High-pressure liquid chromatography mobile phase

WH Schaefer, F Dixon Jr. Effect of high-performance liquid chromatography mobile phase components on sensitivity in negative atmospheric pressure chemical ionization liquid chromatography-mass spectrometry. J Am Soc Mass Spectrom 7 1059—1069,1996. 

Schaefer, W.H. Dixon, F. Jr. Effect of High-Performance Liquid Chromatography Mobile Phase Components on Sensitivity in Negative Atmospheric Pressure Chemical Ionization Liquid Chromatography-Mass Spectrometry, J. Am. Soc. Mass Spectrom. 7, 1059-1069 (1996). 

The stationary phase matrices used in classic column chromatography are spongy materials whose compress-ibihty hmits flow of the mobile phase. High-pressure liquid chromatography (HPLC) employs incompressible silica or alumina microbeads as the stationary phase and pressures of up to a few thousand psi. Incompressible matrices permit both high flow rates and enhanced resolution. HPLC can resolve complex mixtures of Upids or peptides whose properties differ only slightly. Reversed-phase HPLC exploits a hydrophobic stationary phase of... 

In a high-pressure liquid chromatography assay of aspirin tablets, 10 extracts are made and the extracts are diluted with mobile phase solution, which consists of acetonitrile/0.1 M sodium acetate buffer pH 4.5 (10 90) and analysed sequentially. If the rate constant for the degradation of aspirin in the mobile phase is O.OfOl h " at room temperature how long can the andyst store the solutions at room temperature before the degradation of the analyte is greater than 0.5% ... 

If a liquid is used as die mobile phase, the technique used is liquid chromatography (LC). The solid adsorbent is constrained in a tube or column through which the liquid mobile phase flows. Any number of solvents, buffer solutions, or supercritical fluids can be used as liquid mobile phases. High-pressure liquid chromatography (HPLC) is used if pressure is needed to force die liquid phase through the tube. If the liquid phase moves over a thin adsorbent surface propelled by capillary action, die technique used is thin-layer chromatography (TLC). In general, two types of surfaces are used as the solid phase. 

Oxyphenbutazone, and other non-narcotic analgesics are screened by reverse-phase high-pressure liquid chromatography (39). The column is LiChrosorb RP8 and the mobile phase is a acetonitrile-water mixture. Blood and organs are homogenized in 4% perchloric acid before extraction with the solvents. Urine is extracted without primary treatment. 

Samples containing 150 g of 500 ppm acids were also prepared using 3% added sodium chloride in the 90/10 oil/water blend, water, and vegetable oil as the microwave medium. These samples were heated 0, 1, 2, and 3 minutes in the microwave. Changes in the acid concentration were determined by high pressure liquid chromatography with an organic acid column and an aqueous mobile phase. 

Reverse phase high pressure liquid chromatography (HPLC) was used to further fractionate the sample and add another dimension of specificity (8,21). The extract was evaported to dryness and taken up in CHCI3. The entire extract was injected onto a DuPont Zorbax ODS column at 40°C using 2 cc/min. CH3OH mobile phase. Typical chromatograms are shown in Figure 2. 

In normal high pressure liquid chromatography, typical sample volumes are 20-200 p.L this can become as little as 1 nL in capillary HPLC. Pretreatment of the sample may be necessary in order to protect the stationary phase in the column from deactivation. By employing supercritical fluids such as carbon dioxide, pretreatment can be bypassed in many instances so that whole samples from industrial and environmental matrices can be introduced directly into the column. This is due to the fact that the fluid acts as both extraction solvent and mobile phase. Post-column electrochemistry has been demonstrated. For example, fast-scan cyclic voltammo-grams have been recorded as a function of time after injection of microgram samples of ferrocene and other compounds in dichloromethane solvent and which are eluted with carbon dioxide at pressures of the order of 100 atm and temperatures of 50°C the chromatogram is constructed as a plot of peak current vs. time [18]. 

Perkin Trans. 2, 2087 (1988). Solute-Sovent Interactions in Chemistry and Biology. Part 7. An Analysis of Mobile Phase Effects in High Pressure Liquid Chromatography Capacity Factors and Relationships of the Latter with Octanol-Water Partition Coefficients. 

The D4 content of the samples was determined by reverse-phase high-pressure liquid chromatography (HPLC) with a Varian 5500 liquid chromatograph. A DuPont Zorbax ODS (Cis) column was used with a Wilmad infrared detector set at 12.45 xm to monitor the Si-CHa vibration. The mobile phase was an 83 17 mixture of acetonitrile and acetone at a flow rate of 0.8 mL/min. A Rheodyne injector valve operating on compressed air was used with a 10-p,L sample loop for reproducible injection volumes. Ethyl acetate was used to dissolve the samples for analysis. 

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