High performance liquid chromatography solvent purity

Because of the instability of cyanohydrins, the characterization of cyanohydrins mostly should be hydroxyl protected. In 2001, Gerrits et al. [26] investigated the influence of solvent composition on the stability of unprotected cyanohydrins and then described a method to analyze unprotected cyanohydrins (with regard to enantiomeric purity and conversion) via chiral high-performance liquid chromatography (HPLC). Hernandez et al. [27] and the groups... 

High-performance liquid chromatography (HPLC) grade Solvents of suitable purity for use in liquid chromatography procedures. 

The application of high-performance liquid chromatography to the determination of the concentrations in the two immiscible solvents together with a miniaturisation of the technique can speed up the measurements, and minimise the sample requirement regarding quantity and purity. 

Many technical problems can occur with gradient elution, some of which can be avoided through various methods. To begin, gradient elution relies upon the purity of the solvents used. The high-performance liquid chromatography (HPLC) column can collect impurities. 

Thin-layer chromatography (TLC) is mainly applied in micropreparative taxoids separation [2-4]. Silica gel 6OF254 preparative plates are usually applied for this purpose. The problem of taxoids separation involves not only their similar chemical structure (e.g., paclitaxel versus cephalomannine) but also, due to different coextracted compounds usually encountered in crude yew extracts (polar compounds such as phenolics and nonpolar ones such as chlorophylls and biflavones), the separation is very difficult. The common band of paclitaxel and cephalomannine was satisfactorily resolved from an extraneous fraction in isocratic elution with ethyl acetate as a polar modifier [4] and n-heptane-dichloromethane as the solvent mixture and it was of suitable purity for high-performance liquid chromatography (HPLC) quantitative determination. 

We isolated C7g, Cg2 and Cg4 by high-performance liquid chromatography (the preparation is described in detail elsewhere ). Laser-desorption time-of-flight mass spectra were obtained to confirm the purity of the isolated samples. We used an ArF (193 nm) laser as the desorption light source . Mass spectra for the samples of C78, Cg2 and Cg4 are shown as inserts to Fig. la-c. We measured C NMR spectra of the higher fuiierenes using CS2 as the solvent with Cr(C5H702)3 as a relaxant. 

Besides the discussed above, gas chromatographic analysis has also been successfully employed for the determination of moisture contents [Se 71]. This method is most preferred for the selective detection and determination of other impurities. Paper, thin-layer and, most recently, high-performance liquid chromatography are also used to check the purities of solvents. However, in general, they are employed only if some special impurity is to be detected or determined. Otherwise, it is sufficient to determine some characteristic, impurity-sensitive, physical property of the carefully purified system. 

Unfortunately, the labeled 9Z,11E) CLA isomer was contaminated with (9 ,11 ) isomer and oveneduced fatty adds. Purification by C18 reversed-phase high-performance liquid chromatography (RP-HPLC) followed by silver resin chromatography furnished pure methyl (9Z,llfi)-[9,ll-2H]-octadecadienoate (isomeric purity >99% isotopic purity 82-88%) in 60-70% overall yields. In this paper, the author also noticed that increasing the ratio of quinoline to substrate and the volume of solvent resulted in improved chemical and isotopic yields, but the formation of overreduced by-products could uot be prevented. 

Instmmental methods of analysis provide information about the specific composition and purity of the amines. Qualitative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and determination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a liquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using silica columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofiiran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for qualitative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

Impurities in and additives to solvents can cause several problems and artifacts in liquid and gas chromatography. " Primarily they can be the origin of irreproducible separations, enhanced UV-background and even of mechanical problems. De Schutter and Col have investigated this problem in purity of solvents used in high-performance thin-layer chromatography. 

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