Separation of urea, uric acid, creatine, and creatinine by micellar electrokinetic capillary chromatography with sodium cholate. (1/66)

The capillary electrophoretic separation of the four nonprotein nitrogenous compounds (NPNs; urea, uric acid, creatine, and creatinine) typically employed in clinical and medical settings for the monitoring of renal function is described. Successful resolution of these compounds is achieved with the use of a bile salt micelle system composed of sodium cholate at phosphate buffer pH 7.4. The elution patterns of four NPNs are obtained within 30 min with a voltage of 30 kV. The effect of varying the applied voltage, temperature, and the mole ratio of phosphate buffer with bile salt surfactant on the migration behavior is also examined.  (+info)

Quantification of riboflavin, flavin mononucleotide, and flavin adenine dinucleotide in human plasma by capillary electrophoresis and laser-induced fluorescence detection. (2/66)

BACKGROUND: Riboflavin is the precursor of flavin mononucleotide (FMN) and FAD, which serve as cofactors for several redox enzymes. We have developed a capillary electrophoresis method for the determination of riboflavin and its two coenzyme forms in human plasma. METHODS: Trichloroacetic acid-treated plasma was subjected to solid-phase extraction on reversed-phase columns. The analytes were separated by micellar electrokinetic capillary chromatography in uncoated fused- silica capillaries filled with borate buffer containing 50 mmol/L sodium dodecyl sulfate, methanol, and N-methylformamide. Native fluorescence was monitored at 530 nm, using an argon laser operating at 488 nm as excitation source. RESULTS: The assay was linear over a concentration range of two orders of magnitude, and the limit of detection was far below physiological concentrations for all vitamers. The within-day and between-day coefficients of variation were 4-9% and 6-12%, respectively. The reference values (median, 5-95 percentiles) obtained by analyzing plasma from 63 healthy subjects were 8.6 nmol/L (2.7-42.5 nmol/L) for riboflavin, 7.0 nmol/L (3.5-13.3 nmol/L) for FMN, and 57.9 nmol/L (44.5-78.1 nmol/L) for FAD. CONCLUSIONS: Capillary electrophoresis with laser-induced fluorescence detection allows determination of all riboflavin vitamers far below physiological concentrations. The method may become a useful tool for the assessment of riboflavin status in humans.  (+info)

Simultaneous determination of sweeteners and preservatives in preserved fruits by micellar electrokinetic capillary chromatography. (3/66)

A micellar electrokinetic capillary method for the simultaneous determination of the sweeteners dulcin, aspartame, saccharin, and acesulfame-K and the preservatives sorbic acid; benzoic acid; sodium dehydroacetate; and methyl-, ethyl-, propyl-, isopropyl-, butyl-, and isobutyl-p-hydroxybenzoate in preserved fruits is developed. These additives are ion-paired and extracted using sonication followed by solid-phase extraction from the sample. Separation is achieved using a 57-cm fused-silica capillary with a buffer comprised of 0.05 M sodium deoxycholate, 0.02 M borate-phosphate buffer (pH 8.6), and 5% acetonitrile, and the wavelength for detection is 214 nm. The average recovery rate for all sweeteners and preservatives is approximately 90% with good reproducibility, and the detection limits range from 10 to 25 microg/g. Fifty preserved fruit samples are analyzed for the content of sweeteners and preservatives. The sweeteners found in 28 samples was aspartame (0.17-11.59 g/kg) or saccharin (0.09-5.64 g/kg). Benzoic acid (0.02-1.72 g/kg) and sorbic acid (0.27-1.15 g/kg) were found as preservatives in 29 samples.  (+info)

Analysis of human ouabainlike compound by micellar electrokinetic chromatography. (4/66)

In this preliminary study we have optimised micellar electrokinetic chromatography (MEKC, a form of capillary electrophoresis) to enable the chromatographic and spectral characteristics of human ouabainlike compound (OLC) to be investigated. Sera from fifty patients were combined to form a pool (100 ml) whilst urine (92.5 ml) was obtained from a normal healthy volunteer. Both samples were initially concentrated and partially purified by solid phase extraction before further purification by sequential HPLC separations. Final volumes for both extracts were 100 microl. MEKC was performed on a HP(3D) CE instrument with voltage set at 20 KV, capillary temperature at 20 degrees C, injection time 4 s, sample volume 10 nl, with detection by photodiode array. A compound was found in both serum and urine that had similar elution and spectral characteristics to authentic ouabain. We conclude that MEKC is potentially a useful tool for the analysis of human OLC.  (+info)

Correlation of the capacity factor in vesicular electrokinetic chromatography with the octanol:water partition coefficient for charged and neutral analytes. (5/66)

PURPOSE: The aim of this study was to develop a method based upon electrokinetic chromatography (EKC) using oppositely charged surfactant vesicles as a buffer modifier to estimate hydrophobicity (log P) for a range of neutral and charged compounds. METHODS: Vesicles were formed from cetyltrimethylammonium bromide (CTAB) and sodium n-octyl sulfate (SOS). The size and polydispersity of the vesicles were characterized by electron microscopy, dynamic light scattering, and pulsed-field gradient NMR (PFG-NMR). PFG-NMR was also used to determine if ion-pairing between cationic analytes and free SOS monomer occurred. The CTAB/SOS vesicles were used as a buffer modifier in capillary electrophoresis (CE). The capacity factor (log k') was calculated by determining the mobility of the analytes both in the presence and absence of vesicles. Log k' was determined for 29 neutral and charged analytes. RESULTS; There was a linear relationship between the log of capacity factor (log k') and octanol/water partition coefficient (log P) for both neutral and basic species at pH 6.0, 7.3, and 10.2. This indicated that interaction between the cation and vesicle was dominated by hydrophobic forces. At pH 4.3, the log k' values for the least hydrophobic basic analytes were higher than expected, indicating that electrostatic attraction as well as hydrophobic forces contributed to the overall interaction between the cation and vesicle. Anionic compounds could not be evaluated using this system. CONCLUSION: Vesicular electrokinetic chromatography (VEKC) using surfactant vesicles as buffer modifiers is a promising method for the estimation of hydrophobicity.  (+info)

Separation of sympathomimetic amines of abuse and related compounds by micellar electrokinetic chromatography. (6/66)

Separation of twelve sympathomimetic amines and related compounds by micellar electrokinetic chromatography (MEKC) with UV absorbance detection is described. These amines were well separated within 25 min using 50 mM sodium tetraborate solution containing 15 mM sodium dodecylsulfate (SDS) of pH 9.3 as a running solution and detected at 210 nm. MEKC was performed with an applied voltage of 13 kV at 25 degrees C using a fused-silica capillary (50 cm x 75 mm i.d.) with effective length of 37.5 cm. The detection limits of these compounds were in the range from 4 to 97 fmol/injection at a signal-to-noise ratio (S/N) of 3. The reproducibility of the method expressed as relative standard deviation (RSD) for within-day (n=6) and between-day (n=5) assays was less than 4.8 and 8.8%, respectively. The proposed method could be applied to the determination of an anorectic drug, phentermine, in Chinese tea with a detection limit of 99 microg/g (105 fmol/injection, S/N=3).  (+info)

Evaluation of variation of acteoside and three major flavonoids in wild and cultivated Scutellaria baicalensis roots by micellar electrokinetic chromatography. (7/66)

Micellar electrokinetic chromatography (MEKC) conditions were developed to analyze the constituents of Scutellariae Radix (SR) and Scutellaria baicalensis roots. Using the MEKC method, the major flavonoid constituents of baicalin, baicalein and wogonin of wild and cultivated S. baicalensis roots were compared. In a preliminary comparison of electropherogram, one special peak was found in a wild sample but not in a 2-year-cultivated one. The compound corresponding to the peak was isolated and identified as a phenylethanoid glycoside, acteoside, by comparing the 1H- and 13C-NMR spectral data with that of the authentic compound. This is the first time acteoside has been isolated from the Scutellaria genus. It could only be found in SR derived from wild S. baicalensis roots and 4-year-cultivated plants, but not in plant materials cultivated for 3 years. Applying the MEKC method established in this study, rapid and simultaneous determinations of acteoside together with 3 flavonoids in samples were achieved. The method can thus be used for the quality control of SR in a shorter analysis period than HPLC.  (+info)

Analysis method of the angiotensin-I converting enzyme inhibitory activity based on micellar electrokinetic chromatography. (8/66)

A micellar electrokinetic chromatography (MEKC) method was developed for estimating the angiotensin-I converting enzyme (ACE) inhibitory activity by separating the hippuric acid liberated in the ACE reaction mixture in the presence of an inhibitor, captopril. The hippuric acid was successfully separated and detected by MEKC with a 25 mM sodium dodecyl sulfate solution in a 25 mM phosphate-50 mM borate buffer at pH 7.0; the total analysis took about 5 min. A good linear relationship was observed between the inhibitor and the peak area of hippuric acid release. No significant difference in the ACE inhibitory activity (IC50) of captopril (an antihypertensive medicine) or autolyzed-mushrooms (functional foods) was observed between the conventional method and the MEKC method. The MEKC method was found to be a useful technique for a rapid assay of the ACE inhibitory activity.  (+info)