Abstract: The use of packed sample loops to minimize band-broadening in flow injection analysis was studied. For test analytes detected directly or after reaction with a reagent, lower dispersion and improved detection limits were achieved with packed or distorted sample loops compared with those achieved with empty sample loops. Results are presented for ethyl methyl ketone and pyridoxal. In order to achieve max. sensitivity in flow injection anal., sample dispersion must be kept to a min. This dispersion process, however, is not well understood. Studies of the dispersion process have concentrated on dispersion within the flow manifold while dispersion due to the injection process has been largely ignored. Here sample injection loops packed with inert glass beads and a Serpentine II (distorted) empty loop were constructed and compared to traditional empty sample loops. Digitization of the response curves and subsequent calculation of the statistical moments were used to compare the contribution of each sample loop type to the total system dispersion. Both packed and Serpentine II sample loops were shown to decrease dispersion and increase throughput in flow injection systems. Plots of peak variance vs. injection volume show variance increasing 1.67 times faster with traditional open sample loops compared to packed loops. When combined with other peak width minimization techniques, this method should further lower concentration. limits of detection.

Abstract: Studies were performed in an aqueous/chloroform segmented flow stream. The absorbance of each chloroform segment was measured as it passed through an on-tube photometer located at various distances along the Teflon extraction tube. Band broadening, studied by injecting iodine into a single chloroform segment, is intermediate in magnitude between that predicted by using a mixing chamber model and that predicted by assuming only diffusional mixing between the segments and the wetting film of chloroform on the tube wall. Extraction from aqueous Into chloroform segments was studied by generating iodine within a single aqueous segment using the "Iodine clock" reaction. Application of a "successive reaction" model to the axial extraction from the front of the aqueous segment reveals that, in straight tubes, solute extracts at the same rate per unit area across ail of the interface, at both the segment ends and side.