Capacitive-Discharge Circuit for Controlled Heating of Anisotropic Graphite Tubes. Part II: Characterization for Graphite Furnace Atomic Absorption

Abstract

Performance data from a recently described capacitive-discharge heating system are presented. The capacitive-discharge heating circuit, which used a 0.15 F capacitor bank, is shown to provide reproducible heating of a small anisotropic graphite tube (5 mm o.d. × 9 mm long, 1 mm wall thickness) at heating rates of up to 65°C per ms to a final temperature of 2500°C. The performance and resistance of graphite from two manufacturers are compared. The effect of the capacitor bank voltage on the heating rate and maximum achievable temperature is studied. Photographic and optical pyrometric evidence of the circumferential temperature anisotropy is presented. Pyrolytically coated anisotropic graphite tubes were investigated. Preliminary investigations using Pb indicated that sample deposition on the unbroken lamellar graphitic planes provides about 1.5 times the peak-area and peak-height sensitivity obtained from sample deposition across the lamellar planes.