Simultaneous SIA analysis of pH and total acidity measurements in milk

Abstract

The development of a sequential injection analysis method for automatic determination of pH and total acidity in milk is proposed. For this purpose, firstly, three micro-sized composite pH electrodes were prepared and tested. A microliter dead volume flow-cell was designed for composite pH and reference electrodes. Potentiometric performance characteristics of the pH electrodes were examined by a computer-controlled potentiometric system in both stagnant and flowing environments. Three different micro-columns with the best working pH electrode were applied on the flowing stream line in the sequential injection analysis system to fulfill the titration efficiency for total acidity. The sequential injection analysis system was optimized for two parameters (pH and total acidity) by testing all the variables. Mobile phase concentration, volume and flow-rate together with sample concentration, volume and sample flow-rate were fixed for the best stable values by arranging the experimental programming steps. Total acidity of ten different milk samples was analyzed using the sequential injection analysis system developed. The same samples were also titrated in the classical way using phenolphthalein indicator for the comparison. The results of both methods analyzed statistically by SPSS software were found to be compatible with each other. pH analysis of ten different milk samples carried out by using the sequential injection analysis system were also measured with a glass electrode. The results obtained by both methods analyzed by SPSS were also found to be compatible with each other.