Search results for "analytical"
showing 10 items of 9586 documents
More about sampling and estimation of mercaptans in air samples
2013
[EN] Several strategies have been developed for sampling and determination of volatile thiols. The selectivity and sensitivity of the proposed methodologies are achieved by using a specific derivatizing reagent. The different procedures assayed are based on air sampling followed by derivatization of the analytes with OPA and isoleucine in alkaline solution. The derivatization products are separated and determined by liquid chromatography and fluorescence detection. To start, the derivatization conditions and stability of the derivates have been studied in order to establish the storage conditions. In general, the strategies studied consisted on trapping and detivatization the thiol compound…
Comparison of silica-based materials for organophosphorus pesticides sampling and occupational risk assessment.
2020
Abstract A novel air sampler has been designed containing a sorbent based on UVM-7 mesoporous silica doped with Ti. The sorbent has been applied for the determination of organophosphorus pesticides in occupational air, followed by gas chromatography with mass spectrometry detection. Thus, several silica materials with different structures (mesoporous UVM-7 and microporous xerogels) were synthesized, and modified with the addition of Ti and Fe. The structure of these materials was proved by transmission electronic microscopy, energy-dispersive X-ray, X-ray diffraction, nitrogen adsorption-desorption and UV–Vis and Raman spectroscopy. The potential of these materials for the retention of pest…
Development of a selective solid phase extraction method for nitro musk compounds in environmental waters using a molecularly imprinted sorbent
2013
A powerful analytical method for the determination of the family of the nitro musk compounds at trace level in environmental waters-river, sea, and water from a treatment plant-is presented. The method is based on the use of molecularly imprinted silica (MIS) as sorbent for solid phase extraction (SPE) used for the clean-up and the concentration step of the target analytes previous to their determination by gas chromatography-mass spectrometry. The optimized extraction procedure allowed extraction recoveries between 61% and 87% using the MIS. The comparison with a non-imprinted silica (NIS) sorbent, for which extraction recoveries between 8% and 26% were obtained, showed the high selectivit…
A solid colorimetric sensor for the analysis of amphetamine-like street samples.
2016
A solid sensor obtained by embedding 1,2-naphthoquinone-4-sulfonate (NQS) into polydimethylsiloxane/tetraethylortosilicate/silicon dioxide nanoparticles composite has been developed to identify and determine amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxymetamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA). The analytes are derivatized inside the composite for 10 min to create a colored product which can be then quantified by measuring the diffuse reflectance or the color intensity after processing the digitalized image. Satisfactory limits of detection (0.002–0.005 g mL−1) and relative standard deviations (<10%) have been achieved. The proposed kit has been successfu…
Tips on ligand immobilization and kinetic study using surface plasmon resonance.
2016
Surface plasmon resonance (SPR) technique offers a robust label-free approach applicable in various investigations including binding affinity, specificity and kinetics of biological macromolecules (e.g., peptides, proteins and nucleotidase) and small molecules. SPR provides extremely important data on the kinetics and affinity of substances examined, through which bio-specific interaction(s) can be established by the analysis of adsorption of analyte onto the immobilized ligand(s) on a sensor-based analytical system. Due to SPR wide applications in biomedical laboratories, the aim of this editorial is to highlight the importance of SPR in affinity kinetics and ligand immobilization.
An investigation of the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in authentic urine samples.
2004
Preanalytical stability of a drug and its major metabolites is an important consideration in pharmacokinetic studies or whenever the analyte pattern is used to estimate drug habits. Firstly, the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH, THCCOOglu) in authentic urine samples was investigated. Random urine samples of cannabis users (n = 38) were stored at -20, 4, and 20 degrees C up to 15 days and up to 5 days at 40 degrees C, and alterations of the analyte pattern during storage were followed by liquid chromatography-tandem mass spectrometry. Secondly, the influence of pH (range 5.0-8.0) on the stability of the analytes was studied us…
Hyperbolic subtraction method: Determination of the concentration of an analyte in the presence of an unknown interferent via spectral data.
2018
A theoretical model to determine the concentration of an analyte in the presence of unknown interferents using spectral-type data is described. The method involves absorbance measurements at three wavelengths and the calculation of specific absorbances yielding a hyperbolic relationship between absorbance ratios and analyte concentrations. The concentration of the analyte of known spectrum can be determined in the presence of an interferent or mixture of interferents of unknown concentration(s) and spectra can be determined combining data for different sets of wavelengths. Application to indigo and isatin solutions in DMSO related to the so-called Maya blue problem is reported as an illustr…
The H-point and generalized H-point standard additions methods for flow injection procedures.
1997
This paper establishes the fundamentals of the H-point standard additions method (HPSAM) and generalized H-point standard additions method (GHPSAM) in the flow injection technique. Two kinds of analytical signals can be employed, FIA peaks and spectra. Different analytical problems have been studied: determinations of one analyte in the presence or absence of matrix effect when different blank features are present, and determination of two analytes in the presence of blank bias error affecting the development of one of them. The determination of chloride with mercury thiocyanate which presents a matrix effect, and the determinations of calcium and/or magnesium with arsenazo III are examined…
Observation of interaction forces by investigation of the influence of eluent additives on the retention behavior of aqueous nanoparticle dispersions…
2020
The investigation and subsequent understanding of the interactions of nanomaterials with components of their surrounding media is important to be able to evaluate both potential use cases as well as potential risks for human health and for the environment. To investigate such interactions, asymmetrical flow field-flow fractionation (AF4) is an interesting analytical tool. This statement grounds on the fact that interactions of the analyte with the membrane and with components of the eluent are crucial for the retention behavior of the analyte within the field-flow fractionation (FFF) channel. Therefore, the investigation of the retention behavior provides an insight in the nature of the int…
Determination of biochemical parameters in human serum by near-infrared spectroscopy
2014
NIR offers multiple advantages for serum analysis, permitting a fast and direct determination of several parameters simultaneously, with low sample handling and without the need for reagents during the measurement step. The aim of this paper was to provide an evaluation of this technique in a real world scale, for the simultaneous determination of several parameters and based on a considerable number of samples. Direct near infrared (NIR) absorbance measurements were used to determine the concentration of clinical parameters in human serum that are required in routine biochemical tests. Total protein, albumin, total cholesterol, high-density lipoprotein (HDL cholesterol), low-density lipopr…