Sodium Hexanesulfonate Research Articles

Development of Methods of Quality Control of the Tablets «Ramipril»

Our main target was to develop methods for the quality control of the tablet «ramipril» according to the indicators of «Quantitative determination», «Impurities» and «Dissolution». New, precise, accurate and green HPLC methods were developed for the determination of ramipril and its impurities in tablets. The separation was accomplished using a diode array detector at 210 nm with an isocratic and gradient mobile phase consisting of a 0.2 g/L solution of sodium hexanesulfonate (pH 2.7) and the acetonitrile and chromatographic columns Acclaim 120 C18 and Inertsil ODS-3. The developed method was validated in accordance with ICH guidelines. The analysis of impurities was performed within a run duration of less than 25 min, which is about a two times shorter than that of the official Ph. Eur. method. The analysis of ramipril in tablets was performed with a run duration of less than 4.5 min, which is about three times shorter than that of the official USP method. The developed methods were successfully applied for the quality control of the tablet «ramipril» according to the indicators of «Quantitative determination», «Impurities» and «Dissolution». In addition, they proved its superiority over the reported methods in terms of greenness using different assessment tools.

Development of a rapid and reliable high-performance liquid chromatography method for determination of water-soluble vitamins in veterinary feed premix.

Background and Aim:Determination of trace amounts of vitamins in multi-component feed premix is a troublesome analytical procedure. In this study, a simple and rapid high-performance liquid chromatography (HPLC) method was developed and validated for the concurrent detection and quantitation of four water-soluble vitamins such as thiamine, riboflavin, pyridoxine, and cyanocobalamin in veterinary feed premixes.Materials and Methods:The chromatographic separation of the vitamins was carried out at 35°C temperature on a reversed-phase C18 column using a gradient pump mode. Mobile phase constituents were solvent (a): 25 mM Potassium dihydrogen phosphate and 5 mM sodium hexanesulfonate in deionized water having pH-4.0 and solvent and (b) 5 mM sodium hexanesulfonate in methanol. Detection was performed with HPLC ultraviolet/visible detection set at 278 and 361 nm wavelength in two different channels. The flow rate was 1.2 mL/min and the total run time was 25 min.Results:The method was validated according to the International Conference on Harmonization and Food and Drug Administration guidelines and acceptance criteria for system suitability, precision, linearity, and recovery were met in all cases. The relative standard deviation for system suitability and precision was <2% for all vitamins. The linearity of the calibration curves was excellent (R2>0.999) at concentration of 5, 10, 15, 20, 25, and 30 μg/mL for all vitamins. The limits of detection values were 0.0125, 0.0017, 0.0064, and 0.0065 μg/mL for thiamine, riboflavin, pyridoxine, and cyanocobalamin, respectively, and the limits of quantification values were 0.0378, 0.0051, 0.0213, and 0.0198 μg/mL for thiamine, riboflavin, pyridoxine, and cyanocobalamin, respectively. The recovery percentages ranged from 88% to 115%.Conclusion:The overall parameters of the proposed method met the validation criteria and this method could be a highly desirable technique for routine analysis of water-soluble vitamins in veterinary feed premix.

The physicochemical and fire extinguishing performance of aqueous film‐forming foams based on a class of short‐chain fluorinated surfactants

AbstractAqueous film‐forming foams (AFFFs) are an important for fire extinguishing, and their key ingredient is fluorinated surfactant. In recent years, traditional long‐chain fluorinated surfactants have been banned by most countries because of their persistence, bio‐accumulation and toxicity. Therefore, increased attention has been paid to the research and development of short‐chain fluorinated surfactants. As is well known, the introduction of hydrophilic or hydrophobic groups in a surfactant affects its surface activity, and therefore, the fire extinguishing performance of AFFFs. In this work, a series of short‐chain fluorosurfactant‐based AFFFs with different hydrophobic chain lengths were prepared. The physicochemical performance of mixed systems (fluorinated surfactant plus sodium hexanesulfonate), including surface activity, spreading ability, foam expansion, drainage time, and the fire extinguishing and burn‐back performance of AFFFs were studied. The results show that the critical micelle concentration (CMC) and the surface tension (γCMC) at the CMC of mixed systems at 25°C are lower than 7.68 mmol/L and 16.51 mN/m, respectively. For mixed systems, the average spreading rate is more than 1.09 cm/s, the foam expansion is over 7.1, and the drainage time is greater than 3.28 min. The fire extinguishing time of AFFFs on fuels is less than 51 s while the burn‐back time is more than 15.18 min. The results imply a potential application prospect of the short‐chain fluorinated surfactants in AFFFs.

Implementation of Total Error Perception in the Analytical Method Validation for Quantification of Related Substance in Pharmaceutical Formulation

<p style="text-align: justify;"><strong>Objectives:</strong> This study is initiated to develop a simple and reproducible liquid chromatographic method with ultraviolet detection for the estimation of Sisomicin in Gentamicin pharmaceutical formulation by application of total error statistical tool. <strong>Methods:</strong> Gentamicin has a weak UV chromophore it is not possible to detect low levels of known related substance of gentamicin using a UV detector. Hence derivatization technique was applied to detect those substances. Chromatographic separation was accomplished by using Thermo scientific Hypersil Gold column (150 x 4.6 mm) and 5&mu;m particle size as stationary phase by isocratic elution with Methanol: Water: Glacial acetic acid: Sodium hexane sulfonate in the ratio 70:25:5:3% v/v/ v/w as mobile phase. Sisomicin was detected at 330 nm within 25 min with a flow rate of 0.5 mL/min. <strong>Results: </strong>Concurrent results were obtained in the developed analytical method based on total error measurement. Proposed method showed good linearity response (r&gt; 0.995) with limit of quantification at 0.007495 mg/mL, % relative standard deviation less than 1% in repeatability and % recovery was found within 96 to 98 % in accuracy. Accuracy profile result found within the range of &plusmn;10% and risk profile &plusmn;5% between the two set. <strong>Conclusion:</strong> This method can separate all the analogues of Gentamicin including known related substances. The finding demonstrated that method could be suitable for quantification of related substances in parental liquid dosage form. <p style="text-align: justify;"><strong>Key words:</strong> Gentamicin, Ultra violet detection, Liquid chromatography, Related substance, Quantification.

Ion pair assisted micro matrix solid phase dispersion extraction of alkaloids from medical plant

A novel micro matrix solid phase dispersion method was successfully used for the extraction of quaternary alkaloids in Phellodendri chinensis cortex. The elution of target compounds was accomplished with sodium hexanesulfonate as the eluent solvent. A neutral ion pair was formed between ion-pairing reagent and positively charged alkaloids in this process, which was beneficial for selectively extraction of polar alkaloids. Several parameters were optimized and the optimal conditions were listed as follows: silica gel as the sorbent, silica to sample mass ratio of 1:1, the grinding time of 1min. The exhaustive elution of targets was achieved by 200µL methanol/water (9:1) containing 150mM sodium hexane sulfonate at pH 4.5. The method validation covered linearity, recovery, precision of intraday and interday, limits of detection, limits of quantitation, and repeatability. This established method was rapid, simple, environmentally friendly, and highly sensitive.

Comprehensive stability-indicating high-performance liquid chromatography coupled with diode array detection method for simultaneous determination of amprolium hydrochloride and ethopabate in powder dosage form for veterinary use.

This research deals with the development of a stability-indicating high-performance liquid chromatography method for simultaneous determination of amprolium hydrochloride and ethopabate. To the best of our knowledge, no comprehensive stability-indicating method has been reported for analysis of this mixture. Separation was achieved using Kromasil cyano column with gradient elution of the mobile phase composed of sodium hexane sulfonate solution and methanol. Quantification was based on measuring peak areas at 266nm. Amprolium and ethopabate peaks eluted at retention times 10.42 and 18.53min, respectively. The proposed procedure was validated with respect to system suitability, linearity, ranges, precision, accuracy, specificity, robustness, detection, and quantification limits. Linearity ranges for amprolium and ethopabate were 1.5-240 and 1-160μg/mL, respectively. Analytes were subjected to stress conditions of hydrolysis, oxidation and thermal degradation. The proposed method enabled resolution of drugs from their forced-degradation products and amprolium related substance (2-picoline). Moreover, specificity was verified by resolution of the analytes from about 22 drugs used in antimicrobial veterinary products. The validated method was successfully applied to assay of the combined veterinary powder dosage form, additionally it was implemented in the accelerated stability study of the dosage form when stored for six months at 40°C and 75% relative humidity.

Pharmacokinetic Properties of Arsenic Species after Intravenous and Intragastrical Administration of Arsenic Trioxide Solution in Cynomolgus Macaques Using HPLC-ICP-MS.

A rapid and sensitive method was established for arsenic (As) speciation based on high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). This method was validated for the quantification of four arsenic species, including arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV) in cynomolgus macaque plasma. Separation was achieved in just 3.7 min with an alkyl reverse phase column and highly aqueous mobile phase containing 20 mM citric acid and 5 mM sodium hexanesulfonate (pH = 4.3). The calibration curves were linear over the range of 5–500 ng·mL−1 (measured as As), with r > 0.99. The above method was validated for selectivity, precision, accuracy, matrix effect, recovery, carryover effect and stability, and applied in a comparative pharmacokinetic study of arsenic species in cynomolgus macaque samples following intravenous and intragastrical administration of arsenic trioxide solution (0.80 mg·kg−1; 0.61 mg·kg−1 of arsenic); in addition, the absolute oral bioavailability of the active ingredient AsIII of arsenic trioxide in cynomolgus macaque samples was derived as 60.9 ± 16.1%.

DEVELOPMENT OF A HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY METHOD FOR ANALYZING DISODIUM 5′-GUANYLATE AND DISODIUM 5′-INOSINATE LEVELS IN FLAVOR ENHANCERS

Objective: This study aimed to develop a selective analytical method for assessing disodium 5′-guanylate and disodium 5′-inosinate levels in flavorenhancers.Methods: The levels were assessed using high-performance liquid chromatography (HPLC) with a photodiode array detector (PDA) (wavelength=255 nm) and a SunFire® C18 column (250 mm × 4.6 mm × 5 μm). The mobile phase comprised a mixture of potassium phosphate buffer and anion pair reagent-hexane-1-sulfonic acid sodium salt - with a flow rate of 1.2 mL/min. The ion pair was used to generate a neutral equilibrium, whichresulted in increased retention of the analytes. Optimized analysis conditions were then validated regarding accuracy, precision, linearity, selectivity,and the limits of detection and quantification.Results: The average levels of disodium 5′-inosinate in the six analyzed samples were 0.24±1.46, 0.21±2.69, 0.58±3.26, 0.21±0.84, 0.22±3.59, and0.47±2.21%, respectively. Regarding disodium 5′-guanylate, the average levels were 0.15±2.85, 0.15±0.12, 0.41±3.80, 0.16±1.72, 0.27±1.18, and0.34±1.83, respectively.Conclusion: The optimal conditions for analyzing disodium 5′-guanylate and disodium 5′-inosinateusing HPLC with a PDA and SunFire C18 columnwere λ=255 nm, a mobile phase of potassium phosphate buffer and sodium hexane sulfonate, and a flow rate of 1.2 mL/min. For disodium 5′-inosinate,its average levels in samples A–F were 0.24±1.46, 0.21±2.69, 0.58±3.26, 0.21±0.84, 0.22±3.59, and 0.47±2.21%, respectively. Meanwhile, the averagelevels of disodium 5′-guanylate in the samples were 0.15±2.85, 0.15±0.12, 0.41±3.80, 0.16±1.72, 0.27±1.18, and 0.34±1.83%, respectively.

Development and validation of a micellar electrokinetic capillary chromatography method for the determination of goserelin and related substances.

An MEKC method for the analysis of goserelin and related substances has been developed using a combination of additives including CTAB, β-CD, and sodium hexanesulfonate. For this assay, the running buffer (pH and additives) and separation conditions (voltage and temperature) were optimized. The optimized system was the following: 200 mM 6-aminocaproic acid buffer (pH 4.2) supplemented with 175 mM CTAB, 3.0% w/v β-CD, and 20 mM sodium hexanesulfonate; the voltage was 10 kV in reverse polarity mode, the temperature was 20°C, and UV detection was measured at 220 nm. The method was qualified by evaluating the specificity, precision, linearity, accuracy, LOD, and LOQ. According to validation experiments, the optimized method was specific, accurate, and repeatable and satisfied the requirements for the analysis of goserelin and related substances. Compared with the RP-HPLC method, the MEKC method better solved the problem of overlapping impurity signals, and the migration time required was shorter. This method can be used for quality control and for the analysis of goserelin and its related substances.

Novel Solid-Phase Extraction for Epimer-Specific Quantitation of Ergot Alkaloids in Rye Flour and Wheat Germ Oil

Ergot alkaloids and their epimer-specific determination have gained increasing importance for food safety. A solid-phase extraction and cleanup method based on sodium-neutralized strong cation exchange (Na(+)-SCX) was developed to quantitate 12 priority ergot alkaloids in rye flour and wheat germ oil by HPLC fluorescence analysis. Sample preparation is achieved by omitting acidic and alkaline conditions enabling minimized epimerization, which is necessary to determine ergot alkaloids according to their natural distribution in foods. Ergot alkaloids are eluted from SCX-column by forming ion pairs using a sodium hexanesulfonate containing solution which prevents epimerization for at least 96 h. Method validation yielded recoveries of 80-120% (rye flour) and 71-96% (wheat germ oil) with a maximum limit of quantitation (LOQ) of 2.0 μg kg(-1) per ergot alkaloid for both matrices. The applicability of the developed method was demonstrated by analyzing 16 samples from German retail markets: 9 rye flours (max 178 ± 5 μg kg(-1)) and, reported for the first time, 7 wheat germ oils (max 56.8 ± 2.7 μg kg(-1)) expressed as the sum of 12 ergot alkaloids.

SIMULTANEOUS DETERMINATION AND PHARMACOKINETIC STUDY OF AMLODIPINE AND VALSARTAN IN RAT PLASMA USING ION-PAIR HPLC WITH FLUORESCENCE DETECTION

A simple, selective, and sensitive high-performance liquid chromatographic method is described for the simultaneous determination of amlodipine and valsartan combined tablets in rat plasma, using losartan as internal standard. The assay was based on protein precipitation with acetonitrile then reversed phase chromatography with fluorescence detection. In order to delay the rapid elution of amlodipine and to obtain acceptable relative retention value, sodium hexane sulfonate was used as ion pairing reagent and a gradient elution mode was applied. The separation was performed on an Agilent Zorbax Eclipse XDB C18 column, using gradient elution with aqueous 0.02% sodium hexane sulfonate–glacial acetic acid (500:1,v/v) (solvent A) and acetonitrile (solvent B). The fluorescence detector was on-line switched to measure each analyte and internal standard at their optimum excitation and emission wavelengths. The assay was linear over the concentration ranges 0.01–0.80 and 0.10–20 µg/mL for amlodipine and valsartan, respectively, with recoveries of 97.80 and 99.35%, respectively. The method was successfully applied to a pharmacokinetic study involving a single oral dose of combined (10/160 mg) tablet.

RP-LC and TLC Densitometric Determination of Paracetamol and Pamabrom in Presence of Hazardous Impurity of Paracetamol and Application to Pharmaceuticals

Two simple, accurate and reproducible methods were developed and validated for the simultaneous determination of paracetamol (PARA) and pamabrom (PAMB) in pure form and in tablets. The first method was based on reserved-phase high-performance liquid chromatography, on a Thermo Hypersil ODS column using methanol:0.01 M sodium hexane sulfonate:formic acid (67.5:212.5:1 v/v/v) as the mobile phase. The flow rate was 2 mL/min and the column temperature was adjusted to 35 °C. Quantification was achieved with UV detection at 277 nm over concentration range of 100–600 and 4–24 μg/mL, with mean percentage recoveries were found to be 99.90 ± 0.586 and 99.26 ± 0.901 for PARA and PAMB, respectively. The second method was based on thin-layer chromatography separation of PARA and PAMB followed by densitometric measurement of the spots at 254 nm and 277 nm for PARA and PAMB respectively. Separation was carried out on aluminum sheet of silica gel 60F254 using dichloromethane:methanol:glacial acetic acid (7.5:1:0.5 v/v/v) as the mobile phase over concentration range of 1–10 and 0.32–3.20 μg per spot, with mean percentage recovery of 100.52 ± 1.332 and 99.71 ± 1.478 for PARA and PAMB, respectively. The methods retained their accuracy in presence of up to 50% of P-aminophenol and could be successfully applied in tablets.

HPLC 및 ESI-tandom Mass Spectrometry를 이용한 인터넷에서 판매되는 기능성표방식품 중 부정유해물질 모니터링

인터넷에서 판매되는 건강기능성표방식품 51개를 구매하여 발기부전치료제 5종과 그 유사물질 29종, 이카린, 요힘빈, 시부트라민 그리고 시부트라민 유사물질인 데스메틸시부트라민, 디데스메틸시부트라민 총 39종의 부정유해물질을 3개의 혼합표준용액으로 만든 후 HPLC를 이용하여 총 50분 동안 이동상 용액 A(5 mM sodium hexanesulfonate와 0.1% phosphoric acid을 함유한 물), B(95% acetonitrile) 두 가지를 기울기 용매 조건으로 분석하였다. 검출된 화합물의 확인을 위하여 LC-ESI-tandom MS의 MRM 조건을 최적화하고 정성분석 한 결과 1개의 홍삼제품과 영양보충용제품 2건에서 실데나필과 슈도바데나필, 디메틸티오실데나필성분이 1회 복용량당 1.3-82.1 mg 검출되었으며, 2개의 기타가공품에서 부작용이 우려되어 사용이 금지된 시부트라민의 유사물질인 디데스메틸시부트라민이 각각 1회 복용량 당 2.2, 1.7 mg이 검출되었다. 시중에 판매되는 비아그라의 실데나필 1회 최소복용량은 25 mg으로 시료에서의 검출량은 이보다 높은 수준으로 함유되었으며, 의사의 처방 없이 식품 중에 불법적으로 함유된 이들 물질 혹은 이들의 유사물질은 소비자들의 건강상에 문제를 일으킬 수 있으므로, 시중에 유통되는, 더욱이 온라인 상에서 음성적으로 판매되고 있는 건강관련식품에 대한 모니터링이 지속적으로 필요한 실정이다. It was carried out to detect anti-impotence drug-like compounds, sibutramine and their analogues in dietary supplements, which are doubtful whether they include illegal compounds. A total of 51 food products were bought online and have been investigated. The separation was achieved on a C18 column, with the mobile phase made up of water (5 mM sodium hexanesulfonate and 0.1% phosphoric acid) and 95% acetonitrile, at a flow rate of 1.2 mL/min with gradient elution using by HPLC-DAD. The UV signals were monitored at 220 nm and 291 nm. LC-ESI-tandom MS was utilized to confirm that detected compounds in samples are the same as the reference materials. Two nutrient supplement foods and ginseng products were found to contain 1.3-82.1 mg of sildenafil, dimethylthiolsildenafil and pseudovardenafil per serving size. In addition, two other processed products were detected to contain 1.7 and 2.2 mg of didesmethylsibutramine, derived from sibutramine per serving size.

Organic Solvent-Free Reversed-Phase Ion-Pairing Liquid Chromatography Coupled to Atomic Fluorescence Spectrometry for Organoarsenic Species Determination in Several Matrices

A novel method has been developed to determine As-containing animal feed additives including roxarsone (ROX), p-arsanilic acid (p-ASA) and nitarsone (NIT), as well as other organic As species (dimethylarsonic acid (DMAA) and monomethylarsonic acid (MMAA)) by ion-pairing high-performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry (IP-HPLC-HG-AFS). A simple isocratic reversed-phase (RP) HPLC method with a mobile phase containing citric acid and sodium hexanesulfonate (pH 2.0) was developed using a C(18) column. The use of an organic solvent free mobile phase turns this methodology into an environmentally friendly alternative. Several ion pair forming agents, such as sodium hexanesulfonate, tetrabutylammonium bisulfate and perfluoroheptanoic acid, were studied. The limits of detection for As species were calculated in standard solution and resulted to be 0.2, 0.5, 0.6, 1.6, and 1.6 μg As L(-1) for MMAA, DMAA, p-ASA, ROX and NIT, respectively. This method exhibited convenient operation, high sensitivity and good repeatability. It was applied to As speciation in different samples including arugula, dog food, dog urine and chicken liver.

Ion-pair LC–UV Method for the Determination of Boanmycin in Mouse Plasma and Its Application to a Pharmacokinetic Study

An ion-pair LC–UV detection assay was developed for the determination of boanmycin (BAM) in mouse plasma. The mobile phase contained methanol, acetonitrile, 0.055 M sodium hexanesulfonate and 0.08 M acetic acid in water, with a flow rate of 0.8 mL min−1. This assay involved a rapid and simple extraction process and subsequent detection at 291 nm. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.04 and 0.09 μg mL−1, respectively. Using bleomycin (BLM A5) as the internal standard, the assay was linear over the concentration range from 0.1 to 30 μg mL−1 (r2 > 0.99). The extraction recovery of BAM in mouse plasma was >66.5%, and the intra- and inter-day accuracy and precision were ≤7.5%. The assay was successfully applied to a pharmacokinetic study after intravenous injection of BAM (40 mg kg−1) to mice.

Determination of Boanmycin in Pharmaceutical Preparations by a Simple and Rapid Ion-pair LC Method

An ion-pair HPLC method with UV detection is described for the determination of boanmycin in freeze-dried pharmaceutical preparations. Chromatographic separation was achieved on a 5 μm Agilent Eclipse XDB-C18 column (150 × 4.6 mm). The mobile phase contained methanol, acetonitrile, 055 M sodium hexanesulfonate and 0.08 M acetic acid in water. UV detection was at 291 nm. The assay was validated over a linear concentration range from 0.05 to 120 μg mL−1. The method was applied to determine the content of BAM in freeze-dried powders.

Analysis of methylene blue in human urine by capillary electrophoresis

A capillary electrophoresis method for the determination of the dye methylene blue (tetramethylthionine, MB) in human urine depending on liquid/liquid-extraction and diode array detection has been developed, validated, and applied to samples of healthy individuals, who had been dosed with methylene blue within clinical studies. After extraction with dichloromethane and sodium hexanesulfonate, sample extracts were measured on an extended light path capillary. The dye was detected simultaneously at 292 and 592 nm using methylene violet 3 RAX as internal standard. The limit of quantification was 1.0 microg/ml. The accuracy of the method varied between -15.2 and +0.8% and the precision ranged from 2.0 to 12.0%. The method was linear at least within 1.0 and 60 microg/ml. In contrast to earlier indirect determinations no leuco methylene blue (LMB) was directly detected in urine, whereas in aqueous test solutions containing surplus amounts of ascorbic acid leuco methylene blue was well separated from MB in a single run.

Chiral CE Separation of Dopamine-Derived Neurotoxins

An enantiomeric separation of dopamine-derived neurotoxins by capillary electrophoresis has been developed. Tetrahydroisoquinoline (TIQ), dopamine (DA), (R/S)-1-benzyl-TIQ (BTIQ), (R/S)-6,7-dihydroxy-1-methyl-TIQ (salsolinol, Sal), and (R/S)-6,7-dihydroxy-1, 2-dimethyl-TIQ (N-methyl-salsolinol, NMSal) were studied as model compounds. The CE running buffer (50 mM phosphate buffer at pH 3.0) contained 1.5 M urea and 12 mM beta-CD as a chiral selector. During separation, the (R)-enantiomers formed more stable inclusion complexes with beta-CD, and thus had a longer migration time than their optical antipodes. It was noticed that the recovery rates of these TIQ derivatives were very poor (< 15%) during protein precipitation, a procedure widely used for cleaning up biological samples. The recovery was significantly improved by pre-mixing the sample with a surfactant (e.g., sodium hexanesulfonate or Triton X-100) to reduce the co-precipitation. The present method in combination with electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to study samples obtained from in vitro incubation of two catecholamines, dopamine and epinine, with aldehydes forming neurotoxins including (S)- and (R)-NMSal enantiomers. The later is known to induce Parkinsonism in rats.

Effects of detergent alkyl chain length and chemical structure on the properties of a micelle-bound bacterial membrane targeting peptide

The effects of phospholipid or detergent chain length on the structure and translational diffusion coefficient of the membrane-targeting peptide corresponding to the N-terminal amphipathic sequence of Escherichia coli enzyme IIA Glc were investigated by nuclear magnetic resonance (NMR) spectroscopy. Three anionic phospholipids (dihexanoyl phosphatidylglycerol, dioctanoyl phosphatidylglycerol, and didecanoyl phosphatidylglycerol) and four lipid-mimicking anionic detergents (sodium hexanesulfonate, 2,2-dimethyl-silapentane-5-sulfonate, sodium nonanesulfonate, and sodium dodecylsulfate) were evaluated. In all cases, the cationic peptide adopts an amphipathic helical structure. While the chain length of the two-chain phospholipids has a negligible effect on the peptide conformation, the effect of chain length of those single-chain detergents on the helix length is more pronounced. The diffusion coefficients of the peptide/micelle complexes were found to correlate with the chain lengths of both the lipid and the detergent groups. Taken together, short-chain anionic phospholipids are proposed to be useful membrane-mimetic models for the structural elucidation of membrane-binding peptides such as cationic antimicrobial peptides. DSS does not form micelles by itself according to the diffusion coefficient data, but it does associate with this cationic peptide. Consequently, both DSS and its analog may be chosen as NMR chemical shift reference compounds depending on the nature of the biomolecules under investigation.

Simultaneous determination of nicotinamide, pyridoxine hydrochloride, thiamine mononitrate and riboflavin in multivitamin with minerals tablets by reversed-phase ion-pair high performance liquid chromatography.

A reversed-phase ion-pair high performance liquid chromatographic method (HPLC) has been developed and validated for the routine analysis of nicotinamide, pyridoxine hydrochloride, thiamine mononitrate and riboflavin in multivitamin with minerals tablets. HPLC separation of the vitamins was performed on a Hypersil C(18) column and detected by ultraviolet absorbance at 280 nm. The use of methanol-aqueous 0.5% acetic acid solution (18:82, v/v; containing 2.5 mM sodium hexanesulfonate, pH = 2.8) as the mobile phase at a flow-rate of 1.2 mL/min enables the baseline separation of the four analytes free from interferences with isocratic elution at 30 degrees C. The analysis time was 17 min per injection. The method was linear in the ranges of 5-90, 2.5-90, 5-95 and 25-450 micro g/mL for thiamine mononitrate, riboflavin, pyridoxine hydrochloride and nicotinamide, respectively. The average coefficients of variation of within- and between-day assays were 2.2 and 3.6% for thiamine mononitrate, 1.8 and 2.4% for riboflavin, 1.3 and 1.7% for pyridoxine hydrochloride and 1.0 and 1.5% for nicotinamide, respectively. The average recoveries of thiamine mononitrate, riboflavin, pyridoxine hydrochloride and nicotinamide were 97.0, 97.2, 98.9 and 100.4% for the tablets, respectively. The method has been successfully applied to the simultaneous determination of nicotinamide, pyridoxine hydrochloride, thiamine mononitrate and riboflavin in multivitamin with minerals tablets.