Separation Of Major Components Research Articles

Analysis of wax esters in seven commercial waxes using C30 reverse phase HPLC

Commercial waxes are difficult to analyze due to their limited solubility in most organic solvents. Recently, our laboratory published a new reverse phase HPLC-MS method using a C30 column, a gradient of methanol and chloroform, an evaporative light-scattering detector (ELSD), and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) to analyze jojoba wax (jojoba oil), carnauba wax, and sorghum wax. In the current study, the published HPLC method was modified by reducing the solvent gradient program to 60 minutes and this new method was evaluated for its usefulness for the analysis of five other commercial waxes (beeswax, rice bran, sunflower, candelilla and paraffin waxes). The ELSD appeared to detect all types of wax components, whereas the APCI-MS was most useful for the identification of wax esters and was unable to detect hydrocarbons, such as those in candelilla wax and paraffin wax. Previous HPLC methods for waxes and most GC methods for waxes only separate wax esters with size up to 54 carbons (C54) but this method was able to separate those with size up to 60 carbon wax esters. This report presents the first HPLC chromatograms for rice bran, sunflower, candelilla, and paraffin waxes. The main contribution of this work is the evidence that a C30 reverse phase HPLC system provides acceptable chromatographic separation of major components in commercial waxes.

Magnetic resonance imaging based determination of body compartments with the versatile, interactive sparse sampling (VISS) method

To investigate the inhomogeneity of radiofrequency fields at higher field strengths that can interfere with established volumetric methods, in particular for the determination of visceral (VAT) and subcutaneous adipose tissue (SCAT). A versatile, interactive sparse sampling (VISS) method is proposed to determine VAT, SCAT, and also total body volume (TBV). VISS is based on a separation of major components by contour lines, followed by a sparse sampling algorithm, and eventually a quick manual correction. T1-weighted whole body scans of 24 subjects were evaluated (12 at 1.5T, 12 at 3.0T). (a) Coefficients of variance (CV) and intra class correlation coefficients (ICC) determined within 3 raters (24 subjects) showed high consistency for SCAT (CV 2.2%, ICC 0.993) and VAT (CV 4.9%, ICC 0.987), (b) comparison with an established volumetric method revealed good agreement (Bland-Altman, VAT -0.68L to 1.07L, SCAT -2.18L to 8.39L), and (c) comparison of weights calculated from TBV with values measured on a scale resulted in an even better accuracy for VISS (Bland-Altman -1.98 kg to 4.09 kg) than for the reference method (-5.60 kg to 1.60 kg). VISS is reproducible in particular within the same rater, accurate as compared with established methods, and robust against low contrast and inhomogeneity artifacts.

Determination of rare earths in monazite sand and rare-earth impurities in high-purity rare-earth oxides by high-performance liquid chromatography

Using high-performance liquid chromatography it has been possible to separate 14 lanthanide elements in less than 40 min by elution with an α-hydroxyisobutyric acid concentration gradient. LiChrosorb KAT cation exchanger (10 µm) is used as the packing material and the eluted lanthanides are detected with an ultraviolet detector after complexation with Arsenazo III. The detection limit is about 0.1 µg.Determinations of the rare-earth composition in monazite sand and rare-earth impurities in high-purity lanthanum(III), cerium(IV), samarium(III) and yttrium(III) oxides were carried out. The proposed method is more convenient than others, and the separation of major components is not necessary in analyses of high-purity rare earths; the elution time is only about 1 h.

Separation of major components in licorice using high-performance liquid chromatography

Separation of major components in licorice using high-performance liquid chromatography