Refractometers detectors

Figure 1 The gel-chromatogram of the obtained product from the alkylation reaction of toluene with EC under various reaction conditions T, K = 273 (1), 293 (2), 313 (3), 333 (4). The ratio of toluene epichlorohydrin 0.5 1 (5) 1 1 (6), 2 1 (7), and 5 1 (8). (-) refractometer detector (—) UV-detector.

Hie hydrolytic depolymerization of nylon-6 was followed by gel permeation chromatography (GPC), viscometry, and gravimetry. GPC determinations were performed on a Waters 150C chromatography system using benzyl alcohol as die eluant, two Plgel 10-p.m crosslinked polystyrene columns, and a differential refractometer detector. The flow rate was 1 mL/min. The concentration of the polymer solutions was 0.5 wt% and dissolution was accomplished at 130°C. 

An ultraviolet absorption detector was used In tandem with a differential refractometer detector to obtain chemical composition data (3, 5 6). 

Ability to analyze unreacted monomers was dependent on detector selectivity. The UV detector was operated at 254 nm for analysis of AN/S latex solutions. Styrene is a strong UV abosrber at this wavelength while acrylonitrile has no measurable absorbance at 254 nm. Thus, the UV detector was entirely selective to monomeric styrene. The refractometer detector was sensitive to both acrylonitrile and styrene when each was present in the desired copolymer proportions (70/30). However,... 

Similarly, estimation of chemical composition of soluble polymer was also dependent on selectivity of the UV detector. Polymerized acrylonitrile has no significant UV absorbance at 230 and 254 nm. Thus, UV chromatograms were used to estimate amounts of polymerized methylacrylate and styrene In each resin system. The refractometer detector was sensitive to polymerized methylacrylate and styrene, as well as to polymerized acrylonitrile. It was therefore necessary to calculate comonomer contribution to refractometer peak areas In order to estimate concentration of polymerized acrylonitrile. This was done by obtaining a refractometer calibration for all three homopolymers. Quantity of polymerized comonomers measured by UV were then converted to equivalent refractometer peak areas. Peak areas due to polymerized acrylonitrile were then calculated by difference, and used to calculate amount of polymerized acrylonitrile. 

All three monomers were soluble In the chromatographic mobile phase and standard analytical techniques were used for calibration. Solutions containing known quantities of monomer were chromatographed to establish a peak area concentration relationship for the appropriate detector. The homopolymer of methylacrylate was also soluble In the mobile phase. Thus, both UV and refractometer detectors were calibrated for polymerized methylmethacrylate by chromatographing solutions of PM ... 

Figure 2. Chromatograms of AN/MA graft polymer (differential refractometer detector (a) 7% total solids (b) 11% total solids (c) 27% total solids)...

Colin, H., Jaulmes, A. Guichon, G., Corno, J., and Simon, J, Construction and performance of an improved differential refractometer detector for liquid chromatography, J. Chromatogr. Sci., 17, 485, 1979. 

Temperature control is important for the accurate measurement of retention data, and has to be used with refractometer detectors (Section 2.4.5). Increasing the temperature can increase the speed of the separation, especially in exclusion chromatography, and usually increases the efficiency of the column (though the gain in efficiency can be lost if the mobile phase is not properly equilibrated). Complicated separations can often be optimised by increasing the temperature, but this is done very much on a trial and error basis, and most work in hplc is still done without temperature control. 

Temperature In reality, the maintenance of strict temperature control plays a vital role in measuring the retention-data correctly and precisely. It makes use of the refractometer detectors specifically. In HPLC, difficult separations may be achieved by increasing the temperature carefully, but this must be done initially on a hit and trial basis. 

High Molecular Weight Polymers in Cyclohexane and also in Special Column Arrangements. Waters Associates Ana-Prep and 501 GPC were used. One four-foot Styragel column of 5x10 pore size was connected to a pump and a differential refractometer detector to determine the effect of fritted discs on degradation. 

Gel Permeation Chromatography (GPC). Waters Associate Model 200 GPC was used with 4 x 3/8" styragel columns with an internal diameter of 0.311" and refractometer detector. The basic characteristics and operation of the instrument have been previously described in detail (19-20). Some of the operating conditions used in this study are outlined below. 

When characterizing copolymers, it is necessary to have two detectors in series, e.g., a refractometer with either a UV detector or an IR detector. An IR detector is preferred for the detection of polyalkenes at elevated temperatures because baseline noise and drift are much less than for the refractometer detector. 

Use of the differential refractometer detector is applicable to all polymers having refractive indices different from that of the solvent. However, a correction must be made if the polymer refractive index depends on molecular size, such as at very low molecular weights. 

Liquid chromatographs are equipped with a means to continuously monitor the column effluent and recognize the presence of solute. Only small sample sizes are used with most HPLC columns, so a detector must have high sensitivity. The type of detector that has the most universal application is the differential refiractometer. This device continuously monitors the refractive index difference between the mobile phase (pure solvent) and the mobile phase containing sample (column effluent). The sensitivity of this detector is on the order of 0.1 ju,g, which, compared to other detectors, is only moderately sensitive. The major advantage of the refractometer detector is its versatility its main limitation is that there must be at least 10 7 refractive index units between the mobile phase and sample. 

Detector Compatibility A solvent must be carefully chosen to avoid interference with the detector. Most UV detectors monitor the column effluent at 254 nm. Any UV-absorbing solvent, such as benzene or olefins, would be unacceptable because of high background. Since refractometer detectors monitor the difference in refractive index between solvent and column effluent, a greater difference leads to greater ability to detect the solute. 

Sugar and polyols in aqueous media were analyzed by HPLC. (column, sugar pack waters eluant H O flow rate 0.5 ml/min. temperature 90°C differential refractometer detector). 

Differential refractometer detectors are used in preparative separations of peptides, though not in the analytical separations themselves, because of their low sensitivity. 

Chromatographic System Determine as directed under Chromatography, Appendix HA, but use a liquid chromatograph equipped with a differential refractometer detector and a 30-cm x 7.8-mm (id) column packed with 25-pm diameter beads of silver bonded to sulfonated divinyl benzene-styrene copolymer (Aminex HPX-42A, Bio-Rad Laboratories, or equivalent). Maintain the column at a constant temperature of 65° 10°, and the flow rate at 0.3 to 1.0 mL/min. Use deionized water as the mobile phase. 

Apparatus (See Chromatography, Appendix IIA.) Use a suitable high-performance liquid chromatography system such as described in Standard Analytical Methods of the Corn Refiners Association, equipped with a 22- to 31-cm stainless-steel column, or equivalent, a strip-chart recorder, and a differential refractometer detector maintained at 45° 0.005°. 

Differential refractometer detectors measure the difference between the refractive index of the mobile phase alone and that of the mobile phase containing chromatographed compounds as it emerges from the column. Refractive index detectors are used to detect non-UV absorbing compounds, but they are less sensitive than UV detectors. They are sensitive to small changes in solvent composition, flow rate, and temperature, so that a reference column may be required to obtain a satisfactory baseline. 

Apparatus Use a suitable high-performance liquid chromatographic system (see Chromatography, Appendix HA) equipped with a differential refractometer detector, a precol-... 

A high performance liquid chromatograph (Dionex CHROMELEON) fitted with an isocratic pump, an auto-sampler, an UV detector and a refractometer detector was used to analyze quantitatively the reaction products at the outlet of the anode side of the DEFC. 

Two different columns were used according to the products to be analyzed. For AA and COs " analysis an HPX-87H column was used with an eluent (0.01 M H2SO4 solution) flow of 0.6 mL min. For the hydrazone derivative of AAL analysis, a CI8-NH2 column was used with an eluent (CH3CN/H2O 60 40) flow at 0.6 mL min. AAL and AA can be detected by the UV detector at a wavelength of 240 mu as well as by the refractometer detector, whereas COs " was only detected using the refractometer. 

The Optilab Interference Refractometer Detector Courtesy of Wyatt Technology... 

Molecular Weight Determination. Molecular weights were determined using a Waters Model 200 gel permeation chromatograph equipped with a modified Waters R4 differential refractometer detector. The solvent was THF the flow was 2.0 mm /min. The column, 25 cm x 7.8 mm ID, consisted of 10 , 10 , 10, 10 , 10 A° waters microstyragel. 

Sugars. The high performance liquid chromatography (HPLC) method described by Hunt et al. (8) was used to determine the sugars in the kiwifruit and nectars with some modifications (21). A Waters Association Chromatograph equipped with a Model 6000-A solvent delivery system, a Model R401 refractometer detector, a D6K universal injector column was a 30 cm x 4 mm i.d. stainless steel tube packed with u-bondapak-carbohydrate (Waters Associates). The precolumn was packed with CO-PELL PAC (Whatman). The eluent was acetonitril and distilled water (85/15, v/v). 

Lactose, lactic acid, and acetic acid were determined by high-performance liquid chromatography (Waters, Milford, MA) with a KC-811 ion exclusion column and a Waters 410 differential refractometer detector. The mobile phase was 0.1% H3PO4 solution at a flow rate of 1 mL/min. The temperatures of the detector and of the column were maintained... 

Refractive index, for use with differential refractometer detectors. v ... 

Figure 6.26 Deflection refractometer detector. (Reproduced with permission of Waters.)...

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