sodium-dodecyl-sulfate and phosphoric-acid

The present study represents a connection between basic science and clinical applied science through providing a bioanalytical method for the analysis of certain co-administered drugs used for the treatment of rheumatoid arthritis. The studied drugs are esomeprazole, leflunomide and ibuprofen. The proposed bioanalytical method is a simple reversed phase high performance liquid chromatographic method using micellar mobile phase. The method is conducted using a Shim-pack VP-ODS (150 mm × 4.6 mm ID) stainless steel column at ambient temperature with ultraviolet detection at 285 nm. The micellar mobile phase consisted of 0.1 m sodium dodecyl sulfate, 10% n-propanol, 0.3% triethylamine in 0.02 m orthophosphoric acid (pH 3.5) and is pumped at a flow rate of 1.0 mL/min. The calibration curve was rectilinear over the concentration range of 0.1-5.0, 0.5-10.0 and 1.0-20.0 μg/mL for esomeprazole, leflunomide and ibuprofen respectively. The proposed method was successfully applied to the analysis of these drugs in dosage forms. The method is extended to the in-vitro, in-vivo determination of these drugs in spiked and real human plasma samples.

Topics: Adult; Calibration; Chromatography, Liquid; Drug Therapy, Combination; Esomeprazole; Ethylamines; Humans; Ibuprofen; Isoxazoles; Leflunomide; Limit of Detection; Male; Micelles; Phosphoric Acids; Reproducibility of Results; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Ultraviolet Rays

A chemometrics approach has been used to optimize the separation of six quinolone compounds by micellar liquid chromatography (MLC). A Derringer's desirability function, a multicriteria decision-making (MCDM) method, was tested for evaluation of two different measures of chromatographic performance (resolution and analysis time). The effect of three experimental parameters on a chromatographic response function (CRF) expressed as a product of two sigmoidal desirability functions was investigated. The sigmoidal functions were used to transform the optimization criteria, resolution and analysis time into the desirability values. The factors studied were the concentration of sodium dodecyl sulfate, butanol content and pH of the mobile phase. The experiments were done according to the face-centered cube central composite design, and the calculated CRF values were fitted to a polynomial model to correlate the CRF values with the variables and their interactions. The developed regression model showed good descriptive and predictive ability (R(2) = 0.815, F = 6.919, SE = 0.038, [Formula: see text]) and used, by a grid search algorithm, to optimize the chromatographic conditions for the separation of the mixture. The efficiency of prediction of polynomial model was confirmed by performing the experiment under the optimal conditions.

Topics: 1-Butanol; Algorithms; Anti-Bacterial Agents; Chromatography, High Pressure Liquid; Ethylamines; Factor Analysis, Statistical; Hydrogen-Ion Concentration; Micelles; Models, Statistical; Phosphoric Acids; Quinolones; Sodium Dodecyl Sulfate; Solutions; Solvents

Paliperidone is a new antipsychotic drug with a relatively low therapeutic concentration of 20-60 ng/mL. We established an accurate and sensitive CE method for the determination of paliperidone concentrations in human plasma in this study. To minimize matrix effect caused by quantification errors, paliperidone was extracted from human plasma using Oasis HLB SPE cartridges with three-step washing procedure. To achieve sensitive quantification of paliperidone in human plasma, a high-conductivity sample solution with sweeping-MEKC method was applied for analysis. The separation is performed in a BGE composed of 75 mM phosphoric acid, 100 mM SDS, 12% acetonitrile, and 15% tetrahydrofuran. Sample solution consisted of 10% methanol in 250 mM phosphoric acid and the conductivity ratio between sample matrix and BGE was 2.0 (γ, sample/BGE). The results showed it able to detect paliperidone in plasma samples at concentration as low as 10 ng/mL (S/N = 3) with a linear range between 20 and 200 ng/mL. Compared to the conventional MEKC method, the sensitivity enhancement factor of the developed sweeping-MEKC method was 100. Intra- and interday precision of peak area ratios were less than 6.03%; the method accuracy was between 93.4 and 97.9%. This method was successfully applied to the analysis of plasma samples of patients undergoing paliperidone treatment.

Topics: Acetonitriles; Antipsychotic Agents; Chemical Fractionation; Chromatography, Micellar Electrokinetic Capillary; Humans; Isoxazoles; Limit of Detection; Paliperidone Palmitate; Phosphoric Acids; Pyrimidines; Reproducibility of Results; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Solutions

The determination of metal-binding proteins in plankton is important because of their involvement in photosynthesis, which is fundamental to the biogeochemical cycle of the oceans and other ecosystems. We have elaborated a new strategy for screening of Cu and Zn-containing proteins in plankton on the basis of separation of proteins by use of Blue-Native PAGE (BN-PAGE), which entails use of a non-denaturing Tris-tricine system and detection of metals in the proteins by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). For comparison, denaturing PAGE based on Tris-glycine and Tris-tricine systems and Anodic-Native PAGE have also been investigated. A large number of protein bands with MW between 20 and 75 kDa were obtained by use of Tris-glycine PAGE but detection of metals by LA-ICP-MS was unsuccessful because of loss of metals from the proteins during the separation process. Different protein extraction, purification, and preconcentration methods were evaluated, focussing on both issues-achieving the best extraction and characterization of the proteins while maintaining the integrity of metal-protein binding in the plankton sample. Use of 25 mmol L(-1) Tris-HCl and a protease inhibitor as extraction buffer with subsequent ultrafiltration and acetone precipitation was the most efficient means of sample preparation. Two Cu and Zn proteins were detected, a protein band corresponding to a MW of 60 kDa and another poorly resolved band with a MW between 15 and 35 kDa.

Topics: Animals; Buffers; Carbon Dioxide; Cattle; Copper; Ecosystem; Electrophoresis, Polyacrylamide Gel; Glycine; Laser Therapy; Lasers; Mass Spectrometry; Metals; Molecular Weight; Phosphoric Acids; Plankton; Proteins; Serum Albumin; Sodium Dodecyl Sulfate; Zinc

The on-line sample concentration technique, micelle to solvent stacking (MSS), was studied for small organic cations (quaternary ammonium herbicides, β-blocker drugs, and tricyclic antidepressant drugs) in reversed migration micellar electrokinetic chromatography. Electrokinetic chromatography was carried out in fused silica capillaries with a background solution of sodium dodecyl sulfate (SDS) in a low pH phosphate buffer. MSS was performed using anionic SDS micelles in the sample solution for analyte transport and methanol or acetonitrile as organic solvent in the background solution for analyte effective electrophoretic mobility reversal. The solvent also allowed for the separation of the analyte test mixtures. A model for focusing and separation was developed and the mobility reversal that involved micelle collapse was experimentally verified. The effect of analyte retention factor was observed by changing the % organic solvent in the background solution or the concentration of SDS in the sample matrix. With an injection length of 31.9 cm (77% of effective capillary length) for the 7 test drugs, the LODs (S/N=3) of 5-14 ng/mL were 101-346-fold better when compared to typical injection. The linearity (R(2), range=0.025-0.8 μg/mL), intraday and interday repeatability (%RSD, n=10) were ≥0.988, <6.0% and <8.5%, respectively. In addition, analysis of spiked urine samples after 10-fold dilution with the sample matrix yielded LODs=0.02-0.10 μg/mL. These LODs are comparable to published electrophoretic methods that required off-line sample concentration. However, the practicality of the technique for more complex samples will rely on dedicated sample preparation schemes.

Topics: Acetonitriles; Adrenergic beta-Antagonists; Antidepressive Agents, Tricyclic; Cations; Chromatography, Micellar Electrokinetic Capillary; Herbicides; Humans; Hydrogen-Ion Concentration; Linear Models; Micelles; Phosphoric Acids; Quaternary Ammonium Compounds; Reproducibility of Results; Sensitivity and Specificity; Sodium Dodecyl Sulfate

The separation of flunarizine hydrochloride (FLZ) and five of its degradation products--1-[bis(4-fluorophenyl)methyl]-4-(3-phenyl-2-propenyl)piperazine, 4-oxide (A), bis(4-fluorophenyl)methanone (B), bis(4-fluorophenyl)methanol (C), 1-(3-phenyl-2-propenyl)piperazine(D), and 1-[bis-4-fluorophenyl) methyl] piperazine (E)--could be accomplished by reversed phase liquid chromatography using either micellar or microemulsion mobile phases. Cyanopropyl-bonded stationary phase has been used with UV detection at 254 nm. Microemulsion mobile phase consisting of 0.15 M SDS, 10% n-propanol, 1% n-octanol, and 0.3% triethylamine in 0.02 M phosphoric acid of pH 7.0, has been used for the separation of FLZ and its degradation products (B, C, D, and E). Micellar mobile phases consisting of 0.15 M sodium dodecyl sulphate (SDS), 10% n-propanol, 0.3% triethylamine (TEA) in 0.02 M phosphoric acid of pH values either 4.0 or 6.8 have been used for the separation of FLZ from its degradation products, i.e. either from (B, C, D, and E) or from (A, B, C, and D), respectively. Micellar liquid chromatography (MLC) was applied to the determination of FLZ in pure form as well as in dosage forms; the calibration graph was linear over the concentration range of 0.15-50 microg/mL with detection limit of 0.02 microg/mL (4.19 x 10(-8)M).

Topics: 1-Octanol; 1-Propanol; Anticonvulsants; Calibration; Chromatography, Liquid; Ethylamines; Flunarizine; Hydrogen-Ion Concentration; Micelles; Models, Chemical; Phosphoric Acids; Sodium Dodecyl Sulfate; Time Factors

Two stacking methods of capillary electrophoresis (CE) were developed for the separation of very dilute solutions of ephedra-alkaloids, namely ephedrine, pseudoephedrine, methylephedrine, methylpseudoephedrine, norephedrine, and norpseudoephedrine. A sweeping method which uses a carrier comprised of phosphoric acid, sodium dodecyl sulfate (SDS), diethylamine and acetonitrile permits the detection of the alkaloids down to the 10(-1) microg/mL level, and the cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-Sweep-MEKC) method using phosphoric acid, SDS, and acetronitrile as electrolytes can detect down to the 10(-3) microg/mL level. The former requires the conductance of the sample solution to be adjusted beforehand, and only five peaks were observed, two of which were overlapped. The latter is capable of separating the six alkaloids but has a somewhat poorer reproducibility. Using an optimized injection time, it was found that the more diluted a solution is, the greater the sweeping effect will be. The CSEI-Sweep-MEKC method with a 600 s injection time and a 10(-1) microg/mL solution concentration provides an amplification effect of approximately 10(4). The method is suitable for analyses of dilute herb drug extracts and mouse sera. The effect of buffers on the separation and validation of the methods in this study are also discussed.

Topics: Acetonitriles; Alkaloids; Animals; Cations; Chromatography, Micellar Electrokinetic Capillary; Diethylamines; Drugs, Chinese Herbal; Electrolytes; Ephedra; Flow Injection Analysis; Mice; Phosphoric Acids; Plant Extracts; Reproducibility of Results; Serum; Sodium Dodecyl Sulfate; Time

The development of a stability-indicating assay for ranitidine hydrochloride using a mobile phase added ion-interaction reagent was achieved. The assay easily separated all known and unknown impurities/degradants. This assay may be used for the determination of purity, identity and strength for the active ingredient and finished dosage forms. Placebo samples were analyzed for all of the dosage forms and did not interfere with the separation. The system was found to be linear over a range of 0.056 to 44.4 microg/g, with a limit of detection of 0.028 microg/g and a limit of quantitation of 0.056 microg/g. The system precision was determined to be 0.7%. The development of the stability-indicating assay and the effect that each chromatographic variable had on the separation will be discussed.

Topics: Calibration; Chromatography, High Pressure Liquid; Dosage Forms; Hydrogen-Ion Concentration; Phosphoric Acids; Placebos; Ranitidine; Reference Standards; Sensitivity and Specificity; Sodium Dodecyl Sulfate

This study was designed to assess: 1) the ability of several commercially available and laboratory-made acid etchants to penetrate occlusal fissures when used for pit and fissure sealing, and 2) the influence of adding a surfactant to the etchant on penetration of the sealer. Viscosity, surface tension and contact angle to enamel of the etchants were determined for each treatment, and these properties were related to the etchant's ability to penetrate fissures.. Penetration was assessed in an acrylic fissure model having a deep-narrow fissure using a microscope and a chronometer. Penetration depth was expressed as percentage of total fissure depth and was measured in intervals up to 90 s. Commercially available etching agents with different viscosities and two solutions of phosphoric acid (37%), one with and one without a surfactant, were tested. The etch pattern obtained on the fissure wall enamel of extracted teeth with some of these products was evaluated using scanning electron microscopy. Eventually, the penetration depths of a composite sealer in fissures treated with a conventional etchant were compared to those after application of a surfactant-containing etchant on sections of extracted teeth.. None of the commercially available etchants studied were able to penetrate farther than 17% of the total fissure depth in the fissure model. The surfactant-containing etchant showed complete penetration within about 1 min and had a significantly lower surface tension and contact angle than the other products tested. Only the surfactant-containing etchant could produce a retentive pattern on the entire wall enamel of the fissure with the exception of locations blocked by debris and plaque. Fissures treated with this product prior to sealing showed a significantly deeper penetration of the sealer in deep-marrow fissures.. Surfactant-containing etchants with a low viscosity can penetrate completely into fissures and can produce an increased retentive and wettable surface which significantly increased sealant penetration into deep fissures.

Topics: Acid Etching, Dental; Chemical Phenomena; Chemistry, Physical; Dental Enamel; Dental Fissures; Drug Compounding; Materials Testing; Microscopy, Electron, Scanning; Phosphoric Acids; Pit and Fissure Sealants; Sodium Dodecyl Sulfate; Statistics, Nonparametric; Surface Properties; Surface-Active Agents; Viscosity; Wettability