Bis Trimethylsilyl Trifluoroacetamide Research Articles

Determination of benzophenone derivatives in wastewater by GC–MS/MS combined with in‐port derivatization

AbstractThe analysis of UV filters (UVFs) in water has become increasingly important due to their adverse effects on aquatic organisms and humans. This study describes a method for the determination of benzophenone derivatives UVF in wastewater samples. The selected UVFs are 2‐hydroxy‐4‐methoxybenzophenone (BP‐3), 2,4‐dihydroxybenzophenone (BP‐1), 4‐hydroxybenzophenone (4HB), 2,2′‐dihydroxy‐4‐methoxybenzophenone (DHMB) and lastly, 4,4′‐dihydroxybenzophenone (4DHB). The method includes solid‐phase extraction (SPE) of analytes from wastewater followed by on‐line derivatization with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and analysis with GC‐MS/MS. Method validation studies resulted in good recoveries (86–112%), relative standard deviation RSD = 0.8 and 7.3%, the limits of detection LODs = 1.00–10.8 ng/L, and the limits of quantification LOQs = 3.00–32.3 ng/L. The method was successfully applied to domestic wastewater samples collected from influent and effluent of touristic hotels’ biological wastewater treatment plants. BP‐3 (24–1765 ng/L), BP‐1 (8–703 ng/L), 4HB (26–96 ng/L), and 4DHB (20–22 ng/L) were the common benzophenone derivatives in the influent wastewater while effluent contained mainly BP‐1 (8–32 ng/L), 4HB (12–57 ng/L) and 4DHB (20–102 ng/L). These results indicate that BP‐3 and BP‐1 are biodegraded in the treatment processes. However, 4HB and 4DHB are resistant to degradation and they are the main benzophenone metabolites discharged to receiving media.

Collection of Alfalfa Root Exudates to Study the Impact of Di(2-ethylhexyl) Phthalate on Metabolite Production.

Root exudates are the main media of information communication and energy transfer between plant roots and the surrounding environment. The change in secretion of root exudates is usually an external detoxification strategy for plants under stress conditions. This protocol aims to introduce general guidelines for the collection of alfalfa root exudates to study the impact of di(2-ethylhexyl) phthalate (DEHP) on metabolite production. First, alfalfa seedlings are grown under DEHP stress in a hydroponic culture experiment. Second, the plants are transferred to centrifuge tubes containing 50 mL of sterilized ultrapure water for 6 h to collect root exudates. The solutions are then freeze-dried in a vacuum freeze dryer. The frozen samples are extracted and derivatized with bis(trimethylsilyl)) trifluoroacetamide (BSTFA) reagent. Subsequently, the derivatized extracts are measured using a gas chromatograph system coupled with a time-of-flight mass spectrometer (GC-TOF-MS). The acquired metabolite data are then analyzed based on bioinformatic methods. Differential metabolites and significantly changed metabolism pathways should be deeply explored to reveal the impact of DEHP on alfalfa in view of root exudates.

Rapid screening of Chemical Weapons Convention-related chemicals in oil matrix by headspace solid-phase microextraction and gas chromatography-mass spectrometry

The Chemical Weapons Convention (CWC) requires verification of a large number of compounds with different types and properties. The results of the verification are of great political and military sensitivity. However, the sources of verification samples are complex and diverse, and the contents of the target compounds in these samples are usually very low. These issues increase the likelihood of missed or false detection. Thus, establishing rapid and effective screening methods for the accurate identification of CWC-related compounds in complex environmental samples are of great importance. In this study, a fast and simple procedure based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-electron ionization mass spectrometry (GC-EI/MS) in full-scan mode was developed to determine CWC-related chemicals in oil matrix. A total of 24 CWC-related chemicals with different chemical characteristics were selected to simulate the screening procedure. The selected compounds were divided into three groups based on their properties. The first group included volatile and semi-volatile CWC-related compounds with relatively low polarity, which could be extracted by HS-SPME and directly analyzed by GC-MS. The second group included moderately polar compounds with hydroxyl or amino groups; such compounds are related to nerve, blister, and incapacitating agents. The compounds in the third group included non-volatile CWC-related chemicals with relatively strong polarity, such as alkyl methylphosphonic acids and diphenyl hydroxyacetic acid. These compounds must be derivatized into vaporizable derivatives prior to extraction by HS-SPME and analysis by GC-MS. Variables that influence the SPME process, such as fiber type, extraction temperature and time, desorption time, and derivatization protocol, were optimized to improve the sensitivity of the method. The screening procedure for CWC-related compounds in the oil matrix samples included two main steps. First, low-polarity volatile and semi-volatile compounds (i. e. the first group) were extracted by HS-SPME with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibers and analyzed in split-injection mode (split ratio, 10∶1) using GC-MS. The use of a large split ratio can reduce the solvent effect, which is conducive to the detection of low-boiling-point compounds. If necessary, the sample could be extracted once more and analyzed in splitless mode. The derivatization agent bis(trimethylsilyl)trifluoroacetamide (BSTFA) was then added to the sample. Mid- and high-polarity compounds (i. e. the second and third groups) were extracted with polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibers after derivatization and analyzed in splitless mode using GC-MS. The established method exhibited good repeatability and sensitivity. The detection limits for the compounds in the first group ranged from 0.5 ng/mL to 100 ng/mL, whereas the detection limits for the compounds in the second and third groups ranged from 20 ng/mL to 300 ng/mL. Except for compounds with extremely high boiling points and a few compounds that are not suitable for derivatization with BSTFA, the method can be used to analyze most CWC-related compounds in oil matrix samples. In particular, it greatly shortened the preparation time of the oil matrix samples and reduced the loss of low-boiling-point compounds owing to the sample concentration process, thereby avoiding missed detection. The method was successfully applied to the Organization for the Prohibition of Chemical Weapons (OPCW) proficiency tests and proved to be a useful technique for the rapid screening of trace levels of CWC-related chemicals in oil matrix.

Quantitation of Neuroblastoma Markers Homovanillic Acid (HVA) and Vanillylmandelic Acid (VMA) in Urine by Gas Chromatography-Mass Spectrometry (GC/MS).

Neuroblastoma and other neural crest tumors can be characterized by the increased production and excretion of catecholamines and their metabolites. Homovanillic acid (HVA) and vanillylmandelic acid (VMA) are important catecholamine metabolites that can be measured to provide relatively rapid laboratory diagnosis and clinical follow-up of neuroblastoma. We present a procedure to quantify HVA and VMA in urine samples which have been diluted to a creatinine concentration of 2mg/dL. Diluted samples are spiked with deuterated internal standards, acidified, and extracted with an organic solvent. A bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS) and pyridine mixture is added to the dried extract to create trimethylsilyl derivatives of HVA and VMA. The derivatized compounds are measured using gas chromatography-mass spectrometry (GC/MS).

Detection and determination of spectinomycin and lincomycin in poultry muscles and pork by ASE-SPE-GC–MS/MS

An innovative study on the qualitative identification and quantitative determination of spectinomycin and lincomycin residues in poultry (chicken, duck, and goose) muscles and pork using gas chromatography-tandem mass spectrometry (GC–MS/MS) was conducted. The samples were extracted and separated with accelerated solvent extraction (ASE) and then purified and enriched by solid-phase extraction (SPE). Then, the obtained residues were derivatized with 200 μL bis(trimethylsilyl) trifluoroacetamide (BSTFA) for 60 min at 75 °C, and the derivative products were injected into a GC–MS/MS system. Under the optimized conditions, the limits of detection (LODs) and limits of quantification (LOQs) of spectinomycin and lincomycin in samples were 2.5–4.6 μg/kg and 5.7–7.6 μg/kg, respectively, the targets’ recoveries were 79.7 %–94.2 %, the determination coefficients were 0.9992−0.9998, and the relative standard deviations (RSDs) were 1.2 %–3.5 %. The method revealed good linearity, and the parameters met the European Union requirements for the detection of veterinary drug residues. Poultry muscles and pork were procured from local stores for actual sample testing, confirming the feasibility and practicability of this method. Therefore, this study established an ASE-SPE-GC–MS/MS method to detect spectinomycin and lincomycin residues in animal-derived food.

Determination of simple carbohydrates in beer using SPME, on fiber derivatization and gas chromatography mass spectrometry

Fermentable sugars directly contribute to the sweetness of beer, whereas carbohydrates with more than four glycosyl units can be beneficial to the perception of beer in that they contribute to body or mouthfeel. GC/MS has not been widely used for the analysis of carbohydrate contents in beer. The analysis of beer by using L-SPME, on fiber derivatization with bis(trimethylsilyl) trifluoroacetamide (BSTFA) and GC-MS showed the presence of some carbohydrates (D-arabinose, -D-arabinopyranose, D-galactose, Dxylose, and D-mannose) never detected in beer. The analysis of three different types of beer showed that the presence of these carbohydrates can represent a significant part of the total amount of carbohydrates present in the beer.

PSYCHOSOCIAL IMPACT OF PSYCHIATRIC GENETIC TEST RESULTS: ANTICIPATING THE CHALLENGES

An innovative study on the qualitative identification and quantitative determination of spectinomycin and lincomycin residues in poultry (chicken, duck, and goose) muscles and pork using gas chromatography-tandem mass spectrometry (GC–MS/MS) was conducted. The samples were extracted and separated with accelerated solvent extraction (ASE) and then purified and enriched by solid-phase extraction (SPE). Then, the obtained residues were derivatized with 200 μL bis(trimethylsilyl) trifluoroacetamide (BSTFA) for 60 min at 75 °C, and the derivative products were injected into a GC–MS/MS system. Under the optimized conditions, the limits of detection (LODs) and limits of quantification (LOQs) of spectinomycin and lincomycin in samples were 2.5–4.6 μg/kg and 5.7–7.6 μg/kg, respectively, the targets’ recoveries were 79.7 %–94.2 %, the determination coefficients were 0.9992−0.9998, and the relative standard deviations (RSDs) were 1.2 %–3.5 %. The method revealed good linearity, and the parameters met the European Union requirements for the detection of veterinary drug residues. Poultry muscles and pork were procured from local stores for actual sample testing, confirming the feasibility and practicability of this method. Therefore, this study established an ASE-SPE-GC–MS/MS method to detect spectinomycin and lincomycin residues in animal-derived food.

Bio-based succinic acid sample preparation and derivatization procedure optimisation for gas chromatography-mass spectrometry analysis

This study focused on bio-based succinic acid sample preparation and derivatization conditions optimization using GC-MS analytical method. Succinic acid, the precursor of a wide range bio-compounds, especially it is important in accumulation of mitochondrial metabolite succinate (citric acid cycle) and during ischemia controls reperfusion injury through mitochondrial reactive oxygen production. Accurate determination of analytes is the key in metabolomics to use as low molecular biomarkers in case to improve diagnostic methods. Methods. Gas chromatography-mass spectrometry (GC-MS) method. For the quantitative determination of the succinic acid applied derivatization process by silylation using -bis- (trimethylsilyl) -trifluoroacetamide (BSTFA). Results. The derivatization agent BSTFA, the derivatization time of 3-4 hours and derivatization temperature at 70 °C were selected as the optimal derivatization condition for quantification of succinic acid by GС/MS in biological samples. The results show that GC-MS SIM method with evaporation was the most effective to quantify succinate in biological samples after ischemia/reperfusion injury. Selected ion monitoring (SIM) allowed to monitor a subset of fragments with their related mass values in a certain retention time (RT) range for a set of targets. Conclusions. DC – MS has several advantages for measurements of succinate concentration in small kidney tissue samples (lyophilized mitochondria). The method can be applied in small pieces of tissue - biopy samples, tissues from various organs

Determination of cembrenediols in tobacco by gas chromatography—mass spectrometry-selected ion monitoring with precolumn derivatization

An efficient and sensitive analytical method based on precolumn derivatization and gas chromatography—mass spectrometry—selected ion monitoring (GC—MS—SIM) was proposed and validated for analysis of two cembrenediols (CBDs) which are α-cembrenediol and β-cembrenediol in tobacco samples. CBDs in tobacco samples were extracted by sonication with 50 mL dichloromethane for 10 min before derivatized with 2:3 (v/v) bis(trimethylsilyl)trifluoroacetamide (BSTFA)—pyridine at 20 °C for 100 min. CBDs’ level in tobacco samples was analyzed by GC—MS—SIM and quantified by the internal standard method. The linear range for α-CBD and β-CBD was 13.6–554.6 μg mL−1 and 4.11–162.6 μg mL−1, and the correlation coefficients of both were 0.9998. The limit of detection (LOD) and limit of quantification (LOQ) of α-cembrenediol and β-cembrenediol were 0.40 μg g−1 and 1.34 μg g−1, and 0.27 μg g−1 and 0.90 μg g−1, respectively. Average recoveries of α-CBD and β-CBD were 94.4–99.9% and 91.9–98.2% while the relative standard deviations (RSDs, n = 5) were ranged from 2.67 to 5.6% and 2.04 to 4.22%, respectively. This proposed analytical method has been successfully applied to analyze CBDs in tobacco samples.

Improved Efficiency for Partial Oxidation of Methane by Controlled Copper Deposition on Surface-Modified ZSM-5.

The mono(μ‐oxo) dicopper cores present in the pores of Cu‐ZSM‐5 are active for the partial oxidation of methane to methanol. However, copper on the external surface reduces the ratio of active, selective sites to unselective sites. More efficient catalysts are obtained by controlling the copper deposition during synthesis. Herein, the external exchange sites of ZSM‐5 samples were passivated by bis(trimethylsilyl) trifluoroacetamide (BSTFA) followed by calcination, promoting selective deposition of intraporous copper during aqueous copper ion exchange. At an optimum level of 1–2 wt % SiO2, IR studies showed a 64 % relative reduction in external copper species and temperature‐programmed oxidation analysis showed an associated increase in the formation of methanol compared with unmodified Cu‐ZSM‐5 samples. It is, therefore, reported that the modified zeolites contained a significantly higher proportion of active, selective copper species than their unmodified counterparts with activity for partial methane oxidation to methanol.

P-Tolyl isocyanate derivatization for analysis of CWC-related polar degradation products by mass spectrometry

Most of the precursors and/or degradation products related to the Chemical Weapons Convention (CWC) are polar. Identification of these molecules in environmental samples provides clues regarding the alleged usage and/or synthesis of the parent toxic chemicals. Such polar compounds need to be derivatized in order to analyze them by gas chromatography-mass spectrometry (GC-MS). In this study, we developed a new derivatizing reagent, para-tolyl isocyanate (PTI), for derivatization of polar CWC-related compounds. The PTI reagent selectively derivatizes the -OH and/or-SH functional groups with high efficiency, but does not react with carboxylic acid (-COOH) or phosphonic acid (-(O)P(OH)2) groups. The PTI derivatives of dialkyl aminoethanols, dialkyl aminoethanol-N-oxides, and 3-quinuclidinol were successfully eluted through GC, and their electron ionization (EI) mass spectra were distinct and provided the structure information by which the isomeric compounds can be easily distinguished. We also calculated the GC-retention index values that can be used for further confirmation of the target compounds. All the studied PTI derivatives can be analyzed by EI-MS with direct insertion probe and/or by direct electrospray ionization mass spectrometry (ESI-MS) together with the MS-MS data; both sets of data provide full structure information. The PTI reagent was found to be better in some respects than the conventional bistrimethylsilyl trifluoroacetamide (BSTFA), a trimethyl silylating reagent. The PTI reagent is commercially available, and the PTI derivatives are highly stable for months and are not sensitive to moisture. The applicability of the PTI derivatization for trace-level determination of the target CWC-related polar compounds in environmental matrices and in human plasma samples is also evaluated.

Use of hydroxylapatite composite membranes for analysis of bisphenol A

This study evaluates solid-phase micro-extraction (SPME) coupled with gas chromatography–mass spectrometry (GC–MS) to determine trace levels of bis-phenol A in water and leached from plastic containers. In our study, we used very thin composite membranes prepared in the laboratory. The extraction using headspace post-derivatization with bis(trimethylsilyl) trifluoroacetamide (BSTFA), containing 1 % trimethylchlorosilane (TMCS) vapor, following SPME was compared with extraction without derivatization. The SPME experimental procedures to extract bis-phenol A in water were optimized with a relatively polar polyacrylate (PA)-coated fiber, an extraction time of 50 min, and desorption at 300 °C for 2 min. Headspace derivatization following SPME was performed using 7 μL of BSTFA with 1 % TMCS at 65 °C for 30 s. The precision was 5.2 % without derivatization and 9.0 % headspace derivatization. The detection limit was determined to be at the nanogram per liter level. When SPME was used following headspace derivatization, the detection limit was one order of magnitude better than that achieved without derivatization. The results of this study reveal the adequacy of the SPME–GC–MS method for analyzing bisphenol A leached from plastic containers. The concentrations of bisphenol A leached from plastic containers into water ranged from 0.7 to 78.5 μg L−1.

Determination of 4-Hydroxy-2-Nonenal in Plasma

Protocol 1. Place freshly taken plasma (1.0 mL), BHT (2.0 mM, 0.010 mL), and nonanoic acid (internal standard; 0.006 mL) in new clean glass tubes. 2. Mix and divide into equal parts 'A' and 'B'. 3. Add chloroform-methanol (2: 1 v/v, 4.0 mL) and NaCI (0.15 M, 0.4 mL) to each tube. 4. Purge with oxygen-free nitrogen for 2 min, cap, and vortex mix for 30 s. 5. Centrifuge at 5,000 rpm for 6 min at 4°C. 6. Remove lower (chloroform) layer, and store at 4°C A, under N2. 7. Extract the remaining (upper) residue with chloroformmethanol (2:1 v/v 2 mL) by vortex mixing for 30 s. 8. Centrifuge at 5,000 rpm for 6 min at 4°C. 9. Collect the lower phase and combine with previous extract. 10. Evaporate combined extracts to dryness under N2 at 25°C. 11. Store at –20°C for less than 1 week. 12. Derivatize the samples: a. Add dry acetone (0.2 mL) and bis(trimethylsilyl) trifluoroacetamide (BSTFA) containing 1% (w/v) trimethylchlorosilane (0.2 mL) to the dried extracts. b. Cap tubes and leave for 60 min at 25°C. c. Centrifuge at 6,000 rpm for 5 min to deposit residues. 13. Analyse by GC-MS.

엔진윤활유 중 Ethylene Glycol의 용제추출후 bistrimethylsilyltrifluoroacetamide(BSTFA)를 이용한 GC/MS 분석에 관한 연구

For proper functioning, general machines usually need lubricant oil as a cooling, cleaning, and sealing agent at points of mechanical contact. The quality of lubricant oil can deteriorate during operation owing to various causes such as high temperature, combustion products and extraneous impurities. In this study, a heavy load stopped during operation, and the oil was analyzed to check whether any impurities were added. Extraction using acetonitrile followed by reaction with BSTFA(bistrimethylsilyl trifluoroacetamide) showed that, trimethylsilylated ethylene glycol was present in the lubricant oil. To quantify the ethylene glycol in the oil, deuterium-substituted ethylene glycol, which acted as an internal standard, was added to the sample and then extracted with the solvent. Next, the extract was reacted with the derivatizing agent(BSTFA) and then analyzed with GC/MS. The detection limit of this method was found to be <TEX>$0.5{\mu}g/g$</TEX> and the recovery of oil containing <TEX>$20,000{\mu}g/g$</TEX> of ethylene glycol was measured to be 94.8%. A damaged O-ring and eroded cylinder liner were found during the overhaul, which implied the leakage of coolant containing ethylene glycol into the lubricating system. The erosion of the cylinder liner was assumed to be due to cavitation of the coolant in the cooling system.

Determination of ethyl glucuronide in human urine by solid phase extraction-gas chromatography-mass spectrometry

A solid phase extraction (SPE) and gas chromatography (GC) with mass spectrometry (MS) method for determination of ethyl glucuronide (EtG) in human urine was established. One mL urine sample was deproteinated by 100 microL 3 mol/L hydrochloric acid and cleaned up through a solid phase extraction column. The target analytes were eluted from an NH2-column with 4% ammonia solution and then treated with bis (trimethylsilyl) trifluoroacetamide (BSTFA) + trimethylchlorosilane (TMCS) (99:1) for derivatization. The derivatized samples were analyzed by GC-MS. Data were acquired in the selected ion monitoring (SIM) mode and the quantitation of EtG was done through internal standard method. Good linearity was obtained at the mass concentration range of 0.1 - 3.2 mg/L with a correlation coefficient (r) of 0.9921. The limit of detection (LOD) was 28.4 microg/L. The range of recoveries was 92.5% - 108.7%, and the relative standard deviations (RSDs) of intra-day and inter-day were all less than 5%. This method is sensitive, specific, accurate and can be applied to the determination of EtG for medicolegal identification and clinical laboratory.

Distribution Analysis of Organic Pollutants in Paper Mill Wastewater

Gas chromatography-mass spectrometry(GC-MS) was employed for the determination of organic pollutants in recirculating water of a paper-recycling industry.Origins of the detected organics and potential pollutions on the environment and human being were discussed.Their contents in water at different production stages were compared.Water samples were first pre-treated by liquid-liquid extraction using methyl tert-butylether(MTBE) with the presence of heptadecanoic acid(C17) as the internal standard.They were then treated by bis(trimethylsilyl)trifluoroacetamide(BSTFA) and trimethylchlorosilane(TMCS) in pyridine,followed by GC-MS analysis for the detection of respective trimethylsilyl esters formed at different stages.Using this approach,nearly 50 kinds of organic chemicals,such as resin acids,fatty acids,additives and their ramifications were detected in the processed water.And the resin acids were mainly existed in pulping water,which may come from secondary fibers and sizing agents.The fatty acids,aromatic acids and their derivatives,which may come from secondary fibers,impurities and additives,such as printing ink,plastic matters,surface active agents,were mainly existed in the white water and mixed water coming out of the mill.It was found that the mixed water contained most kinds of organic chemicals while the vacuum pumping water contained the least organic chemicals.The main chemicals contained in vacuum water were aromatic acids.There are large mounts of fatty acids,aromatic acids and theirs derivations in the wastewater of each papermaking processes,most of them are brought by the adding of secondary fiber and other additives.These organics are harmful to the environment,and difficult to be eliminated by sedimentation and flocculation.Therefore,in order to reduce the pollution of the organic pollutants in effluent wastewater,it is necessary to avoid adding phthalic acid and ester of phthalic acid.The addition of additives of long chain fatty acids and aromatic compound should be minimized in the papermaking processes.

Enrichment of H217O from Tap Water, Characterization of the Enriched Water, and Properties of Several 17O-Labeled Compounds

A low-abundance form of water, H(2)(17)O, was enriched from 0.04% to ∼90% by slow evaporation and fractional distillation of tap water. The density and refractive index for H(2)(17)O are reported. Gas chromatography-mass spectrometry (GC-MS) of (16)O- and (17)O-1-hexanols and their trimethyl silyl ethers and of (16)O- and (17)O-hexamethyl disiloxanes was used to determine the percentage of (17)O enrichment in the H(2)(17)O. Furthermore, the chemical shifts of labeled and nonlabeled water dissolved in CDCl(3) differed sufficiently that we could verify the enrichment of H(2)(17)O. (17)O hexanol was synthesized by the reaction of iodohexane with Na(17)OH. (17)O-Labeled trimethylsilanol and (17)O-labeled hexamethyldisiloxane were prepared by the reaction of H(2)(17)O with bis(trimethylsilyl)trifluoroacetamide (BSTFA). To generate standards for (17)O NMR, H(2)(17)O(2), and (17)O camphor were prepared. H(2)(17)O was electrolyzed to form (17)O-labeled hydrogen peroxide which was quantified using two colorimetric assays. (17)O-Labeled camphor was prepared by exchanging the ketone oxygen of camphor using H(2)(17)O. The (17)O-labeled compounds were characterized using (17)O, (1)H, and (13)C NMR and GC-MS. While we were characterizing the labeled camphor, we also detected an unexpected oxygen exchange reaction of primary alcohols, catalyzed by electrophilic ketones such as camphor. The reaction is a displacement of the alcohol OH group by water. This is an example of the usefulness of (17)O NMR in the study of a reaction mechanism that has not been noticed previously.

Determination of melamine and its analogues in egg by gas chromatography-tandem mass spectrometry using an isotope dilution technique

A method was developed for the simultaneous determination of melamine, ammeline, ammelide, and cyanuric acid in egg using gas chromatography-tandem mass spectrometry (GC-MS/MS). The samples were first extracted by the solution of diethylamine–water–acetonitrile (10:40:50, v/v/v). Clean-up employed an ‘On Guard II’ RP cartridge, and the dried elute was derivatised using bis-(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS). Derivatised samples were analysed by GC-MS/MS using multiple-reaction monitoring (MRM) with 13C3-15N3-labelled melamine and cyanuric acid as internal standards. Blank samples of egg were spiked with the four analytes at concentration level of 0.1, 0.5, 1.0 mg kg−1, and the intra-day and inter-day recoveries were in the range 75.7–122.5% with the relative standard deviation (RSD) from 2.6% to 22.8%. Decision limits (CCα, α = 0.01) for melamine, ammeline, ammelide, and cyanuric acid in egg samples and milk powder were 3.5–5.9 and 2.5 to 3.8 µg kg−1, and the detection capabilities (CCβ, β = 0.05) were 4.9–8.4 and 3.6–9.5 µg kg−1, respectively. The method was successfully applied to egg samples and milk products as well. Satisfactory results were obtained as part of the 2009 European Union melamine proficiency test.

Determination of melamine and cyanuric acid in powdered milk using injection-port derivatization and gas chromatography–tandem mass spectrometry with furan chemical ionization

A reliable, sensitive and eco-friendly injection-port trimethylsilylated (TMS) derivatization and gas chromatography–tandem mass spectrometry (GC–MS/MS) with furan chemical ionization (furan-CI) method was developed to determine melamine and cyanuric acid in powdered milk samples. The effects of several parameters related to the TMS-derivatization process (i.e., injection-port temperature, residence time and volume of silylating agent) and of various CI agents were investigated. Addition of a solution (3 μL) of bis(trimethyl)silyltrifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane (TMCS) reagent to a 20-μL extract from the powdered milk sample gave an excellent yield of the tris-TMS-derivatives of melamine and cyanuric acid at an injection-port temperature of 90 °C. Furthermore, using furan as the CI agent in conjunction with tandem mass spectrometry provided the greatest sensitivity and selectivity of detection. The limits of quantitation (LOQs) for melamine and cyanuric acid were 0.5 and 1.0 ng/g in 0.5-g of powdered milk samples, respectively. The recoveries from spiked samples – after simple ultra-sonication with 5% dimethyl sulfoxide in acetonitrile coupled with n-hexane liquid–liquid extraction – ranged from 72% to 93% with relative standard deviations of lower than or equal to 18%. In three of four real powdered milk samples, melamine was detected at concentrations ranging from 36 to 1460 ng/g; and cyanuric acid was detected in two of these samples at concentrations of 17 and 180 ng/g.

Determination of selected non-steroidal anti-inflammatory drugs in wastewater by gas chromatography-mass spectrometry

An analytical method for the simultaneous determination of the four most detected non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater, namely ibuprofen (IBF), naproxen (NPX), diclofenac (DFC) and ketoprofen (KFN), was developed based on gas chromatography–mass spectrometry (GC-MS). Extraction from wastewater samples was performed by solid-phase extraction (SPE) with C18 cartridges, while meclofenamic acid (MFC) was used as surrogate. The optimisation of SPE procedure included the type of the extraction solvent used for the elution and the pH of the loading solution (acidic or neutral). The developed extraction procedure resulted in good repeatability and reproducibility with relative standard deviations (RSDs) less than 10% for all the compounds. Moreover, satisfactory recoveries (>98%) were obtained. Chromatographic analysis was achieved after derivatisation with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% trimethyl chlorosilane (TMCS) in the presence of pyridine, a derivatisation mixture used for the first time for these compounds. The limits of detection (LODs) of the method varied from 0.37 (KFN) to 3.1 ng L−1 (NPX). The analytical method was successfully applied for the determination of these compounds in the raw and treated wastewater of two different wastewater treatment plants (WWTPs) of the city of Mytilene in Lesvos, Greece. The maximum concentrations were detected in raw wastewater originated from a hospital and they were 574 ng L−1 and 704 ng L−1 for IBF and KFN, respectively.