Columns | Column: Sample Prep Perspectives

This installment examines a sample preparation survey, focusing on sample sizes, laboratory techniques used, automation, the use of solid-phase extraction (SPE) devices (cartridges, disks, plates, tips), SPE chemistries and selection criteria, and problems encountered in SPE.

In this article, the author reports the results from a survey of trends in sample preparation techniques.

An examination of the principles behind “salting out,” and when it can be applied in analytical extractions to enhance the extraction yield.

Here's the scoop on the latest offerings in sample preparation.

On a fundamental level, equilibrium and diffusion define chemical separations. Practical applications of partition coefficients to chromatographic sample preparation illustrate this point.

Continued development of needle-trap extraction (NTE) has expanded its versatility in applications such as disease diagnosis, aerosol-bound analytes, and breath analysis.

Test your knowledge of octanol-water partition coefficients and practical applications of sample preparation.

Can you pass this test of chromatographic sample preparation concepts?

We assess the landscape of new sample preparation instrumentation, supplies, and accessories introduced over the past 12 months.

The QuPPe method expands on QuEChERS to tackle highly polar compounds.

QuEChERS has been updated to suit modern instrumentation. Now also “efficient and robust,” QuEChERSER is a “mega-method” that covers a wider polarity range.

We explore the aspects of sampling that are of highest importance in an analytical scheme. Devices and processes for obtaining appropriate samples outside of the laboratory are presented.

We look at five modern treatments of chromatographic sample extraction, explaining their initial conception and development to shed light on their current roles as analytical tools.

These seven case studies capture and expand on lessons presented at ChromTalks.

We assess the landscape of new sample preparation instrumentation, supplies, and accessories introduced over the past 12 months.

Sorbent-based extractions using metal-organic frameworks (MOFs) have several advantages, notably selectivity. How do these extractions work, and where are they most useful? We look into the current state of the art.

Temperature is frequently employed to enhance analytical extractions, especially with solid samples or volatile analytes. Using temperature to enhance analytical extractions continues today with more recently developed techniques, which we explore.

In electromembrane extraction (EME), the target analyte is extracted from an aqueous sample across a supported liquid membrane (SLM) and analyzed using LC. Through the study presented here, we demonstrate the principles of the technique and test its performance.

Our annual review of the new sample preparation instrumentation products introduced in the past year.

This selection of influential recent papers on chromatographic sample preparation gives us a sense of important developments.

A new technique, ICE concentration linked with extractive stirrer (ICECLES), provides highly efficient isolation of trace compounds from aqueous samples. ICECLES combines freeze concentration with stir-bar sorptive extraction into a seamless analytical extraction methodology.

Proper sample preparation is vital. We look at formal and informal training opportunities to educate chemists in the fundamentals of sample preparation skills.

To better understand modern sample preparation techniques-such as ultrasound-assisted extraction, microwave-assisted extraction, and pressurized solvent extraction-we should look at the lessons these methods took from Soxhlet extraction.

Our annual report of sample preparation instrumentation, supplies, and accessories for gas and liquid chromatography

Bioanalysis with SPME has advanced greatly over the past decade.

Whether or not headspace sampling is quantitative depends on the information gleaned from the analysis

We assess the state of the field, first looking back at developments presented at conferences this year, reader questions, and the passing of a pioneer in solid-phase extraction. Then, we look to the future of sample preparation.

Blanks are important in the pursuits of quality control and robust quantitative analytical methods, but many analysts don’t fully understand their value, or how to use them correctly.

Our yearly report on new products covers sample preparation instrumentation, supplies, and accessories. New sample preparation technologies introduced in the past year, while not necessarily disruptive, take giant leaps in that direction.

A look at recent advances in SPME, such as increasing the sorbent surface area available for extraction, accommodating direct analysis by mass spectrometry, and sorbent overcoating to resist fouling by sugars and lipids

There is a resurgence of interest in chemical derivatization schemes in separation science, particularly in sample preparation. Here’s why.

Incremental sampling methodology laboratory processing is used to produce an appropriately sized subsample that has the analytes of interest at the same concentration as the large incremental sample collected in the field. The end goal is to produce results that represent the conditions at the site and facilitate good decisions.

CAE is a versatile sample preparation tool for aqueous samples.

This yearly report on new products introduced at Pittcon 2017 (or in the preceding year) covers sample preparation instrumentation, supplies, and accessories.

Traditional extraction methods for food samples, such as liquid-liquid extraction and Soxhlet extraction, are often time-consuming and require large amounts of organic solvents. Therefore, one of the objectives of analytical food safety studies currently has been the development of new extraction techniques that can improve the accuracy and precision of analytical results and simplify the analytical procedure.

This installment describes several commonly used microextraction sample preparation techniques and their applications to forensic toxicology analysis. Solid-phase microextraction (SPME), microextraction by packed sorbent (MEPS) and different types of liquid-based microextraction (LPME), including single-drop microextraction (SDME), hollow-fiber supported LPME, three-phase LPME, and dispersive liquid-liquid microextraction (DLLME), are discussed. Examples of application of these techniques to determine illicit drugs and drugs of abuse from various biological specimens are provided as well.

Blood is perhaps the most widely used sample fluid in bioanalysis. Dried blood spots (DBS) have been used with clinical samples for over 50 years but are recently seeing a resurgence of interest. DBS hold several advantages associated with the use of small sample sizes obtained via finger pricks, reduction biohazard, and more. In the previous installment, we gave an overview of microsampling in bioanalysis. This month, we will dig deeper into bioanalysis using DBS.

The rise of microsampling raises questions about representative sampling.

This yearly report on new products introduced at Pittcon or in the preceding year covers sample preparation instruments.

The results obtained from a new survey on sample preparation techniques were compared with the results of previous surveys from 1991 to March 2013. The survey investigated trends in technologies currently being used, sample loads, sample sizes, automation, the use of solid-phase extraction (SPE) devices (cartridges, disks, plates, tips), SPE chemistries, selection criteria, and problems encountered. Respondents were also asked about sample preparation technologies on the horizon.

At the heart of liquid chromatography lies a column. Because of the importance of the column, we have dedicated a regular place to it in LCGC magazine: “Column Watch.” And what has made “Column Watch” so informative over the years is that it has captured the insights of an insider-someone who really understood the workings of the column and its role in separations: Ron Majors.

Cloud-point extraction (CPE) manipulates temperature and surfactant concentration to move aqueous solutes into a micelle phase for separation. Although CPE has been around for some time, it is still considered an emerging technique. Much of the development, and most applications, of CPE have dealt with extraction and preconcentration of inorganic solutes. More recently, attention has turned to the use of CPE in the isolation of organic solutes. This month, we review how CPE works and focus on applications for extracting organics.

A farewell letter from long-time LCGC columnist Ron Majors.

Throughout his career, Ron Majors always had his finger on the pulse of the latest chromatography developments, and he kept readers in the know too.

If sample preparation is the most time and labor intense step in the analytical process, and uses the largest amounts of solvents, it stands to reason that sample preparation may present the most significant safety risks in the analytical lab. While most laboratory workers receive significant safety training, we may become numb to the prospect of accidents or get into the mindset that accidents only happen to other people. Given some recent, significant safety incidents, this month we step back and take a quick refresher on safety concerns appropriate during our sample preparation activities.

Recently, Nature and Science Citation Index listed the 100 most cited research papers of all time. Two of these are the classic Bligh-Dyer and Folch lipid extraction methods from the late 1950s. This month we will take a look at the lasting impact of these papers and explore the current state of lipid extractions, including lipidomics.

When developing analytical methods, several parameters are often considered, things like solvent type and amount, sample size, pH, sorptive phases, temperature, time, and more. While some of these considerations can be considered unimportant in a given situation and experience and chemical knowledge can guide us to appropriate starting points, extraction method development is often a one-parameter-at-a-time proposition. A family of statistical approaches, which fall under the category of response surface methodology, are available to screen and optimize several parameters simultaneously.

As expected, the new products introduced in the past year in the area of chromatographic sample preparation, while somewhat limited, mirror the current development in the field.

When pyrolyzed, macromolecules will decompose into smaller fragments that can have the appropriate volatility for gas chromatography (GC) separation and analysis.

In this installment of "Sample Prep Perspectives," we cover some of the basic scientific principles behind solid-phase extraction (SPE) to allow the correct mode of extraction to be selected through an understanding of how analytes interact with and are separated by the sorbent.

In sample preparation, what does "high-throughput" really mean?

The selective removal of a fat substitute in food products is discussed to demonstrate options for obtaining selectivity during extraction.

A look at five sample preparation methods where the application of a charge across barriers provides enhanced selectivity

Some solid–liquid extraction sorbents that have had significant development recently include MIPs, dSPE for QuEChERS, nanomaterials, and mixed-mode and silicone monolith sorbents.

Some sample preparation techniques that were introduced in the past are now being used for new applications.

The results from a reader survey on sample preparation techniques

Ionic liquids have tunable selectivity for specific classes of analytes, giving them distinct advantages over organic solvents.

Howard G. Barth and Ronald E. Majors Liquid–solid extraction is the most popular method, but sometimes modern approaches such as PLE/ASE and MAE are possible.

By achieving selectivity in other portions of the analytical cycle, we can lower the burden on sample preparation.

An alternative approach to liquid–liquid extraction is explored.

Turbulent flow chromatography is often used for on-line sample cleanup of biological matrices in liquid chromatography–mass spectrometry applications.

The practical aspects of hollow-fiber liquid-phase microextraction in the three-phase mode (HF3LPME) are described.

Combining a membrane with a solid sorbent can improve selectivity and save time in sample preparation.

Miniaturization and solvent substitution are two key approaches.

New methods are available for whole blood analysis. Here, various approaches are compared and contrasted.

An interview with the inventors about the successes, challenges and potential future directions of this technique.

In this installment, the subject of LPME is reviewed, with emphasis on the use of hollow fibers.

The inventors of the QuEChERS technique present an update and a look at the future.

How the combination of an electroextraction with hollow-fiber liquid-phase microextraction can lead to a selective, rapid new method.

Ron Majors discusses the technique of Salting-out Liquid-Liquid Extraction (SALLE) and provides some examples of its successful applications.

The guest columnists review SBSE and HSSE and examine their advantages and limitations, along with providing approaches to overcoming the latter.

Columnist Ron Majors discusses some of the practical considerations in the successful application of the popular yet age-old technique of solvent extraction (also known as liquid–liquid extraction, or LLE). After a brief review of the basics, guidelines on the selection of the appropriate extraction solvents and how to use acid–base equilibria to ensure efficient extractions of ionic and ionizable compounds are provided. Problems in LLE and the solutions to these problems are highlighted. A newer technique called dispersive liquid–liquid microextraction (DLLME) is introduced.

Guest authors from South Africa review the application of membranes in the extraction, preconcentration, and separation of various contaminants in food.

Columnist Ron Majors discusses some of the practical considerations in the successful application of the popular yet age-old technique of solvent extraction (also known as liquid–liquid extraction, or LLE).

This installment of SPP will compare and contrast the various types of polymeric and non-polymeric sorbents. The major advantages or polymeric sorbents will be discussed, and some applications will illustrate the versatility of polymeric SPE.

The authors discuss a preparative process using the principles of countercurrent chromatography. This process is faster, capable of loadings from milligrams to hundreds of grams, and uses robust equipment.

Selective sample preparation techniques are particularly attractive for the analysis of trace amounts of small molecules in complex matrices. In this month's instalment, columnist Ron Majors covers the field of immunoextraction, a technique that employs immobilized antibodies to selectively capture specific analytes using molecular recognition via antibody–antigen interactions. Recently, the introduction of commercial products for specific high-volume environmental and food safety applications should spur further applications of this technique.

In this month?s installment, columnist Ron Majors covers the field of immunoextraction, a technique that employs immobilized antibodies to selectively capture specific analytes using molecular recognition via antibody?antigen interactions. Recently, the introduction of commercial products for specific high-volume environmental and food safety applications has spurred further applications of this technique.

This month's instalment of "Sample Prep Perspectives" describes a new extraction technique called QuEChERS (standing for quick, easy, cheap, effective and safe and is pronounced "catchers") for the sample preparation of pesticides in foods and agricultural samples. The technique uses simple glassware, a minimal amount of organic solvent and various salt/buffer additives to partition analytes into an organic phase for clean up by dispersive solid-phase extraction (d-SPE). The technique provides good recoveries, is reproducible and costs less than other sample preparation approaches. The technique is being adopted by many laboratories worldwide. It has the potential for applications outside of the pesticide in foods area.

In this instalment of "Sample Preparation Perspectives", columnist Ron Majors discusses advanced topics such as multimodal SPE, restricted-access media, molecular imprinted polymers, immunoaffinity extraction phases and other class-or compound-specific sorbents...

This month's installment of "Sample Prep Perspectives" describes a new extraction technique called QuEChERS (standing for quick, easy, cheap, effective, and safe and is pronounced "catchers") for the sample preparation of pesticides in foods and agricultural samples.

This installment of "Sample Prep Perspectives" discusses techniques for the reduction/depletion of high-abundance proteins.

Traditional methods for the sample preparation of insoluble solid materials have represented one of the more time consuming and labour-intensive efforts in analysis. In this instalment of "Sample Prep Perspectives", Ron Majors examines modern sample preparation methods for solids that often involve increased temperature and higher pressure to speed up the extraction process. In addition, modern sample preparation methods have been automated to relieve analysts of the drudgery associated with traditional methods. Here, he reports on automated Soxhlet extraction, supercritical fluid extraction, pressurized fluid extraction–accelerated solvent extraction, and microwave-assisted extraction and updates earlier coverage.

Although the majority of solid-phase extraction (SPE) is performed with conventional bonded silica- and polymeric-phases, difficult and complex samples may require more specialized stationary phases. In this installment of "Sample Prep Perspectives," columnist Ron Majors discusses advanced topics such as multimodal SPE, restricted-access media, molecular imprinted polymers, immunoaffinity extraction phases, and other class- or compound-specific sorbents. These phases provide additional selectivity, and procedures using them can be automated. Representative applications will be presented.

Capillary extraction (CEx) is used to study the solventless in-tube extraction of naphthalene, acenaphthene, phenanthrene, fluoranthene, chrysene, benzo(a)pyrene and coronene in aqueous samples prepared by analyte spiking into clean waters or, as an alternative, by using the generator–column method of sample preparation. Analysis of laden extractors is conveniently performed by high-resolution gas chromatography (GC), with a flameionization detector (FID). Extraction set-ups and main extraction variables are investigated from a practical point of view. For 2- to 4-ring polycyclic aromatic hydrocarbons (PAHs), equilibrium times are within a few minutes, analytical sensitivity is in the parts-per-billion (ppb) range and reproducibility is better than 10% relative standard deviation (RSD) (n = 6). Coronene behaviour is unique and presumably determined by extreme hydrophobicity and thus very negligible aqueous solubility: in-tube extraction of coronene seems possible only if starting from oversaturated..

Guest authors Luke Chimuka and Ewa Cukrowska provide an in-depth look at the verious approaches to passive sampling, weighing the merits and challenges for each type.

Liquid–liquid extraction (LLE) is among the most widely used sample preparation methods. In this month's instalment of "Sample Preparation Perspectives," Ron Majors discusses newer LLE approaches that offer significant advantages over classic methods. The miniaturization of LLE has resulted in solvent and time savings, improved automation possibilities and faster sample preparation. The techniques of single-drop microextraction, extraction in levitated droplets, flow injection-, membrane-based- and solid-supported extractions are reviewed. Often, these techniques use the same immiscible solvent pairs of conventional LLE.

The two most popular mechanical techniques for sample preparation for large-scale protein production are concussion and liquid shear.

The authors review the latest technologies in MPT sample preparation used in study of genomics, proteomics, and metabolomics.

This month's guest authors review the application of solid-phase microextraction (SPME) to the analysis of drugs in human plasma discussing important factors in the optimization of extraction efficiency. The column concludes with a discussion of method validation issues.

This month's column reviews some key considerations in the manufacture and use of microplates with particular reference to the 96-well plate.

A new sampling method for gas chromatography termed single-drop microextraction (SDME) is described. In this column, SDME is applied to residual solvent analysis, both in manual and automated modes.

A novel device for coupling on-line in-tube SPME with capillary GC is presented by the guest authors and the method's application demonstrated for the analysis of contaminants in water.

Extracting analytes from biological tissues often presents serious challenges for the analytical chemist. In this column, the guest authors provide an overview of human and animal tissue sample preparation, and compare conventional extraction technologies with novel approaches to these challenges.

New miniaturized liquid-membrane extraction designs are especially suited for speciation studies of metal ions in small amounts of biological fluids.

Highly selective sorbents for solid-phase extraction (SPE) are desirable tools for the development of selective and sensitive methods for trace analysis. Molecular imprinting is an emerging technique that can yield analyte- or group-selective polymeric sorbents.

Ron Majors describes solid-phase extraction devices that provide new levels of convenience, improved performance.

This installment of "Sample Prep Perspectives" discusses microdialysis sampling and the opportunities and challenges it presents. The guest authors look at microdialysis theory and equipment and describe potential applications...

Norberto Guzman and Ron Majors look at three areas in which progress has been made in improving concentration limits of detection for CE and CE microchip techniques: preconcentration methods, detector enhancements, and derivatization methods to improve separation selectivity and to enhance detection.

Guest author Reg Cross discusses strategies for collecting samples from large masses of material. He also describes the problems associated with acquiring truly representative samples for analysis.

Current sample preparation procedures for LC–MS as applied to samples from biological matrices.

To accommodate high-throughput analysis, analysts are using 96-well plates, as well as some unfamiliar accessory products. This column describes these products and tells readers how to use them in their laboratories.