Eluents cetyltrimethylammonium bromide

Both acidic and basic drugs can be chromatographed on silica using aqueous methanolic eluents containing cetyltrimethylammonium bromide (S. H. Hansen,... 

The kind of counter ion of an ion-pair reagent is vitally important for selecting the appropriate detection method. If suppressed conductivity detection is applied, the ion-pair reagent is used in its hydroxide form. With direct conductivity detection, salicylate is perferred as the counter ion for tetraalkylammonium cations [19,20], since these salts exhibit a lower background conductance in aqueous solution. According to Wheals [21], eluents such as cetyltrimethylammonium bromide in combination with citric acid at pH 5.5 have proved suitable for UV-, RI-, and amperometric detection, as well as for direct conductivity detection. This example is an impressive illustration of the versatility of ion-pair chromatography. 

Retention data of 12 corticosteroids including prednisolone is given on dynamically modified silica by cetyltrimethylammonium bromide added to the eluent with various organic modifiers. Separation factors between hydrocortisone and 11 other corticosteroids including prednisolone measured on 8 different silica columns and six different ODS-silica columns are presented. The variations in selectivity were found to be substantially smaller than those of chromatographic systems based on chemically bonded ODS-silicas from the same sources (104). 

A linear behavior between k and n was found for n-alkylbenzenes eluted with pure micellar eluents of the anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB), and nonionic poly[oxyethylene(10 or 23)]dodecanol (Brij 22 or Brij 35), and with hybrid eluents containing SDS or CTAB and 2-propanol. The homologues of n-alkylphenones eluted with pure and hybrid mobile phases of CTAB showed the same behavior, but linear relationships were observed between log k and nc for these compounds eluted with SDS mobile phases, the same type of correlation found in aqueous-organic systems. It seems that the... 

The eight principal metabolites of sulfasalazine (salicylazosulfapyridine. Figure 6.61) have been measured in plasma by direct injection HPLC after protein precipitation with methanol. The analytical column was unmodified silica and the eluent was methanol-aq. potassium phosphate (0.2molL pH 6.5)-water (45 + 10 + 45) containing cetyltrimethylammonium bromide (3.75 mmolL ). Detection was at a GCE (+0.6 V vs Ag/AgCl). 

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