Development of a capillary electrophoretic method for determination of plasma clearance of iohexol in dogs and cats.

Renal function can be monitored by estimation of the glomerular filtration rate (GFR), for example, through measurement of the plasma clearance of a marker that is freely filtrated through the kidney without reabsorption. It has been proposed that iohexol is the most accurate marker for GFR determination in cats and dogs. However, there is a need for a validated capillary electrophoretic method that covers the concentration range for a full curve clearance estimate of iohexol. In the final method, the plasma samples were protein precipitated and the supernatant was analyzed in a background electrolyte containing borate buffer (0.06 m, pH 10.0). The method developed was proved to be linear (concentration range 18- 2900 mg/L) and had a good precision (e.g. 2.3-2.9% at 88 mg/L) and accuracy (e.g. 101-105% at 88 mg/L). Finally, the method was compared with a previously published and validated HPLC-UV method by parallel analysis of clinical plasma samples from dogs and cats administered Omnipaque®. This comparison showed excellent agreement between the two methods and no proportional or systematic error was observed. The proposed method is simple and has a low cost per sample, which makes it applicable for routine analysis.

Evaluation of electroosmotic markers in aqueous and nonaqueous capillary electrophoresis.

The most common method to determine the EOF in CE is to measure the migration time for a neutral marker. In this study, 12 compounds (three novel and some previously used) were investigated as EOF markers in aqueous and nonaqueous BGEs. In the aqueous buffer systems (ammonium acetate, sodium phosphate, and sodium borate) the evaluation included a wide pH range (2-12). Two BGEs contained chiral selectors (sulphated-ß-CD, (-)-diketogulonic acid) and one that contained a micellar agent (SDS) were included in the study. The majority of the evaluated compounds were found to migrate with the EOF in the water-based BGEs and are thus useful as EOF markers. However, in the SDS-based BGE only four of the compounds (acetone, acrylamide, DMSO, and ethanol) were found to be applicable. In the nonaqueous BGEs 11 markers (acetone, acetophenone, acrylamide, anthracene, benzene, 4-(4-methoxybenzylamino)-7-nitro-2,1,3-benzoxadiazole, benzyl alcohol, 2,5-diphenyloxazole, ethanol, flavone, and mesityl oxide) seemed to be functional as EOF markers. Even though several of the evaluated compounds can be used as EOF markers in the investigated BGEs, the authors would recommend the use of acrylamide as a general marker for UV detection. Furthermore, the four fluorescent markers (of which three were novel) gave RSD values equal to the other markers and can be used for the determination of the EOF in CE or microchip CE with fluorescence detection.