Rapid characterization of linear and star-branched polymers by concentration gradient detection

Flow dependence and sensitivity of the refractive index gradient measurement with the Z-configuration flow cell at low Reynolds number

“…The direct mea- surement method using a PSD is now preferred, since the data are more reliable and useful. Furthermore, in our application papers (15)(16)(17) the relationship of the probe beam to the flow cell may be misleading. The work presented in this paper will aim to clarify any ambiguity in our previous reports.…”

“…First, the deflected probe beam can be measured by an interferometric transduction mechanism at a simple photodiode detector. This was the basis of the RIG detector that was reported by Hancock and Synovec (15,16), although recognition of the radial concentration gradient was not made in this initial work. Second, the deflected probe beam can be measured more directly by using a position-sensitive detector (PSD) that provides absolute angular deflection data (17).…”

“…With the Z-configuration flow cell, at suitably low Reynolds number, a Poiseuille flow (20,21) appears to exist that produces a sharp radial concentration gradient in the presence of an axial concentration gradient. When measuring the radial concentration gradient directly (15)(16)(17), one is actually measuring the axial concentration gradient indirectly, since the existence of the radial concentration gradient requires an axial concentration gradient (1). The reliability of the radial concentration gradient measurement with the Z-configuration flow cell will be addressed in this report.…”

Optical beam deflection approach for studying ion-exchange reactions occurring at a single ion-exchange resin particle

“…On the other hand, the OBD method has also been applied for exploring a concentration gradient [15][16][17][18][19] in chemical and electrochemical systems. The OBD method also can be used for exploring a concentration gradient in flow systems [20][21][22]. Recently, we have explored chemical reaction heat-induced OBD and concentration gradient-induced OBD in chemical reactions in aqueous solution [23][24][25][26][27][28][29][30].…”

Capillary zone electrophoresis with analyte velocity modulation. Application to refractive index detection

“…These devices produce a first-derivative response. A recent variant on this design by Synovec (18,24) and a dual differential design by Pawliszyn (23) can measure refractive index differences of (2-5) X 8 RI unit. While these devices perform well, they are inherently limited to refractive index detection, or where a second laser at a suitable wavelength is available for absorbance detection via photothermal beam deflection (25).…”