Determination of petroleum sulfonates in crude oil by column-switching anion-exchange chromatography

A column-switching anion-exchange chromatography method was described for the separation and determination of petroleum monosulfonates （PMS） and petroleum disulfonates （PDS） in crude oil that was simply diluted with the dichloromethane/methanol （60/40）. The high performance liquid chromatography （HPLC） system consisted of a clean-up column and an analytical column, which were connected with two six-port switching valves. Detection of petroleum sulfonates was available and repeatable. This method has been successfully applied to determine PMS and PDS in crude oil samples from Shengli oil field.

Denatured Thermodynamics of Proteins in Weak Cation-exchange Chromatography

The thermostability of some proteins in weak cation-exchange chromatography was investigated at 20-80 ℃. The results show that there is a fixed thermal denaturation transition temperature for each protein. The appearance of the thermal transition temperature indicates that the conformations of the proteins are destroyed seriously. The thermal behavior of the proteins in weak cation-exchange and hydrophobic interaction chromatographies were compared in a wide temperature range. It was found that the proteins have a higher thermostability in a weak cation-exchange chromatography system. The thermodynamic parameters(Δ H 0, Δ S 0) of those proteins were determined by means of Vant Hoff relationship(ln k -1/ T ). According to standard entropy change(Δ S 0), the conformational change of the proteins was judged in the chromatographic process. The linear relationships between Δ H 0 and Δ S 0 can be used to evaluate 'compensation temperature'( β ) at the protein denaturation and identify the identity of the protein retention mechanism in weak cation-exchange chromatography.

Copper modified platinum electrode for amperometric detection of spectinomycin sulfate by anion-exchange chromatography

A La^3＋-Cu/Pt modified electrode was fabricated by electrodepositing process in CuS04 solution by adding a small amount of lanthium compound, and it was employed for direct current （DC） amperometric detection of spectinomycin by anion-exchange chromatography. Without derivatization, this method can simultaneously determine the main component and impurities in spectinomycin pharmaceutical raw material. Ease of preparation, being applied in DC detection mode and good catalytic stability confirmed the interests of this modified electrode as amperometric sensor for the determination of spectinomycin.

Impact of Hydrogen Ion Concentration on Amino Acids Composition of Macadamia Protein: Approached Using Cation-Exchange Chromatography

In the present context, the objective of this study was to synthesize and analyze the content of AA of macadamia protein and the impact of hydrogen ion concentration (pH) on AA composition. The determination of AA mainly by cation-exchange chromatography was also investigated. Reproducible and reliable techniques for quantification and identification of AA usually require derivatization. However, techniques such as AA analyzer are composed of cation-exchange chromatography and other components can sideline the derivatization with significant accuracy. The present analysis revealed a higher concentration of essential amino acids especially acidic AA, Glu and Asp and basic AA, Arg than other AA in macadamia protein. The study constitutes first report of use of bubble chart for evaluation of AA and explaination of AAS. The results may elaborate that the degradation of AA of macadamia protein for extraction of pH 11 is caused by the impact of pH. Moreover, the nutritional values of AA present in macadamia protein could change for the better by adjusting pH of extraction.

Study on the Separation of Co^(2+) from Zn^(2+) , Cd^(2+) by Anion-exchange Chromatography

The separation of Co 2+ from Zn 2+ , Cd 2+ by anion exchange chromatography was discussed. The chromatographic column containing anion resin 201×7 which was saturated with a solution of ammonium chloride. The effects of the eluant acidity and eluant composition on the separation were investigated. The results indicate that this anion exchange chromatography is suitable to the separation of Co 2+ from Zn 2+ , Cd 2+ , and the condition of separation is simple and convenient. When the column is saturated with NH 4Cl solution (2.0 mol/L, pH=4.0), the separation can be completed effectively. Zn 2+ and Cd 2+ can also be separa ted when different eluants are used and the pure solution with high concentration of Zn 2+ , Cd 2+ respectively can be obtained ea sily.

Refolding of reduced/denatured bovine pancreatic insulin with ion-exchange chromatography coupled with MALDI-TOF MS

The refolding of the reduced/denatured insulin from bovine pancreas as the model protein was investigated with weak anion exchange chromatography （WAX） coupled with MALDI-TOF MS. The results indicated that the disulfide bonds almost cannot be formed correctly with the common mobile phase by WAX. However, with the urea gradient elution and in the presence of GSSG/ Cyst as the ratio 1：6 in the mobile phase employed, the disulfide exchange of reduced/denatured insulin can be accelerated resulting in forming the correct three disulfide bonds. The protein refolding efficiency of reduced/denatured insulin can be increased from 3 % to 34%. The effects of urea gradient and the oxidant and reductant groups, such as GSSG/GSH, Cyst, and GSSG/Cyst, on the forming the disulfide bonds of reduced/denatured insulin were investigated in detail. The results were further tested by the separation of the WAX fraction of reduced/denatured insulin with RPLC and MALDI-TOF MS.

Effects of ion-exchange on the pervaporation performance and microstructure of NaY zeolite membrane

Pervaporation performance of NaY zeolite membranes is improved by ion-exchange with di-valent nitrate salt.Different nitrate salts,including Co(NO_(3))_(2),Mg(NO_(3))_(2),Zn(NO_(3))_(2),Ca(NO_(3))_(2),Cu(NO_(3))_(2),KNO_(3),and AgNO_(3),have great effects on the channel structure and water affinity of the NaY zeolite membrane.When the concentration of nitrate salt,ion-exchange temperature and time are 0.1 mol·L^(-1),50℃and 2 h,the ion-exchange degree order of NaY zeolites is Ag^(+)>K^(+)>Ca^(2+)>Zn^(2+)>>Co^(2+)>Mg^(2+).Especially,Ag^(+)and K^(+)cation exchange degree of NaY zeolites are achieved to 96.54% and 82.77% in this work.BET surface,total pore capacity,pore size distribution and water contact angle of the ion-exchanged NaY zeolites are all disordered by mono-and di-valent cations.Di-valent nitrate salt is favor for increasing the dehydration performance of NaY zeolite membranes by ion-exchange.When the ion-exchange solution is Zn(NO_(3))_(2),the total flux variation and separation factor variation of the NaY membrane(M-5)are -45% and 230% for separation of 10%(mass)H_(2)O/EtOH mixture by pervaporation,and the ion-exchanged membranes showed good reproducibility.

Mathematical modeling of salt-gradient ion-exchange simulated moving bed chromatography for protein separations

The salt-gradient operation mode used in ion-exchange simulated moving bed chromatography (SMBC) can improve the efficiency of protein separations. A detailed model that takes into account any kind of adsorption/ion-exchange equilibrium, salt gradient, size exclusion, mass transfer resistance, and port periodic switching mechanism, was developed to simulate the complex dynamics. The model predictions were verified by the experimental data on upward and downward gradients for protein separations reported in the literature. All design and operating parameters (number, configuration, length and diameter of columns, particle size, switching period, flow rates of feed, raffinate, desorbent and extract, protein concentrations in feed, different salt concentrations in desorbent and feed) can be chosen correctly by numerical simulation. This model can facilitate the design, operation, optimization, control and scale-up of salt-gradient ion-exchange SMBC for protein separations.

Purification of a Choleragenoid by Ion-exchange Chromatography

Abstract: Choleragenoid was obtained in pure form by ultra-filteration and fractionation on cationexchange resin-phospho-cellulose column. The choleragenoid was highly pure as judged by the electrophoresis of isoelectric focusing,immunization and SDS-gel electrophoresis.The results of test are thesame as that of the standard choleragenoid.Keywoeds:choleragenoid; vibrio cholerae; purification;ion-exchange; chromatography

Gas Chromatographic Method for Identification and Quantification of Commonly Used Residual Solvents in Pharmaceuticals Products

Background: Impurities are not expected in the final pharmaceutical products. All impurities should be regulated in both drug substances and drug products in accordance with pharmacopeias and ICH guidelines. Three different types of impurities are generally available in the pharmaceutical’s product specification: organic impurities, inorganic impurities, and residual solvents. Residual solvents are organic volatile chemicals used or generated during the manufacturing of drug substances or drug products. Purpose: The aim of this study is to develop a cost-effective gas chromatographic method for the identification and quantification of some commonly used solvents—methanol, acetone, isopropyl alcohol (IPA), methylene chloride, ethyl acetate, tetrahydrofuran (THF), benzene, toluene, and pyridine—in pharmaceutical product manufacturing. This method will be able to identify and quantify the multiple solvents within a single gas chromatographic procedure. Method: A gas chromatography (GC) equipped with a headspace sampler and a flame ionization detector, and a column DB 624, 30-meter-long × 0.32-millimeter internal diameter, 1,8 μm-thick, Brand-Agilent was used to develop this method. The initial GC oven temperature was 40°C and held for 5 minutes. It was then increase to 80˚C at a rate of 2˚C per minute, followed by a further increase to 225˚C at a rate of 30˚C per minute, with a final hold at 225˚C for 10 minutes. Nitrogen was used as a carrier gas at a flow rate of 1.20 mL per minute. Dimethyl sulfoxide (DMSO) was selected as sample solvent. Results: The developed method is precise and specific. The percent RSD for the areas of six replicate injections of this gas chromatographic method was within 10.0 and the recovery result found within 80.0% to 120.0%.

Simultaneous purification of minor components in natural products using twin-column recycling chromatography with a step solvent gradient

The isolation of minor components from complex natural product matrices presents a significant challenge in the field of purification science due to their low concentrations and the presence of structurally similar compounds.This study introduces an optimized twin-column recycling chromatography method for the efficient and simultaneous purification of these elusive constituents.By introducing water at a small flowing rate between the twin columns,a step solvent gradient is created,by which the leading edge of concentration band would migrate at a slower rate than the trailing edge as it flowing from the upstream to downstream column.Hence,the band broadening is counterbalanced,resulting in an enrichment effect for those minor components in separation process.Herein,two target substances,which showed similar peak position in high performance liquid chromatography(HPLC)and did not exceed 1.8%in crude paclitaxel were selected as target compounds for separation.By using the twin-column recycling chromatography with a step solvent gradient,a successful purification was achieved in getting the two with the purity almost 100%.We suggest this method is suitable for the separation of most components in natural produces,which shows higher precision and recovery rate compared with the common lab-operated separation ways for natural products(thin-layer chromatography and prep-HPLC).

Determination of 14 Organophosphorus Pesticide Residues in Mutton by Gel Permeation Chromatography-Gas Chromatography-Mass Spectrometry(GPC-GC-MS)

[Objectives]This study was conducted to purify mutton samples by gel permeation chromatography(GPC).[Methods]Fourteen organophosphorus pesticide residues in samples were qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry(GC-MS)in selective ion scanning mode(SIM).[Results]The organophosphorus pesticide standard solutions showed good linearity in the mass concentration range of 0.1-10.0μg/ml with correlation coefficients(r)not lower than 0.999,and the detection limits(S=3 N)ranged from 0.01 to 0.05 mg/kg.The average recovery values were in the range of 80.2%-99.7%,with relative standard deviations(RSDs,n=3)in the range of 1.8%-6.3%,at the addition levels of 0.5,1.0 and 2.0 mg/kg.[Conclusions]The method is simple,sensitive and accurate,and can be used for the determination of organophosphorus pesticide residues in mutton.

Comprehensive analysis of phenolic composition and antioxidant mechanisms in Gymnema sylvestre extracts using LC-MS and column chromatography

Recent studies have highlighted the potential of plant extracts as therapeutic agents for managing oxidative stress and related disorders.This study aims to elucidate the phenolic composition and antioxidant properties of Gymnema sylvestre extracts.Ethanolic reflux extraction followed by column chromatography was employed to isolate phenolic compounds.The total phenolic and flavonoid contents were quantified using the Folin–Ciocalteu and aluminum chloride colorimetric methods,respectively.Antioxidant activities were assessed by DPPH,ABTS scavenging assays and the ferric reducing antioxidant power(FRAP)assay.High-Performance Liquid Chromatography(HPLC)with a C18 column and Thermo TSQ Quantum Access Max(LC-MS)were used to determine the levels of gymnemic acid and identify other potential phenolic compounds.The analysis revealed significant antioxidant activities in the fractions.Fraction A showed the highest DPPH and ABTS scavenging activities,and Fraction C demonstrated the highest ferric reducing power.LC-MS analysis identified several phenolic compounds,indicating that these are major contributors to the antioxidant efficacy of the extract.This study provides a detailed phenolic profile and confirms the strong antioxidant potential of Gymnema sylvestre leaf extract,supporting its therapeutic use and further investigation.

Determination of Benzo[a]pyrene in Edible Oil by High Performance Liquid Chromatography-Fluorescence Detector (HPLC-FL)

In this study, an optimized high performance liquid chromatography-fluorescence detector (HPLC-FL) method for the determination of benzo[a]pyrene in edible oil was established. HPLC was performed with Thermo Fisher Scientific C18 column (250 mm×4.6 mm, 5 μm) as the chromatographic column and acetonitrile and water as the mobile phase, and the excitation wavelength and emission wavelength of fluorescence detector were 286 and 430 nm, respectively. The response was high, and the linear range was 0.5-10.0 ng/ml. The lowest limit of detection was 0.11 ng/ml, and the average recovery was 92.5%. This method is suitable for quantitative analysis of benzo[a]pyrene content in edible oil.

Cation-exchange high-performance liquid chromatography for variant hemoglobins and HbF/A2:What must hematopathologists know about methodology?

Cation-exchange high-performance liquid chromatography(CE-HPLC) is a widely used laboratory test to detect variant hemoglobins as well as quantify hemoglobins F and A2 for the diagnosis of thalassemia syndromes. It's versatility, speed, reproducibility and convenience have made CE-HPLC the method of choice to initially screen for hemoglobin disorders. Despite its popularity, several methodological aspects of the technology remain obscure to pathologists and this may have consequences in specific situations. This paper discusses the basic principles of the technique, the initial quality control steps and the interpretation of various controls and variables that are available on the instrument output. Subsequent sections are devoted to methodological considerations that arise during reporting of cases. For instance, common problems of misidentified peaks, totals crossing 100%, causes of total area being above or below acceptable limits and the importance of pre-integration region peaks are dealt with. Ultimately, CE-HPLC remains an investigation, the reporting of which combines in-depth knowledge of the biological basics with more than a working knowledge of the technological aspects of the technique.

Ion-Exchange Preparative Chromatography of Amino Acids

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Modified DIX model for ion-exchange equilibrium of L-phenylalanine on a strong cation-exchange resin

L-phenylalanine, one of the nine essential amino acids for the human body, is extensively used as an ingredient in food, pharmaceutical and nutrition industries. A suitable equilibrium model is required for purification of L-phenylalanine based on ion-exchange chromatography. In this work, the equilibrium uptake of L-phenylalanine on a strong acid-cation exchanger SH11 was investigated experimentally and theoretically. A modified Donnan ion-exchange （DIX） model, which takes the activiW into account, was established to predict the uptake of L-phenylalanine at various solution pH values. The model parameters including selectivity and mean activity coefficient in the resin phase are presented. The modified DIX model is in good agreement with the experimental data. The optimum operating pH value of 2.0, with the highest t-phenylalanine uptake on the resin, is predicted by the model. This basic information combined with the general mass transfer model will lay the foundation for the prediction of dynamic behavior of fixed bed separation process.

Purification of Lactic Acid by Heterogeneous Catalytic Distillation Using Ion-exchange Resins

The purification of lactic acid based on the esterification of raw lactic acid from fermentation broth and then the catalytic distillation hydrolysis of methyl lactate simultaneously to achieve pure lactic acid is reported. The esterification kinetics of lactic acid with methanol catalyzed by strong-acid cation-exchange resins (Amberlyst-15,D001, D002, NKC, 002) was studied under the condition that simulates the real catalytic environment. Experimental results were correlated by a Langmuir-Hinselwood model and the nonideality of the solution was taken into account by using activities calculated by the universal quasichemical functional group activity coefficient (UNIFAC) method.A good agreement between the model and the experimental data was achieved. Continuous purification experiments were conducted to find the optimum column configuration and operation condition for the system. The effects of various parameters, e.g. the length of different section of the column, feed rate and ratio of reactants, packing material and catalyst type, were studied. This novel system shows good separation results in lab scale, and is potential for industrial application.

Effective adsorptive denitrogenation from model fuels over yttrium ion-exchanged Y zeolite

The adsorption removal of indole and quinoline in octane with and without toluene over zeolites NaY and Yttrium Ion-exchanged Y(YY)using batch adsorption experiments was studied at 25℃and 0.1 MPa.YY was prepared by treating NaY with Y(NO3)3 solution twice via liquid ion-exchange method.NaY and YY were both characterized by XRD,SEM,N2 adsorption,XRF,NH3-TPD,and pyridine-FTIR techniques.Adsorption isotherms of indole,quinoline and toluene in octane were conducted at 25.0℃to explain the influence of toluene on nitrogen removal over NaY and YY.The partial destruct of the crystalline structure of NaY was observed after the introduction of yttrium ion,which led to an evident decline in BET surface area and pore volume of YY.Strong Br?nsted acidity and medium Lewis acidity were introduced by yttrium ion-exchange.Though the specific surface area and pore volume of YY were much lower than those of NaY,YY exhibited equivalent adsorption capacities for indole and quinoline as NaY in model fuels without toluene.In the presence of 20 vol%toluene,however,YY exhibited much higher adsorption capacities for indole and quinoline than NaY,especially in the case of quinoline.The improved toluene-tolerant of YY was ascribed to the strong acid–base interaction between YY and quinoline and the decreased adsorption strength between YY and toluene.

Tribological Properties of Magnesium Ion-exchanged α-Zirconium Phosphate as a Solid Lubricant Additive in Lithium Grease

Magnesium ion-exchanged a-zirconium phosphates(Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that larger particles of Mg-α-ZrP had a higher load-carrying capacity than that of smaller particles, whereas smaller Mg-α-ZrP particles had better anti-wear properties than that of larger Mg-α-ZrP particles under mild loads. The correlation between the particle size of the sample and the surface roughness of the friction pair thus seems to be a key factor influencing the performance.