Sensitive Gas Chromatography-mass Spectrometry Method Research Articles

A SIMPLE SENSITIVE AND RAPID GAS CHROMATOGRAPHY METHOD FOR DETECTION AND QUANTIZATION OF METFORMIN IN METFORMIN TABLET FORMULATION, BY DIRECT INJECTION, USING MASS DETECTOR

Metformin (1, 1- dimethyl biguanide) represents the “gold standard” for the treatment of diabetes mellitus type 2. Despite its important role in reducing mortality and morbidity in the diabetic population, metformin is associated with an increased risk of stroke. A simple, novel, specific, and sensitive gas chromatography-mass spectrometry method (GC-MS) for the determination of metformin was developed. Several parameters such as reaction time and temperature were optimized. There was no interfering peak from the blank at the retention time of metformin. Linearity was demonstrated over the concentration range of 4.024–24.144ppm with a coefficient of determination (R2) above 0.9999. Accuracy and precision were within acceptable limits. The method was fully validated using parameters such as specificity, linearity, limits of detection and quantification, precision, accuracy, recovery, range, robustness, and ruggedness. The developed method was successfully applied for the identification and quantification of metformin in the market tablet formulation.

HPLC-UV and GC-MS Methods for Determination of Chlorambucil and Valproic Acid in Plasma for Further Exploring a New Combined Therapy of Chronic Lymphocytic Leukemia.

High performance liquid chromatography with ultra-violet detection (HPLC-UV) and gas chromatography–mass spectrometry (GC-MS) methods were developed and validated for the determination of chlorambucil (CLB) and valproic acid (VPA) in plasma, as a part of experiments on their anticancer activity in chronic lymphocytic leukemia (CLL). CLB was extracted from 250 µL of plasma with methanol, using simple protein precipitation and filtration. Chromatography was carried out on a LiChrospher 100 RP-18 end-capped column using a mobile phase consisting of acetonitrile, water and formic acid, and detection at 258 nm. The lowest limit of detection LLOQ was found to be 0.075 μg/mL, showing sufficient sensitivity in relation to therapeutic concentrations of CLB in plasma. The accuracy was from 94.13% to 101.12%, while the intra- and inter-batch precision was ≤9.46%. For quantitation of VPA, a sensitive GC-MS method was developed involving simple pre-column esterification with methanol and extraction with hexane. Chromatography was achieved on an HP-5MSUI column and monitored by MS with an electron impact ionization and selective ion monitoring mode. Using 250 µL of plasma, the LLOQ was found to be 0.075 μg/mL. The accuracy was from 94.96% to 109.12%, while the intra- and inter-batch precision was ≤6.69%. Thus, both methods fulfilled the requirements of FDA guidelines for the determination of drugs in biological materials.

Development of a highly sensitive gas chromatography-mass spectrometry method preceded by solid-phase microextraction for the analysis of propofol in low-volume cerebral microdialysate samples.

To date, the commonly used intravenous anesthetic propofol has been widely studied, and fundamental pharmacodynamic and pharmacokinetic characteristics of the drug are known. However, propofol has not yet been quantified in vivo in the target organ, the human brain. Here, cerebral microdialysis offers the unique opportunity to sample propofol in the living human organism. Therefore, a highly sensitive analytical method for propofol quantitation in small sample volumes of 30 μL, based on direct immersion solid‐phase microextraction was developed. Preconcentration was followed by gas chromatographic separation and mass spectrometric detection of the compound. This optimized method provided a linear range between the lower limit of detection (50 ng/L) and 200 μg/L. Matrix‐matched calibration was used to compensate recovery issues. A precision of 2.7% relative standard deviation between five consecutive measurements and an interday precision of 6.4% relative standard deviation could be achieved. Furthermore, the permeability of propofol through a cerebral microdialysate system was tested. In summary, the developed method to analyze cerebral microdialysate samples, allows the in vivo quantitation of propofol in the living human brain. Additionally the calculation of extracellular fluid levels is enabled since the recovery of the cerebral microdialysis regarding propofol was determined.

Pharmacokinetics of meperidine (pethidine) in rabbit oral fluid: correlation with plasma concentrations after controlled administration.

Oral fluid assays for quantifying drugs are useful in forensic toxicology and drug monitoring. Compared with blood and urine specimens, oral fluid collection is simple, non-invasive, and more difficult to adulterate. Therefore, we investigated whether meperidine and its metabolites could be detected in oral fluid and whether there was a predictable relationship between oral fluid and plasma concentrations. Male New Zealand white rabbits (n = 10) were administered meperidine hydrochloride (20 mg/kg, intravenous). Then, plasma and oral fluid were collected at various time points up to 10 h after administration. We developed a simple and sensitive gas chromatography-mass spectrometry method for the determination of meperidine and normeperidine in oral fluid and plasma. We estimated the apparent pharmacokinetic parameters for meperidine in oral fluid and plasma and determined the ratio and correlation between oral fluid and plasma concentrations. The results demonstrate that this method has excellent specificity, linearity, precision, and recovery. Meperidine and normeperidine were detected in both body fluids; meperidine was the most abundant analyte in oral fluid. The oral fluid-to-plasma drug concentration ratios did not differ significantly over time (p > 0.05). In addition, oral fluid and plasma levels of meperidine and normeperidine were significantly correlated over time (r = 0.713 and 0.725, respectively; p < 0.05). These results provide context for interpreting meperidine and metabolite concentrations in oral fluid and support the utility of oral fluid as an alternative matrix in clinical and forensic testing.

Determination of Pyrrolizidine Alkaloids in Honey with Sensitive Gas Chromatography-Mass Spectrometry Method

Pyrrolizidine alkaloids (PAs) are secondary metabolites produced by plants as a chemical defense against herbivores. Plants containing PAs are widely distributed in almost all geographical regions posing a risk of honey contamination. To provide safety of honey and decrease the potential risk for the consumers, a sensitive method based on gas chromatography-mass spectrometry enabling determination of a content of 1,2-unsaturated PAs in honey was developed. Honey samples were purified on MCX cartridges, and PAs were eluted with a solvent mixture consisting of ethyl acetate, methanol, ammonia, and triethylamine. Subsequently, 1,2-unsaturated alkaloids were reduced to their common backbone structures and derivatized with heptafluorobutyric anhydride. The method was validated according to SANTE 2015. All received parameters are in consistence with the document requirements as recovery ranged from 73.1 to 93.6%. The repeatability and reproducibility were calculated as relative standard deviation and ranged from 3.9 to 8.6% and from 10.6 to 17.8%, respectively. The limit of quantification was determined as 1 μg kg−1. Good linearity of the method was obtained with the coefficient of determination R2 > 0.99. The method was applied to 40 Polish and 14 Asian honey sample analyses.

A simple, selective, and sensitive gas chromatography-mass spectrometry method for the analysis of five process-related impurities in atenolol bulk drug and capsule formulations.

An extremely sensitive and simple gas chromatography with mass spectrometry method was developed and completely validated for the analysis of five process-related impurities, viz., 4-hydroxy-l-phenylglycine, 4-hydroxyphenylacetonitrile, 4-hydroxyphenylacetic acid, methyl-4-hydroxyphenylacetate, and 2-[4-{(2RS)-2-hydroxy-3-[(1-methylethyl)amino]propoxy}phenyl]acetonitrile, in atenolol. The separation of impurities was accomplished on a BPX-5 column with dimensions of 50m×0.25mm i.d. and 0.25μm film thickness. The method validation was performed following International Conference on Harmonisation guidelines in which the method was capable to quantitate 4-hydroxy-l-phenylglycine, 4-hydroxyphenylacetonitrile, and 4-hydroxyphenylacetic acid at 0.3ppm, and methyl-4-hydroxyphenylacetate and 2-[4-{(2RS)-2-hydroxy-3-[(1-methylethyl)amino]propoxy}phenyl]acetonitrile at 0.35ppm with respect to 10mg/mL of atenolol. The method was linear over the concentration range of 0.3-10ppm for 4-hydroxy-l-phenylglycine, 4-hydroxyphenylacetonitrile, and 4-hydroxyphenylacetic acid, and 0.35-10ppm for methyl-4-hydroxyphenylacetate and 2-[4-{(2RS)-2-hydroxy-3-[(1-methylethyl)amino]propoxy}phenyl]acetonitrile. The correlation coefficient in each case was found ≥0.998. The repeatability and recovery values were acceptable, and found between 89.38% and 105.60% for all five impurities under optimized operating conditions. The method developed here is simple, selective, and sensitive with apparently better resolution than the reported methods. Hence, the method is a straightforward and good quality control tool for the quantitation of selected impurities at trace concentrations in atenolol.

Quantification of furandiones in ambient aerosol

Furandiones are products of the photooxidation of anthropogenic volatile organic compounds (VOC), like toluene, and contribute to secondary organic aerosol (SOA). Because few molecular tracers of anthropogenic SOA are used to assess this source in ambient aerosol, developing a quantification method for furandiones holds a great importance. In this study, we developed a direct and highly sensitive gas chromatography-mass spectrometry method for the quantitative analysis of furandiones in fine particulate matter that is mainly free from interference by structurally-related dicarboxylic acids. Our application of this method in Iowa City, IA provides the first ambient measurements of four furandiones: 2,5-furandione, 3-methyl-2,5-furandione, dihydro-2,5-furandione, and dihydro-3-methyl-2,5-furandione. Furandiones were detected in all collected samples with a daily average concentration of 9.1 ± 3.8 ng m−3. The developed method allows for the accurate measurement of the furandiones concentrations in ambient aerosol, which will support future evaluation of these compounds as tracers for anthropogenic SOA and assessment of their potential health impacts.

Determination of diclofenac concentrations in human plasma using a sensitive gas chromatography mass spectrometry method.

BackgroundA gas chromatography mass spectrometry (GCMS) method for the determination of diclofenac in human plasma has been developed and validated.ResultsThis method utilizes hexane which is a relatively less toxic extraction solvent compared to heptane and benzene. In addition, phosphoric acid and acetone were added to the samples as deproteination agents, which increased the recovery of diclofenac. These revised processes allow clean extraction and near-quantitative recovery of analyte (approx. 89–95 %). Separation was achieved on a BP-1 column with helium as carrier gas. The molecular ion peaks of the indolinone derivatives of diclofenac ion (m/z 277) and the internal standard, 4-hydroxydiclofenac ion (m/z 439) were monitored by a mass-selective detector using selected ion monitoring (SIM) mode. The linear range for the newly developed and highly sensitive assay was between 0.25–50 ng/mL. The detection and lower quantifiable limits were 0.125 and 0.25 ng/mL, respectively. The inter-day and intra-day coefficients of variation for high, medium and low quality control concentrations were less than 9 %. The robustness and efficacy of this sensitive GCMS method was further demonstrated by using it for a pharmacokinetic study of an oral dosage form of diclofenac, 100 mg of modified-release capsules (Rhumalgan XL), in human plasma.ConclusionsThis method is rapid, sensitive, specific, reproducible and robust, and offers improved sensitivity over previous methods. This method has considerable potential to be used for detailed pharmacokinetics, pharmacodynamics and bioequivalence studies of diclofenac in humans.

A salting out-acetonitrile homogeneous extraction coupled with gas chromatography–mass spectrometry method for the simultaneous determination of thirteen N-nitrosamines in skin care cosmetics

A sensitive gas chromatography–mass spectrometry method was established for the simultaneous determination of thirteen N-nitrosamines (NAs) in skin care cosmetics. The cosmetics samples were firstly dispersed by water and subsequently extracted and purified using salting out-acetonitrile homogeneous extraction method. Finally, the extracting solution was concentrated by slow nitrogen gas blowing. All of the samples were separated by INNOWAX capillary chromatographic column, and detected by selected ion monitoring (SIM) mode of gas chromatography–mass spectrometry (GC–MS) and quantified by isotope internal standard method. The method was validated for linearity and range, accuracy, precision and sensitivity. Under the optimized condition, the calibration curves were linear over the selected concentration ranges of 2–500μg/L for all the thirteen analytes, with calculated coefficients of determination (R2) of greater than 0.996. The limits of detection (LODs) and the limits of quantitation (LOQs) of the method were 3–15μg/kg and 10–50μg/kg, respectively. Recoveries were calculated at three levels of concentration spiked in two kinds of cosmetics (skin care cream and water). The values were found between 93.8% and 121.0% with relative standard deviation (RSD) values of 2.5–7.2% for intra-day precision (n=6) and 3.3–6.7% for inter-day precision (n=5). The method was successfully applied to analyze twenty-two cosmetics samples and N-nitrosodimethylamine (NDMA) was detected in one sample with the concentration of 207μg/kg.

Development and Validation of a Sensitive GC-MS Method for the Determination of Alkylating Agent, 4-Chloro-1-butanol, in Active Pharmaceutical Ingredients

The analysis of genotoxic impurities (GTIs) in active pharmaceutical ingredients (APIs) is a challenging task. The target detection limit (DL) in an API is typically around 1 ppm (1 µg/g API). Therefore, a sensitive and selective analytical method is required for their analysis. 4-Chloro-1-butanol, an alkylating agent, is one of the GTIs. It is generated when tetrahydrofuran and hydrochloric acid are used during the synthesis of the APIs. In this study, a sensitive and robust gas chromatography-mass spectrometry (GC-MS) method was developed and validated for the identification of 4-chloro-1-butanol in APIs. In the GC-MS method, 3-chloro-1-butanol was employed as an internal standard to ensure accuracy and precision. Linearity was observed over the range 0.08 to 40 ppm (µg/g API), with a R(2) value of 0.9999. The DL and quantitation limit (QL) obtained were 0.05 ppm and 0.08 ppm (0.13 ng/mL and 0.20 ng/mL as the 4-chloro-1-butanol concentration), respectively. These DL and QL values are well over the threshold specified in the guidelines. The accuracy (recovery) of detection ranged from 90.5 to 108.7% between 0.4 ppm and 20 ppm of 4-chloro-1-butanol. The relative standard deviation in the repeatability of the spiked recovery test was 6.0%. These results indicate the validity of the GC-MS method developed in this study. The GC-MS method was applied for the determination of 4-chloro-1-butanol in the API (Compound A), which is under clinical trials. No 4-chloro-1-butanol was found in Compound A (below QL, 0.08 ppm).

Simultaneous determination of imperatorin and its metabolites in vitro and in vivo by a GC‐MS method: application to a bioavailability and protein binding ability study in rat plasma

In this study, a simple and sensitive gas chromatography-mass spectrometry method was developed for the study of bioavailability and protein binding and the metabolism of imperatorin in rat. The results showed that the pharmacokinetics of imperatorin after intravenous and oral administration in rats exhibited linear characteristics. The absolute bioavailability of imperatorin was calculated as ~3.85, ~33.51 and ~34.76% for 6.25, 12.5 and 25 mg/kg, respectively. The low bioavailability of imperatorin may be attributed to the poor absorption or extensive metabolism. The phase I metabolites of imperatorin formed in vitro by rat liver microsomes were studied, and two metabolites were isolated and identified as xanthotoxol and heraclenin. Following oral administration of imperatorin, one metabolite (heraclenin) was detected in rat plasma, and two potential metabolites (xanthotoxol and heraclenin) were detected in rat urine. However, none of potential metabolites was detected in rat feces and bile. The results showed that the metabolites of imperatorin were excreted by kidney, and heraclenin was associated with an active component. Demethylation and oxygenization were the main metabolic pathways. In vitro plasma protein binding of imperatorin was 90.1 and 92.6% for the spiked rat plasma concentrations of 1.0 and 50.0 µg/mL, respectively, indicating that imperatorin showed slow distribution into the intra- and extracellular space.

Occurrence of postmortem production of ethylene glycol and propylene glycol in human specimens

We previously established a sensitive gas chromatography–mass spectrometry method for analysis of ethylene glycol (EG), propylene glycol (PG), and diethylene glycol (DEG), and disclosed the presence of appreciable amounts of EG, PG, and DEG in fresh whole blood and urine specimens obtained from nonoccupational healthy humans. These results led us to analyze EG and PG in specimens taken from three human cadavers. EG and PG concentrations in the postmortem blood and solid tissues were much higher than those found in fresh whole blood; their concentrations in many postmortem specimens were more than tenfold those in fresh whole blood specimens, suggesting the postmortem production of EG and PG. Therefore, we examined the time courses of EG and PG concentrations in blood specimens in the absence and presence of saprogenic blood (10 % volume) and/or glucose (3 mg/ml) in vitro, which were left at room temperature for 7 days. EG concentration in fresh blood without any addition decreased slightly during the 7 days. EG concentration in the blood with addition of glucose, and PG concentrations in the blood with and without addition of glucose did not change appreciably during the 7 days. EG and PG concentrations in the blood after addition of 10 % saprogenic blood increased 3.1-fold and 3.5-fold after 7 days, respectively; those after addition of saprogenic blood plus glucose increased 9.1-fold and 11.9-fold after 7 days, respectively. These results show that microorganisms present in the saprogenic blood caused the postmortem production of EG and PG, and the addition of glucose further enhances the EG and PG concentrations, probably acting as the substrate for glycol production by the microorganisms. To our knowledge, this is the first report to describe postmortem production of EG and PG in human specimens.

Physicochemical characterization and pharmacokinetics evaluation of β-caryophyllene/β-cyclodextrin inclusion complex

β-Caryophyllene (BCP), a natural sesquiterpene existing in the essential oil of many plants, has exhibited a wide range of biological activities. However, its volatility and poor water-solubility limit its application in pharmaceutical field. β-Cyclodextrin (β-CD) has intrinsic ability to form specific inclusion complexes with different drugs to enhance their stability, solubility and bioavailability. The aim of this study is to investigate and compare the oral bioavailability and the pharmacokinetics of free BCP and BCP/β-CD inclusion complex after a single oral dose of 50mg/kg on rats. A simple, rapid, and sensitive gas chromatography-mass spectrometry method in selected ion monitoring (GC-MS/SIM) mode was developed on determination of BCP in rat plasma. The in vivo data showed that BCP/β-CD inclusion complex displayed earlier Tmax, higher Cmax and the AUC0-12h was approximately 2.6 times increase than those of free BCP. These results demonstrated that BCP/β-CD inclusion complex has significantly increased the oral bioavailability of the drug in rats than free BCP.

A rapid and sensitive gas chromatography-mass spectrometry method for the quality control of perfumes: simultaneous determination of phthalates

A rapid and sensitive analytical gas chromatography-mass spectrometry (GC-MS) method for perfume analysis to determine the phthalates banned by the European Union Regulation on cosmetic samples is presented. This method has been tested in commercial alcoholic perfume samples for the determination of the following seven phthalates: dibutyl phthalate, bis(2-ethylhexyl) phthalate, bis(2-methoxyethyl) phthalate, n-pentyl-isopentylphthalate, di-n-pentyl phthalate, diisopentylphthalate and benzyl butyl phthalate. Sample evaporation and redissolution in ethanol is carried out before GC-MS analysis, with no dilution of the sample. External calibration and standard addition calibration are compared to detect possible matrix effects. External calibration could provide good results in some cases but standard addition calibration is recommended as matrix effects are observed in many cases in the determination of the target phthalates. The accuracy of the method has been proven by the analysis of quality control samples prepared from commercial free phthalate perfumes after spiking with known concentrations of the analytes. Accurate results were obtained with limits of detection in the ng mL−1 range and good repeatability (relative standard deviations lower than 6%). The method was satisfactorily applied to the analysis of commercial perfume samples, and the results revealed considerable amounts of dibutyl phthalate and bis(2-ethylhexyl) phthalate in some of the analyzed samples.

A Sensitive Gas Chromatography-Mass Spectrometry Method for the Determination of Patulin in Apple Juice

A simple and sensitive GC/MS method was developed for the detection of patulin in apple juice. The method utilized a common laboratory chemical, 3-nitrobenzyl alcohol, as an internal standard. The calibration curve, ranging from 5 to 100 microg/L, showed good linearity with a correlation coefficient of 0.999. The LOD and LOQ were 2 and 5 microg/L, respectively. The significant advantage of the method was removal of the need for in-house synthesis of appropriate internal standards as reported by other researchers. The method also eliminated the need for careful sample preparation procedures, as outlined in some AOAC methods in which no internal standard was utilized. The streamlined extraction process and the improved sensitivity warrant the developed method to be a useful alternative for drug testing laboratories, especially those with large specimen volume and throughput to determine patulin levels in apple juice.

Development and Validation of a Simple GC–MS Method for the Simultaneous Determination of 11 Anticholinesterase Pesticides in Blood—Clinical and Forensic Toxicology Applications

Anticholinesterase pesticides are widely used, and as a result they are involved in numerous acute and even fatal poisonings. The aim of this study was the development, optimization, and validation of a simple, rapid, specific, and sensitive gas chromatography-mass spectrometry method for the determination of 11 anticholinesterase pesticides (aldicarb, azinphos methyl, carbofuran, chlorpyrifos, dialifos, diazinon, malathion, methamidophos, methidathion, methomyl, and terbufos) in blood. Only 500 μL of blood was used, and the recoveries after liquid-liquid extraction (toluene/chloroform, 4:1, v/v) were more than 65.6%. The calibration curves were linear (R(2) ≥ 0.996). Limit of detections and limit of quantifications were found to be between 1.00-10.0 and 3.00-30.0 μg/L, respectively. Accuracy expressed as the %E(r) was found to be between -11.0 and 7.8%. Precision expressed as the percent relative standard deviation was found to be <9.4%. The developed method can be applied for the investigation of both forensic and clinical cases of accidental or suicidal poisoning with these pesticides.

Gas Chromatography–Mass Spectrometry Assessment of Amines in Port Wine and Grape Juice after Fast Chloroformate Extraction/Derivatization

A simple, reliable, and sensitive gas chromatography-mass spectrometry method for the quantification of volatile and nonvolatile biogenic amines in Port wines and grape juices was developed and evaluated. The method was based on a previously reported two-phase derivatization procedure with isobutyl chloroformate in a toluene medium, which provides a quantitative reaction in 10 min. Following the derivatization step, the excess of reagent was eliminated by treatment with alkaline methanol. The derivatization procedure was performed directly on 1 mL of sample, avoiding any fastidious and time-consuming cleanup extraction steps. The method allows the simultaneous quantification of 22 amines, which can be found in wines: methylamine, dimethylamine, ethylamine, diethylamine, propylamine, isopropylamine, butylamine, isobutylamine, amylamine, isoamylamine, 2-methylbutylamine, hexylamine, pyrrolidine, piperidine, morpholine, 1,3-diaminopropane, putrescine, cadaverine, 1,6-diaminohexane, 2-phenylethylamine, histamine, and tyramine. Because of the fact that histamine and tyramine derivatives are degraded during the isobutyl chloroformate elimination step, the corresponding determination was made after removal of the excess of derivatizing reagent by evaporating an aliquot of the toluene layer obtained after the reaction. The presented method showed excellent analytical characteristics in what linearity, recovery, repeatability, and limit of detections were respected. It was used to assess the concentration of biogenic amines in juice grapes and Tawny and Vintage Port wines with different aging times. On the whole, the total content of amines in Port wines was low. Most of the amines found in wines have their origin in the raw material used for their elaboration, so the Port winemaking process is not prone to the production of this kind of compounds. Total biogenic amine contents have shown a decrease with the aging of both types of Port wines.

Concentrations of phytanic acid and pristanic acid are higher in organic than in conventional dairy products from the German market

Abstract Differentiation of organic and conventional dairy products is an important, yet difficult task in food authentication. In this study it was tested whether phytanic acid and pristanic acid can be used as markers for this purpose. Phytanic and pristanic acid cannot be de novo synthesised by mammals, and the predominant source for uptake is chlorophyll in food. Highest concentrations (but still in the sub-gram per 100 g lipids range) are found in ruminants because rumen bacteria are able to release phytol from chlorophyll and transforming it into phytanic acid. Degradation of phytanic acid leads to pristanic acid, and both fatty acids usually co-exist in biota. Owing to the unique source of grass-based feedstuffs in organic farming it was tested whether organic cheeses (n = 13) and other organic dairy products (n = 5) are higher in phytanic and pristanic acid concentrations than conventional products (n = 12). For this purpose, a sensitive gas chromatography–mass spectrometry method in the selected ion monitoring mode was developed. Organic cheeses contained on average 50% more phytanic acid and 30% more pristanic acid, while concentrations of 14-methylhexadecanoic acid (a17:0), i.e. another minor fatty acid in ruminants, were only slightly increased by 8%. A target value of at least 200 mg/100 g phytanic acid was suggested for the verification of grass-fed, organic dairy products. Some conventional products also reached the target value, and this indicated that the cows that gave the milk were also fed with grass-silage. On the other hand, only one organic cheese fell below this target value. It is recommended to control manufacturers whose organic dairy products show concentrations of below the target value of 200 mg phytanic acid per 100 gram lipids in order to confirm the application of organic principles.

Gas chromatography–mass spectrometric assay for propofol in cerebrospinal fluid of traumatic brain patients

A sensitive gas chromatography–mass spectrometry method for measuring propofol in cerebrospinal fluid is described, validated and applied to four patients after traumatic brain injury. The limit of quantitation was 2 μg/L using a volume of 0.5 mL. The inter- and intra-assay coefficients of variation were 5.9 and 5.1%, respectively. The assay covers the linear concentration range of 2–50 μg/L, which is relevant in clinical pharmacokinetic studies when propofol is used in the Intensive Care Unit as a sedative agent or to lower the intracranial pressure.

Sensitive Gas Chromatography-Mass Spectrometry Method for Simultaneous Measurement of MDEA, MDMA, and Metabolites HMA, MDA, and HMMA in Human Urine

A sensitive gas chromatography-mass spectrometry method was developed and validated for the simultaneous measurement of MDEA, MDMA, and its metabolites, 3,4-methylenedioxy-N-ethylamphetamine (MDEA), 3,4-methylenedioxymethamphetamine (MDMA or Ecstasy), and its metabolites, 4-hydroxy-3-methoxyamphetamine (HMA), 3,4-methylenedioxyamphetamine (MDA), and 4-hydroxy-3-methoxyamphetamine (HMMA) in human urine. We hydrolyzed 1 mL urine, fortified with MDMA-d5, MDA-d5, and MDEA-d6, with 100 microL of concentrated hydrochloric acid at 120 degrees C for 40 min, then added 100 microL 10 N sodium hydroxide and 3 mL phosphate buffer 0.1 N (pH 6.0) were added to hydrolyzed urine specimens before solid-phase extraction. After elution and evaporation, we derivatized extracts with heptafluorobutyric acid anhydride and analyzed with gas chromatography-mass spectrometry operated in EI-selected ion-monitoring mode. Limits of quantification were 25 microg/L for MDEA, MDMA, and its metabolites. Calibration curves were linear to 5000 microg/L for MDEA, MDMA, HMA, MDA, and HMMA, with a minimum r2 > 0.99. At 3 concentrations spanning the linear dynamic range of the assay, mean overall extraction efficiencies from urine were >85.5% for all compounds of interest. Intra- and interassay imprecisions, produced as CV, were <15% for all drugs at 30, 300, and 3000 microg/L. This gas chromatography-mass spectrometry assay provides adequate sensitivity and performance characteristics for the simultaneous quantification of MDEA, MDMA, and its metabolites HMMA, MDA, and HMA in human urine. The method meets and exceeds the requirements of the proposed Substance Abuse and Mental Health Services Administration's guidelines for federal workplace drug testing of MDEA and MDMA in urine.