Temperature Vaporizer-gas Chromatography-mass Spectrometry Research Articles

Identification of Volatile Components in Tea Infusions by Headspace–Programmed Temperature Vaporization–Gas Chromatography–Mass Spectrometry (HS–PTV–GC–MS) with Chemometrics

In this work, the two-step headspace (HS) technique was applied to determine the actual volatile compositions of tea infusions. In order to eliminate the influence of water vapor to the gas chromatography-mass spectrometry (GC-MS) analysis and enable the capability to determine the volatile compounds in water base samples, a programed temperature vaporizer (PTV) was employed for the additional pre-concentration of thee analytes. While using the reported method, the volatile compounds were retained by the absorbent packed in the PTV, while the water vapor was directly removed through the purge valve. Then the retained volatile compounds were splitlessly injected into the GC column, which means that very low detection limits were achieved with the newly developed method. The obtained results demonstrated that the reported protocol possessed excellent repeatability and stability for volatile compound determination, and a total of 94 volatile compounds were identified from 28 teas. Multivariate data analysis was performed to obtain insights into the relationship between volatile compounds composition of the teas and their types. The volatiles composition of tea was shown to be closely related to the processing techniques adopted. Furthermore, the characteristic volatile compounds of each tea type were also illustrated. All of the results demonstrated that the presented method is a reliable approach to analyze and discriminate various beverages.

Liquid-liquid extraction-programmed temperature vaporizer-gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in saliva samples. Application to the occupational exposure of firefighters

We present the development and validation of a sensitive method for the reliable determination of sixteen polycyclic aromatic hydrocarbons (PAHs) in saliva samples, which can be used as exposure markers. This method was based on a liquid-liquid extraction and programmed temperature vaporizer-gas chromatography-mass spectrometry analysis (LLE-PTV-GC-MS). Since no matrix effect was found, quantification was performed using external calibration. The detection limits were lower than or equal to 0.057 µg L−1 for all analytes, and repeatability and reproducibility (expressed as relative standard deviation, RSD) were always lower than or equal to 11% and 19%, respectively. The method was used to quantify polycyclic aromatic hydrocarbons in the saliva samples taken from firefighters and unexposed volunteers, detecting the presence of seven of the sixteen analytes analysed. Two of the compounds (fluorene and phenanthrene) were found in the both exposed and unexposed individuals, while the remaining five analytes (naphthalene, acenaphthylene, anthracene, fluoranthene and pyrene) were only detected in samples taken from the firefighters. Good discrimination between the firefighters and the unexposed volunteers was obtained through a principal component analysis.

Salt-assisted dispersive liquid–liquid microextraction coupled with programmed temperature vaporization gas chromatography–mass spectrometry for the determination of haloacetonitriles in drinking water

We report here a new analytical method for the simultaneous determination of seven haloacetonitriles (HANs) in drinking water by coupling salt-assisted dispersive liquid–liquid microextraction (SADLLME) with programmed temperature vaporizer-gas chromatography–mass spectrometry (PTV-GC–MS). The newly developed method involves the dispersion of the extractant in aqueous sample by addition of a few grams of salt and no dispersion liquid was required as compared to the traditional DLLME methods. The extractant (CH2Cl2, 50μL) and the salt (Na2SO4, 2.4g) were successively added to water (8mL) in a conical centrifuge tube that was shaken for 1min and centrifuged (3500rpm, 3min). The aliquot of sedimented phase (4μL) was then directly injected into the PTV-GC–MS system. The limits of detection and quantification for the HANs were 0.4–13.2ngL−1 and 1.2–43.9ngL−1, respectively. The calibration curves showed good linearity (r2≥0.9904) over 3 orders of magnitude. The repeatability of the method was investigated by evaluating the intra- and inter-day precisions. The relative standard deviations (RSDs) obtained were lower than 10.2% and 7.8% at low and high concentration levels. The relative recoveries ranged from 79.3% to 105.1%. The developed methodology was applied for the analysis of seven HANs in several drinking water samples in coastal and inland cities of China. It was demonstrated to be a simple, sensible, reproducible and environment friendly method for the determination of trace HANs in drinking water samples.

Assessment of commercially available polymeric materials for sorptive microextraction of priority and emerging nonpolar organic pollutants in environmental water samples

Among the different organic pollutants, persistent organic pollutants and emerging organic contaminants (EOCs) are of particular concern due to their potentially dangerous effects on the ecosystems and on human health. In the framework of the analysis of some of these organic pollutants in water samples, sorptive extraction devices have proven to be adequate for their monitoring. The efficiency of four commercially available and low-cost polymeric materials [polypropylene, poly(ethylene terephthalate), Raffia, and polyethersulfone (PES)] for the simultaneous extraction of 16 organic compounds from five different families from environmental water samples was evaluated in this work. Firstly, the homogeneity of the sorbent materials was confirmed by means of Raman spectroscopy. After the optimization of the parameters affecting the extraction and the liquid desorption steps, it was found that PES showed the largest efficiencies for slightly polar analytes and, to a lesser extent, for nonpolar analytes. Additionally, Raffia rendered good extraction efficiencies for nonpolar compounds. Thus sorptive extraction methods followed by large volume injection-programmable temperature vaporizer-gas chromatography-mass spectrometry were validated using PES and Raffia as sorbent materials. The validation of the method provided good linearity (0.978 < r (2) < 0.999 for PES and 0.977 < r (2) < 0.999 for Raffia), adequate repeatability (below 19 % and 14 % for PES and Raffia, respectively), and low method detection limits (low ng · l(-1) level). Finally, these materials were applied to the analysis of contaminants in environmental water samples.

Determination of chlorobenzenes in water samples based on fully automated microextraction by packed sorbent coupled with programmed temperature vaporization–gas chromatography–mass spectrometry

A fully automated method consisting of microextraction by packed sorbent (MEPS) coupled directly to programmed temperature vaporizer-gas chromatography-mass spectrometry (PTV-GC-MS) has been developed to determine the 12 chlorobenzene congeners (chlorobenzene; 1,2-, 1,3-, and 1,4-dichlorobenzene; 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzene; 1,2,3,4-, 1,2,3,5-, and 1,2,4,5-tetrachlorobenzene; pentachlorobenzene; and hexachlorobenzene) in water samples. The effects of the variables on MEPS extraction, using a C18 sorbent, and the instrumental PTV conditions were studied. The internal standard 1,4-dichlorobenzene d4 was used as a surrogate. The proposed method afforded good reproducibility, with relative standard deviations (RSD %) lower than 12%. The limits of detection varied between 0.0003 μg L(-1) for 1,2,3,4-tetrachlorobenzene and 0.07 μg L(-1) for 1,3- and 1,4-dichlorobenzene, while those of quantification varied between 0.001 μg L(-1) and 0.2 μg L(-1) for the same compounds. Accuracy of the proposed method was confirmed by applying it to the determination of chlorobenzenes in different spiked water samples, including river, reservoir, and effluent wastewater.

D-optimal experimental design coupled with parallel factor analysis 2 decomposition a useful tool in the determination of triazines in oranges by programmed temperature vaporization–gas chromatography–mass spectrometry when using dispersive-solid phase extraction

The determination of triazines in oranges using a GC–MS system coupled to a programmed temperature vaporizer (PTV) inlet in the context of legislation is performed. Both pretreatment (using a Quick Easy Cheap Effective Rugged and Safe (QuEChERS) procedure) and injection steps are optimized using D-optimal experimental designs for reducing the experimental effort. The relative dirty extracts obtained and the elution time shifts make it necessary to use a PARAFAC2 decomposition to solve these two usual problems in the chromatographic determinations. The “second-order advantage” of the PARAFAC2 decomposition allows unequivocal identification according to document SANCO/12495/2011 (taking into account the tolerances for relative retention time and the relative abundance for the diagnostic ions), avoiding false negatives even in the presence of unknown co-eluents. The detection limits (CCα) found, from 0.51 to 1.05μgkg−1, are far below the maximum residue levels (MRLs) established by the European Union for simazine, atrazine, terbuthylazine, ametryn, simetryn, prometryn and terbutryn in oranges. No MRL violations were found in the commercial oranges analyzed.

A method based on microextraction by packed sorbent-programmed temperature vaporizer–fast gas chromatography–mass spectrometry for the determination of aromatic amines in environmental water samples

We report a sensitive method for the determination of 15 aromatic amines in environmental water samples. They have been included in the list of priority pollutants in surface water by the European Union. The method is based on analyte enrichment using microextraction by packed sorbent (MEPS) and later analysis using programmed temperature vaporizer-gas chromatography-mass spectrometry (PTV-GC-MS). All MEPS steps were carried out manually. The detection limits were of the order of nanograms per liter for most of the compounds. The results were compared with those obtained without MEPS using the method exclusively based on direct injection of the sample into the PTV-GC-MS. External calibration in ultrapure water was used in the determination of the compounds studied in five types of water samples (sea, river, tap, influent, and effluent waste water) since no significant matrix effect was found. The results obtained can be considered highly satisfactory and they revealed the presence of aniline in the sea and the influent and effluent waste water samples.

Solvent-minimized extraction for determining halonitromethanes and trihalomethanes in water

Halonitromethanes (HNMs) are a class of nitrogenous disinfection by-products (N-DBPs) that have so far received little attention and focused largely on trichloronitromethane. By contrast, trihalomethanes (THMs) are the most commonly regulated DBPs and have been the subject of much study. This paper reports the first miniaturized system for the simultaneous determination of the nine known HNMs and four THMs in tap and swimming pool water. Micro liquid–liquid extraction (MLLE) is an adaptation of EPA Method 551.1 using ethyl acetate instead of methyl tert-butyl ether as extractant and large injected sample volumes (30μL) in combination with programmed temperature vaporizer–gas chromatography–mass spectrometry for improved sensitivity and selectivity. Because extraction is done with a few microlitres of organic solvent (200μL) and practically all extract is injected into the instrument, MLLE can be regarded as a virtually solvent-free sample preparation technique. The proposed method provided an extraction efficiency of ∼85%, average limits of detection (tribromonitromethane excluded) of 30ng/L and relative standard deviations of ∼6.0%. The influence of various dechlorinating agents on the stability of the thirteen target analytes in treated water was evaluated; the only salt allowing both types of compounds to be efficiently preserved was (NH4)2SO4, but only for 1 day at 4°C. Therefore, acidifying the sample at pH ∼3.4—the optimum value for MLLE—at the time of collection is recommended in order to ensure that both HNMs and THMs retain their integrity for 2 days during storage at 4°C.

Solid-phase extraction combined with large volume injection-programmable temperature vaporization–gas chromatography–mass spectrometry for the multiresidue determination of priority and emerging organic pollutants in wastewater

In the present work the simultaneous extraction for the multiresidue determination in wastewater samples of organic compounds such as polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), pesticides, polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PEs), alkylphenols (APs), bisphenol A (BPA) or hormones included in different lists of priority and emerging pollutants because of their action as endocrine disrupting compounds (EDCs) was developed. Different solid phase extraction (SPE) variables such as the nature of the solid phase (Oasis-HLC, C18 and Lichrolut), the sample volume, the addition of MeOH and NaCl, the pH of the water phase and the volume of the eluent solvent were optimized in order to analyze simultaneously the priority and emerging families of pollutants mentioned above. Good recoveries were obtained for Milli-Q water (80–120%), however, since the use of deuterated analogues and dilution of the sample did not correct the matrix effect, additional SPE clean-up step using Florisil® cartridges was necessary to obtain good results for wastewater samples (80–125%). In order to improve the limits of detection (LODs), large volume injection (LVI) using programmable temperature vaporizer (PTV) coupled to gas chromatography–mass spectrometry (GC–MS) was also optimized. Since analytes losses in the case of the most volatile congeners occurred during the derivatization step and no separation of the derivatized and the non-derivatized analytes was possible during SPE elution, two different injections were optimized for each analyte group. LODs were in good agreement with those found in the literature and relative standard deviations (RSDs) were in the 10–25% range for Milli-Q and 12–30% for wastewater samples. The method was finally applied to the determination of target analytes in three different wastewater treatment plants (WWTPs, Bakio, Gernika and Galindo (Spain)) and in one water purification plant (WPP) in Zornotza (Spain).

Microextraction by packed sorbent for the analysis of pharmaceutical residues in environmental water samples by in situ derivatization-programmed temperature vaporizer–gas chromatography–mass spectrometry

The present work describes the development and validation of a method for the determination of five non-steroidal anti-inflammatory drugs (NSAIDs: clofibric acid, ibuprofen, naproxen, diclofenac and ketoprofen) in water samples. The fully automated method includes in situ aqueous derivatization followed by analyte enrichment by microextraction by packed sorbent (MEPS) coupled directly to programmed temperature vaporizer-gas chromatography-mass spectrometry (PTV-GC-MS). The MEPS variables, such as sample volume, elution solvent, elution volume, fill and injection speed and washing steps were optimized. It was possible to use the MEPS polymer (silica-C18) 250 times. Ibuprofen-d3 was used as internal standard. The reproducibility of the method, calculated as the relative standard deviation (RSD), was below 10% for all compounds. Detection limits in ultrapure water were between 3.0 and 110 ngL(-1) for ibuprofen and ketoprofen, respectively. External calibration was used in the determination of NSAIDs in several types of water samples, including tap, river, sea and influent and effluent wastewater. The results obtained revealed the presence of ibuprofen and naproxen in the influent wastewater sample and of naproxen in the effluent wastewater sample.

Micro liquid–liquid extraction combined with large-volume injection gas chromatography–mass spectrometry for the determination of haloacetaldehydes in treated water

Haloacetaldehydes (HAs) are becoming the most widespread disinfection by-products (DBPs) found in drinking water, besides trihalomethanes and haloacetic acids, generated by the interaction of chemical disinfectants with organic matter naturally present in water. Because of their high potential toxicity, HAs have currently received a singular attention, especially trichloroacetaldehyde (chloral hydrate, CH), the most common and abundant compound found in treated water. The aims of this study are focused on the miniaturisation of EPA Method 551.1, including some innovations such as the use of ethyl acetate as the extracting solvent, the enhancement of HAs stability in aqueous solutions by adjusting the pH ∼3.2 and the use of a large-volume sample injection (30 μL) coupled to programmed temperature vaporizer–gas chromatography–mass spectrometry to improve both sensitivity and selectivity. In optimised experimental conditions, the limits of detection for the 7 HAs studied ranged from 6 to 20 ng/L. Swimming pools have recently been recognized as an important source of exposure to DBPs and as a result, in this research for the first time, HAs have been determined in this type of water. Two HAs have been found in the analysed water: CH at concentrations between 1.2–38 and 53–340 μg/L and dichloroacetaldehyde between 0.07–4.0 and 1.8–23 μg/L in tap and swimming pool waters, respectively.

Determination of antioxidants in new and used lubricant oils by headspace-programmed temperature vaporization–gas chromatography–mass spectrometry

A sensitive method is presented to determine antioxidants (2-, 3-, and 4-tert-butylphenol, 2,6-di-tert-butylphenol, 3-tert-butyl-4-hydroxyanisol, 2,6-di-tert-butyl-4-methylphenol, 1-naphthol, and diphenylamine) in new and used lubricant oil samples. Research was carried out on a GC device equipped with a headspace sampler, a programmed temperature vaporizer, and an MS detector unit. The proposed method does not require sample treatment prior to analyses, hence eliminating possible errors occurring in this step. Sample preparation is reduced when placing the oil sample (2.0 g) in the vial and adding propyl acetate (20 μL). Solvent vent injection mode permits a pre-concentration of the compounds of interest in the liner filled with Tenax-TA®, while venting other species present in the headspace. Thereby, both the life of the liner and the capillary column is prolonged, and unnecessary contamination of the detector unit is avoided. Calibration was performed by adding different concentrations of analytes to a new oil which did not contain any of the studied compounds. Limits of detection as low as 0.57 μg/L (2-tert-butylphenol) with a precision lower or equal to 5.3% were achieved. Prediction of the antioxidants in new oil samples of different viscosities (5W40, 10W40, and 15W40) was accomplished with the previous calibration, and the results were highly satisfactory. To determine antioxidants in used engine oils, standard addition method was used due to the matrix effect.