Electron Impact Mode Research Articles

Sweat testing for heroin and metabolites in a heroin maintenance program

Recent advances in sensitive analytical techniques have enabled the analysis of drugs in unconventional biological materials such as sweat. In a study conducted during a heroin maintenance program, 14 subjects had sweat patches applied, then received intravenously two or three doses of heroin hydrochloride ranging from 80 to 1000 mg/day. The sweat patch was applied 10 min before the first dosage and removed approximately 24 h later, minutes before the next dosage. Absorbent pads were stored at -20 degrees C in plastic tubes until analysis. The target drugs were extracted in 5 mL of acetonitrile in the presence of 100 ng each of heroin-d9, 6-acetylmorphine-d3, and morphine-d3. After agitation for 30 min, the acetonitrile solution was divided into two portions: 2 mL for heroin testing and the remainder for testing for the other compounds. After evaporation, the residue of the first portion was reconstituted in 35 microL of acetonitrile; the second was derivatized by silylation with 40 microL of N,O-bis(trimethylsilyl)trifluoroacetamide containing 10 mL/L trimethylchlorosilane. Drugs were analyzed by GC-MS in electron impact mode. Concentrations (nanograms per patch) ranged from 2.1 to 96.3 for heroin, 0 to 24.6 for 6-acetylmorphine, and 0 to 11.2 morphine. Except in one case, heroin was the major drug present in sweat, followed by 6-acetylmorphine and morphine. We observed no correlation between the doses of heroin administered and the concentrations of heroin measured in sweat.

Determination of Sufentanil in Human Plasma by Capillary Electrophoresis and Gas Chromatography–Mass Spectrometry

A fast capillary electrophoretic method and a gas chromatographic - mass spectrometric method were developed for the determination of sufentanil in human plasma. Spiked plasma samples and patient plasma samples were prepared by liquid-liquid extraction. In the capillary electrophoretic analysis, both inorganic and organic buffers were tested with and without surfactants, at various pHs. The final separation with fast analysis time was performed with organic 3–[N-morpholino]propanesulfonic acid solution at pH 7.00, with a bubble cell capillary and UV detection at 195 nm. The gas chromatographic separation was performed without sample derivatization, in a nonpolar column material with fentanyl as the internal standard. The mass spectrometric identification was done in electron impact mode. The limit of detection for sufentanil was lower in the gas chromatographic - mass spectrometric technique than in capillary electrophoresis with UV, therefore more sample was required in the capillary electrophoretic analysis. Comparison of the techniques was done with spiked plasma samples. Both techniques were found to be excellent for the determination of sufentanil. Advantages of the capillary electrophoretic analysis over the gas chromatographic method are better efficiency and the faster elution.

Gas Chromatographic and Mass Spectrometric Purity Analysis of Acrylates and Methacrylates Used as Patch Test Substances

Background: To make a correct diagnosis of allergic contact dermatitis, patch testing needs to be performed, and the patch test substances need to be pure. Objective: We wanted to study how pure commercial (meth)acrylic patch test substances are. Methods: The purity of (meth)acrylic patch test substances (diacrylates, dimethacrylates, and triacrylates) dissolved in acetone was determined by gas chromatography. The impurities were identified by mass spectrometry in both electron impact and chemical ionization mode. Results: The analyzed dimethacrylates were very pure (97% to 99%). The purity of the three studied diacrylates were 81% to 91%, but tripropyleneglycol diacrylate (81% pure) contained as much as 13% of tripropyleneglycol monoacrylate. The purities of the triacrylates were 82% to 86%. All diacrylates and triacrylates contained 1% to 13% of the corresponding hydroxyacrylates. Conclusion: The impurities may result in false interpretation of the patch test results, and accordingly in wrong diagnosis. If the patch test substance is impure, at least, the chemical impurities that can be detected by gas chromatography should be measured and reported in a certificate of analysis, preferably from each batch.

Gas chromatographic and mass spectrometric purity analysis of acrylates and methacrylates used as patch test substances

Background: To make a correct diagnosis of allergic contact dermatitis, patch testing needs to be performed, and the patch test substances need to be pure. Objective: We wanted to study how pure commercial (meth)acrylic patch test substances are. Methods: The purity of (meth)acrylic patch test substances (diacrylates, dimethacrylates, and triacrylates) dissolved in acetone was determined by gas chromatography. The impurities were identified by mass spectrometry in both electron impact and chemical ionization mode. Results: The analyzed dimethacrylates were very pure (97% to 99%). The purity of the three studied diacrylates were 81% to 91%, but tripropyleneglycol diacrylate (81% pure) contained as much as 13% of tripropyleneglycol monoacrylate. The purities of the triacrylates were 82% to 86%. All diacrylates and triacrylates contained 1% to 13% of the corresponding hydroxyacrylates. Conclusion: The impurities may result in false interpretation of the patch test results, and accordingly in wrong diagnosis. If the patch test substance is impure, at least, the chemical impurities that can be detected by gas chromatography should be measured and reported in a certificate of analysis, preferably from each batch.

Semiochemical-Mediated Location of Host Habitat by Apanteles carpatus (Say) (Hymenoptera: Braconidae), a Parasitoid of Clothes Moth Larvae

In Y-tube olfactometer bioassays, adult Apanteles carpatus (Say), were attracted to beaver or rabbit pelts infested with larvae of the casemaking clothes moth (CCM)Tinea pellionella L. Porapak Q-captured volatiles from a CCM-infested beaver pelt were also very attractive, whereas isolated CCM larvae or larval feces were not. Coupled gas chromatographic–electroantennographic detection (GC-EAD) analysis of the Porapak Q volatile extract revealed two compounds that elicited responses by A. carpatus antennae. Coupled GC–mass spectrometry (MS) in electron impact and chemical ionization modes of these compounds indicated, and GC-MS and GC-EAD of authentic standards confirmed, that they were nonanal and geranylacetone. While each compound singly did not attract A. carpatusa 1:1 blend of both compounds was as attractive as the volatile extract. Because these compounds are host habitat-derivedA. carpatus must be a habitat rather than host specialist, responding to kairomonal indicators of localized and specific habitats such as animal hair or feather. The tritrophic interaction between A. carpatusits clothes moth hosts and their animal-derived habitats is similar to the well-studied relationship between parasitoids of insect herbivores and their host plant habitats.

Development of a Method to Identify Keto Acids in Ozonated Fulvic Acid Solutions

A gas chromatographic-mass spectrometric method, combining an O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine–diazomethane double derivatization, was developed to identify major keto acids in ozonated fulvic acid solutions. Three keto acids, glyoxylic, pyruvic, and ketomalonic acid, four aldehydes and two analytical artifacts were identified. The detailed mass spectra, obtained in both electron impact and positive chemical ionization modes, and their fragment assignments are presented. Owing to the similarity of their electron impact mass spectra, electron impact mass spectra along with positive chemical ionization mass spectra are needed to identify these keto acids reliably. The effects of the formation of keto acids on water quality are also discussed. © 1997 by John Wiley & Sons, Ltd.

Use of Chemical Ionization in Multianalysis Gas and Liquid Chromatography Combined With a Single Mass Spectrometer for the Ultra-trace Level Determination of Microcontaminants in Aqueous Samples†

An automated system that comprises a single mass spectrometer (MS) in combination with gas (GC) and liquid chromatography [LC; particle beam (PB) interface] has been used for the trace-level detection and identification of contaminants in water samples. The analytes were enriched by on-line solid-phase extraction (SPE). In the present study, the potential of negative chemical ionization (NCI) detection in this so-called multianalysis system was explored. Attention was devoted to the enhancement of selectivity and sensitivity as well as to the additional spectral information obtained for the identification of unknown compounds.Nine chlorinated pesticides representing three major groups, i.e., triazines, anilides and organophosphorus pesticides, were used as test compounds. Among the three reagent gases used for NCI, isobutane, methane and ammonia, methane gave the best results. For six of the nine pesticides, a 3- to 30-fold increase in sensitivity was observed in the NCI mode as compared with the electron impact (EI) mode. As expected, the NCI mass spectra showed little fragmentation. Electron capture appears to be the dominant ionization mechanism.In order to study the potential of the total on-line SPE–LC/GC–MS set-up, the pesticides were spiked to tap and surface water samples. The detection limits obtained in the NCI (full-scan) mode ranged from 0.1–3 ng l–1 for GC–MS and 50 to 200 ng l–1 for LC–PB–MS for 100-ml tap water samples. The potential of NCI–MS was demonstrated by the identification of several unknown microcontaminants in a river water sample.

Experience with hair testing in the clinical biochemistry laboratory of Ca' Granda Niguarda Hospital, Milan, Italy

In our laboratory, analysis of human hair for drugs of abuse detection was first performed in 1980. In the last 10 years we have processed about 2000 subjects/year (‘living subjects’ only). In the last 3 years we have also introduced hair analysis of cocaine: at first only in clinical applications, but for the last 2 years this analysis is now routine. Our application of hair analysis includes: clinical toxicology, medico-legal and administrative agencies. Requests come for example from several Committees for Driving Licenses, Addiction Treatment Centers and Legal Authorities. Hair samples are currently collected from the occipital area at the back of the head, which appears to show less variability in hair growth rate. At present we perform hair analysis using highly sensitive radioimmunoassay screening methods for the detection of parent drug and/or metabolites. All positive cases of cocaine and opiates abuse are confirmed by gas chromatography-mass spectrometry in electron impact or chemical ionization mode. Positive cases for opiates are also analysed using a specific morphine radioimmunoassay kit. Data show that, when the opiates/morphine ratio is higher than 6, we are dealing with consumption of codeine and/or dihydrocodeine. In our routine work last year there were 177 (263 samples) positive opiates subjects out of 2244 patients; positive cocaine subjects were 290 (362 samples) out of 2001 patients.Guidelines for hair analysis in Lombardia have been established based on the experience of our laboratory. Furthermore it will be possible to apply a unique protocol for all Committees for Driving Licenses, involving hair testing in addition to urine assay.

Distinguishing Amphetamine, Methamphetamine and 3,4-Methylenedioxymethamphetamine from Other Sympathomimetic Amines After Rapid Derivatization with Propyl Chloroformate and Analysis by Gas Chromatography—Chemical Ionization Mass Spectrometry

Abstract Misidentification of ephedrine and pseudoephedrine as methamphetamine has been reported because of similar retention times of their derivatives in gas chromatography as well as very similar mass spectral fragmentation patterns in the conventional electron impact mode of analysis. Recently, a new derivatization of amphetamine and methamphetamine has been described using propyl chloroformate. The derivatization is easily accomplished at room temperature by adding the derivatizing reagent in the extraction solvent because the reagent is stable in the presence of water. The electron impact mass spectrum of derivatized methamphetamine (base peak, m/z 144, other peaks at m/z 102, 58) is similar to the electron impact mass spectrum of both derivatized pseudoephedrine (base peak, m/z 144, other peaks, m/z 102, 58), and ephedrine (base peak, m/z 144, other peaks, m/z 102, 58). Therefore, misidentification of ephedrine and pseudoephedrine as methamphetamine is possible even if this new derivatization technique is used with conventional gas chromatography/electron impact mass spectrometry. We demonstrated that by using chemical ionization mass spectrometry, this problem can be eliminated. In the chemical ionization, using methane as a reagent gas, derivatized methamphetamine showed a protonated molecular ion as a base peak at m/z 236 and other strong peaks at m/z 144 and 119, both derivatized ephedrine and pseudoephedrine showed a base peak at m/z 192 and another strong peak at m/z 148, thus differentiating them clearly from methamphetamine. Amphetamine also showed a protonated molecular ion at m/z 222 and other strong peaks at m/z 130 and 119, whereas phenylpropanolamine after derivatization with propyl chloroformate showed a base peak at m/z 220 and another strong peak at m/z 238, thus differentiating it from amphetamine. The designer drug 3,4-methylenedioxymethamphetamine (MDMA) showed a molecular ion at m/z 279 using electron impact, after derivatization with propyl chloroformate. Using chemical ionization, a relatively stronger protonated molecular ion at m/z 280 was observed. We conclude that using chemical ionization instead of conventional electron impact and propyl chloroformate derivatization, misidentification of ephedrine or pseudoephedrine as methamphetamine or phenylpropanolamine as amphetamine can be eliminated.

Analysis of methylhexahydrophthalic acid in human urine

A method for analysis of urinary methylhexahydrophthalic acid (MHHP acid), a metabolite of the highly sensitising methylhexahydrophthalic anhydride, is described. The method is based on a double liquid-solid extraction of the MHHP acid from urine, esterification with methanol and boron trifluoride catalysis, and analysis with gas chromatography-mass spectrometry in the electron impact mode. The detection limit was 3 ng mL−1 and the precision between 2 and 5% in the range 34 to 340 ng mL−1. The method gave similar results compared to another method. Urine stored for five years at −20°C lost between 38 and 86% of the MHHP acid (range 16–85 ng mL−1).

Optimization of a matrix solid-phase dispersion method for the analysis of pesticide residues in vegetables

A multiresidue method based on matrix solid-phase dispersion (MSPD) is studied to determine chlorfenvinfos, chlorpyrifos, fenarimol, iprodione, procimydone, propiconazole, tetradifon, triadimefon and vinclozolin in artichokes, green beans, lettuces and tomatoes. Alumina, silica and Florisil were assessed as extracting phases, and the extracts from Florisil were the cleanest. To facilitate manual extraction, sand was added to the sample together with the dispersing phase. Three eluting systems were then studied, and dichloromethane proved to be the best. Further purification can be performed using solid-phase cleanup after diluting extracts with acqueous solutions. Octyl- and octadecyl-silica, modifications of the aqueous diluted extracts and several eluting solvents were studied. Determination was done by capillary gas chromatography (GC) with electron-capture detection, and confirmed by GC-MS using the electron impact mode and the selected ion monitoring. The proposed MSPD method was used to analyze 48 samples taken in the course of a year. Procymidone, vinclozolin, chlorpyrifos and chlorfenvinfos were identified in 10 samples at levels below the maximum residue levels allowed by the Spanish Government.

Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and 5,6-dihydro-5-fluorouracil in plasma by gas chromatography-mass spectrometry

A gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of 5′-deoxy-5-fluorouridine (doxifluridine, 5′-dFUR), 5-fluorouracil (5-FU) and its main catabolite 5,6-dihydro-5-fluorouracil (5-FUH 2) in human plasma has been developed. Sample preparation consisted of protein precipitation with ammonium sulphate followed by analyte extraction with ethyl acetate/isopropanol ( 90 10 , v/v) mixture. Extracts were then analysed by GC-MS in positive electron impact mode after derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide/pyridine ( 1 1 , v/v). The trimethylsilyl (TMS) derivative of 5′-dFUR was proved to be stable so that no interference in 5-FU determination was observed. Mass spectra of TMS derivatives of 5′-dFUR, 5-FU and 5-FUH 2 are discussed. Analyte response was linear over two decades of concentration and detection limits were typically 20 ng/ml of plasma.

Characterization of phenolic and secoiridoid aglycons present in virgin olive oil by gas chromatography-chemical ionization mass spectrometry

Olive oil phenolic and secoiridoid compound derivatives were detected by mass spectrometry. Chemical ionization (CI) allowed us to obtain parent ions, that were not detectable in the electron impact mode. CI experiments were performed using either CH 4 or NH 3 as the reactant gas. Unlike CH 4-CI, which fails to give molecular mass information, NH 3-CI provided, in all the cases explored, an adduct ion [M+18] + that was sufficiently stable to be detected and recorded. Information about molecular masses was very useful for the complete characterization of aglycons from glycosides occurring in virgin olive oils. Aglycons of ligstroside, of decarbomethoxyoleuropein and of oleuropein were detected. Each aglycon, because of several tautomeric equilibria involving the ring opening of secoiridoid, showed up as compounds with four main structures after derivatization with bis(trimethylsilyl)trifluoracetamide.

Synthesis and GC-MS of 6-Alkylestradiols, Possible Aromatase Reaction Products of 6-Alkylandrostenediones.

A series of 6α- and 6β-alkylestradiols (5 and 6) (alkyl : methyl, ethyl, n-propyl, n-pentyl, and n-heptyl) were synthesized as possible aromatase reaction products of 6-alkylandrost-4-ene-3, 17-diones and their Δ1-derivatives, potent competitive and mechanism-based inhibitors of aromatase. Treatment of 6-oxoestradiol with Grignard reagents followed by acid-catalyzed dehydration and subsequent catalytic hydrogenation over Pd-C gave the 6-alkylestradiols (5 and 6). GC-MS (electron impact mode) of trimethylsilyl derivatives of bis-trimethylsilyl derivatives of compounds 5 and 6 revealed that the 6α-alkyl compounds, 5, emerged with a longer retention time compared to the corresponding 6β-alkyl isomers, 6, where the retention time was in proportion to the length of the 6-alkyl chain in each series. In the MS, a molecular ion (M+) peak was the base peak for all the 6-alkylestrogens, with strong and characteristic fragment ion peaks corresponding to M+-131 and at m/z 325. A selected ion monitoring method using a molecular ion will be sensitive enough for analysis of the aromatization reaction of the 6-alkylandrogens.

Comparisons between electron impact and fast atom bombardment mass spectra of some triphenylphosphonium and triphenylarsonium salts

The electron impact (EI) mass spectra of alkyltriphenylphosphonium and alkyltriphenylarsonium salts were compared with fast atom bombardment (FAB) mass spectra in a 3-nitrobenzyl alcohol matrix. It is clearly demonstrated that FAB is an effective ionization method compared with EI for analysis of these non-volatile and thermally labile compounds, particularly triphenylarsonium salts. In FABMS, the spectra generally show the intact cations (C+) as the base peaks, in addition to the singly charged cluster ions (C2A)+. High-resolution mass spectrometry was used to determine the elemental composition of the ions at m/z 277 for some phosphonium salts in the EI mode and the results show that the formation of (O(double bond)PPh3 − 1)+ (m/z 277) involves an oxygen rearrangement as a possible reaction pathway. B/E linked scans of the intact cations of triphenylarsonium salts generated by FABMS were studied in detail both to illustrate the dissociation pathways and to compare the reaction mechanism with that occurring for triphenylphosphonium salts.

Testing human hair for Cannabis. III. rapid screening procedure for the simultaneous identification of delta 9-tetrahydrocannabinol, cannabinol, and cannabidiol.

delta 9-Tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN) are three constituents of the 16 that can be currently isolated from some Cannabis spp plants. Their identification in decontaminated hair can indicate exposure to cannabis. In this study, we propose a rapid, simple, and direct (without derivatization) screening procedure for the simultaneous identification and quantitation of CBD, CBN, and THC in hair of chronic cannabis abusers. Hair samples were washed with methylene chloride, hydrolyzed with sodium hydroxide, extracted with n-hexane-ethyl acetate (9:1, v/v), evaporated to dryness, and injected directly on a gas chromatographic-mass spectrometric system operating in electron-impact mode. THC-d3 was used as the internal standard. Thirty hair samples were tested. CBD was detected 23 times, CBN was detected 22 times, and THC was detected five times. Concentrations ranged from 0.03 to 3.00 ng/mg (mean, 0.44 ng/mg), from 0.01 to 1.07 ng/mg (mean, 0.13 ng/mg), and from 0.1 to 0.29 ng/mg hair (mean, 0.15 ng/mg) for CBD, CBN, and THC, respectively. These results show that this new screening procedure is suitable for the detection of CBD and CBN in the hair of cannabis abusers.

Determination of s-Triazine Metabolites: A Mass Spectrometric Investigation

The s-triazine herbicides have highly polar metabolites that often cannot be analyzed directly by gas chromatography−mass spectrometry (GC-MS). Chemical derivatization may be necessary to improve identification and quantitative analytical methods. The analysis of eight suspected metabolites of two s-triazine herbicides, atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and ametryn [2-(methylthio)-4-(ethylamino)-6-(isopropylamino)-s-triazine], was performed in the electron-impact mode by direct inlet system−mass spectrometry (DIS-MS) and by GC-MS, after sample derivatization. So far, previous derivatization procedures were either difficult or yielded a mixture of derivatives. By using N-methylbis[trifluoroacetamide] (MBTFA), we obtained only one derivative of each metabolite, and the method easily detected microbial degradation-derived metabolites. Moreover, we identified some frequently present ions that can be used in the analysis of complex samples. Keywords: Atrazine; ametryn; herbicides...

Analysis of water-soluble vitamins by high-performance liquid chromatography–particle beam-mass spectrometry

Particle beam (PB) LC–MS was investigated for the analysis of eleven water-soluble vitamins. A reversed-phase chromatographic method making use of volatile buffers was set up for the simultaneous separation of this mixture by using narrow-bore columns. After optimization of the PB interface parameters, the effect of the MS source temperature was evaluated at 200 °C and 300 °C in electron impact (EI) and chemical ionization (positive-ion, PCI and negative-ion, NCI) modes. Electron impact mass spectra were library-searchable, but generally sensitivity was better under PCI conditions. Under these conditions and operating in selected-ion monitoring mode, linearity, detection limits and precision of the analysis was explored. Detection limits at the low-ng level were achieved for nicotinamide, nicotinic acid in PCI mode and pyridoxal under NCI conditions; repeatability of <6%(RSD) was obtained for all the compounds examined except for biotin.

On-line solid-phase extraction–liquid chromatography–particle beam mass spectrometry and gas chromatography–mass spectrometry of carbamate pesticides

On-line solid-phase extraction–liquid chromatography–particle beam mass spectrometry (SPE–LC–PB-MS) was used to study 32 carbamates and 11 of their transformation products in environmental water samples. The analytes were enriched from 100 ml samples on Bondesil-C18/OH, packed in a 10 mm × 3.0 mm id precolumn, eluted on-line with a gradient of methanol–0.1 mol l–1 ammonium acetate to a C18 analytical column and detected by PB-MS. Detection limits of 12 carbamates and five degradation products were 0.1–8 µg l–1 in surface water, using full-scan electron impact mode detection. The RSDs of the retention times were 0.05–0.2% and those of peak areas 5–35%. Twenty-eight analytes proved to be amenable to GC with detection limits of 0.05–3 ng injected on-column. When using the same mass spectrometer, the spectra obtained by LC–PB-MS and GC–MS were identical.

Capillary GC‐MS investigation of the metabolism and excretion of oxabolone in man

AbstractThe metabolism of oxabolone cipionate, 17‐(3‐cyclopentyl‐1‐oxopropoxy)‐4‐hydroxyestr‐4‐en‐3‐one, a synthetic anabolic steroid, was investigated in man, the cumulative urinary excretion and the metabolism of the compounds being studied by GC‐MS in both electron impact and chemical ionization modes. After administration by injection to volunteers, five different metabolities were detected in urine. The metabolites and the parent compound were detected in urine up to a week after administration.