On-line atomization of selenium hydride in graphite furnaces: estimate of atomic absorption coefficient and spectroscopic temperature

Abstract

A transversely heated graphite tube atomizer (THGA) has been employed to ensure constant temperature within the observation volume. A method of sampling of gaseous selenium hydride from a container has been developed including a relation between observed peak area (integrated absorbance) and selenium mass injected into the furnace. This makes it possible to control fully the composition of the atomizer atmosphere. A boron nitride tube sealed to the injection hole of the graphite tube has been used as the interface. It performed well even at the highest tested atomization temperature (2400°C). Spectroscopic temperature measurements based on atomic absorption at the 196.1 nm and 204.0 nm Se lines have been used to determine the influence of carrier gas flow rates on the effective gas phase temperature in the atomizer at set furnace temperatures of 1800°C and 2200°C. Characteristic masses m 0 at the 196.1 nm line, in pure argon atmosphere, have been determined at these set furnace temperatures for various argon gas flow rates. The data are employed to estimate an experimental value of the atomic absorption coefficient: (17.1 ± 0.8) × 10 −18 m 2. The value does not significantly differ from the theoretical value. m 0 values found for the temperature range 1800–2400°C for the hydride injection into the furnace at the minimum feasible carrier gas flow rate are compared with characteristic masses for the traditional liquid sampling to the furnace in the same temperature range. This made it possible to estimate that the analyte losses through the injection port in the case of the traditional liquid sampling to the furnace are in the range 20–25%.