Handling Low Frequency Drifting Background Noise in Data from a Swept-Potential Electrochemical Detector


Chemistry and Biochemistry

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The quality of measurements obtained from high-performance liquid chromatography using electrochemical detection is often obscured by both the low-frequency drifting background noise and the high-frequency background noise. While the quality of measurements can be greatly improved by digital filtering techniques which are capable of minimizing high-frequency noise, these techniques are very limited in handling low-frequency drifting background noise. A method for effectively performing background correction (the moving band method) has been developed and applied to a few chemical systems which were studied in our laboratory. The method examines each sweep (chromatograms or voltammogram) for the presence of the analyte peak. Once the peak has been detected, the base of the peak is then generated by interpolation and then refined visually by adjusting the base peak width. The generated base, along with the data points which do not contain the peaks, constitutes the background of that sweep. This background is then subtracted from the original sweep, leaving the analyte signal on a flat baseline. Before the method is applied to a sweep, high-frequency noise is removed by fast Fourier transforms digital filtering. The moving band method is tested and evaluated using data matrices of nitrophenols and catecholamines at concentrations of about 5.0 ng/10 μL where the drifting background noise is significant. The quality of the data matrices is greatly improved due to the improved signal-to-noise ratios.