INDIRECT DETERMINATION OF THE HYDROGEN INDEX OF SMALL VOLUME SOLUTIONS BY DIGITAL COLORIMETRY

A technique for indirect determination of the hydrogen index of aqueous solutions of small volume (from units to hundreds of µl) by digital colorimetry with the use of consumer optical raster imaging devices is proposed. To find pH, no fixed color scales or information on the concentration of acid-base indicator in the solution is needed. A prototype of a hand-held analyzer based on a smartphone was developed for out-of-laboratory applications. The accuracy of pH determination results was confirmed by ionometry and spectrophotometry techniques.