Electrochemical Quantitative Analysis of Uric Acid in Milk

Abstract

Analysis of cows' milk by cyclic voltammetry using a carbon electrode showed an oxidation wave at a potential around + 0.8V with respect to a saturated calomel electrode. The compound responsible for the wave was determined to be uric acid. The electrochemical assay of uric acid was without preliminary treatment of the milk. A concentration of 3.3 x 10v2 g&. milk was detectable. The method proved highly accurate, rapid and precise [coefficient of variation = 3%].

The occurrence and nature of electrochemical activity in milk from a herd of dairy cows

“…The conclusion that uric acid is the principal interferent in whey and de-proteinized milk is consistent with those of Chen et al (2002) and Jawad et al (1991). Ascorbic acid may well be an interferent also, but any ascorbic acid present was elusive (presumably because of its instability), as also noted by Chen et al (2002).…”

“…The exact relative importance of the various determinants -diet, stage of lactation etc -of levels of uric acid in milk are uncertain but it can be expected that uric acid is a common component of milk that sensor technologists have to deal with, for example, in amperometric determinations of lactate (Marraza et al 1994) and progesterone (Pemberton et al 2001). It certainly occurred in milk products such as powdered skim milk (Jawad et al 1991) and pasteurized supermarket milk (Ostdal et al 2000) that would have been derived from large numbers of cows.…”

A simple and sensitive method for lactose detection based on direct electron transfer between immobilised cellobiose dehydrogenase and screen-printed carbon electrodes

“…The response of the CDH modified SPCEs as a function of pH showed that the response current for both immobilised enzymes attained a maximum at pH 4.5 (citrate buffer containing 0.1 M KCl), that was used in the following experiments. In order to minimise enzyme inactivation, possible interferences from other components, which might be present in the sample (e.g., ascorbic, uric acids) [29][30][31][32] but, on the other hand, still be able to detect the analyte with a high sensitivity a potential of 100 mV vs. pseudo Ag|AgCl (which is formed on the surface of the reference electrode due to the presence of KCl in the working buffer) was chosen for all further experiments. A flow rate of 0.57 mL min −1 provided a good combination of both high and rapid analytical response for the chosen system and was used for further experiments.…”

Voltamperometric Discrimination of Urea and Melamine Adulterated Skimmed Milk Powder

“…Even though the reacting species present in the samples are not known, in 1991, Jawad et al [36] using a carbon paste electrode versus Ag/AgCl sat and performing cyclic voltammetries in milk postulated that uric acid is the responsible for an anodic peak at +845 mV.…”