Quantitative analysis of thiols in consumer products on a microfluidic CE chip with fluorescence detection

Abstract

A microchip CE-based method for the quantification of the thiols mercaptoethanoic acid (MAA) and 2-mercaptopropionic acid (2-MPA) in depilatory cream and cold wave lotions was developed. The thiols were first derivatized with the fluorogenic reagent ammonium-7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD-F). The derivatives were separated within only 20 s by microchip CE and detected by their fluorescence. Conventional CE with diode array detection and LC with fluorescence detection were used for validation. The internal standard 3-mercaptopropionic acid (3-MPA) provided RSDs of multiple injections of only 4% or less for the MCE approach. LOD is 2 mM, LOQ 6 mM, and the linear range comprises nearly three decades of concentration starting at the LOQ.

Optofluidic integration for microanalysis

“…Peaks in the elution spectra could be assigned to different pure analytes and unexpected impurities were detected both by CE separation and within an elution peak using spectral information. Using similar apparatus the group were then able to detect thiols found in cosmetics with an LoD of 2 lM (Revermann et al 2007) and taurine found in drinks with concentrations as low as 60 aM (Götz et al 2007c). Mitra et al (2006) fabricated a microdischarge device stacked on top of a microfluidic device as an alternative excitation light source producing emission in the UV for intrinsic fluorescence excitation.…”

Capillary electrophoresis in the analysis of biologically important thiols

“… derivatized both reduced and oxidized GSH in blood plasma and tobacco leave extracts using NBD‐Cl and separated them in 20 mM borate, 4 mM beta‐CD at pH 9.25 reaching LODs of 46 and 11 nM for GSH and GSSG. Ammonium‐7‐fluorobenzo‐2‐oxa‐1,3‐diazole‐4‐sulfonate is a modified molecule that is highly water soluble (due to the sulfonyl group) and easily amenable to CE that could be used for separation of NAC, though the primary compounds to be analyzed were mercaptoethanoic acid and 2‐mercaptopropionic acid.…”

Chip‐mass spectrometry for glycomic studies

“…The advent in microfluidic technology offers a possibility of fast inter-channels changeable flow, by means of adjusting the electrical potentials at the channel termini. Basically, they operate as miniaturized CE instruments, exploiting the electroosmotic field generated under an applied electrical field to drive the fluid and the separated components through the microchannel (Sung, Makamba, & Chen, 2005;Revermann, Gotz, & Karst, 2007). Essentially, the electrophoresis performance in such device is not compromised, permitting a highly efficient separation of various components, while substantially decreasing the analysis time and increasing the sensitivity Sung, Makamba, & Chen, 2005;Dahlin et al, 2005b;Huang, Chen, & Lee, 2007;Revermann, Gotz, & Karst, 2007).…”