2.4. Procedure for the real sample preparations
One AA tablet (4.01 g) was dissolved in 500 mL of doubledistilled
water, and then diluted 12 times with a 0.10M phosphate
buffer solution before the measurements. The NA injection
solution and urine sample were diluted 100 times and
40 times with 0.10M phosphate buffer solution, respectively.
The diluted sample solutions were placed in an electrochemical
cell to determine their concentrations using the DPV
method.