Many samples ion analytical chemistry consist of trace components in a complex and interfering matrix. Identification and quantification of these components often requires the use of sample pretreatment. Moreover, preconcentration is often necessary in order to meet the required detection limits. The introduction of large sample volumes is an attractive means of improving the detection limits in capillary gas chromatography. In comparison with conventional pre-concentration techniques, large volume sampling is generally more time and cost effective.

The introduction of liquid samples in gas chromatography has been a problem ever since the introduction of this technique into routine laboratories. Especially in capillary gas chromatography extraordinary demands are placed on the sample introduction device. An extremely small sample amount has to be introduced accurately and rapidly in a reproducible manner into the smallest possible gas volume. This gas plug must be transferred into the column without any losses by degradation, adsorption or discrimination. It is evident that this can only be achieved by employing very sophisticated inlet devices. For routine analysis of liquid samples four injection techniques are available: split, splitless, on-column and programmed temperature vaporising injection.

Chromatographic separations are based upon differences in the physical and chemical properties of the various components. The difference in the partition coefficients of the individual sample components give them different retention times. If a coefficient is very high, then the component has a very long retention time.

Selecting the appropriate chromatographic technique for a given separation problem is a challenging task for analytical chemists. The answer to the question whether a given problem should be tackled by gas chromatography, liquid chromatography, supercritical – fluid chromatography or one of the newer electrophoretic methods depends on numerous parameters. In general however, one could say that if capillary GC can be used, it should be preferred over any of the other techniques. Capillary GC offers a resolving power, separation speed and a user-friendliness unsurpassed by the other chromatographic methods. In this respect high temperature capillary gas chromatography is an interesting new development as it opens possibilities for the analysis of components that in the past could only be analysed using liquid chromatography or packed- or open-tubular supercritical-fluid chromatography.

In the past, thermal desorbers have been both complex and costly. This has stemmed from an assumption that the only way to achieve satisfactory peak shapes is to perform the transfer of the analytes from the air sample to the column in several stages, transferring the organic components into successively smaller volumes of gas, until the gas volume matched the input bandwidth required by the column. While generally effective, this approach suffers from a number of disadvantages, which in the main, arise from the complexity of the process employed.

The determination of mineral oils in water is of major importance in the environmental analysis. Mineral oils are present in water as well as in soil. In areas near gasoline stations, for example, the soil is often very contaminated with mineral oils. Concern for the environment is getting more and more important. Natural processes are being disrupted so that the quality of life is being threatened. Modern laboratories get more and more requests for the determinations of organic pollutants in water. The required detection limits seem to get lower and lower. Large volume injection can aid to meet these requirements.

Comparison of Silanized glass wool; quartz wool; Tenax TA (35-60 mesh); Dexil-300 (12% on Chromasorb 750 80- 100 mesh); PTFE; and polyimide wool for sample volume, inertness and thermostability. Deactivation with bis- (trimethylsilyl)amine and polymethylhydrosiloxane.

In this short contribution the various methods for PTV-based large volume sampling will de discussed. The basic principles of the methods are described and guidelines for the selection of the PTV injector and the sampling method that is to be preferred for a given (large volume sampling) application are discussed. Examples of PTV large volume sampling experiments will be given. Special emphasis will be on the optimization of the experimental conditions in PTV-based large volume sampling.

A method was developed for measurement of the low levels of cotinine in saliva resulting from ETS exposure. This involved the use of capillary GC-MSD system fitted with an OPTIC injector. The Optic enabled large volume injections to be made and, therefore, low detection limits to be achieved, whilst the MSD allowed selective detection and reliable identification of the cotinine. This is important, as there are other nitrogen-containing compounds present in saliva at a similar retention time.

Solid–phase extraction is a powerful technique for the clean-up and trace enrichment of samples before GC or GCMS.  Unfortunately, up until recently, its use with GC was strictly limited to off-line mode, since no standard instrumentation for hyphenated SPE-GC was commercially available. This note presents a fully automated STE-GC system. The PROSPEKT for automated SPE is interfaced to the GC using the OPTIC 2 injector for large volume injection.

Current methods for the analysis of mineral oils in water employ a Freon extraction combined with infrared spectrophotometry. Freons and other suitable solvents (such as Tetrachloromethane) are damaging to the environment and covered by the terms of the Montreal Protocol. As a consequence, there is an urgent need for an alternative method of performing the analysis.

The ATAS 8270 Injector System has been developed to automate the rapid injection of large volumes of sample extract utilising the OPTIC 2 Injector. The ability to routinely inject larger volumes of solvent results in significantsavings in the sample preparation laboratory. It is estimated that 65% of all costs associated with semi-volatile sample analysis result from sample preparation and concentration. By significantly increasing GC/MS sensitivity, sample volumes can be greatly reduced. Initial sample volumes can be reduced from 1000 mL to 50 mL or less. Corresponding decreases in solvent usage are also realised. Soil samples can be extracted and analysed without further concentration steps. Volatile surrogate recoveries show dramatic improvement.

The preparation of the methyl esters of fatty acids for analysis by gas chromatography is the commonest chemical reaction performed by lipid analysts. Although it is a relatively simple operation, it is still a time consuming process. Automated preparation, extraction and injection of the methyl esters of fatty acids for gas chromatographic analysis is now possible using the FOCUS Sample Processing Robot in conjunction with GC-FID.

Most multidimensional systems are difficult to set-up, require specialist equipment and technical experience and have high running costs. For example, heart cutting transfers selected groups of peaks from the outlet of a first column to the inlet of a second, hence sacrificing the first, which requires frequent replacement. Using Optic as an alternative to multidimensional chromatography is cost effective, simplifies the technique of selectively introducing components into the column and protects the column and detector. The Optic 2 was used on a gas chromatograph to produce a model for the analysis of volatile trace components in highly concentrated samples. This was achieved by the positive use of discrimination against the less volatile major component. Discrimination is a result of injection technique or temperature, the column phase, etc. has no impact on the transfer or exclusion of components, as the effects are achieved in the liner. Here, the difference in the volatilities of the trace and major components is used to specifically exclude the less volatile major component, hence removing up to 98% of it from the system, thereby improving the sensitivity for the analysis of the trace analyte through the ability to use highly concentrated samples and the detector sensitivity, as only a fraction of the sample is detected.

Following on from the ATAS Chromatography Technical Notes No here is a short procedure of how to estimate the injector isothermal temperature and time and optimise these conditions to selectively discriminate between two compounds in the liner.

Temperature programmable injectors with packed widebore (ca. 3.5 mm i.d.) liners are used for large volume injection in capillary gas chromatography with the aim to simplify and/or improve off-line sample pre-treatment procedures. A simple procedure for optimization of large volume PTV injection is described. The system performance, i.e. linearity and repeatability, is evaluated for polar nitrogen/phosphorous containing pesticides (PTVGC- NPD) and organochlorine pesticides (PTV-GC-ECD) in river water extracts as well as for PAHs in river sediment (PTV-GC-MS).

In-situ field measurements of isoprene, methacrolein, methyl vinyl ketone and selected monterpenes have been taken in a Portugese eucalyptus forest. Samples were collected on to a sorbent trap, and analysis was performed on site using a programmed temperature vaporization injector to produce a rapid desorption of analytes from sorbent trap on to a wide bore GC column. Using the method no intermediate cryofocusing step is required, eliminating the need for cryogenic coolants. The high flow rate of helium over the sorbent trap during the GC analysis rapidly reconditions the trap, which is ready to be reused at the end of the analytical programme. Using a single sorbent trap ambient biogenic compound concentrations from the forest canopy were monitored every 70 minutes, over a 5 day period.

Simple procedures for the determination of C1-C7 hydrocarbons in air are described. C2-C7 hydrocarbons are collected on a carbon molecular sieve trap and desorbed directly into a porous layer open-tubular column by means of a programmed temperature injector. Methane is determined by direct injection.

Thermal sample treatment hyphenated with gas chromatography is a versatile and powerful tool in analytical chemistry. Techniques such as thermal desorption combined with GC and pyrolysis-GC are widely used for the analysis of samples that cannot be introduced directly into the GC. In this contribution a PTV injector is used both as a thermal desorption unit and as a pyrolysis device. In commercially available instruments these tow techniques are always separated. An injector with relatively large internal volume was used because this allows weighing the samples directly into the liner of the injector. Only minor adaptions to existing PTV injectors are required. The results obtained with the new method indicate the interesting potentials of the technique as an analytical tool. The absence of a heated transfer line and switching valves, which are generally present in conventional set-ups, eliminates the risk of losses of high molecular weight components. The advantages of combining thermal desorption and pyrolysis sequentially inside a PTV injector includes the flexible temperature possibilities and the ease of calibration and quantitation. As an application the system is used for analysis of geological samples for geochemical purposes. The samples under investigation are geological coal samples. The system gives important information about origin, maturity as well as quality and quantity of oil in a source rock.

The hyphenation of thermal sample treatment techniques such as thermal desorption and pyrolysis with gas chromatography gives a versatile and powerful tool in the study of polymers. An inexpensive system where thermal treatment at different temperatures occurs inside a PTV injector is described. The samples investigated, commercial plastics, are complex mixtures that contain several polymers and additives. These plastics as well as their pure constituents are subjected to multi-step thermal treatment. The individual chromatograms of the various constituents of the polymeric sample are correlated with those of the final material in order to identify additives (thermal desorption) and degradation products (pyrolysis). Results obtained with the new method indicate the interesting potentials of the technique for the characterization of polymer compositions. The absence of a heated transfer line and switching valves, which are often present in conventional set-ups, eliminates the risk of losses of high molecular weight components. Further advantages of the technique proposed are the simplicity and versatility as well as its inexpensive nature.

Set-up of the Mirror air sampling system for analyzing ambient air.

The use of programmed-temperature vaporizing injector for large-volume injection in capillary GC is briefly reviewed. The principles and optimization of large-volume PTV injection are discussed. Guidelines are given for selection of the PTV conditions and injection mode for specific applications. Relevant examples from the recent scientific literature serve as illustrations.

The pulsed discharge helium ionization detector (HID) has been shown to have many advantages over the widely used flame ionization detector (FID) when coupled to GC. These include the ability to detect all volatile organic compounds as well as exhibiting improved response to the hydrocarbons. The advantages that the HID offers are being employed in a number of applications in the field of atmospheric chemistry. This work is using the HID to facilitate the monitoring of ambient formaldehyde and other oxygenated hydrocarbons by a GC method and as a detector for and airborne instrument monitoring hydrocarbons in the upper troposphere.

Rapid large volume injection using an Optic programmable injector has been widely used in recent years, when analysing a large variety of trace compounds. This combines the advantages of the ability to inject greater than 100 times more sample, therefore reducing the amount of sample preparation, as well as its use as a method of hyphenation and automation. There are, however a couple of disadvantages when using the RLVI packed liner. Decomposition of some analytes may occur due to the catalytic effects of the liner packing, whereas some analytes adsorb to the packing and are too strongly retained. The disadvantages with the conventional large volume oncolumn injection method, is that a long pre-column is necessary and the auto-sampler injection speed must be strictly controlled. The new large volume at-column concentrating technique has been devised to overcome these problems.

The on-line automatic Solid Phase Extraction and the capillary GC/MS were combined for the determination of pesticides and herbicides in the aqueous samples. The at-column concentrating large volume injection technique, which the authors exploited, was employed as the interface between SPE and GC/MS. In the at-column concentrating large volume injection method, the sample solvent was evaporated in the empty liner and the target compounds were retained at the inlet of the analytical GC capillary column. Employing this method, heat labile target compounds were not decomposed. Automatic on-line operation was possible, since the large volume of the liquid sample could be transferred to the capillary GC/MS system.

In the present research project, two hyphenated GC methods for monitoring industrial wastewater streams were developed. The first method is used for the element-specific analysis of environmental pollutants and is based on large-volume injection using a PTV. The second method uses on-column large-volume injection on a pre-column, where the solvent-vapour formed during and after sample injection is vented through a solvent-vapour-exit, placed between the pre-column and the analytical column. This method is applied for the analysis of oligostyrenes in wastewater streams.

The American Society for Testing and Materials has established guidelines for simulated distillation analyses, which include samples that have boiling points in the range of about –44 °F to 1139 °F. These include ASTM Method D2887 and Method D3710. A new high temperature simulated distillation method is under development that extends the boiling range distribution to final boiling point temperatures upwards of 1300 °F to 1380 °F. Data provided from HTSD analysis is currently being utilized to provide valuable information to refiners of heavy crude oils. This information helps improve gas oil yields and minimize vacuum tower residues. The method is precise enough that it can also be used to determine if a crude oil has been adulterated, e.g. by blending pitch into the crude.

In order to make accurate measurements of atmospheric hydrocarbons such as the trace levels observed in the clean marine environment, the employment of numerous GC methods have been suggested. So called grab samples provide a very convenient method of acquiring such a sample and dismisses the need to transport what has always been considered as typical laboratory equipment. However the atmosphere is a constantly reacting body and any ‘total air sample’ will subsequently include the reactive species. A method has recently been developed to facilitate in-situ measurements of atmospheric hydrocarbons. Such an instrument has been deployed at Mace Head on the west coast of Ireland, a clean marine location frequently used for atmospheric studies. The concentrations monitored at such a site are at such a level as to necessitate manual analysis due to the constraints of currently available software. This work presents the application of a digital signal processing unit (DSP) to a trace level instrument and illustrates the advantages of such a coupling.

Sampling systems for GC have recently received much attention. New techniques, such as SPME and LVI have made the routine analysis of ultra trace impurities in water at the sub-ppb level possible. The capillary GC analysis of compounds from an aqueous matrix generally requires that the compounds be extracted into a suitable solvent before analysis. In SPME, the fibre coating serves as solvent, whereas, in LVI, an appropriate volatile organic solvent is used. Thus SPME can be directly compared with LVI that employs LLE prior to injection. Due to its small volume, the SPME fiber forces the method to include a significant concentration of the analyte as it transfers from the aqueous matrix to the fiber. This pre-concentration may not occur in LVI-based methods. Several scenarios for SPME and pre-LVI extractions will be compared for maximum recovery, based on calculations from partition theory and from experimental data. Based upon the above comparisons, and from data on column and detector capabilities available in the literature, it will be possible to theoretically compare ideal detection limits and linear ranges for the two methods. These theoretical calculations will be compared to experimental data for a test mixture of PAHs. Considerations in the practical operation of the two techniques will also be discussed.

Atmospheric non-methane hydrocarbons (NMHC) and dimethyl sulphide (DMS) have been monitored at a remote coastal location using adsorption sampling techniques with analysis by in-situ GC as part of the ACSOE OXICOA 1996 campaign. Concentrations varied considerably during the campaign but can be consistently interpreted by consideration of the relevant back trajectory of the monitored air mass. Isoprene is confirmed as the most important NMHC in determining OH removal contributing to up to 20% of OH removal. Isoprene shows strong diurnal variations, although the structure of the diurnal pattern depends on the origin of the air mass. In contrast to previous studies, DMS concentrations during the campaign appeared to show no consistent diurnal variation.

PTV injection has been used extensively as a means of injecting large volumes of samples to enhance sensitivity. This paper describes the use of PTV injection in the desorption mode for the analysis of a range of solid samples, and four examples of this application as a problem solving tool are described in detail. Detection by mass spectrometry was used extensively as a means of identification of the components in the various samples characterized.

The analysis of mixed acid streams plays and important role in the control of production processes for acetic acid and the determination of dicarboxylic and keto-acids, such as succinic (butane-dioic acid) and levulinic acids (4- oxypentanoic acid), can present particular problems to the analyst. As a result derivatisation methods have been employed to achieve satisfactory results in terms of sensitivity and chromatographic resolution in capillary GC. These derivatisation methods however are time consuming and expensive when dealing with a large number of samples. This paper describes the development of a fast and effective technique for quantifying levulinic and succinic acid in process streams for acetic acid production using in-liner derivatisation to silyl ethers in a PTV injector equipped capillary GC. The PTV in-liner derivatisation technique gives efficient conversion to silyl ether derivatives with good precision, minimal sample preparation and low sample volume and reagent consumption and results in a circa 5 fold decrease in analysis time.

This paper describes a new analytical tool for the analysis of geological samples for geochemical purposes. A system is described that allows subsequent thermal treatment at several stages to occur inside the liner of a PTV injector. The samples under investigation are geological hydrocarbon source rock and coal samples. Analysis of the samples is performed in a sequential procedure. A three-step temperature-level procedure is proposed. The system described is inexpensive and easy to operate. The advantages of combining thermal desorption and pyrolysis sequentially inside a PTV injector is the flexibility of temperature selection, as well as the ease of calibration and quantitation. Moreover, the absence of a heated transfer line and heated valves minimizes the risk of loss of high-molecular mass compounds. The method described allows a detailed characterization of oil and kerogen in a source rock. An atomic emission detector is used to monitor simultaneously the carbon and the sulphur signals for further structural elucidation of the kerogen. The results obtained with this system are in good agreement with those obtained with other pyrolysis systems.

Thermal treatment hyphenated with GC is a versatile and powerful tool in the study of polymer characterization. An inexpensive system where thermal treatment at different temperatures occurs inside a PTV injector is described. The samples investigated, commercial plastics, are complex mixtures that contain several polymers and additives. These plastics as well as their pure constituents are subjected to multi-step thermal treatment. The individual chromatograms of the various constituents of the polymeric sample are correlated with those of the final material in order to identify additives (thermal desorption) and degradation products (pyrolysis). Results obtained with the new method indicate the interesting potentials of the technique for the characterization of polymer compositions. Reproducibility of absolute and relative peak areas has been considered and found to be acceptable. The absence of a heated transfer line and switching valves, which are always present in conventional set-ups, eliminates the risk of losses of high molecular weight components. Further advantages of the technique proposed are simplicity, versatility, and its inexpensive nature.

Pressurised liquid extraction (PLE) is essentially an analyte and matrix-independent technique. It provides cleaner extracts than the time-consuming classical procedures. In this study, PLE was miniaturized and performed in a stainless-steel cell of 10mm x 3mm I.D. 50mg amounts of the solid sample were packed in the holder. After being subjected to the PLE procedure, 50 out of 100-µl extracts were introduced into GC-MS using large volume injection (LVI). The new device was applied to the determination of polycyclic aromatic hydrocarbons (PAHs) in soil s and sediment. Evaluation of the pressure and temperature during extraction, and extraction solvent volume and nature (typical variables affecting the PLE efficiency) resulted in selection of 100µl of toluene at 15 Mpa for 10 min in a static-dynamic mode using not more than 50-mg samples. Clean up or filtration of the extracts was not required.

PVC plastic is blended with Nitrile rubber to produce a compound, which is softer and more durable, that pure PVC. Nitrile rubber is a polymeric mixture of butadiene and acrylonitrile in the respective ratio 2:1. The aim of this experiment was to quantify the amount of Nitrile rubber in a PVC plastic sample. Various weights of Nitrile rubber were pyrolysed in the liner of the Optic injector and the products analysed by GC. A peak characteristic of the chromatograms was isolated and a calibration of peak area against sample weight constructed. A known weight of PVC plastic was then pyrolysed under the same conditions and using this calibration the amount of Nitrile rubber in the pyrolysed PVC sample was determined.

Tributyl and triphenyl tin are both EC Red List compounds, which must be determined in water down to levels of 0.1 ppb. Existing methods, involving the use of Grignard reagents for derivatisation, are complex, labour intensive and, as a consequence, costly. This new approach utilises sodium tetraethyl borate as the derivatisation reagent, which makes it considerably simpler. The Optic programmable injector is used to perform large volume injections of the derivatised sample, this increases the sensitivity and therefore eliminates the need for a pre-concentration step.

The headspace GC/MS analysis of five varieties of perpetual flowering carnations and one Malmaison type showed significant differences in the chemical composition of their flower scent. The principal difference in odor between the varieties was accounted for by the proportion of eugenol (trace 84.1%) and methyl salicylate (0.1-1.4 %).

The trace-level analysis of unknown pollutants in water requires the use of fast and sensitive methods, which also provide structural information. In the present preliminary study, solid phase extraction (SPE) programmed temperature vaporization (PTV) and gas chromatography (GC) with mass spectrometric (MS) detection are combined. A fully automated SPE system was connected to a GC via a PTV injector. The PTV injector was selected because of its robustness (over 100 analyses) when analyzing real-life samples. The mass spectrometer was used in the full-scan mode to allow compound identification. The technique is applied to the determination of a series of priority pollutants in water from the river Rhine and Meuse. In this way tributylphosphate and caffeine were detected. The results of this analysis were confirmed by RIZA both qualitative as well as quantitative.

Beside the biological effectiveness the approval of a chemical wood preservative requires also techniques for the analytical determination of active ingredients in different matrices. Fulfilling of the last requirement is particularly difficult in the case of impregnated timber treated with wood preservatives containing organic compounds. This paper describes a procedure for the determination of the organic ingredient N-cyclohexyl-diazeniumdioxide (HDO) in solid phases using gas chromatography coupled with mass spectrometry (GC-MS) in connection with a previous thermal desorption step. For this powdered samples are placed in a glass tube. Then the tube is reinserted into the thermal desorption unit which is placed in the GC-oven and directly connected with the capillary column. Afterwards the sample was quickly heated up to 200°C. The resulting gas mixture is pushed onto the column and the separation of the gas components took place. The single components could be identified by means of the retention time and the mass spectrum. A quantitative determination seems to be possible by means of the intensity of the signals. The suitability and reproducibility of this method of the determination of HDO were tested successfully by analysing a number of impregnated wood specimens treated with different formulations containing HDO.

When analysing very low level samples it is necessary to trap analytes from large volumes of sample. Under these conditions knowledge of the breakthrough volume of an analyte on the trap is important if confidence in the analytical results is to be maintained. When trapping analytes on a packed Optic liner, the packed liner can be considered as a very short packed column so under any conditions of temperature and flow, an analyte will have a finite (but hopefully very large) retention time. By knowing the sample flow rate and the retention time of the analyte under consideration, the breakthrough volume can easily be calculated.

Apples, cabbage and potatoes were used as representatives of the food classes to be examined by this technique. Samples were chopped, macerated and extracted with ethyl acetate. The extracts were then spiked with pesticide mixes to correspond to the Maximum Residue Levels and an order of magnitude above and below this level to represent gross contamination and the lower levels of interest respectively. The ethyl acetate extracts were presented to the Vision. The mixed pesticide standards were analysed on the GC/MS to determine the optimum GC, Optic and Vision conditions for this application. Optimisation of the Optic included establishing the maximum volume to be injected, the solvent venting time and the temperature programming. The washing steps of the cartridges of the Vision were optimised.

The analysis of vehicle paint is often difficult, especially when reaching low detection limits. Here a new technique is introduced where thermal desorption takes place from the sample matrix in the injector liner directly onto the head of the column, using DMI microvials. By using selective exclusion of the major components trace level detection limits may be reached and there is no manual sample preparation. This method may also be automated using the Focus DTD.

In the past, the labile insecticide lambda-cyhalothrin has been very difficult to analyse by gas chromatography. Usually LC-MS is the analysis method of choice. The AT-Column concentration technique is presented as a method of injecting a large volume of the sample into the liner, which contains no packing material. Then, after concentrating the sample by venting the solvent, the analytes of interest are transferred directly onto the head of the column under cool conditions. Little if any compound degradation occurs and no optimisation is required for this technique.

The analysis of volatiles in the gaseous phase is often difficult, with many opportunities for sample losses both in sample collection, transportation and on analysis. The emission of volatiles from a pair of healthy leaflets on a 4- week old broad bean plant was sampled before and after damage. Sampling takes place onto a packed Optic liner, allowing thermal desorption directly onto the head of the column, therefore no manual sample handling is required.

The analysis of soap is often very difficult, both liquid and powdered soap. Using DMI desorption takes place directly from the sample matrix onto the column by placing a small amount of the liquid or soap powder in a DMI microvial. Therefore no manual sample preparation is required so no problems are caused by emulsions forming. This method may also be automated using the Focus DTD.

The analysis of nicotine is often difficult. Using this technique, desorption takes place directly from the sample matrix onto the column. No manual sample preparation is required and this may be automated using the Focus DTD.

A fully automated sample preparation and injection method is presented for the analysis of FAMES in fats and oils using sodium methanolate.

An automated method for the thermal desorption of solid wood samples is presented, which requires no sample preparation.

The Focus Direct-TD is an automated thermal desorber. It uses the Focus autosampling robot to automatically exchange special packed sample tubes, SepLiners, held in a 98-position DTD tray, into the head of the Optic programmable injector. The head is then closed and sealed pneumatically, and the sample is desorbed onto the head of the column and analysed. The Focus DTD can also be used for the automated desorption of solid and liquid samples using the Difficult Matrix Introduction (DMI) technique. Two separate organisations suggested different sets of experiments to test the performance of the Focus-DTD in the thermal desorption role.

The analysis of food products for organic problem compounds such as organophosphorous pesticides is an important task in quality control to assure maximum safety for the customers. High throughput capabilities are as important as reliability and sensitivity of the applied methods. Standard routine GC/MS methods usually require between a 30 and 60 minute run time in addition to a more or less complicated sample preparation procedure. This application note describes the combination of a sophisticated injection system like the ATAS Optic 2 which allows simplification of the necessary sample preparation by means of a large volume injection; and the Pegasus II Time-Of-Flight GC/MS detector enabling the application of fast GC conditions. Together, a powerful analysis system is set up allowing the acceleration of standard food monitoring analyses while maintaining the required quality.

Copes well with the difficult mixture of labile and sticky compounds. No or very little optimisation is required.

Improved sensitivity with large volume injection. Very little optimisation is required. A sensitive and user-friendly system for the trace analysis of drugs.

The determination of chlorinated compounds such as PCBs, dioxins, etc., has always been of interest in environmental analysis. These compounds are known to be carcinogenic, therefore the detection limits of the applied analytical methods need to be as low as possible. One way of achieving high sensitivity is to use large volume injection. This application note describes the combination of a sophisticated injection system like the ATAS Optic 2 in large volume injection mode and the Pegasus II time-of-flight MS detector enabling the application of fast GC conditions. Together, a powerful analysis system is set up allowing the acceleration of standard monitoring analyses while maintaining the required sensitivity.

Current injection techniques consist of split, splitless, and on-column injection. The best technique for eliminating degradation is on-column injection, but industry standards mandate the use of a split/splitless injection port. With oncolumn injection, the analytes are placed directly into the GC column, eliminating residence time in the injection port. This is an advantage as well as a disadvantage. Since the sample is placed directly on column, everything in the sample including non-volatile material enters the column, reducing the lifetime of the column. A new way to reduce degradation is to use a Programmed Temperature Vaporizing (PTV) injector in which the sample is injected into a cold injection port and ramped to the upper temperature required for vaporization.

The low-level detection and quantification of food grade mineral oil in sunflower oil is a difficult analytical problem. The sunflower oil matrix is viscous and contains a high proportion of high molecular weight compounds, which can quickly lead to a contaminated liner, injector, column and detector. A large mineral oil peak can be selected for the quantification, which is relatively volatile so that all of the sample is not necessarily analysed, and with the injection volume kept to a minimum to reach the required detection limits this helps to reduce the problem. However, there is still a build-up of involatile components. Selective exclusion can be used to only transfer those peaks of interest from the injector onto the column, thereby keeping the majority of the involatile components in the liner and greatly reducing contamination of the column and detector. The remaining sample may be vented through the split line, by heating the injector to a very high final temperature, and then trapped.

Acid herbicides were first introduced as weedkillers in the 1940s. They are applied as esters or salts, as they are readily metabolised in this form, to the top of the soil or grass, regulating the growth of mainly broadleaf weeds. They readily degrade in the environment, however the esters are oil soluble and form emulsions in water, whereas the salts are highly soluble in water, therefore the leaching of the acid herbicides into the groundwater causing contamination is of major concern. The analysis of acid herbicides using large volume injection enables detection limits to be more easily reached, and therefore sample preparation to be reduced. A method for the large volume injection using the Optic is presented, along with some performance data.

Eastman Chemical Co.'s Environmental Laboratory in Longview, TX, routinely uses solid-phase extraction (SPE) and rapid, large-volume injection (LVI) to eliminate the postextraction concentration step normally required for the preparation of samples for semivolatiles analyses by U .S. EPA SW846 Method 8270D. Using automated SPE and LVI in place of conventional liquid/liquid extraction eliminates the labour-intensive steps, reduces sample analysis costs, improves accuracy and precision, decreases solvent (methylene chloride) usage, and reduces turnaround time from days to hours.

Biodiesel is a renewable fuel and can be made from most vegetable oils, for example oilseed rape and sunflower oil. It causes less pollution than fossil fuels and is mainly used in the transport industry. It is produced by transesterification of the oil, producing the oil methyl ester (biodiesel) and glycerol, which settles out. Through removal of the glycerol, biodiesel can be used in most diesel engines with little or no modification either on its own or as a mixture with conventional or low sulphur diesel. Here, a simple on-line method is presented as a way of analysing glycerol in biodiesel down to the necessary detection limit of 500 ppm.

The new technique, Solid Sorptive Extraction (SSE) is used to sample the flavour components in yoghurt. Coupled with Direct Thermal Desorption, in the Optic, and GC/MS this is a powerful technique.

The analysis of mixed acid streams plays an important role in the control of processes for the production of acetic acid and the determination of dicarboxylic and keto-acids, such as succinic (butane-dioic acid) and levulinic acids (4- oxypentanoic acid), can present particular problems to the analyst. In process streams at high temperatures these components are fully soluble but at ambient temperatures they can crystallise out resulting in multiphase samples. GC methods using conventional injection techniques therefore require dilution in a solvent to obtain a representative sample with trace level components being close to, or below the detection limit. In addition peak tailing of major acid components can cause further significant problems in conventional GC analysis. As a result, derivatisation methods such as methylation have been developed to enable concentrated liquid and solid samples to be analysed without excessive dilution while achieving satisfactory chromatography.

Solid-phase extraction-pipette tips (SPE-PT) were used for micro solid-phase extraction (mSPE) of lidocaine and diazepam. Off-line analysis was done after in-vial collection for reference purposes, whereas with on-line analysis the eluant was directly introduced into the gas chromatograph. With both methods the total eluant (100 µl) was introduced into the GC, which was equipped with a programmed temperature vaporiser (PTV) for large volume injection. For on-line analysis a home-made coupling device was used to connect the pipette tips with the injector of the PTV. The coupling device was applied successfully for on-line analysis-mSPE since no leakage occurred at the connection surface of coupling device and pipette tip, and no significant differences in recovery of lidocaine and diazepam and presence of impurities were observed between chromatograms obtained with either off-line or on-line analysis. Preliminary experiments with standard solutions showed recoveries of about 75%, at a concentration level of 1 µg/ml. The described on-line analysis seems particularly suitable for high throughput screening.

Allows the direct desorption of analytes from sample matrix to column. It uses a multi-step thermal desorption method followed by pyrolysis of the same sample in the injector and it may be automated using the Focus DTD.

Allows the direct desorption of analytes from the sample matrix to column, eliminates the need for sample preparation and may be automated using the Focus DTD.

No sample preparation is necessary, the method removes water under controlled conditions prior to analysis and retains the salt and involatiles within the microvial.

The extraction of active ingredients from pharmaceutical products, especially creams, can often be a long and tedious process involving many steps and using strongly acidic and basic reagents. An automated extraction method has been written closely following the customers existing manual method, the main difference being that the volumes have been reduced to allow the use of 10 mL headspace vials. The method uses the Focus Sample Processing Robot for the extraction of an active ingredient for the quality control of a pharmaceutical cream.

The parent amino acid water extract normally requires preconcentration and careful derivatisation steps prior to analysis. An alternative method, monitoring the breakdown products of the material at high temperature, allows direct injection of the aqueous extract with minimum sample preparation.

Recently, the analysis of drugs of abuse in human hair has received much attention, primarily as it allows for the determination of long-term trends in drug usage. The analysis of delta-9-tetrahydrocannabinol (THC), the active ingredient of cannabis, and one of its human metabolites 11-nor-delta-9-THC-COOH (THC-COOH) in human hair currently requires solvent extraction of a quantity of hair, concentration of the extract by SPE, derivatisation with BSTFA followed by GC/MS analysis. Using large volume injection with in-liner derivatisation reduces sample preparation and lowers the detection limits.

The Anatune VSA turn-key system has been shown to be a suitable method for the determination of sulphur volatiles in beer. The excellent sensitivity of the Sievers SCD enabled twelve important sulphur compounds commonly found in beer to be successfully calibrated below their respective flavour thresholds. The three main advantages over previous methods are the excellent improvements in precision, making it a much more reliable method (less chance of human error), higher throughput of samples with the use of an autosampler, as the system can run 24 hours a day, and it is less labour intensive.

2D-GC = 2 Dimensional Gas Chromatography P&T = Purge & Trap

DMI = Difficult Matrix Introduction RLVI = Rapid Large Volume Injection

DTD = Direct-Thermal Desorption SCD = Sulfur Chemiluminescence Detector

HT = High Temperature SE = Selective Exclusion

HT deg. = High Temperature Degradation SPE = Solid Phase Extraction

In-liner deriv. = In-liner derivatisation SPME = Solid Phase MicroExtraction

LLE = Liquid-Liquid Extraction TD = Thermal Desorption

LVI = Large Volume Injection TOF = Time Of Flight mass spectrometer