Microbore liquid chromatography and refractive index gradient detection of low-nanogram and low-ppm quantities of carbohydrates

Hancock, Darrell O.; Synovec, Robert E.

doi:10.1016/s0021-9673(00)94225-0

Cited by 21 publications

(12 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 2 shows the schematic diagram for the model, where light is transmitted from the entrance fiber through a solvent of refractive index ns and collected by the exit fiber. In the absence of absorbance, a change in refractive index of the solvent changes the divergence cone of both the entrance and exit fibers, thereby changing the light flux received by the exit fiber, resulting in a changing baseline for slow refractive index changes (19,20) or a substantial baseline disturbance for sharp refractive index changes such as injection disturbances (21,22). For a single wavelength, the relative collected light flux (RCLF) is the amount of light transmitted across the flow cell for a given solvent, relative to a reference solvent, i.e., relative to a stable baseline in a flowing system such as LC or SFC, and is given by (26) RCLF = /,//", = (n2 -N.A.2)/(nref2 -N.A.2) (4) where /8 and /ref are the photocurrents generated by the transmitted light for the solvent and reference solvent, respectively, ns and nie{ are the refractive index of the solvent and reference solvent, and N.A.…”

Section: Theorymentioning

confidence: 99%

“…An issue recently addressed by Synovec (19) and McGuffin (20) is the effect of refractive index on aperture-limited absorbance measurements. The effect is commonly manifested as an "injection disturbance" for sharp refractive index profiles (21,22) or baseline drift for MPG-LC (2). The implication of RI aberrations to absorbance measurements with TG-LC is also manifested in a drifting baseline.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal gradient microbore liquid chromatography with dual-wavelength absorbance detection

Renn¹,

Synovec²

1991

Anal. Chem.

Self Cite

View full text Add to dashboard Cite

and consequently that this process (which may involve the formation of carbon-carbon double bonds or of cross-linking between the polymer chains) or a similar one might be more common in the case of ion bombardment than in the case of atom bombardment. The exaggerated difference in time dependence behavior for ion beams, as compared to atom beams, observed for PTFE, as compared to PET, certainly suggests that particle-surface electronic interactions are a major contributor to this preferential sputtering of fluorine. CONCLUSIONSComparison of spectral time-dependence behavior for PET and PTFE has provided data concerning the nature of polymer degradation during particle bombardment. In particular, electronic particle-surface interactions have been shown to be a key contributing factor to degradation. In PET, this degradation is by straightforward physical degradation (random segmentation of polymer chains), which is accelerated by the use of charged primary particles. For PTFE, in addition to this process, an additional chemical degradation mechanism operates, which is, to a large extent, the consequence of electronic particle-surface interactions. This involves the preferential sputtering of fluorine and is manifested by the observation of a rise in peaks with a low fluorine to carbon ratio. At doses less than 1013 particles cmV2, this degradation mechanism may be nearly eliminated by the use of primary neutral particles rather than charged particles.Theoretical relationships are derived relating changes in the refractive index of the mobile phase in liquid chromatography to aperture limited absorbance measurements as applled to a single fiber-optic two-wavelength detector. The detection system was designed for remote sensing in thermal gradient microbore liquid chromatography (TG-pLC). TG-pLC was demonstrated with a reversed-phase separation of an unleaded gasoline sample for a temperature gradient of 25-150 OC over 30 min. The unique two-wavelength difference detection method, along with the single fiber-optic construction, virtually eliminated baseline drift associated with thermal Induced refractlve index ( R I ) aberrations. The detector provides a solution to R I aberrations not only for TEMLC but also for mobile-phase gradient liquid chromatography (MPG-LC) and other flow methods such as flow injection analyds (FIA). The advantages of TG-pLC are presented, including gradient separation capability for MLC, effective control of retention tlme comparable to MPG-LC, and separation efflclency over 72 000 theoretical plates/m using 5-pm packing material.

show abstract

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal gradient microbore liquid chromatography with dual-wavelength absorbance detection

Renn¹,

Synovec²

1991

Anal. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

“…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.…”

Section: Introductionmentioning

confidence: 95%

“…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). Thus, the principle of operation for the RIG detector will seem quite different depending upon whether an interferometric transduction mechanism (15,16) or a direct beam position detection mechanism ( 17) is used.…”

Section: Introductionmentioning

confidence: 99%

“…The work presented in this paper will aim to clarify any ambiguity in our previous reports. There was difficulty in quantitatively comparing the results of Hancock and Synovec (17) to the results of Pawliszyn, who pioneered the development of the sensitive RIG detector for FIA and HPLC (18,19). It was the difficulty in making a quantitative comparison between available theory and experimental evidence that suggested a more thorough understanding of the hydrodynamic behavior in the Z-configuration flow cell would be useful.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Hancock¹,

Renn²,

Synovec³

1990

Anal. Chem.

Self Cite

View full text Add to dashboard Cite

A simple model based upon Polseullle flow Is reported that allows the prediction of the sensitivity In the refractive Index gradient (RIG) measurement with the Z-conflguratlon flow cell. The RIG measurement Is shown to depend upon carefully probing the radial-concentration gradient (orthogonal to the direction of flow) of an ahalyte. A fiber optic graded refractive Index (GRIN) lens combination provided a narrow collimated beam that facilitated accurate probing of the RIG and far-fleld observation of the beam deflection, for subsequent comparison to the position-sensitive detector output. The flow rate range Investigated was at a low Reynolds number, Re < 10 In the cylindrical flow cell bore. Both the predicted and experimental measured RIG data are directly proportional to linear flow velocity and Inversely proportional to both the axial length variance of the analyte concentration and the analyte translational diffusion coefficient. The linear flow velocity and axial length variance dependence on RIG sensitivity were examined, and the model was found to closely predict the experimentally observed RIG sensitivity. Band-broadening contributions In the RIG detector are critically accounted for In the calculations. Measuring the radial concentration gradient was found to be over 2 orders of magnitude more sensitive than measuring the axial concentration gradient of a typical analyte peak for microbore liquid chromatography conditions.

show abstract

An o-toluidine method for detection of carbohydrates in protein hydrolysates

Morçöl

Velander

1991

Analytical Biochemistry

View full text Add to dashboard Cite

Microbore liquid chromatography and refractive index gradient detection of low-nanogram and low-ppm quantities of carbohydrates

Cited by 21 publications

References 38 publications

Thermal gradient microbore liquid chromatography with dual-wavelength absorbance detection

Thermal gradient microbore liquid chromatography with dual-wavelength absorbance detection

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

An o-toluidine method for detection of carbohydrates in protein hydrolysates

Contact Info

Product

Resources

About