The uses of high-pressure liquid chromatography

Gupta and Shek reported on the use of high pressure liquid chromatography, ultraviolet spectrometry, and colorimetry as stability-... 

A portion (30.5 g) of the residue collected above was subjected to fractional distillation under reduced pressure (0.1-0.15 mm/Hg). The temperature was slowly raised to 125°C and the materials collected were kept separate. The temperature was then raised between 140°-160°C where the major fraction was collected (14 g). GC analysis showed >96% THC. Further purification on a silica gel column gives THC with at least 98% purity. An improvement of this process includes the use of high pressure liquid chromatography (HPLC). The preparation of dronabinol and related compounds have employed acid-catalyzed electrophilic condensation of a 5-alkylresorcinol such as 5-n-pentylresorcinol (commonly known as olivetol) and a menthadienol, followed by cyclization yield of desired product is about 17-22% (Petrzilka et al., Helv. Chim. Acta, 52, 1102 (1969)). 

Derivatives may also be used to m e the molecule capable of detection by selective detectors. The reaction may be carried out during extraction (e.g. extractive methylation), on the dry residue (e.g. silylation), or during injection (e.g. methylation). If a compound requires derivatisation in order to reduce its polarity, the use of high pressure liquid chromatography should be considered instead of GLC, assmning that sensitivity is not the limiting factor. 

The use of high pressure liquid chromatography enables many compounds to be studied which are not amenable to gas chromatographic analysis, for example those that are thermally labile. Eluent flow rates of between 0.5 and 2.0 ml/min are commonly used, whilst the maximum input the mass spectrometer can accommodate is about 1 to 4 ml/ min of gas at standard temperature and pressure (s.t.p.). Simple calculations show that 1 ml of liquid hexane gives 172ml of gas at s.t.p., 1 ml of chloroform gives 285 ml, 1 ml ofmethanol 550 ml, and 1 ml of water 1200 ml. In the low pressure... 

In order to overcome these undesirable effects of silica and to have a medium more suitable for the separation of a large variety of organic compounds, modification of the surface is necessary to provide a more nonpolar (hydrophobic) material. It is advantageous to retain silica as the primary material in the column because it possess physical and mechanical properties that make it particularly useful for modern liquid chromatography [i.e., the use of high-pressure liquid chromatography (HPLC) to force the mobile phase and sample through the system at a reasonable flow rate]. 

H5. Hartwick, R. A., and Brown, P. R., The use of high pressure liquid chromatography in clinical chemistry and biomedical research. Adv. Clin. Chem. 21, 25-99 (1980). 

The Use of High Pressure Liquid Chromatography in Clinical Chemistry and Biomedical Research... 

The use of high pressure liquid chromatography (HPLC) with fluorimetiic detection (FD) allows to separate and identify the isomer forms of type I and III uro- and coproporphyrins as metabolytes derived from the oxidation of the corresponding porphyrinogens, produced in the process of natural metaloporphyrin biosynthesis. With this aim, the application method described by Jacob et al. (1985) was used. 

In the last few years the GC/MS technique was improved by the use of high pressure liquid chromatography (HPLC) for sample work up (25) and by capillary gas chromatographic columns (21, 26). We would like to report about some of these improvements. 

THE USE OF HIGH PRESSURE LIQUID CHROMATOGRAPHY TO MONITOR NUCLEOTIDE LEVELS IN CELLS... 

---