The direct introduction of supercritical fluid chromatography effluent from a packed DeltaBond 300 phenyl column with the MIP as an elemental detector, using a high efficiency TM010 cavity, has been employed for SFC separations. A toroidal plasma is sustained in the cavity by using an ICP type torch and an argon auxiliary flow (2 L/min) over all pressures (1500–5000 psi). Methanol modifier concentrations (0–5%) have also been studied. Studies of the effects of CO2 on excitation temperature, electron number density, and analyte emission signals are presented. In addition, the background broad-band emission signal with 100% CO2 and a methanol modifier up to 5% are presented.
The use of a highly efficient microwave-induced plasma as an element-selective detector for packed column supercritical fluid chromatography is discussed. The cavity is able t o support an Ar or He discharge at powers of 150 W or less. The effects of the introduction of supercritical C 0 2 on the analytical parameters of the plasma are described and minimum detectable quantity values for S, P and CI are presented.
A packed-column supercritical fluid Chromatograph (SFC) was coupled to an argon high-efficiency microwave-induced plasma (Ar-HEMIP) for the purpose of elemental detection of the chromatographic effluent. Two methods of sample introduction of the effluent into the argon plasma are presented for this hyphenated technique. The results of central introduction vs. sidearm introduction of SFC effluent into the Ar-HEMIP are evaluated according to analytical parameters such as: repeatability, the effects of pressure programming of 100% CO2 and modified CO2 on background emission, linear dynamic range (LDR), and minimum detectable quantity (MDQ) of several organometallic compounds. Sidearm introduction is found to be superior to central introduction in terms of these analytical parameters.
The performance of several mathematical approaches for quantification of components in cases of severe chromatographic and spectroscopic overlap has been investigated. The problem under consideration was the separation of two amino acids, glycine and glutamine, on high-performance thin-layer chromatographic plates, followed by derivatiration with o-phthaidiaidehyde. The chromatographic characteristics of these two amlno acids are very similar, and the fluorescence responses of the two derivatives are very similar as well. Here, five approaches, based on two data analysis methods, factor analysis and Kaiman filtering, have been studied. Each approach was able to detect the presence of the two amino acids in a mixture chromatogram, and the resolved responses showed a peak-shaped morphology. The concentration estimates were within an order of magnitude of the correct values, with the results for the derivativeadaptive Kaiman filtering approach showing the smallest errors, 5.9% error for glycine and -6.4% for glutamine.In the past several years, mathematical and statistical tools have been used increasingly to enhance the analysis of chemical data. In particular, several methods have been developed for the resolution of overlapped responses, which can arise in chromatographic and spectroscopic methods of analysis. In many cases, chromatographic methods can be coupled with multiwavelength spectroscopic detection approaches to enhance the analyst's ability to distinguish a number of coeluting components. Two classes of curve resolution approaches have been employed those that require a model for the spectral or chromatographic characteristics and those that are "self-modeling". The model-based curve resolution approaches are most useful for determining the relative contributions of each of the coeluting components to the overall spectroscopic response in cases where the identities of the contributing chemical species are known. These approaches include factor analysis methods ( l ) , linear leastsquares methods (2,3), modified least-squares approaches (4, 5), and Kalman filtering techniques (6, 7). One major requirement for successful implementation of all of these techniques is that the responses due to each of the components must be linearly independent of one another. This requirement means that inaccurate concentration estimates may be obtained for compounds that cannot be resolved chromatographically and that give rise to very similar spectral responses.One area where severely overlapped chromatographic and spectroscopic responses may cause difficulties in obtaining accurate concentration estimates is when derivatization methods are employed in chromatography to increase the detection sensitivity. In particular, fluorogenic reagents are often used to form fluorescent molecules from nonfluorescent Present address:analytes. The spectroscopic characteristics of these fluorescent derivatives are usually very similar, due to the fact that the energy levels in the fluorescent moiety are not substantially perturbed by th...
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