Gas Chromatography-electron Impact Mass Research Articles

Broccoli Leaves (Brassica oleracea var. Italica) as a Source of Bioactive Compounds and Chemical Building Blocks: Optimal Extraction Using Dynamic Maceration and Life Cycle Assessment

Bioactive compounds (BACs) and chemical building blocks (CBBs) play a pivotal role in driving economic growth. These compounds, known for their diverse applications in pharmaceuticals, agriculture, and manufacturing, have become integral to meeting the increasing demand for sustainable and innovative products. In this research, we used and characterized dynamic maceration to extract BACs and CBBs from broccoli leaves (BLs). A central composite design (CCD) was selected to evaluate the effect of temperature (from 4 °C to 70 °C), ethanol concentration (from 30% to 70% (v/v)), and exposition time (15 to 60 min) on total phenolic content (TPC) (mg of gallic acid equivalents (GAEs) per 100 g of dry biomass (db)). A confirmation experiment (CE) was performed to reproduce the optimal conditions (50 °C, 36.92 min, and 30% (v/v)) for BAC extraction. Results indicated a GAE concentration of 112.95 ± 0.92 mg/100 g db, while the statistical model predicted a value of 111.87 mg of GAEs/100 g db (error of 0.95%) with a rate constant (k) value of 0.0154 mg/g·min (R2 of 0.9894). BACs and CBBs were identified with gas chromatography–electron impact mass spectrometry detecting l-isoleucine, l-leucine, malonic acid, and succinic acid, among others. Finally, a life cycle inventory (LCI) was developed to determine global warming (GW) and water consumption (WC), among others, for 10 g of BL extract. Findings reported herein prove the sustainability of eco-friendly extraction of BACs and CBBs for the effective use of agricultural by-products.

Analysis, identification and confirmation of synthetic opioids using chloroformate chemistry: Retrospective detection of fentanyl and acetylfentanyl in urine and plasma samples by EI-GC-MS and HR-LC-MS.

Electron Impact Gas Chromatography-Mass Spectrometry (EI-GC-MS) and High Resolution Liquid Chromatography-Mass Spectrometry (HR-LC-MS) have been used in the analysis of products arising from the trichloroethoxycarbonylation of fentanyl and acetylfentanyl in urine and plasma matrices. The method involves the initial extraction of both synthetic opioids separately from the matrices followed by detection of the unique products that arise from their reaction with 2,2,2-trichloroethoxycarbonyl chloride (Troc-Cl), namely Troc-norfentanyl and Troc-noracetylfentanyl. The optimized protocol was successfully evaluated for its efficacy at detecting these species formed from fentanyl and acetylfentanyl when present at low and high levels in urine (fentanyl: 5 and 10 ng/mL and acetylfentanyl: 20 and 100 ng/mL) and plasma (fentanyl: 10 and 20 ng/mL and acetylfentanyl: 50 and 200 ng/mL), values that reflect levels reported in overdose victims. The HR-LC-MS method's LOQ (limit of quantitation) for the Troc-norfentanyl and Troc-noracetylfentanyl products was determined to be ~10 ng/mL for both species. Even though the superiority in the detection of these species by HR-LC-MS over EI-GC-MS, the latter method proved to be important in the detection of the second product from the reaction, namely 2-phenylethyl chloride that is crucial in the determination of the original opioid. This observation highlights the importance of using complimentary analytical techniques in the analysis of a sample, whether biological or environmental in nature. The method herein serves as a complementary, qualitative confirmation for the presence of a fentanyl in collected urine, plasma and by extension other biological samples amenable to the common extraction procedures described for opioid analysis. More importantly, the method's main strength comes from its ability to react with unknown fentanyls to yield products that can be not only detected by EI-GC-MS and HR-LC-MS but can then be used to retrospectively identify an unknown fentanyl.

Determination of Phosphodiesterase Type 5 Enzyme (PDE-5) Inhibitors and Analogues as Adulterants in Selected Herbal Products using Gas Chromatography–Electron Impact-Mass Spectrometer (GC-EI-MS)

Sildenafil, tadalafil, and vardenafil are phosphodiesterase type 5 enzyme (PDE-5) inhibitors used for the treatment of male erectile dysfunction. This present study aims to investigate 55 herbal products indicated for men’s sexual health from the Malaysian market for adulteration of PDE-5 inhibitors and analogues. The screening and identification of 20 PDE-5 inhibitors and analogues in herbal products of various forms (powder, capsules, tablets, and pastels) were conducted using gas chromatography–electron impact-mass spectrometer (GC-EI-MS). The analysis has shown that 19 herbal products were adulterated with PDE-5 inhibitors and analogues. Unique ion fragmentations and the presence of molecular ion serve as potential markers, and the limit of detection (LOD) was 0.1-5.0 µg/g. Ten PDE-5 inhibitors and analogues were randomly selected and successfully validated for simultaneous quantification, whereby the limit of quantitation (LOQ) was 5.0–50.0 µg/g with recoveries at 86.1-118.9%. The developed method of GC-EI-MS was shown to be simple, throughput, economical and had sufficient sensitivity to screen, identify and quantify PDE-5 inhibitors and analogues in herbal matrices.

Effect of N Supply Level and N Source Ratio on Cichorium spinosum L. Metabolism

Cichorium spinosum L. is considered a health-promoting vegetable that has been recently introduced in cultivation, and thus information on the responses of its different ecotypes to N supply level and source is largely fragmented. To cover this gap of knowledge, seeds of two different local ecotypes of C. spinosum L. originating from a coastal and a montane habitat of the island of Crete were propagated, and the obtained seedlings were grown hydroponically. The supplied nutrient solution differed in the total-N level (4 or 16 mmol L−1) and N source (NH4-N/-N/total-N: 0.05, 0.25, or 0.50). The impact of N supply level and N source ratio on the metabolism of the two ecotypes was assessed by gas chromatography–electron impact–mass spectrometry (GC/EI/MS) metabolomics combined with bioinformatics analyses. A general disturbance of the plants’ metabolism was recorded, with results revealing that the genotypic composition was the predominant factor for the observed discriminations. The montane ecotype exhibited substantially lower levels of metabolites such as fructose and α-α-trehalose, and higher levels of glucose, myo-inositol, and fatty acids compared to the coastal ecotype when both were treated with low N. Carboxylic acids and metabolites of the tricarboxylic acid cycle (TCA) were also substantially affected by the N supply level and the NH4-N/total-N ratio. The obtained information could be further exploited in the breeding of cultivars with improved nutritional value and resilience to variations in N supply levels and sources.

In vitro plants of Vitis vinifera respond to infection with the fungus Phaeoacremonium parasiticum by synthesizing the phytoalexin nerolidol

This study investigated terpene biosynthesis in basal and apical tissues of in vitro-grown plants of Vitis vinifera cv. Chardonnay infected or not (control) with Phaeoacremonium parasiticum. This pathogen is one of the prevalent agents involved in the grapevine “hoja de malvon” disease. The main terpene identified by gas chromatography electron impact mass spectrometry (GC-EIMS) was nerolidol, which was found in apical and basal tissues at a concentration of ca. 0.12 μg mg FW−1. Consistent with this, an increment in terpene synthase (TPS) activity, assessed as tritiated farnesyl pyrophosphate ([1−3H]-FPP) transformed into hexane-soluble radioactive products in infected plants, was observed. TPS activity increased in correlation with the fungal concentration. Nerolidol inhibited in vitro mycelium growth and reduced fungal growth, in a concentration dependent manner. According to our results, the response of grapevine tissues to Pm. parasiticum is systemic, as it can be visualized by an augment of transcript abundance of VvPNLinNer1. It is also characterized by an increase of de novo synthesis of TPS responsible for the biosynthesis of phytoalexin nerolidol. This is the first report in assessing in vitro grapevines response to woody fungus by modulating the route of terpene synthesis so increasing the phytoalexin nerolidol.

Carbon Atomic Survey for Identification of Selected Metabolic Fluxes.

Stable-isotope-labeling experiments have become a frequently used tool to investigate different metabolic systems. They have been recently applied to several comprehensive studies in plant metabolomics providing interesting insights into metabolic dynamics and regulation. However, the complexity of mass spectrometry data originating from such experiments is rarely fully explored. Data analysis often considers metabolites in their entirety which obscures important information at the atomic level. Recently, the use of mass spectrometry fragmentation for obtaining positional-labeling information was described for a few specific metabolites. Here, we describe a general methodology that can be applied for extracting positional-labeling information based on the characterization of fragments that are inherent in gas chromatography electron impact mass spectrometry (GC-EI-MS) chromatograms.

Elucidation of oxidation and degradation products of oxygen containing fuel components by combined use of a stable isotopic tracer and mass spectrometry

In order to reveal the degradation products of oxygen-containing fuel components, in particular fatty acid methyl esters, a novel approach was developed to characterize the oxidation behaviour. Combination of artificial alteration under pressurized oxygen atmosphere, a stable isotopic tracer, and gas chromatography electron impact mass spectrometry (GC-EI-MS) was used to obtain detailed information on the formation of oxidation products of (9Z), (12Z)-octadecadienoic acid methyl ester (C18:2 ME). Thereby, biodiesel simulating model compound C18:2 ME was oxidized in a rotating pressurized vessel standardized for lubricant oxidation tests (RPVOT), i.e., artificially altered, under 16O2 as well as 18O2 atmosphere. Identification of the formed degradation products, mainly carboxylic acids of various chain lengths, alcohols, ketones, and esters, was performed by means of GC-EI-MS. Comparison of mass spectra of compounds under both atmospheres revealed not only the degree of oxidation and the origin of oxygen atoms, but also the sites of oxidative attack and bond cleavage. Hence, the developed and outlined strategy based on a gas-phase stable isotopic tracer and mass spectrometry provides insight into the degradation of oxygen-containing fuels and fuel components by means of the accurate differentiation of oxygen origin in a degradation product.

Identification of (2-aminopropyl)benzofuran and its metabolites in human urine

An HPLC−HRMS method for the detection of the benzofuran analog of amphetamine and its metabolites in human urine using both library search and target search of the most probable metabolites based on their calculated accurate weights and fragmentation regularities is proposed. The proposed method is confirmatory. Gas chromatography–electron impact mass spectrometry with library search is proposed as the main screening method.

Organic compound composition in soil and sediments collected in Jackson, Mississippi

ABSTRACTThe aim of our study was to identify organic pollutants found in soil and sediment samples collected within the Jackson, MS metropolitan area. The chemical characterization of the organic compound fractions in soil and sediment samples was carried out by separating the organic fraction using column chromatography (CC) and quantitatively analyzing the polycyclic aromatic hydrocarbons (PAHs), n-alkanes and other organic compounds using gas chromatography–electron impact mass spectrometry (GC–MS). Fifty-six compounds were identified and quantified in the soil samples and 33 compounds were identified and quantified in the sediment samples. The PAHs, n-alkanes and other organic compound profiles in the soil and sediment samples were compared. The percentage contents of the organic compounds in the soil samples were very diverse (from traces to 12.44 ± 1.47%). The compounds present in the highest concentrations were n-alkanes: n-C31 (12.44 ± 1.47%), n-C29 (11.64 ± 1.21%), and n-C33 (8.95 ± 1.08%). The components occurring in smaller quantities (from 1% to 5%) were 2 PAHs (fluoranthene 1.28 ± 0.25%, pyrene 1.16 ± 0.20%), 10 n-alkanes from n-C21 (1.25 ± 0.29%) to n-C32 (2.67 ± 0.52%) and 11 other compounds (e.g., 2-pentanol, 4-methyl (3.33 ± 0.44%), benzyl butyl phthalate (4.25 ± 0.59%), benzenedicarboxylic acid (1.14 ± 0.08%), ethane, 1,1-diethoxy (3.15 ± 0.41) and hexadecanoic acid (2.52 ± 0.34). The soil samples also contained 30 compounds present in concentrations <1% (e.g., anthracene (0.13 ± 0.04%), n-C20 (0.84 ± 0.21%) and acetic acid (0.12 ± 0.04%). The compounds present in the highest concentrations in the sediment samples were PAHs: pyrene (7.73 ± 1.15%) and fluoranthene (6.23 ± 1.07%) and n-alkanes: n-C31 (6.74 ± 1.21%), n-C29 (6.65 ± 0.98%) and n-C27 (6.13 ± 1.09%). The remaining organic compounds were present in smaller quantities (< 5%).

Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation.

Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH), 3-mercaptohexylacetate (3-MHA), and 4-mercapto-4-methyl-2-pentanone (4-MMP)) are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS). We describe a method in which thiols are converted to pentafluorobenzyl (PFB) derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME) and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%–109%) and precision (5%–11% RSD) were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines), V. labruscana (Niagara), and Vitis spp. (Cayuga White). Mean 4-MMP concentrations in New York Niagara (17 ng/L) were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

Allium sativum produces terpenes with fungistatic properties in response to infection with Sclerotium cepivorum

This study investigated terpene biosynthesis in different tissues (root, protobulb, leaf sheath and blade) of in vitro-grown garlic plants either infected or not (control) with Sclerotium cepivorum, the causative agent of Allium White Rot disease. The terpenes identified by gas chromatography–electron impact mass spectrometry (GC-EIMS) in infected plants were nerolidol, phytol, squalene, α-pinene, terpinolene, limonene, 1,8-cineole and γ-terpinene, whose levels significantly increased when exposed to the fungus. Consistent with this, an increase in terpene synthase (TPS) activity was measured in infected plants. Among the terpenes identified, nerolidol, α-pinene and terpinolene were the most abundant with antifungal activity against S. cepivorum being assessed in vitro by mycelium growth inhibition. Nerolidol and terpinolene significantly reduced sclerotia production, while α-pinene stimulated it in a concentration-dependent manner. Parallel to fungal growth inhibition, electron microscopy observations established morphological alterations in the hyphae exposed to terpinolene and nerolidol. Differences in hyphal EtBr uptake suggested that one of the antifungal mechanisms of nerolidol and terpinolene might be disruption of fungal membrane integrity.

Isotopologue ratio normalization for non-targeted metabolomics

Robust quantification of analytes is a prerequisite for meaningful metabolomics experiments. In non-targeted metabolomics it is still hard to compare measurements across multiple batches or instruments. For targeted analyses isotope dilution mass spectrometry is used to provide a robust normalization reference.Here, we present an approach that allows for the automated semi-quantification of metabolites relative to a fully stable isotope-labeled metabolite extract. Unlike many previous approaches, we include both identified and unidentified compounds in the data analysis. The internal standards are detected in an automated manner using the non-targeted tracer fate detection algorithm. The ratios of the light and heavy form of these compounds serve as a robust measure to compare metabolite levels across different mass spectrometric platforms. As opposed to other methods which require high resolution mass spectrometers, our methodology works with low resolution mass spectrometers as commonly used in gas chromatography electron impact mass spectrometry (GC–EI-MS)-based metabolomics.We demonstrate the validity of our method by analyzing compound levels in different samples and show that it outperforms conventional normalization approaches in terms of intra- and inter-instrument reproducibility. We show that a labeled yeast metabolite extract can also serve as a reference for mammalian metabolite extracts where complete stable isotope labeling is hard to achieve.

Solar UV-B radiation modifies the proportion of volatile organic compounds in flowers of field-grown grapevine (Vitis vinifera L.) cv. Malbec

Ultraviolet-B solar radiation (UV-B) is an environmental signal with biological effects in different plant tissues. Recent investigations reported dramatic changes of terpenes with a protective role in plant tissues submitted to biotic and abiotic stresses. This study examined the volatile organic compounds (VOCs) profile in flowers of Vitis vinifera L. cv. Malbec under filtered UV-B (or not). Gas chromatography–electron impact mass spectrometry analysis of flowers resulted in the identification of 12 VOCs, including eight sesquiterpenes, two aldehydes, and two ketones, being the oxygenated sesquiterpene farnesol the most abundant. The total amount of VOCs in flowers did not change irrespective UV-B had been filtered or not, suggesting those compounds have a protective role that is constitutive of the reproductive tissues. However UV-B increases the proportion of valencene, β-farnesene, α-panasinsene and hepatriacontanedione which would require further investigation.

Aquatic photochemistry of diclofenac in the presence of natural dissolved organic chromophoric material and nitrate

Photolysis experiments with diclofenac (DCF) in aqueous solutions under different artificial irradiations were performed to characterise the influence of natural chromophoric dissolved organic material (CDOM) and nitrate ions () on the transformation rate of DCF. The irradiations were carried out by a low-energy UVA–vis (315–400–800 nm) and powerful UVB–uva (280–315–400 nm) lights simulating natural conditions. Alterations of molecular size distributions and optical properties of CDOM after different irradiation intervals were also detected. The kinetic measurements and principal structural determinations of the transformation products were performed by a GC–EI–MS (gas chromatography electron impact mass spectrometry) technique. The capacity of the CDOM for production of •OH radicals or/and different reactive transient oxidants was not enough powerful to initiate the indirect photolysis of the DCF even assisted by ions. As a consequence, the CDOM acts as a quencher reducing the photochemical transformation rate of DCF, and in the applied conditions the phototransformation of DCF takes place alone through direct photolysis even under the UVB–uva radiation. Likewise, the action of ions as photoinductors under the applied conditions was not so significant as usually expected. The kinetic half-life for the phototransformation of DCF was at the best less than one hour corresponding to an apparent quantum yield of 0.097. Structural compositions of detected transformation products were analogous with the conventional ones. The only exception was the formation of a quite UV-resistant carbazole-dione derivative. Irradiation of DCF in pure laboratory water generated practically generated this carbazole-dione derivative solely, thus confirming the photocyclisation as the main phototransformation pathway. However, in the presence of CDOM the main phototransformation pathways were photocyclisation, dehydration, and decarboxylation. It may be that CDOM does not necessarily stimulate pathways but rather decreases the importance of photocyclisation in front of dehydration and decarboxylation competitive pathways. The main photoproducts in the presence of CDOM were: a carbazole-dione derivative, carbazole-1-acetic acid, 1-(2,6-dichlorophenyl)indolin-2-one, and 2-2-(chlorophenylamino)benzaldehyde.

Multistep derivatization method for the determination of multifunctional oxidation products from the reaction of α-pinene with ozone

A novel three-step analytical method was developed which enables the simultaneous detection and identification of multifunctional oxygenated products resulting from the reaction of α-pinene with ozone. The method consists of the following steps: conversion of carbonyl groups to methyloximes using methyloxyamine, conversion of carboxylic acids to methyl esters using trimethylsilyldiazomethane (TMSD), and conversion of alcohols to trimethylsilyl ethers using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The derivatization procedure at each stage was optimized yielding the appropriate amount of derivatization reagent, reaction temperature and time. The newly developed analytical procedure manages without processes of extraction and evaporation to dryness at any stage. Total time for sample analysis is short ca. 3 h. The characteristic ions of derivatives and common pattern for ion fragmentation in capillary gas chromatography electron impact mass spectrometry (GC–EI–MS) analysis were elucidated and discussed.

Dehydration of 2-Methyl-1-cyclohexanol: New Findings from a Popular Undergraduate Laboratory Experiment

The mineral acid-catalyzed dehydration of 2-methyl-1-cyclohexanol has been a popular laboratory exercise in second-year organic chemistry for several decades. The dehydration experiment is often performed by organic chemistry students to illustrate Zaitsev’s rule. However, sensitive analytical techniques reveal that the results do not entirely corroborate with Zaitsev’s rule. Previous reports pertaining to this experiment have been limited by two factors: (i) it is difficult to separate 3- and 4-methyl-1-cyclohexene on a standard gas chromatography (GC) column and (ii) methods of accurate detection, identification, and quantification of trace minor products have been lacking. The current study uses gas chromatography–electron impact mass spectrometry (GC–MS) and quantitative nuclear magnetic resonance (qNMR) to identify and quantify not only the putative 1-, 3-, and 4-methyl-1-cyclohexene products but also several minor products such as methylenecyclohexane and ethylidenecyclopentane. Performing the dehyd...

Measuring Deuterium Enrichment of Glucose Hydrogen Atoms by Gas Chromatography/Mass Spectrometry

We developed a simple and accurate method for determining deuterium enrichment of glucose hydrogen atoms by electron impact gas chromatography mass spectrometry (GC/MS). First, we prepared 18 derivatives of glucose and screened over 200 glucose fragments to evaluate the accuracy and precision of mass isotopomer data for each fragment. We identified three glucose derivatives that gave six analytically useful ions: (1) glucose aldonitrile pentapropionate (m/z 173 derived from C4-C5 bond cleavage; m/z 259 from C3-C4 cleavage; m/z 284 from C4-C5 cleavage; and m/z 370 from C5-C6 cleavage); (2) glucose 1,2,5,6-di-isopropylidene propionate (m/z 301, no cleavage of glucose carbon atoms); and (3) glucose methyloxime pentapropionate (m/z 145 from C2-C3 cleavage). Deuterium enrichment at each carbon position of glucose was determined by least-squares regression of mass isotopomer distributions. The validity of the approach was tested using labeled glucose standards and carefully prepared mixtures of standards. Our method determines deuterium enrichment of glucose hydrogen atoms with an accuracy of 0.3 mol %, or better, without the use of any calibration curves or correction factors. The analysis requires only 20 μL of plasma, which makes the method applicable for studying gluconeogenesis using deuterated water in cell culture and animal experiments.

ANALYSIS AND IDENTIFICATION SPIKING CHEMICAL COMPOUNDS RELATED TO CHEMICAL WEAPON CONVENTION IN UNKNOWN WATER SAMPLES USING GAS CHROMATOGRAPHY AND GAS CHROMATOGRAPHY ELECTRON IONIZATION MASS SPECTROMETRY

The identification and analysis of chemical warfare agents and their degradation products is one of important component for the implementation of the convention. Nowadays, the analytical method for determination chemical warfare agent and their degradation products has been developing and improving. In order to get the sufficient analytical data as recommended by OPCW especially in Proficiency Testing, the spiking chemical compounds related to Chemical Weapon Convention in unknown water sample were determined using two different techniques such as gas chromatography and gas chromatography electron-impact ionization mass spectrometry. Neutral organic extraction, pH 11 organic extraction, cation exchanged-methylation, triethylamine/methanol-silylation were performed to extract the chemical warfare agents from the sample, before analyzing with gas chromatography. The identification of chemical warfare agents was carried out by comparing the mass spectrum of chemicals with mass spectrum reference from the OPCW Central Analytical Database (OCAD) library while the retention indices calculation obtained from gas chromatography analysis was used to get the confirmation and supported data of the chemical warfare agents. Diisopropyl methylphosphonate, 2,2-diphenyl-2-hydroacetic acid and 3-quinuclidinol were found in unknown water sample. Those chemicals were classified in schedule 2 as precursor or reactant of chemical weapons compound in schedule list of Chemical Weapon Convention. Keywords: gas chromatography, mass spectrometry, retention indices, OCAD library, chemical warfare agents

11-Nor-Δ 9-tetrahydrocannabinol-9-carboxylic acid ethyl ester (THC-COOEt): Unsuccessful search for a marker of combined cannabis and alcohol consumption

11-Nor-Δ 9-tetrahydrocannabinol-9-carboxylic acid ethyl ester (THC-COOEt) can be presumed to be a mixed metabolite formed during combined consumption of cannabinoids and alcohol. In order to examine this hypothesis, THC-COOEt and its deuterated analogue D 3-THC-COOEt were synthesized as reference substance and internal standard from the corresponding carboxylic acids and diazoethane and methods were developed for the sensitive detection of THC-COOEt in plasma and hair based on gas chromatography–electron impact mass spectrometry after silylation with N-methyl- N-tert-butyldimethylsilyl-trifluoroacetamide and gas chromatography–negative chemical ionization mass spectrometry (GC-NCI-MS) as well as tandem mass spectrometry (GC-NCI-MS-MS) after derivatization with pentafluoropropionyl anhydride. The methods were applied for THC-COOEt determination to plasma samples from 22 drunk driving cases which contained both ethanol (0.30–2.16 mg/g) and THC-COOH (15–252 ng/mL) as well as to 12 hair samples from drug fatalities which were both positive for THC (0.09–2.04 ng/mg) and fatty acid ethyl esters as markers of chronic alcohol abuse (0.70–6.3 ng/mg). In none of these samples THC-COOEt could be found with limits of detection of 0.3 ng/mL in plasma and 2 pg/mg in hair in 11 samples using GC-NCI-MS and 0.2 pg/mg in one sample using GC-NCI-MS. Therefore, the use of this compound as a marker for combined cannabis and alcohol consumption could not be achieved.

Conversion of a commercial gas chromatography-mass spectrometer to a liquid chromatography-particle beam/glow discharge mass spectrometer

Presented here is the evaluation of working parameters necessary to convert a commercially available HP 5973 MSD gas chromatography electron impact mass spectrometer into a liquid chromatography particle beam glow discharge mass spectrometer (LC-PB/GDMS) system. The initial GC unit was replaced with a commercially available PB interface that allows analysis of liquid samples via electron ionization (EI) mass spectrometry. The original EI source has been removed and replaced with a simple, home-built glow discharge (GD) source, allowing both molecular and elemental information to be obtained simultaneously. Nebulization characteristics were optimized with respect to liquid flow, nebulizer gas, desolvation temperature, and the ability to remove solvent by a two-stage momentum separator. Glow discharge source block temperatures and plasma conditions were optimized relative to the caffeine (test compound) responses. The optimized conditions determined in this study are comparable to work done on a similar type of GDMS in this laboratory. Comparisons of analyte responses for the EI and GD sources with the PB interface reveal caffeine detection limits of 34 and 15 ng mL−1, respectively. The GD and EI mass spectra for caffeine are similar to those of prior work and the NIST mass spectral library. Analytical responses of 100 µL injections varied from 4.7–9.2% RSDs for concentrations of 0.001–250 µg mL−1 of caffeine, creatinine, a tetra-peptide, selenium-methyl-selenocysteine, and Cs and Pb salts. Detection limits were found to be in the ng mL−1 level with absolute masses ranging from 0.24–31.4 ng.