Quantitation of the ligand in Phenyl-Superose

¹³C SPE MAS measurement of ligand concentration in compressible chromatographic beads

A method for measuring the ligand concentration in heterogeneous materials like chromatography media is described. In this method, (13)C single pulse excitation magic angle spinning NMR experiment with broadband (1)H decoupling is used to determine the peak integrals for a butyl ligand in the spectrum of a dried chromatography medium. Within a carefully controlled protocol, those integrals compared with that of the internal reference compound dimethyl sulfone provide the required volume concentration with an accuracy of ca 2%. The effects of temperature, degree of hydration, and other experimental parameters are discussed.

Quantitative determination of the ligand content in Benzamidine Sepharose 4 Fast Flow media with ion-pair chromatography

A quantitative hydrochloric acid hydrolysis-HPLC method was developed for the analysis of the ligand content of Benzamidine Sepharose 4 Fast Flow media. The method requires about 100 mg of dried sample and simple reaction vials can be utilised. Release of the ligand (p-aminobenzamidine) from the base matrix (Sepharose 4 Fast Flow) was obtained after hydrolysis for 180min at 70 degrees C in concentrated hydrochloric acid. When Benzamidine Sepharose 4 Fast Flow media were treated this way p-aminobenzoic acid and p-aminobenzamidine were the only products released from the ligand. A chromatographic system based on ion-pair reversed phase separation was used to quantify these ligand products. The mobile phase was made acidic enough to make p-aminobenzoic acid and p-aminobenzamidine positively charged in order to make ion-pair formation with hexanesulfonic acid possible. The relative standard deviation of th e method was below 2% and no systematic errors could be detected when the results were compared to an independent method based on elemental analysis (nitrogen). The new HPLC method was used to analyse ligand densities in the range of 2-20 micromol/ml medium.

Determination of the leakage from Phenyl-Sepharose Cl-4B, Phenyl-Sepharose FF and Phenyl-Superose in bulk and column experiments

The release of ligands from Phenyl-Sepharose CL-4B, Phenyl-Sepharose FF and Phenyl-Superose has been studied in bulk and column experiments. The leakage products have been identified and quantified by liquid chromatography, fluorescence spectroscopy and proton NMR spectroscopy. It is demonstrated that the leakage occurs primarily through hydrolysis of the agarose support. However, leakage via ether cleavage of the spacer arm-ligand moiety is also observed especially for Phenyl-Superose. The release of ligands at acidic pH is in agreement with a first-order reaction and correspondingly the rate constants have been estimated for all three gels at pH 1 and 2. These show that 50% of the ligands are intact after 15 years of incubation at pH 2. Phenyl-Superose is the most stable gel at acidic pH, whereas Phenyl-Sepharose CL-4B and Phenyl-Sepharose FF are the most stable at neutral and basic pH.