Rapid quantitative turbidimetric spot test analysis of potassium in blood serum

a spot test quantitative turbidimetric method was developed for the determination of potassium in blood serum. the precipitation of potassium is done in basic medium with the classical analytical reagent sodium tetraphenylborate. the measurement of the turbidity is directly performed in this solution without further dilution using a micro-turbidimetric cell developed in this work. blood serum was mixed with the buffer and the analytical reagent solution. the turbidity is measured in a spectrophotometer at 700 nm. the calibration curve is a straight line in the working concentration range, presenting a correlation coefficient equal to 0.9998. the analytical results obtained with this method were compared with those obtained through the use of a potassium ion selective electrode. complete agreement was achieved between the two methods at the 99% confidence level. the observed mean rsd was 3.8%.