High-performance liquid chromatography column materials

In the so-called high-performance liquid chromatography column materials with a small particle size (3-10 /im) and a narrow size distribution (- 20%) are used. 

Chiral stationary-phase HPLC (high-performance liquid chromatography) columns can be used to separate the enantiomers of anft -cryptophanes, or CTV derivatives however, it is not an ideal technique owing to its sensitivity to conditions, high expense, and inability to separate large quantities of material. A better approach for the resolution of chiral CTVs and cryptophanes is to attach a resolved chiral moiety onto the CTV or cryptophane framework. The... 

Unfortunately, most column and sorbent manufacturers do not develop column packing materials mainly for SEC work, but for the bigger high-performance liquid chromatography (HPEC) market. However, there are many important differences to consider when designing packings for different modes of chroma-... 

Plant materials are homogenized with methanol. Hexythiazox residue is extracted with hexane and then transferred to acetonitirile by liquid-liquid partitioning. The acetonitirile is removed by rotary evaporation and the sample is cleaned up using Florisil PR column chromatography. The concentrated eluate is subjected to high-performance liquid chromatography (HPLC) analysis. 

Milbemectin consists of two active ingredients, M.A3 and M.A4. Milbemectin is extracted from plant materials and soils with methanol-water (7 3, v/v). After centrifugation, the extracts obtained are diluted to volume with the extraction solvent in a volumetric flask. Aliquots of the extracts are transferred on to a previously conditioned Cl8 solid-phase extraction (SPE) column. Milbemectin is eluted with methanol after washing the column with aqueous methanol. The eluate is evaporated to dryness and the residual milbemectin is converted to fluorescent anhydride derivatives after treatment with trifluoroacetic anhydride in 0.5 M triethylamine in benzene solution. The anhydride derivatives of M.A3 and M.A4 possess fluorescent sensitivity. The derivatized samples are dissolved in methanol and injected into a high-performance liquid chromatography (HPLC) system equipped with a fluorescence detector for quantitative determination. 

Pyrimidifen is extracted from plant materials with methanol-water (7 3, v/v). The extracts are concentrated and pyrimidifen is partitioned with n-hexane after addition of sodium chloride. The organic phase is collected and concentrated. Pyrimidifen in the organic phase is purified by silica gel column chromatography. Pyrimidifen is dissolved in acetonitrile and injected into a high-performance liquid chromatography... 

Today, there are many so-called hyphenated methods with IR. These methods include gas chromatography-infrared (GC-IR) where the IR spectra are taken from materials as they are evolved through the column. Related to this are high-performance liquid chromatography-infrared (HPLC-IR), thermogravimetry-infrared (TG-IR), and multispec-tral infrared (MS-IR). 

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