1,720,997 research outputs found
Determinazione simultanea di erbicidi e contaminanti emergenti in acque superficiali, potabili e minerali mediante HPLC tandem MS
No full textUn ampio range di sostanze chimiche, note e/o di nuova generazione, è prodotto ogni anno per gli scopi più vari e riversato nell’ambiente con conseguenze spesso non prevedibili. Ne sono un significativo esempio i fitofarmaci ed i contaminanti emergenti che, per la loro comune possibilità di raggiungere l’ambiente acquatico e le risorse idropotabili attraverso numerose vie, sono oggetto di studio continuo da parte della comunità scientifica internazionale.
Mentre i fitofarmaci costituiscono una problematica ambientale nota fin dagli anni ́60, regolata da leggi e normative, i contaminanti emergenti, pur avendo origini anche più remote, erano fuori da eventuali studi di monitoraggio ambientale fino a qualche decennio fa. Ciò spiega la mancanza di normative che impongano limiti alla loro presenza nell’ambiente e che le metodologie proposte per la valutazione del rischio ambientale ad esse associato siano ancora in fase di sviluppo.
Il presente lavoro è stato rivolto alla determinazione di alcuni tra i chemicals più utilizzati nel nostro paese e rilasciati nell’ambiente a livello di tracce, con lo scopo di ottenere un quadro, seppur ristretto, della “contaminazione multi-residuale” alla quale siamo esposti. Considerato lo stato di degradazione in cui si trovano le acque superficiali italiane, nonché quelle di falda e ad uso umano in generale, lo studio ha cercato di essere più ampio possibile andando ad esaminare non solo le acque superficiali, ma anche quelle potabili e minerali, comparti particolarmente sensibili, in quanto facilmente raggiungibili dagli xenobiotici riversati nell’ambiente.
E’ stata quindi sviluppata e validata una metodica analitica basata sulla cromatografia liquida accoppiata alla spettrometria di massa tandem (LC-MS-MS), per la determinazione in matrice acquosa di alcuni erbicidi (MCPA, 2,4 D, dicamba, bentazone) e di diversi farmaci ad uso umano ed animale (ibuprofene, diclofenac, nimesulide, indometacina, chetoprofene, naprossene, acido tolfenamico, acido meclofenamico, acido clofibrico, idroclorotiazide); queste sostanze, pur avendo caratteristiche chimico-fisiche diverse sono state scelte perchè particolarmente rappresentative della contaminazione antropogenica. Dopo la fase di estrazione degli analiti, su cartucce OASIS HLB, la separazione cromatografica era realizzata con colonna C18 narrow-bore (150 mm x 2.1 mm i.d.; 5μm) usando dibutilammina come agente di coppia ionica. L’identificazione e l’analisi quantitativa erano condotte rivelando gli analiti mediante sorgente electrospray in ionizzazione negativa, selezionando per ciascun analita due transizioni SRM (Selected-Reaction-Monitoring).
Il metodo sviluppato è stato poi applicato all’analisi di diversi campioni di acque superficiali, minerali e potabili; i risultati ottenuti mostrano un quadro di contaminazione abbastanza preoccupante soprattutto per lo stato di alcuni corsi d’acqua risultati positivi sia ai farmaci che agli erbicidi
MS techniques for analyzing phenols, their metabolites and transformation products of environmental interest
No full textThis overview covers, in particular, chlorinated phenols, alkylphenols and steroidal estrogens that have caused great concern because of their adverse effects, diffusion and resistance to (bio)degradation. We first describe strategies for combining liquid chromatography with mass spectrometry (LC-MS) to recognize metabolites, providing evidence for the advantages and the limitations of the available techniques and predicting future trends in this field. We then review the present state of the art in the analysis of the above compounds. We pay particular attention to those LC-MS methods involving the analysis of target phenolic compounds and identification of their unknown products in the various environmental compartments. (C) 2008 Elsevier Ltd. All rights reserved
LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY FOR PERFORMING CONFIRMATORY ANALYSIS OF VETERINARY DRUGS IN ANIMAL-FOOD PRODUCTS
No full textThis review focuses on recent developments and trends in liquid chromatography coupled to mass spectrometry, with a particular emphasis on tandem mass spectrometry and the new criteria established by the European Union for performing confirmatory analysis of veterinary drugs in animal-food products. The combination of liquid chromatography and tandem mass spectrometry allows unequivocal identification of traces of antibiotics and antibacterial agents in complex biological matrices, such as honey, eggs, milk and meat. The sensitivity of the coupling is particularly useful for confirming the presence of banned substances that require limits of detection as low as possible. (c) 2005 Elsevier Ltd. All rights reserved
DETERMINATION OF ARYLPHENOXYPROPIONIC HERBICIDES IN WATER BY LIQUID CHROMATOGRAPHY-ELECTROSPRAY MASS SPECTROMETRY
No full textA very sensitive and specific analytical procedure for determining arylphenoxypropionic herbicides in aqueous environmental samples, using pneumatically assisted electrospray (ESI) liquid chromatography-mass spectrometry (LC-MS) is presented. Arylphenoxypropionic acids are a new class of herbicides used for the selective removal of most grass species from any nongrass crop. These herbicides are commercialized as herbicide esters. It has been shown that the ester derivatives undergo fast hydrolysis in the presence of vegetable tissues and soil bacteria, yielding the corresponding free acid. The analytical procedure involves passing 1 l of surface or ground water and 2 l of drinking-water samples, through a 0.5-g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6-mn I.D. reversed-phase LC C-18, operating with a 1 ml/min mobile phase flow-rate, was used for chromatographing the analytes. A flow of 200 mu l/min of the column effluent was diverted to the ESI source. The ESI source was operated in positive-ion mode for neutral pesticides and in negative-ion mode for acid pesticides. For ion-signal optimization, the effect of the concentration of the acid in the mobile phase on the response of the ESI-MS detector was investigated. By evaluating the specificity and sensitivity of the method, the effects of varying the orifice plate voltage on the production of the diagnostic fragment and the response of the MS detector were also investigated. For the analyte considered, the response of the mass detector was linearly related to the amount of the analyte injected between 1 and 200 ng. In all cases, recoveries of the analytes were better than 91%. The limit of detection (signal-to-noise ratio=3) of the method for the pesticides considered in drinking water samples was estimated to be about 3-10 ng/l. (C) 1998 Elsevier Science B.V. All rights reserved
DETERMINATION OF NON STEROIDAL ANTI-INFLAMMATORY DRUGS IN SURFACE WATER AND WASTEWATER BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY
No full textAn analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS-MS) has been developed for the determination of pharmaceutical compounds in water samples. The drugs investigated were the analgesics: Ibuprofen, Fenoprofen, Ketoprofen, Naproxen, and Diclofenac and the decomposition product of acetylsalicylic acid: salicylic acid. The selected compounds are acidic, very polar and all are analgesic compounds that can be purchased without medical prescription. Sample enrichment of water samples was achieved by solid-phase extraction procedure (SPE), using Waters Oasis HLB cartridges followed by LC-MS-MS. A narrow-bore 2.1 min i.d., reversed phase LC C-18 column was used to chromatograph analytes. Average recoveries from 1 L samples varied 75-95% and the detection limits are <1 ng L-1. The method developed was applied to real samples from wastewater and surface waters of Lazio country (Italy)
Study of the Vitamin K Cyclic Metabolism in absence and presence of coumarin anticoagulants by Liquid Chromatography- Linear Ion Trap Mass Spectrometry
No full textIn mammalians the only known function of vitamin K is that of γ-glutamylcarboxylase cofactor, enzyme catalyzing the posttranslational carboxylation of the so-called vitamin K-depending proteins. Well-known for the activation of the coagulation proteins, vitamin K has also been shown to be
required by extra-hepatic proteins involved in bone metabolism, vascular calcification, and apoptosis. This vitamin is characterized by a cyclic metabolism: it is its stable quinonic form to be absorbed and transported in blood, but it is the hydroquinone one to act as enzymatic cofactor and to be transformed into vitamin K 2,3-epoxide. The latter is then recycled to quinone and hydroquinone in successive reactions catalyzed by vitamin K reductases, dithiol-depending enzymes
inhibited by coumarin drugs. A second NAD(P)H-dependent quinone reductase is relatively insensitive to these anticoagulants and operates at high concentrations of
vitamin K. Probably because of its efficient recycle system, very low levels of vitamin K circulate in plasma. Moreover, its Recommended Daily Allowance has currently been set at 1 μg/kg/day; this value is surely suitable for its hepatic function, but an extra demand might be required for guaranteeing the bone and vessel health, especially in subjects under anticoagulant therapy. For these reasons, an accurate determination of the vitamin K and its metabolites is a real analytical challenge. This work was just addressed to overcome the above-mentioned difficulties making use of an advanced analytical technique such as liquid chromatography-linear ion trap mass spectrometry. After its development and
validation, the method was applied for refining the status of phylloquinone (vitamin K1) and for defining that of vitamin K1 2,3-epoxide in a significant cohort of healthy subjects and of patients under anticoagulant therapy. An accumulation of
both forms was verified in individuals taking long-term coumarin drugs
Ottimizzazione del sistema HPLC/MS per la determinazione di pesticidi in matrici ambientali
No full textQUADRUPOLE TIME-OF-FLIGHT VERSUS TRIPLE-QUADRUPOLE MASS SPECTROMETRY FOR THE DETERMINATION OF NON STEROIDAL ANTIINFLAMMATORY DRUGS IN SURFACE WATER BY LIQUID CHROMATOGRAPHY/TANDEM MASS SPECTROMETRY
No full textA triple-quadrupole instrument and a hybrid quadrupole/time-of-flight (TOF) mass spectrometer were compared for the determination of pharmaceutical compounds in water samples. The drugs investigated were the analgesics Ibuprofen, Fenoprofen, Ketoprofen, Naproxen, and Diclofenac. The recently introduced Q2-pulsing function, which enhances the transmission of fragment ions of a selected m/z window from the collision cell into the TOF analyzer, improved the sensitivity of product ion scans on the quadrupole/TOF instrument. The selectivity is much better on quadrupole/TOF systems than on triple quadrupoles because the high resolving power of the reflectron-TOF mass analyzer permits high-accuracy fragment ion selection. This minimizes interferences from environmental matrices and allows acquisition of full spectra for selected analytes with better signal-to-noise characteristics than comparable spectra obtained with a scanned quadrupole. The qualitative information obtained (mass accuracy, resolution and full-scan spectra) by hybrid quadrupole/TOF mass spectrometry allows a more certain identification of analytes in environmental matrices at trace levels. Sample enrichment of water samples was achieved by a solid-phase extraction procedure. Average recoveries for loading 1 L of samples varied from 88 to 110%, and the quantification limits were less than 1.2 ng/L for the triple-quadrupole instrument (in MRM mode) and less than 3 ng/L for the quadrupole/TOF instrument. Copyright (C) 2003 John Wiley Sons, Ltd
PRESSURIZED-LIQUID EXTRACTION FOR DETERMINATION OF IMIDAZOLINONE HERBICIDES IN SOIL
No full textA rapid and simple method has been developed for determination of imidazolinone (IMI) residues in soil. Extraction of the analytes from the soil matrix was performed with a pressurized-liquid-extraction apparatus built in this laboratory. Four different types of soil sample (clay, clay loam, sandy clay loam, and silty loam) were fortified with target compounds at levels of 10 and 50 ng g-1 by a procedure which can mimic weathered soils. The samples were then dried and packed in a 25 cm × 4.6 mm i. d. stainless steel column; this was placed inside a GC oven and extracted by passing an aqueous solution of KCl (0.1 M, 20 mL) through the column at 90°C. Quantification of the analytes in the final extract (50-μL injection) was performed by reversed-phase liquid chromatography-mass spectrometry with a TurbolonSpray interface. Recoveries of the analytes were greater than 83% and RSD less than 7%. The method detection limit was in the 1 - 2.5 ng g-1 range in analysis by time-scheduled selected-ion monitoring (SIM)
Solid-phase extraction followed by high-performance liquid chromatography-ionspray interface-mass spectrometry for monitoring of herbicides in environmental water
No full textIn this work we developed a sensitive and specific multiresidue method, based on reversed-phase liquid chromatography-mass spectrometry, with an ionspray interface (LC-ISI-MS), for determining 53 of most representative compounds of herbicides in water samples. The procedure used involved passing 0.5 l of surface water, 2 l of ground water and 4 l of drinking water samples, respectively, through a 0.5 g graphitized carbon black (GCB) extraction cartridge. Base-neutral and acid herbicides were differential eluted from GCB cartridge and follow analyzed by HPLC-ISI-MS apparatus. A conventional 4.6-mm-ID reversed-phase LC C-18 column, operating with a mobile phase flow-rate of 1 ml/min, was used to chromatograph the analytes. A flow of 100 mu l/min of the column effluent was diverted to the ISI source. The study demonstrates the sensitivity of the technique, with detection limit under 10 ng/l in drinking water samples. Performance data for the method such as recovery and precision are also reported. (C) 2000 Elsevier Science B.V. All rights reserved
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