Sodium Octanesulfonate Research Articles

Reversed-phase ion-pair high performance liquid chromatography with electrochemical detection for simultaneous quantification of neurotransmitters in mice brain tissues

An analytical method for the simultaneous quantification of neurotransmitters has been developed using reversed-phase ion-pair high performance liquid chromatography (RPIP-HPLC) coupled with electrochemical detection (ECD). As a strategy to simultaneously analyze acetylcholine, glutamate, and γ-aminobutyric acid, which were previously difficult to analyze in ECD, along with serotonin and dopamine, the ion pair separation technique was optimized, and electroactivity was induced by eluting with strong alkaline solution. This method achieved improved sensitivity, showing limits of quantification of 0.02 to 0.1 μg/mL and linear regression coefficients of determination of 0.9938–0.9994 through the use of an 8% acetonitrile solution containing 15 mM H3PO4 and 0.4 mM sodium 1-octanesulfonate as the mobile phase and 200 mM NaOH as the post-column eluent, detected at the gold electrode. All inter- and intra-day precision were below 4.10%, and the average recoveries were 97.43–103.69%. In an application comparing cerebral cortical tissues and hippocampal tissues between a control group and a scopolamine-treated group, the levels of the five components showed a clear difference. As a result of evaluating the eco-friendliness of this method, the Analytical GREEnness metric was determined as 0.47. Our method is expected to be useful in screening for neurotransmitters in various biological and clinical samples.

Elucidation of binding mechanisms of bovine serum albumin and 1-alkylsulfonates with different hydrophobic chain lengths

In this article, the binding interactions between bovine serum albumin (BSA) and three 1-alkylsulfonates, namely sodium 1-dodecanesulfonate, sodium 1-decanesulfonate, and sodium 1-octanesulfonate, have been thoroughly investigated. The study employed various experimental techniques such as isothermal titration calorimetry (ITC), steady-state fluorescence spectroscopy (SF), circular dichroism spectroscopy (CD), and molecular dynamics-based simulations. The objective was to understand the influence of the alkyl chain length of the investigated ligands on several aspects, including the strength of the interaction, the stoichiometry of the resulting complexes, the number of BSA binding sites, and the underlying mechanisms of binding. Notably, the study also demonstrated that sodium dodecyl sulfate (S12S) can serve as an effective site marker for BSA when studying ligands with similar structural and topological features. These findings may have significant implications for enhancing our understanding of the interactions between small amphiphilic molecules and proteins.

Can sodium 1-alkylsulfonates participate in the sodium dodecyl sulfate micelle formation?

The aggregation behavior of sodium dodecyl sulfate (SDS) was studied in an aqueous solution in the presence of increasing concentrations of selected sodium 1-alkylsulfonates, namely sodium 1-octanesulfonate, sodium 1-decanesulfonate, and sodium 1-dodecanesufonate. The critical micelle concentration (CMC) of SDS was determined by conductivity and fluorescence intensity measurements. The steady-state fluorescence quenching experiments with pyrene as a fluorescent probe were performed to obtain micellar aggregation numbers (Nagg) of the surfactant. The thermodynamic parameters of micellization (ΔGmic0 for all studied systems; ΔHmic0 and ΔSmic0 for sodium 1-dodecanesufonate) have been determined and compared. The influence of alkyl chain length and concentration of the selected sodium 1-alkylsulfonates on the values of CMC, Nagg, ΔGmic0, ΔHmic0, and ΔSmic0 of SDS has been discussed. As it was found, all selected for the experiments electrolytes decrease significantly the CMC of the surfactant, while an opposite effect is observed for Nagg values. The obtained experimental results have been supported by theoretical calculations. Interestingly, it has been proven that solely the molecules of sodium 1-dodecanesufonate (of the same carbon chain length) may act as the SDS mimetics – they are not recognized by SDS as the ones with a different structure and consequently are allowed to participate in the formation of the surfactant’s micelles.

Development and Validation of HPLC Method for Identification of Ramipril in Printed Tablets and Filaments

Introduction. 3D printing has shown its usefulness as a drug manufacturing technology over the past decade. However, the lack of regulated methods for quality control of finished printed drugs imposes a limitation on the widespread use of 3D printing methods in pharmaceutical practice. Thus, the development of methods for the analysis of printed dosage forms is of interest in pharmaceutical development.Aim. To develop a specific method for the determination of ramipril in filaments and printlets by HPLC.Materials and methods. Substance: ramipril. Excipients: Kollidon® VA 64, Kollidon® CL-F, PEG-1500, sodium carbonate anhydrous, Poloxamer-188, sodium stearyl fumarate. Reagents: hydrochloric acid, acetonitrile for ultra-HPLC, sodium octanesulfonate for HPLC, orthophosphoric acid 85 %, sodium perchlorate analytical grade, triethylamine. Standard: ramipril USP (No 1598303).Results and discussion. A special HPLC method in accordance with an ion-pair reagent (sodium octanesulfonate) for the determination of ramipril in the composition of filaments and printets was proposed.Conclusion. The developed chromatographic method should be adapted for ramipril release determination. This method can be used to quantify ramipril in further studies.

Three-dimensional printing of ramipril tablets by fused deposition modeling

Introduction. Arterial hypertension is one of the main risk factors for the development of cardiovascular diseases. Drug treatment of arterial hypertension is associated with a number of difficulties: often requires combination therapy, also a possible change in either dosages or drugs during treatment during the patient's life. Three-dimensional printing allows to create individual medicines on-demand.Aim. Study suitability of Kollidon® VA 64 as a matrix-polymer for the preparation of immediate release ramipril printing tablets.Materials and methods. Substance: ramipril; excipients: Kollidon® VA 64, Kollidon® CL-F, Soluplus®, PEG 1500, sodium carbonate anhydrous, Poloxamer 188, sodium stearyl fumarate, mannitol; reagents: hydrochloric acid, acetonitrile for ultra-HPLC, sodium octanesulfonate for HPLC, orthophosphoric acid 85 %, sodium perchlorate analytical grade, triethylamine, standard: ramipril USP (№1598303). Ramipril filaments were prepared by hot melt extrusion on the extruder Haake™ miniCTW (Thermo Fisher Scientific). The tablets were printed on a hand-made 3D printer. The printlets were studied for friability and hardness. Uniformity and quantitative determination of ramipril and impurities in tablets and filaments were determined by high performance liquid chromatography on a Shimadzu Prominence LC liquid chromatograph. Stability of ramipril was studied on a DSC 3+ Mettler Toledo by differential scanning calorimetry. Also, the stability of ramipril was determined by the Raman spectroscopy on an analytical system ORTES-785TRS-2700.Results and discussion. Ramipril filaments with a diameter of 1.75 mm were obtained by melt extrusion at a temperature of 105 °C. They were homogeneous in quantitative content of the active substance. From the resulting filaments, tablets were printed in five configurations with three filling densities: 30 %, 50 % and 100 %. Degradation of ramipril in filaments and tablets is not observed. The melting point of the selected mixture is lower than the melting point of matrix-polymer. It makes possible to lower the processing temperature. Tablets with 100 % filling provide an immediate release of ramipril.Conclusion. Kollidon® VA 64 is suitable as a matrix-polymer for the development of immediate release ramipril printlets. Kollidon® VA 64 provides the necessary physical and processing properties of the filament required for FDM printing.

Water-soluble pillar[4]arene[1]quinone: Synthesis, host-guest property and application in the fluorescence turn-on sensing of ethylenediamine in aqueous solution, organic solvent and air

Water-soluble pillar[5]arenes are a class of typical macrocycles and have aroused tremendous attention for its easy to modify, abundant host-guest properties and extensive applications. However, up to now, all the reported water-soluble pillar[5]arenes acted as the host molecules, whereas they failed to be postsynthetically modified, which seriously impeded the development of the pillar[5]arene-based supramolecular chemistry. In this work, a new water-soluble pillar[5]arene, pillar[4]arene[1]quinone, was designed and synthsized with eight quaternary ammonium groups as well as a quinone units. Such a new water-soluble pillar[4]arene[1]quinone was capable of forming 1:1 stable complex with sodium 1-octanesulfonate in aqueous solution. Since the 1,4-quinone unit of WP[4]Q[1] could react with ethylenediamine (EDA) to form a conjugated quinoxaline structure, so pillar[4]arene[1]quinone could apply to the facile fluorescence turn-on sensing of EDA in aqueous solution, organic solvent and air.

Assessing the perfluoroalkyl acid-induced swelling of Förster resonance energy transfer-capable poly(N-isopropylacrylamide) microgels.

As a method to combat the extensive contamination of poly- and perfluoroalkyl substances (PFAS) in water supplies, poly(N-isopropylacrylamide) (PNIPAM) microgels copolymerized with 2,2,2-trifluoroethylacrylate (TFEA) represent a potential sensing tool for recognizing PFAS at dilute aqueous concentrations. The microgels exhibit exceptional temperature responsiveness, transitioning from a swollen z-average diameter of 890.8 ± 19.8 nm to a collapsed diameter of 246.4 ± 10.3 nm below and above their lower critical solution temperature, respectively, for non-fluorinated gels, offering broad size fluctuations that are susceptible to coadded contaminants. Monitoring size perturbations as a function of analyte concentration, the polymers were observed to deswell in the presence of perfluorooctanoic acid, octanoic acid, phenol, and sodium 1-octane sulfonate while tetraethylammonium perfluorooctane sulfonate (TPFOS) augmented swelling. Adding up to 40 mol% TFEA to the networks lowered the concentration at which the microgels' normalized z-average diameter demonstrated a significant deviation from 0.25 mM to 0.1 mM for TPFOS, indicating fluorophilicity as a key contributor to the copolymers' associative capacity. Implanting Förster resonance energy transfer-compatible dyes, cyanine 3 and cyanine 5, into non-fluorinated microgels largely reiterated results from light scattering, as expected for the size-dependent energy transfer mechanism. Including dyes did, however, reinforce the customizability of this system, leaving windows open for functionalization with other signal transduction motifs to lower the detection limits of the polymer further. The swelling changes for PNIPAM microgels stimulated by the acidic constituents of PFAS highlight the polymer as a candidate for detecting the substances following additional development.

Application of achiral-chiral two-dimensional HPLC for separation of phenylalanine and tryptophan enantiomers in dietary supplement.

This study developed a two-dimensional heart-cutting LC method for the separation of amino acid enantiomers. Two approaches for achiral separation of amino acids, phenylalanine and tryptophan, were selected. Amino acids were separated on C18 or hydrophilic interaction liquid chromatography (HILIC) columns in first dimension after their enantiomer separation on a teicoplanin chiral column in second dimension. Mobile phases for both separation systems were optimized by testing different types of organic modifiers, concentrations of ion-pair agent (sodium 1-octanesulfonate), and ionic modifier (ammonium acetate). The resolution of enantiomers higher than 1.5 for both amino acids was achieved using a C18-teicoplanin coupled column separation system with mobile phases methanol/2 mM sodium 1-octanesulfonate (10:90 and 75:25, step gradient between achiral and chiral columns, respectively). The lower resolution of amino acid enantiomers (RS ˃ 0.9), but higher column efficiency, was achieved on a HILIC-teicoplanin separation system with mobile phases acetonitrile/50 mM ammonium acetate (90:10 and 80:20, step gradient between achiral and chiral columns, respectively). The developed heart-cutting 2D-LC methods were validated in terms of linearity, limit of detection, limit of quantification, precision, and accuracy. The results suggested that the developed methods were applicable for the simultaneous determination of amino acid enantiomers in the dietary supplement. The sample contained l-phenylalanine and l-tryptophan.

Determination of cotinine in human urine by high-performance liquid chromatography

A reversed-phase liquid chromatography with ultraviolet detection is described for the determination of cotinine. A mobile phase consisted of an acetate buffer with sodium octanesulfonate as an ion pair reagent and methanol was used to resolve cotinine from theobromine, theophylline, arecoline and nicotine. Using an octadecyl-type column, a good separation was achieved in 12 min. The wavelength of UV detector was set at 260 nm. With p-nitroaniline as internal standard, human urine samples were cleaned up by liquid-liquid extraction. The regression equations obtained from both the standard and the biological samples were linear between 0.1 - 10.0 μg/mL (r > 0.999). The detection limit for cotinine is 30.0 ng/mL. The R.S.D. and R.E. of intraday and interday are less than 3.93% and 3.07%, respectively (n = 6). The recoveries are all greater than 96.44%. This method has been successfully applied to the determination of urinary cotinine content in several heavy smokers.

Forced degradation studies of norepinephrine and epinephrine from dental anesthetics: Development of stability‐indicating HPLC method and in silico toxicity evaluation

Injectable solutions containing epinephrine (EPI) and norepinephrine (NE) are not stable, and their degradation is favored mainly by the oxidation of catechol moiety. As studies of these drugs under forced degradation conditions are scarce, herein, we report the identification of their degradation products (DP) in anesthetic formulations by the development of stability-indicating HPLC method. Finally, the risk assessment of the major degradation products was evaluated using in silico toxicity approach. HPLC method was developed to obtain a higher selectivity allowing adequate elution for both drugs and their DPs. The optimized conditions were developed using a C18 HPLC column, sodium 1-octanesulfonate, and methanol (80:20, v/v) as mobile phase, with a flow rate of 1.5 mL/min, UV detection at 199 nm. The analysis of standard solutions with these modifications resulted in greater retention time for EPI and NE, which allow the separation of these drugs from their respective DPs. Then, five DPs were identified and analyzed by in silico studies. Most of the DPs showed important alerts as hepatotoxicity and mutagenicity. To the best of our acknowledgment, this is the first report of a stability-indicating HPLC method that can be used with formulations containing catecholamines.

Quantitation of Four Tryptophan-Related Impurities in Compound Amino Acid Injection-18 AA by HPLC–PDA

Compound amino acid injection-18 AA (CAAI-18 AA) is widely applied in medical care as a part of total parenteral nutrition systems. Thus, suitable quality control of CAAI-18 AA is of crucial importance for safety of the patients. Tryptophan (TRP) is one of the main components in CAAI-18 AA and may be degraded to 5-hydroxy-tryptophan (5-HTP), 5-hydroxytryptamine (5-HT), kynurenine (KYN) and indole (IN) under certain conditions, such as oxidation environments, ultraviolet light radiation and nonsterile conditions. The existence of these harmful impurities seriously affects the quality of CAAI-18 AA. Here, a simple HPLC approach with a PDA detector was developed and validated for simultaneous determination of the concentrations of 5-HTP, 5-HT, KYN and IN impurities in CAAI-18 AA. Separation of these four impurities in CAAI-18 AA was achieved under a gradient condition using acetonitrile and 10 mM phosphate buffer (containing 10 mM sodium 1-octanesulfonate, pH adjusted to 1.8 with phosphoric acid). To detect the four analytes with high sensitivity, multi-wavelength detection at 257, 270 and 276 nm was carried out during the separation. The method was validated in accordance with ICH guidelines and the results were compared to that obtained by UHPLC–MS/MS, showing that the two approaches did not provide significantly different results. Our results reveal that the simple and less expensive HPLC method holds great potential for quantitation of the four impurities in CAAI-18 AA.

Reversed-phase ion-pair chromatography of hydroxyl functionalized imidazolium ionic liquid cations and its application in analysis of environmental water and measurement of hydrophobicity constants

A reversed-phase ion-pair chromatography with ultraviolet detection method for the determination of 1‑hydroxyethyl‑3‑methyl imidazolium cation ([HOEtMIm]+) and 1‑hydroxypropyl‑3‑methyl imidazolium cation ([HOPrMIm]+) was developed. The method has been applied to the analysis of hydroxyl functionalized imidazolium ionic liquid cations in Songhua River water samples and the determination of hydrophobicity constants. [HOEtMIm]+ and [HOPrMIm]+ were not completely separated in the reversed-phase chromatography, but complete separation was realized in the reversed-phase ion-pair chromatography. The effects of ion-pair reagents, organic solvents, column temperatures and ultraviolet detection wavelengths on the separation and detection of hydroxyl functionalized imidazolium ionic liquid cations in reversed-phase ion-pair chromatography were investigated. Ordinary imidazolium ionic liquids do not interfere with the determination of hydroxyl functionalized imidazolium ionic liquids. The suitable ion-pair reagent was sodium octanesulfonate. Using reversed-phase C18 chromatographic column, the mobile phase consisted of 0.5 mmol/L sodium octanesulfonate solution/methanol (85/15, v/v) with column temperature of 40 °C, ultraviolet detection wavelength of 210 nm and flow rate of 1.0 mL/min, [HOEtMIm]+ and [HOPrMIm]+ can be achieved baseline separation within 20 min. The detection limits were 0.36 and 0.50 mg/L, respectively. The relative standard deviations of peak area and retention time were less than 0.80%. Recoveries of sample addition were between 97.3% and100.5%. The method was simple, accurate, reliable, satisfying the requirement of quantitative analysis, and has good practicability.

A novel two-dimensional liquid chromatography - Mass spectrometry method for direct drug impurity identification from HPLC eluent containing ion-pairing reagent in mobile phases

In this study, a novel two dimensional liquid chromatography – mass spectrometry (2D-LC-MS) method with use of a weak anion exchange column between the 1st DLC RP column and the 2nd DLC RP column (RP1-WAX-RP2) was developed and applied to identify drug impurities from MS incompatible mobile phases containing sodium 1-octanesulfonate and non-volatile buffer. The 1st DLC conditions follow exactly the original standard HPLC method recorded in Chinese Pharmacopeia (ChP), European Pharmacopeia (EP) or US Pharmacopeia (USP). An impurity fraction was collected with a built-in sample loop (100 μL) and transferred to the WAX column where 1-octanesulfonate and phosphate were trapped and removed. While, the impurity and other cations were eluted to the 2nd D column (RP2) for separation and identification by connected IT-TOF MS. Methods were programmed and applied to identify impurities in two generic drugs, sulpiride (hydrophilic drug with logP 0.57) and dobutamine (hydrophobic drug with logP 3.6). The results indicate that the methods based on RP1-WAX-RP2 column configuration offer a feasible solution for direct impurity identification in generic drug product or API without needs of off-line desalting from the MS incompatible mobile phases containing ion-pairing reagent and non-volatile buffer.

Development of a novel ion-pairing UPLC method with cation-exchange solid-phase extraction for determination of free timolol in human plasma

A novel UPLC-UV method was developed for analysis of timolol in human plasma using a simple, fast, and cost effective ion-exchange SPE procedure, followed by separation on a C18 UPLC column with a mobile phase consisting of acetonitrile, phosphate buffer, and sodium 1-octane sulfonate as an ion pairing agent. The method was fully validated according to US-FDA guidelines, and was found to be sufficiently accurate and precise for analysis of timolol in human plasma for clinical pharmacokinetic studies. The application of ion-exchange SPE cartridges for purification of timolol in plasma produced excellent percent recoveries and good sample clean-up, while the ion-pairing separation described here allowed quantitation of timolol without interference from endogenous sample components. The method lower limit of detection was 1.7 ng/mL and the lower limit of quantitation was 5.0 ng/mL, allowing for analysis of therapeutic concentrations of timolol in plasma.

Experimental and Theoretical Studies of Anionic Surfactants Activity at Metal/Solution Interface: The Influence of Temperature and Hydrocarbon Chain Length of Surfactants on the Zinc Ions Electroreduction Rate

Abstract The effect of concentration of two anionic surfactants sodium 1-octanesulfonate and sodium 1-decanesulfonate in the temperature range 288–318 K on the kinetics and mechanism of electroreduction of Zn2+ ions was studied using electrochemical impedance spectroscopy (eis) and other electrochemical methods. It was found that the process of electroreduction proceeds in two steps. To describe the mechanism of Zn2+ amalgamation, the Fawcett’s models were considered: CE (chemical step C, electron transfer step E), IE (ion transfer step I, electron transfer step E) and IA (ion transfer step I, adsorption step A). The results of theoretical investigations suggest that the IE model is the most probable mechanism of the process. Both surfactants were found to exert a catalytic effect on the analyzed electrode process. The accelerating abilities of the surfactants were found to increase with the growth of the length of their hydrocarbon chain and with the increase of temperature. The observations concerning the mechanism of the electrode reaction and its acceleration caused by surfactants were confirmed by the parameters calculated from temperature dependencies.

Assay Development for Aminoglycosides by HPLC with Direct UV Detection.

The absence of UV chromophores in the structure of most aminoglycosides impedes an easy and straightforward development of analytical methods. It was demonstrated that addition of borate to the mobile phase allowed direct detection of aminoglycosides at the lower end of the UV spectrum. Although the borate ion complexes preferably with compounds possessing vicinal diols, the aim of this study was to develop an assay for tobramycin that does not contain vicinal diols in its structure. Amikacin, an aminoglycoside with a broad spectrum, was added to the study for its high therapeutic importance. An assay for both has been developed and validated. This method was developed on an XBridge C18 column (4.6 mm x 250 mm; 5 µm) and the mobile phase consisting of methanol-disodium tetraborate decahydrate buffer (0.1 M; pH=9.0)-water (20:20:60) supplemented with 1 g/L sodium octanesulfonate was run isocratically at a column temperature of 40°C. After validation according to International Conference on Harmonization guidelines, this method was tested on two commercially available pharmaceutical formulations, Amukin® and Tobrex®. The developed method was fast, accurate, easy to use and cheap as it did not require sophisticated equipment or tedious derivatization steps.

Impurity profiling of l-asparagine monohydrate by ion pair chromatography applying low wavelength UV detection

l-asparagine is a non-essential amino acid being used for a variety of pharmaceutical applications. The compound may be produced following synthetic or fermentative pathways leading to the formation of distinct impurities such as organic acids, other amino acids, dipeptides, or cyclic amino acid derivatives. Analysis of the respective analytes is challenging due to the lack of a chromophore, thus the monograph of the European Pharmacopoeia describes a thin layer chromatographic test for detection of other amino acids. Thus, a sensitive and robust liquid chromatographic method was developed and validated applying detection at 210nm for determining the related substances. Separation and quantification of the analytes was achieved on a reversed phase C18 column using a mobile phase composed of a mixture of a phosphate buffer, sodium octanesulfonate, and acetonitrile in an isocratic elution mode. In contrast to the currently used thin layer chromatographic test, the method is capable of separating and quantitatively assessing expected ninhydrin-positive and −negative impurities from synthetic and enzymatic production pathways.

Sodium Atom Emission from Aqueous Surfactant Solutions Exposed to Ultrasound.

Emission from electronically excited sodium atoms (Na*) was observed when argon saturated aqueous solutions of the anionic surfactants, sodium dodecyl sulfate, sodium octyl sulfate, sodium 1-pentanesulfonate, and sodium 1-octanesulfonate were sonicated using 358 kHz ultrasound. The same emission band, centered at about 590 nm, was also obtained in aqueous NaCl solutions, although a ∼100-fold higher concentration than that used for the surfactant solutions was required to obtain an emission of comparable intensity. The results have been interpreted in terms of the surfactant adsorbing at the gas-solution interface of the bubbles generated by the ultrasound, generating an electrostatic surface potential, and attracting Na+ counterions to the bubble surface. It is reasoned that Na+ ions are simultaneously reduced and electronically excited at the bubble-solution interface during the final stages of the collapse phase of the acoustically driven bubble. It is proposed that sodium ion bound water molecules reduce interfacial Na+ under the extreme, perhaps supercritical, conditions the interface experiences on bubble implosion.

Electrospray ion mobility mass spectrometry of positively and negatively charged (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide aggregates.

Self-assembling processes of surfactants in the gas phase constitute a developing research field of interest since they allow information to be gained on the peculiar structural organization of these aggregates, on their ability to incorporate from small molecules up to proteins and on their possible use as carriers of drugs in the gas phase or as cleaning agents and exotic reaction media. The mass spectra of charged aggregates of the chiral surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) in the gas phase have been recorded using a Synapt G2-Si mass spectrometer in the positive and negative ion mode. For comparison purposes, the mass spectra of sodium bis(2-ethylhexyl)sulfosuccinate and sodium octane sulfonate aggregates have also been recorded under the same experimental conditions. The collisional cross sections of positively and negatively charged DMEB aggregates were obtained through an appropriate calibration of the measured drift times. For all the surfactants investigated, it has been found that there is a lowest and a highest limit of the aggregation number at each charge state: no aggregates are found outside this range. Moreover, the occurrence at each aggregation number and extra charge of a unique value of drift time points toward aggregates whose conformations do not show discernible shape change in the experiment time scale. The analysis of the collisional cross sections emphasizes that the DMEB aggregates are nearly spherical clusters somewhat affected by the charge state and constituted by interlaced polar and apolar domains. The analysis of all the experimental findings indicates that in the gas phase DMEB forms supramolecular aggregates characterized by an internal organization whose stability is triggered by the charge state. The comparison of the behavior of DMEB aggregates with that of sodium bis(2-ethylhexyl)sulfosuccinate and sodium octane sulfonate aggregates allows us to highlight the effects on the aggregate organization in gas phase due to nature of the head group and alkyl chain steric hindrance.

Simultaneous Determination of Fangchinoline and Tetrandrine in Qi-Fang-Xi-Bi-Granules by RP-HPLC.

Knee Osteoarthritis is one of the most common diseases of elder worldwide. Qi-Fang-Xi-Bi-Granules (QFXBG) is a new Chinese medicine granules employed for the treatment of Knee Osteoarthritis. Fangchinoline (FAN) and tetrandrine (TET) are used as targets of quality control of QFXBG. A simple, practical high-performance liquid chromatographic method was developed for the simultaneous quantitation of FAN and TET in Stephaniae tetrandrae radix and QFXBG. The analysis was performed on a Athena C18 column (250 × 4.6 mm, 5 µm) with mobile phase of methanol-water (65 : 35, v/v, pH 3.0, adjusted by glacial acetic acid) containing 1.0 g/L sodium 1-octanesulfonate. This method was validated in terms of linearity, precision, accuracy and recovery. Results showed that this method had good linearity with R(2) at >0.999. The limit of detection and limit of quantification for FAN were 0.13 and 0.35 mg/L, while for TET were 0.28 and 0.76 mg/L, respectively. The relative standard deviations of precision were 0.1-1.3% for intraday and 0.5-2.4% for interday. The recovery was 94.56-98.81% of FAN and 94.07-99.12% of TET, respectively. The chromatographic analytical time was 14 min. This method was successfully applied for the quantitative analysis of FAN and TET in Stephaniae tetrandrae radix and QFXBG, so that it could be extended to quality control of QFXGB in commercial.