Capillary Scale Reagent Introduction And Optical Detectors For Capillary Scale Analysis

Abstract

Atmospheric aerosols are of great interest as they have the potential to perturb the earth's radiative energy balance, influence the climate, reduce visibility, and adversely affect human health. The composition of atmospheric particulate matter, especially the concentrations of metals and their ratios, provide insights into sources of the aerosol. Capillary scale ion chromatography systems have several advantages over conventional chromatographic analysis systems like low reagent consumption, small sample requirement, higher efficiencies and better absolute mass detection limits. Hence, to achieve source identification and source apportionment, optical detector based capillary ion chromatography systems are proposed to perform qualitative and quantitative analysis of metal ions in a continuous fashion. Optical absorption detection is the most common mode of detection in analytical chemistry and chromatography. A simple, economical, versatile, light emitting diode based capillary scale multi-reflection absorbance detector was investigated. The detector performance is better than commercial absorbance detectors and the fabrication cost for the detector is a small fraction of the cost of commercial absorbance detectors.The sensitivity of fluorescence detection is often much better than that of absorbance detection. A capillary ion chromatography compatible, simple, versatile, liquid-core waveguide-based fluorescence detector was developed. A commercially available Teflon® AF coated fused silica capillary was used as a liquid core waveguide detection cell; this was transversely excited. Very high detection sensitivities (low picomol to low femtomol level detection limits) were achieved with very good reproducibility.Postcolumn reagent addition is a very common technique utilized in liquid/ion chromatography because the detection selectivity and sensitivity can be increased considerably thanks to the derivatization reaction. A capillary scale, low volume, dilutionless, pulseless, electrodialytic reagent introduction device was investigated for large ionizable ligands such as 2-(4-pyridyl azo) resorcinol that can form intensely colored metal chelates. The electrodialysis current is easily controlled and governs the amount of reagent introduced.