Plasma samples obtained from healthy volunteers were subjected to the spe procedure described above and analysed with both methods 1 and 2. The electropherogram and chromatogram obtained are shown in Fig. 3a and b, respectively. As can be seen, a complete removal of possible interferences was obtained.
The same blank plasma sample was spiked with arp (150ngml) and the I S (300ngml) then treated as described. The according electropherogram and chromatogram shown in Fig. 3c and d agree with those of the standard solution.