Determination of drug levels in human serum by circular dichroism.

A study of the applicability of circular dichroism (CD) for the determination of drug levels in human serum is described and a new method for the quantitative determination of optically active absorbing drugs having Cotton effects at wavelengths about 250 nm in human serum and/or plasma is proposed. The principal advantages of this method are speed, economy, and simplicity, no derivatization or chromatographic separation steps being needed. The validity of the CD determination was confirmed by analysis of variance, beta-lactam antibiotics being chosen as model drugs. In addition, the validation studies performed confirm the accuracy and precision of the proposed method. For beta-lactam antibiotics lacking Cotton effects above 250 nm, an alternative method based on the extraction of the drug from serum is considered.