| 
      
        | Analyte | Spiked conc. | In bulk | In serum |  
        | (µg mL-1) | % Rec. | % RSD | % Rec. | % RSD |  
        | Prazosin | 8 | 100.08 | 0.009 | 100.04 | 0.004 |  
        | 10 | 99.93 | 0.004 | 99.97 | 0.002 |  
        | 12 | 100.65 | 0.001 | 100.07 | 0.008 |  
        | Amlodipine | 32 | 100.21 | 0.008 | 100 | 0.018 |  
        | 40 | 100.09 | 0.085 | 100.03 | 0.008 |  
        | 48 | 99.55 | 0.002 | 99.98 | 0.001 |  
        | Diltiazem | 16 | 100.17 | 0.007 | 100.06 | 0.011 |  
        | 20 | 100.09 | 0.005 | 99.96 | 0.005 |  
        | 24 | 100.1 | 0.001 | 100.03 | 0.002 |  
        | Verapamil | 48 | 100.05 | 0.002 | 100.05 | 0.004 |  
        | 60 | 99.94 | 0.003 | 99.92 | 0.004 |  
        | 72 | 99.98 | 0.054 | 100.09 | 0.017 |  |