Examination of the automated solute-independent calibration technique

Temperature‐programmed microcolumn liquid chromatography/mass spectrometry

“…For example, Okada [l] used temperatureprogrammed LC in combination with UV-absorbance, refractive index, and conductimetric detectors for the analysis of polyoxyethylene oligomers. Renn and Synovec [2] employed temperatureprogrammed LC with dual-wavelength UV-absorbance detection and reported a reduction of baseline shift compared to traditional single-wavelength measurements. Biggs and Fetzer [3] demonstrated the advantage of temperature-programmed LC with inductively coupled plasma emission spectroscopy for the element-specific detection of sulfur and silicon.…”

“…Such theoretical studies have been complicated by the presence of radial and axial thermal gradients in large diameter columns 19,101 and by the use of nonlinear or even exponential temperature programs [1,2]. In addition, if the system is maintained at constant pressure rather than constant flow rate, an increase in temperature causes a decrease in mobile-phase viscosity and, hence, an increase in flow rate.…”

“…Finally, the lack of commercially available instrumentation with the appropriate range of operating characteristics as well as the requisite accuracy and precision in temperature control has hindered the conduct of theoretical studies. The goals of the present study are as follows: (1) to develop a temperature-programmed LC/MS system that addresses the problems mentioned previously, (2) to develop a theoretical approach to predict and optimize solute retention under temperature-programmed conditions, and (3) to demonstrate the advantages of temperatureprogrammed LC/MS by practical application of this technique to the determination of fatty acids in fish oil dietary supplements.…”

Two-dimensional conductometric detection in ion chromatography. Postsuppressor conversion of eluite acids to a base

“…1 Present address: Eichrom Industries, 8205 S. Cass Ave, Suite 107, Darien, IL 60559. have also been presented in order to understand the effect of various parameters on the band shape, such as the sample size, the displacer concentration, and the column length {4-6). Mass-transfer effects in displacement chromatography have also been presented (7,8).…”

“…Wilson et al (6) utilized separate sequential single-column IC determination of the same sample with two different eluents, enabling them to assess the ionic mobility of the individual eluites and permitting solute-independent calibration. This technique was explored subsequently in more detail by Renn and Synovec (7) who also simplified the approach by using simultaneous injection into two independent chromatographic systems. An implicit requirement of these techniques is that the eluite anion be ionized to the same extent in the two eluent systems.…”