Combination of knotted reactor with portable tungsten coil electrothermal atomic absorption spectrometer for on-line determination of trace cadmium

In this work, flow injection (FI) on-line precipitation-dissolution in a knotted reactor (KR) was established and combined with a portable tungsten coil electrothermal atomic absorption spectrometer (W-coil ET-AAS) firstly for preconcentration and determination of ultra-trace cadmium. As a new instrument, the application of the portable W-coil spectrometer was expanded to carry out on-line preconcentration and detection through the coupling with a KR system. A self-assembled FI system was employed to hyphenate the KR system with W-coil ET-AAS. The instrumental conditions and influencing factors relevant to KR efficiency, such as concentration of ammonia, pH, conditions of sampling and elution were studied systematically. The coupling improved the analytical performance of the portable spectrometer considerably. Under the optimal conditions, the limit of detection (LOD) for cadmium was 0.006 μg/L, with sensitivity enhancement factor (EF) of 41. The established method could be expanded and used for on-line preconcentration and detection of some other trace metal ions.