Search results for "Standard curve"
showing 6 items of 26 documents
Determination of ammonia and primary amine compounds and Kjeldahl nitrogen in water samples with a modified Roth's fluorimetric method.
2005
Abstract A method for the simultaneous determination of primary amino groups and ammonium ion has been proposed. The method is based in solution derivatization with o-Phthaldialdehyde/N-acetyl-cisteine (OPA/NAC) and fluorescence measurement of the formed isoindols. Analytical characteristics and description of the developed procedure have been provided. The calibration graphs for ammonium (up to 1.44 mg L−1 of N) and methylamine as primary amino model compound (up to 0.282 mg L−1 of N), were obtained. Bivariate and multivariate calibration models have been tested. The limits of detection were 0.07 mg L−1 of N and 0.004 mg L−1 of N for ammonium and amine, respectively. The procedure was firs…
Towards minimization of chlorinated solvents consume in Fourier transform infrared spectroscopy determination of Propamocarb in pesticide formulation…
2008
Abstract A method has been developed for Fourier transform infrared (FTIR) spectroscopy determination of Propamocarb in emulsifiable pesticide concentrate formulations. Five microliter sample was directly injected without any pretreatment in a CHCl 3 stream at 2 mL min −1 into a closed system and the FTIR spectra of sample and standard solutions were obtained using a nominal resolution of 4 cm −1 from 4000 to 900 cm −1 spectral region and accumulating 2 scans per spectrum. Propamocarb determination was based on the measurement of flow injection analysis (FIA) recording height established from FTIR peak area measurements from 1713 to 1703 cm −1 corrected using a baseline defined at 2000 cm −…
Elimination of the unknown irrelevant matrix absorbance by using the H-Point Standard Additions Method (HPSAM)
1994
It is demonstrated how the H-Point Standard Additions Method (HPSAM) using DeltaA as analytical signal (from data at three previously selected wavelengths) is only related with analyte concentration when unknown irrelevant matrix absorbance is present. The method is compared with the most common previously reported methods, such as derivative spectroscopy or the compensation method. The obtained results show that the proposed HPSAM leads to the same found concentration of analyte as the other reported methods, except detection limits and standard deviation for six replicates which are lower, because of the use of absorbance data (instead of first derivative data as usual). In addition, the …
Pressurized liquid extraction followed by liquid chromatography–mass spectrometry for determination of zearalenone in cereal flours
2010
Abstract A method for determination of zearalenone in cereal flour has been developed applying pressurized liquid extraction (PLE) using methanol/acetonitrile (50:50 v/v) as the extraction solvent. The extracted samples were analyzed with liquid chromatography coupled to mass spectrometry (LC–MS) with an electro spray ionisation interface (ESI). The method was validated as a quantitative confirmatory method according to the Eu Commission Decision 2002/657/EC. Recoveries of the extraction step data were satisfactory with values higher then 70%. Quantification limits (LOQ) were 5 μg/kg for ESI (+) and 1 μg/kg for ESI (−). Twenty one flour samples produced in different countries were extracted…
Quantitative analysis of chromite ores using glass discs in moderate dilutions of lithium tetraborate by x-ray fluorescence spectrometry
2006
A method for the quantitative analysis of chromite ores by x-ray fluorescence spectrometry using beads is proposed. The work concerned the serious problems caused by the refractory nature of these materials which prevents the use of glass discs in x-ray fluorescence. An in-depth study was done to optimise the variables which influence the glass disc formation process. Sufficiently homogeneous glass discs were obtained under the following experimental conditions: lithium tetraborate as flux with moderate sample dilution (1:40), with the addition of one or two drops of LiBr solution(250 g l−1), at a temperature of 1200 °C for 30 min. The qualitative and semiquantitative results for the chromi…
A new procedure for the Antioxidant capacity dpph assessment in small samples.
2018
The antioxidant capacity of a substance is its ability to prevent or slow down oxidation. This reaction is a transfer of electrons. The molecule catching electrons is the oxidative agent and the molecule giving electrons is the reducing agent. Oxidative stress is toxic for the cells, and it can be limited by different pathways: the inhibition of enzymes responsible of the production of oxidative species, the synthesis, activation or stabilization of antioxidant enzymes, and finally by direct scavenging of radical species. In living organisms, especially in association to the respiration process, free radicals are commonly produced. Antioxidant are naturally present to prevent damages, and t…