Solid phase microextraction and gas chromatography coupled to magnetic sector high resolution mass spectrometry for the ultra-trace determination of contaminants in surface water.

With the aim of monitoring water quality according to the regulations established by the European Union it would be necessary to implement analytical methodologies capable of simultaneously determining a broad range of organic pollutants at ultra-trace levels, allowing for increased sample throughput. In addition, the high number of samples to be analyzed requires a particular focus on setting up fully automated analytical methodologies. In view of that, this study is aimed at the development of a complete automated procedure for the ultra-trace determination of certain pesticides, polycyclic aromatic hydrocarbons (PAHs), brominated diphenyl ethers (BDEs) and polychlorinated biphenyls (PCBs) in surface waters. The proposed method is based on an on-line combination of solid phase microextraction (SPME) and gas chromatography coupled to double-focusing magnetic sector high resolution mass spectrometry (GC-HRMS). SPME as well as GC-HRMS conditions were optimized to achieve maximum extraction efficiency and sensitivity, which was reinforced by using multiple ion detection (MID) as acquisition mode. Using only 19mL of water and with minimum sample manipulation, the method allowed for the determination of 53 compounds exhibiting good linearity (R2>0.99), recoveries between 84 and 118% and relative standard deviation (RSD) values <20% for intra-day and inter-day precision. In addition, the method provides quantification limits (LOQs) between 0.1-50ngL-1, lower than the Environmental Quality Standards (EQS) fixed by Directive 2013/39/EC. Finally, the method was successfully applied to determine target contaminants in Almería surface water compartments, detecting dioxin-like PCBs, BDEs and some pesticides.

[Assessment of adherence to antibiotic treatment in Primary Care by determining levels of the drug using a liquid chromatography technique]. / Valoración de la adherencia al tratamiento antibiótico en Atención Primaria mediante la determinación de niveles del fármaco utilizando una técnica de cromatografía líquida.

OBJECTIVE: The lack of adherence to antibiotic treatments is a matter of special interest, which has important clinical implications, as it is associated with therapeutic failure and increased bacterial resistance causing a high sani-tary cost. The objective of our study was to assess the degree of adherence to prescribed antibiotic treatment in outpatients through the detection of these in blood, urine or sputum. METHODS: Concentrations of antibiotics prescribed in 39 patients (34 with clinical suspicion of urinary tract infection and 5 with clinical suspicion of low respiratory tract infection) treated in Primary Care consultations of the Sanitary District of Almería (Spain) were determined by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. RESULTS: A 48.7% of the patients did not comply correctly with the indicated treatment due to the complete or partial omission in taking the prescribed antibiotics. This lack of adherence was independent of the age and sex of the patients, the number of daily doses of the antibiotic, and whether or not they were receiving another medication. CONCLUSIONS: Precise analytical techniques such as liquid chromatography can be useful to detect inadequate or incomplete treatments as well as the degree of adherence of outpatients. Thus, adequate measures could be established that affect the control of therapeutic compliance.

Rapid and sensitive on-line solid phase extraction-ultra high performance liquid chromatography-electrospray-tandem mass spectrometry analysis of pesticides in surface waters.

A simple, fast and sensitive method has been developed for the determination of 37 LC-amenable pesticides in surface water samples. On-line solid phase extraction (SPE) coupled to ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS. was employed for pre-concentration and analysis of all compounds in 16min. SPE parameters were evaluated in order to increase sample throughput and detectability. Thus, injected sample volume, sample loading flow, carryover effects and reusability of the cartridges employed were studied, observing that 70 extractions can be performed with the same cartridge. Validation parameters were performed and good linearity (R(2)>0.99 in all cases) and precision (interday relative standard deviation values were lower than 14%) were obtained. Limits of detection (LOD) and limits of quantification (LOQ) were lower than 6.0 and 18.0ngL(-1) applying an injection sample volume of 1.5mL, respectively, with exception of thifensulfuron methyl, whose limits were 10.0 and 33.0ngL(-1), respectively. On-line SPE recoveries were evaluated for three concentration levels (0.01, 0.03, 0.10 and 0.20µgL(-1)) and acceptable values were found. The on-line SPE method was also compared with off-line SPE. Matrix effects were observed for majority of compounds and standard addition method was selected for analysis of real water samples. Finally, surface water samples were analyzed and, in all cases, the pesticide concentrations were below than the allowable limit in water for human consumption.

Gallbladder selection for histopathological analysis based on a simple method: a prospective comparative study.

INTRODUCTION: After a cholecystectomy, the current and traditional practice is to send each resected gallbladder to the pathologist for analysis. Some reports have suggested the possibility of selecting only those gallbladders that need to be analysed. The purpose of this study was to show a simple method for selecting which gallbladders should be sent to the pathologist. METHODS: A prospective comparative study was carried out. Two 'tests' were performed in 150 patients to detect or rule out gallbladder cancer. The first test included the patient's variables and a macroscopic gallbladder analysis performed by the surgeon (MGAS). The second test was the analysis performed by the pathologist. The results were compared. RESULTS: Of the 150 patients, 132 were women and 18 men; 130 were under 60 years old. One patient had inflammatory bowel disease, seven had changes on ultrasonography and in four cases intra-operative disturbances were observed. During the MGAS, disturbances were found in 30 patients. Eighty-one cases (54%) had at least one or more risk factors for gallbladder cancer.

Food contaminant analysis at high resolution mass spectrometry: application for the determination of veterinary drugs in milk.

Veterinary drugs (VDs) can remain in milk as a consequence of their use in livestock. In order to control the levels of VD residues in milk, screening methodologies can be applied for a rapid discrimination among negative and non-negative samples. In a second stage, non-negative samples are classified as negative or positive samples by using a confirmation method. Pre-target screening methods in low resolution MS (LRMS) are normally applied, but the number of analytes is limited, whereas the information obtained by full scan acquisition in high resolution mass spectrometry (HRMS) is improved. Here, three screening methods (running time<4 min) based on Orbitrap, quadrupole-time of flight (QqTOF) and triple quadrupole (QqQ) have been compared, using in all cases ultra-high performance liquid chromatography (UHPLC). For HRMS, the identification of the VDs was based on retention time (RT) and accurate mass measurements. Confirmation was based on the monitoring of fragments generated without precursor selection. The performance characteristics of the screening method provided reliable information regarding the presence or absence of the compounds below an established value, including uncertainty region and cut-off values. Better results in terms of cut-off values (≤ 5.0 µg kg(-1), except for spiramycin with a cut-off of 13.4 µg kg(-1) for milk samples and 43.1 µg kg(-1) for powdered milk based, emamectin with a cut-off of 42.2 µg kg(-1) for milk samples and doxycycline, with a cut-off value of 15.8 µg kg(-1) in powdered milk-based infant formulae) and uncertainty region were obtained using the Orbitrap-based screening method, which was submitted to further validation and used to analyze different real milk samples. The proposed method can be used in routine analysis, providing reliable results.

Simultaneous analysis of chlorophenols, alkylphenols, nitrophenols and cresols in wastewater effluents, using solid phase extraction and further determination by gas chromatography-tandem mass spectrometry.

An analytical methodology has been developed for the simultaneous extraction of 13 phenolic compounds, including chlorophenols (CPs), nitrophenols (NTPs), cresols and alkylphenols (APs) in different types of wastewater (WW) effluents. A solid-phase extraction (SPE) method has been optimized prior to the determination by gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS). Due to the complexity of the matrix, a comparison study of matrix-matched-calibration (MMC) and standard addition calibration (SAC) was carried out for quantification purposes. The optimized procedure was validated using the SAC approach since it provided the most adequate quantification results (in terms of recovery and precision values). Recoveries were in the range 60-135% (0.5 µg L(-1)), 70-115% (1 µg L(-1)), and 78-120% (5 µg L(-1)), with precision values (expressed as relative standard deviation, RSD) ≤ 30% (except for 2-nitrophenol) involving intra-day and inter-day precision studies. Limits of detection (LODs) and quantification (LOQs) were also evaluated, and LOQs ranged from 0.03 µg L(-1) to 2.5 µg L(-1). The proposed method was applied to the analysis of 8 real WW effluent samples, finding some phenolic compounds (e.g. 2-chlorophenol, 2,4,6-trichlorophenol and 4-tert-octylphenol) at concentrations higher than the established LOQs.

Simultaneous determination of pesticides, biopesticides and mycotoxins in organic products applying a quick, easy, cheap, effective, rugged and safe extraction procedure and ultra-high performance liquid chromatography-tandem mass spectrometry.

A method for the simultaneous determination of pesticides, biopesticides and mycotoxins from organic products was developed. Extraction of more than 90 compounds was evaluated and performed by using a modified QuEChERS-based (acronym of Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation procedure. The method was based on a single extraction with acidified acetonitrile, followed by partitioning with salts, avoiding any clean-up step prior the determination by ultra-high performance liquid chromatography/tandem quadrupole mass spectrometry (UHPLC-MS/MS). Validation studies were carried out in wheat, cucumber and red wine as representative matrixes. Recoveries of the spiked samples were in the range between 70 and 120% (with intra-day precision, expressed as relative standard deviation, lower than 20%) for most of the analysed compounds, except picloram and quinmerac. Inter-day precision, expressed as relative standard deviation, was lower than 24%. Limits of quantification were lower than 10µg kg⁻¹ and the developed method was successfully applied to the analysis of organic food products, detecting analytes belonging to the three types of compounds.

Comparison of the efficiency of different extraction methods for the simultaneous determination of mycotoxins and pesticides in milk samples by ultra high-performance liquid chromatography-tandem mass spectrometry.

A rapid multi-analyte method has been developed for the simultaneous determination of pesticides and mycotoxins in milk by ultra high-performance liquid chromatography coupled to triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS). A variety of methodologies has been evaluated, including solid-phase extraction (SPE), "dilute-and-shoot" (liquid-liquid extraction-based procedures), and QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based methods. The optimization and development process was carried out considering that the maximum residue level for aflatoxin M1 (AFM1) in milk in the European Union (EU) is set at 0.05 µg kg(-1), which is the lowest tolerance in the target compounds. The selected method consisted of an extraction by SPE using C18 as sorbent and methanol as elution solvent. The final determination was performed by UHPLC-QqQ-MS/MS. Matrix-matched standard calibration was used for quantification, obtaining recoveries in the range 60-120% with relative standard deviations <25%, at three spiking levels: 0.5, 10, and 50 µg kg(-1) (ten times lower for AFM1). Limits of quantification ranged from 0.20 to 0.67 µg kg(-1), which were always below or equal to the established tolerance levels by the EU. Finally, the selected method was applied to different types of milk.

Comparison of solid phase microextraction and hollow fiber liquid phase microextraction for the determination of pesticides in aqueous samples by gas chromatography triple quadrupole tandem mass spectrometry.

This work compares two miniaturised sample preparation methods, solid phase microextraction (SPME) and hollow fiber liquid phase microextraction (HF-LPME), in combination with gas chromatography coupled to tandem mass spectrometry with a triple quadrupole analyzer for the determination of 77 pesticides in drinking water. In the case of SPME, extraction temperature and time were optimized by experimental design, although other parameters, as desorption time, pH, and ionic strength, were also evaluated. The extraction and desorption solvents [octanol/dihexyl ether (75:25, v/v) and cyclohexane, respectively], as well as the extraction and desorption time, ionic strength, and pH, were studied for the HF-LPME procedure. Under the optimal conditions, recoveries (70.2-113.5% for SPME and 70.0-119.5% for HF-LPME), intra-day precision (2.1-19.4% for SPME and 4.3-22.5% for HF-LPME), inter-day precision (5.2-21.5% for SPME and 8.4-27.3% for HF-LPME), and limits of detection, between 0.1 and 28.8 ng/L for SPME and 0.2 and 47.1 ng/L for HF-LPME and overall uncertainty (9.6-25.2% for SPME and 13.3-27.5% for HF-LPME) were established for both extraction procedures. Finally, the proposed methods were successfully applied to the analysis of 41 drinking water samples, and similar results were obtained with both extraction approaches.

Determination of ochratoxin A and T-2 toxin in alcoholic beverages by hollow fiber liquid phase microextraction and ultra high-pressure liquid chromatography coupled to tandem mass spectrometry.

A new method for the determination of ochratoxin A and T-2 toxin in alcoholic beverages (wine and beer) by hollow fiber liquid microextraction was optimized. The extraction step was followed by ultra high-pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The extraction procedure was based on the extraction of mycotoxins from the sample to the organic solvent (1-octanol) immobilized in the fiber, and afterwards, they were desorbed in a mixture of acetonitrile/water (80:20, v/v) at pH 7 prior to chromatographic determination. Different variables affecting the extraction process such as organic solvent, salt content, extraction time and desorption solution were studied. The developed method was validated in wine and beer, using white wine and alcoholic beer as representative matrices for both types of samples. Relative recoveries higher than 70% were obtained for the selected mycotoxins. Good linearity (R(2)>0.993) was obtained and quantification limits (0.02-0.09 microg L(-1)) below European regulatory levels were achieved. Repeatability, expressed as relative standard deviation, was always lower than 12%, whereas interday precision was lower than 21%. The proposed method was applied to the analysis of several types of wines and beers and ochratoxin A was detected in a rosé wine at 1.1 microg L(-1).

Determination of pesticide transformation products: a review of extraction and detection methods.

Pesticides are widely applied and they can produce a variety of transformation products (TPs), through different pathways and mechanisms. Nowadays there is a growing interest related to the determination of pesticide TPs in several matrices (environmental, food and biological samples), due to these compounds can be more toxic and persistent than parent compounds, and some of them can be used as markers of exposure to different pesticides. Although solid-phase extraction (SPE) is mainly used for the extraction of TPs, alternative techniques such as solid-phase microextraction (SPME) and liquid-phase extraction (LPE) can be used. These TPs are mainly determined by liquid chromatography (LC) due to the recent developments in this technique, especially when it is coupled to mass spectrometry (MS) detectors, allowing the determination of known and/or unknown TPs. Furthermore, MS is a very valuable tool for the structural elucidation of unknown TPs. This review discusses all phases of analytical procedure, including sample treatment and analysis, indicating the main problems related to the extraction of TPs from several matrices due to their high polarity, as well as the different alternatives found for the simultaneous determination of parent compounds and TPs, using chromatographic techniques coupled to MS detection.

Compensation for matrix effects in gas chromatography-tandem mass spectrometry using a single point standard addition.

One of the major problems in quantitative analysis of pesticide residues in food samples by gas chromatography-tandem mass spectrometry (GC-MS/MS) is the enhancement or the suppression, of the target analyte signals in matrix extracts. Potentially positive samples, which had previously been identified by a rapid screening method, were quantified using standard addition to compensate matrix effects. As example we performed a systematic study on the application of the standard addition calibration (SAC) method for the determination of 12 pesticides (acephate, bromopropylate, chlorpyrifos, cypermethrin, diazinon, etrimfos, heptenophos, iprodione, methamidophos, procymidone, tetradifon, and triadimefon) in two matrices (cucumber and orange) in the range of initial concentrations of 10-200 microg kg(-1). The influence of some factors, such as the minimum number of standard additions used (single, two, three or four points calibration), as well as the known amount of analyte added to the sample, is evaluated in order to obtain reliable results. Accurate quantification is achieved when a single point SAC at 200 microg kg(-1) was used, obtaining for all the cases recoveries between 70 and 120%. The proposed analytical approach only needs two injections per sample (blank and spiked extracted sample) to determine the final concentration of pesticide in positive samples.

Comparison of ultrasonic and pressurized liquid extraction for the analysis of polycyclic aromatic compounds in soil samples by gas chromatography coupled to tandem mass spectrometry.

A pressurized liquid extraction (PLE) method has been optimized for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil samples and it was compared with ultrasonic extraction. The extraction step was followed by gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS/MS) analysis. Parameters such as type of solvent, extraction time, extraction temperature and number of extractions were optimized. There were no significant differences among the two extraction methods although better extraction efficiencies were obtained when PLE was used, minimizing extraction time and solvent consumption. PLE procedure was validated, obtaining limits of detection (LODs) ranging from 0.02 to 0.75 microg kg(-1) and limits of quantification (LOQs) ranging from 0.07 to 2.50 microg kg(-1) for the selected PAHs. Recoveries were in the range of 59-110%, except for naphthalene, which was the most volatile PAH. Finally, the method was applied to real soil samples from Southeast of Spain. PAHs concentrations were low, and phenanthrene, pyrene, fluorene, benzo[a]pyrene and chrysene were the most frequently detected analytes in the samples.

Application of hollow fibre liquid phase microextraction for the multiresidue determination of pesticides in alcoholic beverages by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry.

An alternative method has been developed to determine more than 50 pesticides in alcoholic beverages using hollow fibre liquid phase microextraction (HF-LPME) followed by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), without any further clean-up step. Pesticides were extracted from the sample to the organic solvent immobilized in the fibre and they were desorbed in methanol prior to chromatographic analysis. Experimental parameters related to microextraction such as type of organic solvent, extraction time and agitation rate have been optimized. The extraction method has been validated for several types of alcoholic beverages such as wine and beer, and no matrix effect was observed. The technique requires minimal sample handling and solvent consumption. Using optimum conditions, low detection limits (0.01-5.61microgL(-1)) and good linearity (R(2)>0.95) were obtained. Repeatability and interday precision ranged from 3.0 to 16.8% and from 5.9 to 21.2%, respectively. Finally the optimized method was applied to real samples and carbaryl, triadimenol, spyroxamine, epoxiconazole, triflumizol and fenazaquin were detected in some of the analyzed samples. The obtained results indicated that the new method can be successfully applied for extraction and determination of pesticides in alcoholic beverages, increasing sample throughput.

Multiresidue method for fast determination of pesticides in fruit juices by ultra performance liquid chromatography coupled to tandem mass spectrometry.

A new analytical method for the simultaneous determination of 90 pesticides in fruit juices by ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) has been developed and validated. Extraction was performed with acetonitrile, applying QuEChERS methodology, and the extracts were analyzed without any further clean-up step, providing better results than solid phase extraction (SPE) procedure. Before chromatographic step, extracts were diluted with water (1:1) in order to obtain good peak shapes. Several chromatographic conditions were evaluated in order to achieve a fast separation in Multiple Reaction Monitoring (MRM) mode, obtaining a run time of only 11 min. Matrix effect was studied for different types of fruit juices (peach, orange, pineapple, apple and multifruit), indicating that multifruit juice can be selected as representative matrix for routine analysis of these food commodities. Pesticides were quantified using matrix-matched calibration with recoveries between 70.4 and 108.5% and relative standard deviation lower than 20%. Limits of quantification were lower than 5 microg L(-1) in all the cases. The developed procedure was applied to commercial fruit juices, detecting carbendazim, cyprodinil and thiabendazol in a few samples.

High-throughput determination of pesticide residues in food commodities by use of ultra-performance liquid chromatography-tandem mass spectrometry.

A rapid, simple, and sensitive multiresidue method for analysis of 53 pesticides in fruit and vegetables by ultra-performance liquid chromatography (UPLC) coupled to triple-quadrupole tandem mass spectrometry (MS-MS) has been developed and validated. Prior to analysis, analytes were extracted by use of buffered QuEChERS (quick, easy, cheap, effective, rugged, safe) methodology without further cleanup for non fatty matrices. Chromatographic conditions were optimised in order to achieve a fast separation in multiple reaction monitoring (MRM) mode. Indeed, more than 50 pesticides can be separated in less then 10 min. Four common representative matrices (cucumber, orange, strawberry, and olive) were selected to investigate the effect of different matrices on recovery and precision. Mean recoveries ranged from 70 to 109% with relative standard deviations lower than 20% for all the pesticides assayed in the four selected matrices. The method has been applied to the analysis of 200 vegetable samples, and imidacloprid was the pesticide most frequently found, with concentrations ranging from 0.01 to 1.00 mg kg(-1). This methodology combines the advantages of both QuEChERS and UPLC-MS-MS producing a very rapid, sensitive, and reliable procedure which can be applied in routine analytical laboratories.

Evaluation of the equations to estimate the glomerular filtration rate in kidney transplant recipients.

This study assessed the performance of three methods for estimating glomerular filtration rate (GFR) in kidney transplant patients: the Cockcroft-Gault formula, the modification of diet in renal disease (MDRD) method, and the four-variable modification of diet in renal disease (four-variable MDRD), both as an overall estimate and as related to clinical disease stage. We analyzed data from 136 renal transplant patients including 84 men in an overall age range of 28 to 76 years. Patients were categorized into three groups according to GFR as determined by the arithmetical mean of the last four creatinine clearance determinations after outlying values had been excluded: group 1, estimated GFR of <30 mL/min (n = 26); group 2, estimated GFR of 30 to 60 mL/min (n = 63);, and group 3, estimated GFR >60 mL/min (n = 33). Fourteen patients were excluded from the analysis because of a high variability between their creatinine clearance determinations. Estimated GFRs using the Cockroft-Gault, MDRD, and four-variable MDRD formulae were compared with GFRs as measured by creatinine clearance. Statistically significant correlations were observed for all three formulae for the overall series and for individual clinical groups. Hence, we concluded that all equations had a similar capacity to predict the GFR. In addition, because of the clear, significant correlation between the MDRD and the four-variable MDRD (r = .992; P = .0001), we believe that the four-variable MDRD can substitute for the MDRD for clinical purposes.

Simultaneous determination of selected veterinary antibiotics in gilthead seabream (Sparus Aurata) by liquid chromatography-mass spectrometry.

A method was optimised and validated for simultaneous monitoring of several drugs of different classes of antibiotics such as quinolones (oxilinic acid and flumequine), tetracyclines (oxytetracycline), sulfonamides (sulfadiazine) and trimethoprim in fish muscle and skin. The method is based on solid-liquid extraction without further sample clean up followed by liquid chromatography-mass spectrometry (LC-MS) determination with electrospray ion source (ESI) in positive mode. The limits of quantification (LOQs) were lower than 20 microg/kg for all compounds and repeatability, expressed as relative standard deviations (RSD), were lower than 15%. Therefore, the LC-MS method was successfully applied for the quantitative determination of antibiotics in gilthead sea bream muscle and skin and oxytetracycline in medicated fishes.