Fast generic-gradient reversed-phase high-performance liquid chromatography using short narrow-bore columns packed with small nonporous silica particles for the analysis of combinatorial libraries.

The extremely large number of samples generated for the quality control analysis of combinatorial libraries that are developed in the pharmaceutical research for drug discovery requires fast generic methods such as rapid-gradient reversed-phase high-performance liquid chromatography (HPLC). These methods are necessary as standard procedures to produce up to several hundreds of analytical results per day and should be optimized in order to be applied to library products of widely differing polarities. This work presents an optimized generic method using a narrow-bore column packed with 1.5-microm nonporous particles and a completely automated HPLC workstation configured for the best efficiency, throughput, and robustness with this column. A test mix of 12 compounds with a wide polarity range is separated within 1.5 min with a cycle time of 3.5 min. The throughput is further enhanced using a Gilson 233XL dual-injection sampler to feed two parallel HPLC systems in order to perform 34 analyses per hour.

On-line column-switching high-performance liquid chromatography analysis of cardiovascular drugs in serum with automated sample clean-up and zone-cutting technique to perform chiral separation.

A selective and highly reproducible, multi-column HPLC method is described for the analysis of the following cardiovascular drugs: lidocaine, pindolol, metoprolol, oxprenolol, diltiazem and verapamil, in serum. Column-switching devices are employed in combination with advanced separation media technologies for the automated analysis of samples containing complex matrices. The method consists of on-line sample clean-up using a restricted access sorbent, HPLC analysis of the drugs on a microsphere non-porous silica RP-18 column, and front-cutting to perform the chiral separation of pindolol enantiomers on a second HPLC system. Simultaneous control of the two HPLC systems and data analysis is achieved from a single centralized software. The R.S.D. values of the peak areas for spiked serum are less than 1% for metoprolol and oxprenolol, 2-5% for lidocaine, diltiazem and verapamil, and 1.2 and 2.4% for the two pindolol enantiomers. Recoveries, limits of detection and linearities are provided.

A new approach to mixing techniques for enhanced performance in automated sample preparation.

In the automation of sample dilution or derivatization, the performance of the mixing technique employed when adding solvents or reagents to samples is critical. This paper presents a newly developed mixing method, based on conventional aspiration and dispensing of liquid techniques, but which considerably improves the precision of mixing. The paper discusses the results of a comparison of the technique with other methods and describes the application of the technique to several different types of sample solutions, including a highly concentrated glucose solution. The mixing technique was performed on a Gilson XL Sampling Injector, with a 1/25 dilution of a paraben solution in 2 ml vials to give relative standard deviations of 0.2 to 0.3% (N =10).