sodium-acetate--anhydrous and acetonitrile

Mixed-mode chromatographic materials are more and more often used for the purification of biomolecules, such as peptides and proteins. In many instances they in fact exhibit better selectivity values and therefore improve the purification efficiency compared to classical materials. In this work, a model to describe biomolecules retention in cation-exchange/reversed-phase (CIEX-RP) mixed-mode columns under diluted conditions has been developed. The model accounts for the effect of the salt and organic modifier concentration on the biomolecule Henry coefficient through three parameters: α, β and γ. The α parameter is related to the adsorption strength and ligand density, β represents the number of organic modifier molecules necessary to displace one adsorbed biomolecule and γ represents the number of salt molecules necessary to desorb one biomolecule. The latter parameter is strictly related to the number of charges on the biomolecule surface interacting with the ion-exchange ligands and it is shown experimentally that its value is close to the biomolecule net charge. The model reliability has been validated by a large set of experimental data including retention times of two different peptides (goserelin and insulin) on five columns: a reversed-phase C8 column and four CIEX-RP columns with different percentages of sulfonic groups and various concentration values of the salt and organic modifier. It has been found that the percentage of sulfonic groups on the surface strongly affects the peptides adsorption strength, and in particular, in the cases investigated, a CIEX ligand density around 0.04μmol/m(2) leads to optimal retention values.

Topics: Acetonitriles; Adsorption; Cations; Chromatography, Ion Exchange; Chromatography, Reverse-Phase; Hydrogen-Ion Concentration; Insulin; Models, Chemical; Peptides; Sodium Acetate; Sulfur Compounds

A sensitive and reproducible high-performance liquid chromatography-fluorescence method was developed and validated for quantitative determination of indoxyl sulfate in plasma using methyl paraben as an internal standard. The separation was carried out on an OSD-2 C18 Spherisorb column by isocratic elusion with sodium acetate buffer (pH 4.5) and acetonitrile (10:90, v/v) as the mobile phase. The method was validated and found to be linear in the range of 2.5 to 50 µM. The limit of quantification was 2.0 µM. The variations for intra-day and inter-day precision were less than 10.1%, and the accuracy values were between 93.4 and 102.5%. The extraction recoveries were more than 89%.

Topics: Acetonitriles; Chromatography, High Pressure Liquid; Humans; Indican; Parabens; Reproducibility of Results; Sensitivity and Specificity; Sodium Acetate; Spectrometry, Fluorescence

Eight textile dye compounds including five cationic dyes, namely, basic blue 41, basic blue 9, basic green 4, basic violet 16 and basic violet 3, and three anionic dyes, acid green 25, acid red 1 and acid blue 324, were separated and detected by non-aqueous capillary electrophoresis (NACE) with electrochemical detection. Simultaneous separations of acid and basic dyes were performed using an acetonitrile-based buffer. Particular attention was paid to the determination of basic textile dyes. The optimized electrophoresis buffer for the separation of basic dyes was a solvent mixture of acetonitrile/methanol (75:25, v/v) containing 1 M acetic acid and 10 mM sodium acetate. The limits of detection for the basic dyes were in the range of 0.1-0.7 microg mL(-1). An appropriate solid-phase extraction procedure was developed for the pre-treatment of aqueous samples with different matrices. This analytical approach was successfully applied to various water samples including river and lake water which were spiked with textile dyes.

Topics: Acetic Acid; Acetonitriles; Buffers; Coloring Agents; Electrochemistry; Electrophoresis, Capillary; Methanol; Reproducibility of Results; Sensitivity and Specificity; Sodium Acetate; Solid Phase Extraction; Solvents; Textiles; Water

An immunoglobulin (IgG) preparation with micro-amount of histamine fixed on the active protein fraction has been used to increase the resistance to allergic reactions. However, excessive histamine may cause hypo- or hypertension, headache, or anaphylactic shock and so the histamine content of the drug is strictly controlled by a regulation: 0.15 microg of histamine dihydrochloride is allowed for 12 mg of immunoglobulin. In this study, a liquid chromatographic method to determine micro-amount of histamine in the pharmaceutical was developed and validated. This method include a sample cleanup by a solid phase extraction (SPE) using a polystyrene-divinyl benzene (PS-DVB) polymeric sorbent and high-performance liquid chromatography after precolumn fluorescent labeling of the histamine with o-phthaldialdehyde. The drug sample was loaded to the SPE cartridge after adjusting to pH 9.5. After successive washings of the cartridge with water and 30% aqueous methanol, histamine was then eluted with 100 mM sodium acetate (pH 9.5)-methanol (20:80, v/v). An aliquot from the eluate was labeled with o-phthaldialdehyde-mercaptoethanol (OPA-ME) for fluorescence detection at the excitation maximum of 340 nm and emission maximum of 450 nm. HPLC analysis was performed on a phenyl-hexyl column with an acetonitrile-phosphate buffer (pH 6.8; 50 microM) (35:65, v/v) as the mobile phase. The retention times of histamine and 3-methylhistamine (IS) were approximately 7.2 and 9.5 min, respectively. The quantitation range was between 0.01-0.2 mg/mL of histamine showing good linearity (r=0.9996). This analytical method would provide a potential mean for the strict control of histamine content in the pharmaceutical product.

Topics: Acetonitriles; Anti-Allergic Agents; Buffers; Calibration; Chromatography, High Pressure Liquid; Histamine; Hydrogen-Ion Concentration; Immunoglobulin G; Indicators and Reagents; Ion Exchange Resins; Mercaptoethanol; Methanol; Methylhistamines; o-Phthalaldehyde; Polystyrenes; Quality Control; Reproducibility of Results; Sodium Acetate; Solid Phase Extraction; Solvents; Spectrometry, Fluorescence

Paclitaxel, a unique antimitotic chemotherapy agent that inhibits cell division by binding to microtubules and prevents them from "depolymerizing," has received widespread interest because of its efficacy in fighting certain types of cancer, including breast and ovarian cancer. Paclitaxel undergoes aggregation at millimolar concentrations in both aqueous media and solvents of low polarity (mimicking hydrophobic environments). Its aggregation may have impact on its aqueous stability and its ability to stabilize microtubules. Here, we investigated the dimerization phenomenon of paclitaxel by electrospray ionization mass spectrometry (ESI-MS). Paclitaxel dimers were stable in solutions of acetonitrile/aqueous ammonium acetate (80/20) and aqueous sodium acetate/acetonitrile (92/8 or 95/5) at various pH values. Additional experiments using solution-phase hydrogen/deuterium exchange were employed to ascertain whether or not the observed dimers were formed in solution or as an artifact of the ESI process by ion-molecule reaction. The evidence supports formation of the dimer in solution, and the approach used can be extended to investigation of other types of drug-drug interactions.

Topics: Acetates; Acetonitriles; Antineoplastic Agents, Phytogenic; Dimerization; Drug Stability; Hydrogen-Ion Concentration; Paclitaxel; Sodium Acetate; Solutions; Solvents; Spectrometry, Mass, Electrospray Ionization

Non-aqueous capillary electrophoresis was used to study the separation selectivity of positively charged drug substances and negatively charged diuretics. Study was made of the effects of organic solvent composition and the background electrolyte on the separation. The separation selectivity could be altered considerably by varying the methanol/acetonitrile composition. In addition, the migration order and the resolution of the pharmaceuticals could be altered merely by changing the electrolyte cation or the anion. The electrolytes tested were alkali metal acetates, ammonium acetate, ammonium chloride and ammonium bromide. As with aqueous background electrolyte solutions, the electroosmotic flow was decreased with increasing size of the alkali metal cation of the electrolyte in methanol/acetonitrile 50:50 (v/v).

Topics: Acetates; Acetonitriles; Ammonium Chloride; Bromides; Dextromoramide; Dose-Response Relationship, Drug; Electrolytes; Electrophoresis, Capillary; Ephedrine; Hydrogen-Ion Concentration; Levorphanol; Lithium Compounds; Methadone; Methanol; Morphine; Potassium Acetate; Quaternary Ammonium Compounds; Sodium Acetate; Time Factors; Viscosity

A single-solvent extraction step high-performance liquid chromatographic method is described for quantitating zolpidem in rat serum microsamples (50 microl). The separation used a 2.1 mm I.D. reversed-phase OD-5-100 C18 column, 5 microm particle size with an isocratic mobile phase consisting of methanol-acetonitrile-26 mM sodium acetate buffer (adjusted to pH 2.0 with 40% phosphoric acid) containing 0.26 mM tetrabutylammonium phosphate (13:10:77, v/v/v). The detection limit was 3 ng/ml for zolpidem using an ultraviolet detector operated at 240 nm. The recovery was greater than 87% with analysis performed in 12 min. The method is simple, rapid, and applicable to pharmacokinetic studies of zolpidem after administering two intravenous bolus doses (1 and 4 mg/kg) in rats.

Topics: Acetonitriles; Animals; Buffers; Chromatography, High Pressure Liquid; Hydrogen-Ion Concentration; Hypnotics and Sedatives; Male; Methanol; Microchemistry; Pyridines; Quality Control; Rats; Rats, Sprague-Dawley; Sensitivity and Specificity; Sodium Acetate; Zolpidem

Paracetamol is a safe drug which has been used as an in-vivo probe to determine phase II metabolism in a HIV+/AIDS population. Due to the biohazard nature of HIV-infected samples, a high performance liquid chromatography (HPLC) assay which offers minimal sample manipulation and maximal specificity was developed. This reverse-phase HPLC method uses wavelength-switching UV detection for the simultaneous determination of paracetamol and its glucuronide and sulfate metabolites in HIV-infected urine samples. The solvent systems involves a simple isocratic elution with a composition of 50 mM sodium acetate buffer, pH adjusted to 3.5; acetonitrile (96:4 v/v) modified with 0.35% trifluroacetic acid. The validated method is highly reproducible with an inter-assay variation of < 7%. This method also shows good precision and sensitivity, making it an ideal assay for phenotyping studies to determine the extent of glucurondiation and sulfation activities.

Topics: Acetaminophen; Acetonitriles; Acquired Immunodeficiency Syndrome; Chromatography, High Pressure Liquid; Glucuronates; HIV Seropositivity; Humans; Hydrogen-Ion Concentration; Phenotype; Reproducibility of Results; Sensitivity and Specificity; Sodium Acetate; Sulfates; Trifluoroacetic Acid; Ultraviolet Rays