Programmed Temperature Vaporizer Research Articles

Quantitative analysis of fragrance in selectable one dimensional or two dimensional gas chromatography–mass spectrometry with simultaneous detection of multiple detectors in single injection

A selectable one-dimensional (1D) or two-dimensional (2D) gas chromatography–mass spectrometry (GC–MS) system coupled with flame ionization detector (FID) and olfactory detection port (ODP) was employed in this study to analyze perfume oil and fragrance in shower gel. A split/splitless (SSL) injector and a programmable temperature vaporization (PTV) injector are connected via a 2-way splitter of capillary flow technology (CFT) in this selectable 1D/2D GC–MS/FID/ODP system to facilitate liquid sample injections and thermal desorption (TD) for stir bar sorptive extraction (SBSE) technique, respectively. The dual-linked injectors set-up enable the use of two different injector ports (one at a time) in single sequence run without having to relocate the 1D capillary column from one inlet to another. Target analytes were separated in 1D GC–MS/FID/ODP and followed by further separation of co-elution mixture from 1D in 2D GC–MS/FID/ODP in single injection without any instrumental reconfiguration. A 1D/2D quantitative analysis method was developed and validated for its repeatability – tR; calculated linear retention indices (LRI); response ratio in both MS and FID signal, limit of detection (LOD), limit of quantitation (LOQ), as well as linearity over a concentration range. The method was successfully applied in quantitative analysis of perfume solution at different concentration level (RSD≤0.01%, n=5) and shower gel spiked with perfume at different dosages (RSD≤0.04%, n=5) with good recovery (96–103% for SSL injection; 94–107% for stir bar sorptive extraction-thermal desorption (SBSE-TD).

Dynamic headspace generation and quantitation of triacetone triperoxide vapor

Two methods for quantitation of triacetone triperoxide (TATP) vapor using a programmable temperature vaporization (PTV) inlet coupled to a gas chromatography/mass spectrometer (GC/MS) have been demonstrated. The dynamic headspace of bulk TATP was mixed with clean humid air to produce a TATP vapor stream. Sampling via a heated transfer line to a PTV inlet with a Tenax-TA™ filled liner allowed for direct injection of the vapor stream to a GC/MS for vapor quantitation. TATP was extracted from the vapor stream and subsequently desorbed from the PTV liner for splitless injection on the GC column. Calibration curves were prepared using solution standards with a standard split/splitless GC inlet for quantitation of the TATP vapor. Alternatively, vapor was sampled onto a Tenax-TA™ sample tube and placed into a thermal desorption system. In this instance, vapor was desorbed from the tube and subsequently trapped on a liquid nitrogen cooled PTV inlet. Calibration curves for this method were prepared from direct liquid injection of standards onto samples tube with the caveat that a vacuum is applied to the tube during deposition to ensure that the volatile TATP penetrates into the tube. Vapor concentration measurements, as determined by either GC/MS analysis or mass gravimetry of the bulk TATP, were statistically indistinguishable. Different approaches to broaden the TATP vapor dynamic range, including diluent air flow, sample chamber temperature, sample vial orifice size, and sample size are discussed. Vapor concentrations between 50 and 5400ngL−1 are reported, with stable vapor generation observed for as long as 60 consecutive hours.

Unexpected dimerization of isoprene in a gas chromatography inlet. A study by gas chromatography/mass spectrometry coupling

During analysis of pure isoprene by gas chromatography/mass spectrometry (GC–MS) using a programmed temperature vaporization (PTV) inlet, the presence of several isoprene dimers was detected in the total ion chromatograms (TICs). This study intends to determine the part of the instrument where dimerization occurs and the relative importance of the dimer amounts under different experimental conditions. The reference thermal dimerization of isoprene gives four six-membered cyclic dimers and two eight-membered ones. In all samples containing different amounts of freshly distilled isoprene, only peaks corresponding to the former appeared in TICs. For the same temperature, their amounts increase as the concentration of injected isoprene increases. The main products are diprene (from 80 to 100%) of the total dimers and dipentene (from 1 to 14%). The sum of the two other dimers is never higher than 6%. In conclusion, isomeric dimers are produced through a dimerization in the inlet. No dimerization of isoprene occurs in the mass spectrometer source. Then care is needed when analyzing terpenic compounds in the presence of isoprene by GC–MS because structures, retention times and mass spectra of diprene and dipentene are close.

Combination of programmable temperature vaporizer-large volume injection gas chromatography-mass spectrometry and automated mass spectral deconvolution and identification system for the determination of 32 pesticides in fruits and vegetables

An analytical method was developed for the simultaneous determination of 32 pesticides including organophosphorus, organochlorine, pyrethroid and carbamate pesticides in fruits and vegetables using gas chromatography-mass spectrometry (GC-MS). The sample was extracted with acetonitrile, and the organic layer was cleaned up with ENVI-Carb and LC-NH2 cartridges. A large volume of 20 µL purified solution was injected into the GC system using programmable temperature vaporizer (PTV). The mass spectrometric detection was operated with full scan mode. The automated mass spectral deconvolution and identification system (AMDIS) and an isotopic internal standard were used for the qualitative and quantitative determination of the 32 pesticides, respectively. The conditions for PTV-large volume injection were studied. Furthermore, the selectivity and durability of the method were also assessed. Under the optimized conditions, the experimental results showed that all the linearities were good within their test ranges, with correlation coefficients more than 0. 995, and the method detection limits of the pesticides were 2.0-5.0 µg/kg. The spiked recoveries (n=6) at three levels in the 0. 010 - 0. 50 mg/kg using spinach, snap bean and cucumber samples as blank matrices were in the range of 65. 2% - 120. 3% with the relative standard deviations (RSDs) varying from 4. 1% to 22. 3%, showing good accuracy of the method. The advantages of the proposed method include high throughput, high sensitivity, reliability, robustness, and the ability to meet the demand of multi-residue pesticide analysis in fruits and vegetables.

Rapid determination of pesticide multiresidues in porphyra by dispersive solid-phase extraction coupled with online gel permeation chromatography-gas chromatography-mass spectrometry

A rapid method for the simultaneous identification and quantification of pesticide multiresidues in porphyra was developed using gel permeation chromatography (GPC) coupled to gas chromatography-mass spectrometry (GPC-GC/MS). Nineteen pesticides (organochlorines, organophosphoruses, triazines and pyrethroids) were selected as the target analytes. The pretreatment method was applied consisting of organic solvent extraction followed by dispersive solid-phase extraction with graphitized carbon black (GCB) and primary secondary amine (PSA) adsorbents. GPC was also employed online to remove the large molecules such as pigments and lipids. The quantitative analysis was carried out by external standard method using gas chromatography coupled with mass spectrometry in selective ion monitoring (SIM) mode. Moreover, a large volume of sample was allowed to be injected using the program of GPC programmed-temperature vaporizer of gas chromatography to improve the sensitivity of measurements. The results showed that the calibration curves were linear (r > 0.995) in the range of 10-1,000 μg/L for all the pesticides. The limits of detection (LODs) for the pesticides in porphyra were from 0.005 to 0.03 mg/kg, and the average recoveries were between 70% and 120%. The advantages of the method are simple, sensitive and shorter operation time for analysis of pesticide residues in porphyra samples.

Reduction of matrix effects in pesticide residue analysis in food by programmable temperature vaporizer

Background: The phenomenon known as the “matrix-induced chromatographic response enhancement” commonly affects the sensibility, precision, and accuracy in pesticide residue analysis. The presence of matrix effects can be given by adsorption and/or thermal decomposition of pesticides on the gas chromatograph injection port. Objective: To reduce the matrix-induced chromatographic response enhancement on pesticide residues analysis in food through the use of several operational modes of programmable temperature vaporizer inlet. Methods: The analyses were carried out in potato (Solanum tuberosum) extracts by gas chromatography with mass spectrometry detector. In this study, four programmable temperature vaporizer splitless modes were investigated: hot, pulsed, cold and solvent vent. Another topic developed in this study has to do with the influence of injection volume, assessed for the matrix effects. Results: The analysis of variance (ANOVA) (α = 0.05) indicates that when the hot splitless is used most compounds are subjected to matrix-induced chromatographic response enhancement. Furthermore, with the pulsed splitless, a decrease in the number of compounds with matrix-induced chromatographic response enhancement was found, approximately 20% compared to the classic hot splitless. Finally, a remarkable decrease in matrix-induced effects was found when cold splitless mode was used, since there was up to 55% reduction in the compounds, relative to traditional hot splitless, that showed statistical differences between responses in matrix-free standards and matrix-matched standards. Conclusions: It was found that the use of conventional hot splitless and pulsed splitless modes caused matrix-induced effects in more than 70% of the studied compounds. In addition, the results indicate that for most compounds there is an inverse relationship between matrix-induced chromatographic response enhancement and the volume of injection.

Determination of dichlobenil and its major metabolite (BAM) in onions by PTV–GC–MS using PARAFAC2 and experimental design methodology

The optimization of a GC–MS analytical procedure which includes derivatization, Quick Easy Cheap Effective Rugged and Safe (QuEChERS) and programmed temperature vaporization (PTV) using design of experiments is performed to determine 2,6-dichlorobenzonitrile (dichlobenil) and 2,6-dichlorobenzamide (BAM) in onions, using 3,5-dichlorobenzonitrile and 2,4-dichlorobenzamide as internal standards. The use of a central composite design and two D-optimal designs, together with the desirability function, makes it possible to significantly reduce the economic, time and environmental cost of the study. The usefulness of PARAFAC2 for solving problems as the interference of unexpected derivatization artifacts unavoidably linked to some derivatization agents, or the presence of coeluents from the complex matrix, which share m/z ratios with the target compounds, is shown. The limits of decision (CCα) of the optimized procedure, 5.00μgkg−1 for dichlobenil and 1.55μgkg−1 for BAM (α=0.05), are below the maximum residue limit (MRL) established by the EU for dichlobenil (20μgkg−1) in this commodity.

Design of experiment approach for the optimization of polybrominated diphenyl ethers determination in fine airborne particulate matter by microwave-assisted extraction and gas chromatography coupled to tandem mass spectrometry

A sensitive and selective procedure for the determination of 12 polybrominated diphenyl ethers (BDE-28, BDE-49, BDE-47, BDE-66, BDE-100, BDE-119, BDE-99, BDE-155, BDE-154, BDE-153, BDE-139 and BDE-183) in airbone particulate matter (PM2.5) at trace level has been developed. The proposed method includes extraction PM2.5-bound PBDEs by microwave-assisted extraction (MAE) followed by gel permeation chromatography (GPC) clean-up and determination by GC-MS/MS using a programmed temperature vaporizer (PTV) in large volume injection (LVI) mode to introduce the sample to the chromatographic system. A design of experiment (DoE) approach was used for the optimization of large volume injection and microwave-assisted extraction parameters to improve these techniques efficiency. Other conditions of the method were studied: GC-MS/MS parameters, extraction solvent and matrix effect. The limit of quantification ranged from 0.063pgm−3 to 0.210pgm−3 when air volumes of 723m3 were collected. Recoveries ranged from 80% to 106%. The method was successfully applied to eight real samples collected from a residential area of the monitoring network of the Region of Valencia Government (Spain) during April–August 2012. BDE-47 and BDE-99 were quantified in six and five samples respectively. The concentrations were ranged from 0.063 to 0.112pgm−3 for BDE-47, and from 0.107 to 0.212pgm−3 for BDE-99.

Occurrence of Pesticide Residues in Lebanon’s Water Resources

Contamination of water sources by pesticides is one of the most critical environmental problems. The present work is designed to address the occurrence of 67 pesticides in the Lebanese waters. Chemical analysis was performed by a solid-phase extraction followed by a gas chromatography-mass spectrometry using programmed temperature vaporization injection. In drinking water and groundwater samples, organochlorine and organophosphate pesticides were frequently detected with a maximal sum concentration of up to 31.8 ng L(-1). High pesticide ecotoxicological risk was noticed in many surface waters, while this risk was driven mainly by diazinon, chlorpyrifos, fenpropathrin and bifenthrin insecticides.

In-line sequential injection-based hollow-fiber sorptive microextraction as a front-end to gas chromatography–mass spectrometry: a novel fully automatic sample processing technique for residue analysis

A novel and affordable analytical setup is herein reported for automatic flow-through sorptive microextraction of organic contaminants, exploiting polydimethylsiloxane (PDMS) as a front-end to gas chromatography-ion trap-tandem mass spectrometry. The analytical procedure involves a short single-strand PDMS hollow fiber integrated in a sequential injection (SI) network for automatic fluidic handling by programmable flow. The target species are in-line extracted from 10 mL of sample containing 20% (v/v) methanol followed by elution with a metered volume of organic solvent, which is whereupon quantitatively transferred into the programmed temperature vaporization (PTV) injector of the GC. Diffusional resistance to mass transfer was overcome by effecting the overall concentration and stripping steps at a single PDMS tubing interface. The proof of concept of the novel hyphenated system was demonstrated for extraction and determination of organochlorine pesticides (OCPs), namely, heptachlor, dieldrin, endrin, endosulfan, p,p'-dichlorodiphenyldichloroethane, p,p'-dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene, and endrin ketone, taken as model analytes, in environmental and industrial waters. Four organic solvents with a broad spectrum of polarity were investigated as eluents in the SI-based assembly, namely, ethyl acetate, methyl tert-butyl ether, hexane, and chloroform. Chloroform was proven the most suitable solvent for expedient elution and fast evaporation in the PTV injector. Under the selected experimental variables, limits of detection (signal-to-noise ratio (S/N) = 3) within the range of 0.3-1.1 ng L(-1), limits of quantification (S/N = 10) of 1.0-3.6 ng L(-1), and method repeatabilities spanning from 1.7 to 4.7% were obtained for the suite of OCPs. The hyphenated flow analyzer was harnessed to the analysis of samples of varying matrix complexity with good relative recoveries (86-112%) in drinking water, surface water, and influent and effluent wastewaters, with quantification limits far below those endorsed by WHO and EU drinking water directives setting maximum allowed concentrations at ≤100 ng L(-1) OCPs.

Automated clean-up, separation and detection of polycyclic aromatic hydrocarbons in particulate matter extracts from urban dust and diesel standard reference materials using a 2D-LC/2D-GC system

A multidimensional, on-line coupled liquid chromatographic/gas chromatographic system was developed for the quantification of polycyclic aromatic hydrocarbons (PAHs). A two-dimensional liquid chromatographic system (2D-liquid chromatography (LC)), with three columns having different selectivities, was connected on-line to a two-dimensional gas chromatographic system (2D-gas chromatography (GC)). Samples were cleaned up by combining normal elution and column back-flush of the LC columns to selectively remove matrix constituents and isolate well-defined, PAH enriched fractions. Using this system, the sequential removal of polar, mono/diaromatic, olefinic and alkane compounds from crude extracts was achieved. The LC/GC coupling was performed using a fused silica transfer line into a programmable temperature vaporizer (PTV) GC injector. Using the PTV in the solvent vent mode, excess solvent was removed and the enriched PAH sample extract was injected into the GC. The 2D-GC setup consisted of two capillary columns with different stationary phase selectivities. Heart-cutting of selected PAH compounds in the first GC column (first dimension) and transfer of these to the second GC column (second dimension) increased the baseline resolutions of closely eluting PAHs. The on-line system was validated using the standard reference materials SRM 1649a (urban dust) and SRM 1975 (diesel particulate extract). The PAH concentrations measured were comparable to the certified values and the fully automated LC/GC system performed the clean-up, separation and detection of PAHs in 16 extracts in less than 24 h. The multidimensional, on-line 2D-LC/2D-GC system eliminated manual handling of the sample extracts and minimised the risk of sample loss and contamination, while increasing accuracy and precision.

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.

Development of an environment-friendly microextraction method for the determination of aliphatic and aromatic aldehydes in water

Aldehydes are produced in water disinfected primarily by ozone treatment, and are generally present in treated water below the limit of detection (<5μgL−1) of commonly proposed methods. Formaldehyde is the most studied along with acetaldehyde due to their mutagenic character, and because it causes chromosomal aberrations. This paper reports the first miniaturised system for the simultaneous determination of thirteen aldehydes (aliphatic and aromatic) which are selected based on their frequent or suspected presence in water, mainly as disinfection by-products (DBPs). The micro liquid–liquid extraction (MLLE) method is a miniaturisation of EPA Method 556.1 for carbonyl compounds that includes some innovations, such as performing the derivatising reaction in a strong acidic medium (pH 1.1), and the addition of magnesium sulphate to the aqueous layer as the heating agent, which allows to carry out the whole simultaneous derivatisation/microextraction process in only 1min. Large-volume sample injection (50μL) coupled to programmed temperature vaporiser–gas chromatography–mass spectrometry is also used to improve both sensitivity and selectivity. The MLLE method demonstrated high extraction efficiency (96%) with low limits of detection, between 0.7 and 80ngL−1, and good precision (RSD below 10%, n=11). The proposed method was evaluated by determining aldehydes in water. Our study demonstrated that the selection of the target aldehydes was appropriate since all were found (at average concentrations from 8.0 to 1.4μgL−1 for aliphatic and aromatic aldehydes, respectively) in swimming pool waters as DBPs.

Feasibility and Safety of High Dose Chemoradiation in Locally Advanced Cervical Cancer: A Preliminary Experience of Gynecologic Oncology Management Italian Team

Locally advanced cervical cancer has a poor prognosis and is difficult to treat by surgery; authors’ evaluated feasibility and safety of the simultaneous integrated boost (SIB) technique for dose escalation in patients with cervical cancer using a rotational dynamic Intensity Modulated Radiation Therapy Technique (VMAT®). Authors evaluated 10 patients affected by loco-regionally advanced, node negative, inoperable cervical cancer. All women received primary chemoradiation (CRT). Six pts received three cycles of platinum-based chemotherapy (CT) plus CRT. Three Programmed Temperature Vaporization (PTV) were delineated: PTV1 (primary, cervix and parametria with a 1cm-margin); PTV2 (body of uterus with a 1cm-margin); PTV3 (pelvic nodes). PTV1 was defined using image fusion between CT-scan and RM or PET/CT. Treatment plans, calculated using a rotational dynamic Intensity Modulated Radiation Therapy (IMRT) system on Oncentra Masterplan® (VMAT®), and consisted in a simultaneous integrated boost. Total treatment time was 45 days. Concomitant CT consisted of weekly cisplatin 40 mg/m2. Dose–volume histograms and acute gastrointestinal, genitourinary, and hematological toxicity were evaluated. Secondary endpoint was evaluation of short term disease free survival. Three months after CTRT, patients were revaluated with colposcopy and cytology and Pelvic imaging. After six and twelve months from CTRT, reevaluation included PET-CT or Chest CT scan and Abdominal and Pelvic RM. All patients concluded radiation without suspension. Cytology demonstrated complete response (CR) in 4 pts in the ERT fraction of brachytherapy (BRT) group and in 1 pts in ERT alone group. All other patients showed a partial response (PR) &gt; 75%. After a median follow up of 20 month (range 16-22), 5 patients are free from disease (NED), 4 patients are alive with disease (AWD) and 1 patient died after three months (DOD). In 2 AWD patients, re-staging PET showed a RC of pelvic disease with evidence of disease in lomboaortic nodes. One of them received salvage radiation therapy on recurrence. After this preliminary experience, in patients with inaccessible cervical canal, authors could propose the dose escalation on PTV1, with the aim of delivering BED as near as possible to 85Gy.

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.

Programmed temperature vaporizing injector to filter off disturbing high boiling and involatile material for on-line high performance liquid chromatography gas chromatography with on-column transfer

Insertion of a programmed temperature vaporizing (PTV) injector under conditions of concurrent solvent recondensation (CSR) into the on-line HPLC–GC interface for on-column transfer (such as the retention gap technique with partially concurrent eluent evaporation) enables filtering off high boiling or involatile sample constituents by a desorption temperature adjusted to the required cut-off. Details of this technique were investigated and optimized. Memory effects, observed when transferred liquid was sucked backwards between the transfer line and the wall of the injector liner, can be kept low by a small purge flow rate through the transfer line at the end of the transfer and the release of the liquid through a narrow bore capillary kept away from the liner wall. The column entrance should be within the well heated zone of the injector to prevent losses of solute material retained on the liner wall during the splitless period. The desorption temperature must be maintained until an elevated oven temperature is reached to prevent peak broadening resulting of a cool inlet section in the bottom part of the injector.

Determination of dioxin-like polychlorinated biphenyls in 1 mL whole blood using programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry

A sensitive method based on programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry (PTV-GC–HRMS) has been developed for the determination of ultra trace levels of dioxin-like polychlorinated biphenyls (DL PCBs) in small amounts of human blood. Blood samples (1mL) were first extracted by column extraction and then purified with column chromatorgraphies. Final extracts (20μL) were introduced to the PTV injector under the solvent vent mode and detected by GC–HRMS (SIM mode). PTV parameters were observed by changing one factor at a time (practical conditions: vent flow: 50mLmin−1, vent pressure: 0kPa and vent time: 0.1min), recoveries of most PCB congeners ranged from 55.1% to 108%, and method detection limits were in the range of 0.11–1.63pgg−1.

Analysis of irradiated cooked ham by direct introduction into the programmable temperature vaporizer of a multidimensional gas chromatography system

A simple method involving direct introduction (DI) of cooked ham into a programmable temperature vaporizer and subsequent thermal desorption for multidimensional chromatographic analysis as a tool for studying changes of volatile compounds during food irradiation has been proposed. Analysis of non-irradiated samples showed four peaks in the precolumn, which were identified on the main column as peak 1, ethyl acetate; peak 2, a mixture of octanol and ethyl propanoate; peak 3, (R,R)-2,3-butanediol, and peak 4, nonanoic acid. (R,R) and (S,S)-2,3-butanediol were detected in samples irradiated at 8kGy, which may indicate that irradiation induces isomerisation. When a single cut was transferred from the precolumn to the main column, 1-tetradecene, n-pentadecane, 8-heptadecene and 1-hexadecene were detected in irradiated samples. This simple and easy method allows detection of radiolytic markers and isomerisation of 2,3-butanediol during irradiation of food.

Simultaneous quantitation of volatile compounds in citrus beverage through stir bar sorptive extraction coupled with thermal desorption-programmed temperature vaporization

Due to disparate concentrations and physiochemical properties of analytes, difficulties in terms of sensitivity and reproducibility are commonly encountered in flavour analysis. In this study, we attempted to improve the performance of stir bar sorptive extraction coupled with thermal desorption and programmed temperature vaporization (SBSE–TD–PTV) based on a model citrus beverage. Through response surface methodology, thermal desorption conditions (i.e. desorption flow, thermal desorption time and cryofocusing temperature) were optimised based on constrained optimisation. Solute discrimination during injection was alleviated by normalising the variability of peak responses of different analytes. In addition, the effects of extraction conditions (i.e. ionic strength, stirring speed, extraction time, temperature and pH) were also investigated using partial factorial design. The obtained method showed high precision and good linearity over the concentration ranged from 0.10 to 20.00μgL−1 with the correlation coefficients higher than 0.991 for most of the selected chemicals, except indole. The limit of detection ranged from 0.03 to 3.89μgL−1. Hence, our results indicated that through the systematic study, SBSE–TD–PTV method became much less solute discriminative and more reliable to quantitate complex analytes.

Clinical Validation of a Highly Sensitive GC-MS Platform for Routine Urine Drug Screening and Real-Time Reporting of up to 212 Drugs

An important role of the clinical toxicology laboratory is to provide continuous diagnostic testing for patients with altered mental status and for other medical indications. To meet these needs, we have developed a new Gas Chromatography-Mass Spectrometry (GC-MS) platform that facilitates routine screening and automated reporting of 212 drugs by laboratory technologists around the clock without the need to sign out by an on-site mass spectrometry-trained toxicologist. The platform uses a programmable temperature vaporizer (PTV) injector for large sample volume injection and the free software Automated Mass Spectral Deconvolution and Identification System (AMDIS) for data reduction and spectral matching that facilitates rapid library searching and analyte identification. Method comparison with 118 patient samples demonstrated that this platform and data searching algorithm independently provided improvements in sensitivity compared to an established GC-MS platform. Further examination of the role of the data processing software and the in-house databases used in the established versus the new platform demonstrated that the improved analytical sensitivity of the new platform was attributed to both the technical superiority of the new GC-MS instrumentation and the use of AMDIS in conjunction with the newly generated in-house library for data processing.