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.