We present the thickness measurement of multilayer samples by X-ray fluorescence (XRF) using calibration curves obtained from simulated spectra through Monte Carlo (MC) algorithm.  https://www.selleckchem.com/products/ipi-549.html  The XRF is a widespread technique for the analysis of single and multilayer films but the accuracy of quantitative analysis must be increased. Moreover, the use certified standards is not easy to implement due to the high variability of combination and/or concentration in layered samples. The results of this work were compared with fundamental parameter (FP) method and focussed ion beam scanning electron microscopy (FIB-SEM) analysis. The results show good quantitative values even without the use of any standard with known thickness. In addition to having built the calibration curves with a simple univariate approach, also multivariate data analysis was performed to consider multiple variables simultaneously. From the comparison of the obtained results, it can be inferred that the univariate analysis worked well in the case of single layer samples and in the determination of the upper layer in multilayer samples but only multivariate analysis, taking into account the matrix effect of each layer, provided maximum accuracy on each layer of multilayer samples.A novel multiplexed label-free electrochemical immunosensor was fabricated using graphene/methylene blue-chitosan/antibody and bovine serum albumin on indium tin oxide glass electrode for the simultaneous determination of three types of tumor markers including carcinoembryonic antigen (CEA), cancer antigens 153 (CA153), and cancer antigen 125 (CA125). Cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy were employed to monitor each fabrication step. Under the optimized experiment conditions, the immunosensor exhibited good reproducibility and selectivity with linear ranges of 0.10-1.00 pg mL-1 and 1.00-100.00 pg mL-1 for CEA, 0.10-2.50 mU mL-1 and 2.50-100.00 mU mL-1 for CA153, 0.10-2.50 mU mL-1 and 2.50-100.00 mU mL-1 for CA125, a detection limit of 0.04 pg mL-1 for CEA, 0.04 mU mL-1 for CA153, and 0.04 mU mL-1 for CA125. This electrochemical immunosensor was successfully applied to detect three tumor markers in blood serum samples with good recoveries. The reliability of the electrochemical immunosensor to detect three tumor markers in blood serum samples was in good agreement (P > 0.05) with that of the enzyme-linked fluorescent assay method.A simple, fast, sensitive and reliable method was developed for the simultaneous determination of 13 food contact materials (FCM) regulated substances and non-intentionally added substances (NIAS) migrating into official food simulants. The method has been optimized to quantify the monomers styrene and α-methyl styrene, selected polystyrene oligomers (dimers, trimers) and polyester urethane-based oligomers (PU) cyclic oligomers, as well as cyclic NIAS originating from food packaging such as 2,6-Di-tert-butylbenzoquinone and 7,9-Di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione. The method employs liquid-liquid extraction of aqueous ethanol food simulants with dichloromethane, and analysis with gas chromatography coupled to mass spectrometry (GC-MS) with a total analysis time of less than 16 min, with limits of detections ranging from 0.32 ng mL-1 (1,1-diphenyl-ethylene) to 14.8 ng mL-1 for 7,9-di-tert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione and respective limits of quantification from 1.0 ng mL-1 to 41.7 ng mL-1, for the same analytes. Accuracy and precision results showed that the method is sufficiently accurate for all target analytes, with recoveries ranging between 80 and 110% and relative standard deviations (RSDs) smaller than 16% at the three selected concentration levels. The method has been successfully applied to seven FCM. Results indicated that significant amounts of polystyrene monomers, dimers and trimers are migrating into food simulants; this is also the case for polyester urethane-based oligomers (PU). Exposure assessment estimation was performed using EFSA's approach on the total sum of migrating oligomers. In certain cases, amounts of PS and PU oligomers found to be in some cases higher than the respective limits, for the sum of oligomers with a MW lower than 1000 Da.A methodology for the estimation of the different phase volumes in HILIC is presented. For a ZIC-HILIC column the mobile phase volume (hold-up volume) is determined in several acetonitrile- and methanol-water compositions by a Linear Free Energy Relationships (LFER) homologous series approach involving n-alkyl-benzenes, -phenones, and -ketones. We demonstrate that the column works as a HILIC column when the mobile phase contains high and medium proportions of methanol or acetonitrile. However, for acetonitrile contents below 20%, or 40% for methanol, same column works in RPLC. In between, a mixed HILIC-RPLC behavior is observed, and solutes of low molecular volume are retained as in HILIC mode, but the largest ones show RPLC retention. From the homologous series retention data and pycnometric measurements involving the pure organic solvents and their mixtures with water, the mean solvent composition of the water-rich transition layers between column functionalization and the bulk mobile phase, which act as stationary phase, is estimated. Finally, the phase ratio between stationary and mobile phases is also estimated for each eluent composition, allowing the calculation of the corresponding stationary phase volumes. All volumes are strongly dependent on the water content in the eluent, especially when acetonitrile is selected as mobile phase constituent. In HILIC mode, when the water content in the hydroorganic mobile phase increases, the volumes of mobile phase decrease, but the volumes of stationary phase (mainly the water layer adsorbed onto the bonded-phase and the water-enriched interface) increase. However, at high water concentrations, where the column works in RPLC mode, the mobile phase volume increases and the stationary phase (which is now the bonded zwitterion) volume decreases when increasing the water percentage in the mobile phase.