Phases Of Sodium Dodecyl Sulfate Research Articles

Extraction of Alkaloids by the Micellar Phase of Sodium Dodecyl Sulfate for their Further Chromatographic Determination

The influence of the main parameters of hydrophobicity (log P), structure (PSA), and protolytic properties (pKa) of some alkaloids on their distribution into modified micellar extraction system based on sodium dodecyl sulfate (SDS-NaCl-H2Sal) was established. The proposed prognostic regression D= 941 – 4.09∙PSA – 27.3∙log P – 44.5∙рКа is characterized by satisfactory indexes (R-squared 99.9, F-ratio 242, standard error 7.19, mean absolute error 2.38). The accuracy of the alkaloid distribution prediction by this regression is well correlated with accuracy of the measurement of the extraction parameters. The predicted D value for novocaine is 257 (R = 93 %), and the experimentally found D value is 202 (R = 91 %). For lidocaine, the predicted and experimental D values are practically the same and equal 386 (R = 95 %) and 380 (R = 95 %), respectively. The possibility of quantitative extraction of positively charged hydrophilic (logP < 0) organic bases into the micellar phase of SDS is shown. The developed hybrid HPLC technique for determining papaverine in urine with its cationic form (pH=2) preconcentration by modified micellar SDS phase is characterized by sufficient sensitivity and accuracy (DL= 0.01 μg/ml, Sr ≤ 0.08, R > 99 %, K = 10). Only alkaloids with log P > 1.4 can be determined by this technique because otherwise, the chromatographic peaks of salicylic acid and alkaloid cannot separate.

Aqueous liquid chromatography with mobile phases of sodium dodecyl sulphate and ionic liquid

In conventional reversed-phase liquid chromatography (RPLC) with hydro-organic solvents, basic cationic solutes yield retained, broad, asymmetric peaks, owing to their interaction with free anionic silanols in the stationary phase. RPLC mobile phases to which the anionic surfactant sodium dodecyl sulphate (SDS), or an ionic liquid (IL) are added, have been proposed as solutions, since these additives are able to block the silanol effect thus improving the chromatographic performance. With these additives, it is however necessary to increase the elution strength by adding an organic solvent, such as an alcohol or acetonitrile. A novel aqueous liquid chromatographic mode (in the absence of organic solvent) is here proposed, where the mobile phases contain only a mixture of aqueous solutions of SDS and an IL derived from 1-alkyl-3-methylimidazolium associated to chloride, both environmentally friendly. When these reagents are added, the anionic surfactant adsorbed on the stationary phase is able to attract the cationic solutes, whereas the adsorbed IL cation repels them. The combination of both effects (attraction and repulsion) allows the modulation of retention, by varying the IL/SDS ratio. Given the character of the additives, a type of green liquid chromatography is achieved. In this work, the chromatographic behavior of six basic compounds of pharmaceutical interest, the β-adrenoceptor antagonists acebutolol, atenolol, carteolol, metroprolol, oxprenolol and propranolol, is examined. In order to assess the chromatographic behavior of the mixed mobile phases containing SDS and IL, changes in retention, peak profile and resolution of mixtures of the analytes were explored at varying concentration of the additives.

Local velocity of thermoresponsive colloidal gels in rate-driven flow

The interplay between flow and attractive interactions in colloidal gels results in complex particle trajectories and velocity profiles that are not evident from bulk rheological measurements. We use high-speed confocal microscopy to investigate the local velocity of a low volume fraction (ϕ = 0.20) thermogelling nanoemulsion system as it flows through a cylindrical capillary at temperatures below and above the gel point. The nanoemulsions are composed of poly(dimethyl siloxane) droplets in a continuous phase of sodium dodecyl sulfate, de-ionized water, and a gelator molecule, poly(ethylene glycol diacrylate). The trajectories of fluorescent polystyrene tracer beads in the oil-rich domains are tracked using two-dimensional image processing. While the velocity profiles agree with those computed from rheometry measurements for nanoemulsion suspensions below the gel point temperature, increasing attractive interactions above the gel point results in statistically significant deviations. Specifically, the velocity measurements indicate a higher yield stress and a larger degree of shear thinning than expected from bulk rheology measurements, resulting in a more plug-shaped velocity profile as temperature and associated interdroplet attraction increase. These deviations from theoretical predictions are likely due to structural heterogeneity. Confocal microscopy images show that small, fluidized clusters are found in high shear rate regions near the capillary walls, while large dense clusters form in low shear rate regions closer to the center of the capillary.

Quantification of rifampicin and rifabutin in plasma of tuberculosis patients by micellar liquid chromatography

A Micellar Liquid Chromatographic method is described to determine Rifampicin and Rifabutin in plasma from Tuberculosis patients. Samples were diluted in mobile phase and then directly injected, avoiding long and tedious extraction steps. The analytes were resolved from the matrix without interferences from endogenous compounds using a mobile phase of sodium dodecyl sulfate 0.15 mol L-1–6%(v/v) 1-pentanol and phosphate buffer at pH 3, running at 1 mL min−1 through a C18 column at 25 °C. Detection was carried out by UV absorbance at 270 nm. Under these conditions, the final chromatographic analysis time was 22 min. The analytical methodology was validated following the FDA 2018 Bioanalytical Method Validation Guidance for Industry. The response of the drugs in plasma was linear in the 0.05–5 μg/mL range, with r2 > 0.9993. Trueness and precision were <14% for both substances. Carry over and matrix effects were negligible. Dilution integrity, robustness and stability were also investigated. Method was reliable, economic, eco-friendly, safe, easy-to-conduct, and with a high sample throughput, thus useful for routine analysis. Finally, the analytical method was used to determine both antituberculosis drugs in incurred plasma samples of Tuberculosis patients.

Greener liquid chromatography using a guard column with micellar mobile phase for separation of some pharmaceuticals and determination ofparabens

In this research, a greener chromatography employing a short column, Zorbax SB C18 cartridge (12.5×4.6mm, 5μm) commonly used as a guard column in a reverse phase high performance liquid chromatography (RP-HPLC), was utilized as the analytical column in conjunction with a more eco-friendly micellar mobile phase of sodium dodecyl sulfate (SDS) for separation tertiary mixtures of local anesthetics and antihistamines; and binary mixture of colds drugs; and quaternary mixture of some parabens with different separation conditions. The chromatographic behavior of these analytes was studied to demonstrate separation efficiency of this guard column in a micellar mobile phase. Moreover, this column and SDS mobile phase was exploited for determination of parabens in 64 samples of cosmetic product, both those that were produced locally in the community and those that were commercially manufactured. Linear calibration graphs of the parabens as detected at 254nm were obtained in the range of 1–100μmolL−1 with R2>0.9990. Percentage recoveries were 92.4–109.2 with %RSD<3, and the limit of detection and quantitation were 0.04–0.10 and 0.20–0.80μmolL−1, respectively. This analytical system is not only greener but also faster and employing simpler sample preparation than a conventional liquid chromatographic system.

Use of micellar mobile phases for the chromatographic determination of melamine in dietetic supplements

Melamine is a nitrogen-rich industrial chemical which is occasionally used to increase the apparent protein content of different products destined for human and animal consumption. In this work, a liquid chromatographic procedure that uses micellar mobile phases of sodium dodecyl sulfate (SDS) buffered at pH 3, a C18 column and UV detection is reported for the determination of melamine in dietetic supplements. Samples were reconstituted with a SDS solution and were directly injected, thus avoiding long extraction and experimental procedures. Melamine was eluted in less than 10 min with no interference by other compounds of the matrices. The optimum mobile phase composition was taken by a chemometrical approach that considers the retention factor, efficiency and peak shape. Validation was performed following the indications of the European Commission (Decision 2002/657/EC). The following parameters were considered: linearity (0.02-100 μg mL(-1); R(2) = 0.9996), intra- and inter-day precisions (<12.4%), accuracy (90.0-101.3%), and robustness (less than 9.8% and 5.1%, for retention time and peak area, respectively). The limits of detection and quantification were 9 and 20 ng mL(-1), respectively. Recoveries for several spiked samples were in the 85.8-114.3% range. These results indicate that the proposed methodology is useful for routine analysis of control quality of infant formula and adult dietetic supplements.

Preconcentration of proteins using modified micellar phases of sodium dodecyl sulfate

The influence of electrolyte and additives of organic acids and alcohols on the efficiency of the extraction of ovalbumin and casein into micellar phases of sodium dodecyl sulfate is studied. The optimal acidity and the conditions for the preconcentration of the proteins using low-temperature anion-active phases are found. Micellar extraction procedures for the extraction of proteins from fabrics, solid surface, and biological fluids are proposed.

Preparation and Characterization of Mesoporous Iron-Oxide

Transition metal oxides are easy to form insoluble oligomer in reaction because of complicated oxidation states,so it is difficult to obtain the desired mesoporous structure.To resolve the problem,mesoporous iron oxide was synthesized by reacting a micellar phase of sodium dodecyl sulfate(SDS) with iron polymer solution which was prepared by controlling the proportion of sodium hydroxide and ferric chloride.Crystal structure and surface structure of the mesoporous iron oxide was characterized by powder X-ray diffraction(XRD),Fourier transform-infrared spectroscopy(FT-IR),thermogravimetric analyse(TGA),Nitrogen adsorption-desorption method and so on.The results show that mesoporous α-Fe2O3 can be obtained after calcining at 450℃ with OH-/Fe3+ ratio of 2.0.Its surface area is 146.5m2·g-1,BJH average diameter is 6.9nm,pore volume is 0.27cm3·g-1.The as-prepared mesoporous iron oxide has better thermal stability,it still has surface area of 110.2m2·g-1 after calcination at 550℃.

Analysis of omeprazole and its main metabolites by liquid chromatography using hybrid micellar mobile phases

Omeprazole is a selective inhibitor of gastric acid secretion and is one of the most widely prescribed drugs internationally. A chromatographic procedure that uses micellar mobile phases of sodium dodecyl sulphate and propanol buffered at pH 7 and a C18 column is reported for the determination of omeprazole and its principal metabolites (omeprazole sulphone and hydroxyomeprazole) in urine and serum samples. In this work, direct injection and UV detection set at 305 nm was used. Omeprazole and its metabolites were eluted in less than 11 min with no interference by the protein band or endogenous compounds. Adequate resolution was obtained with a chemometric approach, in which the retention factor and shape of the chromatographic peaks were taken into account. The analytical parameters including linearity ( r > 0.9998), intra- and inter-day precision (RSD, %: 0.6–7.9 and 0.14–4.7, respectively) and robustness were studied in the validation of the method for the three compounds. The limits of detection and quantification were less than 6 and 25 ng mL −1, respectively. Recoveries in micellar medium, plasma and urine matrices were in the 98–102% range. Finally, the method was successfully applied to the determination of omeprazole and its metabolites in physiological samples. Omeprazole was also analysed in pharmaceutical formulations.

Measurement of multilamellar onion dimensions under shear using frequency domain pulsed gradient NMR

We present a simple method by which the dimensions of shear-induced multilamellar vesicles (MLVs), also known as onions, can be measured during the shearing process itself. This approach is based on the use of a closely spaced train of magnetic field gradient pulses applied during a CPMG echo sequence. The CPMG train compensates flow effects while the frequency-dependence of apparent diffusion can reveal the onion size. We present here a simple phenomenological model for restricted diffusion in multilamellar vesicles, which may be used to interpret the resulting diffusion spectrum. We demonstrate this approach with MLVs formed from the lamellar phase of sodium dodecyl sulfate (SDS) in water and octanol.

Determination of trazodone in urine and pharmaceuticals using micellar liquid chromatography with fluorescence detection

A simple and reliable liquid chromatographic procedure is described for the determination of trazodone in pharmaceutical formulations and urine samples. The optimized procedure uses fluorimetric detection, a C18 column and a micellar mobile phase of sodium dodecyl sulfate (SDS) and 1-butanol. The mobile phase selected for use was 0.2 M SDS and 8% 1-butanol fixed at pH 3 with phosphate buffer. The total analysis time was 10 min. For the analysis of urine samples, one great advantage of the method is that no extraction step is required. The quantification limit was 9.5 ng mL −1, ensuring the analysis of the drug in biological fluids. The procedure shows good accuracy, repeatability and selectivity. Repeatability and intermediate precision were tested for several concentrations of the drug. Good claim percentages were obtained in the analysis of pharmaceutical formulations. Calibration repeatability in urine matrix was also studied in the 0.06–22.4 μg mL −1 range. Good recoveries were obtained from spiked urine samples. No interferences from common additives frequently administered with trazodone or from endogenous compounds in urine samples were found. The results show that the procedure is suitable for routine analysis of the drug.

Micellar liquid chromatographic determination of five antianginals in pharmaceuticals

A procedure was developed for the determination of five antianginals (diltiazem, nadolol, nifedipine, propranolol and verapamil), using hybrid micellar mobile phases of sodium dodecyl sulphate (SDS) and pentanol, a C18 column and UV detection. All possible combinations of antianginals were resolved and determined using a mobile phase of 0.05 M SDS–5% pentanol with an analysis time of 9 min. Repeatabilities and intermediate precision were evaluated at four different drug concentrations in the 2–20 μg/ml ( n = 5) range. Limits of detection were in the range 0.028 μg/ml for diltiazem and 0.130 μg/ml for verapamil. The range of the limit of quantitation was from 0.092 to 0.431 μg/ml for the same compounds. Antianginal drugs were studied in pharmaceuticals with no interference from related compounds. The results of the analyses of pharmaceuticals formulations were in agreement with the declared compositions.

A study of molecular complex formation between propyl gallate and ascorbic acid in the microemulsion phase of sodium dodecyl sulfate, pentanol and water system

The association between two water-soluble antioxidants, i.e. ascorbic acid and propyl gallate have been studied by absorption spectroscopy in microemulsion formed in sodium dodecyl sulfate/pentanol/water micellar system. It has been shown that propyl gallate forms 1:1 molecular complex with ascorbic acid in every solution. Evolution of the absorption spectra during the study of molecular complex formation goes through well-defined isosbestic points. The association constants were calculated using curve-fitting procedure. The observed interactions are stronger in the less polar solvents.

Ultramicroelectrode Voltammetric Investigation of the Micellar Phase of Sodium Dodecyl Sulfate in Aqueous Solution

Abstract Ultramicroelectrode voltammetric measurements have been made on Sodium Dodecyl Sulfate (SDS) in aqueous solutions using K4Fe(CN)6 as the electroactive probe and H2SO4 as the supporting electrolyte. By extrapolation, the SDS micellar diffusion coefficient (D m), hydrodynamic radius (R m), aggregation number (n), and the molecular weight of SDS micellar in aqueous solutions at various surfactant concentrations are obtained. The partition coefficients, KD , of the electroactive probe between micelle and water continuous phase are also estimated. The results suggest that the probe is sensitive to the surfactant concentration and reflect the changes of the structure and the hydrophobic nature of micelles.

Therapeutic Drug Monitoring of Anticonvulsant Drugs by Micellar HPLC with Direct Injection of Serum Samples

We developed a micellar liquid chromatographic (MLC) procedure for the determination of three extensively monitored antiepileptics in serum samples: carbamazepine, phenobarbital, and phenytoin. We determined the composition of the mobile phase after modeling the elution behavior of the antiepileptics in hybrid micellar mobile phases of sodium dodecyl sulfate (SDS) with different organic modifiers (propanol, butanol, or pentanol) in an experimental design that used five mobile phases, a C(18) column, and ultraviolet detection. In the micellar chromatographic system, the serum samples can be injected directly. The optimum mobile phase was 70 mL/L butanol in 0.05 mol/L SDS, pH 7, in which the three antiepileptics were resolved in <10 min. Intra- and interday precision was evaluated at four different drug concentrations within the therapeutic range (n =10); CVs were <2.1%. The method was applied to the analysis of 120 serum samples, and results were similar to those obtained by the TDx method. The MLC method allows chromatographic determination of three antiepileptics, using an interpretative strategy of optimization, without pretreatment of the serum samples and with direct injection in a hybrid micellar mobile phase of SDS-butanol. The method provides complete resolution and quantification of mixtures of two and three antiepileptics.

Micellar-organic versus aqueous-organic mobile phases for the screening of β-blockers

A comparative study of the performance of reversed-phase liquid chromatography with micellar-organic (MLC) and aqueous-organic (RPLC) mobile phases is reported for the separation of 16 β-blockers (acebutolol, alprenolol, atenolol, bisoprolol, carteolol, celiprolol, esmolol, labetalol, metoprolol, nadolol, oxprenolol, pindolol, practolol, propranolol, sotalol, and timolol). MLC with hybrid mobile phases of sodium dodecyl sulfate (SDS) and propanol is revealed as a very competitive technique for the screening of these drugs. Using a conventional Spherisorb C18 column, the theoretical plates ( N) and asymmetry factors ( B/ A) for the optimal mobile phase compositions were in the ranges N=2200–4400 and B/ A=1.0–1.3 for SDS–propanol against N=290–960 and B/ A=2.2–3.6, and N=1700–5100 and B/ A=1.5–2.2 for acetonitrile–water in the absence and presence of 0.1% (v/v) triethylamine. With a base-deactivated XTerra MS C18 column and acetonitrile–water, peak shape was improved ( N=1100–8800 and B/ A=1.1–2.5), but the elution pattern (large differences in retention between polar and low polar compounds) was similar to that achieved with the Spherisorb column. A set of 14 β-blockers showing a wide range of polarities ( log P o/w =− 0.03 for atenolol to 2.60 for propranolol) could be resolved isocratically with a mobile phase of 0.10 M SDS–15% (v/v) propanol with an analysis time of 32 min. The resolution was better than with aqueous-organic RPLC using the conventional and base-deactivated C18 columns, where only 10–12 compounds could be separated in a single chromatogram. Using specific mobile phases of SDS–propanol, all possible binary mixtures of the 16 β-blockers could be resolved fully (peak purity of the peak pairs, R>0.999), except practolol–sotalol ( R=0.992), nadolol–pindolol ( R=0.959), and esmolol–metoprolol ( R=0.956), which showed a small overlapping. The resolution of the individual peaks with the aqueous-organic mixtures was more problematic.

Quantitation of Antihistamines in Pharmaceutical Preparations by Liquid Chromatography with a Micellar Mobile Phase of Sodium Dodecyl Sulfate and Pentanol

A reversed-phase liquid chromatographic procedure with a micellar mobile phase of sodium dodecyl sulfate (SDS), containing a small amount of pentanol, was developed for the control of 7 antihistamines of diverse action in pharmaceutical preparations (tablets, capsules, powders, solutions, and syrups): azatadine, carbinoxamine, cyclizine, cyproheptadine, diphenhydramine, doxylamine, and tripelennamine. The retention times of the drugs were <9 min with a mobile phase of 0.15M SDS-6% (v/v) pentanol. The recoveries with respect to the declared compositions were in the range of 93-110%, and the intra- and interday repeatabilities and interday reproducibility were <1.2%. The results were similar to those obtained with a conventional 60 + 40 (v/v) methanol-water mixture, with the advantage of reduced toxicity, flammability, environmental impact, and cost of the micellar-pentanol solutions. The lower risk of evaporation of the organic solvent dissolved in the micellar solutions also increased the stability of the mobile phase.

Determination of active ingredients in cough–cold preparations by micellar liquid chromatography

The chromatographic behaviour of some active ingredients in cough–cold pharmaceutical preparations, the antihistamine chlorpheniramine (or the dextro enantiomer dexchlorpheniramine), and the phenethylamines phenylephrine, phenylpropanolamine and pseudoephedrine, has been studied using a C 18 column, micellar mobile phases of sodium dodecyl sulphate (SDS) and pentanol, and with UV detection. All possible combinations of chlorpheniramine/phenethylamine were resolved and determined using a mobile phase of 0.15 M SDS–6% (v/v) pentanol at pH 7, with analysis time below 7 min. Repeatabilities and within laboratory precisions were evaluated at four different drug concentrations in the range 0.5–25 μg ml −1 ( n=5), resulting RSDs below 1.6%. The drug amounts found in the analysis of 14 commercialised preparations agreed with those declared by the manufacturers within the tolerance limits, and with those obtained using an aqueous 60% (v/v) methanol reference mobile phase. No interference was observed from other accompanying drugs such as acetylsalicylic acid, ascorbic acid, betamethasone, caffeine, codeine phosphate, diphenhydramine, lactose, paracetamol, and prednisolone. The studied combinations required a rather high amount of methanol in conventional RPLC to be eluted from the column. In contrast, the proposed procedure used a much lower amount of organic solvent (pentanol), which is highly retained in the SDS solution, being also less toxic than methanol.

DETERMINATION OF STEROIDAL HORMONES IN URINE SAMPLES BY MICELLAR LIQUID CHROMATOGRAPHY FOLLOWING SOLID-PHASE EXTRACTION

Steroidal hormones were determined in spiked urine samples using micellar mobile phases of sodium dodecyl sulphate (SDS)-pentanol, solid-phase extraction (SPE), and detection in the UV region. In the optimized procedure, a 10 mL aliquot of urine sample is loaded into a C18 cartridge and washed with 2 mL of 50:50 (v/v) methanol-water, followed by 200 μL of 70:30 (v/v) methanol-water. The retained steroids are eluted with 2 mL of methanol and the eluate evaporated to dryness under nitrogen at 50°C. The residue is redissolved with 200 μL of the micellar mobile phase used in the chromatographic separation and injected into the chromatograph. The performance of the procedure was checked for 13 steroidal hormones: dehydrotestosterone, methandienone, methenolone enanthate, methyltestosterone, dydrogesterone, medroxyprogesterone, medroxyprogesterone acetate, nandrolone, nandrolone decanoate, progesterone, testosterone, testosterone enanthate, and testosterone propionate. Limits of detection were below 5 ng/mL for all steroids except nandrolone, nandrolone decanoate, and testosterone enanthate, whose elution from the SPE C18 column was not quantitative.

Resolution assessment and performance of several organic modifiers in hybrid micellar liquid chromatography

The performance of four criteria that measure the elementary resolution (modified selectivity, modified R S, peak purity, and orthogonal valley-to-peak ratio) was critically assessed using as global resolution function, the product of elementary measurements. The peak purities and valley-to-peak criteria yielded the best description of the overall separation according to the shape of the resolution surfaces compared to the peak arrangements in the chromatograms, the capability of defining unambiguously the composition regions of complete resolution, and the resolution achieved in the predicted optimums. Peak purities were used to compare the effect of five organic modifiers (1-propanol, 1-butanol, 1-pentanol, acetonitrile and tetrahydrofuran) on the separation quality of micellar mobile phases of sodium dodecyl sulphate (SDS). Acetonitrile, a common solvent in reversed should read reversed-phase liquid chromatography but scarcely used in micellar liquid chromatography, allowed the most satisfactory resolution in an extensive composition region with very small overlapping and sufficiently low retention times. The enhanced resolution was produced by the improved selectivity, and larger efficiencies and asymmetries of the chromatographic peaks.