An optoelectronic instrument for the determination of sulphite in beverages

The paper describes an optoelectronic device that has been designed and developed to measure the sulphite concentration in beverages for quality evaluation. A selective and sensitive method for determination of sulphite is based on the reaction with pararosaniline acid bleached dye and formaldehyde solution, which gives violet colored complex having absorption maxima at 560 nm. Lambert–Beer’s law is obeyed in the concentration range up to 25 μg/ml (25 ppm) of test solution within an accuracy of ±0.05μg/ml (0.05 ppm). The instrument involves the use of high intensity green light emitting diode (LED) of wavelength 565 nm as light source. BPW21 photodiode having the relative spectral sensitivity above 90% in the range of 500–600 nm has been used as a detector, for the determination of sulphite concentration.