Development and validation of an LC/MS/MS method for the determination of L-hyoscyamine in human plasma.

A sensitive and specific LC/MS/MS method for the determination of L-hyoscyamine was developed and validated over the linearity range 20-500 pg ml-1 with 1.0 ml of plasma using scopolamine as the internal standard. The API III-Plus LC/MS/MS was operated under the multiple reaction monitoring mode using the atmospheric pressure chemical ionization technique. The instrument parameters were optimized to obtain 1.8 min run time with baseline separation of the internal standard from L-hyoscyamine. The between-run precision and accuracy of the calibration standards were 1.2 to 5.0% RSD and -4.5 to +2.5% relative error (RE). The within-run precision and accuracy of quality controls (60, 150 and 350 pg ml-1) were 1.9-3.4% RSD and -3.3 to +5.1% RE. Stability of L-hyoscyamine in human plasma and processed samples has been established.