Trends in Analytical Chemistry, Volume 4 focuses on the advancements of processes, technologies, operations, automation, and applications of analytical chemistry. The selection first offers information on bullet-proof input with an IBM-PC, including trends in pesticide residue analysis; environmental analysis using gas chromatography; and ion-induced spectroscopic methods for the analysis of surfaces, interfaces, and thin films. The text then elaborates on the PROLOG, an artificial intelligence language, and the consideration of FORTH as a good programming environment for laboratory automation. Discussions focus on computer aided optimization in high performance liquid chromatography; porphyrin analysis by reversed-phase high performance liquid chromatography; and liquid chromatography with on-line electron-capture detection. The text elaborates on linear regression and simple statistics calculated with the spread sheet program, SUPERLAC. Discussions focus on lipid membrane technology for chemical and biosensor development; use of chemometrics in apportionment of air pollution sources; and analytical applications of direct chromatographic enantioseparation. The publication is a dependable reference for readers interested in the trends in analytical chemistry.