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Abstract: A high performance liquid chromatography (HPLC) method has been developed for the simultaneous determination of four fluoroquinolones. The studied compounds have been enoxacin (ENO), norfloxacin (NOR), ofloxacin (OFLO) and enrofloxacin (ENRO). An isocratic elution method, using a mixture of tetrahydrofuran (8%) and phosphate buffer (pH 3.00, 30.0mM, 92%) as mobile phase, has been developed. Fluorimetric detection, exciting at 277nm, and multiemission scan (407nm for ENO, 444nm for both NOR and ENRO and 490nm for OFLO) has been used. Detection limits of 500, 14.7, 25.2 and 15.0ngmL−1 for ENO, NOR, OFLO and ENRO, respectively, have been obtained. The proposed method has been satisfactorily applied to analyze NOR, OFLO and ENRO in human urine and serum samples. [Copyright &y& Elsevier]

Abstract: A widely employed compound for honey treatment, sulfathiazole (ST), was determined in commercial honey samples, employing a combination of photochemically induced fluorescence excitation–emission matrices (EEMs) and chemometric processing of the recorded second-order data. Parallel Factor Analysis (PARAFAC) and Self-Weighted Alternating Trilinear Decomposition (SWATLD) methods were used for calibration. An appropriately designed calibration with a set of standards composed of 18 samples, coupled to the use of the second-order advantage offered by the applied chemometric techniques, allowed quantitation of sulfathiazole in spiked commercial honey samples. No previous separation or sample pretreatment steps were required. The results were compared with other calibration methods such as N-PLS and PLS-1 that produced good results on synthetic samples but not on the investigated commercial honey samples. [Copyright &y& Elsevier]

A simple, rapid and efficient methodology was developed for the extraction and determination of heterocyclic aromatic amines (HAAs) in cigarette and forest fire ash samples based on a novel Ultrasound-Assisted Dispersive Solid-liquid Microextraction (UA-DSLME) coupled to polyurethane foam (PUF) mini-column as a clean-up strategy and on-line determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The optimal working conditions were found by (i) application of two-level full factorial designs and (ii) implementation of a response surface methodology based on the second-order design as central composite designs. Under optimal experimental conditions, good linearity was obtained for concentrations ranging from 8.3 to 500 ng g -1 , with correlation coefficients (r 2 ) varying from 0.995 to 0.999 for all HAAs investigated. The limits of detection and quantification resulted to be between 2.1 and 10.7 ng g -1 and 8.3-16.9 ng g -1 , respectively. The recoveries from 92.2 to 100.6% were reached and the relative standard deviations (RSDs) were lower than 9.2%. The developed method was successfully applied to the determination of HAAs in ashes generated by cigarette and forest fire combustion., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Monitoring of amphetamine-type stimulant (ATS) confronts clinical labs with a high number of samples involving a variety of biological matrices. Liquid chromatography-tandem mass spectrometry (LC-MS/MS), routinely used for confirmation of ATS abuse, requires of laborious and matrix-dependent sample treatment methods, this increasing analysis time and cost. In this work, a universal and single-step sample treatment, based on supramolecular solvents (SUPRAS), was proposed for simplifying ATS confirmation in seven biological matrices. The SUPRAS was synthesized in situ in the sample (900 µL of basified oral fluid, urine, serum, sweat or breast milk or 50 mg of digested hair or fingernails) by the addition of hexanol (200 µL) and tetrahydrofuran (900 µL). The mixture was vortex-shaken and centrifuged and the SUPRAS extract was subsequently analyzed by positive ion mode electrospray LC-MS/MS. The method was fully validated for amphetamine (AMP), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), N-ethyl-3,4-methylenedioxyamphetamine (MDEA) and N-methyl-3,4-methylenedioxyamphetamine (MDMA). Maximum ion suppression or enhancement was 9% and 7%, respectively, and extraction recoveries (87-111%) and within- (0.1-6.7%) and between-day (0.3-9.7%) CVs were all within required values. The lower limits of quantification (LLOQ) for biological fluids (5 ng/mL), and hair and fingernails (100 ng/g) were all well below the cut-offs established by worldwide organizations. Confirmation of MDA was carried out in five urine samples that tested positive for ATS by immunoassay. The SUPRAS-LC-MS/MS methodology succeeded in developing a hitherto unexplored and universal tool for quantifying ATS in a comprehensive pool of biological matrices of interest in forensic and clinical samples., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A study was conducted to evaluate the homogeneity of the distribution of metals and metalloids deposited on glass fiber filters collected using a high-volume sampler equipped with a PM-10 sampling head. The airborne particulate matter (APM)-loaded glass fiber filters (with an active surface of about 500cm(2)) were weighed and then each filter was cut in five small discs of 6.5cm of diameter. Each disk was mineralized by acid-assisted microwave (MW) digestion using a mixture of nitric, perchloric and hydrofluoric acids. Analysis was performed by axial view inductively coupled plasma optical emission spectrometry (ICP OES) and the elements considered were: Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Ti and V. The validation of the procedure was performed by the analysis of the standard reference material NIST 1648, urban particulate matter. As a way of comparing the possible variability in trace elements distribution in a particular filter, the mean concentration for each element over the five positions (discs) was calculated and each element concentration was normalized to this mean value. Scatter plots of the normalized concentrations were examined for all elements and all sub-samples. We considered that an element was homogeneously distributed if its normalized concentrations in the 45 sub-samples were within +/-15% of the mean value ranging between 0.85 and 1.15. The study demonstrated that the 12 elements tested showed different distribution pattern. Aluminium, Cu and V showed the most homogeneous pattern while Cd and Ni exhibited the largest departures from the mean value in 13 out of the 45 discs analyzed. No preferential deposition was noticed in any sub-sample.

Ternary mixtures of fluoroquinolones, with a 7-piperazinyl substituted group have been simultaneously determined in human urine samples by application of a multivariate calibration partial least squares (PLS) model. The calibration set was designed with 15 urine samples containing different concentrations of the three fluoroquinolones and 16 blank urine samples. The concentration range for the fluoroquinolones were up to 25ngml(-1) for norfloxacin (NOR), 80ngml(-1) for ofloxacin (OFLO) and 300ngml(-1) for enoxacin (ENO). The method is based on the native fluorescence emission of these compounds in sodium dodecyl sulfate (SDS) medium, at pH 4.0, when exciting at 277nm. A selection of the emission wavelength range used for the analysis was made for each component. Intraday and interday precision values were determined. Figures of merit as selectivity, sensitivity, limit of detection (LOD) and analytical sensitivity were also calculated. Using the standard addition methodology, five urine samples from five different persons, fortified with three concentration levels of the fluoroquinolones, were analyzed. The limits of detection in urine were 10.0, 0.5 and 0.8ngml(-1) for ENO, NOR and OFLO, respectively.