Simultaneous measurements of signal and background in inductively coupled plasma atomic emission spectrometry: Effects on precision, limit of detection and limit of quantitation

Use of simultaneous measurements of the line intensity and the off-peak background intensity results in a significant improvement of repeatability at low concentrations, the limit of detection and the limit of quantitation in inductively coupled plasma atomic emission spectrometry. Simultaneous measurements have been performed using an echelle-based dispersive system equipped with a custom segmented-array charge coupled device detector. Correlation between background signals, and shape of the curve of the RSD of the net signal as a function of the concentration is studied from both a theoretical and practical aspect. Concepts of limit of detection and limit of quantitation are discussed both in terms of RSD of the net signal and correlation. Results have been obtained using the Ba II 455 nm line in the visible region and the Ni II 231 nm line in the UV region. Improvements in the limit of detection and limit of quantitation are up to a factor of 10 and are in good agreement with theoretical values. The main limitation of the procedure is related to the accuracy of the background correction.