A fast gas chromatography/mass spectrometry method for the determination of stimulants and narcotics in urine

A fast method has been developed for the simultaneous determination of 52 stimulants and narcotics excreted unconjugated in urine by gas chromatography/mass spectrometry (GC/MS). The procedure involves the liquid/liquid extraction of the analytes from urine at strong alkaline pH and the injection of the extract into a GC/MS instrument with a fast GC column (10 m × 0.18 mm i.d.); the short column allows the complete separation of the 52 analytes in a chromatographic run of 8 min. The method has been fully validated giving lower limits of detection (LLODs) satisfactory for its application to antidoping analysis as well as to forensic toxicology. The repeatability of the concentrations and the retention times are good both for intra‐ and for inter‐day experiments (%CV of concentrations always lower than 15 and %CV of retention times lower than 0.6). In addition, the analytical bias is satisfactory (A% always >15%). The method proposed here would be particularly useful whenever there are time constraints and the analyses have to be completed in the shortest possible time. Copyright © 2010 John Wiley & Sons, Ltd.     

Stable isotope dilution method for the determination of guanidinoacetic acid by gas chromatography/mass spectrometry

For more than 30 years, guanidinoacetic acid (GAA), together with other guanidino compounds, has been proposed as an important marker for renal failure, in kidney transplantation, and for renal metabolism, especially for the metabolic activity of the renal proximal tubules. Since the discovery of the first patient with guanidinoacetic acid methyltransferase deficiency in 1994 by St?ckler et al. (Pediatr. Res. 1994; 36: 409), GAA has become of great interest for all laboratories involved in the diagnosis of metabolic diseases. In the literature there are several methods described for the determination of GAA, ranging from ion-exchange chromatography with post-column derivatisation, enzymatic methods, gas chromatography/mass spectrometry (GC/MS), to liquid chromatography/atmospheric pressure chemical ionisation mass spectrometry (LC/APCI-MS). Here a stable isotope dilution method for quantitative and accurate determination of GAA in urine, plasma, and cerebrospinal fluid is described. GAA is converted to the bis(trifluoromethyl)pyrimidine di(tert-butyldimethylsilyl) derivative by stepwise derivatisation with hexafluoroacetylacetone and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA). Analysis can be performed using a standard benchtop GC/MS system. For quantitative GAA determination with 1,2-(13)C-GAA as internal standard, selected ion monitoring is performed using m/z 460/462, with m/z 432/433 and 375/376 as qualifiers.     

A fully validated method for the determination of vardenafil in blood using gas chromatography/mass spectrometry

Vardenafil (VDN) is one of the three commercially available phosphodiesterase type 5 inhibitors and it is mainly used in the treatment of erectile dysfunction. A sensitive and specific gas chromatography/mass spectrometry (GC/MS) method for the determination of VDN in blood has been developed and validated. Sample preparation included solid-phase extraction and derivatization with N-methyl-N-tert-butyldimethylsilyl-trifluoroacetamide (MTBSTFA) and 1% tert-butyldimethylsilylchloride (TBDMSCl). Protriptyline was used as the internal standard for this assay. Limits of detection and quantification for VDN were 0.70 and 2.00 μg/l, respectively. The calibration curves were linear within the dynamic range 2.00-200.0 μg/l with a correlation coefficient higher than 0.991. Absolute recovery ranged from 88.6% to 95.7% for the analyte of interest at three quality control levels. Intra- and inter-day accuracy was found to be between - 6.1% to 10.8% and - 9.3% to 11.6%, respectively, whereas intra- and inter-day precision was < 7.8% and 9.7%, correspondingly. The proposed method is the first fully validated GC/MS method for the determination of VDN in blood samples and it can be used in routine every day analysis by clinical and forensic laboratories for pharmacokinetic studies, for therapeutic drug level monitoring or for the investigation of related forensic cases. A few blood samples analyzed using the developed method is reported herein to demonstrate the suitability of the method.     

Improved gas chromatographic method for the determination of nicotine and cotinine in biologic fluids

Improved methods have been developed for the determination of nicotine and its major metabolite, cotinine, in blood, plasma, and urine samples. These methods utilize gas chromatography with alkali flame ionization (nitrogen--phosphorus) detection and structural analogs of nicotine and cotinine as internal standards.     

溶剂转移-气相色谱-质谱法和选择洗脱-气相色谱法测定大蒜中289种农药多残留

以溶剂转移净化为核心步骤,建立了一种适用于大蒜样品中农药多残留分析的前处理方法(方法I),配以一个辅助方法(方法II),构成大蒜中常见289种农药多残留的分析体系(方法I283种,方法II6种)。方法I中,样品用乙腈-水溶液提取,盐析分配,溶剂转移和固相萃取(SPE)净化后进行气相色谱-质谱(GC-MS)分析;方法II中,样品用无水Na2SO4配合乙酸乙酯均质研磨,超声波辅助提取,提取液经Primary Secondary Amine (PSA)粉末分散固相萃取和LC-Si柱选择洗脱净化后进行GC分析。GC-MS采用选择离子监测(SIM)方式,GC采用火焰光度检测器(FPD)检测,外标法定量。方法简便、快速,通过优化前处理和上机条件,在最优条件下进行测试,方法的定量限(S/N≥10)为0.01～0.05 mg/kg。方法I中,在加标水平为0.02、0.20 mg/kg时,回收率为52%～163%,其中回收率在70%～120%之间的占88%,相对标准偏差为2.4%～18%;方法II中,在加标水平为0.01、0.02、0.10、0.20 mg/kg时,回收率为70%～111%,相对标准偏差为3.2%～9.3%。详细描述了实验模型的构建,并对GC-MS灵敏度的提高提出了新的见解。该方法准确、灵敏、快速,可满足大蒜中多种农药残留的检测要求。     

Mixed-mode solid-phase extraction followed by acetylation and gas chromatography mass spectrometry for the reliable determination of trans-resveratrol in wine samples

This work presents an advantageous analytical procedure for the accurate determination of free trans-resveratrol in red and white wines. The proposed method involves solid-phase extraction (SPE), acetylation of the analyte in aqueous media and further determination by gas chromatography (GC) with mass spectrometry detection (MS). The use of a mixed-mode SPE sorbent provides an improvement in the selectivity of the extraction step; moreover, the presence of several intense ions in the electron impact mass spectra of its acetyl derivative guarantees the unambiguous identification of trans-resveratrol. Considering a sample intake of 10 mL, the method provides a limit of quantification (LOQ) of 0.8 ng mL⁻¹ and linear responses for concentrations up to 2.5 μg mL⁻¹, referred to wine samples. The average recovery, estimated with samples fortified at different concentrations in the above range, was 99.6% and the inter-day precision stayed below 8%. Trans-resveratrol levels in the analyzed wines varied from 3.4 to 1810 ng mL⁻¹. Cis-resveratrol was also found in all samples. In most cases, equal or higher responses were measured for this latter form than for the trans-isomer. The reduced form of resveratrol, dihydro-resveratrol, was systematically identified in red wines.     

A multi-residue method for the determination of 203 pesticides in rice paddies using gas chromatography/mass spectrometry

This work reports a rapid, specific and sensitive multi-residue method based on the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method and gas chromatography with mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM) using one quantification ion and two identification ions for the routine analysis of 203 pesticides in rice paddies. Analyses of fortified rice paddy samples were performed at different levels (0.05, 0.20 and 0.50 mg kg⁻¹). Mean recoveries from five replicates ranged from 75% to 115%, with coefficients of variation lower than 17%. The limit of quantification was in the range of 0.002-0.05 mg kg⁻¹ for the pesticides. 1040 rice paddy samples were analyzed for method application.     

Isotope dilution gas chromatography/mass spectrometry method for determination of pyrethroids in apple juice

This paper presents the development of a highly precise and accurate analytical method for the determination of three matrix-bound pyrethroids, namely, cypermethrin, permethrin, and bifenthrin, using an isotope dilution gas chromatography/mass spectrometry technique. Identification of the analytes was confirmed under selective ion monitoring mode by the presence of two dominant ion fragments within specific time windows and matching of relative ion intensities of the ions concerned in samples and calibration standards. Quantitation was based on the measurement of concentration ratios of the natural and isotope analogues in the sample and calibration blends. Intraday and interday repeatabilities of replicate analyses of the pyethroids in an apple juice sample were below 0.5%. The expanded relative uncertainty ranged from 3 to 6%, which was significantly lower than the range obtained using internal or external calibration methods. As a labeled analogue is not available for bifenthrin, bifenthrin was determined using labeled cis-permethrin as the internal standard. The results were counterchecked by a gas chromatography-electron capture detection technique using PCB 209 as the internal standard. The method developed was applied to a recent pilot study organized by CCQM and the results were consistent with those of other participants.     

Simultaneous determination of nicotine and cotinine in plasma by capillary gas liquid chromatography with nitrogen-sensitive detection

Conclusion By the use of structural analogues of nicotine and cotinine as internal standards, the elimination of environmental sources of contamination and an exact clean-up procedure, we were able to develop a rapid and sensitive method which has acceptable accuracy and precision over the concentration range necessary in pharmacokinetic studies.

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Gleichzeitige Bestimmung von Nicotin und Cotinin in Plasma mit Hilfe der Capillar-Gas-Chromatographie

     

A simple, rapid and sensitive method for determination of aldehydes in human blood by gas chromatography/mass spectrometry and solid-phase microextraction with on-fiber derivatization

Aldehydes are considered potential markers for enhanced oxidative stress and have been proposed as a diagnostic measure of cancer status. Do to their volatility and activity, it is very difficult to accurately measure aldehydes in human blood. In the present work, gas chromatography/mass spectrometry (GC/MS) and solid-phase microextraction (SPME) with on-fiber derivatization was developed for determination of aldehydes in human blood. O-(2,3,4,5,6-Pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) in aqueous solution was first adsorbed by a SPME fiber, and then the aldehydes in blood samples were headspace extracted by the SPME fiber and rapidly derivatized with PFBHA on the SPME fiber. Finally, the oximes formed were desorbed and detected by GC/MS in electron ionization (EI) mode. Validation of the present method was carried out, and the method was applied to quantitative analysis of the aldehydes in lung cancer blood. The results demonstrated that GC/MS and SPME with on-fiber derivatization is a simple, rapid, sensitive and solvent-free method for the determination of aldehydes in human blood.     

Screening method for pesticides in air by gas chromatography/tandem mass spectrometry

A multiresidue method for determining more than 70 pesticides in air has been validated using a single injection with gas chromatography/tandem mass spectrometry (GC/MS/MS). The method validation considered both stages of sampling and analysis. The sampling method, based on active sampling using sorption in sorbent cartidges, was validated by generating standard atmospheres. Performance parameters of the method were evaluated, with a reduction in the limits of quantification by injecting a higher volume of sample extract, and increase of selectivity by the use of MS/MS detection mode. The method was based on solid-phase extraction, which permits a degree of automation. The best adsorbents were found to be Chromosorb 106 and Tenax TA. The retention capacity of these sampling sorbents allows up to 1440 L of air to be sampled without any breakthrough for most of the compounds. Data were generated for assessing the potential exposure of bystanders. The application of the method to the analysis of the air in urban locations near agricultural areas showed that pesticides were present in most of the samples.     

The determination of nicotine and cotinine by ion pair reversed-phase chromatography

An ion chromatographic method is described for the determination of nicotine and cotinine in aqueous solutions. This method is based on a type of reversed-phase chromatography involving ion pair formation of protonated nicotine, cotinine, pyridine, and pyridine derivatives. Detection is accomplished by measuring the UV absorption at 262 nm. Detection limits for nicotine and cotinine are 8 ng/mL and 2 ng/mL, respectively. Analyses of environmental samples and spiked environmental samples by both this ion chromatographic method and a previously reported gas chromatographic method have been used to demonstrate the accuracy and precision of this technique. The results of the analyses of both sets of samples by the two methods are in excellent agreement with a linear correlation coefficient of 0.97.     

A single glucose derivative suitable for gas chromatography/mass spectrometry and gas chromatography/combustion/isotope ratio mass spectrometry

The incorporation of stable isotopes improves the assessment of glucose metabolism and, with some researchers using two tracers, (2)H-glucose assessed by gas chromatography/mass spectrometry (GC/MS) and (13)C-glucose by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), a common derivative for both is advantageous. The most commonly used derivatives for GC/MS are inappropriate for GC/C/IRMS as additional functional groups dilute the label. We therefore considered the suitability of six derivatives for both GC/MS and GC/C/IRMS. Glucose alkylboronates were prepared by adding the appropriate alkylboronic acid (butyl- or methylboronic acid) in pyridine to desiccated glucose. The derivatisation was completed by reacting this with either (a) acetic anhydride or trifluoroacetic anhydride (acetate derivatives) or (b) bis(trimethylsilyl)trifluoroacetamide BSTFA (TMS derivatives). All six derivatives were assessed using GC/MS and (13)C GC/C/IRMS.Neither TMS derivative exhibited any signal intensity in the molecular ion, although a M-15 ion showed good agreement between experimental and theoretical data and, whilst still low in intensity, could be suitable for isotope work. Similarly, none of the acetate derivatives showed any intensity at the molecular ion although three key fragmentation series were identified. The most attractive sequence, initiated by the loss of 1,2 cyclic boronate, resulted in the main fragment ion of interest, m/z 240, corresponding to the fluorinated methylboronate derivate. Minimal carbon and hydrogen atoms are added to this derivative making it an excellent choice for stable isotope work, while proving suitable for analysis by both GC/MS and GC/C/IRMS.     

A multiresidue method for the determination 234 pesticides in Korean herbs using gas chromatography mass spectrometry

A rapid, specific and sensitive multiresidue method based on dispersive solid phase extraction sample preparation and gas chromatography with the mass spectrometric detection for the analysis of 234 pesticides in Korean herbs (Acanthopanax senticosus, Morus alba L., Hovenia dulcis) has been developed. Method recoveries were found to be between 62 and 119% with relative standard deviation lower than 21% for all compounds in the concentration range of 0.05 to 0.400 mg kg^? 1. Limits of quantification of most compounds are below 0.050 mg kg^? 1. The data demonstrate that this method was successfully used for analysis of 234 pesticides in Korean herbs.     

Isotope dilution gas chromatography/mass spectrometry for platinum determination in urine

The therapeutic importance of platinum (Pt) compounds, the growing accessibility of gas chromatography/mass spectrometry (GC/MS) systems in clinical laboratories, and the lack of a mass spectrometric method for the determination of Pt in biological samples motivated us to develop an isotope dilution GC/MS assay for Pt. The method is based on the use of lithium bis(trifluoroethyl) dithiocarbamate, Li(FDEDTC), as a chelating agent and enriched ¹⁹²Pt for isotope dilution. Conditions were optimized for the precise and accurate determination of isotope ratios of Pt by using a 10-m DB-l fused silica capillary column and a reverse-geometry double-focusing mass spectrometer with selected ion monitoring. An overall precision of 1% was obtained by combining within-run precision and between-run precision at the 10-ng level. No appreciable memory effect was observed when samples with different isotope ratios were analyzed sequentially. The method was validated by the quantitation of Pt in National Institute of Standards and Technology freeze-dried urine sample SRM 2670. A concentration value of 125 ± 6 /Lg/L (n = 6) was obtained by using four different sets of isotope ratios in the molecular ion and supports the National Institute of Standards and Technology recommended value of 120 ± ? μg/L. Limits-of-quantitation, estimated at 3 μg/L, are made possible by the high sensitivity of the method and the low blank value for Pt.     

Simultaneous determination of amphetamines and ketamines in urine by gas chromatography/mass spectrometry

A method for the simultaneous determination of amphetamines and ketamines (ketamine, norketamine and dehydronorketamine) in urine samples by gas chromatography/mass spectrometry was developed and validated. Urine samples were extracted with organic solvent and derivatized with trifluoroacetic anhydride (TFAA). The limits of detection and limits of quantification for each analyte were lower than 19 and 30 ng/mL, respectively. Within-day and between-day precisions were within 0.5% and 10.6%, respectively. Biases for three levels of control samples were within -10.6% and +7.8%. The concentration of dehydronorketamine was greater than those of ketamine or norketamine in 19 of 35 ketamine-positive samples. A group of 110 human urine samples previously determined to contain at least one of the target analytes was analyzed using the new method, and excellent agreement was observed with previous results.