Flow system for liquid sample introduction in arc/spark excitation sources

Abstract

A flow system based on the monosegmented flow analysis (MSFA) approach is described for delivery of liquid samples to arc/spark excitation sources commonly used in spectrographs. A Carl Zeiss PGS-2 spectrograph, previously automated in the laboratory by replacing its photographic plate detection system with a photodiode array, was employed. The sample is introduced via an injection port into the path to the excitation source, where the liquid sample plug (typically 50 µl) is passed through a hole drilled in a conventional graphite electrode. The arc/spark is applied to excite the sample for a computer-controlled time interval and the light emitted is integrated. After sample measurement, the electrode is cleaned by applying the arc/spark while the water stream, that follow the sample plug, is being pumped. About 25 samples can be analysed per hour. The flow system was evaluated for determination of aluminium (3–50 mg l^–1), lead (5–160 mg l^–1) and mixtures of hafnium (60–120 mg l^–1) and zirconium (600–1300 mg l^–1).