Electromembrane Extraction with Vials of Conducting Polymer

A Discussion about SEC, NAIEC, and Py-GC-MS

Industrious Innovations in Polymer Analysis

Recovering from a COVID-19 Shutdown

Three-Dimensional Thinking 

EAS Award for Outstanding Achievements in the Fields of Analytical Chemistry

This year, Susan Olesik from The Ohio State University is the EAS Awardee for Outstanding Achievements in the Fields of Analytical Chemistry. Best known for her chromatography as well as mass spectroscopy expertise, Dr. Olesik will present a plenary lecture entitled "The Fascinating Impact of Nanoscale Structure on Chromatography and Mass Spectral Ionization”. The Field's Session for her award includes a group of separation scientist leaders, including University of Buffalo’s Luis Colón, University of Waterloo’s Janusz Pawliszyn, Lisa Holland from West Virginia University, and Jared Anderson from Iowa State University. Their talks will bring novel and innovative chromatographic and sample preparation technology presentations to the program at EAS.

Invited Talks: Green Chemistry, Forensics, Cannabis, Bioanalysis, Biologics, Pharmaceutical Analysis, and More

Invited speaker sessions are the strength of EAS; this year will be no exception. In two green chemistry sessions sponsored by the Chromatography Forum of the Delaware Valley, advances in sustainability using liquid and supercritical fluid chromatography along with the robust application of gas chromatography will be discussed. From reaction monitoring of pharmaceutical processes, the use of enhanced fluidity as a more sustainable solvent through the evaluation of alternative solvents in sample preparation followed by comments on volatile organic compound (VOC) emission testing, to embracing sustainable freshness and looking at more efficient gas chromatography processes, the direction is toward greener chromatographic systems. Additionally, invited presentations by experts on the challenges of cannabis testing, handwriting and drug analysis in the field of forensic science, bioanalysis of sensitive and accurate biologic therapeutics and biomarker analysis, life cycle management of analytical methods, pharmaceutical forensics for safe manufacturing, and supply and counterfeit screening will contribute to the separation science scope of EAS.

New Technical Powerhouse Sessions on Hot Topics with Live Audience Virtual Roundtables

Of special note are the new invited technical powerhouse sessions, where leaders on the current hot topics of technical and industrial interest will speak, and then attendees will have the opportunity to engage in virtual round table discussions with the experts, as well as fellow conferees. The hot separation topics in 2020 are “Impurities in the Pharmaceutical Industry” and “Analytical Challenges and Opportunities in Drug Product Development”.

Contributed sessions will touch on a wide variety of applications used in the chromatographic world. Included are dozens of papers in sessions on tradition and innovation in bioanalytical and pharmaceutical analysis, as well as method development, instrumentation, and pharmaceutical applications in modern chromatography.

In the EAS Separation Science Award Session, 2020 awardee Joe Foley from Drexel University will tell us whether two columns are better than one via a discussion on the hydrophobic subtraction model. Included in this session are a presentation by Isiah Warner of Louisiana State University (“Materials Approach to Separation Science”), as well as discussions led by Andre Striegel from NIST (“Determination of Polymer Molar Masses when Using Mixed Solvents”) and 

“Capillary Columns Versus Traditional Packed Beds for Biomolecular Analysis”). 

Presentations Available November 16 through December 31

The advantage of being virtual in 2020 is that all presentations are available from November 16 through December 31, 2020 for your viewing pleasure. Please join EAS on November 16th, and experience the latest developments in the field of separations.

Mary Ellen P. McNally is a Global R&D Fellow at the Stine Haskell Research Center of FMC Corporation, in Newark, Delaware.

Articles

The 2020 Eastern Analytical Symposium has gone virtual for 2020, and although we will miss the camaraderie of face to face interaction, the theme of this year’s conference “Analytical Science: Cornerstone of Innovation” indicates the strength of the separation sciences and the talks that you will not want to miss. 

Chromatography Advances at EAS 2020

Tony Taylor is Group Technical Director of Crawford Scientific Group and CHROMacademy. His background is in pharmaceutical R&D and polymer chemistry, but he has spent the past 20 years in training and consulting, working with Crawford Scientific Group clients to ensure they attain the very best analytical science possible. He has trained and consulted with thousands of analytical chemists globally and is passionate about professional development in separation science, developing CHROMacademy as a means to provide high-quality online education to analytical chemists. His current research interests include HPLC column selectivity codification, advanced automated sample preparation, and LCâMS and GCâMS for materials characterization, especially in the field of extractables and leachables analysis.

I have many conversations with colleagues and customers who want to ”keep analyte extraction simple,” to “make sure the extraction method is rapid and robust,” to ”ensure the extraction method is cost-effective, as we have so many samples to process.” All very noble aims.

Except, these same people will tell me that limits of detection aren’t looking great, specificity isn’t too good, there are some coelution issues, or that they are having problems with matrix effects in LC-MS. I refer you to the learned gentleman above, and add that to achieve quick, cheap, and good all at once takes a lot of work in development. Oh, I nearly forgot: that’s the other thing that I hear a lot these days, ”we don’t have a lot of time to get this method up and running!” Exasperation.

All this being said, depending upon your analytical goals, there are some techniques, which when properly optimized, can achieve that holy grail of inexpensive, quick, and selective. But in order to efficiently develop these methods, one needs to know the premise on which they work and how to quickly optimize them. We begin this short series by describing the principles and optimization of perhaps the most straightforward of all the extraction techniques, liquid-liquid extraction (LLE).

No matter which ”version” of liquid-liquid extraction method you wish to use, there are some fundamentals that apply, and perhaps principle among these is analyte physicochemical information. It can be shown that, for neutral molecules, the partition coefficient between water and an organic solvent is directly related to the analyte hydrogen bond acidity, hydrogen bond basicity, dipolarity, polarizability, and molar volume (2). For ionizable species, at least one further descriptor related to the properties of the ionic form is required. It is, however, my experience that predictive relationships of this kind are rarely used in practice, and a trial and error approach using various solvent combinations is typically undertaken.

Understanding analyte physico-chemical parameters

To achieve the best selectivity and recovery, one needs to ensure that partitioning of target analytes from one phase into the other is as efficient as possible, and this is underpinned in most cases by some simple physicochemical information. The following information is recommended;

Number of hydrogen bond donors or acceptors (

Specific volume (inverse of density) (m3/Kg) (

 
For example, this data for the molecule Cathinone, which is an ionogenic substance as shown in Figure 1:   

This information is available from a variety of sources and we have made extensive use of the following;

 (ChemAxon) (which also calculates values for analytes not in the previous databases) (

So how can use this information to design and optimize our LLE experiment. The first choice in designing any liquid extraction is the choice of extracting solvent, and this choice is driven by the relative hydrophobicity of the analyte molecule, which is reflected by its LogP(D) value.

As a brief reminder, the partitioning behaviour of an analyte between two phases will be reflected in LogP values as follows:

As can be seen from Table I, the analyte Log P value will indicate the degree of success that is likely in extracting an analyte from an aqueous matrix.

It is obvious from the Cathinone physico-chemical data that the LogP(D) value will vary according to the pH of the sample solution, and we can use this information to our advantage when designing LLE experiments. For our Cathinone example, by adjusting the aqueous pH to a higher value, the analyte will be in the neutral form and therefore will be to the left of the equilibrium and the analyte LogD value (as the analyte is ionizable we used LogD rather than LogP but the general relationships hold) will be 1.18 and will partition 10:1 into the organic phase, depending upon the organic solvent chosen.

The relationship between solution pH and pK is shown below as a reminder for the target pH values:

For our target Cathinone analyte, adjusting the sample solution pH to 9.55 or above, will ensure the analyte is in the neutral form, the LogD value will be 1.18, and therefore will be more successfully extracted from the aqueous sample into an organic solvent. This should demonstrate the importance of knowing the analyte physicochemical properties in designing your extraction experiment. If the sample solution had been at neutral or acidic pH the partition coefficient for the analyte would have been much lower and recovery from the sample solution into the extracting solvent would be accordingly very much lower.

If one is unsure of analyte pKa or even exact analyte structure, it is always best practice to assess the effect of pH on solvent extraction efficiency with the following pH conditions suggested;

pH 6 and 7.5 for suspected neutral analytes

The difference in analyte recovery between each of the pH value pairs can sometimes be quite startling and these differences are driven by the (unknown) analyte pKa.

The selectivity of the extraction experiment involving pH manipulation can be further improved using a technique known as back extraction. Once the target analytes are in the organic phase, they can be re-extracted into a fresh aqueous phase whose pH has been manipulated to ensure the analytes are in the charged form and therefore most highly hydrophilic. For acidic target analytes, the second aqueous extracting solution is manipulated to basic pH and vice versa for basic analytes. In this way, specificity of the extraction can be improved as all neutral extractants will be left behind in the organic solvent, reducing the instances of co-elution, and achieving lower matrix background (and hence lower detection limits). There are no limits to the number of back extraction steps that can be employed to improve specificity and hence the aqueous layer pH may again be adjusted to ensure the analyte is in the neutral form and extracted into a further organic solvent. Of course, absolute analyte concentration will decrease in each back-extraction stage according to the specific recovery achieved at each stage.

Recovery of more highly hydrophilic analytes from aqueous samples can be promoted through the use of salt addition to the sample. There are two common approaches:

Use of an ion-pairing salt with opposite charge to the analyte, which, if the sample solution pH is adjusted to ensure the analyte is fully ionized, will pair with the analyte to form a neutral complex. This neutral complex is likely to have a much higher partition co-efficient than the ionized analyte, and recovery into the organic extracting solution will be increased. When analytes are strongly acidic or basic, this tends to be the method of choice.

Adding high-enough concentrations of simple salts to saturate the aqueous sample solution can increase the partition coefficient of hydrophilic analytes and improve recovery into organic extraction solvents. Effectively the analyte solubility in the aqueous sample is reduced by adding, for example, 3–5 M sodium sulphate to the sample solution, driving the target analytes into the organic phase and improving recovery. There are a variety of salts that can be used in this way, and the required concentrations to achieve saturation, or optimum analyte recovery, need to be empirically determined.

Of course, the partitioning behavior of our target analytes is strongly influenced by the choice of organic solvent into which we chose to extract our analyte, as the various solvents will also have a range of polarities that will influence their affinity for the analyte(s). For reference, some water-immiscible solvents are shown below with their polarity index values.

For more polar analytes, and here lower values of LogP(D) can also act as a good indicator of polarity, one may need to select an organic solvent that has a higher polarity index value in order to optimize recovery of the analyte from the aqueous sample into the organic extracting solvent. The rules are fairly simple: try to match the polarity of your analyte with the polarity of the extraction solvent. If you cannot obtain a good polarity measure of the analyte (see later discussion for some useful tools to help with this), LogP(D) can be used as a surrogate, with lower LogP values indicating the need for a more polar extraction solvent and vice versa.

Of course, it is also possible to used ”mixed” organic systems as the extraction solvent to further fine-tune the selectivity or the recovery of the target analytes from the sample. Here one needs to develop an in-house screening approach, using solvent mixtures that have proven to be successful in your application area. To assist with this, a list of the solvent systems I have found particularly useful in the past is shown below in Table III. We typically use 96 well plates to screen these solvent mixtures, as this provides a rapid way of assessing the gross partitioning behaviors of a relatively large number of analytes, several solvents, and perhaps different pH or (as we shall see later), and salt strengths and still leaves enough wells for blanks, recovery standards, and so on.

Of course, the most effective solvent combination in terms of recovery will depend upon the nature of the analyte and interferent species that we wish to leave behind, and some trial and error is likely.

Advanced methods for extraction solvent selection

I recently came across a fascinating paper in which the group had investigated building a predictive algorithm for extraction efficiency based on quantitative relationships between the LogP(D) values of model compounds in a variety of solvent pairs. (2) It strikes me that this would be a very logical and useful approach where one is working in a specific application area. A suitable set of model compounds can be identified. This group used pKa, Log D, number of hydrogen bond donor (HBD) groups, and the analyte specific volume to calculate the analyte partition coefficient in a variety of organic solvents from an equation derived from only a few basic partition co-efficient measurements. 

There are other online tools that can help to inform the optimum choice of solvent for liquid-liquid extraction and perhaps the most useful of these is the UFZ-LSER database (3). Using the SMILES string for our cathinone molecule, it was possible to calculate some key thermodynamic and physico-chemical properties of the molecule that are then used to predict the partition coefficients between a wide variety or organic solvents (solvent mixtures) and water. This is a very useful tool to quickly identify the organic solvents to use in any screening experiments and, in this particular example, it was identified that chloroform is a good candidate for the liquid extraction of Cathinone. While the results from this database are less reliable when the analyte properties need to be calculated, it does contain a vast array of compounds with known values, and will also search the internet for reliable sources of the descriptors, again improving the reliability of the partition coefficient estimations.

A further cautionary note when selecting the extraction solvent is that one always needs to be mindful of which layer is the extraction solvent, bearing in mind that certain organic solvents are more dense than water and will therefore be the lower layer in the extraction vessel. Common examples of these solvents include (in order of increasing density):

Chlorobenzene < Ethylene Dichloride < o-Dichlorobenzene < Methylene Chloride < Trichloroethylene < Chloroform < Carbon Tetrachloride

When considering solvent selection, one must always be mindful of the specificity of the extraction, and here I specifically refer to the ability of technique to separate the target analytes from matrix components which may have similar chemical and physico-chemical properties. Where simple binary solvent systems are used for liquid-liquid extraction, the control of specificity can be restricted to the choice of the organic solvent, the sample solution pH, and perhaps the ionic strength. In terms of organic solvent selection, one important selectivity consideration is that of the water solubility in the organic solvent, and this can be particularly important when one is carrying out trace analysis. The relative solubility of water in a range of organic solvents is shown in Table IV:

From Table IV, it should be obvious that some organic solvents are able to solubilize a reasonable amount of water and therefore can be expected to be less specific than those solvents in which water has much lower solubility. Using solvents that can more readily solubilize water will give rise to extracts which contain higher levels of interferents which, as is pointed out above, may be a particularly important considering when performing trace analysis. A very useful lookup resource for these water solubilities can be found at the following link: 

To ensure the highest recovery possible, the ratio of organic extraction solvent to aqueous sample should be high (or perhaps higher than is generally accepted as reasonable), and a ratio of 7:1 is considered somewhat of a generic optimum value. Obviously, the actual optimum value will depend upon the partition coefficient of the target analyte(s) between the two solvents, and extraction solvents with high partition coefficients may require lower ratios and vice versa. Interestingly, the database of Reference 4 has a nice tool (“Extraction Tool”) which allows the optimum solvent/sample ratio to be estimated, which can save a great deal of empirical optimization. The optimum value for the Chloroform extraction of Cathinone as described above was found to be 6:1 organic to aqueous using this tool, indicating that our generic 7:1 ratio for optimum recovery may indeed be a reasonable guide.

Volatility of extraction solvent and analyte

The volatility of the extracting solvent is a further important consideration that goes alongside the selection of the optimum organic : aqueous ratio, primarily as the speed of sample preparation will usually be rate limited by the speed with which the organic solvent volume may be reduced, using evaporation to achieve a sample concentration that meets analytical limits of detection. More volatile extraction solvents may give rise to more rapid evaporation protocol steps and therefore reduce the overall extraction experiment time, but it should be stated that if one can avoid a solvent evaporation step, then this is much preferred. Solvent evaporation steps can introduce unwanted qualitative and quantitative error into the determination, and the careful choice of solvents with high affinity for the target analytes may allow lower solvent volumes to be used and may, perhaps, avoid the need for solvent evaporation.

A further, often-overlooked consideration is that of analyte volatility. An ideal solvent should be capable of evaporation-to-dryness in a reasonably short time (10–15 min) under nitrogen when heated to 30– 40 oC. If the analyte can withstand these conditions without loss or degradation, then recovery will be high. Of course, the more volatile the analyte under these conditions, then the lower the recovery of the extraction experiment. If recovery is low due to analyte volatility, one must consider an alternative extraction solvent that will evaporate under less harsh conditions.

Mixing (agitation) mode and extraction time

The facile process of extraction requires that the surface area interface between the two phases is maximized, which will often involve the mixture being agitated with reasonable vigor. In the modern laboratory, manual shake flasks have been (or should be!) replaced with smaller vessels that can be mixed on an orbital mixer or by using automation systems. Yet one still needs to optimize the vigor with which the sample is mixed, in order to achieve maximum analyte recovery in a reasonable timeframe. Of course, the time of extraction will also need to be optmized, and this will be predicated by the mode of mixing, affinity (partition coefficient) of the extracting solution for the analyte, and the ratio of sample-to-extraction solvent. One might consider then that there are enough variables here to perform an optimization of the extraction using Design of Experiments (DoE) approaches, and this indeed is a highly effective way to achieve the ultimate extraction recovery.

In summary then, there are many more considerations when designing a simple liquid-liquid extraction experiment than one might realize. However, to avoid ”getting nothing for something,” and to drive towards fast, inexpensive, and selective LLE protocols, one really does need to put in a lot of method development effort. There are very few shortcuts, but hopefully the discussion above and the resources highlighted will assist you in this work.

Of course ”standard” liquid-liquid extraction is only one version of the liquid extraction technique. There are many variants available, including:

Solid supported liquid-liquid extraction (SSLE / SLLE)

Membrane assisted solvent extraction (MASE)

Hollow fibre liquid phase microextraction (HF-LPME)

Next time I will consider the principles of some of these techniques as well as their optimization.

"The Untold Story of Napoleon Hill, the Greatest Self-Help Scammer of All Time"

S. Tshepelevitsh, K. Hernits, J Jenčo, J.M. Hawkins, K. Muteki, P. Solich, and I. Leito, 

N. Ulrich, S. Endo, T.N. Brown, N. Watanabe, G. Bronner, M.H. Abraham, K.-U Goss, UFZ-LSER database v 3.2.1 [Internet], Leipzig, Germany, Helmholtz Centre for Environmental Research-UFZ. 2017 [accessed on 12.07.2020]. Available from 

Tony Taylor is the Chief Scientific Officer of Arch Sciences Group and the Technical Director of CHROMacademy. His background is in pharmaceutical R&D and polymer chemistry, but he has spent the past 20 years in training and consulting, working with Crawford Scientific Group clients to ensure they attain the very best analytical science possible. He has trained and consulted with thousands of analytical chemists globally and is passionate about professional development in separation science, developing CHROMacademy as a means to provide high-quality online education to analytical chemists. His current research interests include HPLC column selectivity codification, advanced automated sample preparation, and LC–MS and GC–MS for materials characterization, especially in the field of extractables and leachables analysis.

Oliver Napoleon Hill (1883– 1970) was an American self-help author once described as ”the most famous conman you’ve probably never heard of” (1 ). Conman maybe, but there is a quote of his that I believe to be particularly true when considering sample preparation for chromatography techniques; ”The one who tries to get something for nothing generally winds up getting nothing for something.”

The LCGC Blog: Inexpensive, Quick, and Selective: Seeking the Holy Grail of Sample Extraction

In this panel of veterninary drugs from a milk sample, SPE displays an improved solution over traditional protein precipitation methods and other types of SPE, due to clean up efficiency, all while maintaining a rapid and fast analysis time.

Utilizing a Rapid, Two-Step Method for the Clean-Up of Veterinary Drugs in Milk Using Strata®-X PRO Solid Phase Extraction (SPE)

http://www.chromatographyonline.com/lcgc_w/dioxin_analysis


	The EU-China-Safe* project is a jointly funded EU/Chinese project that aims to deliver a shared vision for food safety and authenticity based on “mutual recognition” in food standards, testing and certification. Partners in China and Europe identified that validating GC–MS/MS methods for dioxins analysis is as an economic option to build value for money testing capacity. As part of the EU-China-Safe project, Fera Science Limited (Fera) performed analysis of PCDDs, PCDFs, and dl-PCBs in food using a preconfigured Thermo Scientific TSQ 9000 triple quadrupole GC–MS/MS system equipped with the new Advanced Electron Ionization (AEI) source. An important aspect of the collaboration was the development of an EU-China Joint Laboratory Network, which conducted a study using shared data systems to enable cooperative development of a method to demonstrate equivalency with traditional HRMS. Study results obtained from proficiency test (PT) and quality control (QC) samples were within the expected concentration ranges. These findings demonstrate that the limit of quantification (LOQ) complied to one-fifth maximum levels, and that the analytical method demonstrated the sensitivity, selectivity, and robustness required to satisfy current EU regulations 644/2017 and 771/2017. 

	In this webcast, we will provide an overview of how methods are being developed by the EU-China-Safe project and focus on the particular benefits of the TSQ 9000 and AEI technology for dioxin analysis.

		Overview of the EU-China-Safe project and how methods are being developed within the project

		Discover a fully-validated dioxin analyzer with pre-loaded acquisition, calculation and reporting templates to simplify user training and increase productivity soon after installation

		Learn how this analytical solution is easily implemented into laboratories and able to meet EU performance criteria 

		Understand how GC–MS/MS with enhanced sensitivity enables users to lower sample weight to reduce both the cost of sample preparation and system maintenance

*EU-China-Safe project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 727864 and from the Chinese Ministry of Science and Technology (MOST).

The content of this webinar does not reflect the official opinion of the European Commission and/or the Chinese government. Responsibility for the information and views expressed therein lies entirely with the author(s).

Sean Panton, Analytical Chemist, Food Safety and Quality, Fera Science Limited

	Aaron Lamb, Senior Mass Spectrometry Applications Specialist, Thermo Fisher Scientific

 Thursday, Sept. 3, 2020 at 11am EDT | 8am PDT | 4pm BST | 5pm CEST

	On demand available after final airing until  Sept. 3, 2021

Learn how to simplify the complexity of dioxin analysis using a fully integrated workflow based on GC–triple quadrupole analysis. This Dioxin Analyzer not only takes advantage of the new GC–MS/MS technical advancements, but significantly improves the ease of use and accelerates
the implementation in routine laboratories.

Live: Thursday, Sept. 3, 2020 at 11am EDT | 8am PDT | 4pm BST | 5pm CEST

On demand available after final airing until Sept. 3, 2021

Register free

The EU-China-Safe Project: The Assessment of a Dioxin Analytical Workflow in Food and Feed

 and the American Chemical Society Analytical Division Subdivision on Chromatography and Separations Chemistry.

As one would expect of any technology, each passing year shows some incremental advantage in chromatography.The realization of these advantages comes through an incredible amount of carefully thought-out and conscientious effort. Some areas where we consistently see incremental improvement in chromatography are

and otherwise, the democratization of our field.

We are now at a time, however, when our focus should no longer concern itself with the incremental, and instead focus on a big idea that will alter the course of chromatography forever. This big idea is, without a doubt, miniaturization.

The trend toward miniaturization is visible in many areas of the wider world.Items such as our wristwatches and cellular phones take up newly developed technology, allowing them to be trimmed down without sacrificing qualities consumers have come to expect, and subsequently demand. Chromatography systems, accessories, and workflows are all following suit; this has taken some years to build, but is now advancing rapidly. Large and small companies have joined in this effort. While common themes are evolving, there is no shortage of different approaches to solving the multitude of problems created, as well as opportunities afforded by, miniaturization.

To miniaturize chromatography, the engineering and fabrication feats are tremendous. For instance, as sample pathways, tubing, and systems narrow and shrink, so do the design tolerances. To address this challenge, many companies are returning or keeping manufacturing in their home countries: Instruments are built by hand in high-end facilities by qualified engineers—a job that is typically shopped out to overseas partners for the majority of contemporary chromatographic instruments.

Another big obstacle is the bureaucratic administration of large agencies, such as the Food and Drug Administration (FDA) and Environmental Protection Agency (EPA), governing the most productive analytical laboratories. These organizations are, by nature, cautious, and often seemingly resistant to “course correction.” Novel instruments are less likely to serve these controlled environments, which boast the highest density of instrumentation—thus slowing innovation.

All the obstacles in the world, however, cannot stop innovation, but merely slow its inevitable march. Some advantages are so evident and incredible that they overcome even the most vigorous resistance. One such advantage of miniaturized chromatography—as simple as it is powerful—is that as systems reach a tenable size for overnight shipment, the need for a traditional and cumbersome service network naturally falls away—because if you need instrument repair, you can quickly receive a stand-in instrument to use while you send out your broken unit for repair, without needing to have a service engineer visit your site. This change has the potential to halve the cost of running instrumentation in the field.

Another game-changing advantage of miniaturization is that smaller channels and sample pathways dramatically decrease the need for gasses, solvents, and power requirements. This feature further allows a more portable or mobile paradigm to evolve, while lowering costs and waste.

Current Examples of Chromatography Miniaturization

While there isn’t enough space here to go through all the fantastic attempts to miniaturize chromatography instruments, I would like to highlight a couple of my favorite approaches for your consideration. First, I need to state that my opinion in no way reflects on my employer, this publication, nor any group to which I belong.

A favorite of mine is the approach being taken by Axcend, which offers the most portable gradient liquid chromatography (LC) system the world has yet seen. Their instrument’s toolless design, rechargeable battery, and light weight make it compatible with almost any field application.

Another excellent offering in this field is the miniaturized gas chromatography (GC) instrument made by Lucidity. This elegant solution to an overcrowded benchtop sits on roughly a third of the space used by a traditional kit while not sacrificing any meaningful performance. Set up and run, and swap columns and consumables like a pro, from your first day. They don’t lock you into any consumables and offer the best of consumer-driven business practices that you have come to expect from other areas of life.

The best of our companies operate by standing in their customers’ shoes, solving problems as if they were their own. Innovation rooted in holistic long-term problem-solving that lovingly draws from the learnings of the previous step inspires enthusiasm for advancement from the greater community—one in which I am thrilled to be taking my part.

began his career as an analytical chemist in the pharmaceutical industry. Inspired by his long-standing love of science and natural ease with sales and marketing, he is currently working to seek strategic business solutions in the chromatography field. Currently, he works for Restek and volunteers his time to a wide variety of nonprofit organizations within the chromatography community. Edelman serves as the treasurer of the ACS SCSC, in addition to serving as Chair of the Organizing Committee for the ISCC/ GCxGC 2021 conference, Executive Committee Person at the Chromatography Forum of Delaware Valley, 

 of the Washington Chromatography Forum, and founder and president of the Separation Community Mixer.

 and the American Chemical Society Analytical DivisionSubdivision for Chromatography and Separations Chemistry (ACS AD SCSC). The goals of the subdivision include:

promoting chromatography and separations chemistry

organizing and sponsoring symposia on topics of interest to separations chemists

developing activities to promote the growth of separations science

increasing the professional status and the contacts between separations scientists.

In any given community, on rare occasions, leaders converge on a big idea. The development of such an idea alters the course of the community, in a way that is meaningful if it is lasting. It is my belief that the collective chromatography community is currently converging on a big idea.

The LCGC Blog: Miniaturized Chromatography—The Next Big Idea

Click the title above to open the LCGC Asia Pacific August/September 2020 regular issue, Vol 23, No 3, in an interactive PDF format.

LCGC Asia Pacific-09-08-2020

is pleased to announce the addition of Nicholas Snow to its editorial advisory board (EAB). Earlier this year, Snow became the editor of the “GC Connections” column in 

Snow is the Founding Endowed Professor of Chemistry and Biochemistry and an Adjunct Professor of Medical Science at Seton Hall University in South Orange, New Jersey. He has served the university in many capacities over the years, including as chair of the Department of Chemistry and Biochemistry, chair pro tem of the College of Arts and Sciences Faculty, vice chair of the Faculty Senate, faculty chair of the 2004 Decennial Middle States re-accreditation, and associate provost for Finance and Administration. He holds a BS from the University of Virginia and a PhD from Virginia Tech.

His research group works broadly in separation science with a special interest in developing and understanding sample preparation and how the sample preparation techniques impact overall chromatographic methods.

In 26 years at Seton Hall, Snow has published more than 70 research articles and book chapters and mentored 20 PhD students along with numerous MS students and undergraduates. He has been recognized twice by Seton Hall’s Board of Regents for outstanding teaching and service to students.

LCGC is pleased to announce the addition of Nicholas Snow to its editorial advisory board (EAB).

Nicholas Snow Joins LCGC’s Editorial Advisory Board

The method uses a new magnetic solid-phase extraction (SPE) technique, followed by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Nitrogen-doped reduced graphene oxide-iron oxide (Fe

) nanocomposite, used as the adsorbent of organophosphorus pesticides, was successfully prepared using an easy hydrolysis process. The nanocomposite was synthesized and characterized by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The effects of type and ratio of eluents, amount of the graphene oxide (GO)/Fe

 nanocomposite, pH, ionic strength, equilibrium time, and ultrasound time on the quantitative recoveries of fenitrothion, chlorpyrifos-methyl, and chlorpyrifos were investigated. On the basis of the best condition, the recoveries of the target analytes in real water samples were between 84.40% and 105.05%. The relative standard deviations varied from 1.21% to 4.22%. Finally, the method was successfully applied to the determination of three organophosphorus pesticides in real environmental water samples.

Organophosphorus pesticides (OPPs) have been widely used for preventing or decreasing damage caused by pests, weeds, and plant disease, and are very important for high-yield production in agriculture (1,2). However, as a result of extensive use, these OPPs enter the environmental water system by various sources, and, as a result, both human and animal populations are exposed to OPPs through drinking water. The most harmful outcome, however, may be the formation of mutagenic compounds during conventional oxidation processes (3). Therefore, it is necessary to develop an effective method for monitoring OPPs in real environmental water, which is useful for ensuring environmental and health safety.

The determination of OPPs has been carried out with a variety of techniques, such as gas chromatography with a flame photometric detector (GC‑FPD) (4,5), liquid chromatography–mass spectrometry (LC-MS) (6), gas chromatography–mass spectrometry (GC-MS) (7), and gas chromatography with nitrogen–phosphorus detector (GC-NPD) (8). Even though most OPPs are analyzed by GC, high performance liquid chromatography (HPLC) is preferred to GC for analysis of OPPs because of the thermal lability of these compounds. In addition, HPLC is one of the most sensitive and selective analytical methods for the determination of organic pollutants in environmental water.

However, there are challenges in using HPLC for such analyses, because OPPs in environmental water samples, such as tap water, underground water, farmland water, lake water, and river water, are often present at low concentrations, and these matrices are considered to be very complex. Therefore, for HPLC analysis of OPPs in environmental water samples, an appropriate sample preparation technique is required to isolate and enrich the target analytes (9–11). To address this challenge, various sample preparation methods for analysis of OPPs have been researched, such as liquid–liquid extraction (LLE) (12), ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) (13), liquid–liquid microextraction based on solidification of floating organic droplets (DLLME‑SFO) (14), and other traditional sample pretreatment methods.

In recent years, there has been much interest in the study of the magnetic materials, such as iron oxide (

) nanoparticles, which have been widely used for enrichment of organic pollutants in water, owing to various advantages, including their stability, good separation characteristics, availability, and avoidance of secondary contamination of samples (15–19). However, 

 nanoparticles, have a tendency to agglomerate into larger particles because of the magnetic tendencies of this compound (20–24). The most effective technique is to load Fe3O4 onto supporting materials, such as activated carbon or graphene. There are many researchers who load 

 onto graphene to analyze organic contaminants in water (21,25,26). However, in recent studies, the structure of the activated carbon was changed after treatment by strong oxidation (18,27). In another study, therefore, a new magnetic material, a nitrogen-doped reduced graphene oxide-Fe3O4 nanocomposite (N-RGO/Fe

, was synthesized using an easy method. N-RGO/

 has high adsorption capacity and strong catalytic ability for removing OPPs at low concentrations from environmental water, and the N-RGO incorporated with magnetic 

 nanoparticles is able to effectively overcome the challenge of the separation of adsorbent from aqueous solution (28).

 has long been used for electrochemical super capacitors and electrochemical catalysis (29–32). The aim of the present study, therefore, is to establish a new method of magnetic solid-phase extraction (MSPE) for enriching and separating OPPs in water samples. This is the first time that the novel N-RGO/

 has been used as a solid-phase extraction agent for the enrichment of OPPs including fenitrothion, chlorpyrifos methyl, and chlorpyrifos in real water samples. This separation process can be performed directly in crude samples containing suspended solid materials without the need for filtration or additional centrifugation, which makes separation faster and easier. Furthermore, the recoveries of OPPs and reusability of the N-RGO/

were also evaluated. This method using sample pretreatment with MSPE followed by HPLC analysis offers several advantages, including good precision and recoveries, low cost, and good reproducibility. Given these advantages, this new method may be broadly useful in many other fields.

Fenitrothion (purity >98%), chlorpyrifos methyl (purity >98%), chlorpyrifos (purity >98%), GO (purity >98%, layers <3), FeSO

O were obtained from Aladdin Ltd. The reagents used for the elution, including methanol, ethanol, acetone, acetonitrile, and ethyl acetate, were purchased from Taixin Ltd. Deionized water was provided using a laboratory system. All chemicals were used as received, without further purification. A stock solution containing fenitrothion, chlorpyrifos methyl, and chlorpyrifos at 100, 430, and 500 mg/L concentration, respectively, was prepared in methanol, and stored at 4 °C.

An LC-20AT series HPLC system equipped with a solvent delivery pump, an SPD-20A UV-vis detector (Shimadzu), and an LC solution workstation were used for the analyses. An HY-5 mechanical shaker (Jintan Etong Electric Corp.) was used in this work. An SZ-2 system (Shanghai Lu West Analytical Instruments) was used to prepare double deionized water. A high-speed centrifuge was employed to centrifuge the sample solutions (Model 800).

The N-RGO was prepared by adding 260 mg graphene oxide (GO), 100 mL water, and 4 mL aqueous ammonia into a 250 mL round-bottom flask, and then heating at 180 °C for 24 h, followed by adding 5.2 mL of NH

O with sonication for 7 min to thoroughly mix the solution. Finally, 8 mL of 0.35 g/mL freshly prepared FeSO

O was added to the solution, and heated in a water bath at 85 °C for 6 h to form N-RGO/Fe

After being cooled to room temperature, negative‑pressure filtration was used, and then N-RGO/Fe

 solids were washed with deionized water to neutralize them. Finally, N-RGO/Fe

 solids were placed in an oven to dry, and the dry solids were placed in storage for the next phase of the experiment.

The HPLC separation was performed on a C18 column (150 mm × 4.6 mm, 5-µm, Beijing Jingkerida Technology Co., Ltd.) with equivalent elution using methanol and water at a rate of 1 mL/min and detection at 285 nm. The composition of equivalent elution was 85% methanol and water (0.1% acetic acid). The injection volume was 20 µL, and the column temperature was 35 °C.

 into 150 mL water to which was added 0.075 mL fenitrothion, 0.015 mL chlorpyrifos methyl, and 0.015ml chlorpyrifos, with a concentration of 5.0 mg/L for each analyte. The mixture was sonicated for 1 min to disperse the graphene, and then the conical flask was shaken on the platform of an orbital incubator for 30 min for adsorption equilibrium. Subsequently, an external magnet was placed on the bottom of the tube. After the solid phase was aggregated, the water phase was discarded. Simultaneously, the collected sorbents adsorbing the target analytes were eluted with 0.5 mL methanol and 0.5 mL ethyl acetate to desorb the analytes, which was sonicated for 5 min. Separation of solid and liquid phases was the same as above. The eluted solution was collected, then dried under a stream of nitrogen at 55 °C, and dissolved with 1 mL methanol. Finally, after filtration through 0.22 µm membrane, 20 μL of the solution was analyzed by HPLC.

 was synthesized and characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS).

FT-IR was used to identify the presence of functional groups and chemical bonds in material. Figure 1 shows the FT-IR spectra of N-RGO/Fe

 is assigned to the Fe-O bonds stretching of the magnetite, and the intense band at 3440 cm

 is attributed to stretching of the amino group, which can provide the evidence to demonstrate that amino group were successfully grafted onto the surface of the RGO/Fe

 during preparation. The band at 1635 and 1128 cm

 could be assigned to the aromatic skeleton C=C and C-C stretching vibration of the autoxidized graphitic domains and stretching vibrations of the epoxy, further confirming the above results.

XRD is a common technology to determine the crystal structure of the superparamagnetic nanoparticles. The XRD pattern of the N-RGO/Fe

 is depicted in Figure 2. It shows diffraction peaks at 2θ = 18.10°, 30.13°, 35.69°, 36.36°, 43.04°, 53.51°, 57.07°, and 62.64°, which correspond to crystal indexes of (220), (311), (400), (222), (422), (511), and (440), respectively (JCPDS no. 19–0629) (30,33). For N-RGO/Fe

, the disappearance of the diffraction peaks corresponding to GO (24.6°) and N-RGO (43.1°) is attributed to inhibition of the restacking of graphene layers by the crystal growth of Fe

, leading to decreasing integrity of graphene oxide crystal structure (28).

XPS was employed to further investigate the chemical composition of N-RGO/Fe

. As shown in Figure 3a, the XPS wide scan spectra of N-RGO/Fe

 clearly exhibited that the magnetic material mainly consisted of Fe, C, N, and O. Figure 3a also shows that the observation of Fe 2p3/2 and Fe 2p1/2 signals at 711 and 725 eV arose from the magnetic Fe

 core of prepared material, and from Figure 3a, and binding energy of N 1s was about 400 eV, which was attributed to the amino group. Thus, the presence of the peak for N 1s suggested the formation of amino group on surface of Fe

. Figures 3b and 3c show the high-resolution XPS of C 1s and O 1s. As can be seen from C 1s, the appearance of peaks at the binding energies of 284.7, 286.4, and 288.8 eV were corresponding to C-C in aromatic rings, C-OH, and C=O, respectively, which confirmed that RGO was successfully immobilized on N-Fe

 by acylation reaction. For O 1s, the typical peak at 530.3 and 531.8 eV were corresponding to O-H and C=O, respectively, which suggest there were different oxygen-containing groups. Thus, these indicated the successful preparation of N-RGO/Fe

In the present study, a 150 mL sample to which was added 0.075 mL fenitrothion, 0.015 mL chlorpyrifos methyl, and 0.015 mL chlorpyrifos for each analyte, was used to study the extraction performance of OPPs under different experimental conditions. During optimization, the experiments were analyzed them at least in duplicate.

In this study, four elution solvents, including methanol, acetone, acetonitrile, and ethyl acetate, were used. Methanol has a better elution effect on chlorpyrifos and chlorpyrifos methyl than acetone, acetonitrile, or ethyl acetate. However, in addition to ethyl acetate, other elution solvents have little elution capacity for fenitrothion. This may be accounted for by their better solvation capabilities for the target analytes. Based on the above considerations, a mixed solvent of methanol and ethyl acetate was selected as the elution solvent.

The rate of the elution solvent was also an important factor affecting the extraction and recoveries efficiency. To achieve good extraction and recoveries for the target analytes, different ratios of methanol and ethyl acetate (for example, V

 acetate=5:1; 3:1; 1:1; 1:3; and 1:5, respectively) were compared at these studies. As shown in Figure 4a, the results showed that the extraction recovery of fenitrothion was affected by the ratio of methanol to ethyl acetate, and when the ratio of methanol and ethyl acetate was 1:1, the recoveries of fenitrothion and chlorpyrifos methyl were highest. However, the greatest recovery of chlorpyrifos appeared at 1:3. This may be owing to the strong polarity of ethyl acetate for chlorpyrifos. Considering that the change of extraction recovery of chlorpyrifos and chlorpyrifos methyl with the ratios of methanol and ethyl acetate is less obvious than fenitrothion, V

 acetate=1:1 was selected as the optimum rate for the following experiments, at a total volume equal to 1 mL.

To improve the enrichment efficiency of the extraction method, the amount of N-RGO/Fe

 was investigated, from 10 to 50 mg. As shown in Figure 4b, when the amount of N-RGO/Fe

 added was 30 mg, the recovery reached peak; this result was due to the stronger adsorption capability of the N-RGO/Fe

. The peak areas of the three tested analytes slightly decreased when the amount of N-RGO/Fe

 was increased from 30 to 50 mg. There is one reason which can explain this phenomenon: A very high amount of adsorbent requires high amounts of desorbing solvent to elute the analytes, so the peak areas of test analytes are reduced. Therefore, an optimal sorbent amount of 30 mg was selected for further experiments.

To examine the effect of the sample solution pH, the pH was studied ranging from 3.0 to 11.0, which was adjusted by using CH3COOH and NH3·H2O solution. From the results, as shown in Figure 4c, it was found that the recoveries of OPPs increased when increasing the pH of the sample solution from 3.0 to 6.0. This is due to the electrostatic interactions that the three tested OPPs exhibit on the surface of the N-RGO/Fe

. At pH <6.0, both the analyte and the adsorbent surfaces are positively charged, and the electrostatic repulsion between two positive charges is a robust force. Further increases in solution pH were also examined, and it was found that the peak areas of the OPPs decreased when the pH was above 6.0. This result was attributed to the fact that more oxygen-containing groups on the N-RGO/Fe

 surfaces are ionized when the pH is above 6.0, which causes lower extraction of analyte materials. To sum up, a pH of 6.0 was selected for follow-up experiments.

To investigate the effect of ionic strength on the adsorption percentage of OPPs on N-RGO/Fe

, the ionic strength was set over the range of 0–11% (adding NaCl of 0, 4.5, 7.5, 11.5, and 14.5 g), and the results are shown in Figure 4d. As can be seen, the recoveries rose rapidly with the increasing NaCl concentration at the beginning, due to the salting out effect and the higher viscosity, which may make the process of extraction between the target analytes and adsorbents more effective. Meanwhile, previous studies suggested that an excessive amount of NaCl may reduce the extraction kinetics. Thus, the optimal salt addition was determined to be 5%.

Adsorption equilibrium time is an important factor for evaluating the adsorption capacity of the materials, because MSPE is a partition equilibrium process of analytes between adsorbents materials and sample solution. To screen out the optimum conditions, the effect of extraction time from 10 to 50 min were explored. As shown in Figure 4e, the maximum recoveries were obtained when the extraction time was 30 min for the three analytes. Thus, 30 min was selected as optimum adsorption equilibrium time for the further experiments.

Ultrasound time is the minimum time needed for quantitative desorption of the analytes, which is another essential factor that affects the recoveries of the analytes. As shown in Figure 4f, for screening out optimum ultrasound time, 3–11 min was set for experiments. For fenitrothion, 3 min was enough to get desorption, while 5 min was needed for chlorpyrifos and chlorpyrifos methyl. In terms of total recovery for the three OPPs, 5 min was selected as the optimal ultrasound time.

To validate the developed HPLC method for the analysis of OPPs, the linearity was evaluated using a series of standard mixture solutions of the analytes. Concentrations from 0.020 to 800 μg/mL were obtained for the establishment of the calibration curve. For each level, five repetitive measurements were carried out. Relative standard deviations (RSDs), enrichment factors (EFs), and limits of detection (LODs) were examined to evaluate the HPLC method.

The recovery percentage (RSD) was calculated by following equation 1 (34):

 are the final concentration of the analyte in the spiked sample and in the unspiked sample, respectively.

The enrichment factor was calculated with equation 2 (34):

 are the final concentration of the analyte in the organic phase (extraction solvent) and the initial concentration of the analyte in the aqueous phase, respectively.

The results are shown in Table 1. Three OPPs exhibited good linearity with correlation coefficients (

) between 0.9993 and 0.9997, and the RSDs varied from 1.58% to 2.90%. The LODs of 0.04–0.06 μg/mL for the analytes were obtained based on the ratio of signal-to-noise (S/N = 3), with the RSDs (

 = 5) lower than 3.58%. Finally, EFs were in the range of 133 to 166, which demonstrates that the HPLC method has high values and good extraction performance. Above all, it can be concluded that good sensitivity and reproducibility could be achieved with the developed HPLC method.

 was applied to determine three OPPs, including fenitrothion, chlorpyrifos, and chlorpyrifos methyl residues in environmental samples under the above optimum conditions established. No OPPs were found in the real samples; the recovery was carried out by spiking known concentrations of mixed standard OPPs into the samples before adding the N-RGO/Fe

. For each concentration level, three replicate experiments with the whole analysis process were performed. The results are listed in Table 2, and show that this method has good extraction efficiency for analyzing of three OPPs in real water samples. The recoveries of the studied OPPs were between 84.40% and 105.05%. Figure 5 shows the typical chromatograms of tap water and lake water.

In this study, a method based on MSPE-HPLC with N-RGO/Fe

 as the adsorbent was proposed for analyzing three organophosphorus pesticides—fenitrothion, chlorpyrifos, and chlorpyrifos methyl—in environmental water. A rapid separation of organophosphorus pesticides was achieved. The developed method provided fast analysis process, high EFs, low LODs, wide linear range, and good anti-interference ability. This method fully embodies the high speed and efficiency of HPLC. It is suitable for the speciation of OPPs in environmental studies.

We thank the Fundamental Research Funds for the Central Universities (XDJK2018C043).

S. Hassani, S. Momtaz, F. Vakhshiteh, A.S. Maghsoudi, M.R. Ganjali, P. Norouzi, and M. Abdollahi, 

M.I. Badawy, M.Y. Ghaly, and T.A. Gad-Allah, 

E. Zhao, W. Zhao, L. Han, S. Jiang, and Z. Zhou, 

F. Tian, W. Liu, H. Fang, M. An, and S. Duan, 

F.K. Wan, S.A. Ong, L.N. Ho, Y.S. Wong, C.H. Voon, S.Y. Yusuf, N.A. Yusoff, and S.L. Lee, 

J.C. Wei, J. Hu, J. Cao, J.B. Wan, C. He, Y.J. Hu, H. Hu, and P. Li, 

In this study, a method was developed for extraction and preconcentration of trace amounts of organophosphorus pesticides (OPPs), including fenitrothion, chlorpyrifos-methyl, and chlorpyrifos in environmental water. 