Solid-phase Extraction Gas Chromatography-mass Spectrometry Research Articles

Postharvest dehydration of red grapes: impact of temperature and water-loss conditions on free and glycosylated volatile metabolites of exocarp and epicarp of Nebbiolo and Aleatico varieties.

Postharvest dehydration affects the metabolism of grapes, impacting odorous secondary metabolites and therefore the features of the corresponding passito wines - high-quality products with winemaking practices linked to specific territories and related autochthonous grape varieties. Water loss and temperature conditions are the main variables of the dehydration process. This study assessed how they impacted the patterns of free and glycosylated volatile organic compounds (VOCs) of the exocarp (pulp) and epicarp (skin) in Nebbiolo and Aleatico, a neutral and semi-aromatic red grape variety, respectively. Dehydration parameters were set in tunnel conditions, and VOCs were quantitatively analyzed by solid phase extraction-gas chromatography-mass spectrometry. For Nebbiolo grapes, weight loss had a greater impact on free volatiles than dehydration temperature, with a 20% weight loss increasing total VOCs in both exocarp and epicarp. Low temperature (10 °C) significantly increased (P < 0.05) the glycosylated VOCs' terpene content. In Aleatico grapes, weight loss was key in modulating free volatiles, with 30% weight loss and 15 °C leading to significant increases in VOCs, especially exocarp terpenes, acids and benzenoids. More stressful dehydration (30% weight loss at 25 °C) resulted in higher aroma precursor concentrations. These findings can assist passito wine production in preserving varietal aromas of original grapes trough optimized dehydration conditions, preventing sensory homologation occurring because of strong uncontrolled dehydration. They can also promote optimization of energy consumption, thus fostering financial and environmental sustainability. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Synthesis of a novel isotopically labelled standard for quantification of γ-nonalactone in New Zealand Pinot noir via SIDA-SPE-GC–MS

γ-Nonalactone is a linear aliphatic lactone ubiquitous in wine, associated with coconut, sweet, and stone fruit aroma descriptors. Little research has been conducted looking at the importance of this compound to New Zealand (NZ) wine aroma. 2H213C2-γ-Nonalactone, a novel isotopologue of γ-nonalactone, was synthesised in this work for use in a stable isotope dilution assay (SIDA) for quantification of γ-nonalactone in NZ Pinot noir wines for the first time. Synthesis was carried out using heptaldehyde as the starting material, and 13C atoms and 2H atoms were introduced via Wittig olefination and deuterogenation steps, respectively. The suitability of this compound as an internal standard was demonstrated by spiking model wine at normal and elevated conditions during sample preparation, with subsequent analysis via mass spectrometry showing stability of 2H213C2-γ-nonalactone. A model wine calibration, with concentrations of γ-nonalactone from 0 to 100 µg L−1, was shown to have excellent linearity (R2 > 0.99), reproducibility (0.72%), and repeatability (0.38%). Twelve NZ Pinot noir wines, representative of a range of NZ Pinot noir–producing regions, prices, and vintages, were analysed by solid-phase extraction–gas chromatography–mass spectrometry (SPE-GC–MS). The concentrations of γ-nonalactone ranged from 8.3 to 22.5 µg L−1, the latter of which was close to the odour detection threshold of this compound. These findings provide a basis for further research into γ-nonalactone and its impact on NZ Pinot noir aroma and provide a robust method for the quantification of this compound in Pinot noir.Graphical abstract

Simultaneous determination of benzothiazoles, benzotriazoles, and benzotriazole UV absorbers by solid-phase extraction-gas chromatography-mass spectrometry.

Benzotriazoles (BTRs), benzothiazoles (BTHs), and benzotriazole ultraviolet absorbers (BUVs) are common products in plastic rubber and personal care products. Due to their toxicity and bioaccumulation, they have been identified as emerging contaminants (ECs) in the environment. Solid-phase microextraction (SPME) and solid-phase extraction (SPE) combined with gas chromatography-mass spectrometry (GC-MS) were used for the enrichment and detection of the contaminants in seawater and sediment, respectively. The conditions of SPE and SPME were optimized in terms of material, temperature, time, pH, ionic strength, extraction solvent, and elution solvent. Although SPME requires a small sample volume, it is not reliable for the extraction efficiency and reproducibility of BTHs, BTRs, and BUVs in seawater. However, the precision of SPE-GC-MS for the determination of BTHs, BTRs, and BUVs was around 10%, with recoveries of 67.40-102.3% and 77.35-101.8% in seawater and sediment, respectively. The limits of detection of 14 contaminants in seawater and sediment were 0.03-0.47ng/L and 0.01-0.58ng/g, respectively. Secondly, BTHs, BTRs, and BUVs were detected with low ecological risk when SPE-GC-MS was applied to the analysis of seawater and sediment samples from the Yangtze estuary and its adjacent areas. The SPE-GC-MS was highly precise with lower detection limits relative to previous studies and thus was able to meet the requirements for the detection of BTHs, BTRs, and BUVs in seawater and sediments.

Pollution Characteristics and Risks of Polycyclic Aromatic Hydrocarbons in Underground and Surface Drinking Water Sources in Northeast Inner Mongolia

Polycyclic aromatic hydrocarbons (PAHs) are hazardous and ubiquitous pollutants in the aquatic environment, and understanding the pollution characteristics and risk levels of PAHs is of great significance to the sustainable development of drinking water sources and drinking water safety. Hence, PAHs residues were measured qualitatively and quantitatively with solid-phase extraction-gas chromatography-mass spectrometry (SPE-GC-MS) in 33 water samples (including 22 groundwater and 11 surface water samples) of the drinking water sources in the Manzhouli and Xinyouqi areas of northeast Inner Mongolia, and assessments of the pollution level of PAHs and the health and ecological risks were carried out. The results showed that PAHs were detected in all 33 sampling points of Manzhouli drinking water sources, except for benzo[k] fluoranthene, benzo[a] pyrene, and dibenzo[a,h] anthracene, with detection rates ranging from 36.36% to 95.45%; the detection rates of the other 13 PAHs monomers were 100%. The detection range of ρ（ΣPAHs） was 42.76-164.50 ng·L-1, and the mean value was 90.82 ng·L-1. The detection ranges of ρ（ΣPAHs） in surface water and groundwater were 66.39-164.50 ng·L-1 and 42.76-147.70 ng·L-1, respectively. The concentration of the detected naphthalene was the highest, with a mean value of 36.91 ng·L-1, and the concentration of anthracene was the lowest, with a mean value of 0.81 ng·L-1; there were no significant differences among the concentrations of all the PAHs monomers of the surface and groundwater (P>0.05). The pollution of PAHs was at a median level in China and abroad, mainly in the middle and low loops (3-4 loops). The analysis of the sources of PAHs in groundwater and surface water in Manzhouli using the ratio feature method and principal component analysis showed that the PAHs in the drinking water source water bodies in the Manzhouli area were mainly affected by the combustion of coal and biomass and oil, and some surface water sources were affected by the oil source. The human health and ecological risk assessment results showed that the water body of drinking water would not cause health risks to the human body, and the ecological risk was at a medium level; however, the high risk of benzo[b] fluoranthene (BbF) monomer production should be continuous cause for concern. From the perspective of the sustainable development of drinking water sources and drinking water safety, the necessary supervision and protection measures should be considered to prevent further pollution. The results of this research provide a scientific basis for the pollution control and prevention and control of PAHs in drinking water sources.

A sensitive, robust method for determining natural and synthetic hormones in surface and wastewaters by continuous solid-phase extraction–gas chromatography–mass spectrometry

Over recent decades, steroidal estrogens have become an emerging and very serious issue as they pose a serious threat to living organisms, soil, plants, and water resources in general. Estrogens have therefore been the subject of considerable scientific attention in order to develop new methodologies for its determination, being able of detecting them at very low concentrations. Those procedures minimize or eliminate the consumption of organic solvents and reagents that may be incompatible with the environment. In this respect, we developed a sensitive, selective method for the simultaneous determination of thirteen natural and synthetic hormones present at the nanogram-per-liter level in various types of water by using continuous solid-phase extraction in combination with gas chromatography and mass spectrometry (GC–MS). The target analytes were preferentially sorbed on an Oasis HLB sorbent column (80 mg) and eluted with acetone (600 µL) for derivatization with a mixture of 70 µL of N,O-bis(trimethylsilyl) trifluoroacetamide and trimethylchlorosilane and 35 µL of petroleum ether in a household microwave oven at 200 W for 4 min. Under optimum conditions, the ensuing method exhibited good linearity (r ≥ 0.998), good precision (RSD ≤ 7%), high recoveries (92–103%), and low detection limits (0.01–0.3 ng L−1). The method outperforms existing alternatives in robustness, sensitivity, throughput, flexibility—it allows both estrogens, progestogens, and androgens to be determined simultaneously—and compliance with the principles of Green Chemistry. It was successfully used to analyze various types of water samples (mineral, tap, well, pond, swimming pool, river, and waste) that were found to contain four estrogens (estrone, 17β-estradiol, 17α-ethinylestradiol, and hexestrol), two progestogens (testosterone, dihydrotestosterone), and one progestogen (progesterone) at concentrations ranging from 3.0 to 110 ng L−1.

Characterization of Berry Aromatic Profile of cv. Trebbiano Romagnolo Grapes and Effects of Intercropping with Salvia officinalis L.

Volatile organic compounds (VOCs) are secondary metabolites responsible for the aroma of grapes and the quality of wine. Apart from genetics, agronomic practices may impact the aroma composition and the concentration of volatiles in grape berries. The possible influence of intercropping with medicinal aromatic plants (MAPs) on the VOCs in grape berries’ profile has been poorly explored. Trebbiano Romagnolo is a white Vitis vinifera cultivar cultivated within the Italia region Emilia-Romagna. The study investigated, for the first time, the volatile organic profile of Trebbiano Romagnolo berries as well as the possible influences of intercropping with sage (Salvia officinalis L.) on the volatile composition of grape berries. A total of 48 free and bound aroma compounds were identified using solid phase extraction-gas chromatography-mass spectrometry (SPE-GC-MS). In the free aroma fraction, the main classes were C6 derivatives, alcohols, and benzenes, while in the bound aroma fraction, the major classes were benzenes, C13 norisoprenoids, and terpenes. The results obtained in this experiment indicate that intercropping with Salvia officinalis may influence volatile compounds in grape berries, an interesting result in cultivars considered neutral such as Trebbiano Romagnolo, providing new insights for exploring the complexity of the terroir and the role of agroecological strategies.

A new core-shell magnetic mesoporous surface molecularly imprinted composite and its application as an MSPE sorbent for determination of phthalate esters.

In this study, a new core–shell magnetic mesoporous surface molecularly imprinted polymer (Fe3O4@SiO2@mSiO2-MIPs) which has specific adsorption and rapid adsorption rate for phthalate esters (PAEs) was prepared by a convenient method. Based on this composite as a magnetic solid phase extraction (MSPE) material, a rapid, efficient and sensitive matrix dispersion magnetic solid-phase extraction gas chromatography-mass spectrometry method (DMSPE-GC/MS) was developed for the determination of PAEs in multiple liquid samples. It is the first time that Fe3O4@SiO2@mSiO2-MIPs have been prepared by bonding amino groups on the surface of a double layer silicon substrate with diisononyl phthalate (DINP) as virtual template and 3-(2-aminoethyl)-aminopropyl trimethoxymethylsilane (TSD) as functional monomer. FT-IR, TEM, EDS, SEM, XRD, BET and VSM were used to characterize the composite. The adsorption isotherm and kinetics of Fe3O4@SiO2@mSiO2-MIPs showed that it possessed fast adsorption rates (approximately 5 min to reach equilibrium), high adsorption capacities (523.9 mg g−1) and good recognition of PAEs. The real samples were preconcentrated by Fe3O4@SiO2@mSiO2-MIPs, under the optimum DMSPE-GC/MS conditions. Validation experiments showed that the method presented good linearity (R2 > 0.9971), satisfactory precision (RSD < 5.7%) and high recovery (92.1–105.8%), and the limits of detection ranged from 1.17 ng L−1 to 3.03 ng L−1. The results indicated that the novel method had good sensitivity, high efficiency and wide sample application and was suitable for the determination of PAEs in liquid drink samples such as water, alcohol, beverages and so on.

Simultaneous Determination of Benzothiazoles, Benzotriazoles and Benzotriazole Uv Absorbers by Solid-Phase Extraction-Gas Chromatography-Mass Spectrometry

Simultaneous Determination of Benzothiazoles, Benzotriazoles and Benzotriazole Uv Absorbers by Solid-Phase Extraction-Gas Chromatography-Mass Spectrometry

Removal of organic pollutants by effluent recirculation constructed wetlands system treating landfill leachate

The leachate of municipal solid waste landfills contains various types of organic substances, increasing the difficulty of efficient treatment. This study built an effluent recirculation (1:4 ratios) vertical subsurface flow constructed wetlands (CWs) system treating actual landfill leachate (LL). In order to better monitor and evaluate the removal of organic pollutants in LL by CWs, Three-Dimensional Fluorescence (3D-EEM) and Solid Phase Extraction–Gas Chromatography–Mass Spectrometry (SPE–GC–MS) analysis of CWs influent and effluent water was performed to investigate the removal of Dissolved organic matter (DOM), Organochlorine pesticides (OCPs), Organophosphorus pesticide (OPPs), Polycyclic aromatic hydrocarbons (PAHs), and Volatile organic compounds (VOCs). Results showed that during the treatment of LL by CWs, the average removal rate of conventional pollutants (COD, NH4+-N and TP) was over 85%, with a majority of microbial metabolites and humic acids in DOM effectively degraded. The concentrations of OCPs, OPPs, PAHs, and VOCs in the CWs influent LL ranged between 378.6 and 4746.32 ng L−1, accounting for only a small proportion (3.7×10−7–4.6×10−6) of COD. The achieved organic micro-pollutants total removal rates were: OCPs(56.9%), OPPs(41.4%), PAHs(58.3%), and VOCs(78.3%), with relatively higher removal rates observed for DDT (83.6%), dimethoate (89.2%), benzo(a)anthracene (82.0%). Therefore, the effluent recirculation CWs system can effectively remove organic pollutants in LL, indicating that this is a promising technology with good application for the effective treatment of wastewater.

Identification of Key Volatiles Differentiating Aromatic Rice Cultivars Using an Untargeted Metabolomics Approach.

Non-aromatic rice is often sold at the price of aromatic rice to increase profits, seriously impairing consumer experience and brand credibility. The assessment of rice varieties origins in terms of their aroma traits is of great interest to protect consumers from fraud. To address this issue, the study identified differentially abundant metabolites between non-aromatic rice varieties and each of the three most popular aromatic rice varieties in the market using an untargeted metabolomics approach. The 656 metabolites of five rice grain varieties were determined by headspace solid-phase extraction gas chromatography-mass spectrometry, and the multivariate analyses were used to identify differences in metabolites among rice varieties. The metabolites most differentially abundant between Daohuaxiang 2 and non-aromatic rice included 2-acetyl-1-pyrroline and acetoin; the metabolites most differentially abundant between Meixiangzhan 2 and non-aromatic rice included acetoin and 2-methyloctylbenzene,; and the metabolites most differentially abundant between Yexiangyoulisi and non-aromatic rice included bicyclo[4.4.0]dec,1-ene-2-isopropyl-5-methyl-9-methylene and 2-methylfuran. Overall, acetoin was the metabolite that was most differentially abundant between the aromatic and non-aromatic rice. This study provides direct evidence of the outstanding advantages of aromatic rice and acts a reference for future rice authentication processes in the marketplace.

Study on the method of detection of benzene exposure biomarkers by solid phase extraction-gas chromatography-tandem mass spectrometry

Objective: A gas chromatography-tandem mass spectrometry detection method for benzene and its metabolites was established to provide methodological support and theoretical basis for the study of benzene toxicity mechanism. Methods: In August 2019 to March 2020, the animal model of containing high concentration of benzene by inhalation of poison through the respiratory tract of mice was established, taken the blood of mice after dyeing the poison, and the HLB solid phase extraction method was used to extract and purify the samples. The gas chromatography-tandem mass spectrometry detection method was used to qualitative and quantitative analysis of the target substances. After separated by HP-17MS capillary chromatographic column, the compounds were ionized with EI ion source, mass spectrometry detection was carried out by selective ion scanning method (SIM) , and quantification was carried out by external standard curve method. Results: Benzene and its metabolites (phenol, catechol, hydroquinone and m-trihydroxybenzene) in blood could be effectively separated and quasi deterministic and quantitative by this method. The regression equations and correlation coefficients of this method for detecting benzene and its metabolites were: benzene: y=3252.1x+1540, r=0.9993; phenol: y=2046.5x+1423, r=0.9991; catechol: y=1853.9x+945, r=0.9993; hydroquinone: y=1891.5x+840, r=0.9992; m-trihydroxybenzene: y=1052.4x+655, r=0.9991. The detection limits for benzene, phenol, catechol, hydroquinone and m-trihydroxybenzene were 0.03, 0.03, 0.05, 0.05 and 0.10 μg/g, respectively. And the lower limits of quantification were 0.10, 0.10, 0.15, 0.15 and 0.30 μg/g, respectively. The intra-assay precision interval was 2.64%-10.06%, the inter-assay precision interval was 1.37%-10.17%, and the spike recovery rate was 89.8%-102.3%. This method could be used to quantitatively detect benzene, phenol, catechol, hydroquinone and m-trihydroxybenzene in the blood of benzene-infected mice. Conclusion: Solid phase extraction-gas chromatography-mass spectrometry can be used for qualitative and quantitative detection of benzene and its metabolites (phenol, catechol, hydroquinone and m-trihydroxybenzene) accurately.

Removal of Estrogens in Kuwaiti Municipal Wastewater Treatment Plants

Presence of estrogens in the environment is gaining great attention worldwide due to their potential adverse effects on aquatic ecosystems and public health. Estrogens pollution is generally related to incomplete removal at wastewater treatment plants (WWTPs). To ascertain the status of estrogens pollution in Kuwait, this study evaluated the removals of estrogens at municipal WWTPs in Kuwait. The solid-phase extraction gas chromatography-mass spectrometry method was used for the determination of estrogens concentrations in influent and effluent streams of three main municipal WWTPs (Kabd, Suliabiya and Umm-Al-Haiman). Obtained results indicated that concentration of estrogens in the influent streams ranged from 0.0 to 474 ng/l, while that in the effluent streams were between 0.0 to 233 ng/l. Both influent and effluent concentrations showed high variations around mean values. Average removal rates of total estrogens were found to be 13%, 79%, 68%, for Kabd, Suliabiya and Umm-Al-Haiman, respectively. This study indicated that operation of municipal WWTPs in Kuwait needs to be upgraded/optimized in order to maximize estrogens’ elimination. It also revealed that Kuwait needs to regulate discharges of estrogens from WWTPs in order to prevent further pollution of marine environment and groundwater.

Analysis of balms taken from Egyptian human mummies using solid-phase extraction and gas chromatography-mass spectrometry.

The aim of this paper is to establish a protocol by solid-phase extraction-gas chromatography-mass spectrometry leading to a wide and fine qualitative chemical characterization of the several natural substances present in human mummies' balms, using a minimal quantity of samples. In this study, nine samples were analyzed from mummies dating back from the Third Intermediate Period to the Roman Period, and were provided by the Confluences Museum (Lyon, France). Using solid-phase extraction, three fractions were examined in this protocol. The first one, eluted with hexane, concerned chemical families of hydrocarbons of bitumen. The second, eluted with ethanol, enabled terpenic compounds to be characterized and beeswax. The last one, composed of diethyl ether with 2% acetic acid, extracted carboxylic acids with a long aliphatic chain (fatty matter) and glycerides. This study also allowed the characterization of non-saponified compounds from beeswax to be obtained while excluding the common saponification step. The analyzed mummification balms were shown to contain fatty matter, beeswax, bitumen, and diterpenic resinous material. This one-pot solid-phase extraction-gas chromatography-mass spectrometry method was efficient in reducing both the number of analytical steps and the complexity of the archaeological balms subsequently analyzed by gas chromatography-mass spectrometry.

Determination of 2,4-diaminotoluene in Mianpi composite packaging film bags by ion-exchange solid-phase extraction-gas chromatography-mass spectrometry

A method for the determination of 2,4-diaminotoluene in Mianpi composite packaging film bags was established based on ion-exchange solid-phase extraction-gas chromatography-mass spectrometry (GC-MS). The samples were immersed in 4% (v/v) acetic acid solution. 2,4-Diaminotoluene was enriched from a 50.0 mL soak solution with an activated and balanced MCX solid-phase extraction column. The MCX column was washed with 5.0 mL water and eluted with 3.0 mL ammoniated methanol. 2,4-Diaminotoluene was detected quantitatively by GC-MS after derivatization with heptafluorobutyric acid anhydride. In the mass concentration range of 1-50 μg/L, the linear correlation coefficient (r) was 0.9991. The limit of detection (LOD, S/N=3) was 0.2 μg/L, and the limit of quantification (LOQ, S/N=10) was 0.6 μg/L. The recovery of 2,4-diaminotoluene was in the range of 89.0%-94.2%. The relative standard deviations (RSDs) were 1.9%-3.6%. This method requires neither pH adjustment of the soak solution in the pre-processing step nor liquid-liquid extraction. With this method, the pre-processing step is greatly simplified and there is minimal consumption of organic solvents. Further, the method is simple, convenient, and accurate, and it is suitable for the determination of 2,4-diaminotoluene in Mianpi composite packaging film bags.

Qualitative and Quantitative Analysis of Cathinones in Human Urine by SPE-GC-MS.

To propose an alternative solid phase extraction-gas chromatography-mass spectrometry （SPE-GC-MS） method for the sensitive determination of cathinones in human urine samples, plus methodological verification. Human urine samples were concentrated by solid phase extraction （SPE） sorbent and converted into the corresponding heptafluorobutyric acid anhydride derivatives. Methcathinone, 4-methylmethcathinone and 3,4-methylenedioxy-N-methylcathinone were detected by gas chromatography-mass spectrometry （GC-MS）. With quantitative analysis by internal standard method, methodological verification was carried out from the aspects of specificity, precision and reco-very rate. Methcathinone, 4-methylmethcathinone and 3,4-methylenedioxy-N-methylcathinone showed good linearly in the range of 25-200 ng/mL of urine （r>0.99）, with the limits of detection 2.0 ng/mL, limit of quantitation 25.0 ng/mL, both intra- and inter-day coefficients of variation lower than 6.0%, and recovery rates of 98.4%-105.7%. he proposed SPE-GC-MS procedure has good accuracy and specificity, can meet the need of qualitative and quantitative analysis of cathinones in the urine of drug abusers, and therefore provide technical support for the detection of cathinone abuse.

Multiresidue determination of polycyclic aromatic hydrocarbons in edible oils by liquid-liquid extraction–solid-phase extraction–gas chromatography–mass spectrometry

The presence of polycyclic aromatic hydrocarbons (PAHs) in edible oils is usually due to environmental contamination, manufacturing processes or the nature of the oil. Because oils constitute a very large family of foodstuffs that are ubiquitous in human diet, the presence of PAHs in them may have a considerable impact. In this work, we developed a method for determining EPA's 16 PAH priority pollutants using liquid–liquid and solid-phase extraction for their extraction and isolation, and gas chromatography–mass spectrometry for their quantification. The proposed method is highly sensitive, with limits of detection from 4 to 110 ng kg−1, accurate (PAH recoveries of 87–104%) and precise (relative standard deviation < 7.5%). Application to various types of oil (olive, sunflower, coconut, soybean and sesame) testified to its flexibility. Most of the samples studied contained more than three PAHs, albeit at concentrations below the legally allowed levels. Only two samples of refined sunflower oil contained no PAH at levels within the sensitivity range of the method.

Determination of labdanoids in oriental tobacco by D-SPE-GC/MS

In order to establish a method to quantify labdanoids in oriental tobacco, a dispersive Solid-Phase Extraction-Gas Chromatography-Mass Spectrometry (d-SPE-GC/MS) method was used to measure ten labdanoids in oriental tobacco. The fragmentation mechanisms of nine labdaniols were deduced according to the fragmentation pattern of sclareolide, and their contents were semi-quantified by using the calibration curve of sclareolide. With anthracene-d10 as the internal standard, the effects of extraction time, eluent volume and purification on the contents of labdanoids were investigated. The results showed the correlation coefficient (R2) and relative standard deviation (RSD) of sclareolide was 0.999 5 and 2.09%, respectively. The recoveries ranged from 100.65% to 106.91%. The limits of detection and quantification were 0.06 μg·mL-1 and 0.19 μg·mL-1, respectively. This method is simple, sensitive, accurate, therefore suitable for the determination of labdanoids in oriental tobacco.

Direct detection of Mycobacterium tuberculosis in sputum: A validation study using solid phase extraction-gas chromatography-mass spectrometry.

Tuberculosis (TB) remains a worldwide health problem, especially in developing countries. Correct identification of Mycobacterium tuberculosis (MTB) infection is extremely important for providing appropriate treatment and care to patients. Here we describe a solid phase extraction-gas chromatography-mass spectrometry method (SPE-THM-GC-MS) for the detection of five biomarkers for M. tuberculosis. The method for classification is developed and validated through the analysis of 112 sputum samples from patients suspected of having TB. Twenty of twenty-five MTB culture-positive sputum samples were correctly classified as positive by our improved SPE-THM-GC-MS method. Eighty-five of eighty-seven MTB culture-negative samples were also negative by SPE-THM-GC-MS. The overall sensitivity of the new SPE-THM-GC-MS method is 80% (20/25) and the specificity is 98% (85/87) compared with culture. The method proved to be reliable and, although complex in principle, easy to operate due to the high degree of automation.

A modified commercial gas chromatograph for the continuous monitoring of the thermal degradation of sunflower oil and off-line solid phase extraction gas–chromatography–mass spectrometry characterization of released volatiles

A homemade flow cell attached to a commercial Gas Chromatograph equipped with a Flame Ionization Detector (FID) has been designed for the continuous monitoring of volatile compounds released during heating edible oils. Analytical parameters such as mass of sample, temperature and flow rates have been optimized and the obtained results have been compared with the corresponding thermographs from standard TG systems. Results show that under optimum conditions, the profiles of volatiles released upon heating are comparable to the profiles of TG curves, suggesting that the FID based system could be an alternative to TGA. Additionally, volatiles have been retained in a Lichrolut EN® resin, eluted and analyzed by Gas Chromatography–Mass Spectrometry. In this case, forty five compounds have been identified (acids, alcohols, alkanes, aldehydes, ketones and furans) and compared with the FID signals, working both in air or nitrogen atmosphere. It has been concluded that the oxidative thermal degradation is prevented in the presence of a nitrogen atmosphere.

Direct detection of Mycobacterium tuberculosis in sputum using combined solid phase extraction-gas chromatography-mass spectrometry.

Recently, thermally-assisted hydrolysis and methylation followed by gas chromatography-mass spectrometry (THM-GC-MS) in combination with chemometrics has been used to develop a 20-compound model for fast differentiation of Mycobacterium tuberculosis (MTB) from Non-tuberculous mycobacteria (NTM) in bacterial cultures. This model provided better than 95% accuracy. In our current work a hexane/methanol/water extraction followed by a solid phase extraction (SPE) clean-up procedure was developed for use before THM-GC-MS, to make the test suitable for the identification of mycobacteria in sputum. The 20 biomarker model had to be adapted since many compounds were also found in the sputum of non-tuberculosis patients. An algorithm was established based on tuberculostearic acid, hexacosanoic acid and mycoserosates. The detection limit of the method was approximately 1×10(4) bacteria/mL sputum. Sputum specimens from 32 patients from South Africa who were suspected of having tuberculosis were blindly tested using the new method. Eight of the nine culture-positive sputum specimens were detected by the new SPE-THM-GC-MS method, resulting in a sensitivity of 89%. The specimen that was missed by the new method was also microscopy negative. The specificity of the test was 100%; all 23 microscopy- and culture-negative specimens were correctly identified as negative by SPE-THM-GC-MS.