Fast Gas Chromatography Method Research Articles

End Column Reverse Chromatography as a Novel Approach for Enhanced Separation: A Pilot Study.

Currently, the most popular technique in gas chromatography (GC) is the "temperature programming", where the temperature increases from the start of the injection. This leads to faster elution of analytes compared to isothermal methods. However, isothermal methods are considered optimal for separating compounds with similar retention times. Another interesting technique that provides higher resolution is the dynamic thermal gradient gas chromatography (TGGC), where separations are achieved as a decreasing thermal gradient. This gradually decreases the positive gas velocity. Nevertheless, it was proven that GC techniques with negative velocity gradients don't improve the resolution of compounds with nearly identical retention times. Optimizing a new GC approach to combine both the short time from positive temperature ramps programming, and the enhanced separation of the negative ramps of the TGGC, a model under the name of "end column reverse chromatography". The process simply consists of two steps, the first is a normal positive ramp from the start of the injection, the second step is a negative thermal ramp at a time that is around the retention time of the first eluting peak. This will decrease the solute velocity almost solely for the second compound leading to relatively enhanced separation. Optimized ECRC method increased the resolution of two isomers (trans and cis chlordane) from 1 (slightly overlapping) in case of temperature programming to 2.78 as shown in this study. This comes in expense of the width and intensity of the peaks, where the intensity decreased about 17% and 12% for cis and trans chlordane, and the peak width increased with 37% and 77% for the same compounds respectively. ECRC is a novel model for enhanced separation that comes with some drawbacks. It can be an alternative approach to get a fast GC method with enhanced separation for isomers.

Fast Chromatographic Method for Explosive Profiling

Security control is becoming a major global issue in strategic locations, such as airports, official buildings, and transit stations. The agencies responsible for public security need powerful and sensitive tools to detect warfare agents and explosives. Volatile signature detection is one of the fastest and easiest ways to achieve this task. However, explosive chemicals have low volatility making their detection challenging. In this research, we developed and evaluated fast chromatographic methods to improve the characterization of volatile signatures from explosives samples. The headspace of explosives was sampled with solid phase micro-extraction fiber (SPME). Following this step, classical gas chromatography (GC) and comprehensive two-dimensional GC (GC×GC) were used for analysis. A fast GC approach allows the elution temperature of each analyte to be decreased, resulting in decreased thermal degradation of sensitive compounds (e.g., nitro explosives). Using fast GC×GC, the limit of detection is further decreased based on the cryo-focusing effect of the modulator. Sampling of explosives and chromatographic separation were optimized, and the methods then applied to commercial explosives samples. Implementation of fast GC methods will be valuable in the future for defense and security forensics applications.

Identification and quantification of acidosis inducing metabolites in cases of alcohols intoxication by GC–MS for emergency toxicology

A simple, cost effective, and fast gas chromatography method with mass spectrometry detection (GC–MS) for simultaneous measurement of formic acid, glycolic acid, methoxyacetic acid, ethoxyacetic acid and 2-hydroxyethoxyacetic acid in serum and urine was developed and validated. This multi-analyte method is highly suitable for clinical and emergency toxicology laboratory diagnostic, allowing identification and quantification of five most common acidosis inducing organic acids present in cases of alcohol intoxication. Furthermore, when patients are admitted to emergency unit at late stage of toxic alcohol intoxication, the concentration of parent compound may be already low or not detectable. This new method employs a relatively less used class of derivatization agents – alkyl chloroformates, allowing the efficient and rapid derivatization of carboxylic acids within seconds. The entire sample preparation procedure is completed within 5min. The optimal conditions of derivatization procedure have been found using chemometric approach (design of experiment). The calibration dependence of the method was proved to be quadratic in the range of 25–3000mgL−1, with adequate accuracy (97.3–108.0%) and precision (<12.8%). The method was successfully applied for identification and quantification of the selected compounds in serum of patients from emergency units.

Simultaneous and cost-effective determination of ethylene glycol and glycolic acid in human serum and urine for emergency toxicology by GC-MS

ObjectivesA simple, cost-effective, and fast gas chromatography method with mass spectrometry detection (GC-MS) for simultaneous measurement of ethylene glycol, 1,2-propylene glycol and glycolic acid was developed and validated for clinical toxicology purposes. Design and methodsSuccessful derivatization of glycolic acid with isobutyl chloroformate was achieved directly in serum/urine while glycols are simultaneously derivatized by phenylboronic acid. The entire sample preparation procedure is completed within 10min. ResultsThe assay was proved to be quadratic in the range of 50 to 5000mgL−1 with adequate accuracy (96.3–105.8%) and precision (CV≤8.9%). ConclusionThe method was successfully applied to quantify the selected compounds in serum of patients from emergency units and the results correlated well with parallel GC-FID measurements (R2 0.9933 for ethylene glycol and 0.9943 for glycolic acid).

Fast determination of ethylene glycol, 1,2-propylene glycol and glycolic acid in blood serum and urine for emergency and clinical toxicology by GC-FID

A simple, cost effective, and fast gas chromatography method with flame ionization detection (GC-FID) for simultaneous measurement of ethylene glycol, 1,2-propylene glycol and glycolic acid was developed and validated for clinical toxicology purposes. This new method employs a relatively less used class of derivatization agents – alkyl chloroformates, allowing the efficient and rapid derivatization of carboxylic acids within seconds while glycols are simultaneously derivatized by phenylboronic acid. The entire sample preparation procedure is completed within 10min. To avoid possible interference from naturally occurring endogenous acids and quantitation errors 3-(4-chlorophenyl) propionic acid was chosen as an internal standard. The significant parameters of the derivatization have been found using chemometric procedures and these parameters were optimized using the face-centered central composite design. The calibration dependence of the method was proved to be quadratic in the range of 50–5000mgmL−1, with adequate accuracy (92.4–108.7%) and precision (9.4%). The method was successfully applied to quantify the selected compounds in serum of patients from emergency units.

A novel fast gas chromatography method for higher time resolution measurements of speciated monoterpenes in air

Abstract. Biogenic emissions supply the largest fraction of non-methane volatile organic compounds (VOC) from the biosphere to the atmospheric boundary layer, and typically comprise a complex mixture of reactive terpenes. Due to this chemical complexity, achieving comprehensive measurements of biogenic VOC (BVOC) in air within a satisfactory time resolution is analytically challenging. To address this, we have developed a novel, fully automated Fast Gas Chromatography (Fast-GC) based technique to provide higher time resolution monitoring of monoterpenes (and selected other C9-C15 terpenes) during plant emission studies and in ambient air. To our knowledge, this is the first study to apply a Fast-GC based separation technique to achieve quantification of terpenes in ambient air. Three chromatography methods have been developed for atmospheric terpene analysis under different sampling scenarios. Each method facilitates chromatographic separation of selected BVOC within a significantly reduced analysis time compared to conventional GC methods, whilst maintaining the ability to quantify individual monoterpene structural isomers. Using this approach, the C9-C15 BVOC composition of single plant emissions may be characterised within a 14.5 min analysis time. Moreover, in-situ quantification of 12 monoterpenes in unpolluted ambient air may be achieved within an 11.7 min chromatographic separation time (increasing to 19.7 min when simultaneous quantification of multiple oxygenated C9-C10 terpenoids is required, and/or when concentrations of anthropogenic VOC are significant). These analysis times potentially allow for a twofold to fivefold increase in measurement frequency compared to conventional GC methods. Here we outline the technical details and analytical capability of this chromatographic approach, and present the first in-situ Fast-GC observations of 6 monoterpenes and the oxygenated BVOC (OBVOC) linalool in ambient air. During this field deployment within a suburban forest ~30 km west of central Tokyo, Japan, the Fast-GC limit of detection with respect to monoterpenes was 4–5 ppt, and the agreement between Fast-GC and PTR-MS derived total monoterpene mixing ratios was consistent with previous GC/PTR-MS comparisons. The measurement uncertainties associated with the Fast-GC quantification of monoterpenes are ≤ 12%, while larger uncertainties (up to ~25%) are associated with the OBVOC and sesquiterpene measurements.

Urine arsenic speciation in clinical toxicology: Usefulness and interpretation

A simple, cost effective, and fast gas chromatography method with flame ionization detection (GC-FID) for simultaneous measurement of ethylene glycol, 1,2-propylene glycol and glycolic acid was developed and validated for clinical toxicology purposes. This new method employs a relatively less used class of derivatization agents – alkyl chloroformates, allowing the efficient and rapid derivatization of carboxylic acids within seconds while glycols are simultaneously derivatized by phenylboronic acid. The entire sample preparation procedure is completed within 10 min. To avoid possible interference from naturally occurring endogenous acids and quantitation errors 3-(4-chlorophenyl) propionic acid was chosen as an internal standard. The significant parameters of the derivatization have been found using chemometric procedures and these parameters were optimized using the face-centered central composite design. The calibration dependence of the method was proved to be quadratic in the range of 50–5000 mg mL−1, with adequate accuracy (92.4–108.7%) and precision (9.4%). The method was successfully applied to quantify the selected compounds in serum of patients from emergency units.

Protocol for the development of automated high-throughput SPME–GC methods for the analysis of volatile and semivolatile constituents in wine samples

Ever since the invention of gas chromatography (GC), numerous efforts within the chromatographic community have been directed toward the development of fast GC methods. However, the developments in high-speed GC technologies have simultaneously created demand for the availability of compatible detection and sample preparation methods, so that the speed of the overall analytical process is increased. Solid phase micro extraction (SPME) is a sample preparation technique developed to address the need for rapid sample preparation. Therefore, the objective of this protocol is to outline recent developments in SPME technology that can be applied toward high-throughput automated qualitative and quantitative analyses of volatile and semivolatile compounds in wine samples. The use of this protocol facilitates routine high-throughput determinations of 200-500 analytes of different physicochemical properties with SPME step requiring only 10-15 min per sample.

Rapid determination of C12–C26 non‐derivatized fatty acids in human serum by fast gas chromatography

The concentration of long-chain fatty acids (LCFAs) in human serum is closely related to human health. It is therefore important to develop a fast, low-cost, efficient method for their determination. In this study, by using fast temperature programming and micro-bore short capillary columns, a fast gas chromatography method was developed for the direct analysis of non-derivatized LCFAs including n-dodecanoic acid to n-hexacosanic acid (C12:0-C26:0, even numbers only), linoleic acid (C18:2), oleic acid (C18:1), and erucic acid (C22:1) within 4.0 min. Method optimization including extraction and separation conditions is considered, and the analysis of real serum samples is presented. The results show that ten LCFAs were well separated with sufficient resolution, and the detection limit was in the range of 2.8-9.6 microg/mL. The reproducibility (RSD) for both intra-day and inter-day determination was always less than 15%, and the recoveries for these LCFAs were from 63.1 to 97.0%.

Fast gas chromatography with luminol chemiluminescence detection for the simultaneous determination of nitrogen dioxide and peroxyacetyl nitrate in the atmosphere

An instrument has been designed and constructed for the simultaneous determination of nitrogen dioxide (NO2) and peroxyacetyl nitrate (PAN) in atmospheric samples. The instrument’s design is based on separation by fast gas chromatography (GC) with a 30 ft capillary column (DB-1) followed by detection by luminol chemiluminescence. The chemiluminescent reaction between NO2 or PAN and luminol takes place at the gas–liquid interface on the surface of a solid support. The chemiluminescent emission at 425 nm is detected with a photon counting module. The instrument is controlled by a 1.8 GHz Notebook computer with a WINDOWS 2000 operating system and a custom software application programmed in LABVIEW. Detection limits are in the low parts per trillion (ppt) with a time resolution of 30 s to 1 min. The instrument was operated during the Mexico City Metropolitan Area/Mexico City Megacity 2003 collaborative air quality study. Results for NO2 from this fast GC method were compared with results from a co-located differential optical absorption spectrometer (DOAS) and a tunable diode laser absorption spectromenter (TDLAS). The results support the application of the new luminol-based instrument for atmospheric measurements.

Measuring residual solvents in pharmaceutical samples using fast gas chromatography techniques

Residual process solvents in pharmaceutical samples are monitored using gas chromatography (GC) with either flame ionization detection (FID) or mass spectrometry. Based on good manufacturing practices, measuring residual solvents is mandatory for the release testing of all active pharmaceutical ingredients and is routinely performed on samples of process intermediates. General GC methods have been developed to monitor solvents routinely used in the drug synthesis process. It is now possible to take advantage of GC equipment with faster temperature ramping capabilities, in combination with shorter capillary GC columns, to achieve a considerable gain in efficiency and a reduction in analysis turnaround time. In this paper, the development and implementation of fast GC methods for residual solvents testing will be discussed. Continued efforts to improve the efficiency of gas chromatography using existing technologies such as, the ThermoOrion Flash GC will also be discussed.

Theoretical and practical aspects of fast gas chromatography and method translation.

Interest in the development and implementation of fast gas chromatography (GC) methods continues to increase. Fast GC method development and validation can be simplified and more successful if a few key theoretical and practical concepts are kept in mind. Key concepts such as speed-optimized flow rate, optimal temperature-program rate, sample capacity, "cut the column", and principles of method translation are discussed.

Fluidized-bed extraction of polycyclic aromatic hydrocarbons from contaminated soil samples

Due to the carcinogenity and ubiquity of polycyclic aromatic hydrocarbons in the environment they are of ongoing interest to analytical chemistry. In this study, a comparison of the classic Soxhlet extraction and, fluidized-bed extraction, has been conducted. The extraction of polycyclic aromatic hydrocarbons by this technique has been optimized considering as experimental variables the variation of the number of extraction cycles and the holding time after reaching the heating temperature by means of a surface response design. The significance of the operational parameters of the fluidized-bed extraction on the performance characteristics has been investigated. For the determination of the analytes a selective clean-up of the extracts followed by a fast gas chromatography method with mass spectrometric detection was used, resulting in low limits of detection (0.2 pg μL -1 ) The accuracy of the complete analytical method was established by extraction and analysis of reference materials.