Chemical Ionization Gas Chromatography-mass Spectrometry Research Articles

Distribution and Sensory Impact of (2E,4E,6Z)-nonatrienal and Trans-4,5-epoxy-(E)-2-decenal in Wines and Spirits.

This study reports the distribution of (2E,4E,6Z)-nonatrienal (1) and trans-4,5-epoxy-(E)-2-decenal (2) in wines and spirits. We validated a quantification method using solid-phase extraction (SPE) and negative chemical ionization (NCI, NH3) gas chromatography-mass spectrometry (GC-MS) analysis. Both were identified for the first time in wines and spirits from different grape varieties and raw materials. Their olfactory detection thresholds (ODTs) were 16 and 60 ng/L, respectively. Analysis of 66 wines showed that the highest levels of (1) (441.3 ng/L) and (2) (386.5 ng/L) were found in red and white wines, respectively. At these levels, they modify the balance of the fruity expression of red (fresh to cooked fruits) and white (vegetal/green hazelnut nuance) wines. Similar quantitative and sensory analyses were conducted in spirits. With ODT estimated at 500 and 400 ng/L and concentrations ranging from trace amounts to 1.1 and 2.4 μg/L respectively, (1) and (2) can contribute directly to the aroma of spirits.

Estimates of the Effect of Feeding on Whole-Body Protein Degradation in Women Vary with the Amino Acid Used as Tracer

We measured how feeding status affects the kinetics of multiple indispensable amino acids in four adult female subjects studied both in fed and fasted state. The subjects ingested one dose of uniformly 13C-labeled algae (Spirulina platensis). The isotopic enrichments (measured with negative chemical ionization gas chromatography-mass spectrometry) of the branched chain amino acids, phenylalanine, lysine and threonine were followed for 24 h in both the plasma and in VLDL-apolipoprotein B-100 (apoB-100). Fasting lowered body protein degradation when measured with the branched chain amino acids, increased it when measured with phenylalanine and had no statistically significant effect when determined from the kinetics of lysine and threonine. These apparent differences challenge the adequacy of current models of whole-body protein turnover. The ratio of the peak labeling of amino acids in plasma and apoB-100 was used as an estimate of the isotopic dilution in the hepatic pool. In contrast to our earlier observations during intravenous tracer amino acid administration, in the present study fasting lowered the ratio of the peak isotopic enrichments of apoB-100 and plasma amino acids. This supports our contention that feeding increases the use of hepatic portal amino acids for hepatic secretory protein synthesis.

Nitrogen carrier gas for the separation of trace explosives on CI-GC/MS.

Fluctuations in ultra high purity (UHP) helium supply has the potential to negatively impact critical research efforts. Disruptions have increased significantly with suppliers prioritizing delivery to medical facilities. Due to the greater demand for helium, supply issues are likely to continue through the coming years. Many gas chromatography (GC)-based analytical methods rely on the supply of UHP helium, including those developed for the quantification of trace explosives. Vapor validation is critical in establishing sensor performance, limits of detection, and instrument performance. An alternate carrier gas must be established to maintain these critical functionalities. To circumvent the UHP helium disruptions, UHP nitrogen was explored as a replacement carrier gas in negative mode chemical ionization-gas chromatography/mass spectrometry (CI-GC/MS). Although, hydrogen is considered an acceptable alternative to helium in most GC-based separations, its' use as a replacement was omitted due to reactivity resulting in degradation of the CI-MS detector and incompatibility with the programmable temperature vaporization inlet on the GC used in this work. Herein discusses the method development of nitrogen carrier gas in the separation of an explosives mixture. Adjustments in flow rate, initial oven temperature, and ramp rate were made to achieve comparable analysis to that of helium. By lowering the flow rate and initial oven temperature peak resolution and sensitivity increased when using nitrogen carrier gas. Development of this method allows for continual laboratory output in times of helium scarcity.

Unusual Derivatization of Methylmalonic Acid with Pentafluorobenzyl Bromide to a Tripentafluorobenzyl Derivative and Its Stable-Isotope Dilution GC-MS Measurement in Human Urine.

Methylmalonic acid (MMA) is a very short dicarboxylic acid (methylpropanedioic acid; CH3CH(COOH)2; pKa1, 3.07; pKa2, 5.76) associated with vitamin B12 deficiency and many other patho-physiological conditions. In this work, we investigated several carboxylic groups-specific derivatization reactions and tested their utility for the quantitative analysis of MMA in human urine and plasma by gas chromatography-mass spectrometry (GC-MS). The most useful derivatization procedure was the reaction of unlabeled MMA (d0-MMA) and trideutero-methyl malonic acid (d3-MMA) with 2,3,4,5,6-pentafluorobenzyl bromide (PFB-Br) in acetone. By heating at 80 °C for 60 min, we observed the formation of the dipentafluorobenzyl (PFB) ester of MMA (CH3CH(COOPFB)2). In the presence of N,N-diisopropylamine, heating at 80 °C for 60 min resulted in the formation of a tripentafluorobenzyl derivative of MMA, i.e., CH3CPFB(COOPFB)2). The retention time was 5.6 min for CH3CH(COOPFB)2 and 7.3 min for CH3CPFB(COOPFB)2). The most intense ions in the negative-ion chemical ionization (NICI) GC-MS spectra of CH3CH(COOPFB)2 were mass-to-charge (m/z) 233 for d0-MMA and m/z 236 for d3-MMA. The most intense ions in the NICI GC-MS spectra of CH3CPFB(COOPFB)2 were mass-to-charge (m/z) 349 for d0-MMA and m/z 352 for d3-MMA. These results indicate that the H at C atom at position 2 is C-H acidic and is alkylated by PFB-Br only in the presence of the base N,N-diisopropylamine. Method validation and quantitative analyses in human urine and plasma were performed by selected ion monitoring (SIM) of m/z 349 for d0-MMA and m/z 352 for the internal standard d3-MMA in the NICI mode. We used the method to measure the urinary excretion rates of MMA in healthy black (n = 39) and white (n = 41) boys of the Arterial Stiffness in Offspring Study (ASOS). The creatinine-corrected excretion rates of MMA were 1.50 [0.85–2.52] µmol/mmol in the black boys and 1.34 [1.02–2.18] µmol/mmol in the white boys (P = 0.85; Mann–Whitney). The derivatization procedure is highly specific and sensitive for MMA and allows its accurate and precise measurement in 10-µl of human urine by GC-MS.

An Arabidopsis GCMS chemical ionization technique to quantify adaptive responses in central metabolism.

We present a methodology to survey central metabolism in 13CO2-labeled Arabidopsis (Arabidopsis thaliana) rosettes by ammonia positive chemical ionization-gas chromatography-mass spectrometry. This technique preserves the molecular ion cluster of methyloxime/trimethylsilyl-derivatized analytes up to 1 kDa, providing unambiguous nominal mass assignment of >200 central metabolites and 13C incorporation rates into a subset of 111 from the tricarboxylic acid (TCA) cycle, photorespiratory pathway, amino acid metabolism, shikimate pathway, and lipid and sugar metabolism. In short-term labeling assays, we observed plateau labeling of ∼35% for intermediates of the photorespiratory cycle except for glyoxylate, which reached only ∼4% labeling and was also present at molar concentrations several fold lower than other photorespiratory intermediates. This suggests photorespiratory flux may involve alternate intermediate pools besides the generally accepted route through glyoxylate. Untargeted scans showed that in illuminated leaves, noncyclic TCA cycle flux and citrate export to the cytosol revert to a cyclic flux mode following methyl jasmonate (MJ) treatment. MJ also caused a block in the photorespiratory transamination of glyoxylate to glycine. Salicylic acid treatment induced the opposite effects in both cases, indicating the antagonistic relationship of these defense signaling hormones is preserved at the metabolome level. We provide complete chemical ionization spectra for 203 Arabidopsis metabolites from central metabolism, which uniformly feature the unfragmented pseudomolecular ion as the base peak. This unbiased, soft ionization technique is a powerful screening tool to identify adaptive metabolic trends in photosynthetic tissue and represents an important advance in methodology to measure plant metabolic flux.

Mass-Labeled Fluorotelomer Alcohol Fragmentation Gives "False Positive" for Nonlabeled Fluorotelomer Alcohols with Implications for Consumer Product Analysis.

Volatile per- and polyfluoroalkyl substances (PFAS) are detected in various consumer goods, raising concerns over environmental fate and human exposure. Volatile PFAS are commonly analyzed by gas chromatography-chemical ionization-mass spectrometry. Mass-labeled standards are used for quantitative analysis of volatile PFAS and to ensure quality control. However, mass-labeled fluorotelomer alcohol (FTOH) analyzed in positive chemical ionization produces signals corresponding to nonlabeled (native) FTOH ions, resulting in false positives. This observation was attributed to deuterium or hydrogen abstraction of mass-labeled standards. Deuterium abstraction of deuterated standards, including d4-4:2 FTOH, 13C2-d2-6:2 FTOH, 13C2-d2-10:2 FTOH, and hydrogen abstraction of 13C-labeled standard 13C2-8:2 FTOH are ionization artifacts that yielded responses for native FTOH m/z values. False positives for native (nonlabeled) FTOHs caused by the introduction of a mass-labeled surrogate can be controlled by blank subtracting or decreasing mass-labeled standard concentrations. Alternatively, different mass-labeled standards can also be used in sample analysis.

Stereoselectivity in Atmospheric Autoxidation

We show that the diastereomers of hydroxy peroxy radicals formed from OH and O2 addition to C2 and C3, respectively, of crotonaldehyde (CH3CHCHCHO) undergo gas-phase unimolecular aldehydic hydrogen shift (H-shift) chemistry with rate coefficients that differ by an order of magnitude. The stereospecificity observed here for crotonaldehyde is general and will lead to a significant diastereomeric-specific chemistry in the atmosphere. This enhancement of specific stereoisomers by stereoselective gas-phase reactions could have widespread implications given the ubiquity of chirality in nature. The H-shift rate coefficients calculated using multiconformer transition state theory (MC-TST) agree with those determined experimentally using stereoisomer-specific gas-chromatography chemical ionization mass spectroscopy (GC-CIMS) measurements.

Determination of organo-tin residues in edible vegetable oil by positive chemical ionization-gas chromatography-mass spectrometry

For the determination of organo-tin residues in edible vegetable oil, a method was developed based on gas chromatography-mass spectrometric (GC-MS) with positive chemical ionization (PCI). The edible oil samples were first dissolved by cyclohexane-ethyl acetate (1:1, v/v), and then purified by gel permeation chromatography (GPC). After derivatization by sodium tetraethylborate, the samples were analyzed by GC-MS with PCI source in the single ion monitor (SIM) mode. The seven organo-tin compounds showed good linear relationships in the range of 20-2000 μg/L and the correlation coefficients exceeded 0.99. The limits of quantitation (LOQs) and the average recoveries of the seven organo-tin compounds were 0.3-1.2 μg/kg and 66.2%-103.2%, respectively, and the relative standard deviations were less than 11.5% at three spike levels (0.05, 0.10, and 0.20 mg/kg). The method showed good linearity and high sensitivity and can be used for the determination of organo-tin residues in edible vegetable oil.

Rapid analysis of sulfur mustard oxide in plasma using gas chromatography-chemical ionization-mass spectrometry for diagnosis of sulfur mustard exposure

Sulfur mustard (SM) is the most utilized chemical warfare agent in modern history and has caused more casualties than all other chemical weapons combined. SM still poses a threat to civilians globally because of existing stockpiles and ease of production. Exposure to SM causes irritation to the eyes and blistering of skin and respiratory tract. These clinical signs of exposure to SM can take 6–24 h to appear. Therefore, analyzing biomarkers of SM from biological specimens collected from suspected victims is necessary for diagnosis during this latent period. Here, we report a rapid, simple, and direct quantitative analytical method for an important and early SM biomarker, sulfur mustard oxide (SMO). The method includes addition of a stable isotope labeled internal standard, SMO extraction directly into dichloromethane (DCM), rapid drying and reconstitution of the extract, and direct analysis of SMO using gas chromatography-chemical ionization-mass spectrometry. The limit of detection of the method was 0.1 μM, with a linear range from 0.5 to 100 μM. Method selectivity, matrix effect, recovery, and short-term stability were also evaluated. Furthermore, the applicability of the method was tested by analyzing samples from inhalation exposure studies performed in swine. The method was able to detect SMO from 100% of the exposed swine (N = 9), with no interferences present in the plasma of the same swine prior to exposure. The method presented here is the first of its kind to allow for easy and rapid diagnosis of SM poisoning (sample analysis <15 min), especially important during the asymptomatic latency period.

Qualitative and quantitative analysis of chemicals emitted from the pheromone gland of individual Heliothis subflexa females.

The chemicals emitted from the sex pheromone gland of individual Heliothis subflexa females were sampled using a short section of thick-film megabore fused silica capillary column, and the pheromone glands of the same females were extracted after the effluvia collection. Both samples were treated with a silylation reagent, and then subjected to gas chromatography-chemical ionization-mass spectrometry for quantitative and qualitative analysis of all components. The total amount of all 11 components emitted from the glands of calling females was 153 ng/female/hr, which was substantially higher than previously reported. The ratios of the pheromone components in the volatile emissions and pheromone gland extracts were generally similar to previous studies, but with notable differences. The collections of volatiles and gland extractions contained, respectively: Z9-14:Ald (1.57%, 1.35%), 14:Ald (3.78%, 1.51%), Z7 + Z9-16:Ald (9.60%, 3.59%), Z11-16:Ald (76.14%, 18.94%), 16:Ald (2.95%, 2.17%), Z9-16:OH (0.07%, 7.21%), Z11-16:OH (1.11%, 49.04%), Z7-16:OAc (0.48%, 1.73%), Z9-16:OAc (1.32%, 4.02%), and Z11-16:OAc (2.98%, 10.43%). The thick-film megabore column is an efficient approach for sampling the headspace for semiochemicals.

Peanut butter increases the bioavailability and bioconversion of kale β-carotene to vitamin A.

Kale is a rich source of provitamin A- β-carotene. This study used intrinsically labeled kale [2H9] β-carotene to determine the effect of peanut butter on the bioconversion of kale β-carotene to vitamin A in preschool children. Preschool children (n=37; age 12-36 mo) were randomly assigned to 50 g cooked kale (1.5 mg β-carotene content) with either 33 g peanut butter (PBG) or with 16 g lard (LG) and a reference dose of 1 mg [13C10] retinyl acetate capsule. Blood samples were processed to serum and analyzed by Negative Chemical Ionization-Gas Chromatography Mass Spectrometry (NCI-GCMS) for the enrichments of [2H] retinol from kale [2H9] β-carotene and [13C10] retinol from reference dose. The area under curves (AUCs) of molar enrichment at days 1, 2, 3, 6, 15, and 21 after the labeled doses was 56.3±10.5 and 84.8±16.2 (nmole) for [2H] retinol from LG and PBG kale [2H9] β-carotene, respectively. The AUC of [13C10] retinol from reference dose was 432.6±54.9 (LG) and 560.3±156.7 (nmole) (PBG), respectively. The calculated β-carotene conversion factors were 13.4±3.1 and 11.0±3.9 to 1 (p>0.05) by weight for LG and PBG, respectively. This study showed that peanut butter enhances the vitamin A value of kale.

Structure determination of organic aging products in lithium-ion battery electrolytes with gas chromatography chemical ionization mass spectrometry (GC-CI-MS)

For Gas Chromatography Chemical Ionization Mass Spectrometry (GC-CI-MS) method development, a standard lithium-ion battery (LIB) electrolyte was thermally aged at 95 °C for a faster generation of decomposition products.

A methodological approach to the selection of liquid reagents for chemical ionization ion trap-gas chromatography mass spectrometry: A case study of GBL and 1,4-BD

A new approach is proposed for the selection of reagent ion species in a gas chromatography-chemical ionization mass spectrometry (GC-PICI-MS) method for GBL and 1,4-BD determination, the two “prodrugs” of gamma-hydroxybutyric acid (GHB), a drug associated with sexual assault. The GC-PICI-MS is often the best technique to avoid an extended fragmentation occurring in EI source and it preserves the information on molecular ions. Ion-trap mass spectrometry (IT-MS) is a valuable tool in chemical ionization experiments, commonly affording reaction times 104–105 higher than those in conventional CI sources. This feature allows the use of either vapors from liquid reagents, or many reactant species that are difficult to generate and employ in the conventional CI experiments. In this research acetone, acetonitrile, methanol and diethylamine were evaluated to generate vapors of the chemical ionization species. The use of liquid CI reagent offers a wide range of chemical–physical properties that can greatly affect the specificity, with the possibility to modulate the detection of the analyte in comparison with background or matrix interferences. The experimental data using different CI liquid reagents and reaction times were compared through calibration curves of GBL and 1,4-BD (ranging from 10 to 1000ng/mL). The linear regression curves obtained were used to calculate the sensitivity (slope) and limit of detection (LOD) of the method. Methanol resulted in the most efficient reagent for the determination of studied analytes. However, its employment as ionization agent of the 1,4-BD favors the hydride abstraction mechanism or hydrogen loss from protonated-molecule ions. These phenomena can be considered as a possible sources of uncertainty or errors. Therefore, acetonitrile can be employed as a good compromise between sensitivity and reliability of signal for both analytes.

Determination of N-nitrosamines in processed meats by liquid extraction combined with gas chromatography-methanol chemical ionisation/mass spectrometry

A simple, accessible and reproducible method was developed and validated as an alternative for the determination of nine volatile N-nitrosamines (NAs) in meat products, using a low volume of organic solvent and without requiring specific apparatus, offering the possibility of practical implementation in routine laboratories. The NAs were extracted with dichloromethane followed by a clean-up with phosphate buffer solution (pH 7.0). The extracts were analysed by gas chromatography-chemical ionisation/mass spectrometry (GC-CI/MS) in positive-ion mode using methanol as reagent. Limits of detection and quantification, recovery and reproducibility were determined for all NAs (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine, N-nitrosodipropylamine, N-nitrosomorpholine, N-nitrosopiperidine, N-nitrosodibutylamine and N-nitrosodiphenylamine). Satisfactory sensitivity and selectivity were obtained even without concentrating the extract by solvent evaporation, avoiding the loss of the nine NAs studied. Limits of detection ranged from 0.15 to 0.37 µg kg−1, whereas limits of quantification ranged from 0.50 to 1.24 µg kg−1. Recoveries calculated in cooked ham that had been spiked at 10 and 100 µg kg−1 were found to be between 70% and 114% with an average relative standard deviation of 13.2%. The method was successfully used to analyse five samples of processed meat products on the day of purchase and 7 days later (after storage at 4°C). The most abundant NAs found in the analysed products were N-nitrosodipropylamine and N-nitrosopiperidine, which ranged from 1.75 to 34.75 µg kg−1 and from 1.50 to 4.26 µg kg−1, respectively. In general, an increase in the level of NAs was observed after the storage period. The proposed method may therefore be a useful tool for food safety control once it allows assessing the profile and the dietary intake of NAs in food over time.

Trans-octadecenoic Acid Positional Isomers Have Different Accumulation and Catabolism Properties in Mice.

Trans fatty acids (TFA) are considered risk factors for cardiovascular disease (CVD), while the details of distribution and metabolism of the individual isomers are not clear. Here we investigated the accumulation and catabolic rate of TFA positional isomers of octadecenoic acid (18:1) in mice. ICR mice were fed deuterium- and [1-(13)C] stable isotope-labeled trans-9-18:1 (9t-18:1*), trans-10-18:1 (10t-18:1*), or trans-11-18:1 (11t-18:1*) for 2 or 4 weeks, or a TFA mixture (9t-18:1*, 10t-18:1*, and 11t-18:1*) for 3 weeks. Analysis of whole-body tissues by gas chromatography-chemical ionization mass spectrometry revealed the highest 9t-18:1* levels in the heart. Significant differences in the accumulation of the respective trans-18:1 were observed in the heart and erythrocytes, where 9t- > 11t- > 10t-18:1*, but no significant difference was observed in the liver or white adipose tissue (WAT). Mice fed on 11t-18:1 demonstrated accumulation of endogenously synthesized conjugated linoleic acid in the liver, WAT, and heart, but any other metabolites were not found in other groups. Furthermore, we analyzed catabolic rates of single-dose-administered trans-18:1* isomers into [(13)C]-labeled CO2 using isotope-ratio mass spectrometry, and the 10t-18:1*catabolic rate was significantly higher than those of 9t- and 11t-18:1*. We found that the accumulation and catabolism of trans-18:1 positional isomers varied in these mice. Differential accumulation in tissues suggests that individual TFA positional isomers may play different roles in human health.

Chlorpyrifos Exposure and Respiratory Health among Egyptian Adolescent Agricultural Workers

Chlorpyrifos Exposure and Respiratory Health among Egyptian Adolescent Agricultural WorkersAbstract Number:1731 Catherine Callahan*, Manal Al-Batanony, Ahmed A. Ismail, Gaafar Abdel Rasoul, Olfat Hendy, James R. Olson, Diane S. Rohlman, and Matthew R. Bonner Catherine Callahan* Department of Epidemiology and Environmental Health, State University of New York at Buffalo, United States, E-mail Address: [email protected] Search for more papers by this author , Manal Al-Batanony Community Medicine and Public Health Department, Faculty of Medicine, Menoufia University, Egypt, E-mail Address: [email protected] Search for more papers by this author , Ahmed A. Ismail Community Medicine and Public Health Department, Faculty of Medicine, Menoufia University, Egypt, E-mail Address: [email protected]ail.com Search for more papers by this author , Gaafar Abdel Rasoul Community Medicine and Public Health Department, Faculty of Medicine, Menoufia University, Egypt, E-mail Address: [email protected] Search for more papers by this author , Olfat Hendy Clinical Pathology and Hematology and Immunology, Menoufia University, Egypt, E-mail Address: [email protected] Search for more papers by this author , James R. Olson Department of Epidemiology and Environmental Health, State University of New York at Buffalo.Department of Pharmacology and Toxicology, State University of New York at Buffalo , United States, E-mail Address: [email protected] Search for more papers by this author , Diane S. Rohlman Occupational and Environmental Health, University of Iowa.Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University , United States, E-mail Address: [email protected] Search for more papers by this author , and Matthew R. Bonner Department of Epidemiology and Environmental Health, State University of New York at Buffalo, United States, E-mail Address: [email protected] Search for more papers by this author AbstractChlorpyrifos (CPF) is a commonly used organophosphate insecticide worldwide. The respiratory system is a target of CPF toxicity and CPF has been linked with wheezing in previous epidemiologic studies. We hypothesized that CPF exposure is inversely associated with lung function. We conducted a 10-month study of adolescent male pesticide applicators (n=37) and non-applicator controls of similar age (n=21).Eight spot urine samples and 2 pulmonary function tests were performed throughout the study. A baseline questionnaire queried history of wheezing. We report on forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). TCPy urinary 3,5,6- trichloro-2-pyridinol (TCPy), a CPF specific metabolite, was analyzed using negative-ion chemical ionization gas chromatography–mass spectrometry. Cumulative TCPy was calculated by measuring the area under the TCPy excretion curve. Linear regression was used to assess the association between cumulative TCPy and spirometric measurements adjusting for age, height, weight and exposure to diesel exhaust. These analyses were performed for 2 time points: day 146, which corresponds to the end of spraying and day 269, after spraying when TCPy levels had returned near baseline. On day 146, a 1000 µg/g creatinine increase in TCPy was associated with a decrease in mean FEV1 of 12.77% (95% confidence interval (CI): -34.87; 9.33), and a decrease in mean FVC of 12.55% (95%CI: -36.40; 11.30). Compared to non-applicators, applicators had higher odds of wheeze, odds ratio = 6.43 (95% CI: 0.75; 54.87). Although preliminary, our results are consistent with an association between self-reported wheeze and pesticide applicator status as well as an association between spirometric measurements and urinary TCPy immediately after the spray season. Our small sample size reduces the precision of our results. Spirometric testing is difficult to standardize and the lack of a true baseline assessment complicate inferences.

Monitoring urinary metabolites resulting from sulfur mustard exposure in rabbits, using highly sensitive isotope-dilution gas chromatography-mass spectrometry.

A highly sensitive method for the determination of sulfur mustard (SM) metabolites thiodiglycol (TDG) and thiodiglycol sulfoxide (TDGO) in urine was established and validated using isotope-dilution negative-ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS). TDGO in the samples was reduced with TiCl3, and then determined together with TDG as a single analyte. The sample preparation procedures, including two solid-phase-extraction (SPE) clean-up steps, were optimized to improve the sensitivity of the method. The limits of detection (LOD) for both TDG and TDG plus TDGO (TDG + TDGO) were 0.1 ng mL(-1), and the limits of quantitation (LOQ) for both were 0.3 ng mL(-1). The method was used in a rabbit cutaneous SM exposure model. Domestic rabbits were exposed to neat liquid SM at three dosage levels (0.02, 0.05, and 0.15 LD50), and the urinary excretion of four species of hydrolysis metabolites, namely free TDG, free plus conjugated TDG (total TDG), free TDG + TDGO, and free plus conjugated TDG + TDGO (total TDG + TDGO), was evaluated to investigate the metabolic processes. The total urinary excretion profiles of the metabolites, including the peak time, time window, and dose-response and time-response relationships, were clarified. The results revealed that the concentrations of TDG and TDG + TDGO in the urine increased quickly and then decreased rapidly in the first two days after SM exposure. The cumulative amount of total TDG + TDGO excreted in urine during the first five days accounted for 0.5-1% of the applied dose of SM. It is also concluded that TDG and TDGO in urine existed mainly in free form, the levels of glucuronide and of sulfate conjugates of TDG or TDGO were very low, and most hydrolysis metabolites were present in the oxidized form (TDGO). The study indicates that the abnormal increase of TDG and TDGO excretion levels can be used as a diagnostic indicator and establishes a reference time-window for retrospective analysis and sampling after SM exposure.

Essential Oil of Carpolobia lutea

Carpolobia lutea G. Don (Polygalaceae) is a shrub or small tree native to West and Central tropical Africa [1]. It is known by many common names such as cattle stick (English), Abekpok Ibuhu (Eket), Ikpafum, Ndiyan, Nyayanga (Ibibio), Agba or Angalagala (Igbo), and Egbo oshunshun (Yoruba). Herbalists from these tribes use the root decoction in locally-made alcohol as an aphrodisiac and also for the treatment of genitourinary infections, gingivitis, and waist pains. The root decoction is also said to be useful in the treatment of internal heat. The plant Carpolobia lutea has been reported to possess anti-inflammatory, anti-arthritic [2], antimicrobial [3, 4], antidiarrheal [5], anti-ulcerogenic [5, 6], anti-nociceptive [7], antimalarial [8], and analgesic properties [9]. The plant is known to contain triterpene saponins [10] and glycosides [11]. No report on its oil constituents could be found in the literature. Leaves of C. lutea (herbarium number: FHI 109066) used for this study were collected in Igbesa, Ogun State (Southwest) and Minna, Niger State (North central), Nigeria, in August 2011. The air-dried samples (300 g each) were hydrodistilled in a Clevenger-type apparatus [12] for 3 h to afford oils with yield 0.06% v/w and 0.10% v/w, respectively, for Igbesa and Minna samples. Both oils were greenish yellow in coloration. GC analysis was performed on HP-5890 series II instrument equipped with HP-wax and HP-5 capillary columns (both 30 m 0.25 mm, 0.25 m film thickness). Analytical conditions: temperature program; 60 C for 10 min, rising from 5 C·min–1 to 220 C; injector and detector temperature 250 C; carrier gas nitrogen (2 mL/min); detector, FID; split ratio, 1:30; volume injected 0.5 L. Gas Chromatography-electron ionization mass spectroscopy (GC-EI-MS) was performed with a Varian CP-3800 gas chromatography equipped with an HP-5 capillary column and a Varian Saturn 2000 ion trap mass detector. Analytical conditions: injector and transfer line temperature 220 C and 240 C, respectively; oven temperature programmed from 60 C to 244 C at 3 C·min–1; carrier gas helium at a flow rate of 1 mL/min; volume injected 0.2 L (10% hexane solution); split ratio 1:30. Mass spectra were recorded at 70 eV. The acquisition mass range was m/z 30–300 at a scan rate of 1 scan·s–1. Identification of the constituents (Table 1) was based on comparison of the linear retention indices with those of authentic samples, and by the use of a self-constructed spectral library built up from pure substances and components of known oils and MS literature data [13, 14]. Moreover, the molecular weights of all the identified substances were confirmed by gas chromatography-chemical ionization mass spectrometry using methanol as CI ionizing gas. Although the composition of both oils of C. lutea looks similar, it is evident that some quantitative differences could be seen among them. The ubiquitous terpenoids were mostly represented in the oils. The major oil contents were hexahydrofarnesyl acetone (22.5 and 20.0%), (E)-geranyl acetone (11.8 and 11.5%), (E)-2-decenal (4.5 and 4.3%), farnesyl acetone (5.8 and 4.8%), germacrene B (3.6 and 5.4%), and -calacorene (2.7 and 2.5%). The results indicate that there seems to be homogeneity in the volatile oils of C. lutea grown in Nigeria. The essential oils from other plant species around the world have been the subject of literature discussions [15, 16].

Characterisation of four popular Polish hop cultivars

SummaryPolish cultivars of hop (Humulus lupulus L.) are well known as aroma and bitter raw material in the brewing industry. To characterise four popular Polish hop cultivars, Lubelski (Lublin), Marynka, Sybilla and Iunga (also known as Junga), the essential oil profiles were determined by gas chromatography/flame ionisation detector (GC‐FID) and gas chromatography/chemical ionisation mass spectrometry (GC‐CIMS) and the alpha/beta acids amounts by high‐performance liquid chromatography/diode array detector (HPLC‐DAD) analysis. In addition, the multivariate statistical analysis of the volatile profiles was performed. The results obtained evidenced qualitative and quantitative differences between the four cultivars studied and the foreign hops described in the literature. Lubelski and Iunga showed the typical chemical profile of the fine‐aroma and high‐alpha cultivars, respectively. In Marynka and Sybilla, the average amounts of alpha acids were similar to the bitter hops, but with a volatile profile characteristics of the fine‐aroma and aroma cultivars respectively.

Simultaneous determination of cyanide and thiocyanate in plasma by chemical ionization gas chromatography mass-spectrometry (CI-GC-MS)

An analytical method utilizing chemical ionization gas chromatography-mass spectrometry was developed for the simultaneous determination of cyanide and thiocyanate in plasma. Sample preparation for this analysis required essentially one-step by combining the reaction of cyanide and thiocyanate with pentafluorobenzyl bromide and simultaneous extraction of the product into ethyl acetate facilitated by a phase-transfer catalyst, tetrabutylammonium sulfate. The limits of detection for cyanide and thiocyanate were 1 μM and 50 nM, respectively. The linear dynamic range was from 10 μM to 20 mM for cyanide and from 500 nM to 200 μM for thiocyanate with correlation coefficients higher than 0.999 for both cyanide and thiocyanate. The precision, as measured by %RSD, was below 9 %, and the accuracy was within 15 % of the nominal concentration for all quality control standards analyzed. The gross recoveries of cyanide and thiocyanate from plasma were over 90 %. Using this method, the toxicokinetic behavior of cyanide and thiocyanate in swine plasma was assessed following cyanide exposure.