Very fast electrophoretic determination of creatinine and uric acid in human urine using a combination of two capillaries with different internal diameters.

A capillary system formed by combining 25 and 100 µm id capillaries was used in the short-end injection mode to determine creatinine and uric acid in human urine. The separation was performed at an electric field intensity of 2.3 kV/cm. Creatinine was determined in a BGE with a composition of 20 mM citric acid/NaOH (pH 3.0), and uric acid was determined in 20 mM MES/NaOH (pH 6.0). Under these conditions, migration times of 12.2 s for creatinine and 8.6 s for uric acid were achieved. The LOD value is 2.4 mg/L for creatinine and 0.9 mg/L for uric acid; the RSD for the migration time varies in the range 0.7-1.1% (intra day) to 1.0-7.5% (inter day); RSDs for the peak areas equalled 3.4-4.0% (intra day) and 4.3-4.7% (inter day). The determined creatinine values in seven urine samples vary in the range 221-1394 mg/L for creatinine and 87-615 mg/L for uric acid. t-Test did not reveal any statistically significant difference between the developed CE methodologies and reference methods - Jaffé reaction for creatinine and enzymatic uricase test for uric acid.

Determination of midazolam in rabbit plasma by GC and LC following nasal and ocular administration.

GC with nitrogen phosphorus detection and HPLC with UV detection were used to determine midazolam (MDZ) levels in rabbit plasma following ocular and nasal administration. For GC with nitrogen phosphorus detection, the analyte was extracted from the plasma using a three-step liquid-liquid extraction including extraction with an isopropanol/butyl chloride mixture in an alkaline solution, followed by extractions with 1 M HCl, and finally with an alkaline solution of butyl chloride. The recovery of MDZ was dependent on the sample alkalization time prior to the final extraction. The procedure increased the recovery of MDZ up to 99.6%. Improved sample preparation led to a significant increase in the sensitivity of the determination by GC with nitrogen phosphorus detection. The achieved detection limit was 0.34 ng/mL, which is ten times lower than that obtained using HPLC with UV detection. The small plasma volume was another advantage of the GC with nitrogen phosphorus detection method (200 µL per assay). Both administration routes of the anesthetic (nasal and ocular) resulted in comparable plasma MDZ levels. Kinetic simulation of the MDZ plasma was performed for both administration routes.

Determination of uric acid in plasma and allantoic fluid of chicken embryos by capillary electrophoresis.

Capillary electrophoresis with diode array detection (DAD) was used to determine uric acid (UA) in chicken plasma and the allantoic fluid of chicken embryos. Complete separation of uric and ascorbic acids was attained in less than 10 min in the optimized BGE containing 60 mM MES + 30 mM Tris + 0.001% (w/v) polybrene (pH 6.1). The limit of UA detection (0.2 mg/L) was found to be low enough for sensitive analysis of native plasma and allantoic fluid samples. Range of linearity (1-200 mg/L), repeatability for peak area (CV <4.1%) and migration time (CV < 2.5%), as well as recovery of UA from biological samples (97-100%), were found to be satisfactory. The method was applied to detect the elevated UA concentrations (hyperuricemia) in chicken embryos with induced unilateral renal agenesis. CE/DAD analysis of the chicken plasma can be carried out with a relatively small volume of samples (1 microL).