Analysis of sludge extracts by high resolution GC with selective detectors

Combination of various GC detectors by using a Varian effluent splitter with glass capillary columns has been found to be a rapid procedure for profiling organics extracted from sludges and river sediments. The selectivity and the increased sensitivity of the thermionic nitrogen-phosphorus detector (TSD), the electron capture detector (ECD), and the flame photometric detector (FPD) over the flame ionization detectors (FID) or mass spectrometers allow the detection of compounds present at trace levels without need for extensive sample cleanup. Furthermore, the combination of two selective detectors may supplement the information with regard to the chemical functionalities required for structure elucidation.     

Comparison of the performance of graphitized carbon black and poly(styrene-divinylbenzene) cartridges for the determination of pesticides and industrial phosphates in environmental waters

The determination of polar and nonpolar organophosphorus compounds, triazines and their metabolites, molinate and chlorothalonil in 1 l water samples was investigated using off-line solid-phase extraction followed by gas chromatography with nitrogen-phosphorus and flame photometric detection. The ethylvinylbenzene-divinylbenzene copolymer (LiChrolut EN) and the commercial graphitized carbon black (GCB) of Envi-Carb were tested as solid-phase sorbents. The matrix effect was studied by extracting the compounds spiked in water samples of different types (Milli-Q, tap, salted tap water, river and sea water). The polymeric sorbent LiChrolut EN allowed the determination at low ng/l of all 40 compounds tested, except the very polar atrazine-desethyl-deisopropyl (DDA). Recoveries of compounds from the Envi-Carb sorbent are comparable to those obtained for LiChrolut EN with the exception of chlorothalonil and the more hydrophobic organophosphorus compounds (coumaphos, leptophos), which were strongly sorbed in the Envi-Carb cartridges. Envi-Carb, however, enabled the determination of DDA with a limit of detection of 14 ng/l.     

Stability studies of carbamate pesticides and analysis by gas chromatography with flame ionization and nitrogen-phosphorus detection

As a result of thermal stability studies of carbamate pesticides, a method has been proposed for their direct determination by gas chromatography in the ranges 1-20 and 0.1-1 mg l(-1), using flame ionization and nitrogen-phosphorus detection, respectively. The method allows the determination of propham, propoxur, carbofuran, carbaryl, methiocarb, isopropoxyphenol and naphthol in powdered potato samples. The analytes were previously extracted with a light petroleum-dichloromethane (1:1, v/v) mixture and preconcentred by solid-phase extraction through a C8 cartridge. The recoveries obtained from spiked potato samples (n=4 replicates) at two concentration levels, 10 and 0.5 mg of pesticide per kg of sample, were in the ranges 72-115 and 50-73%, with relative standard deviations of 2-7 and 5-8%, respectively. The detection limits were 50-210 and 41-53 microg kg(-1) with flame ionization and nitrogen-phosphorus detection, respectively, and reaching the maximum residue levels, 0.05 mg kg(-1) for methiocarb and propoxur, set by the Real Decreto 280/1994 (based on the European directive).     

Continuous solid-phase extraction and gas chromatographic determination of organophosphorus pesticides in natural and drinking waters

A simple, rapid continuous-flow solid-phase extraction method with gas chromatographic detection for the determination of organophosphorus pesticides is proposed. The continuous system consists of an adsorbent column where pesticides are preconcentrated and subsequently eluted with ethyl acetate. Various sorbent materials were assayed of which RP-C18 was found to provide the best results, with a sorption efficiency close to 100%. A comparative study of the determination of pesticides in aqueous samples was conducted using gas chromatography with nitrogen-phosphorus (NPD) and flame ionization (FID) detection. The detection limits of the method for 10 ml of sample were between 50-130 ng/l and 4.5-1 1.7 microg/l with NPD and FID detection, respectively. The method was used to determine organophosphorus pesticides in river, pond, well and tap waters, all with good precision (2.9-4.3%) and recoveries ranging from 93.8 to 104.5%.     

Rapid analysis of sorbitol, galactitol, mannitol and myoinositol mixtures from biological sources

The three commonly found hexitols mannitol, sorbitol and galactitol are well separated from each other and from myoinositol by gas chromatography as their butylboronate derivative on Dexsil-400, on a 1:1 mixture of OV-1 and OV-17, or on a DB-17 fused-silica capillary column. The method allows all four substances to be measured by autosampling electron ionization gas chromatography-mass spectrometry (GC-MS) in small tissue samples at organ concentrations as small as 5 mumol/kg wet mass in less than 4 min. Comparisons were made to determine the relative sensitivity of GC-MS and other detection methods. The order of sensitivity was electron ionization GC-MS greater than chemical ionization GC-MS greater than flame photometric detection using a boron-selective filter greater than hydrogen flame ionization detection.     

Solid-phase extraction-gas chromatography and solid-phase extraction-gas chromatography-mass spectrometry determination of corrosion inhibiting long-chain primary alkyl amines in chemical treatment of boiler water in water-steam systems of power plants

Gas chromatography with simultaneous flame-ionization detection (FID) and a nitrogen-phosphorus detection (NPD) as well as gas chromatography-mass spectrometry (GC/MS) has been used to characterize long-chain primary alkyl amines after derivatization with trifluoroacetic anhydride (TFAA). Electron impact ionization- (EI) and negative chemical ionization (NCI) mass spectra of trifluoroacetylated derivatives of the identified tert-octadecylamines are presented for the first time. The corrosion inhibiting alkyl amines were applied in a water-steam circuit of energy systems in the power industry. Solid-phase extraction (SPE) with octadecyl bonded silica (C18) sorbents followed by gas chromatography were used for quantification of the investigated tert-octadecylamines in boiler water, superheated steam and condensate samples from the power plant. The estimated values were: 89 microg l(-1)(n = 5, RSD = 7.8%), 45 microg l(-1) (n = 5, RSD = 5.4%) and 37 microg l(-1)(n = 5, RSD = 2.3%), respectively.     

Determination of triphenyltin hydroxide derivatives by capillary GC and tin-selective FPD

A new method for the determination of triphenyltin hydroxide using capillary column gas chromatography with a tin-selective flame photometric detector has been developed. Triphenyltin hydroxide and its potential metabolites are converted to methyl derivatives and separated on glass capillary columns coated with OV-101. Derivatization of triphenyltin hydroxide, triphenyltin chloride, diphenyltin dichloride, phenyltin trichloride, and bis-triphenyltin oxide is nearly quantitative with a minimum of redistribution products. The selectivity of the flame photometric detector is cearly demonstrated by the comparison of chromatographic profiles obtained from using both the flame photometric and flame ionization detectors. The use of this chromatographic system in the analysis of triphenyltin hydroxide in a fortified water sample demonstrates the potential use of this system in organotin residue chemistry.     

Characteristics and performance of gas chromatographic detectors with glass capillary columns

A comparison of the characteristics and Performance of the flame ionization, electron capture, and flame photometric detectors with capillary columns is described. Factors which may affect the limits of detection, linearity, chromatographic peak shape, and other detector performance characteristics are discussed and compared with the results of a model derived for the behavior of concentration and mass flow-rate dependent chromatographic detectors used with capillary GC systems. Examples are given of highly complex and labile mixtures such as pesticide residues and products from coal hydrogenation.     

Application of a system suitability test for quality assurance and performance optimisation of a gas chromatographic system for pesticide residue analysis

In pesticide residue analysis, screening for over 150 compounds has to be performed on a daily basis. As part of the quality control measures it is crucial to verify that the chromatographic system fits the purpose, or if any deterioration occurred during its previous use. The operation conditions of the chromatographic system can be best monitored with properly selected system suitability test (SST) mixtures, which provide information with one injection on the characteristic performance parameters of the whole system from the injector to the detectors. We developed SST mixtures that are also suitable for use with electron-capture, nitrogen-phosphorus and pulse flame photometric detectors. These SST mixtures were applied over 3 years to monitor the system performance parameters, such as the number of effective theoretical plates, resolution, asymmetry, detection limit and selectivity. The applicability and advantages of these tests are illustrated and discussed.     

Evaluation of the performance of various universal and selective detectors for sulfur determination in natural gas

In the present contribution, the performance of a number of commercially available selective and universal detectors that can be used in the analysis of sulfur components in natural gas is evaluated in terms of sensitivity, selectivity, reproducibility, quenching effect, stability, and compound dependence of the sulfur response. Investigated detectors include the sulfur chemiluminescnce, the flame photometric, the electron capture, the mass spectrometric, the thermal conductivity, and the flame ionization detector. The sulfur chemiluminescence detector was found to have the best overall performance, e.g., low picogram amounts of sulfur can be detected accurately and the linear dynamic range is more than five orders of magnitude. After careful optimization, the sulfur response of this detector was found to be almost compound independent. All other detectors, including the flame photometric and the electron capture detector, have more or less compound dependent responses.     

Determination of mono- and sesquiterpenes in water samples by membrane inlet mass spectrometry and static headspace gas chromatography

A membrane inlet mass spectrometric (MIMS) method is presented and compared with a static headspace gas chromatographic method (HSGC) for the determination of terpenes in water. The MIMS method provides a very simple and fast analysis of terpenes in water, detection limits being relatively low, from 0.2 mug l(-1) for monoterpenes to 2 mug l(-1) for geraniol. The analysis of terpenes by the HSGC (equipped with flame ionization detector, FID) method is more time-consuming and the detection limits (2 mug l(-1) for monoterpenes to 100 mug l(-1) for geraniol) are higher than with MIMS. However, the HSGC method has the advantage of determining individual mono- and sesquiterpene compounds, whereas MIMS provides only separation of different classes of terpenes. Both methods were applied to the analysis of mono- and sesquiterpenes in several condensation water samples of pulp and paper mills.     

Determination of methanol and ethanol by gas chromatrography following air sampling onto florisil cartridges and their concentrations at urban sites in the three largest cities in Brazil

A new sampling protocol was developed to determine methanol and ethanol in the gas phase, at low concentration levels, in urban atmospheres. The procedure involves collection of air samples (20.0-30.0 l) with three florisil cartridges connected in series, at a flow rate ranging from 1.0 to 2.0 l min(-1) and subsequent elution of the alcohols with water. Separation and quantification were done by gas chromatography (GC) coupled with a flame ionization detector, 'SPI' injector and column DB WAX (30 mx0.53 mmx1 mum). The minimum mass detected by the method, based on two times the average background mass on the blank cartridges, was 0.3 mug for both alcohols which, for a sampled volume of 30 l, resulted in detection limits of 7.6 and 5.3 ppbV for methanol and ethanol, respectively. The determined alcohol concentrations, in 42 different samples from the three largest cities in Brazil-S?o Paulo, Rio de Janeiro and Salvador-ranged from 72 ppbV to below the detection limit for methanol and from 355 to 12 ppbV for ethanol.     

tability Indicating Method for the Analysis of Nicotine in Transdermal Drug Delivery Systems by Means of Gas Chromatography

The delivery of drugs through human skin using transdermal drug delivery (TDD) systems has become an established technology. A popular drug with that dosage form is nicotine for smoking cessation. A stability indicating method for the analysis of nicotine TDDs using gas chromatography (GC) with post-column effluent splitting to a flame ionization detector (FID) and a nitrogen-phosphorus detector (NPD) is described. FID detection gave reliable results with low day-to-day variability. The detector is relatively simple to operate. NPD detection offered enhanced sensitivity and specificity. The combination of both detectors resulted in a rugged method for content analysis with high sensitivity for detection of degradation products at low concentration levels. Despite a relatively simple sample preparation procedure no matrix interferences were observed.     

Gas chromatographic data for 187 nitrogen- or phosphorus-containing drugs and metabolites of toxicological interest analysed on methyl silicone capillary columns

Retention data, retention indices and retention times relative to diazepam, associated with 187 nitrogen- or phosphorus-containing drugs and metabolites likely to be found in toxicological analysis, are presented. The work was carried out with cross-linked methyl silicone, siloxane-deactivated fused-silica capillary columns in different gas chromatographs equipped with nitrogen-phosphorus flame ionization detectors and a gas chromatograph-mass spectrometer. Results show the high reproducibility offered by the capillary system, which permits the reduction of identification problems and analysis time.     

Application of microcolumn liquid chromatography and capillary electrophoresis with flame photometric detection for the screening of degradation products of chemical warfare agents in water and soil

Microcolumn liquid chromatography (microLC) and capillary electrophoresis (CE) coupled on-line with flame photometric detection (FPD) have been used for the screening of polar breakdown products of chemical warfare agents in water and soil samples, provided during Official Proficiency Tests organized by the Technical Secretariat of the Organization for the Prohibition of Chemical Weapons. CE-FPD is shown to be a powerful and rapid method for the determination of alkylphosphonic acids, which are the breakdown products of organophosphorus nerve agents. Gradient elution microLC-FPD is more sensitive and robust but less rapid in the determination of these compounds. In addition, microLC-FPD can be applied to screen for hydrolysis products of sulfur mustard and its analogues. Both methods can be applied without prior derivatization and are extremely selective. In order to unambiguously identify the relevant compounds, electrospray ionization (tandem) mass spectrometry, gas chromatography-mass spectrometry and nuclear magnetic resonance spectrometry were applied.     

Screening and confirmation of thyreostatics in urine by gas chromatography with nitrogen-phosphorus detection and gas chromatography-mass spectrometry after sample clean-up with a mercurated affinity column

Methods are described for the screening and confirmation of residues of the thyreostatics thiouracil, methylthiouracil and propylthiouracil in urine samples of cattle at levels down to 25 micrograms/l. After a selective preconcentration of the thiol-containing thyreostatics on a mercurated affinity column, the analytes are derivatized by extractive alkylation and analysed by gas chromatography with nitrogen-phosphorus or mass spectrometric detection.     

A novel method for the calibration of Kováts retention indices using n-alkanes with a thermionic nitrogen-phosphorus specific detector

This paper describes a novel method for the detection of compounds that do not contain nitrogen or phosphorus by a thermionic nitrogen-phosphorus specific detector (NPD), which normally detects only nitrogen- or phosphorus-containing compounds. This method allows for the calibration of gas chromatographic columns with NPD detectors using n-alkanes instead of nitrogen-containing drug mixtures. This results in a more rapid and accurate calibration for the calculation of relative retention indices (RRI), such as Kováts indices, than was previously possible when employing an NPD detector. The proposed method describes the temporary conversion of the NPD detector into a detector with properties much like a flame ionization detector. After a deliberate increase in the hydrogen gas flow rate to the thermionic bead from 4 ml/min to 8 ml/min, the n-alkanes (containing no nitrogen) can be detected and used as RRI calibrators. Once the column has been calibrated, the hydrogen gas flow rate is lowered to the normal rate of 4 ml/min. The detector then behaves as a normal NPD, no longer detecting the n-alkanes.     

Gas chromatographic determination of benzene, toluene, ethylbenzene and xylenes using flame ionization detector in water samples with direct aqueous injection up to 250 microl

A simple method of solventless extraction of volatile organic compounds (benzene, toluene, ethylbenzene and xylenes) from aqueous samples was developed. This method allows direct injection of large volume of water sample into a gas chromatograph using the sorption capacity of the sorbent Chromosorb P NAW applied directly in the injection port of gas chromatograph. The system prevent water penetration into a column, keep it adsorbed on its surface until the analytes are stripped into a column, and the residual water is purging using split flow. The limit of detection ranging from 0.6 for benzene to 1.1 microg l(-1) for o-xylene and limit of quantification ranging 2.0-3.6 microg l(-1) are lower that those reached by gas chromatography with flame ionization detection and direct aqueous injection before.     

Evaluation and comparison of selective gas chromatographic detectors for the analysis of pesticide residues

Summary A series of studies is described on the evaluation and comparison of some selective gas chromatographic detectors used in pesticide residue analysis. A detailed study of the optimization and response characteristics of the CsBr and RbCl three-electrode alkali flame ionization detector for N and P compounds, the Coulson electrolytic conductivity detector in the nitrogen, sulphur and pyrolytic modes of operation and the sulphur phosphorus emission detector, a type of flame photometric detector, was carried out to obtain maximum sensitivity and reliability for the analysis of pesticide residues in various biological substrates. It was observed that the alkali flame and electrolytic conductivity detector responses to nitrogen compounds were of the same order, while the electrolytic conductivity detector was more sensitive than the flame photometric detector to sulphur compounds. Also, attempts were made to correlate the responses from these different detector systems using the insecticide chlorpyrifos which contains P, S, Cl and N atoms. The use of chlorpyrifos as an evaluation standard in verifying the acceptable performance of these types of detectors is recommended.Chemistry and Biology Research Institute Contribution No 901     

Liquid chromatography/atmospheric pressure photoionization tandem mass spectrometry for analysis of Dechloranes

Liquid chromatography/atmospheric pressure photoionization tandem mass spectrometry (LC/APPI-MS/MS) was investigated as an instrumental method for the analysis of the halogenated norbornene flame retardants, Mirex, Dechloranes 602, 603, 604, and Dechlorane Plus (DP). The LC separation was optimized by screening a variety of stationary and mobile phases, resulting in a short LC separation time of 5 min. Different atmospheric pressure ionization approaches were examined including electrospray ionization, atmospheric pressure chemical ionization, and APPI, each with and without post-column addition. APPI without post-column addition was chosen for providing the best ionization response. The optimized LC/APPI-MS/MS approach resulted in instrument detection limits ranging between 25 and 50 pg. Good linearity was also achieved (up to 25.0 ng/μL; R >0.999). The method was applied to extracts of environmental samples including surface water, fish and sediments for screening purposes, and the results agreed well with those obtained by gas chromatography/mass spectrometry.