HPLC separation and determination of astacene,semiastacene, astaxanthin,and other keto-carotenoids

Direct HPLC analysis of astacene, semi-astacene, and astaxanthin isomers in the presence of other keto-carotenoids was achieved using silica gel coated with H₃PO₄. A method was developed for the preparation of such stationary phases with reproducible chromatographic properties.     

Liquid and gas chromatographic separation of isomeric methylated dibenzothiophenes

Trace amounts of a dibenzothiophene (DBT) series in complex matrices were detected by gas chromatography with flame photometric detection (FPD) after purification and isolation by normal-phase high performance liquid chromatography. The gas chromatographic behavior of eleven methylated DBTs was studied on six common stationary phases. Complete resolution of the four monomethyl DBT isomers was only achieved on a capillary column coated with a methylphenylsilicone phase gummified in situ by heat-curing. The determination of the relative distribution of the four monomethylated isomers is proposed as a powerful method for monitoring oil pollution in marine environment.     

The determination of serum retinol by high performance liquid chromatography

A method for the quantitation of retinol in serum by normal phase high performance liquid chromatography is described. The mobile phase consists of a hexane/diethylether/methanol mixture with spectrophotometric detection. The sample preparation is similar to that described by other authors and involves protein precipitation followed by extraction and direct injection onto the chromatograph. Adequate sensitivity is achieved using 200 μl samples. The internal standard chosen is α-naphthol because of its spectral similarities to retinol and its greater stability than the commonly used retinyl esters. The method has been successfully applied to the clinical evaluation of a number of malabsorption syndromes for which it is preferred to the measurement of total carotenoids.     

Quantitative determination of low concentrations of DHETX m. s. in human plasma by high performance liquid chromatography with fluorescence detection

A method is described for separation of low amounts of DHETX m. s. from human plasma, based on extraction and determination by high performance liquid chromatography with fluorimetric detection.     

The rapid quantitative determination of aromatic-type groups in gas oils by high-performance liquid chromatography

Summary A rapid method is described for the quantitative determination of aromatic-type groups in gas oil petroleum fractions. The method involves separation by high-performance liquid chromatography followed by detection with a differential refractometer, whose response to aromatic-type groups is more predictable than an ultra violet absorbance detector. A primary standard is used for calibration, and the precision and accuracy of the method have been investigated and are discussed.     

Validated reversed phase LC method for quantitative analysis of polymethoxyflavones in citrus peel extracts

Polymethoxyflavones (PMFs), which exist exclusively in the citrus genus, have biological activities including anti-inflammatory, anticarcinogenic, and antiatherogenic properties. A validated RPLC method was developed for quantitative analysis of six major PMFs, namely nobiletin, tangeretin, sinensetin, 5,6,7,4'-tetramethoxyflavone, 3,5,6,7,3',4'-hexamethoxyflavone, and 3,5,6,7,8,3',4'-heptamethoxyflavone. The polar embedded LC stationary phase was able to fully resolve the six analogues. The developed method was fully validated in terms of linearity, accuracy, precision, sensitivity, and system suitability. The LOD of the method was calculated as 0.15 microg/mL and the recovery rate was between 97.0 and 105.1%. This analytical method was successfully applied to quantify the individual PMFs in four commercially available citrus peel extracts (CPEs). Each extract shows significant difference in the PMF composition and concentration. This method may provide a simple, rapid, and reliable tool to help reveal the correlation between the bioactivity of the PMF extracts and the individual PMF content.     

High performance liquid chromatographic resolution of the optical isomers of D,L-tryptophane,D,L-5-hydroxytryptophan and D,L-dopa on cellulose columns

The application of HPLC for the purpose of separation of some amino acid racemates with aromatic substituents is described. Using simple untreated cellulose with an average particle size of 7 μm as stationary phase, complete resolution of D,L-tryptophane and D,L-5-hydroxytryptophane can be obtained. D,L-3,4-dihydroxyphenylalanine is resolved partially. The α-value and resolution for D,L-tryptophane was found to be 1.5.