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A simple high-performance liquid chromatographic (HPLC) method with photometric detection is described for the determination of vardenafil hydrochloride, a phosphodiesterase V inhibitor, in human plasma. Chromatographic separation of the analyte and internal standard was achieved on an analytical 250 x 4.6 mm i.d. reversed-phase Kromasil KR 100 C(18) (5 microm particle size) column using a mobile phase of acetonitrile-potassium dihydrogen phosphate (30:70 v/v). The run time was less than 15 min. Column eluate was monitored at 230 nm. The linearity over the concentration range of 10-1500 ng/mL for vardenafil was obtained and the limit of quantification (LOQ) was 10 ng/mL. The method has been applied to analysis of the vardenafil concentrations for application in pharmacokinetic studies.

Only a small proportion of old specimens contain DNA that can be amplified by PCR. Therefore, rapid screening methods are crucial to identify the large fraction of samples that are so badly preserved that there is no need to attempt DNA extraction. In particular, the extent of racemization of some amino acids has proved to be a very useful proxy for DNA preservation. In this study, a rigorous method for the determination of the D/L ratio for aspartic acid and alanine by RP-HPLC with fluorescence detection was developed with the aim to obtain a fast and cheap procedure for both sample preparation and amino acids analysis, without compromising precision and accuracy.

An HPLC method with DAD detection was developed and validated for the simultaneous determination of zofenopril and hydrochlorothiazide in tablets. The separation was carried out through a gradient elution using an Agilent LiChrospher C18 column (250x4.0 mm id, 5 microm) and a mobile phase consisting of (A) water-TFA (99.9:0.1 v/v) and (B) acetonitrile-TFA (99.1:0.1 v/v) delivered at a flow-rate of 1.0 mL/min. 8-Chlorotheophylline was used as internal standard. Calibration curves were found to be linear for the two drugs over the concentration ranges of 5.0-40 and 1.0-20 microg/mL for zofenopril and hydrochlorothiazide, respectively. Linearity, precision, accuracy, specificity and robustness were determined in order to validate the proposed method, which was further applied to the analysis of commercial tablets. The proposed method is simple and rapid, and gives accurate and precise results.