Background Correction In AAS - Can You Really Trust It As Much As You Do?
Background Correction (BGC) is an essential part of any spectrometric analysis. Typically a non-specific signal, the spectral background, is superimposed on the analyte-specific signal and needs to be excluded to obtain the net analyte signal. Different techniques have been developed to distinguish specific from non-specific signals. In ICP OES with an array detector for example, the spectral background can be calculated from the emission spectrum of a sample by evaluating the baseline on both sides of the analyte emission line.
In traditional Atomic Absorption Spectrometry however, sample spectra cannot be used for this purpose because of the line emission profile of the light source used and the detection system, which make it impossible to record wavelength-resolved signals. For this reason the spectral background must be measured in a separate measurement. Practically, total (specific and non-specific) and background (non-specific only) absorbance are measured alternatingly and automatically subtracted from each other.
Traditionally three different methods are used in AAS: Deuterium-, Zeeman- and Self-Reversal-BGC. In all three cases the instrument software only shows numeric values for Atomic Absorption (AA) and Background (BG). As we will see, these numeric values are sometimes not sufficient because no information is available where they actually come from, and the user must have a certain level of trust in these values without being able to verify them.