HPLC methods chemical mixtures

To separate fuUerene derivatives containing covalently bound groups, HPLC methods are also very important. Addends on the fullerene core have a dramahc influence on the solubility properties and the retenhon behavior. Often, more polar eluents in mixtures or in a pure form can be used and efficient separations on silica gel or several reversed phases (medium polarity), even of different regioisomers of addition products, are possible [220-228], A separahon of Cgg from C70 has also been achieved on the basis of the small difference in their chemical reactivity [229],... 

One of the difficult problems is the analysis of the PMR-15 monomeric mixture for reliable quality control [67]. During the production of BTDE, excessive heating can produce some triester (BTTE). Lauber [68] demonstrated that the presence of BTTE led to final composites of inferior properties. More recently Roberts et al. [69, 70] developed a precise and sensitive HPLC method to analyze the PMR-15 momomer mixture. The results greatly helped to elucidate the complex chemical transformation of PMR-15 resin. Further increase of use-temperature up to 371 °C was achieved by use of thermally more stable diamines in place of MDA [71]. 

Most pharmacopoeias specify that ethambutol hydrochloride contains not less than 98.0% and not more than 100.5% of C10H24N2O2 2HCI, calculated on the dried basis. Pharmaceutical products such as tablets must contain not less than 95.0% and not more than 105.0% of the labeled amount.As for pyrazinamide, the main pharmacopoeia assay method for ethambutol is a titration method. However, an HPLC method is used for the assay of ethambutol HCl in tablets.This method requires that a liquid chromatograph equipped with a 200-nm detector and a 4.6 mm X 15 cm base-deactivated column that contains 5 p,m porous silica particles, 3-10 p,m in diameter, with chemically bonded nitrile groups (CN, LIO) is used. The mobile phase is a mixture of 1.0 ml of triethylamine and 1 L of water, adjusted with phosphoric acid to a pH of 7.0. The flow rate is about 1.0 ml/min. Separately inject equal volumes (about 50 p.1) of standard preparations and the assay preparations into the chromatograph, record the chromatograms, and measure the responses for the major peaks and calculate the quantity, in mg, of ethambutol hydrochloride present in the tablets from the peak responses obtained from the assay preparation and the standard preparation, respectively. The tailing factor must not be more than 2.0, and the relative standard deviation for replicate injections not more than 2.0%. 

In coal liquids, coal tar is a complex mixture of hydrocarbons and presents a challenging analysis for MS. A combination of different methods with MS, including HPLC, desorption chemical ionization (DCI), FI, field desorption (FD), and FAB, has been successfully used for coal tar characterization. 

Part One into practical applications of fractionating specific groups of biological macromolecules. The general format of these chapters is a brief discussion of the chemical and biological properties of the biomolecule family, followed by detailed HPLC methods that have been used suceessfiilly for their analysis. Part Three addresses detection methods that are especially suited for qualitatively and quantitatively analyzing the complex mixtures and minute quantities encountered in biochemistry. 

Traditional PAHs separations by reverse phase (RP)-HPLC is conducted using gradient elution, mainly with acetonitrile water mixtures and sometimes with methanokwater mixtnres. RP-HPLC on chemically bonded Cig phases has been widely used in the environmental analysis of PAHs. Up to date, a wide variety of brands of HPLC columns is available for PAHs determination. Packed columns are rarely used in contemporary GC methods for PAHs, being practically 100% of applications carried out with capillary columns. Many commercial brands of GC and HPLC include in their web pages information related to best columns to work with in a specific application, advices to optimize the best gradient elution, and even suggestions for troubleshooting. 

Polyuzhyn I.P., Smirnova O.Ya., Jatchyshyn J.J., Musyanovich R.Ya., Novikov V.P., Tkachenko V.I. - RP-HPLC Separation of Amino Derivatives of 3-Chloro-l,4-Naphtoquinone. // XVII-th International Symposium on Physico-Chemical Methods of the Mixtures Separation Ars Separatoria 2002 .- June 17-20, 2002.- Borowno n.Bydgoszcz, Poland. - Poster P-37. 

The hydrophilic surface characteristics and the chemical nature of the polymer backbone in Toyopearl HW resins are the same as for packings in TSK-GEL PW HPLC columns. Consequently, Toyopearl HW packings are ideal scaleup resins for analytical separation methods developed with TSK-GEL HPLC columns. Eigure 4.44 shows a protein mixture first analyzed on TSK-GEL G3000 SWxl and TSK-GEL G3000 PWxl columns, then purified with the same mobile-phase conditions in a preparative Toyopearl HW-55 column. The elution profile and resolution remained similar from the analytical separation on the TSK-GEL G3000 PWxl column to the process-scale Toyopearl column. Scaleup from TSK-GEL PW columns can be direct and more predictable with Toyopearl HW resins. 

Some Chemical Considerations Relevant to the Mouse Bioassay. Net toxicity, determined by mouse bioassay, has served as a traditional measure of toxin quantity and, despite the development of HPLC and other detection methods for the saxi-toxins, continues to be used. In this assay, as in most others, the molar specific potencies of the various saxitoxins differ, thus, net toxicity of a toxin sample with an undefined mixture of the saxitoxins can provide only a rough approximation of the net molar concentration. Still, to the extent that limits can be placed on variation in toxin composition, the mouse assay can in principle provide useful data on trends in net toxin concentration. However, the somewhat protean chemistry of the saxitoxins makes it difficult to define conditions under which the composition of a mixture of toxins will remain constant thus, attaining a reproducible level of mouse bioassay toxicity is difficult. It is therefore useful to review briefly some of the chemical factors that should be considered when employing the mouse bioassay for the saxitoxins or when interpreting results. Similar concepts will apply to other assays. 

Separation and quantitation of carbohydrate mixtures may be achieved using HPLC, a method that does not necessitate the formation of a volatile derivative as in GLC. Both partition and ion-exchange techniques have been used with either ultraviolet or refractive index detectors. Partition chromatography is usually performed in the reverse phase mode using a chemically bonded stationary phase and acetonitrile (80 20) in 0.1 mol U1 acetic acid as the mobile phase. Anion- and cation-exchange resins have both been used. Carbohydrates... 

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