Evaluation of capillary gas chromatography for multicomponent drug analysis

Capillary gas chromatography is evaluated for multicomponent drug analysis. A 0.32 mm id X 30 m fused silica column and a 0.75 mm id X 30 m borosilicate glass column (both with OV-1 bonded phase) are investigated. Retention times (relative to caffeine) are presented for 39 drug components representing a variety of chemical classes and pharmacological activities. Reproducibility data are presented for both isothermal and programmed temperature runs on selected drug mixtures. Recovery data are provided for 2 multicomponent drug mixtures prepared to approximate over-the-counter antihistaminic and antitussive preparations.     

Multiresidue method for the analysis of pesticide residues in fruits and vegetables by accelerated solvent extraction and capillary gas chromatography

An analytical procedure using accelerated solvent extraction and capillary gas chromatography with electron capture and flame photometric detections was developed to simultaneously determine residues of different pesticides in fruits and vegetables. Single laboratory validation of the method was carried out for 28 compounds selected from eight pesticide classes, in blank and fortified samples of fresh pear, cantaloupe, white potato, and cabbage. The method had to meet specific established validation criteria for regulatory purposes applicable to our laboratory. At each of the two fortification levels studied, 24 of the 28 pesticides gave recoveries of more than 70% with a coefficient of variation of less than 10%. With respect to existing procedures, the method showed acceptable limits of detection (from 0.0019 to 0.14 microg/g depending on the pesticide and matrix) while minimizing environmental concerns, time, and labor.     

Comparison of dieldrin, lindane, and DDT extractions from serum, and gas-liquid chromatography using glass capillary columns.

Rats were given an oral dose of 14C-labeled chlorinated pesticides to obtain serum containing p,p'-DDT, dieldrin, or lindane. Simple hexane and formic acid-hexane extraction methods, involving pretreatment of the serum with formic acid, were compared by radiometric and by paper chromatographic and gas chromatographic analysis. In vivo binding of chlorinated pesticides to constituents of the serum does not necessarily prohibit their isolation by simple hexane extractions, provided that the extraction is very vigorous and at least 5 min long. Stable emulsions were broken by cooling in liquid nitrogen or Dry Ice-acetone. The hexane extraction method described yields quantitative recovery of the pesticides studied, whereas the formic acid-hexane method is quantitative for p,p'-DDT, 93% for dieldrin, and 89% for lindane. Gas chromatographic comparison of both methods, using human serum, shows that the hexane method extracts 16% more beta-BHC, 7% more dieldrin and HCB, and 4% more p,p'-DDE from serum than does the formic acid-hexane method. The difference for p,p'-DDT is not significant. Gas chromatography with glass capillary columns and an all-glass solids injection system yielded detection limits as low as 15 fg. Data show that the use of an internal standard considerably improves the precision of quantitation.     

Behavior of 78 pesticides and pesticide metabolites on four different Ultra-Bond gas chromatographic columns

The gas chromatographic (GC) elution order and relative retention time data (compared to aldrin) are presented for 78 pesticides and pesticide metabolites on 4 different types of commercially available 2 mm id Ultra-Bond columns including Ultra-Bond 20M (20M), Ultra-Bond 20SE (20SE), Ultra-Bond 20M coated with 1% OV-210 (OV-210), and Ultra-Bond 20M coated with 0.5% OV-210 + 0.65% OV-17 (mixed phase). Relative retention time data (compared to parathion) are also represented for 19 organophosphorus insecticides on the 4 Ultra-Bond columns evaluated. Corresponding 4 mm id Ultra-Bond columns were evaluated at the same time as the 2 mm id columns, and results and comparisons for these larger-diameter columns are discussed. These data indicate that, with aldrin as a reference peak, a complement of the mixed-phase column and either the 20M, the 20SE, or the OV-210 column represents a useful chromatographic tool for dual-column analysis of pesticide residues. The 2 mm id columns were more useful in chromatographing later-eluting pesticides whereas the corresponding 4 mm id columns were more useful in chromatographing earlier-eluting pesticides.     

Gas chromatographic relative retention data for pesticides on nine packed columns: II. Organophosphorus and organochlorine pesticides, using electron-capture detection

The retention time relative to parathion, absolute retention time, concentration range, peak asymmetry factor, and peak shape class are given for each of 42 organophosphorus pesticides and 28 organochlorine pesticides analyzed by gas chromatography (GC) on 9 different packed columns. The packing materials used were 3% SP-2100, 1% Dexsil-300, 3% OV-17, 1.5% OV-17 + 1.95% QF-1, 4% SE-30 + 6% QF-1, 3% OV-17 + 3% OV-210, 5% DC-200 + 7.5% QF-1,3% Carbowax-20M, and 4% Reoplex-400. Retention data were determined at 200 degrees C with a carrier gas flow at uopt, using a 63Ni electron-capture detector. Results should be useful for preliminary identification of environmental samples and also for single or multiple pesticide residue analysis.     

Analysis of organochlorine pesticide residues using simultaneous injection of two capillary columns with electron capture and electrolytic conductivity detectors.

A system has been developed that will allow low level screening of 31 organochlorine pesticide residues using simultaneous injection on 2 dissimilar capillary columns. An electron capture detector was attached to a DB-1701 column, and an electrolytic conductivity detector in the halogen mode was attached to a DB-5 column. Chlorinated pesticide amounts ranging from 0.05 ng for gamma-BHC to 1.5 ng for decamethrin can easily be quantitated and confirmed. The system can be used in either the column programmed mode or the isothermal column mode. Good reproducibility was obtained for injections in both modes. This system can easily be retrofitted to any gas chromatograph using on column or split/splitless injectors.     

Measurement uncertainty associated with sample processing of oranges and tomatoes for pesticide residue analysis

The homogeneity of analytical samples and the stability of pesticides during the sample processing of oranges and tomatoes were evaluated. The mean concentrations of 14C-labeled chlorpyrifos in analytical portions (subsamples) after processing show that homogeneity is dependent on sample type as well as the processing procedure. The homogeneity of analytical samples of tomatoes processed cryogenically was much better than those processed at ambient temperature. For tomatoes, the minimum analytical portion masses required for between-analytical portion variation of < 0.3 Ho were 110 and 5 g for processing at ambient and cryogenic temperatures, respectively. Results for orange showed that analytical portion sizes of 5 g provided sufficient homogeneity from both sample processing procedures. Assessments of pesticide stability demonstrated that most were relatively stable during processing at either ambient or cryogenic temperatures. However, some pesticides, including dichlofluanid, chlorothalonil, tolylfluanid, and dicloran, appeared to suffer much greater losses (>20%) during processing at ambient temperature. For these analytes, loss is interpreted as chemical degradation.     

Determination of chlorinated pesticide residues in foods. II. Simultaneous analysis of chlorinated pesticide and phthalate ester residues by using AgNO3-coated Florisil column chromatography for cleanup of various samples.

A simplified method suitable for simultaneous analysis of chlorinated pesticide and phthalate ester residues in various foods was developed. Chemical residues were quantitatively extracted from fatty and vegetable samples with acetonitrile as follows: Chemical standard in 0.5 mL ethanol solution was added to 10 g homogenized sample. After 3 hr, pork and beef were extracted 3 times with 20 mL portions of acetonitrile. The acetonitrile layers were diluted with water and extracted with n-hexane. Rice samples were combined with 10 mL water, 5 mL acetonitrile and 1 mL ethanol and extracted 3 times with 20 mL portions of n-hexane. The n-hexane concentrate from each sample was submitted to AgNO3-coated Florisil column chromatography. The AgNO3 coating adequately adsorbed interfering coextractives. Extracts of fish and vegetable samples were separated into 2 fractions by the above column chromatography. Supplemental cleanup procedures were also developed to accurately determine phthalate esters eluted in the second fraction. Satisfactory gas chromatograms were obtained for most samples.     

Automated sample cleanup for pesticide multiresidue analysis. Part II--Design and evaluation of column chromatography module

An automated, continuous flow system is described for Florisil column chromatography of pesticide residues from food extracts. Evaluation of the system using 5 common organochlorine and organophosphorus pesticides in 2 crop matrices demonstrates essentially no difference in recovery or precision between automated and currently used manual analyses. The automated procedure uses only 20% of the solvents and adsorbents used in the manual procedure and is 3 times faster.     

Analysis of pesticide residues by chemical derivatization. II. N-methylcarbamates in natural water and soils.

A method for the quantitative determination of several N-methylcarbamates in natural waters and the applicability of the derivative to soil samples using a previously published extraction procedure are described. After extraction of the carbamates from the substrate, the carbamates are hydrolyzed in a 10% methanol-potassium hydroxide solution to form the phenolic hydrolysis products, which are isolated and derivatized with pentafluorobenzyl (PFB) bromide to produce the PFB ether derivatives. The PFB derivatives are cleaned up and fractionated on a silica gel microcolumn and determined by electron capture gas-liquid chromatography (GLC). Eight organophosphate pesticides and 2 phthalate acid esters that hydrolyze to phenols or phthalic acid were evaluated as potential interferences and were found not to interfere with any of the carbamates tested. Quantitative determinations of 0.1 mug carbofuran and 3-ketocarbofuran and 0.5 mug carbaryl, metmercapturon, and Mobam in a 1 L water sample are possible. Propoxur was not determined at levels less than 1 mug/L due to the short GLC retention time of the derivative and interferences from the reagents at the lower levels.     

Separation and determination of diesel contaminants in various fish products by capillary gas chromatography.

A semiquantitative capillary column gas chromatographic method is described for the determination of diesel fuel contamination in various canned seafood products. The diesel contaminants are separated from the fish sample by steam distillation, with little carry-over of interfering intrinsic materials such as fish oils. The diesel fuel is extracted from the condensate with n-hexane, and the extract is analyzed on an SPB-1 fused silica capillary column. The efficiency of recovery of diesel fuel added to canned seafood at levels of 40-400 ppt ranged from 72 to 102%. With the additional step of concentrating the hexane extract, the sensitivity of this procedure may be increased at least 10-fold. This procedure can detect the differences among diesel fuel grades No. 1, 2, and 5, and variations within diesel grade No. 2, and thus may be useful in determining the type of petroleum contaminants present in various canned fish products.     

Mass spectral investigations on trichothecene mycotoxins. II. Detection and quantitation of macrocyclic trichothecenes by gas chromatography/negative ion chemical ionization mass spectrometry

A general, sensitive gas chromatographic/negative ion chemical ionization mass spectrometric (GC/NICIMS) method of analysis was developed for the detection and quantitation of several polar, thermally labile, toxic macrocyclic trichothecenes. The procedure involves the conversion of the molecules to their corresponding alcohols (verrucarols) by alkaline hydrolysis, followed by derivatization of the hydrolysate with heptafluorobutyrylimidazole and analysis by GC/MS technique under negative ion chemical ionization conditions. Nanogram (250 ng) quantities of several macrocyclic trichothecenes with different verrucarol and ester moieties were analyzed successfully with good precision by this procedure. The method was applicable for the accurate determination of at least low ppb levels of these macrocyclic trichothecenes in environmental samples, such as fungal products, fermentation broths, and plant samples. This is the first reported, well developed, sensitive, and applicable method for the detection and quantitation of these compounds in naturally occurring samples.