Analyte (urine samples) Concentration (ng/mL) Precision RSD (%) Accuracy (%) Intra-day Inter-day Nitrendipine Nisoldipine 50 200 500 50 200 500 6.83 5.85 5.35 8.62 7.13 4.82 6.74 4.26 5.84 9.35 6.52 7.36 99.6 98.8 100.4 95.7 101.1 89.8

Table 2: Intra- and inter-day precisions and accuracies of nitrendipine and nisoldipine in human urine samples at three different concentrations.