Multi-residue method for trace level determination of pharmaceuticals in solid samples using pressurized liquid extraction followed by liquid chromatography/quadrupole-linear ion trap mass spectrometry

A simple and sensitive method for simultaneous analysis of 43 pharmaceutical compounds in sewage sludge and sediment samples was developed and validated. The target compounds were extracted using pressurized liquid extraction (PLE) and then purified and pre-concentrated by solid phase extraction (SPE) using a hydrophilic-lipophilic balanced polymer. PLE extraction was performed on temperature of 100 °C, with methanol/water mixture (1/2, v/v) as extraction solvent. The quantitative analysis was performed by liquid chromatography tandem mass spectrometry using a hybrid triple quadrupole-linear ion trap mass spectrometer (LC-QqLIT-MS). Data acquisition was carried out in selected reaction monitoring (SRM) mode, monitoring two SRM transitions to ensure an accurate identification of target compounds in the samples. Additional identification and confirmation of target compounds were performed using the Information Dependent Acquisition (IDA) function. The method was validated through the estimation of the linearity, sensitivity, repeatability, reproducibility and matrix effects. The internal standard approach was used for quantification because it efficiently corrected matrix effects. Despite the strong matrix interferences, the recoveries were generally higher of 50% in both matrixes and the detection and quantification limits were very low. Beside the very good sensitivity provided by LC-QqLIT-MS, an important characteristic of the method is that all the target compounds can be simultaneously extracted, treated and analysed. Hence, it can be used for routine analysis of pharmaceuticals providing large amount of data. The method was applied for the analysis of pharmaceuticals in river sediment and wastewater sludge from three treatment plants with different treatment properties (i.e. capacity, secondary treatment, quality of influent waters). The analysis showed a widespread occurrence of pharmaceuticals in the sludge matrices.     

Development of fast screening methods for the analysis of veterinary drug residues in milk by liquid chromatography-triple quadrupole mass spectrometry

Two rapid multi-residue screening methods for the determination of 21 veterinary drugs in milk by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) have been developed and compared. For both methods, veterinary drugs were extracted from milk samples using a rapid extraction procedure based on the modification of the well-known QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method, and no further clean-up steps were necessary. One screening method was based on the selection of a characteristic neutral loss or product ion of the various families of compounds, whereas another one was based on the choice of a selected reaction monitoring (SRM) for each compound. These methods were compared with regards to false negatives, cut-off values and the unreliability region. The total run time for both methods was 3 min, allowing quick selection of samples that contained veterinary drugs. Non-negative samples were re-analyzed by the UHPLC-MS/MS confirmation/quantification method, which consisted in the monitoring of two SRM for each compound. The methods were validated according to international guides. The proposed analytical methods allow for the identification and confirmation of the target veterinary drugs at trace levels employing quick analysis time.     

Pressurized liquid extraction combined with capillary electrophoresis-mass spectrometry as an improved methodology for the determination of sulfonamide residues in meat

A new analytical method, based on capillary electrophoresis and tandem mass spectrometry (CE-MS2), is proposed and validated for the identification and simultaneous quantification of 12 sulfonamides (SAs) in pork meat. The studied SAs include sulfathiazole, sulfadiazine, sulfamethoxypyridazine, sulfaguanidine, sulfanilamide, sulfadimethoxyne, sulfapyridine, sulfachloropyridazine, sulfisoxazole, sulfasalazine, sulfabenzamide and sulfadimidine. Different parameters (i.e. separation buffer, sheath liquid, electrospray conditions) were optimized to obtain an adequate CE separation and high MS sensitivity. MS2 experiments using an ion trap as analyzer, operating in the selected reaction monitoring (SRM) mode, were carried out to achieve the required number of identification points according to the 2002/657/EC European Decision. For the quantification in pork tissue samples, a pressurized liquid extraction (PLE) procedure, using hot water as extractant followed by an Oasis HLB cleanup, was developed. Linearity (r between 0.996 and 0.997), precision (RSD<14 %) and recoveries (from 76 to 98%) were satisfactory. The limits of detection and quantification (below 12.5 and 46.5 microg kg(-1), respectively) were in all cases lower than the maximum residue limits (MRLs), indicating the potential of CE-MS2 for the analysis of SAs, in the food quality and safety control areas.     

Simultaneous analysis of serotonin, melatonin, piceid and resveratrol in fruits using liquid chromatography tandem mass spectrometry

An analytical method was developed for the simultaneous quantification of serotonin, melatonin, trans- and cis-piceid, and trans- and cis-resveratrol using reversed-phase high performance liquid chromatography coupled to mass spectrometry (HPLC-MS) with electrospray ionization (ESI) in both positive and negative ionization modes. HPLC optimal analytical separation was achieved using a mixture of acetonitrile and water with 0.1% formic acid as the mobile phase in linear gradient elution. The mass spectrometry parameters were optimized for reliable quantification and the enhanced selectivity and sensitivity selected reaction monitoring mode (SRM) was applied. For extraction, the direct analysis of initial methanol extracts was compared with further ethyl acetate extraction. In order to demonstrate the applicability of this analytical method, serotonin, melatonin, trans- and cis-piceid, and trans- and cis-resveratrol from 24 kinds of commonly consumed fruits were quantified. The highest serotonin content was found in plantain, while orange bell peppers had the highest melatonin content. Grape samples possessed higher trans- and cis-piceid, and trans- and cis-resveratrol contents than the other fruits. The results indicate that the combination of HPLC-MS detection and simple sample preparation allows the rapid and accurate quantification of serotonin, melatonin, trans- and cis-piceid, and trans- and cis-resveratrol in fruits.     

Fast liquid chromatography–quadrupole-linear ion trap mass spectrometry for the analysis of pharmaceuticals and hormones in water resources

This paper presents the development of a fast multi-residue method for the determination of 49 pharmaceuticals and 6 metabolites from different therapeutic classes in water resources by means of Ultra-performance™ liquid chromatography (UPLC) coupled to tandem mass spectrometry. The use of the UPLC technology enabled all the 55 compounds to be separated chromatographically in less than 9 min (6.3 min positive mode and 2.7 min negative mode) and with a total analysis time of 18 min when considering column conditioning. Improved resolution, sensitivity and a reduction of matrix effects were obtained under these conditions. Unequivocal identification and quantification of the target compounds was also performed by using the dual acquisition modes of the hybrid triple quadrupole-linear ion trap (QqLIT) system. Triple quadrupole mode by means of selected reaction monitoring (SRM) was used for quantification, whilst a second SRM transition together with information-dependent analysis (IDA) experiments was used for confirmation. Additionally, one general, single solid-phase extraction (SPE) method was developed by using Oasis HLB cartridges. Quality parameters of the method in wastewaters were established obtaining a fast, robust, reproducible and cost-effective method for all the target pharmaceuticals. Finally, the optimized SPE-UPLC/QqLIT method was used for the analysis of the target compounds in wastewaters from Spain. Thirty-one out of fifty-five compounds were identified in the samples collected.     

Hydrophilic interaction liquid chromatography/tandem mass spectrometry for the analysis of diallyldimethylammonium chloride in water

We report a selective, sensitive and fast liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of diallyldimethylammonium chloride (DADMAC) in water. Hydrophilic interaction liquid chromatography (HILIC) was used to avoid ion-pairing reagents, which are generally employed to retain cationic compounds. The complementary information obtained in a triple quadrupole mass spectrometer and in an ion trap Orbitrap has been used to study the fragmentation of the DADMAC cation [M](+) and for the correct assignment of the products ions. The HILIC/MS/MS method developed, using electrospray ionization in positive ion mode and selected reaction monitoring (SRM) acquisition mode, led to a reliable determination and confirmation of the DADMAC cation in water samples down to 50 ng L(-1). The low detection limit achieved, in combination with the absence of matrix effects, allowed the direct analysis of samples without any pretreatment, preconcentration or clean-up step. DADMAC was determined in samples collected in a drinking water treatment plant (DWTP) in Barcelona (Spain) and it was found in the influent at the μg L(-1) level.     

A reliable analytical approach based on gas chromatography coupled to triple quadrupole and time‐of‐flight mass analyzers for the determination and confirmation of polycyclic aromatic hydrocarbons in complex matrices from aquaculture activities

The potential of gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole analyzer (QqQ) has been investigated for the quantification and reliable identification of sixteen polycyclic aromatic hydrocarbons (PAHs) from the EPA priority list in animal and vegetable samples from aquaculture activities, whose fat content ranged from 5 to 100%. Matrices analyzed included fish fillet, fish feed, fish oil and linseed oil. Combining optimized saponification and solid‐phase extraction led to high efficiency in the elimination of interfering compounds, mainly fat, from the extracts. The developed procedure minimized the presence of these interfering compounds in the extracts and provided satisfactory recoveries of PAHs. The excellent sensitivity and selectivity of GC/(QqQ)MS/MS in selected reaction monitoring (SRM) allowed to reach limits of detection at pg/g levels. Two SRM transitions were acquired for each analyte to ensure reliable identification of compounds detected in samples. Confirmation of positive findings was performed by GC coupled to high‐resolution time‐of‐flight mass spectrometry (GC/TOFMS). The accurate mass information provided by GC/TOFMS in full acquisition mode together with its high mass resolution makes it a powerful analytical tool for the unequivocal confirmation of PAHs in the matrices tested. The method developed was applied to the analysis of real‐world samples of each matrix studied with the result of detecting and confirming the majority of analytes at the µg/kg level by both QqQ and TOF mass spectrometers. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of eight nitrosamines in water at the ng L(-1) levels by liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry

In this work, we have developed a sensitive method for detection and quantification of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMor), N-nitrosomethylethylamine (NMEA), N-nitrosopirrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitroso-n-dipropylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) in drinking water. The method is based on liquid chromatography coupled to tandem mass spectrometry, using atmospheric pressure chemical ionization (APCI) in positive mode with a triple quadrupole analyzer (QqQ). The simultaneous acquisition of two MS/MS transitions in selected reaction monitoring mode (SRM) for each compound, together with the evaluation of their relative intensity, allowed the simultaneous quantification and reliable identification in water at ppt levels. Empirical formula of the product ions selected was confirmed by UHPLC-(Q)TOF MS accurate mass measurements from reference standards. Prior to LC-MS/MS QqQ analysis, a preconcentration step by off-line SPE using coconut charcoal EPA 521 cartridges (by passing 500 mL of water sample) was necessary to improve the sensitivity and to meet regulation requirements. For accurate quantification, two isotope labelled nitrosamines (NDMA-d(6) and NDPA-d(14)) were added as surrogate internal standards to the samples. The optimized method was validated at two concentration levels (10 and 100 ng L(-1)) in drinking water samples, obtaining satisfactory recoveries (between 90 and 120%) and precision (RSD<20%). Limits of detection were found to be in the range of 1-8 ng L(-1). The described methodology has been applied to different types of water samples: chlorinated from drinking water and wastewater treatment plants (DWTP and WWTP, respectively), wastewaters subjected to ozonation and tap waters.     

Simultaneous determination of acidic,neutral and basic pharmaceuticals in urban wastewater by ultra high-pressure liquid chromatography-tandem mass spectrometry

In this work, an ultra high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method has been developed for the simultaneous quantification and confirmation of the 20 most consumed pharmaceuticals in Spain in urban wastewater and surface water samples. The scope of the method included acidic, neutral and basic compounds belonging to different therapeutic classes and allows their simultaneous determination in just a single injection, giving realistic information of the most widely consumed pharmaceuticals in only one analysis. An enrichment step based on solid-phase extraction using Oasis HLB cartridges was carried out, followed by UHPLC-MS/MS measurement with a fast-acquisition triple quadrupole mass analyzer. It allowed working with short dwell times and made possible to acquire three simultaneous SRM transitions per compound to assure a reliable identification. Several isotope-labelled internal standards were used as surrogates to correct SPE losses, as well as matrix effects that notably affect quantification of analytes. The method was validated in surface water and effluent and influent urban wastewater at different concentrations from 0.005 μg/L (surface water) to 1.25 μg/L (influent wastewater). The optimized method was applied to the analysis of 84 urban wastewater samples (influent and effluent), with the result that 17 out of 20 compounds monitored were detected in the samples. Analgesics and anti-inflamatories, cholesterol lowering statin drugs and lipid regulators were the major groups found, with diclofenac, ketoprofen, naproxen, 4-aminoantipyrine, bezafibrate, gemfibrozil and venlafaxine being the most frequently detected. The highest concentration level reached was 277 μg/L for salicylic acid in influent wastewater.     

Determination of hydrazine in drinking water: Development and multivariate optimization of a rapid and simple solid phase microextraction-gas chromatography-triple quadrupole mass spectrometry protocol

In this work, the capabilities of solid phase microextraction were exploited in a fully optimized SPME-GC-QqQ-MS analytical approach for hydrazine assay. A rapid and easy method was obtained by a simple derivatization reaction with propyl chloroformate and pyridine carried out directly in water samples, followed by automated SPME analysis in the same vial without further sample handling. The affinity of the different derivatized compounds obtained towards five commercially available SPME coatings was evaluated, in order to achieve the best extraction efficiency. GC analyses were carried out using a GC-QqQ-MS instrument in selected reaction monitoring (SRM) acquisition mode which has allowed the achievement of high specificity by selecting appropriate precursor–product ion couples improving the capability in analyte identification. The multivariate approach of experimental design was crucial in order to optimize derivatization reaction, SPME process and tandem mass spectrometry parameters. Accuracy of the proposed protocol, tested at 60, 200 and 800 ng L⁻¹, provided satisfactory values (114.2%, 83.6% and 98.6%, respectively), whereas precision (RSD%) at the same concentration levels were of 10.9%, 7.9% and 7.7% respectively. Limit of detection and quantification of 4.4 and 8.3 ng L⁻¹ were obtained. The reliable application of the proposed protocol to real drinking water samples confirmed its capability to be used as analytical tool for routine analyses.     

Method development for the concentration determination of a protein in human plasma utilizing 96-well solid-phase extraction and liquid chromatography/tandem mass spectrometric detection

Although liquid chromatography/tandem mass spectrometry (LC/MS/MS) technology has been widely used for quantitative analysis of small organic molecules, it has been a challenging task to quantitatively analyze protein samples utilizing this technology in biological matrices for pre-clinical and clinical studies. Here we present our initial results in method development for the quantitative determination of rK5 protein concentrations in human plasma samples utilizing LC/MS/MS technology. A protein similar in structure to rK5, but with a slightly reduced molecular weight, was used as internal standard. A 96-well solid-phase extraction procedure was developed to effectively extract protein analytes from plasma samples. Quantitative analysis was obtained by a novel approach of protein monitoring that employed selective reaction monitoring (SRM). Even though mass spectrometry of the internal standard protein gave no fragment ions, SRM monitoring greatly reduced background interference. Using samples prepared in human plasma with sodium EDTA as anticoagulant, a correlation coefficient (r(2)) of 0.9940 was obtained by producing a single standard curve with the injection of six rows of standards with a concentration range from 100 ng/mL to 10 microg/mL. The mean analytical recovery for these standards ranged from 91.5 to 103.6%. The CVs for individual standard levels ranged from 3.7 to 20.9%. The experiment was also repeated using samples prepared in human plasma with sodium heparin as anticoagulant, which produced a correlation coefficient (r(2)) of 0.9952 obtained from a single standard curve with the injection of four rows of standards with a concentration range from 50 ng/mL to 10 microg/mL. The mean analytical recovery for the standards ranged from 96.2 to 104.6%. The CVs for individual standard levels ranged from 2.6 to 15.6%.     

Determination of eight nitrosamines in water at the ng L levels by liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry

In this work, we have developed a sensitive method for detection and quantification of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMor), N-nitrosomethylethylamine (NMEA), N-nitrosopirrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitroso-n-dipropylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) in drinking water. The method is based on liquid chromatography coupled to tandem mass spectrometry, using atmospheric pressure chemical ionization (APCI) in positive mode with a triple quadrupole analyzer (QqQ). The simultaneous acquisition of two MS/MS transitions in selected reaction monitoring mode (SRM) for each compound, together with the evaluation of their relative intensity, allowed the simultaneous quantification and reliable identification in water at ppt levels. Empirical formula of the product ions selected was confirmed by UHPLC-(Q)TOF MS accurate mass measurements from reference standards.Prior to LC–MS/MS QqQ analysis, a preconcentration step by off-line SPE using coconut charcoal EPA 521 cartridges (by passing 500 mL of water sample) was necessary to improve the sensitivity and to meet regulation requirements. For accurate quantification, two isotope labelled nitrosamines (NDMA-d₆ and NDPA-d₁₄) were added as surrogate internal standards to the samples.The optimized method was validated at two concentration levels (10 and 100 ng L⁻¹) in drinking water samples, obtaining satisfactory recoveries (between 90 and 120%) and precision (RSD < 20%). Limits of detection were found to be in the range of 1–8 ng L⁻¹. The described methodology has been applied to different types of water samples: chlorinated from drinking water and wastewater treatment plants (DWTP and WWTP, respectively), wastewaters subjected to ozonation and tap waters.     

超快速液相色谱-串联质谱法快速筛查蔬菜中176种农药的残留量

采用超快速液相色谱-串联质谱(UFLC-MS/MS)技术建立了蔬菜中176种农药残留快速筛查的分析方法。蔬菜样品采用乙腈提取,盐析后无需净化。采用多反应监测-信息关联采集-增强子离子扫描(MRM-IDA-EPI)的复合扫描模式,利用基于EPI谱图和色谱峰峰面积的谱库检索技术,完成了蔬菜中176种农药残留的定性定量分析。所有农药在各自的线性范围内线性关系良好(r＞0.99),除了丁硫克百威和灭蝇胺在3个添加水平下的平均回收率分别为46.8%和53.1%,其余174种农药的平均回收率范围为72.4%～126.4%,相对标准偏差范围为1.0%～18.7%,方法的检出限和定量限范围分别为0.005～2.0 μg/kg和0.1～10 μg/kg。该方法具有快速、灵敏度高、准确度高等优点,适合于蔬菜样品中农药多残留的快速筛查分析。     

Quantification and confirmation of anionic, cationic and neutral pesticides and transformation products in water by on-line solid phase extraction-liquid chromatography-tandem mass spectrometry

Two on-line SPE-LC-ESI-MS/MS methods have been developed for the rapid determination and confirmation of 18 polar pesticides and nine transformation products (TPs) in water samples. Given the very different physico-chemical characteristics of the analytes, it was not feasible the simultaneous determination of all selected compounds in only one method. Thus, it was necessary to use heptafluorobutyric acid and formic acid in order to obtain good retention in the SPE cartridge for basic and acidic analytes, respectively. The developed analytical methodology based on the direct injection of 2 mL of water sample in the system allowed the quantification of all analytes at the 25 ng/L level (LOQ) with limits of detection normally lower than 5 ng/L. Satisfactory recoveries (70-110%) were obtained for most compounds in ground and surface water samples. Some exceptions were found mainly in surface water, due to the ion suppression produced by the higher amount of matrix interferents in these samples. The acquisition of two MS/MS transitions for each compound allowed the reliable confirmation of positive findings even at the LOQ level. The developed methodology was applied to real ground and surface water samples showing the interest of including TPs in monitoring methods, as several of them were found at concentrations higher than that of parent compounds.     

An ion-pairing liquid chromatography/tandem mass spectrometric method for the determination of ethephon residues in vegetables

A rapid, sensitive and selective method has been developed for the direct determination of ethephon residues in vegetables (apple, cherry and tomato). Given the anionic character of ethephon, the use of ion-pairing liquid chromatography (LC) in combination with tandem mass spectrometry (MS/MS, triple quadrupole) allowed its direct determination in these matrices avoiding a derivatisation step and favouring the automation of the method. Samples were extracted with a mixture of dichloromethane/aqueous formic acid (pH 3) (1:1). Then, tetrabutylammonium acetate (TBA) was added as an ion-pairing reagent, and an aliquot of the aqueous extract was directly injected into the LC/MS/MS system. Quantification was performed with matrix-matched standards prepared from blank sample extracts. MS/MS measurements were made in the selected reaction monitoring (SRM) mode, using the most sensitive transition (m/z 107 > 79) for quantification, and up to four additional transitions for confirmation. Quantitative recoveries were obtained for all matrices (between 83% and 96%) at two concentration levels tested (0.05 and 0.5 mg/kg), with relative standard deviations lower than 9% in all cases. The addition of TBA directly into the sample extract contained in the injection vial was found sufficient to obtain satisfactory LC retention for the analyte. Under these conditions, the absence of ion-pairing reagent in the mobile phase minimised the ionisation suppression for ethephon in the MS source, leading to an increase in the sensitivity of the method and reaching limits of detection of 0.02 mg/kg for all matrices investigated. The acquisition of five specific MS/MS transitions for ethephon allowed the simultaneous and reliable quantification and confirmation of the analyte in the samples.     

Determination of three capsaicinoids in Capsicum annuum by pressurized liquid extraction combined with LC‐MS/MS

A new method based on pressurized liquid extraction followed by LC‐MS/MS analysis has been developed for the identification and quantification of three capsaicinoids (capsaicin, dihydrocapsaicin, and nordihydrocapsaicin) in extracts of Capsicum annuum. For the recovery of three capsaicinoids, the efficiency levels of ultrasonic‐assisted extraction, microwave‐assisted extraction, Soxhlet extraction, and pressurized liquid extraction were compared under different conditions. Pressurized liquid extraction resulted in higher yields. Pressurized liquid extractions were performed using methanol; temperature was set at 100°C and pressure at 1500 psi. LC analysis was performed on a Waters XBridge? C₁₈ column (150 × 2.1 mm, id 3.5 μm) eluted by a mobile phase of 0.1% formic acid and ACN. Data acquisition was carried out in multiple reaction monitoring transitions mode, monitoring two‐reaction monitoring transitions to ensure an accurate identification of target compounds in the samples. The proposed method is rapid, simple, and could be utilized for the routine analysis of three capsaicinoids in C. annuum samples.     

Ultra‐trace level determination of diquat and paraquat residues in surface and drinking water using ion‐pair liquid chromatography with tandem mass spectrometry: A comparison of direct injection and solid‐phase extraction methods

Direct injection and solid‐phase extraction methods for the determination of diquat and paraquat in surface and drinking water were developed using liquid chromatography with tandem mass spectrometry. The signal intensities of analytes based on six ion‐pairing reagents were compared with each other, and 12.5 mM nonafluoropentanoic acid was selected as the best suited amongst them. A clean‐up method was developed using Oasis hydrophilic–lipophilic balance; this was compared to the direct injection method, with respect to limits of detection, interference, precision, and accuracy. Limits of quantification of diquat and paraquat were 0.03 and 0.01 μg/L using the direct injection method, and 0.002 and 0.001 μg/L using the hydrophilic–lipophilic balance method. When the hydrophilic–lipophilic balance method was used to analyze target compounds in 114 surface water and 30 drinking water samples, paraquat and diquat were detected within a concentration range of 0.001–0.12 and 0.002–0.038 μg/L in surface water, respectively. When the direct injection method was used to analyze target compounds in the same samples, the detected concentrations of paraquat and diquat were within 25% in samples being >0.015 μg/L using the hydrophilic–lipophilic balance method. The liquid chromatography with tandem mass spectrometry method using direct injection can thus be used for routine monitoring of paraquat and diquat in surface and drinking water.     

GC-MS/MS multi-residue method for the determination of organochlorine pesticides,polychlorinated biphenyls and polybrominated diphenyl ethers in human breast tissues

In this work, a multiresidue method for the quantification and confirmation of around 30 organohalogenated compounds in human breast tissue samples has been developed. Analytes tested included organochlorine (OC) (pesticides and polychlorinated biphenyls) and organobromine (OBr) (polybrominated diphenyl ether) compounds. The approach is based on a simple extraction with hexane, followed by a SPE clean-up using silica cartridges and final measurement by GC coupled to triple quadrupole MS. Analyses were performed in both ionizations, electron impact (EI) (selected reaction monitoring (SRM) mode) and negative chemical ionization (NCI) (selected ion recording (SIR) mode). Three isotopically labeled standards were added before extraction and used as surrogates: HCB-¹³C₆, lindane-D₆ and p,p′-DDE-D₈. The method was validated in terms of accuracy, precision, LOQ and LOD and confirmation reliability, using breast tissue spiked at three concentration levels in the range 1–100 ng/g for OC compounds and at two levels 0.1 and 10 ng/g for OBr compounds (0.5 and 50 ng/g for BDE 209). The usefulness of the developed method was tested by the analysis of real human samples, giving as a result the detection of several OC and OBr compounds in different samples analyzed. The acquisition of at least two SRM transitions (in EI) or ions (in NCI) per analyte allowed positive findings to be confirmed by accomplishment of ion ratios between the quantification and the confirmation transitions or ions.     

Trace analysis of herbicides in wastewaters by a dispersive liquid–liquid microextraction approach and liquid chromatography with quadrupole linear ion trap mass spectrometry: Evaluation of green parameters

An analytical method for determining phenylureas (monuron, isoproturon, diuron, linuron and neburon) and propanil herbicides in wastewater has been developed and validated, and the most significant parameters were compared with the corresponding ones found in the literature, thus showing the method performance. The method involves pre‐concentration by a simple, rapid, sensitive and low environmental toxicity temperature‐controlled ionic liquid dispersive liquid–liquid microextraction procedure. The herbicides were identified and determined by liquid chromatography with a hybrid triple quadrupole linear ion trap mass spectrometer. Data acquisition in selected‐reaction monitoring mode allowed the simultaneous identification and quantification of the analytes using two transitions. The information dependent acquisition scan was performed to carry out the identification of those analytes whose second transition was present at low intensity, also providing extra confirmation for the other analytes. Limits of quantification were in the range 1.0–5.0 ng/L. Good recoveries (95–103%) were obtained for the extraction of the target analytes in wastewater samples. The methodology developed was applied to analyze effluent wastewater samples from a wastewater treatment plant located in an agricultural zone of Almería (Spain) and the results indicated the presence of diuron at mean concentration levels of 73.5 ng/L.     

Determination of residual solvents in bulk pharmaceuticals by thermal desorption/gas chromatography/mass spectrometry

Thermal desorption (TD) techniques followed by capillary GC/MS were applied for the analysis of residual solvents in bulk pharmaceuticals. Solvents desorbed from samples by heating were cryofocused at the head of a capillary column prior to GC/MS analysis. This method requires a very small amount of sample and no sample pretreatment. Desorption temperature was set at the point about 20 degrees C higher than the melting point of each sample individually. The relative standard deviations of this method tested by performing six consecutive analyses of 8 different samples were 1.1 to 3.1%, and analytical results of residual solvents were in agreement with those obtained by direct injection of N,N-dimethylformamide solution of the samples into the GC. This novel TD/GC/MS method was demonstrated to be very useful for the identification and quantification of residual solvents in bulk pharmaceuticals.