Search results for "Analyte"
showing 10 items of 303 documents
A chemometric study of the simultaneous determination of calcium and magnesium in natural waters
1999
A method for the simultaneous spectrophotometric determination of calcium and magnesium in mineral waters with an FIA system is tested. The method is based on the reaction between the analytes and arsenazo(III) at pH 8.5. The calculations of the amounts of both analytes in the samples are carried out with the H-point standard addition method (HPSAM) for ternary mixtures, and with a partial least squares (PLS) model after a proper variable selection. The results obtained for the determination of calcium were comparable using both methods. The employment of the HPSAM brings to our attention the influence of the calcium concentration in the sample to the development of the reaction between mag…
Determination of titratable acidity and ascorbic acid in fruit juices in continuous-flow systems
1993
Two continuous-flow systems for the determination of titratable acidity and ascrobic acid in fruit juice samples are described. The assemblies permit on-line dialysis of analytes prior to the reaction step, thus improving selectivity and performing sample dilution. Flow systems are built with a channel carrying the donor phase (sample in both determinations) and another channel carrying an acceptor phase, both of them entering the dialyser. The outcoming stream transporting the dialysed sample fills the valve loop, permitting its injection into a carrier stream which continuously passes through the spectrophotometric detector. For the titratable acidity, acceptor phase and carrier are disti…
Control of propranolol intake by direct chromatographic detection of alpha-naphthoxylactic acid in urine.
2002
A rapid chromatographic procedure with a C18 column, a mobile phase of 0.15 M sodium dodecyl sulfate (SDS)-10% (v/v) 1-propanol at pH 3 (0.01 M phosphate buffer), and fluorimetric detection, is reported for the control of propranolol (PPL) intake in urine samples, which are injected directly without any other treatment than filtration. The peak of PPL was only observed in samples taken a few hours after ingestion of the drug due to its extensive conjugation and metabolisation. The detection of several unconjugated PPL metabolites was therefore considered: desisopropylpropranolol (DIP), propranolol glycol (PPG), alpha-naphthoxylactic acid (NLT) and alpha-naphthoxyacetic acid (NAC). NLT showe…
Application of solid-phase microextraction combined with derivatization to the enantiomeric determination of amphetamines.
2005
Abstract The utility of combining chiral derivatization and solid-phase microextraction (SPME) for the enantiomeric analysis of primary amphetamines by liquid chromatography has been investigated. Different derivatization/extraction strategies have been evaluated and compared using the chiral reagent o -phthaldialdehyde (OPA)– N -acetyl- l -cysteine (NAC) and fibres with a Carbowax-templated resin coating. Amphetamine, norephedrine and 3,4-methylenedioxyamphetamine (MDA) were used as model compounds. On the basis of the results obtained, a new method is presented based on the derivatization of the analytes in solution followed by SPME of the OPA–NAC derivatives formed. The proposed conditio…
Micellar liquid chromatography determination of rivaroxaban in plasma and urine. Validation and theoretical aspects.
2019
A Micellar Chromatographic method to determine rivaroxaban in plasma and urine has been developed. The samples were dissolved in the mobile phase (SDS 0.05 M – 1-propanol 12.5%, phosphate buffered at pH 7) and 20 μL directly injected, avoiding the extraction and purification steps. Using a C18 column and running under isocratic mode at 1 mL/min, analyte was eluted without interference from the matrix in <6.0 min. The detection absorbance wavelength was set to 250 nm. The procedure was validated by Food and Drug Administration guidelines in terms of: system suitability, calibration range (0.05–5 mg/L), linearity, sensitivity, robustness, carry-over effect, specificity, accuracy (−11.1 to 4.2…
Computer simulations for bioequivalence trials: Selection of analyte in BCS class II and IV drugs with first-pass metabolism, two metabolic pathways …
2018
A semi-physiological two compartment pharmacokinetic model with two active metabolites (primary (PM) and secondary metabolites (SM)) with saturable and non-saturable pre-systemic efflux transporter, intestinal and hepatic metabolism has been developed. The aim of this work is to explore in several scenarios which analyte (parent drug or any of the metabolites) is the most sensitive to changes in drug product performance (i.e. differences in in vivo dissolution) and to make recommendations based on the simulations outcome. A total of 128 scenarios (2 Biopharmaceutics Classification System (BCS) drug types, 2 levels of KM Pgp, in 4 metabolic scenarios at 2 dose levels in 4 quality levels of t…
Materials and methods of signal enhancement for spectroscopic whole blood analysis: Novel research overview
2017
Abstract The early diagnosis of diseases is crucial for reducing morbidity and mortality and also for improving the quality of treatment process. Among various biological samples used to follow up the concentrations of disease markers, whole blood sensing can efficiently decrease analysis time by means of introducing methods with no pretreatment. In addition, the direct detection of markers in whole blood facilitates testing procedure and minimize the possibility of the loss of analytes in the process. Therefore, the assay of unprocessed whole blood is becoming increasingly important in clinical diagnostics and biomedical research. Incorporation of new advanced materials plays a major role …
Affinity Sensors for the Diagnosis of COVID-19
2021
The coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was proclaimed a global pandemic in March 2020. Reducing the dissemination rate, in particular by tracking the infected people and their contacts, is the main instrument against infection spreading. Therefore, the creation and implementation of fast, reliable and responsive methods suitable for the diagnosis of COVID-19 are required. These needs can be fulfilled using affinity sensors, which differ in applied detection methods and markers that are generating analytical signals. Recently, nucleic acid hybridization, antigen-antibody interaction, and change of reactive oxyge…
Determination of the herbicide benfuresate by its photo-induced chemiluminescence using flow multicommutation methodology.
2007
The present paper deals with an analytical strategy based on coupling photo-induced chemiluminescence in a multicommutation continuous-flow methodology for the determination of the herbicide benfuresate. The solenoid valve inserted as small segments of the analyte solution was sequentially alternated with segments of the NaOH solution for adjusting the medium for the photodegradation. Both flow rates (sample and medium) were adjusted to required time for photodegradation, 90 s; and then, the resulting solution was also sequentially inserted as segments alternated with segments of the oxidizing solution system, hexacyanoferrate (III) in alkaline medium. The calibration range from 1 microg L(…
Development of a Rapid Method for the Determination of Phenolic Antioxidants in Dark Chocolate Using Ultra Performance Liquid Chromatography Coupled …
2017
Development of a new comprehensive method based on one-step liquid-liquid extraction (LLE) combined with ultra-high-performance liquid chromatography-Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap-HRMS) for the determination of eight phenolic compounds in dark chocolate is demonstrated. The study focuses on the optimization of sample preparation, chromatographic separation and Orbitrap-HRMS detection parameters to adjust selectivity and sensitivity of the method. The LLE mixture of formic acid-water-acetonitrile (2:58:40, v/v) and hexane at the component ratio of 1:1 (v/v) was applied for sample preparation. The inter-day and intra-day precision expressed from the relative stand…