Oscillometric flow cell for measurement of conductivity and permittivity

Abstract

We call into question the techniques in the literature which employ least-squares procedures to estimate the mole fractions of species believed to be present. The most serious difficulties with least squares is the lack of statistical independence in the random errors, failure of homoscedasticity, and exact linear dependencies in the observed data which give rise to a singular covariance matrix of the error vector.We applied the Bayesian formalisim of Box and Draper (7) to estimate the mole fractions, the approaches of McLean et al. ( 12) and Box et al. (7) to eliminate the linear dependencies in the observed data, and some approximations given by Stewart and Sorensen (13,14), and we were able to use formulas given by Box and Tiao (15) for a linear, single response model, to find approximate HPD contours and confidence intervals for the mole fractions. The Bayesian confidence intervals are narrower than those obtained from the leastsquares analysis.

Ten years of axial capacitively coupled contactless conductivity detection for CZE – a review

“…Although the use of the axial electrode arrangement was new for CE, it had previously been reported for other applications. One of the early protagonists of contactless conductivity measurements, Pungor, had proposed the use of external tubular electrodes for flow‐injection analysis (FIA) 20 and ion‐chromatography 21 and the authors of the CE‐C 4 D publications in 1998 were aware of these earlier reports.…”

Renaissance of HF Impedimetry in Application to CE Detection

“…This is permitted by high-frequency measurement of impedance (HF impedimetry) in which the electrodes are placed at the outside walls of the cell because the high-frequency current passes through the dielectric material of the wall (e.g., glass or fused silica). This measurement has been known for quite a long time (for surveys see [7,8]) but its practical application was rare, limited to indication in some titrations and several direct determinations, until a few recent years, because of two main reasons: -The mechanism of impedance measurement is complex and the dependences of the signal on the composition of the test system and on the experimental conditions are nonlinear and empirical to a considerable degree. -The measurement is universal, i.e., any change in the test system gives rise to a change in the measured signal.…”

Bioanalytical profile of the l-arginine/nitric oxide pathway and its evaluation by capillary electrophoresis

“…After a prototype of a contactless conductivity detector was designed for capillary ITP [301] and a theoretical treatment of contactless conductivity measurement was proposed [302,303], it became increasingly employed in HPLC and HPCE analyses [294]. Slightly different CCD techniques were proposed for HPCE in 1998 [304,305] and subsequently improved (for reviews see refs.…”