Gas Chromatography-mass Spectrometry Procedure Research Articles

A proposed pathway from D-glucose to D-arabinose in eukaryotes

In eukaryotes, the D-enantiomer of arabinose (D-Ara) is an intermediate in the biosynthesis of D-erythroascorbate in yeast and fungi and in the biosynthesis of the nucleotide sugar GDP-α-D-arabinopyranose (GDP-D-Arap) and complex α-D-Arap containing surface glycoconjugates in certain trypanosomatid parasites. Whereas the biosynthesis of D-Ara in prokaryotes is well understood, the route from D-glucose (D-Glc) to D-Ara in eukaryotes is unknown. In this paper, we study the conversion of D-Glc to D-Ara in the trypanosomatid Crithidia fasciculata using positionally labelled [13C]-D-Glc and [13C]-D-ribose ([13C]-D-Rib) precursors and a novel derivatisation and gas chromatography-mass spectrometry procedure applied to a terminal metabolite, lipoarabinogalactan. These data implicate the both arms of pentose phosphate pathway and a likely role for D-ribulose-5-phosphate (D-Ru-5P) isomerisation to D-Ara-5P. We tested all C. fasciculata putative sugar and polyol phosphate isomerase genes for their ability to complement a D-Ara-5P isomerase-deficient mutant of Escherichia coli and found that one, the glutamine fructose-6-phosphate aminotransferase (GFAT) of glucosamine biosynthesis, was able to rescue the E. coli mutant. We also found that GFAT genes of other trypanosomatid parasites, and those of yeast and human origin, could complement the E. coli mutant. Finally, we demonstrated biochemically that recombinant human GFAT can isomerise D-Ru-5P to D-Ara5P. From these data, we postulate a general eukaryotic pathway from D-Glc to D-Ara and discuss its possible significance. With respect to C. fasciculata, we propose that D-Ara is used not only for the synthesis of GDP-D-Arap and complex surface glycoconjugates but also in the synthesis of D-erythroascorbate.

In-situ acetylation followed by liquid-liquid extraction and gas chromatography – mass spectrometry for the determination of bromophenols in urine

A novel and simple method combining in-situ acetylation, liquid-liquid extraction and gas chromatography-mass spectrometry (GC-MS) has been developed for the quantification of 10 bromophenols in urine, used as biomarkers of exposure to polybrominated diphenyl ethers. The analytical process involves an enzymatic hydrolysis of the bromophenol glucuronide fraction followed by an aqueous derivatization of the phenol group with acetic anhydride. A subsequent liquid-liquid extraction of the sample with hexane allows the injection of the organic layer, using a programmed temperature vaporizer, into a gas chromatograph coupled to a single quadrupole mass spectrometer. Quantification is performed by the standard addition method. Limits of detection are in the pg mL−1 range. Trueness, assessed in terms of percentages of recovery, varies between 100 % and 118 % in synthetic urine and between 79 % and 117 % in human urine. Precision, assessed at two different levels, 0.25 ng mL−1 and 2.5 ng mL−1, shows values of relative standard deviation below 14 % both in intra- and inter-day studies for both matrices. The method has been applied to the analysis of seven urine samples, measuring concentrations higher than the LOQ in three of them. These levels are in agreement with others found in literature, but they have been obtained by applying a much simpler and faster protocol. In addition, the replacement of silylating reagents by acetic anhydride, to derivatize the phenol moiety, provides a greener alternative to other GC-MS procedures published up to date.

Inhibitory effects of Jasminum grandiflorum L. essential oil on lipopolysaccharide-induced microglia activation-integrated characteristic analysis of volatile compounds, network pharmacology, and BV-2 cell.

Neuroinflammation is considered to have a prominent role in the pathogenesis of Alzheimer's disease (AD). Microglia are the resident macrophages of the central nervous system, and modulating microglia activation is a promising strategy to prevent AD. Essential oil of Jasminum grandiflorum L. flowers is commonly used in folk medicine for the relief of mental pressure and disorders, and analyzing the volatile compound profiles and evaluating the inhibitory effects of J. grandiflorum L. essential oil (JGEO) on the excessive activation of microglia are valuable for its application. This study aims to explore the potential active compounds in JGEO for treating AD by inhibiting microglia activation-integrated network pharmacology, molecular docking, and the microglia model. A headspace solid-phase microextraction combined with the gas chromatography-mass spectrometry procedure was used to analyze the volatile characteristics of the compounds in J. grandiflorum L. flowers at 50°C, 70°C, 90°C, and 100°C for 50min, respectively. A network pharmacological analysis and molecular docking were used to predict the key compounds, key targets, and binding energies based on the detected compounds in JGEO. In the lipopolysaccharide (LPS)-induced BV-2 cell model, the cells were treated with 100ng/mL of LPS and JGEO at 7.5, 15.0, and 30μg/mL, and then, the morphological changes, the production of nitric oxide (NO) and reactive oxygen species, and the expressions of tumor necrosis factor-α, interleukin-1β, and ionized calcium-binding adapter molecule 1 of BV-2 cells were analyzed. A total of 34 compounds with significantly different volatilities were identified. α-Hexylcinnamaldehyde, nerolidol, hexahydrofarnesyl acetone, dodecanal, and decanal were predicted as the top five key compounds, and SRC, EGFR, VEGFA, HSP90AA1, and ESR1 were the top five key targets. In addition, the binding energies between them were less than -3.9kcal/mol. BV-2 cells were activated by LPS with morphological changes, and JGEO not only could clearly reverse the changes but also significantly inhibited the production of NO and reactive oxygen species and suppressed the expressions of tumor necrosis factor-α, interleukin-1β, and ionized calcium-binding adapter molecule 1. The findings indicate that JGEO could inhibit the overactivation of microglia characterized by decreasing the neuroinflammatory and oxidative stress responses through the multi-compound and multi-target action modes, which support the traditional use of JGEO in treating neuroinflammation-related disorders.

Fluid Components in Cordierite from the Rocks of Epidote-Amphibole Facies of the Muzkol Metamorphic Complex, Tajikistan: Pyrolysis-Free GC-MS Data

The composition of volatile components of cordierite from the Muzkol metamorphic complex was studied using shock destruction with pyrolysis-free gas chromatography-mass spectrometry (GC-MS) with simultaneous IR and Raman spectroscopy. Applying the GC-MS procedure, the component relative concentrations (rel.%) and composition of different zones of cordierite crystals were determined. It was found that the substantially magnesian cordierite was formed with a predominantly aqueous-carbonic acid fluid (from 57.06 to 67.88 rel.% H2O, from 24.29 to 32.95 rel.% CO2). From the center towards the crystal periphery, the molar fraction of carbon dioxide (CO2/(H2O + CO2)) decreases from 0.36 to 0.26, whereas the alkane/alkene ratio increases from 0.80 to 0.88. At least 11 homologous series of organic compounds among the identified volatile components, in addition to water and carbon dioxide, were determined, including oxygen-free aliphatic and cyclic hydrocarbons (paraffins, olefins, cyclic alkanes and alkenes, arenes, polycyclic aromatic hydrocarbons (PAHs)), as well as oxygen-containing (alcohols, esters, aldehydes, ketones, carboxylic acids) and heterocyclic (furans, dioxanes) organic compounds.

Extraction of Phytochemical Constituents from the root of Eclipta Alba through Gas chromatography-mass spectrometry procedure

The higher herbal values of Eclipta Alba have a long history in the treatment of various ailments in traditional and folk medicine in many tropical and sub-tropical countries. Medicinal plants play a significant role in human culture and civilization. Eclipta Alba plant roots were powdered. By using simple soxhlation method, methanol extract was prepared. The powdered extract of Eclipta alba and methanol extract was concentrated and analyzed using Gas Chromatography-Mass Spectroscopy to identify the biochemical components of Eclipta Alba root extract in the present study. A wide range of active ingredients such as 2- Thiophene carbaldehyde, 5-[5-(thien-2-yl) thien-2-yl]- 0.08%, Dodecanoic acid - 0.19, 9-Octadecenamide, (Z)- (CAS) OLEOAMIDE - 0.29, Loliolide – 0.37 and– 44.86. This study supports, methanolic extract of eclipta alba has potential antimicrobial, antioxidant and hepatoprotective activities.

Volatile profile evolution of Reggianito cheese during ripening under different temperature–time combinations

Using solid-phase microextraction and gas chromatography–mass spectrometry procedure, volatile compounds were studied during ripening of Reggianito cheeses stored under different temperature–time combinations. Volatile profile was characterised for cheeses ripened under standard conditions at 0, 61, 124 and 180 days of ripening, and changes occurring between 61 and 180 days were evaluated for cheeses in which an elevated temperature of 20 °C was applied within the first month of maturation. A total of 41 volatile compounds including acids, ketones, aldehydes, esters, alcohols and hydrocarbons were identified. Despite the presence of other compounds of potential relevance for cheese flavour, carboxylic acids clearly dominated the volatile profile of Reggianito cheeses. The more notable variations in the volatile fraction of Reggianito cheeses occurred during the first 2 months of ripening and were mostly explained by changes observed for the predominant acid fraction. Significant changes in the quantities for some volatile compounds were observed for the different temperature–time combinations applied, though the balance between the different groups of compounds was not considerably affected and small changes were observed for total chromatographic area values. In this work, a first description of changes occurring during ripening for the different volatile compounds present in traditional Reggianito cheese was provided.

A urinary test procedure for identification of cannabidiol in patients undergoing medical therapy with marijuana.

Marijuana is classified by the Drug Enforcement Agency (DEA) as Schedule I, drugs having no accepted medical value. Twenty-three states and the District of Columbia have legalized medical marijuana. This conflict inhibits physicians from prescribing marijuana and the systematic study of marijuana in medical care. This study concerns the use of the clinical laboratory as a resource for physicians recommending cannabidiol (CBD) to patients, or for patients using medical marijuana. Marijuana containing delta-9-tetrahydrocannabinol (THC) is psychoactive. CBD is not psychoactive. CBD is reported to have medical benefit for seizure control, neurologic disorders including multiple sclerosis, neuropathic pain and pain associated with cancer. Use of opiates leads to increasing dosage over time that may cause respiratory depression. The Medical Board of California has termed this a serious public health crisis of addiction, overdose, and death. Is it feasible that CBD might alleviate persistent, severe pain and therefore diminished opiate use? Further study is needed to determine medical effectiveness of CBD including the effect on concurrent opiate therapy due to competition for receptor sites. This study is the application of a gas chromatography mass spectrometry procedure adapted for use in our laboratory, to detect CBD in urine. The intended use is as a tool for physicians to assess that marijuana being used by a patient is of a composition likely to be medically effective. A law ensuring physicians freedom from federal prosecution would provide confidence essential to formal study of medical uses of marijuana and treatment of clinical problems. Detection of CBD in a urine sample would be a convenient test for such confirmation.

Detection of formestane abuse by mass spectrometric techniques.

Formestane (4-hydroxy-androstenedione) is an aromatase inhibitor prohibited in sports and included, since 2004, in the list of prohibited substances updated yearly by the World Anti-Doping Agency (WADA). Since the endogenous production of formestane has been described, it is mandatory for the anti-doping laboratories to use isotope ratio mass spectrometry (IRMS) to establish the exogenous origin before issuing an adverse analytical finding. The described IRMS methods for formestane detection are time-consuming, requiring usually two consecutive liquid chromatographic sample purifications in order to have final extracts of adequate purity before the mass spectrometric analysis. After establishing a procedure for the determination of the origin of formestane by IRMS without the need of derivatization, and integrated in the overall analytical strategy of the laboratory for pseudo-endogenous steroids, a mass spectrometric analysis by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) of formestane metabolites was carried out in order to investigate whether other biomarkers of formestane abuse could be integrated in order to avoid time-consuming and expensive IRMS confirmations for formestane. From the metabolic studies performed, the inclusion of 3β,4α-dihydroxy-5α-androstan-17-one (4α-hydroxy-epiandosterone) in the routine GC-MS procedures has demonstrated to be diagnostic in order to reduce the number of unnecessary confirmations of the endogenous origin of formestane.

False carbamazepine positives due to 10,11-dihydro-10-hydroxycarbamazepine breakdown in the GC-MS injector port.

During the investigation of aviation accidents, postmortem specimens from accident victims are submitted to the Federal Aviation Administration's Civil Aerospace Medical Institute (CAMI) for toxicological analysis. A case recently received by CAMI screened positive for the anticonvulsant medication carbamazepine (CBZ; Tegretol(®)) by gas chromatography-mass spectrometry (GC-MS). The CBZ found during this routine screening procedure was subsequently confirmed using a CBZ-specific GC-MS procedure. It was later discovered that the accident victim had been prescribed oxcarbazepine (OXCBZ; Trileptal(®)). OXCBZ is structurally similar to CBZ and is metabolized by cytosolic enzymes in the liver to an active metabolite, 10,11-dihydro-10-hydroxycarbamazepine (DiCBZ). It was determined that the CBZ initially found in this case was present due to the thermal breakdown of DiCBZ in the GC-MS injector port. In the current study, this conversion was investigated and the percentage of CBZ formed at various injector port temperatures was determined. Additionally, these three compounds were quantified in nine fluid and tissue specimens from the case in question. Liquid chromatography-mass spectrometry was also incorporated to further demonstrate the absence/presence of CBZ in these samples.

Exposure to tobacco smoke based on urinary cotinine levels among Israeli smoking and nonsmoking adults: a cross-sectional analysis of the first Israeli human biomonitoring study

BackgroundCotinine levels provide a valid measure of exposure to environmental tobacco smoke (ETS). The goal of this study was to examine exposure to tobacco smoke among smoking and nonsmoking Israeli adults and to identify differences in ETS exposure among nonsmokers by socio-demographic factors.MethodsWe analyzed urinary cotinine data from the first Israeli human biomonitoring study conducted in 2011. In-person questionnaires included data on socio-demographic and active smoking status. Cotinine levels were measured using a gas chromatography–mass spectrometry procedure. We calculated creatinine-adjusted urinary cotinine geometric means (GM) among smokers and nonsmokers, and by socio-demographic, smoking habits and dietary factors. We analyzed associations, in a univariable and multivariable analysis, between socio-demographic variables and proportions of urinary cotinine ≥1 μg/l (Limit of Quantification = LOQ) or ≥4 μg/l.ResultsCotinine levels were significantly higher among 91 smokers (GM = 89.7 μg/g creatinine; 95% confidence interval [CI]: 47.4-169.6) than among 148 nonsmokers (GM = 1.3; 1.1-1.7). Among exclusive waterpipe smokers, cotinine levels were relatively high (GM = 53.4; 95% CI 12.3-232.7). ETS exposure was widespread as 62.2% of nonsmokers had levels ≥ LOQ, and was higher in males (75.8%) than in females (52.3%). In a multivariable model, urinary cotinine ≥ LOQ was higher in males (Prevalence ratio [PR] = 1.30; 95% CI: 1.02-1.64, p = 0.032) and in those with lower educational status (PR = 1.58; 1.04-2.38, p = 0.031) and decreased with age (PR = 0.99; 0.98-1.00, p = 0.020, per one additional year). There were no significant differences by ethnicity, residence type or country of birth.ConclusionsOur findings indicate widespread ETS exposure in the nonsmoking Israeli adult population, especially among males, and younger and less educated participants. These findings demonstrate the importance of human biomonitoring, were instrumental in expanding smoke-free legislation implemented in Israel on July 2012 and will serve as a baseline to measure the impact of the new legislation.

Furan in canned sardines and other fish

Thirty-seven different samples of canned sardines and other fish sold in the United Kingdom were analysed for their furan content using a validated automated headspace gas chromatography–mass spectrometry procedure. All 37 samples contained detectable furan, with an average level of 26 μg kg−1. The maximum furan content was in canned fish containing tomato sauce, which had an average of 49 μg kg−1 and in canned fish packed with lemon which had an average of 55 μg kg−1. All fish in brine or in oil contained less than 20 μg kg−1 furan. Furan levels recorded in fish packed in extra virgin olive oil were low with an average of 2 μg kg−1.

Detection of p-Chloroamphetamine in Urine Samples with Mass Spectrometry

Designer drugs are introduced periodically to avoid detection and to provide new drugs with different pharmacological activities. During our routine analysis of amphetamine in urine samples, we observed one sample that reacted with immunoassay with high activity. There is one prominent peak in the gas chromatography- mass spectrometry (GC-MS) chromatogram. However, no amphetamine, methamphetamine, MDA, MDMA, MDEA, or ephedrine was detected with GC-MS. Careful examination of the mass spectrum indicated the presence of one fragment ion (m/z 140), which is similar to the base peak of trifluoroacetic anhydride derivative of amphetamine. The characteristic ion cluster representing the presence of one chlorine atom was observed. Investigation with liquid chromatography (LC)-MS detected an unknown compound with molecular ion of m/z 170. This compound was tentatively identified as chloroamphetamine. Pure standard material of p-chloroamphetamine (PCA) was purchased and analyzed with both GC-MS and LC-MS. Identical GC-MS spectra and LC-MS-MS fragmentation patterns were obtained. A GC-MS procedure was developed for the quantitation of PCA. The limits of detection and quantification were 10 μg/L. Precision was between 1.26% and 4.26%, and bias was between -0.91% and 4.27%. The prevalence PCA positive rate is 0.35% of the samples screened positive for amphetamine.

Urine Analysis of 3,4-Methylenedioxypyrovalerone in Opioid-Dependent Patients by Gas Chromatography–Mass Spectrometry

A gas chromatography-mass spectrometry (GCMS) procedure was developed for the quantitative analysis of the new designer drug methylenedioxypyrovalerone (MDPV) in urine together with the common stimulants amphetamine, methamphetamine, and methylenedioxymethamphetamine (MDMA). The procedure involved electron ionization (EI) GCMS in the selected ion monitoring (SIM) mode after liquid-liquid extraction with toluene and derivatization with heptafluorobutyric acid anhydride. All MDPV findings were confirmed by positive chemical ionization GCMS in SIM mode. Positive chemical ionization-GCMS allowed the protonated molecule M+H+ m/z 276 to be used as a target ion with 3 abundant fragments as qualifier ions. By electron ionization-GCMS, the limit of quantification (LOQ) for MDPV was 0.02 mg/L; and for amphetamine, methamphetamine, and MDMA, the LOQ was 0.05 mg/L. The method was applied to monitoring urine samples from opioid-dependent patients undergoing opioid substitution treatment. Nine of the 34 urine samples (26%) analyzed were MDPV positive by the GCMS procedure. The positive samples were obtained from 2 female and 7 male patients with a mean age of 31 years. The median (range) MDPV concentration was 0.16 mg/L (0.04-3.9 mg/L) based on the 7 samples for which a numeric value was obtained, whereas the concentration was below the LOQ but above the limit of detection in 2 samples. The method revealed amphetamine in approximately 40% of the cases, and there was no statistical difference between the MDPV-positive and MDPV-negative groups. Urine amphetamine concentrations were on average 10 times higher than those of MDPV. The opioid-dependent patients used MDPV mainly as a substitute for amphetamine, judging from the laboratory findings of this study and the information from our patients.

Monitoring of kratom or Krypton intake in urine using GC-MS in clinical and forensic toxicology

The Thai medicinal plant Mitragyna speciosa (kratom) is misused as a herbal drug. Besides this, a new herbal blend has appeared on the drugs of abuse market, named Krypton, a mixture of O-demethyltramadol (ODT) and kratom. Therefore, urine drug screenings should include ODT and focus on the metabolites of the kratom alkaloids mitragynine (MG), paynantheine (PAY), speciogynine (SG), and speciociliatine (SC). The aim of this study was to develop a full-scan gas chromatography-mass spectrometry procedure for monitoring kratom or Krypton intake in urine after enzymatic cleavage of conjugates, solid-phase extraction, and trimethylsilylation. With use of reconstructed mass chromatography with the ions m/z 271, 286, 329, 344, 470, 526, 528, and 586, the presence of MG, 16-carboxy-MG, 9-O-demethyl-MG, and/or 9-O-demethyl-16-carboxy-MG could be indicated, and in case of Krypton, with m/z 58, 84, 116, 142, 303, 361, 393, and 451, the additional presence of ODT and its nor metabolite could be indicated. Compounds were identified by comparison with their respective reference spectra. Depending on the plant type, dose, administration route, and/or sampling time, further metabolites of MG, PAY, SG, and SC could be detected. The limits of detection (signal-to-noise ratio of 3) were 100 ng/ml for the parent alkaloids and 50 ng/ml for ODT. As mainly metabolites of the kratom alkaloids were detected in urine, the detectability of kratom was tested successfully using rat urine after administration of a common user's dose of MG. As the metabolism in humans was similar, this procedure should be suitable to prove an intake of kratom or Krypton.

Characterisation of beeswax in works of art by gas chromatography–mass spectrometry and pyrolysis–gas chromatography–mass spectrometry procedures

Pyrolysis (Py) with in situ derivatisation with hexamethyldisilazane–gas chromatography–mass spectrometry (GC–MS) and a gas chromatography–mass spectrometry procedure based on microwave-assisted saponification were used to identify the organic components in small sized beeswax samples. With the latter procedure quantitative recoveries can be made and hydrocarbons, alcohols and ω-1-diols in the neutral fraction, and fatty acids and ω-1-hydroxy acids in the acidic fraction can be efficiently separated and detected. Both procedures were used to characterise a wax anatomic sculpture “The Plague” (1691–1694) by Gaetano Zumbo, resulting in the identification of beeswax and a Pinaceae resin. The GC–MS analysis brought to light some essential differences in beeswax composition between the raw material and the old modelled wax thus giving some clear indications about the recipe used by the sculptor.

Fast solid-phase extraction–gas chromatography–mass spectrometry procedure for oil fingerprinting: Application to the Prestige oil spill

A rapid and simple fractionation procedure using solid-phase extraction (SPE) cartridges was developed for an accurate determination of aliphatic and polycyclic aromatic hydrocarbons in petroleum residues and further application in chemical fingerprinting of oil spills by gas chromatography–mass spectrometry (GC–MS). Among the adsorbents evaluated, SiO 2/C 3CN exhibited the best selectivity, providing, by elution with n-hexane (4 ml) and n-hexane–CH 2Cl 2 (1:1) (5 ml), two well-resolved aliphatic and aromatic hydrocarbon fractions, with recoveries of 97±7.2 and 99.7±13.9%, respectively. The SPE fractionation procedure was compared with the conventional silica–alumina adsorption chromatography showing similar results but practical advantages in terms of reproducibility, analysis time, solvent reduction and cost. Moreover, is particularly suitable for routine analysis with a high sample throughput. The developed methodology was tested in the characterization of fuel-oil samples collected along the Spanish north-west coast, after the Prestige oil spill accident.

Determination of the isoflavonoids genistein and daidzein in biological samples by gas chromatography-mass spectrometry.

The marked differences in the incidences of both breast and prostate cancer between the East and the West have been attributed to habitual diet. Traditionally, Japanese and Far Eastern people in general consume large quantities of soya and soya-derived foodstuffs. Diphenolic soya phytoestrogens have weak oestrogenic and anti-oestrogenic properties and have been implicated in preventing or limiting the early processes associated with breast and prostate carcinogenesis. We have developed a gas chromatography-mass spectrometry procedure that is suitable for measurement of the phytoestrogens daidzein and genistein in serum, urine and tissue samples. In serum samples of Japanese subjects mean (standard deviation) concentrations of daidzein [men, 281 (375.5) nmol/L; women, 246 (369.4) nmol/L] and genistein (men, 493 (604.4) nmol/L; women, 502 (717.6) nmol/L] were approximately 15 times higher than the mean levels achieved in British men [daidzein, 18.2 (20.4) nmol/L; genistein, 34.1 (27.2) nmol/L] and women [daidzein, 13.5 (11.6) nmol/L; genistein, 30.1 (31.2) nmol/L]. In pharmacokinetic studies of British subjects, maximum levels of daidzein and genistein were achieved within 6-8 h after the consumption of a cereal bar containing 20 mg of soya isoflavonoids; these levels were very similar to the mean levels achieved in normal Japanese subjects. Unlike serum, the mean daidzein concentration in urine from British subjects was higher than the mean genistein concentration (1.66 and 0.72 micromol per 24 h, respectively); following soy supplementation, urinary isoflavonoid levels were increased at least 10-fold. Serum daidzein and genistein concentrations are lower in British subjects than in Japanese subjects; this may be due to dietary differences.

An initial assessment of thermally assisted hydrolysis and methylation-gas chromatography/mass spectrometry for the identification of oils from dried paint films

Conservation scientists are frequently asked to identify the materials that are contained in microscopic fragments from works of art. For decades, the only technique successfully used for characterising the type of oil binder used from dried oil paints has been gas chromatography/mass spectrometry (GCMS). Unfortunately, the process requires a lengthy sample preparation and some of the derivatisation processes used present serious health and safety implications. Although thermally assisted hydrolysis and methylation-GCMS (THM-GCMS) has been used more recently for the analysis of traditional paint binders, its ability to distinguish between different oil types has yet to be ascertained. This paper describes the use of THM-GCMS to examine differences in the fatty acid composition of dried pigmented films of linseed, linseed stand, poppy, safflower and walnut oil. The results were compared for pyrolysis at 610 and 770 °C, two of the most commonly used temperatures in Curie point pyrolysis, in order to verify reproducibility of the results. Based on three runs for each sample, the fatty acid composition (measured as methyl esters) was found to be temperature-dependent, as previously suggested in literature. At the lower pyrolysis temperature (610 °C), a higher degree of reproducibility was seen and the ability to differentiate between each of the dried oil types using palmitate/stearate (P/S) ratios was improved. Interestingly, the P/S observed for each oil at this pyrolysis temperature were found to be close to those obtained by published GCMS procedures. In addition, samples of dried pigmented films of egg yolk were investigated and it was confirmed that this medium could be differentiated from each of the drying oils at this pyrolysis temperature from their azelate/palmitate ratios. These preliminary findings are encouraging for the use of THM-GCMS as an alternative method to GCMS for the identification of oils used as binders in paints.

Analysis of the compartmentation of glycolytic intermediates, nucleotides, sugars, organic acids, amino acids, and sugar alcohols in potato tubers using a nonaqueous fractionation method.

The compartmentation of metabolism in heterotrophic plant tissues is poorly understood due to the lack of data on metabolite distributions and fluxes between subcellular organelles. The main reason for this is the lack of suitable experimental methods with which intracellular metabolism can be measured. Here, we describe a nonaqueous fractionation method that allows the subcellular distributions of metabolites in developing potato (Solanum tuberosum L. cv Desiree) tubers to be calculated. In addition, we have coupled this fractionation method to a recently described gas chromatography-mass spectrometry procedure that allows the measurement of a wide range of small metabolites. To calculate the subcellular metabolite concentrations, we have analyzed organelle volumes in growing potato tubers using electron microscopy. The relative volume distributions in tubers are very similar to the ones for source leaves. More than 60% of most sugars, sugar alcohols, organic acids, and amino acids were found in the vacuole, although the concentrations of these metabolites is often higher in the cytosol. Significant amounts of the substrates for starch biosynthesis, hexose phosphates, and ATP were found in the plastid. However, pyrophosphate was located almost exclusively in the cytosol. Calculation of the mass action ratios of sucrose synthase, UDP-glucose pyrophosphorylase, phosphoglucosisomerase, and phosphoglucomutase indicate that these enzymes are close to equilibrium in developing potato tubers. However, due to the low plastidic pyrophosphate concentration, the reaction catalyzed by ADP-glucose pyrophosphorylase was estimated to be far removed from equilibrium.

The effect of anxiety and personality on the pharmacokinetics of oral midazolam.

We investigated the relationship between the pharmacokinetic variables of oral midazolam and patients' state/trait anxiety and personality. Twenty-six patients received the standard 15-mg oral dose for anxiolysis on the evening before otorhinolaryngological surgery. Blood samples were taken over a 9-h period after the administration, and the samples were analyzed for concentrations of midazolam and its two main metabolites by using a gas chromatography-mass spectrometry procedure. The pharmacokinetic variables maximum concentration, time to reach the maximum concentration, the elimination half-life, and the area under the curve were calculated from these data. When the patients were divided into groups with respect to their anxiety and personality scores, no significant differences in the pharmacokinetic variables of midazolam could be found. Only small, insignificant changes in the maximum concentrations were found with respect to nervousness and emotionality. We conclude that personality traits and anxiety levels had no effect on the pharmacokinetic variables of midazolam. We conclude that personality traits and anxiety levels had no effect on the pharmacokinetic variables of midazolam. Therefore, it is not necessary to obtain anxiety or personality scores to find the proper midazolam dose for the individual patient.