Browsing by Author "Pai, Su-Cheng"

Now showing 1 - 4 of 4

Dispersion-convolution model for simulating peaks in a flow injection system
(2007-01-12)
Pai, Su-Cheng
;
Lai, Yee-Hwong
;
Chiao, Ling-Yun
;
Yu, Tiing
;
應用化學系
A dispersion-convolution model is proposed for simulating peak shapes in a single-line flow injection system. It is based on the assumption that an injected sample plug is expanded due to a "bulk" dispersion mechanism along the length coordinate, and that after traveling over a distance ora period of time. the sample zone will develop into a Gaussian-like distribution. This spatial pattern is further transformed to a temporal coordinate by a convolution process, and finally a temporal peak image is generated. The feasibility of the proposed model has been examined by experiments with various coil lengths, sample sizes and pumping rates. An empirical dispersion coefficient (D*) can be estimated by using the observed peak position. height and area (t(p)(*), h* and A(t)(*)) from a recorder. An empirical temporal shift ((Phi*) can be further approximated by (Phi* = D*/u(2), which becomes an important parameter in the restoration of experimental peaks. Also, the dispersion coefficient can be expressed as a second-order polynomial function of the pumping rate Q, for which D*(Q) =delta(0) + delta(1)Q+delta(2)Q(2). The optimal dispersion occurs at a pumping rate of Q(opt) = root delta(0)/delta(.)(2) This explains the interesting "Nike-swoosh" relationship between the peak height and pumping rate. The excellent coherence of theoretical and experimental peak shapes confirms that the temporal distortion effect is the dominating reason to explain the peak asymmetry in flow injection analysis. (c) 2006 Elsevier B.V. All rights reserved.
Examination of the temporal effect in a flow injection analysis system using multi-channel absorbance detection
(2009-05-22)
Lin, Shu-Hui
;
Chang, Kai-Chieh
;
Chen, Yu-Chun
;
Yu, Tiing
;
Pai, Su-Cheng
In addition to the Poiseuille effect, a so-called temporal effect was proposed recently to elucidate the commonly observed tailing peak signals of flow injection analysis (FIA). A multi-channel absorbance detector was used in this study to obtain the FIA peaks on both the spatial and temporal coordinates. The temporal effect was analyzed by comparison of the profiles between the experimental and the corresponding Gaussian peaks. and by comparison of asymmetry factors between the spatial and the temporal peaks. The temporal effect appeared to be the major factor under flow rates ranging from 0.5 to 8 ml min(-1). This was despite the presence of a spatially frontal peak observed in the FIA tubing, which was found to result in a tailing peak on the temporal coordinate due to this discussed cause. in addition, the temporal effect became greater as the flow rate increased. (C) 2009 Published by Elsevier B.V.
Interpretation on Band-broadening in Chromatography with Spatial Peak Profiles Obtained Using Whole-column Detection
(2009-06-01)
Lin, Shu-Hui
;
Yu, Tiing
;
Pai, Su-Cheng
;
應用化學系
;
Department of Applied Chemistry
Fifteen liquid chromatographic experiments were investigated using a whole-column detection (WCD) system and a conventional post-column UV/Vis detector. The peak widths obtained from chromatograms were found dependent on the retention factor; the larger the retention factor was the greater the peak width. However, the on-column spatial peak widths were dependent on the locations where they were measured in the column. The peak widths monitored at 17 cm from the column inlet were found essentially the same no matter what their retention factors were. In addition, a linear relationship was found between the chromatographic peak width and the reciprocal of the average linear rate of the solute migration. The peak widths on chromatograms did not reflect how they appeared in the column; instead, the widths were determined by the solute speed passing the detector.
Peak crossover in high-performance liquid chromatography elution monitored using whole-column detection
(2008-08-01)
Lin, Shu-Hui
;
Yu, Tiing
;
Sheu, Alf
;
Yang, Der-Jyh
;
Pai, Su-Cheng
A whole-column detection (WCD) system was fabricated using the parts from a typical A4 size optical scanner. Optimum layout of the fluorescence tube, beam condenser and photon transducers from the scanner made an effective devise to examine the dynamic chromatographic separation process. This system was applied in monitoring peak crossover in an ion-pair chromatographic elution. A stage-wise gradient was conducted in eluting a mixture of New Coccine and Carmoisine. Compound New Coccine lagging behind after sample injection moved passing Carmoisine at the column outlet. The complete on-column elution process could be observed directly using this detection system. This inexpensive and rugged WCD system provided a 0.3 mm spatial resolution and a 3.6 ms temporal resolution and was proven to be an adequate device to directly monitor solute retention behavior in the liquid chromatography column. (c) 2008 Elsevier B.V. All rights reserved.