Search results for "Spectroscopy"
showing 10 items of 10293 documents
Development of the H-point standard additions method for analyte determinations in unknown matrix
1993
Abstract The development of the H-point standard additions method is proposed in order to obtain the unbiased analyte concentration when the matrix of the sample is completely unknown. A spectral region where the interferent behaviour can be considered linear at three wavelengths must be chosen. The method uses the analytical signal data at these three wavelengths, usually situated in the maxima region of the analyte. Two procedures are proposed in order to know and to locate this behaviour for the unknown interferent. Several binary and ternary mixtures of phenol, 4-chlorophenol and 4-chloro-3-methylphenol as representative examples have been assayed, with accurate (less than 3% relative e…
A mathematical model based on the limit dilution method to obtain linear calibration curves which eliminate the matrix effect in quantitative analysi…
1995
Abstract We propose a mathematical model from an analytical application viewpoint inspired in the limit dilution method. The theoretical development of the model and its results are given. The model shows that there is a linear relation between the inverse of fluorescence intensity and the inverse of the dilution factor; each analytic system (sample, diluent and analyte) is characterised by a general linear function which is easily obtained. The analytical applications arising from this linearity are of great importance in X-ray fluorescence analysis. The following immediate applications are proposed: direct procurement of the total correction factor Y/H, rapid calculation of the fluorescen…
Quantitative electron probe microanalysis of metallic oxide mixtures applying an empirical calibration technique
1997
Abstract An analytical procedure is proposed for the independent quantitative chemical analysis of each element in the presence of other elements in the matrix of a sample by Energy Dispersive Electron Probe Microanalysis. For this purpose, an empirical calibration technique (which we shall call here the JABO method), which studies the variation of the X-ray intensities in terms of the analyte concentration in a chemical system with a complex matrix, is established. The methodology consists of the modification of the unknown sample by addition of a diluent, an internal standard and the analyte itself (dilution-addition method). A mathematical model is proposed to calculate the K parameters …
Multiplexed plasmon sensor for rapid label-free analyte detection.
2013
Efficient and cost-effective multiplexed detection schemes for proteins in small liquid samples would bring drastic advances to fields like disease detection or water quality monitoring. We present a novel multiplexed sensor with randomly deposited aptamer functionalized gold nanorods. The spectral position of plasmon resonances of individual nanorods, monitored by dark-field spectroscopy, respond specifically to different proteins. We demonstrate nanomolar sensitivity, sensor recycling, and the potential to upscale to hundreds or thousands of targets.
Inkjet printing Ag nanoparticles for SERS hot spots
2018
A novel inkjet printing based approach is developed for the fabrication of a customizable platform on glass substrates allowing for surface enhanced Raman spectroscopy (SERS) detection of analytes up to single hot spots generated by the spontaneous aggregation of Ag nanoparticles (Ag NPs) in pL scale droplets. After drying the printed droplets under ambient conditions, trace amounts of the analyte can be detected by SERS given the proximity to NP hot spots. By employing alizarin (10-5M) as a model system and scaling the ink droplet volume from 1 nL to 10 pL, the absolute quantity of hot spots has been derived in the printed droplets allowing detecting up to a few molecules in proximity to i…
Plasmonic Nanosensor Array for Multiplexed DNA-based Pathogen Detection
2019
In this research we introduce a plasmonic nanoparticle based optical biosensor for monitoring of molecular binding events. The sensor utilizes spotted gold nanoparticle arrays as sensing platform. The nanoparticle spots are functionalized with capture DNA sequences complementary to the analyte (target) DNA. Upon incubation with the target sequence, it will bind on the respectively complementary functionalized particle spot. This binding changes the local refractive index, which is detected spectroscopically as the resulting changes of the localized surface plasmon resonance (LSPR) peak wavelength. In order to increase the signal, a small gold nanoparticle label is introduced. The binding ca…
Analysis of basic drugs by liquid chromatography with environmentally friendly mobile phases in pharmaceutical formulations
2017
Abstract Basic drugs are positively charged in the usual working pH (2–8) in reversed-phase liquid chromatography. This gives rise to a strong association with the residual ionized silanols in conventional silica-based stationary phases, which is translated in poor peak shape and high consumption of organic solvent to get appropriate retention times. Micellar mobile phases containing surfactants give rise to modified stationary phases, where silanols are masked, improving the peak shape. However, mobile phases containing the anionic surfactant sodium dodecyl sulfate (SDS) require a small amount of organic solvent to conveniently decrease the retention of cationic analytes. An alternative is…
Simultaneous spectrophotometric determination of calcium and magnesium in mineral waters by means of multivariate partial least-squares regression.
1997
A method for simultaneous spectrophotometric determination of calcium and magnesium in mineral waters using multivariate calibration methods is proposed. The method is based on the development of the reaction between the analytes and Methylthymol Blue at pH 11. Two operational modes were used: static (spectral information) and flow injection (FI) (spectral and kinetic information). The selection of variables was studied. A series of synthetic solutions containing different concentrations of calcium and magnesium were used to check the prediction ability of the partial least-squares models. The method was applied to the analysis of mineral waters and the results were compared with those obta…
Analytical strategies to determine quinolone residues in food and the environment
2007
23 páginas, 5 figuras, 5 tablas.
SIGNAL PROCESSING ALGORITHM FOR SCHLIEREN EFFECT CORRECTION IN FLOW ANALYSIS
2001
Due to the radial refractive index gradients that sometimes develop in flow cells during the travelling of the samples through them, the absorbance records obtained in such conditions have a strange shape, particularly at low analyte levels. To correct this phenomenon, called Schlieren effect, a simple and reliable signal processing algorithm is described in correlation to the detector characteristics of noise. The algorithm is illustrated in nitrite and nitrate determinations with proflavin from more real samples. It has a solid theoretical support and involves the subtraction from the sample records of a smoothed signal, acquired by working with a blank solution.