Development of non-aqueous single stage derivatisation method for the determination of putrescine and cadaverine using GC-MS

A single step derivatisation for the determination of putrescine and cadaverine by gas chromatography using trifluoroacetylacetone (TFAA) in methanol or ethanol was studied and optimised. The derivatives were analysed by an iontrap gas chromatograph-mass spectrometer (GC-MS) operating with electron impact ionisation with selective ion storage (EI-SIS) mode. The optimised mole ratios for TFAA/putrescine and TFAA/cadaverine reactions were 5/1 and 5.8/1 respectively with a reaction time of 15 minutes at 95oC. The retention times for the derivatised putrescine and cadaverine were 11.3 and 12.2 minutes respectively using the capillary column, CP-Sil 8CB; 30 m length x 0.25 mm i.d. x 0.25 mm film. The correlation coefficients (R²) of calibration curves for putrescine and cadaverine were 0.991 and 0.990 respectively over a concentration range of 100 ng cm⁻³ to 1500 ng cm⁻³. The method developed was found to be simple (single-stage derivatisation), rapid (15 minutes derivatisation & 14 minutes GC/MS run) and accurate (putrescine and cadaverine recoveries 94.8%–97.7%).      

热解吸-电晕放电电离-离子迁移谱法现场快速筛查化妆品中5种禁用组分

采用热解吸-电晕放电电离技术结合离子迁移谱，研究建立了化妆品中5种禁用卡因类化合物的现场快速筛查方法。化妆品样品无需前处理步骤，样品轻轻蘸取、滴加或喷雾在采样拭纸上，置于离子源样品槽中，采用热解吸-电晕放电电离技术实现样品中待测物的热解吸和离子化，随后以离子迁移谱进行快速筛查分析。5种卡因类化合物的检出限为10~50 ng，离子迁移谱分析时间小于20 ms，整个样品分析周期不超过1 min。本方法简便、快速、成本低廉，适用于化妆品中卡因类禁用组分的现场快速筛查。     

Quantitative determination of n-alkanethiols in air and in a blended gas mixture of methane with air by gas chromatography/differential mobility spectrometry

Mixtures of n-alkanethiols, in solution with equi-molar amounts from 0.5 to 360 ng per compound, were determined using gas chromatography (GC) with a differential mobility spectrometer, operated with a flow of air at ambient pressure, as the GC detector. A homologous series of n-alkanethiols with carbon number from two to six showed baseline resolution in the GC separation and positive and negative ion chromatograms were produced simultaneously for the alkanethiols. Differential mobility spectra showed compensation voltages characteristic of each alkanethiol and plots of ion intensity, retention time, and compensation voltage yield contour plots illustrating the second dimension of analytical selectivity provided by the detector. Another yet undeveloped dimension of analytical information was found in the dependence of mobility coefficients on electric field. Mass-analysis of ions from thiols showed a hydrogen abstracted ion, protonated monomers, and proton bound dimers. Linear ranges were narrow and the minimum detectable limits were ~1 ng. Response in positive polarity provided a ten-fold improvement in detection limits though spectra were more complex than for negative ions. In a methane-rich air atmosphere, intended to simulate ambient air or the detection of leaks from natural gas pipelines, the response to thiols with negative ions was not degraded by the methane up to 50% v/v, the highest level tested.     

On-line solid-phase extraction-thermal desorption-gas chromatography with ion trap detection tandem mass spectrometry for the analysis of microcontaminants in water

An improved set-up for solid-phase extraction with thermal desorption coupled on-line to gas chromatography (SPETD-GC) is presented. It includes a newly designed liner for a programmable temperature vaporizer (PTV) and an improved water elimination system. The SPETD procedure now includes a washing step with HPLC-grade water to prevent degradation of analytes due to interaction with remaining sample constituents. The system was used to analyze surface and tap water samples over a 4-month period. No decrease of chromatographic or trace-enrichment performance was observed, and a liner packed with Tenax GR could be used for at least 150 analyses. The SPETD module was coupled to GC with ion-trap detection for mass spectrometric (MS) and MS/MS detection. The linearity and repeatability of the procedure for several pesticides which were tested in the 0.5–10 μg/1 range were fully satisfactory (1 μg/1, RSD range 5–11%; n = 5). When using sample volumes of 0.1 ml only, detection limits were as low as 0. 1-0.2 μg/1. As an example, the confirmation and quantification of a suspected pesticide in a real-life sample using electron impact and positive chemical ionization in both the MS and MS/MS mode is shown.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for trace analysis of methylmercury and mercury(II) in water sample

A method for the trace analysis of methylmercury (MeHg) and Hg(II) in water sample was developed, which involved stir bar sorptive extraction (SBSE) with in situ alkylation with sodium tetraethylborate and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). The limits of quantification of MeHg and Hg(II) are 20 and 10 ng L⁻¹ (Hg), respectively. The method shows good linearity and the correlation coefficients are higher than 0.999. The average recoveries of MeHg and Hg(II) in tap or river water sample are 102.1-104.3% (R.S.D.: 7.0-8.9%) and 105.3-106.2% (R.S.D.: 7.4-8.5%), respectively. This simple, accurate, sensitive, and selective analytical method may be used in the determination of trace amounts of MeHg and Hg(II) in tap and river water samples.     

Development of a stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry method for determining synthetic musks in water samples

This study presents the development of an analytical method for determining 9 synthetic musks in water matrices. The developed method is based on stir bar sorptive extraction (SBSE), coated with polydimethylsiloxane, and coupled with a thermal desorption–gas chromatography–mass spectrometry system (TD–GC–MS). SBSE can efficiently trap and desorb the analytes providing low limits of detection (between 0.02 ng L⁻¹ and 0.3 ng L⁻¹). Method validation showed good linearity, repeatability and reproducibility for all compounds. Furthermore, the limited manipulation of the sample required in this method implies a significant decrease of the risk of external contamination of the samples. The performance of the method in real samples was evaluated by analysing biological wastewater treatment plant (WWTP) influent and effluent samples, reverse osmosis treatment plant effluents and river waters. The most abundant musk was galaxolide with values up to 2069 ng L⁻¹ and 1432 ng L⁻¹ in the influent and effluent of urban WWTP samples, respectively. Cashmeran, Pantolide and Tonalide were also detected in all the matrices with values up to 94 ng L⁻¹, 26 ng L⁻¹ and 88 ng L⁻¹, respectively. Although in Europe the use of nitromusks in cosmetics is prohibited, musk xylene and musk ketone were detected both in the WWTP and in the river samples. As far as we know, this is the first time than a SBSE method coupled with TD is applied for the determination of synthetic musks in water samples.     

Environmentally friendly solid‐phase microextraction coupled with gas chromatography and mass spectrometry for the determination of biogenic amines in fish samples

In this work, a facile and environmentally friendly solid‐phase microextraction assay based on on‐fiber derivatization coupled with gas chromatography and mass spectrometry was developed for determining four nonvolatile index biogenic amines (putrescine, cadaverine, histamine, and tyramine) in fish samples. In the assay, the fiber was firstly dipped into a solution with isobutyl chloroformate as derivatization reagent and isooctane as extraction solvent. Thus, a thin organic liquid membrane coating was developed. Then the modified fiber was immersed into sample solution to extract four important bioamines. Afterwards, the fiber was directly inserted into gas chromatography injection port for thermal desorption. 1,7‐Diaminoheptane was employed as internal standard reagent for quantification of the targets. The limits of detection of the method were 2.98–45.3 μg/kg. The proposed method was successfully applied to the detection of bioamines in several fish samples with recoveries ranging 78.9–110%. The organic reagent used for extraction was as few as microliter that can greatly reduce the harm to manipulator and environment. Moreover, the extraction procedures were very simple without concentration and elution procedures, which can greatly simplify the pretreatment process. The assay can be extended to the in situ screening of other pollutant in food safety by changing the derivatization reagent.     

Headspace stir bar sorptive extraction followed by thermal desorption and gas chromatography with mass spectrometry to determine musk fragrances in sludge samples without sample pretreatment

A direct, simple and solvent‐free method based on headspace stir bar sorptive extraction and thermal desorption gas chromatography with mass spectroscopy was developed to determine 13 musk fragrances (six polycyclic musks, three nitro musks and four macrocyclic musks) in sludge without sample treatment. The optimal headspace stir bar sorptive extraction conditions were achieved when a polydimethylsiloxane stir bar was exposed for 45 min in the headspace of a 10 mL vial filled with 100 mg of sludge mixed with 0.2 mL of water stirred at 750 rpm at 80°C. The stir bar was then desorbed in the thermal desorption gas chromatography and mass spectrometry system, obtaining limits of detection between 5 and 30 ng/g. The method applicability was tested with sewage sludge from two urban wastewater treatment plants and from a potable water treatment plant. Results showed galaxolide and tonalide to be the most abundant musk fragrances found in wastewater treatment plants with maximal concentrations of 9240 and 7500 ng/g, respectively. Maximum concentration levels between 35 and 635 ng/g were found for musk ketone, musk moskene, traseolide, phantolide and celestolide in this kind of samples. Concentrations below the limits of quantitation of phantolide, galaxolide, tonalide and musk ketone were found in sludge from a potable water treatment plant.     

High-performance ion mobility spectrometry with direct electrospray ionization (ESI-HPIMS) for the detection of additives and contaminants in food

High-performance ion mobility spectrometry (HPIMS) with an electrospray ionization (ESI) source detected a series of food contaminants and additive compounds identified as critical to monitoring the safety of food samples. These compounds included twelve phthalate plasticizers, legal and illegal food and cosmetic dyes, and artificial sweeteners that were all denoted as detection priorities. HPIMS separated and detected the range of compounds with a resolving power better than 60 in both positive and negative ion modes, comparable to the commonly used high-performance liquid chromatography (HPLC) methods, but with most acquisition times under a minute. The reduced mobilities, K₀, have been determined, as have the linear response ranges for ESI-HPIMS, which are 1.5–2 orders of magnitude for concentrations down to sub-ng μL⁻¹ levels. At least one unique mobility peak was seen for two subsets of the phthalates grouped by the country where they were banned. Furthermore, ESI-HPIMS successfully detected low nanogram levels of a phthalate at up to 30 times lower concentration than international detection levels in both a cola matrix and a soy-based bubble tea beverage using only a simplified sample treatment. A newly developed direct ESI source (Directspray) was combined with HPIMS to detect food-grade dyes and industrial dye adulterants, as well as the sweeteners sodium saccharin and sodium cyclamate, with the same good performance as with the phthalates. However, the Directspray method eliminated sources of carryover and decreased the time between sample runs. Limits-of-detection (LOD) for the analyte standards were estimated to be sub-ng μL⁻¹ levels without extensive sample handling or preparation.     

Pressurised hot water extraction followed by simultaneous derivatization and headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry for the determination of aliphatic primary amines in sewage sludge

In this paper we describe an environmentally friendly and sensitive method for the determination of ten primary amines in sewage sludge. The method is based on pressurised hot water extraction (PHWE) followed by simultaneous derivatization with pentafluorobenzaldehyde (PFBAY) and headspace solid-phase microextraction (HS-SPME) and subsequent gas-chromatography ion-trap tandem mass spectrometry (GC-IT-MS-MS) analysis. The influence of the main factors on the PHWE of sludge was optimized by a central composite design. For all species the optimal conditions were water at pH 4 as the extracting solvent, an extraction temperature of 100 °C and an extraction time of 15 min. The separation and detection of the ten amines by GC-IT-MS-MS took just 10 min and the entire process took approximately 1 h. Repeatability and reproducibility between days, expressed as RSD (%) (n = 5), were less than 19 and 24%, respectively. The average limit of detection (LOD) was of 65 μg kg⁻¹ s (range found 9-135) and the average limit of quantification (LOQ) was of 230 μg kg⁻¹ (range found 50-450) of dry weight (d.w.). Under optimized conditions we used this method to determine the compounds in industrial and municipal sewage sludge samples and in sludge from a potable water treatment plant. Methylamine and isobutylamine showed the highest levels in one of the industrial sewage sludge samples (404 and 543 mg kg⁻¹ (d.w.), respectively). To our knowledge, this paper presents for the first time the determination of ten primary amines in sewage sludge samples using PHWE.     

Comparison of pulse glow discharge‐ion mobility spectrometry and liquid chromatography with tandem mass spectrometry based on multiplug filtration cleanup for the analysis of tricaine mesylate residues in fish and water

Analytical methods based on multiplug filtration cleanup coupled with pulse glow discharge‐ion mobility spectrometry and liquid chromatography tandem mass spectrometry were developed for the analysis of tricaine mesylate residue in fish and fish‐raising water samples. A silica fiber holder and an appropriate new interface were designed to make the direct introduction of the fiber into the pulse glow discharge‐ion mobility spectrometry introduction mechanism. The multiplug filtration cleanup method with adsorption mixtures was optimized for the determination of tricaine mesylate in fish samples. Good linear relationships were obtained by the two methods. For fish samples, limits of detection were 6 and 0.6 μg/kg by ion mobility spectrometry and liquid chromatography with tandem mass spectrometry, respectively. The matrix effect of the established liquid chromatography tandem mass spectrometry method was negligible for fish samples but that of the ion mobility spectrometry method was not. The two methods were compared. The ion mobility spectrometry system could be used a rapid screening tool on site with the advantage of rapidity, simplicity, and portability, and the liquid chromatography tandem mass spectrometry system could be used for validation in laboratory conditions with the advantage of lower limit of detection, stability, and precision.     

A rapid method for simultaneous determination of 14 phenolic compounds in Radix Puerariae using microwave-assisted extraction and ultra high performance liquid chromatography coupled with diode array detection and time-of-flight mass spectrometry

A microwave-assisted extraction (MAE) and ultra high performance liquid chromatography coupled with diode array detection and time-of-flight mass spectrometry (UHPLC-DAD-TOF-MS) method was developed for simultaneous determination of 14 phenolic compounds in the root of Pueraria lobata (Wild.) Ohwi and Pueraria thomsonii Benth. Operational conditions of MAE were optimized by central composite design (CCD). The optimized result was 65% ethanol as extraction solvent, 17 mL of extraction volume, 100 °C of extraction temperature and 2 min of hold time. A Zorbax SB C₁₈ (50 mm × 4.6 mm I.D., 1.8 μm) and gradient elution were used during the analysis. The chromatographic peaks of 14 investigated compounds in samples were successfully identified by comparing their retention time, UV spectra and TOF mass data with the reference substances. All calibration curves showed good linearity (r > 0.9997) within the test ranges. The intra-day and inter-day variations were less than 1.77% and 2.88%, respectively. The developed method was successfully applied to determine the investigated compounds in 10 samples of Radix Puerariae Lobatae and Radix Puerariae Thomsonii, respectively. The result indicated that MAE and UHPLC-DAD-TOF-MS system might provide a rapid method for the quality control of Radix Puerariae.