High-performance liquid materials

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-... 

As alkanesulfonates are mixtures of homologs as well as isomers, high-performance liquid chromatography (HPLC) proves to be a general method for an exact analysis. For identifying the raw material basis (carbon number cut of normal paraffins used), the carbon number distribution of the homologs can be... 

Commercially available poiybrominated aromatic ethers have been analyzed by reversed phase high performance liquid chromatography. NMR spectra of material isolated by preparative methods served to identify the observed peaks as congeners of tetrabromo to nonabromo diphenyl ether. A bromination pathway was clearly indicated. 

In 1979, it was stated that poiybrominated aromatic ethers have received little attention (ref. 1). That statement is still applicable. Analyses to characterize this class of commercial flame retardants have been performed using UV (refs. 1-2), GC (refs. 1-6), and GC-MS (refs. 1-4). The bromine content of observed peaks was measured by GC-MS, but no identification could be made. The composition of poiybrominated (PB) diphenyl ether (DPE) was predicted from the expected relationship with polyhalogenated biphenyl, a class which has received extensive attention. NMR (refs. 3-6) was successfully used to identify relatively pure material which had six, or fewer, bromine atoms per molecule. A high performance liquid chromatography (HPLC) method described (ref. 1) was not as successful as GC. A reversed phase (RP) HPLC method was mentioned, but no further work was published. 

Gregory, G.K. et ah. Quantitative analysis of lutein esters in marigold flowers (Tagetes erecta) by high performance liquid chromatography, J. Food ScL, 51, 1093, 1986. Livingston, A.L., Rapid analysis of xanthophyll and carotene in dried plant materials, J. AOAC, 69, 1017, 1986. 

Gas-chromatographic determination for plant materials High-performance liquid chromatographic determination for soil... 

Apple, pear, peach, citrus, grape, strawberry, cucumber, green pepper, eggplant and green tea High-performance liquid chromatographic determination for plant materials... 

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... 

Kutsuna, H., Ohtsu, Y., and Yamaguchi, M., Synthesis and characterization of highly stable polymer-coated aminosilica packing material for high-performance liquid chromatography, ]. Chromatogr., 635, 187, 1993. 

Yamauchi, S., Nimura, N., and Kinoshita, T., Protamine-coated silica gel as packing material for high performance liquid chromatography of carbohydrates, Analyst, 118, 161, 1993. 

Zheng, J., Kosmus, W., Pichler-Semmelrock, F., and Kock, M., Arsenic speci-ation in human urine reference materials using high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection, /. Trace Elements Med. Biol., 13, 150, 1999. 

The spectrum of new analytical techniques includes superior separation techniques and sophisticated detection methods. Most of the novel instruments are hyphenated, where the separation and detection elements are combined, allowing efficient use of materials sometimes available only in minute quantities. The hyphenated techniques also significantly increase the information content of the analysis. Recent developments in separation sciences are directed towards micro-analytical techniques, including capillary gas chromatography, microbore high performance liquid chromatography, and capillary electrophoresis. 

It was known from gas chromatographic theory that efficiency could be improved if the particle size of the stationary phase materials used in lc could be reduced. High performance liquid chromatography developed steadily during the late 1960s as these high efficiency materials were produced, and as improvements in instrumentation allowed the full potential of these materials to be realised. As hplc has developed, the particle size of the stationary phase used has... 

Nagels, L.J., Creten, W.L. (1985). Evaluation of the glassy carbon electrochemical detector selectivity in high-performance liquid chromatographic analysis of plant material. Anal. Chem. 57, 2706. 

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