Browsing by Author "Vieira, Duarte Nuno"
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- Determination of parathion in biological fluids by means of direct Solid Phase Microextraction.Publication . Gallardo, Eugenia; Barroso, Mário; Margalho, Cláudia; Cruz, Angelines; Vieira, Duarte Nuno; López-Rivadulla, ManuelA new and simple procedure for the determination of parathion in human whole blood and urine using direct immersion (DI) solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. This technique was developed using only 100 ìL of sample, and ethion was used as internal standard (IS). A 65-ìm Carbowax/divinylbenzene (CW/DVB) SPME fibre was selected for sampling, and the main parameters affecting the SPME process such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH effect were optimized to enhance the sensitivity of the method. This optimization was also performed to allow the qualitative determination of parathion’s main metabolite, paraoxon, in blood. The limits of detection and quantitation for parathion were 3 and 10 ng/mL for urine and 25 and 50 ng/mL for blood, respectively. For paraoxon, the limit of detection was 50 ng/mL in blood. The method showed linearity between the LOQ and 50 ìg/mL for both matrices, with correlation coefficients ranging from 0.9954 to 0.9999. Precision and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries were 35.1% for urine and 6.7% for blood. Other parameters such as dilution of sample and stability were also validated. Its simplicity and the fact that only 100 ìL of sample is required to accomplish the analysis make this method useful in forensic toxicology laboratories to determine this compound in intoxications, and it can be considered an alternative to other methods normally used for the determination of this compound in biological media.
- Development and validation of an analytical method for the simultaneous determination of cocaine and its main metabolite, benzoylecgonine, in human hair by gas chromatography/mass spectrometry.Publication . Gallardo, Eugenia; Dias, M.; Vieira, Duarte Nuno; Queiroz, João; López-Rivadulla, ManuelA new, simple and rapid procedure has been developed and validated for the determination of cocaine and its main metabolite, benzoylecgonine, in human hair samples. After extraction from within the hair matrix by a mixture of methanol/hydrochloric acid (2:1) at 65-C for 3 h, and sample cleanup by mixed-mode solid-phase extraction (SPE), the extracts were analyzed by gas chromatography/ mass spectrometry (GC/MS), after derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide with 5% chlorotrimethylsilane. Using a sample size of only 20mg of hair, limits of detection (LODs) and quantitation (LOQs) were, respectively, 20 and 50 pg/mg for cocaine, and 15 and 50 pg/mg for benzoylecgonine, achieving the cut-off values proposed by the Society of Hair Testing for the analysis of these compounds in hair. The method was found to be linear (weighing factor of 1/x) between the LOQ and 20 ng/mg for both compounds, with correlation coefficients ranging from 0.9974 to 0.9996 for cocaine; and from 0.9981 to 0.9994 for benzoylecgonine. Intra- and interday precision and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The sample cleanup step presented a mean absolute recovery greater than 90% for both compounds. The developed method may be useful in forensic toxicology laboratories for the analysis of cocaine and benzoylecgonine in hair samples, taking into account its speed (only 3 h are required for the extraction of the analytes from within the matrix, whereas 5 h or even overnight extractions have been reported) and the low limits achieved (using a single quadrupole mass spectrometer, which is available in most laboratories).
- Solid-phase extraction for gas chromatographic mass spectrometric determination of the veterinary drug xylazine in human blood.Publication . Gallardo, Eugenia; Barroso, Mário; Margalho, Cláudia; Devesa, N.; Pimentel, J.; Vieira, Duarte NunoThis paper presents a method for the determination of xylazine in whole blood using solid-phase extraction and gas chromatography–mass spectrometry. This technique required only 0.5 mL of sample, and protriptyline was used as internal standard (IS). Limits of detection and quantitation (LOQ) were 2 and 10 ng/mL, respectively. The method was found to be linear between the LOQ and 3.50 ìg/mL, with correlation coefficients higher than 0.9922. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The analyte was stable in the matrix for at least 18 h at room temperature and for at least three freeze/thaw cycles. Mean recovery, calculated at three concentration levels, was 87%. To the best of our knowledge, this is the first time that solid-phase extraction is used as sample preparation technique for the determination of this compound in biological media. Because of its simplicity and speed when compared to other extraction techniques, the herein described method can be successfully applied in the diagnosis of intoxications by xylazine.
- Synthetic cannabinoids in biological specimens: a review of current analytical methods and sample preparation techniquesPublication . Rosado, Tiago; Gonçalves, Joana; Luís, Ângelo; Malaca, Sara; Soares, Sofia; Vieira, Duarte Nuno; Barroso, Mário; Gallardo, EugeniaSynthetic cannabinoids are a new class of chemical drugs capable of modifying human behavior. These products do not contain cannabis, but produce similar effects after consumption. The fact that they are easily accessed, and are many times considered to be harmless, justifies their widespread use among young people. This fact, together with the difficulty in their detection by routine drug tests, makes it extremely important to develop new procedures able to detect and monitor their consumption. The aim of this work is to perform a critical review regarding the human biological samples that can be used for the determination of synthetic cannabinoids, paying special attention to analytical methods and sample preparation techniques. The reviewed articles deal with the determination of synthetic cannabinoids in the context of forensic and toxicological analysis.