Analytical methods development and troubleshooting for high-performance liquid chromatography and fast gas chromatography.

摘要

The development and validation of analytical chemical methods using both high performance liquid chromatography (HPLC) and gas chromatography (GC) are reported. Whenever new methods of measurement are developed, the results must be validated by comparison to existing, or standard, methods of analysis. Systematic comparisons of performance are required to prove the validity of the test results and to establish claims of method improvement. Traditional statistical approaches for method comparison (t-tests and regression analysis), as well as non-traditional approaches (principal component analysis and Youden plots), were coupled with computer graphics to judge the degree of agreement between GC- and HPLC-based methods for the analysis of caffeine content in beverages. Established methods sometimes develop problems, and newly developed methods rarely work perfectly the first time. Problem troubleshooting to resolve issues of carry-over, contamination, and background correction for HPLC methods is also discussed.; A robust and fast liquid chromatographic/mass spectrometric method for the analysis of up to 18 commonly abused benzodiazepines (BZDs) in blood or urine samples has been developed. Theoretical relationships between retention and mobile phase composition were employed, based on an initial linear gradient analysis, to predict the mobile phase composition for each step of a multiple ramp gradient that was capable of achieving a specified resolution between adjacent peaks. The developed method provided rapid analysis for a broad range of forensically relevant BZDs.; A Thermo-Orion EZ-Flash(TM) GC accessory was used for high-speed gas chromatographic screening and mass spectrometric confirmation of benzodiazepines in blood and urine. Direct resistive heating of the column enables extremely rapid temperature programming, and produces analyses ca. three times faster than achievable using conventional GC methods. Forensic case samples were analyzed to evaluate applicability of the method to routine testing.; A HPLC method for determining the age of bloodstains was investigated. The presence of previously reported chemical markers for aging was confirmed. A multiple wavelength detector provided increased information content compared to single wavelength analyses and aided in determination of time trends during the course of the experiment.