Gas Chromatography-nitrogen Phosphorus Detection Research Articles

Rapid detection of benzoylecgonine in vitreous humor by enzyme immunoassay.

The usual specimens submitted by a medical examiner for toxicological analysis include blood, urine, bile, vitreous humor, stomach contents, and solid-organ tissue. The detection of drugs in these specimens typically involves a combination of techniques including colorimetry, immunoassay, and gas chromatography. Although many laboratories rely principally on urine for the detection of drugs of abuse by immunoassay, these assays may be applied to other specimen types. An evaluation of Microgenics Corporation's cloned enzyme donor immunoassay (CEDIA) was conducted in order to evaluate its use in the detection of cocaine/cocaine metabolites in vitreous humor specimens. During a 14-month period, 392 vitreous humor specimens were analyzed by the CEDIA DAU Cocaine assay. Instrument parameters were set according to published manufacturer's guidelines. All presumptive positive immunoassay results prompted confirmatory testing and quantitation by gas chromatography-mass spectrometry (GC-MS) of other specimens including blood. Vitreous humor specimens were not tested by GC-MS. Using a approximately 100-ng/mL cutoff, the CEDIA assay produced 23 presumptive positive results, 22 of which were confirmed by GC-MS. The only specimen which could not be confirmed, elicited an immunoassay screen value near the cutoff limit. Routine analysis of blood, urine, bile, and/or bladder wash specimens by gas chromatography-nitrogen phosphorus detection revealed the presence of cocaine/cocaine metabolites in only 7 (31.8%) of the 22 confirmed cases. The concentration ranges of cocaine and benzoylecgonine in the blood specimens were none detected to 337 ng/mL and 17 to 8598 ng/mL, respectively. Cocaethylene was not detected in these cases. Analysis of vitreous humor specimens by CEDIA improved the detection rate of cocaine/cocaine metabolites by 0.7% in the cases submitted to our laboratory during the 14-month period.

Adsorption of metal–ethylenediaminetetraacetic acid chelates onto lake sediment

The adsorption of Ethylenediaminetetraacetic acid (EDTA) and its metal complexes, Cu, Fe(III), Hg, Mn and Ni, onto lake sediment was studied. The results reveal that EDTA and metal–EDTA complexes, even though being hydrophilic compounds, are indeed adsorbed within one months' contact time to some extent (6.3–24.8%). Less than 10% of Ni–EDTA, Cu–EDTA and EDTA salt was adsorbed, while the mass amount of Mn–EDTA, Hg–EDTA and Fe(III)–EDTA found in sediment exceeded 15% after the contact period. Thus, adsorption of metal–EDTA chelates might be a relevant process in their removal from the aquatic environment. The metal–EDTA chelates in aqueous and solid phases were determined by gas chromatography–nitrogen phosphorus detection (GC–NPD) system. The complexes were extracted by phosphate solution prior to analysis. The ability of EDTA to desorb adsorbed heavy metals from sediments is also discussed.

Simultaneous quantitation of ephedrines in urine by gas chromatography–nitrogen–phosphorus detection for doping control purposes

A gas chromatographic method for the simultaneous quantitation of ephedrine, pseudoephedrine, norephedrine (phenylpropanolamine), norpseudoephedrine (cathine) and methylephedrine in urine is described. The method consists of a liquid–liquid extraction with tert.-butyl methyl ether at pH 14. The extracts are analysed on a GC system equipped with an Rtx-5 Amine column and a nitrogen–phosphorus detector. Method validation shows excellent separation, linearity, specificity, accuracy, precision, intra-laboratory repeatability and reproducibility, making the method especially suitable for quantitation of ephedrines in urine samples for doping control purposes. A statistical analysis on the abuse of the different ephedrines in urine from athletes controlled in the Flemish doping control laboratory during the period 1993–2000 is included.

Improved solid-phase extraction method for systematic toxicological analysis in biological fluids.

A method for the simultaneous qualitative and quantitative determination of drugs of abuse (opiates, cocaine, or amphetamines) and prescribed drugs (tricyclic antidepressants, phenotiazines, benzodiazepines, etc.) in biological fluids--blood, urine, bile, and gastric contents--was developed. This procedure involves solid-phase extraction with Bond-Elut Certify columns followed by analysis by gas chromatography-nitrogen-phosphorus detection (GC-NPD) and confirmation by gas chromatography-mass spectrometry (GC-MS), after derivatization, when necessary. Pretreatment was performed on all samples: sonication for 15 min plus enzymatic hydrolysis with beta-glucuronidase in urine. With respect to the internal standards, nalorphine and trihexylamine were used for basic substances, allobarbital for acidic drugs, and prazepam for benzodiazepines. Acidic and basic compounds were extracted from different aliquots of samples at different pH levels: 6-6.5 for the acidic and neutral and 8-8.5 for the basic and the benzodiazepines. Several areas of experimental design were considered in the process of method optimization. These included internal standards, pH, sonication, flow rate and washing solvents. It was found that systematic analysis could be reliably performed using optimized extraction conditions. The recovery rates for the compounds tested were always higher than 61.02%.

Gas chromatography-mass spectrometry determination of phosphine residues in stored products and processed foods.

A gas chromatography-mass spectrometry (GC-MS) method was used for the quantitative confirmation of phosphine residues in stored products and processed foods. An established extraction technique was utilized for the preparation of headspace samples, which were analyzed by GC-MS and gas chromatography-nitrogen-phosphorus detection (GC-NPD). Wheat, oats, maize, white rice, brown rice, cornflakes, tortilla cornchips, groundnuts, and raisins were validated, showing excellent agreement between detectors when spiked at levels equivalent to 0.001 and 0.01 mg/kg phosphine and for samples containing incurred residues. The GC-MS method was reproducible and accurate when compared to the GC-NPD method and allowed five samples to be quantified in a working day. Subambient GC-MS oven temperatures were most suitable for phosphine residues ranging from 0.001 to 0.005 mg/kg, and a GC oven temperature of 100 degrees C was appropriate for residues >0.005 mg/kg. The method was sufficiently robust to be evaluated for other similar commodities as the need arises.

GC determination of nicotine in subcutaneous adipose tissue obtained by minimal trauma tissue biopsy

Nicotine has been analyzed by gas chromatography nitrogen-phosphorus detection in tissue samples obtained by repeated minimal trauma tissue biopsies from human subcutaneous adipose tissue. For sample preparation, a single extraction step of the tissue samples with chloroform was performed at 30–45°C. Calibration curves generated with spiked porcine subcutaneous adipose tissue were linear over a concentration range from 0.20 to 100 μg g−1, therefore, the limit of quantification was fixed at 0.20 μg g−1. The limit of detection was found to be 0.05 μg g−1 adipose tissue. The recovery of nicotinespiked porcine subcutaneous adipose tissue by chloroform extraction was 100±8%. The performance of the assay was not affected by the complex lipid matrix. The method was employed for analysis in a clinical study on nicotine penetration from a transdermal delivery system through the skin of moderate smokers.

Analysis of multiple pesticides in urban storm water using solid-phase extraction.

An analytical method was developed using C(18) solid-phase extraction and gas chromatography-nitrogen phosphorus detection (GC-NPD) to determine the presence and quantity of 12 contemporary pesticides in storm water runoff from an urban environment. The method was validated, using deionized water and water collected from a local pond, for two concentration levels and four holding time regimes. The method was then utilized in a study examining nonpoint source (NPS) pollution in Wichita, KS. Accuracy and precision were demonstrated in each test for each analyte except diazinon, which degraded rapidly during holding times in aqueous solution. For all matrices, concentration levels, and holding times, mean recoveries for the remaining 11 pesticides ranged from 50% to 105% with percent relative standard deviations less than 25%.

Analysis of cyclophosphamide and five metabolites from human plasma using liquid chromatography–mass spectrometry and gas chromatography–nitrogen–phosphorus detection

An assay method for the quantification of cyclophosphamide (CY) and five metabolites from human plasma is presented. The procedure is adapted to the chemical properties of the compounds of interest: non-polar compounds are extracted into methylene chloride, concentrated and analyzed by GC–NPD after derivatization, and the remaining aqueous fraction is deproteinated with acetonitrile–methanol prior to separation via reversed-phase HPLC and detection using atmospheric pressure ionization (API)-MS. Standard curves are linear over the required range and reproducible over five months. Plasma concentration–time profiles of CY and metabolites from a patient receiving CY by intravenous infusion (60 mg/kg, once a day for two days) are presented.

Zolpidem Distribution in Postmortem Cases

Zolpidem is the prototype of a class of sedative hypnotic drugs that are derivatives of imidazopyridine and is sold in the United States under the trade name Ambien. Over a four-year period, zolpidem was identified in eight cases investigated by the Office of the Chief Medical Examiner, State of Maryland. Zolpidem was identified by gas chromatography-nitrogen-phosphorus detection (GC-NPD) following an alkaline extraction and was confirmed by full-scan electron impact gas chromatography/mass spectrometry. Zolpidem was quantitated by GC-NPD in all specimens received. Five of the cases presented were deaths due to drug intoxication. In three of these cases, zolpidem was an incidental finding because the drug fatalities resulted from other drugs. In the other two cases of drug intoxication, zolpidem was present in elevated concentrations and was a contributing, but not exclusive cause of the drug intoxication. The remaining three cases were deaths that were not caused by drugs. The blood zolpidem concentrations in these cases were therapeutic (0.28, 0.12 and 0.19 mg/L, respectively). In six of the eight cases where both blood and urine were analyzed, the blood concentration was higher than the urine concentration. The distribution of zolpidem into the liver and kidney failed to identify any sequestration of the drug into either specimen.

Determination of very-long-chain fatty acids in serum by gas chromatography–nitrogen–phosphorus detection following cyanomethylation

A sensitive method for very-long-chain fatty acid analysis was developed by gas chromatography–nitrogen–phosphorus detection by using cyanomethyl derivatization. Bromoacetonitrile as alkylating reagent was used to improve nitrogen phosphorus detection detectability of compounds containing non-nitrogen. The carboxyl group of very-long-chain fatty acid was alkylated to cyanomethyl esters. Reaction conditions were 40 min at 60°C under potassium carbonate base. Heptacosanoic acid was used as an internal standard and hexane was used as a solvent of extraction. The extraction yield was 82.8% or more, relative standard deviation of the precision test was 8.3 % or more and the result of linearity test showed a good correlation coefficient of r 2=0.999 in the range of 0.1–50 μg/ml. The quantification limits were 10 ng/ml when 0.5 ml of serum was used. The present method proved simple, rapid, inexpensive and resistant to contaminants. When it was applied to serum samples taken from patients with X-linked adrenoleukodystrophy which is a hereditary X-linked disorder characterized by progressive demyelination and adrenal insufficiency during childhood, relative increase of the concentration of hexacosanoic acid and the concentration ratios of hexacosanoic, lignoceric to behenic acid was observed in comparison with control samples.

Polyamine profiles in the urine of patients with leukemia

Eleven urinary polyamine levels were determined in controls (32 cases) and 43 patients with varying stages of leukemia including initial, relapse and complete remission, using gas chromatography nitrogen–phosphorus detection. Also, to indirectly evaluate the possible involvement of enzymes, precursor to product concentration ratios were compared between controls and patients with each stage of leukemia. As a result, it is confirmed that the ratio of N 1-acSpd/ N 8-acSpd could be used as a diagnostic marker and the level of N 1, N 12-diacetylspermine could be used for determining disease stage and as a malignancy marker for leukemia. An altered metabolic pathway related to leukemia is also proposed in which N 1, N 12-diacetylspermine can be produced directly from spermine and N 1, N 12-diacetylspermine is a major source of N 1-acetylspermidine.

Effect of the various parameters governing solid-phase microextraction for the trace-determination of pesticides in water

The parameters governing solid-phase microextraction (SPME) are investigated, with emphasis on the determination of the partition coefficients, K, and their use to predict the selection of a fibre, depending on the respective characteristics of the fibres and the analytes. Film thickness and stability of the compounds can interfere with the determination of K values. The time profile curves were determined for twelve pesticides having a wide range of water solubilities and polarities and using four fibres (polydimethylsiloxane, polydimethylsiloxane–divinylbenzene, Carbowax–divinylbenzene and polyacrylate). Although the affinity order was different for the four coatings, no correlation was found between the respective characteristics of the fibres and solutes. The two fibres containing divinylbenzene were shown to have the highest affinities and the polydimethylsiloxane had the lowest affinity. The polyacrylate fibre which is the more polar commercial fibre did not provide the highest affinities for the more polar and water-soluble analytes. The important parameters for quantitative analysis have been evaluated. The calibration curves were similar when one analyte of interest was present on its own in a drinking water sample, or when eleven other pesticides were present at the same concentration or when much higher concentrations of other analytes were present in the sample. Linearity was obtained over a wide range of concentrations in drinking water samples. Detection limits are in agreement with European regulatory levels in drinking water for most of the analytes using solid-phase microextraction–gas chromatography–nitrogen–phosphorus detection (SPME–GC–NPD). In contaminated surface water samples, the chromatograms are relatively clean and most of the compounds can be detected at levels lower than 0.5 μg/l.

An improved method for the measurement of lidocaine and its metabolites in rat plasma.

An improved method is described for the quantitation of lidocaine and its dominant metabolites in rat plasma, 3-hydroxy-lidocaine glucuronide and 3-hydroxy-MEG-X glucuronide. Frozen plasma samples (100-200 microliters) were thawed and deproteinated by precipitation with acetonitrile, before the conversion of glucuronidates into their respective hydroxylated forms by acid hydrolysis. After extraction with solid-phase C18 cartridge chromatography, the metabolites and parent drug were analyzed by capillary gas chromatography-nitrogen phosphorus detection, without derivativization. A detection limit of 0.005 microgram/ml for lidocaine and nonglucuronidated metabolites and 0.01 microgram/ml for glucuronidated metabolites was achieved. The method offers significant improvements in sensitivity relative to existing techniques, which should be of specific benefit to studies in which sample volume is limited, such as those concerned with the pharmacokinetics of lidocaine metabolism in small-animal pain state models.

Pilot Survey for Atrazine and Total Chlorotriazines in Estuarine Waters Using Magnetic Particle-Based Immunoassay and Gas Chromatography-Nitrogen/Phosphorus Detection

The determination of atrazine in estuarine waters in the presence of the common cross-reactants deethylatrazine, deisopropylatrazine, and simazine has been investigated using direct rapid pesticide immunodetection (RaPID) magnetic particle-based solid-phase ELISA. Different parameters such as least detectable dose, 50% inhibition concentration, and percentage of cross-reactivity, determined by estimating the amount of compound required to displace 50% of the enzyme conjugate to the amount of atrazine, were calculated. Estuarine water samples containing various chlorotriazine herbicides from a pilot monitoring program (with levels varying from 0.008 to 0.326 μg/L) were compared by using the RaPID assay and gas chromatography-nitrogen/phosphorus detection (GC-NPD). Both analytical methods showed good correlation for atrazine and total chlorotriazines for most of the estuarine water samples analyzed. Gas chromatography/mass spectrometry (GC/MS) was used for confirmation purposes, and false positives were detected.

Rapid magnetic particle-based ELISA assay compared with gas chromatography-nitrogen phosphorus detection for determining atrazine in freeze-dried water samples

The determination of atrazine in freeze-dried water samples containing simazine, 0.6% glycine as stabilizer and other pesticides has been compared using three different techniques: (i) direct rapid-magnetic particlebased ELISA, (ii) dichloromethane liquid-liquid extraction (LLE) and Florisil column clean-up prior to ELISA determination and (iii) LLE, Florisil column clean-up and gas chroamtography with nitrogen phosphorus detection (GC-NPD). The methodology developed in this paper has shown the advantages of the introduction of a clean-up step prior to ELISA determination and its correlation with GC-NPD determinations. Atrazine could be determined at levels between 0.1 to 5 μg l−1 in water smaples using the different methods described in this paper. The crossreactivity problems found in the ELISA test associated with the presence of simazine are also discussed.

Comparison of supercritical fluid extraction and liquid-liquid extraction for isolation of selected pesticides stored in freeze-dried water samples

The stability of freeze-dried water samples spiked with eight agrochemicals (atrazine, simazine, linuron, carbaryl, propanil, fenitrothion, parathion and fenamiphos) were examined to evaluate their suitability as candidate reference materials for their determination in water samples. In addition, two different extraction procedures, liquid-liquid and supercritical fluid extraction, were compared for the isolation and trace enrichment of target analytes from freeze-dried water samples. Final analytical determinations were by gas chromatography-nitrogen phosphorus detection and electronic impact mass spectrometry, and by liquid chromatography-diode array detection. The whole methodology developed in this paper permitted the determination of pesticides spiked in water at levels varying from 0.03 to 6.9 μg L−1.

Determination of succinonitrile in horse urine by gas chromatography-nitrogen-phosphorus detector and gas chromatography-mass spectrometry.

A chromatographic method was developed to detect and confirm the presence of succinonitrile (SDN) in horse urine samples, for antidoping control. The urine samples (5 ml) were extracted with diethyl ether and screened by gas chromatography-nitrogen-phosphorus detector and the confirmation of the drug's presence was accomplished by using gas chromatography-mass selective detection. The recovery of extraction was 78 and 81% for 1.0 and 2.0 micrograms ml-1 (relative standard deviation, < 10%), respectively. Urine samples collected after the administration of Energisan were positive for SDN (1-30 h) in all samples analysed.

Environmental degradation of atrazine, linuron and fenitrothion in soil samples

The persistence of atrazine, linuron and fenitrothion in soil samples from an estuarine area (Ebro delta, Tarragona, Spain) has been studied. Soil samples from the top surface (10 cm) were collected during 1989–91, freeze‐dried, sieved through 200 μm, Soxhlet extracted with methanol, cleaned‐up with Florisil and analysed either by gas chromatography‐nitrogen phosphorus detection (GC‐NPD), in the case of atrazine and fenitrothion, or by liquid chromatography with diode array detection (LC‐DAD), for linuron. Confirmation of the samples analysed by GC‐NPD was carried out using GC‐mass spectrometric detection (MS) in the electron impact mode. The soil half lives obtained under the real environmental conditions have been calculated and the values obtained have been correlated with the physicochemical properties of each pesticide and the soil type. Degradation was affected by volatilization since temperatures in the area of study are relatively high, ca. 30°C, in the summer period. In the case of atrazine it ha...

Determination of metrifonate and dichlorvos in whole blood using gas chromatography and gas chromatography—mass spectrometry

Analytical methods for determining metrifonate and dichlorvos in whole blood and a sampling procedure suitable for pharmacokinetic studies in man are described. Metrifonate concentrations were determined after chloroform extraction using gas chromatography—nitrogen—phosphorus detection. The within-assay coefficients of variation were 4 and 9% at 19.4 and 0.8 μmol/l (limits of determination), respectively. Dichlorvos was determined using gas chromatography—mass spectrometry of toluene extracts. The within-assay coefficients of variation were 2 and 5% at 225 and 50 nmol/l (limits of determination), respectively. Since both substances are chemically unstable, the blood was collected by dripping it directly from the vein into 0.74 M phosphoric acid.

Rapid confirmation of enzyme-multiplied immunoassay test (EMIT) for phencyclidine-positive urine samples with capillary gas chromatography—nitrogen—phosphorus detection

Rapid confirmation of enzyme-multiplied immunoassay test (EMIT) for phencyclidine-positive urine samples with capillary gas chromatography—nitrogen—phosphorus detection