Yf. Cheng et al., Simplified procedure for the determination of codeine and its metabolite in urine and plasma by LC/UV and LC/MS using mixed-mode cation exchange for sample preparation, J LIQ CHR R, 24(9), 2001, pp. 1353-1364
Novel mixed-mode cation exchange (MCX) and HPLC methods were developed to d
etermine codeine and its metabolite from human urine and porcine plasma. Fo
r sample cleanup, spiked sample solutions were acidified followed by a well
-thought-out MCX method using 3 cc, 60 mg Oasis(R) MCX cartridges. In this
MCX method there is no need to condition and to equilibrate the sorbent; th
e sample is loaded directly onto the sorbent. Recoveries from human urine a
nd porcine plasma matrices were greater than 87% with RSDs less than 5.4%.
For the HPLC analysis, the separation was obtained using a Symmetry(R) C-18
column with a simple mobile phase of 0.05% TFA/acetonitrile/methanol at 90
.5.5. Good peak shapes were obtained without the need of addition of any co
mpeting reagent to the mobile phase.