High pressure liquid chromatograph

Assay of Endogenous NE. Endogenous NE release from the guinea pig vas deferens was measured by means of a high pressure-liquid chromatograph with an ODS column and an electrochemical detector as described previously (16). 

Figure 3. High pressure liquid chromatographic analysis of the urinary metabolites of 2 C N nitrosonornicotine in the rat after a dose of 300 mg/kg (31), Peaks...

Figure 5.1 Block diagram of a high pressure liquid chromatograph. Dotted lines refer to optional components.

Kreiser, W.R. and Martin, R.A. Jr., High pressure liquid chromatographic determination of theobromine and caffeine in cocoa and chocolate products, JAOAC, 61,1424,1978. 

Kreiser, W., Martin, R., Cacao products — high pressure liquid chromatographic determination of theobromine in cocoa and chocolate products, J. Assoc. Off. Anal. Chem., 61, 1424, 1978. 

The pharmacokinetics of rifaximin after oral administration has been studied in healthy volunteers and patients with intestinal infections or IBD. The aim of these studies was to confirm the low, if any, systemic absorption of the drug metabolism and excretion data are scant. In all these investigations a sensitive high-pressure liquid chromatographic (HPLC) method was used to measure rifaximin in body fluids. 

One approach that allows increased chromatographic flow rates without loss of resolution entails the use of microparticulate stationary-phase media of very narrow diameter. This effectively reduces the time required for molecules to diffuse in and out of the porous particles. Any reduction in particle diameter dramatically increases the pressure required to maintain a given flow rate. Such high flow rates may be achieved by utilizing high-pressure liquid chromatographic systems. By employing such methods, sample fractionation times may be reduced from hours to minutes. 

Molecular weight measurements were determined by size exclusion chromatography on a high pressure liquid chromatograph equipped with a differential refracto-meter. A Waters Styragel HR 5 i column set (106 104 500 A) was employed and calibrated with PS standards. THF was used as solvent at a flow rate of 1 ml/min. 

In order to obtain better and faster separation, instruments using higher pressures than common HPLC have been developed. These are often referred to as ultra-high-pressure liquid chromatographs (UPHPLC), or some similar abbreviation. They are used in a manner similar to HPLC and can be connected to mass spectrometers. 

High-pressure liquid chromatographic (HPLC) analysis performed with a chiral mobile phase (57,58) confirmed in all the conglomerate systems that the S inhibitors are selectively occluded only in the bulk of the S substrate crystals, typically in amounts of 0.5-1% (and, by symmetry, occlusion of R occurs only in R crystals). The selective adsorption causes, furthermore, a drastic decrease in the growth (and possibly nucleation) rate of the affected enantiomer, leading to efficient kinetic resolution various conglomerate systems have been resolved by this method (54). 

Spoms P. 1981. High pressure liquid chromatographic determination of phenol in honey. J Assoc Off Anal Chem 64 337-340. 

Hui, J. and Taylor, S.L. (1983). High pressure liquid chromatographic determination of putrefactive amines in foods, Journal AO AC, 66, 853. 

Sugars were estimated by using a Beckman 344 gradient high-pressure liquid chromatograph with an Altex 156 refractive index detector and a Spherogel 7.5% carbohydrate column with a flow rate of 0.5 ml/min in the mobile phase of water at 80 C. The sugar samples were appropriately diluted before injection. 

Juergens, U. 1981. High-pressure liquid chromatographic analysis of residues of drugs in honey. I. Tetracycline. Juergens, Uwe. Z. Lebensm.-Unters. Forsch., 173(5) 356-8. 

Because N-nitroso compounds can have such a wide variety of physical and chemical properties, and because they can be formed from a wide variety of precursors. analysis at the trace level is difficult. The most widely used technique is the use of a nitrosamine specific detector, called a TEA, which can be interfaced to either a gas chromatograph (GC) or a high pressure liquid chromatograph (HPLC) (31,32). General screening procedures which have been designed to detect all N-nitroso compounds have been developed (33,34). Structural confirmation of N-nitroso compounds is gen-... 

An improved high pressure liquid chromatographic (HPLC) procedure Tor the PSP toxins is described. The method involves separation of the toxins on a polystyrene divinylbenzene resin colunn (Hamilton, PRP-1) in the reversed phase mode using heptane and hexane sulfonic acids as ion-pairing reagents. Detection of the toxins is by fluorescence following post-column alkaline periodate oxidation. The sensitivity of the HPLC method is better than the standard mouse bioassay by at least a factor of four for each of the individual toxins. 

S. K. Henderson and A. F. Wickroski, In Application of High Pressure Liquid Chromatographic Methods for Determination of Fat Soluble Vitamins A, D, E, and iCin Foods and Pharmaceuticals, Symposium Proceedings Association of Vitamin Chemists Chicago, III. 1978, pp. 48-61. 

Hakes DC, Johnson GD, Marhevka JS. 1986. An improved high pressure liquid chromatographic method for the determination of isocyanates using nitro reagent. Am Ind Hyg Assoc J 47(3) 181-184. 

Two students, Denby and Scott, began their quest at the library with a computer search for analytical methods. Searching with the key words caffeine and "chocolate," they uncovered numerous articles in chemistry journals. Reports titled High Pressure Liquid Chromatographic Determination of Theobromine and Caffeine in Cocoa and Chocolate Products 5 described a procedure suitable for the equipment in their laboratory.6... 

It is for these reasons that a recommendation is made to avoid, wherever possible, concentration and cleanup steps that involve "column chromatography" of this nature, that is, chromatography where an in-line detector is not involved. This distinction is made to eliminate any implied criticism of instrumented high pressure liquid chromatographic systems which have not to date been used extensively for this particular purpose. 

A schematic diagram of a typical high-pressure liquid chromatograph is shown in Figure 3.12. The basic components are a solvent reservoir, high-pressure pump, packed column, detector, and recorder. A computer is used to control the process and to collect and analyze data. The similarities between a gas chromatograph and an HPLC are obvious. The tank of carrier gas in GC is replaced by the solvent reservoir and high-pressure pump in HPLC. 

WO Landen Jr, RR Eitenmiller. Application of gel permeation chromatography and nonaqueous reverse phase chromatography to high pressure liquid chromatographic determination of retinyl palmitate and /3-carotene in oil and margarine. J Assoc Off Anal Chem 62 283-289, 1979. 

DW Nierenberg, DC Lester. High pressure liquid chromatographic assays for retinol and beta-carotene potential problems and solutions. J Nutr Growth Cancer 3 215-225, 1986. 

EJ de Vries, J Zeeman, RJE Esser, B Borsje, FJ Mulder. Analysis of fat-soluble vitamins. XXI. High pressure liquid chromatographic assay methods for vitamin D in vitamin concentrates. J Assoc Off Anal Chem 62 129-135, 1979. 

S Oties, Y Hisil. High pressure liquid chromatographic analysis of water soluble vitamins in eggs. Ital J Food Sci 5 69-73, 1993. 

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