Refractive index detectors fractionation

This is illustrated in Figure 2 for six ml of DFM. Fraction one, beginning at 3.2 min, is the saturate fraction which was detected with a refractive index detector. Fraction 2, indicated by slight absorption on the 254 nm uv detector, corresponds to the olefin fraction. The subsequent fractions, as indicated by the strong absorption on one or both of the uv detectors, are comprised of... 

Degassed and preswelled Bio-Gel P-6 and Sephacryl S-200 were packed in self-made glass columns (70 X 1.5 cm 140 X 1.5 cm) and equilibrated for 20 hr with H20(dest.) -t- 0.002% NaN3 to prevent microbial growth. The mass of eluted fractions was detected with a differential refractive index detector (Waters 403 RI, sensitivity 8). 

The molecular weight distribution of cell wall polysaccharides was estimated by gel filtration with a TOSOH TSK gel G4000 PWXL (7.8 x 300 mm) column equilibrated and eluted with 0.05 M sodium acetate, 0.01 M EDTA, 0.05 M NaCl (pH 5.0) in polyuronide and 0.05 M sodium citrate, 0.1 M NaCl (pH 5.5) in the hemicellulose fraction. Samples (1 mg/ml) of 100 ml were injected. The eluate was monitored by a refractive index detector (Shimadzu R1D-6A, Kyoto, Japan) and collected at the fraction size of 0.4 ml. 

Another variation of the preceding method is to apply HPLC to fractionate the cleaned-up aliphatic-aromatic fraction from flash colurim separation of soluble organic matter as it is performed in the Chevron laboratory, for example, as described in Reference 2. A Waters HPLC system equipped with a preparative Whatman Partisil 10 silica column (9.4 X 500 mm), a HPLC pump, and two detectors for separation monitoring (a UV and refractive index detector) are used, giving three fractions of aliphatic hydrocarbons, mono-, di-, and triaromatics and polar compounds. The hrst two fractions are eluted with hexane, whereas polar compounds are eluted with... 

Figure 8. Gel filtration of ethylated (/ -0-4)-(/ -/ )-DHP 16. Solid line Ethylated (/ -0-4)-(/ -/ )-DHP 16 after removal of low molecular weight fractions. The column was calibrated with (/ -0-4)-(/ -/ ) lignin substructure model trimer 6 (molecular weight 642) /3-0-4 lignin model dimer 1 (molecular weight 348) and polystyrenes of molecular weight 9000, 4000 (void), 2200 (indicated by A). Column Sephadex LH-20, 1.1 x 48 cm. Eluent DMF, 13.5-14.4 ml/hr. Detector Refractive index detector RI-2 (Japan Analytical Industry Co., Ltd.).

Molecular weight and polydispersity of the acetone extracted fractions from thermally degraded samples were determined by SEC with a Jasco PU-1580 HPLC pump equipped with two Pigel mixed D columns (Polymer Laboratories UK) connected in series, and a Jasco 830RI refractive index detector. Sample elution was with THF at 1 ml/minute flow rate. The instrument was calibrated with standard polystyrene samples. 

The differential refractive index detector response on the ordinate of the SEC chromatogram in Fig. 3-8 can be transformed into a weight fraction of total polymer while suitable calibration permits the translation of the elution volume axis into a logarithmic molecular weight scale. 

A uv or refractive index detector can also be incorporated into the stem, or the fractions can simply be analysed by tic, as for flash. "omatography. If the conditions are kept constant the results from mplc 133 very consistent, so if you wish to repeat separations of the same iixture, it is very easy to predict which fractions will contain each rmponent... 

Whilst the column is running, collect tics or use the detector to determine which fractions contain the required components. Unless you are using a refractive index detector, gradient elution is simply achieved by gradually adding more polar solvent to the reservoir. 

Fraction purity is guaranteed to a certain extent by the refractive index detector. If the peak of a UV-absorbing compound is partly overlapped by that of a nonabsorbing compound, the UV detector is unable to register this and the fraction obtained will not be pure. 

HPLC was performed with a liquid chromatograph (Waters Associates Series 6000) equipped with UV and refractive-index detectors. Asphaltene fractions were examined by using a 25- X 0.5-cm column packed with silica gel and maintained at 25 °C by an external thermostatically controlled water bath. Asphaltenes and standard polynuclear aromatic compounds were passed through the column with chloroform-isopropyl alcohol blends (90 10). 

In order to avoid the use of standards, multidetection SEC-HPLC systems incorporate, in addition to the refractive index detector, a multiple angle lasCT light scattraing (MALLS) detector. This enables the determination of the molecular weight and radius of gyration of the individual fractions as they elute out of the column, hence to obtain their distribution as a function of concentration. Multidetection HPSEC is undoubtedly the prefored technique for the analysis of the distribution of chitosan s molar masses and sizes [38, 52, 53]. 

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