Development of a New Kinetic Spectrophotometric Method for the Determination of Chromium with an Optical Probe

A new approach for sulfite determination by headspace liquid-phase microextraction with an optical probe

A new approach of headspace liquid-phase microextraction with an optical probe (HS-LPME-OP), which solves the problem of the extraction phase retention in the hole of the optical probe and provides the possibility of simpler, more precise and reliable online processing of the analytical signal, was used for sulfite determination. A 1 × 10^-4 M 5,5'-dithiobis-(2-nitrobenzoic) acid (DTNB) solution was used as an acceptor phase. It was placed in a plastic vial fixed in the headspace above the analyte solution. An optical probe immersed in the acceptor phase was used to monitor the analytical signal. Sulfite determination is based on the release of sulfur dioxide from the sample after the addition of ortho-phosphoric acid, followed by its extraction with an aqueous solution of DTNB at pH 7.0. The absorbance was measured at 412 nm. The calibration graph was linear in the range from 32 to 320 μg L^-1 with a detection limit of 14 μg L^-1. The developed method is sensitive, highly selective and reproducible. It was successfully applied for the sulfite determination in juice, alcoholic beverages and jam.

A fully automated system with an optical immersion probe (OIP) for high-precision spectrophotometric measurements

A new and fully automated system with the interconnection of an Optical Immersion Probe (OIP) - pH meter - peristaltic pump was used to study the spectral and protolytic properties of carbocyanine the dyes 1,1',3,3,3',3'-hexamethylindocarbocyanine chloride (HIC); 1,1',3,3,3',3'-hexamethylindodicarbocyanine iodide (HIDC); and 3,3'-diethyloxadicarbocyanine iodide (DODC). This system can measure a large number of experimental points in a short time period. The effect of 32 various organic solvents on the UV-ViS spectra of the dyes was studied. The solvatochromic behaviour of studied dyes was characterized by positive solvatochromism for HIDC and negative solvatochromism for HIC and DODC. Through the application of a large number of experimental points, the protonation and hydrolysis constants of dyes were determined with high precision, where the confidence interval of the рK values is ±(0.001-0.005), compared with a confidence interval of ±(0.04-0.10) for standard procedures. The fully automated system presented is accurate, fast, environmentally friendly and promising for multiple analytical applications.