Comparative study of robustness between micellar electrokinetic capillary chromatography and high-performance liquid chromatography using one-variable-at-a-time and a new multi-variable-at-a-time approach

Evaluation of recombinant human parathyroid hormone by CZE method and its correlation with in vitro bioassay and LC methods

A stability-indicating capillary zone electrophoresis (CZE) method was validated to assess the content/potency of the recombinant human parathyroid hormone (rhPTH 1-34), using ranitidine as internal standard (IS). A fused-silica capillary, (i.d. of 50µm; effective length of 40cm) was used at 25°C; the applied voltage was 20kV. The background electrolyte solution consisted of 50mmolL^-1 sodium dihydrogen phosphate solution at pH 3.0. Injections were performed using a pressure mode at 50 mbar for 45s, with detection by photodiode array (PDA) detector set at 200nm. Separation was obtained with a migration time of 5.3min, and was linear over the concentration range of 0.25-250µgmL^-1 (r² =0.9992). Specificity and stability-indicating capability were established in degradation studies, which also showed that there was no interference of the excipients. The accuracy was 100.28% with bias lower than 0.85%. Analyses of the same batches showed mean differences of the estimated content/potencies of 0.61%, 1.31% higher and 0.86% lower as compared to the validated reversed-phase and size exclusion liquid chromatography methods, and to the UMR-106 cell culture bioassay, respectively, with non-significant differences (p>0.05). Degraded forms were also subjected to the in vitro cytotoxicity test. The results obtained showed the capabilities of each one of the methods, and constitute an alternative strategy to monitor stability, improve the quality control and ensure the batch-to-batch consistency of bulk and finished biotechnology-derived medicine.

Oxidative status and lipofuscin accumulation in urothelial cells of bladder in aging mice

Age-related changes in various tissues have been associated with the onset of a number of age-related diseases, including inflammation and cancer. Bladder cancer, for instance, is a disease that mainly afflicts middle-aged or elderly people and is mostly of urothelial origin. Although research on age-related changes of long-lived post-mitotic cells such as neurons is rapidly progressing, nothing is known about age-related changes in the urothelium of the urinary bladder, despite all the evidence confirming the important role of oxidative stress in urinary bladder pathology. The purpose of this study was thus to investigate the oxidative status and age-related changes in urothelial cells of the urinary bladder of young (2 months) and aging (20 months) mice by means of various methods. Our results demonstrated that healthy young urothelium possesses a powerful antioxidant defence system that functions as a strong defence barrier against reactive species. In contrast, urothelial cells of aging bladder show significantly decreased total antioxidant capacity and significantly increased levels of lipid peroxides (MDA) and iNOS, markers of oxidative stress. Our study demonstrates for the first time that ultrastructural alterations in mitochondria and accumulation of lipofuscin, known to be one of the aging pigments, can clearly be found in superficial urothelial cells of the urinary bladder in aging mice. Since the presence of lipofuscin in the urothelium has not yet been reported, we applied various methods to confirm our finding. Our results reveal changes in the oxidative status and structural alterations to superficial urothelial cells similar to those of other long-lived post-mitotic cells.

A fast method coupling ultrahigh performance liquid chromatography with diode array detection for flavonoid quantification in citrus fruit extracts

Flavonoids are a widely distributed group of polyphenolic compounds present in an extensive range of edible plants, notably Citrus species. This article reports a rapid, optimized, and validated method for the separation and quantification of flavonoids in three Citrus fruit extracts by ultrahigh performance liquid chromatography (UHPLC) using a photodiode array detector. This new procedure allowed the simultaneous separation and quantification of 11 selected flavonoids in 5.5 min, 8.2 times faster than that by HPLC analysis. The solvent consumption for each individual analysis was also reduced almost 6.2-fold. The most abundant component in the analyzed samples was naringin (299.06-544.36 mg 100 g⁻¹), followed by rutin (116.60-256.33 mg 100 g⁻¹) and quercetin (7.78-251.49 mg 100 g⁻¹). Isoquercitrin was found in a lower proportion (60.05-81.88 mg 100 g⁻¹). The method was completely validated, providing a sensitive analysis for flavonoid detection and showing satisfactory data for all the parameters tested. This methodology is cheaper, more environmentally friendly, and easier to perform than others previously described.

A high-throughput multivariate optimization for the simultaneous enantioseparation and detection of barbiturates in micellar electrokinetic chromatography-mass spectrometry

The R- and S-configurations of barbiturates display differences in potency and biological activity. In this study, multivariate micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) approach for the simultaneous analysis of three chiral barbiturates (mephobarbital, pentobarbital, and secobarbital) is developed using a polymeric chiral surfactant. After screening 11 amino acid polymeric surfactants, polysodium N-undecenoxycarbonyl-L-isoleucinate (poly-L-SUCIL) was found to be the best chiral selector. The multivariate central composite design (CCD) is used to optimize the chiral resolution, decrease the total analysis time, and improve the ESI-MS signal-to-noise (S/N) ratio. In the preliminary set of experiments, the ranges of the factors investigated in the multivariate approaches are determined. Next, the CCD design is conducted to determine the best overall chiral resolution with shortest possible run times. This optimization resulted in simultaneous enantioseparation in less than 32 min of all three barbiturates with 3-5 fold higher sensitivity by MS compared to UV detection. The adequacy of the multivariate model is validated by three replicate experimental runs at the predicted optimum conditions. The predicted results of MEKC-MS are found to be in good agreement with the experimental data for migration times, resolution, and S/N ratio. The optimized method provided good results in terms of linearity and recovery values of chiral barbiturates spiked in human serum after solid-phase extraction procedure.

SPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: comparison of direct injection to SPE-MEKC

A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco LC-8, LC-18, LC-SCX, and LC-WCX, as well as Strata-X and X-C). DOX was determined on a 56 cm (effective length 50 cm) x 50 microm id fused-silica capillary. The BGE was 20 mM borate buffer, pH 9.3, containing 80 mM SDS and 7.5% v/v of methanol (30 sx50 mbar), and the temperature and voltage were 25 degrees C and 30 kV, respectively. The analytical wavelength was set at 210 nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1 microg/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80 mM of SDS, 10% v/v of methanol and 40 mM borate buffer (pH 9.3; 30 s x 50 mbar; 25 degrees C; 30 kV; 350 nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition.