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).