salicylates and benzylamine

The simultaneous separation and detection of small cations and anions by capillary zone electrophoresis (CZE) with indirect ultraviolet (UV) detection was successfully demonstrated in a background electrolyte (BGE) containing two UV-absorbing components. Benzylamine, imidazole, benzenesulfonic acid, sulfosalicylic acid, and pyromellitic acid were tested as the components of the BGE. The success of the simultaneous separation of the cations and anions is dependent upon the proper selection of the electrolyte components and control of the migration of the ions towards the detector. High pH is beneficial to the detection of anionic analytes but not to the separation of cationic analytes because of large electroosmotic flow produced under this condition. The upper pH limit of the working pH range is confined by the pKa value of the cationic component of the BGE. The influence of pH and total electrolyte concentration on the electroosmatic flow (EOF) counteracted each other. This counteraction effect imposes an upper limit on the change of total electrolyte concentration at certain pH. It was found that the EOF should be larger by at least 10 x 10(-5) cm2V(-1)s(-1) than the electrophoretic mobilities of the anions so that the anions could be detected on the cathodic side within reasonable times and with good peak shapes. In the imidazole-sulfosalicylic acid BGE, the detection limits (signal to noise, S/N = 3) for the cations and anions ranged from 100 to 900 ppb. In the benzylamine-pyromellitic acid BGE, K+, Na+, Li+, CH3 COO-, HPO4(2-), F-, ClO3-, ClO4-, NO3-, NO2-, Cl- and SO4(2-) were separated within twelve minutes. The strategies for selection of the electrolyte components of the binary BGE were also discussed.

Topics: Acetic Acid; Anions; Benzenesulfonates; Benzoates; Benzylamines; Cations; Electricity; Electrolytes; Electrophoresis, Capillary; Hydrogen-Ion Concentration; Imidazoles; Salicylates; Ultraviolet Rays

Capillary zone electrophoresis (CZE) methods with indirect absorbance detection for analyzing mixtures of alpha-, beta-, and gamma-cyclodextrins (CDs) and their derivatives have been developed. Benzylamine, salicylic, sorbic, or 1-naphthylacetic acid (NAA) was utilized as background electrolyte (BGE) and absorbance provider. Separation of alpha-, beta-, and gamma-CD could be achieved in less than 18 min when the CZE was run in 2 mM NAA or 5 mM sorbate solution (pH 12.2) and detected by indirect absorbance at 222 or 254 nm, respectively. Mixtures of alpha- and beta-CDs, and dimethyl- and trimethyl-derivatives of beta-CD could also be analyzed by CZE, using 50 mM salicylic acid or benzylamine solution (pH 6.0) as BGE with indirect absorbance detection at 230 and 210 nm, respectively. CZE methods for determining the inclusion complex formation constants of various CDs for salicylic acid or benzylamine with either direct or indirect absorbance detection have also been developed. The formation constants of salicylate are in the range from ca. 8 +/- 0.3 mole-1 for the complex with alpha-CD to ca. 99 +/- 2 molarity-1 for the complex with methyl-beta-CD. The detection limits (determined at a signal-to-noise ratio of 3) for the NAA and the salicylate system are ca. 0.1 mM and 1 mM, respectively.

Topics: alpha-Cyclodextrins; Benzylamines; beta-Cyclodextrins; Cyclodextrins; Electrolytes; Electrophoresis, Capillary; gamma-Cyclodextrins; Naphthaleneacetic Acids; Salicylates; Salicylic Acid; Sorbic Acid