Improved detection limits for transient signal analysis of fluid inclusions by inductively coupled plasma atomic emission spectrometry using correlated background correction

Abstract

The detection limits for ICP-AES bulk analysis of fluid inclusions by thermal decrepitation are limited by fluctuations in background emissions from the plasma. The transient nature of the analyte signal prevents sequential off-peak estimation of background levels. The established technique of time-interpolation of background signals measured between the analyses of samples gives somewhat unrealistic estimates because the background is not measured during the decrepitation event. A new procedure, correlated background correction (CBC), uses the high degree of correlation between the relative fluctuations in the spectral background at different wavelengths to effectively predict the background emission under transient analyte peaks. An estimate of the spectral background is made at a wavelength with no analyte signal or spectral interference, in this case 371.030 nm which is otherwise used to measure yttrium. The relative fluctuation in this intensity is used to predict the background emission intensity at all analyte wavelengths during the decrepitation event. The detection limits achieved using CBC are improved typically by a factor of five over those estimated without any correction of background fluctuation, thus increasing the range of sample material amenable to analysis.