Wide-bore Capillary Gas Chromatography Research Articles

Rapid and simple analysis of oxazolobenzodiazepine drugs in sera by wide-bore capillary gas chromatography with nitrogen-phosphorus detection using on-column methylation

A rapid and simple method for determination of oxazolobenzodiazepines (oxazolam, haloxazolam, mexazolam, cloxazolam, and flutazolam) in sera was developed by gas chromatography (GC) using nitrogen-phosphorus detection (NPD) and a methyl silicone fused-silica wide-bore capillary (DB-1) column. Underivatized oxazolobenzodiazepine drugs gave relatively low sensitivity, because of decomposition during their passage through the column. On the other hand, on-column methylation of the oxazolobenzodiazepines with 0.4 mM trimethylanilium hydroxide in methanolic solution resulted in higher sensitivity; detection was possible at levels at least two to eight times lower than those without derivatization. The average recoveries of five oxazolobenzodiazepines from 0.5-ml volumes of sera containing 1.0 or 0.1 μg of each drug were 88–101% and 66–106%, respectively. The limits of detection of methylated oxazolobenzodiazepines by wide-bore capillary GC-NPD were 50–100pg on column. This method could be used for determination of the drugs in actual serum specimens with concentrations as low as 25–70ng/ml.

Breath biomarkers for detection of human liver diseases: preliminary study

Chronic liver disease is initially occult, has multiple aetiologies, involves complex diagnostic questions, and requires follow-up because progression is likely. Blood tests and biopsies are generally used, but have disadvantages. We have developed a new test for liver disease based on abnormal concentrations of metabolic products detected in exhaled breath. This test can be used, in conjunction with other clinically accepted diagnostic protocols, to detect and classify chronic liver diseases. Samples of breath collected from spontaneously breathing human subjects (86 patients presenting with 13 liver diseases and 109 subjects with normal liver function) were concentrated cryogenically and analysed by wide-bore capillary gas chromatography using various detectors. The concentrations of various molecules in exhaled breath were examined for potential use as biomarkers of liver function. Subjects with chronic liver diseases could be differentiated from those with normal liver function by comparing levels of breath carbonyl sulphide, carbon disulphide and isoprene; these differences were confirmed and correlated by comparing the levels with standard clinical blood markers of liver damage. The presence of chronic liver failure can thus be detected with sensitivity and specificity by quantifying sulphur-containing compounds arising from the abnormal metabolism associated with liver disease. The breath test we have developed appears to distinguish between hepatocellular and biliary tract aetiologies, and allows staging for severity. This approach may provide the clinician with a simple, non-invasive technique for use in the screening of large populations and follow-up for patients with chronic liver disease.

Coupling of thermal desorption in modified closeable sampling columns with wide-bore capillary gas chromatography and mass spectrometric detection

In contrast to usability of Curie-point pyrolysis at 700°C directly attached to gas chromatography-mass spectrometry (GC-MS) for determination of organic wood preservatives in waste wood samples the investigation method reported here consists of thermal desorption at temperatures about 260°C in connection with GC-MS for peak identification or GC with flame ionization detection for quantitative analyses. So-called “modified closeable sampling columns” are used as batch-reactor in thermal desorption experiments. Desorbed vapours can be introduced on capillary columns without sample discrimination and without a disturbing lost of resolution. In this manner a lot of individual polycyclic aromatic hydrocarbons were determinated in waste wood samples, especially in railway sleepers.

Determination of ester-type local anesthetic drugs (procaine, tetracaine, and T-caine) in human serum by wide-bore capillary gas chromatography with nitrogen-phosphorus detection.

A sensitive method for simultaneous determination of ester-type local anesthetic drugs (procaine, tetracaine, and T-caine) has been developed using wide-bore capillary gas chromatography with nitrogen-phosphorus detection (GC-NPD). The extraction procedure, the experimental conditions for heptafluorobutyryl (HFB) derivative formation, and the percentage of the ester-type local anesthetic drugs from the human serum are described. The HFB derivatives of ester-type local anesthetic drugs showed sensitivity of approximately 2-3 fold higher than that without derivatization. The detection limits of HFB derivatives of the ester-type local anesthetic drugs were approximately 60-70 pg on column. Recoveries from the human serum were 85-94%. This method could be used to determine concentrations as low as 24-28 ng/mliters of the ester-type local anesthetic drugs.

Modification of AOAC Multiresidue Method for Determination of Synthetic Pyrethroid Residues in Fruits, Vegetables, and Grains. Part II: Acetone Extraction System

To optimize conditions and to evaluate further a multiresidue method for pyrethroids, various extraction solvents and partitioning conditions were examined. Acetone and acetonitrile (for fruits and vegetables) and acetone-water and acetonitrile-water (for grains) were used as solvents with or without acetonitrile partitioning. Twenty crops fortified with 8 pyrethroid insecticides at low, medium, and high levels were analyzed. For limit of detection (LOD) levels, repeatability tests were completed with acetone-water as extraction solvent. Recoveries of 8 pyrethroid insecticides at LOD levels were 76.2-99.6%, with coefficients of variation (CVs) of 2.08-10.90% for narrow-bore capillary gas chromatography (GC) (n = 6) and 80.1-107.3% with CVs of 3.76-15.38% for wide-bore capillary GC (n = 6). Both acetone or acetone-water extraction with acetonitrile partitioning and acetonitrile or acetonitrile-water extraction with acetonitrile partitioning are suitable for multiresidue analysis of pyrethroid insecticides. However, acetonitrile and acetonitrile-water as extraction solvents were better than acetone and acetone-water at LOD-fortified levels. This finding was confirmed chromatographically with pear, cucumber, and barley control samples.

Determination of tris(2-chloroethyl) phosphate in leachates from landfills by capillary gas chromatography using flame photometric detection

Tris(2-chloroethyl) phosphate (TCEP) in leachates from landfills for hazardous wastes was determined by wide-bore capillary gas chromatography using flame photometric detection. Its concentration levels ranged from 0.137 to 5.43 mg l . The origin of TCEP seems to be waste plastics. No TCEP was detected in underground water and tap water.

Measurement of felbamate by wide-bore capillary gas chromatography and flame ionization detection

Felbamate, a newly developed antiepileptic agent, has been demonstrated to control partial and generalized seizures effectively. We have developed a gas-chromatographic method for the determination of felbamate, using a wide-bore capillary column, a flame ionization detector, and a simple extraction procedure. The assay day-to-day precision (n = 20) was 5.2% and 3.6% for drug concentrations of 50 and 150 mg/L, respectively; average recovery over a wide range of felbamate concentrations was 95%; the detection limit was 5 mg/L; and assay linearity extended to 300 mg/L. Although 9 of the 27 drugs tested were coextracted with felbamate, they exhibited significantly different retention times and showed no interference. A short-term stability study showed that plasma felbamate is stable at 4, -20, or -78 degrees C for at least 1 month. Plasma felbamate concentrations in 66 pediatric patients ranged from 7 to 154 mg/L (mean +/- SD 44 +/- 24.7). We consider the method ideally suited for therapeutic monitoring of plasma felbamate concentration.

Determination of basic drugs extracted from biological matrices by means of solid-phase extraction and wide-bore capillary gas chromatography with nitrogen-phosphorus detection.

Determination of basic drugs from biological matrices at concentration levels of 100-200 ng/mL was accomplished by using mixed-mode Bond Elut Certify columns and a gas chromatograph equipped with a nitrogen-phosphorus detector. The extraction procedure developed for general drug screening on a GC-FID system was found suitable for the extraction of basic drugs from plasma and whole blood for GC-NPD analysis. For urine samples, an extra wash step with 20% acetonitrile in water was required to obtain clean extracts. The recoveries of 18 basic drugs ranged from 77.7 to 104.5%, with relative standard deviations less than 7.0%.

Rapid toxicological screening of barbiturates in plasma by wide-bore capillary gas chromatography and nitrogen-phosphorus detection.

A rapid screening technique for the identification and quantitation of some barbiturates in plasma is reported. The method employs a one-step extraction at pH 5.8 into an organic phase, separation of compounds by gas chromatography with a wide-bore (0.75-mm i.d.) fused-silica capillary column connected to a direct injection kit, and nitrogen-phosphorus detection. Identification of each barbiturate is by retention time relative to brallobarbital, confirmed using another wide-bore column of slightly different polarity, connected to a flame-ionization detector. Rapid quantitation may be obtained with extracted standards used for drug screening. Detection threshold (0.5 micrograms/mL in a 0.5-mL serum sample and 0.5-microL injection volume), precision (CV < or = 11%), and linearity (r > 0.99) were satisfactory for routine toxicological applications.

Quantitative determination of sodium lauroyl sarcosinate by gas chromatography

A simple and rapid procedure is described for the isolation, silylation and wide‐bore capillary gas chromatographic quantitation of sodium lauroyl sarcosinate in personal care products. The sample is dissolved in acidified dimethylformamide to simultaneously acidify/extract the lauroyl sarcosine; an aliquot is then derivatized withbis trimethylsilyltrifluoroacetamide and quantitated by widebore capillary gas chromatography with flame ionization detection.

Rapid isolation with Sep-Pak C18 cartridges and wide-bore capillary gas chromatography of bromisovalum.

A simple and rapid method for isolation of bromisovalum with Sep-Pak C18 cartridges from human whole blood, plasma, and urine containing allylisopropylacetylurea as an internal standard, is presented. Detection of the drugs was made by nonpolar wide-bore capillary gas chromatography (GC) with flame ionization. The drug-containing samples, after mixing with water, were directly applied to the cartridges and eluted with chloroform-methanol (9:1). The recoveries of bromisovalum with use of the cartridges were excellent. Bromisovalum and internal standard allylisopropylacetylurea could be satisfactorily separated from each other and from impurities with the wide-bore capillary column. The detection limit for bromisovalum was 2-5 ng in an injected volume.

Drug matrix effect on the determination of residual solvents in bulk pharmaceuticals by wide-bore capillary gas chromatography.

A wide-bore capillary gas chromatographic method has been developed to study the drug matrix effect on the determination of residual solvents in bulk pharmaceuticals. A selective method is achieved on a Restek wide-bore (0.53-mm i.d. x 30 m) open-tubular fused-silica column coated with a 5-micron film of 95% dimethyl-5% diphenyl polysiloxane protected by a phenyl-methyl siloxane deactivated, uncoated fused-silica guard column. Utilizing this method, several common process solvents in weakly acidic, weakly basic, and neutral drug matrices are evaluated by recovery and linearity studies to show whether or not a drug matrix effect exists in their determination.

Positive and negative ion mass spectrometry and rapid isolation with Sep-Pak C 18 cartridges of ten local anaesthetics

The positive ion electron impact (PIEI), positive ion chemical ionization (PICI) and negative ion chemical ionization (NICI) mass spectra and a rapid isolation procedure using Sep-Pak C 18 cartridges are presented for ten local anaesthetics. In the PIEI mode, molecular peaks were very small or missing for most compounds. Peaks at m z 86 due to the diethylaminomethyl or propylaminoethyl group constituted base peaks in six compounds. In the PICI mode, peaks due to M + H and M + C 2H 5 appeared. The cation at m z 86 was also observed for the six compounds. This ion seems useful for the screening of local anaesthetics. In the NICI mode, anions at m z M − H constituted base peaks for all compounds, peaks at m z M + 12 appeared in many compounds. The total ion current in the PIEI and PICI modes generally gave higher sensitivity than in the NICI mode. Local anaesthetics present in whole blood or cerebrospinal fluid (CSF) could be rapidly isolated by use of Sep-Pak C 18 cartridges with chloroform/methanol as an elution solvent. Their detection was possible using wide-bore capillary gas chromatography with SPB-1 and HP-17 wide-bore capillary columns with satisfactory separation from impurities.

Gas Chromatographic Determination of Captan, Folpet, and Captafol Residues in Tomatoes, Cucumbers, and Apples Using a Wide-Bore Capillary Column: Interlaboratory Study

An interlaboratory study of the determination of captan, folpet, and captafol in tomatoes, cucumbers, and apples was conducted by 4 laboratories using wide-bore capillary column gas chromatography with electron capture detection. The 3 fungicides were determined using the Luke et al. multiresidue method modified to include additional solvent elution in the optional Florisil column cleanup step used with this method. The crops were fortified with each fungicide at 3 levels per crop. Mean recoveries ranged from 86.2% for a 25.1 ppm level of captan in apples to 115.4% for a 0.288 ppm level of captafol in apples. Interlaboratory coefficients of variation ranged from 3.4% (24.7 ppm folpet) to 9.7% (0.243 ppm captafol) for tomatoes; from 2.8% (2.0 ppm captafol) to 8.2% (24.8 ppm captan) for cucumbers; and from 1.5% (0.234 ppm folpet) to 22.1% (0.266 ppm captafol) for apples.

The Determination of Nitroaromatics and Nitramines in Ground and Drinking Water by Wide-Bore Capillary Gas Chromatography

A method has been developed to determine the concentration of nitroaromatics and nitramines in drinking water at levels below those previously achieved by gas chromatography. The nitroaromatics and nitramines are extracted from water using toluene and isoamyl acetate, respectively. The extracts are analyzed via a gas chromatograph equipped with a DB-1301 widebore fused-silica capillary column and an electron capture detector. Method detection limits of 0.003 micrograms/L for 2,6-dinitrotoluene (2,6-DNT), 0.04 micrograms/L for 2,4-dinitrotoluene (2,4-DNT), 0.06 micrograms/L for 2,4,6-trinitrotoluene (TNT), 0.3 micrograms/L for cyclotrimethylenetrinitramine (RDX), and 6.0 micrograms/L for cyclotetramethylenetetranitramine (HMX) have been obtained using this method.

Rapid Isolation with Sep-Pak C18 Cartridges and Wide-Bore Capillary Gas Chromatography of Benzophenones, the Acid-Hydrolysis Products of Benzodiazepines

A simple extraction procedure with a Sep-Pak C18 cartridge for benzophenones and their detection after separation by wide-bore capillary gas chromatography (GC) are presented. The benzodiazepine-containing samples, after heating in acid and centrifugation, were passed through the cartridges and eluted with chloroform. Except for bromazepam, the recoveries of benzodiazepines detected as benzophenones were excellent. Separation of each benzophenone peak from impurities was achieved with an intermediately polar HP-17 capillary column. Electron capture detection gave sensitivity more than 10 times higher than that of flame ionization detection.

Simple Analytical Method for Organophosphorus Pesticide Residues in Milk

A simple method for determination of organophosphorus pesticide residues at the parts per million level in milk was developed. Pesticide residues were extracted with acetonitrile added to aqueous milk, fat was removed by zinc acetate addition and dichloromethane partition, and analytes were concentrated and analyzed by wide-bore capillary column gas chromatography. Recoveries of 6 pesticides spiked in milk samples at levels of 0.1 and 1.0 micrograms/mL were 82.1-93.8% and 79.7-96.6%, respectively. Triplicate samples spiked with 6 pesticides at 1 microgram/mL were analyzed independently by 3 laboratories. Average recoveries were greater than 80%, and the mean coefficients of variation for the complete study were 2.9% for diazinon, 5.4% for dimethoate, 4.6% for malathion, 4.6% for parathion, 4.9% for EPN, and 6.1% for phosalone.

Positive- and negative-ion mass spectrometry and rapid clean-up of some carbamate pesticides

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra of 9 carbamate pesticides are presented. In the PIEI mode, the spectra showed small molecular peaks, intense or base peaks due to M − CH 3NHCO + H and peaks at m z 58 due to CH 3NHCO. In the PICI mode, peaks due to M + H, M + C 2H 5, M − CH 3NHCO + 2H, CH 3NHCO( m z 58) and M-28 appeared. The cations at m z 58 found in both PIEI and PICI modes seem very useful for screening of a carbamate. In the NICI mode, the spectra showed peaks due to M − CH 3NHCO and characteristic anions appearing at mass numbers higher than molecular ones, which were probably due to dimerization of [M − CH 3NHCO] − followed by hydrogen attachment. Carbamates, which had been added to urine, plasma, whole blood, the liver, kidney and brain, could be rapidly isolated by use of Sep-Pak C 18 cartridges with chloroform as an elution solvent. They could be detected by wide-bore capillary gas chromatography with a SPB-5 column, with satisfactory separation from impurities in their underivatized forms.

Positive- and negative-ion mass spectrometry and rapid clean-up of 19 phenothiazines

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra of 19 phenothiazines are presented. In the PIEI mode, peaks due to M, M minus side chain (M − R 1), M − R 1 + H, and side chain itself (R 1) appeared for most compounds. The M − R 1 and R 1 ions were very useful for drug screening. In the PICI mode, most spectra showed base or intense peaks due to M + H, and small peaks due to M + C 2H 5; peaks due to M − R 1 + 2H and R 1 also appeared in many compounds. In the NICI mode, fragmentation modes were different in different compound groups; molecular or [M − H] − quasi-molecular anions appeared in many compounds with aliphatic side chains. Anions at m z 98 and 115 were characteristic for compounds with ( N-methylpiperazinyl)propyl side chains. Selected ion monitoring in the PIEI mode generally gave much higher sensitivity than in the PICI and NICI modes. Phenothiazines present in urine or plasma could be rapidly isolated by use of Sep-Pak C 18 cartridges. Thirteen of 19 phenothiazines could be detected by HP-17 wide-bore capillary gas chromatography with satisfactory separation from impurities in their underivatized forms.

Isolation and Recovery of Organophosphorus Pesticides from Water by Solid-Phase Extraction with Dual Wide-Bore Capillary Gas Chromatography

A systematic study that compares the recoveries of selected organophosphorus pesticides from spiked deionized water using octyl and octadecyl bonded silica sorbents (solid phase extraction, SPE) is reported. A packed column GC is converted to accept a dual wide-bore capillary configuration with chemically dissimilar liquid phases. One column leads to a thermionic detector while the other column leads to a flame photometric detector. The experimental design affords replicate injections and replicate extraction recovery data. Relative standard deviations are calculated that take into account propagation of error for i replicate injections on each of g SPEs performed. The polarity of the dialkyl phosphate ester moiety is correlated with the SPE extraction efficiency.