Noise and baseline disturbances in indirect UV detection in capillary electrophoresis

Investigation of the effects of wall adsorption of the visualization agent on baseline noise characteristics for indirect UV detection in capillary electrophoresis

“…1D-F). These results thus suggested that the origin(s) of baseline fluctuations observed for C 16 was different than those induced mainly by factors that are thermal in nature [16].…”

“…In the present work, this jacket was removed to monitor the noise characteristics of various visualization agents and thus a nonuniform thermostating condition was purposely created along the capillary under this situation. Figures 1D-F show the effects of the variation in applied voltage and ionic strength of the BGE solution on baseline noise fluctuations when using a UV-absorbing cationic surfactant that possesses sixteen carbon atoms in the alkyl chain (C 16 : benzyldimethylhexadecylammonium chloride) as the visualization agent. It should be noted that the use of UV-absorbing cationic surfactants, such as C 16 , as CE buffer additives has been suggested as a promising approach for the indirect UV detection of UVinactive cationic surfactants with high sensitivity [17,18].…”

“…Using singly charged visualization agents such as picric acid, Poppe and co-workers [16] cited that baseline fluctuations (low-frequency noise that occurred with a frequency of 2-10/min) goes up rather regularly with an increase in current, irrespective whether the higher current is caused by a high voltage or by a high conductivity (ionic strength); also, when the conductivity is varied independently from the visualization agent concentration, the low-frequency noise is always largest at the highest conductivity. It is important to note that opposite trends were observed when using C 16 as the visualization agent, in which baseline fluctuations (higher frequency in nature) was dramatically reduced as a result of increasing the applied voltage (current) and/or conductivity (Figs. 1D-F).…”

“…This noise coefficient was found to be affected by the surface mod-ification of the capillaries, e.g., a dramatic reduction in noise was observed when using a coated capillary. Another insightful paper concerning the origin of noninstrumental noise was by the research work of Poppe and coworkers [16], who introduced the concept of "thermal nodes" to account for nondetector noise arisen from mostly Joule heat production and nonuniform thermostatting along the capillary, rather than to adsorption/desorption processes that occur within the capillary.…”

Signal Processing Methods for Capillary Electrophoresis

“…The high frequency noise is from the instrument/detector which results from ``incomplete grounding or from the signal amplification system'' (Kuhn and Hoffstetter-Kuhn 1993) or from other sources such as electronic components including the Analogue to Digital Converter (ADC) (Jacobsen 2007;Solis et al 2007;Xu et al 1997). The low frequency noise is mainly generated from temperature variations, impurities of the background electrolyte (`chemical noise') and air bubbles (Kuhn and Hoffstetter-Kuhn 1993;Xu et al 1997). The unsatisfactory sample injection could also contribute to the low frequency noise due to the background buffer solution variations.…”