Graham D. Marshall

Sequential injection : a new concept for chemical sensors, process analysis and laboratory assays

Abstract Established flow-injection techniques allow advanced solution handling for laboratory purposes, but chemical sensing and continuous monitoring of chemical processes require dramatically simplified flow schemes and instrumentation with the potential for miniaturization and an inherent ruggedness. Considerations based on the random walk model have led to the concept of sensor injection and sequential injection analysis. This new approach to automated analysis is designed to fill a gap in present flow-injection methodology.

Trace metal atomic absorption spectrometric analysis utilizing sorbent extraction on polymeric-based supports and renewable reagents

Various methods of analyte preconcentration for atomic absorption spectrometry are available for trace metals in aqueous samples. Among the drawbacks of many of these techniques are the generation of hazardous or toxic wastes, poor preconcentration efficiencies and cumbersome on-line implementation of the particular technique. Preconcentration of trace metals by sorbent extraction utilizing a flow injection method is described. Preconcentration of the analyte is accomplished by its extraction on a solid-phase hydrophobic support prepared by adsorption of a suitable chelating agent. Following extraction of the analyte, the metal–chelate complex is eluted from the solid support by changing the polarity of the carrier stream. The metal systems chosen for examination were copper and lead chelates of diethyldithiocarbamate (DDC) and quinolin-8-ol. Some results are presented for other chelates, namely 4-(2-pyridylazo)resorcinol, 1-(2-pyridylazo)-2-naphthol and dithizone. The sample throughput of the method was 20 h–1 utilizing 2 ml of sample per analysis for preconcentration. The detection limits using the quinolin-8-ol and DDC chelates are at low parts-per-billion levels, with enhancement factors between 50 and 100.