Application Notes: GC
The Use of Subtle Differences in Selectivity to Improve Separation of Structurally Diverse Analytes
July 2nd 2009The separation of structurally diverse analytes is often complicated by chance coelutions with other analytes or with matrix related compounds. Often the column is blamed, but while such coelutions make analysis difficult they do not necessarily indicate a faulty column, poor chromatography or method design.
Glycerin in Biodiesel by Capillary GC Analysis
June 1st 2009Biodiesel is much in the news today as an alternate fuel source that is safe and nontoxic. It is renewable, via farming and recycling, and is biodegradable. It is cleaner burning than petroleum-based gasolines, with virtually no sulfur and with no net carbon load to the atmosphere.
Can You Use Nitrogen as an Alternate Purge Gas for Analysis of Volatile Organic Compounds (VOCs)?
June 1st 2009Most U.S. Environmental Protection Agency (U.S. EPA) methods for analysis of volatile organic compounds (VOCs) specify purging with helium for 11 min at 40 mL/min, making purge-and-trap (P&T) one of the biggest consumers of helium in a laboratory. Compared to helium, nitrogen is abundant, inert, and can be purchased at affordable prices.
New Innovations for EPA 8260 Analysis
June 1st 2009Over the past 15 years, little has changed for the commercial environmental laboratory's ability to automate U.S. EPA Method 8260 for water and soil purge and trap analysis. As work loads have increased, reporting levels have decreased due to MS sensitivity improvements. However, it has become increasingly difficult for laboratories to run at high levels of productivity due to autosampler reliability, carryover, and internal standard reproducibility challenges. Each of these issues has been addressed in a new Centurion WS autosampler (see Figure 1) designed specifically for the commercial environmental laboratory.
Identifying Drugs of Abuse Using Gas Chromatography-Time of Flight Mass Spectrometry (GC-TOFMS)
June 1st 2009Illegal drug use worldwide is at an all time high. Forensic laboratories are seeing increased sample loads creating an immediate need for fast and accurate analysis to positively identify confiscated materials in criminal investigations. This application highlights the value of gas chromatography with time-of-flight mass spectrometry (GC-TOFMS) for drug testing in forensic laboratories. A method was developed to successfully identify twenty drugs of abuse in 4.5 min. This GC-TOFMS method shows good chromatographic peak shape for even the most challenging drug analytes; even the peak shapes for amphetamine and methamphetamine were exceptional considering they were analyzed underivatized. The total ion chromatogram (TIC) for the twenty drug analytes is shown in Figure 1.
Flexible Fused Silica Capillary: A Discussion of Strength
June 1st 2009Synthetic fused silica capillary tubing is a vital component in many scientific techniques. The general perception is that most laboratory glass products are fragile and easy to break. The opposite is true of fused silica capillary; with its protective coating it is both strong and durable when handled properly.
Case Studies: Improved Productivity with Fast GC Accessories
February 1st 2009Thermal agility is a term that describes the ability of an oven to heat up and cool down. Both steps comprise the complete cycle time which, in turn, determines sample throughput. Fast GC accessories provide an attractive means of increasing sample throughput because they are easy to implement and deliver reliable performance at low cost. They require little or no bench space and do not incur additional costs for consumables and support equipment such as autosamplers, data acquisition software, and computers. Fast oven cooling is especially attractive because methods do not have to be re-validated since the separation parameters remain unchanged.
Analysis of Volatile Organic Compounds in Air by Thermal Desorption
February 1st 2009The Clean Air Act (CAA) (1) provides the U.S. Environmental Protection Agency authority to enforce regulations limiting emissions of volatile organic compounds (VOCs) and other air pollutants. The Compendium of Methods for the Determination of Toxic Compounds in Ambient Air includes a variety of sampling and analysis methods (2, 3), including use of single- and multi-sorbent tubes. Concentrating a large volume of sample onto a sorbent tube, followed by thermal desorption onto a GC column provides an efficient, cost-effective means of monitoring VOCs at parts per billion (ppb) or parts per trillion (ppt) levels.
In-House Generation of Hydrogen for Gas Chromatography
February 1st 2009Hydrogen, commonly used as a carrier gas instead of Helium for gas chromatography (GC) can be supplied via cylinders or by the electrolysis of water using an in-house generator containing metallic electrodes or an ionomeric membrane. An in-house generator can provide a significant increase in safety and convenience with a reduction in operating costs.
GC–MS Screening for Melamine Adulteration in Baby Formula and Dairy Products
December 2nd 2008Melamine is an industrial chemical with a high nitrogen content that can cause kidney stones and lead to renal failure. In some instances, melamine has been added to baby formula and dairy products as a substitute for protein. This paper presents an efficient and definitive gas chromatography–mass spectrometry (GC–MS) method to identify melamine and related compounds based on the released US Food and Drug Administration (FDA) method.
Analysis of PCBs in Food and Biological Samples Using GC-Triple Quadrupole MS–MS
December 2nd 2008This application details a fast, reliable and highly selective trace-level screening method for the quantification of polychlorinated biphenyls (PCBs) in environmental, food and biological samples, using gas chromatography and a triple stage quadrupole mass spectrometer. The analytical strategy is analogous to the well-established US Environmental Protection Agency (USEPA) Method 1668A.
Agilent J&W Ultra Inert GC Columns: A New Tool to Battle Challenging Active Analytes
September 1st 2008QC test probes serve a vital function in ensuring the reproducibility of modern GC columns. These probes ensure that the columns have been properly deactivated, contain the correct amount of stationary phase, and have the same relative retention as the last column purchased. The choice of individual compounds in these test mixes varies widely and can have profound consequences on the performance of a column in the users' applications.
Synthetic Fused Silica Capillary Tubing: A Discussion of Diffusion
September 1st 2008Synthetic fused silica capillary tubing is commonly used as the preferred substrate for chromatographic separation columns. In limited instances the absorption and diffusion of molecules into and through the fused silica deserves consideration.
Performance Gains Using Hydrogen Carrier Gas in Refinery Gas Analysis
September 1st 2008Escalating costs and increasing demands for helium, coupled with diminishing helium supply, have given rise to the investigation and use of hydrogen as an alternate choice of carrier gas for use in gas chromatography (GC) applications. This application note illustrates that the use of hydrogen as a carrier gas as an alternative to helium in refinery gas applications is not only possible, but also results in improved performance and higher sample throughput.
Analysis of Deoxynivalenol in Beer
September 1st 2008Mycotoxins, toxic secondary metabolites of several fungal species, represent food safety issues of high concern. Deoxynivalenol, the most abundant trichothecene mycotoxin, can be found worldwide as a contaminant of wheat, barley, maize and other cereals (1,2). The transmission of deoxynivalenol from barley into beer has been reported in several studies (3,4). Therefore, its levels should be controlled.
Semivolatile Analysis Using an Inertness-Performance-Tested Agilent J&W DB-5ms Ultra Inert Column
September 1st 2008Semivolatile analyses using methods similar to US EPA method 8270 (1) are important in environmental laboratories worldwide. A number of acidic compounds such as benzoic acid or 2,4-dinitrophenol and strong bases such as pyridine or benzidine are active species found in the semivolatile sample set. These highly polar species are particularly susceptible to adsorption into active surfaces in the sample flow path, including the column itself. System and column inertness are critical for effective analysis of these active chemical species.
Real-Time Response to Bacteria Infection of Bioethanol Fermentation Using a Short Rezex™ ROA Column
September 1st 2008Political priorities as well as economic interests have fueled a dramatic growth in the biofuel industry, due much in part to research funding and tax incentives. Currently the world's ethanol production is estimated to be over 16 billion gallons a year. This number is expected to increase in the next few years, reaching an estimated yearly production of 20 billion gallons by 2012. Today, many ethanol producers add fermentors to expand their production capacity. In order to continue using existing HPLC equipment for the increased monitoring, increased analytical throughput is needed.
Flexible Fused Silica Capillary: A Review of Internal Surface Chemistry
June 1st 2008Synthetic fused silica capillary tubing has proven to be a vital component in many separation science techniques. Recently, it has expanded to serve an array of scientific markets. In most cases, an understanding of the internal surface chemistry is of fundamental importance.
Rapid Analysis of Flavors and Fragrances Using High-Efficiency GC Columns
June 1st 2008There are many misconceptions about what it means to perform fast gas chromatography (GC) and what the term fast GC implies. Fast GC is often associated with the use of hydrogen as a carrier gas and, although this is certainly a good approach, it is not always necessary to shorten the analysis time. A second misconception is that changing column dimension results in time-consuming method development. Using high-efficiency GC columns can greatly reduce the analysis time and when coupled with the method translation software, the time spent on method development can be greatly minimized.
Determination of Organic Compounds in Drinking Water Using Atlantic SPE Disks for EPA Method 525.2
June 1st 2008EPA Method 525.2 describes the procedure to determine low ppb levels of semi-volatile organic material in drinking water using solid phase extraction (SPE) or liquid-solid extraction (LSE) techniques. The City of Fort Worth, Water Department implemented an automated SPE process for the analysis of semi-volatiles by EPA Method 525.2, using the Atlantic "Certified for Automation" SPE Disk for EPA Method 525.2. Ethyl acetate, methanol, and water were used to condition the Atlantic disk prior to the extraction step. The extraction solvents used were a 1:1 mixture of methylene chloride and ethyle acetate. Extracts were then analyzed by GC–MS using a splitless injection technique.
Techniques for Reducing Purge-and-Trap Cycle Times in VOC Analysis
June 1st 2008The purge-and-trap (P&T) technique for analysis of volatile organic compounds (VOCs) was pioneered in the 1970s at the United States Environmental Protection Agency (USEPA) research laboratory in Cincinnati. Many of the operational parameters developed during this time period are still included in USEPA methods. While these parameters still produce good analytical results, they do not take advantage of advances in instrumentation that enable analysis of emerging contaminants such as fuel oxygenates, and increased sample throughput.