TLC-Densitometric Method for Quantification of Oxaprozin and its Degradation Products in Pharmaceutical Preparations

JPC – Journal of Planar Chromatography – Modern TLC - A new, simple and rapid thin-layer chromatographic method with densitometric detection has been developed and validated for...     

Separation of Chlordane Residues From Aroclor 1248, 1254 and 1260 and Soil Degradation Products

Abstract

Polychlorinated biphenyls often occur simultaneously in environmental samples complicating the identification and quantification of chlordane. A method is presented for the separation of chlordane and two of its metabolites from several polychlorinated biphenyl mixtures. Soil samples were subjected to controlled environments so that degradation of PCB residues could be followed over a period of 10 months in order to examine interference to the method by PCB degradation products.     

Separation and Quantitation of Urinary Phthalates by HPLC

Abstract

A method was developed for the separation and quantitation of plasticizers and their metabolites from human urine using HPLC, Urine was diluted with an equal volume of water and extracted at pH 2.0 with diethyl ether, The extract was dried, the solvent vacuum stripped, and the residue dissolved in methanol for injection into the chromatograph. A C₁₈ reverse phase column containing 10 μ particles was used for the analysis. Ionic suppression, 0.5% acetic acid in water, at pH 3.0 was used to resolve the acidic components. A step gradient of acetonitri1e:water (containing acetic acid) was used to elute the polar metabolites as well as the non-polar plasticizers. Mass spectrometry was used t o identify the compounds in the HPLC fractions. From the HPLC fractions of the urine extract collected, phthalic acid, MEHP, DEHP and normal urinary constituents (e.g., hippuric and benzoic acid derivatives) were identified     

Environmental Analysis of Cypermethrin and its Degradation Products After Forestry Applications

Abstract

Cypermethrin and alphamethrin ([1R, cis, αS]- and [1S, cis, αR]-cypermethrin) are pyrethroid insecticides used in agriculture, forestry, and public health hygiene. After forestry applications of cypermethrin against bark beetles diastereo- and enantioselective analyses of pyrethroid residues are performed by gas chromatography (GC) with electron capture (ECD) and mass spectrometric (MS) detection, or by achiral and chiral high performance liquid chromatography (HPLC). The major soil metabolites of cypermethrin, i.e. 2,2-dimethyl-3-(1,1-dichlorovinyl)-cyclopropylic acid and 3-phenoxybenzoic acid, are analyzed as methyl esters by GC-MS with electron-impact (EI) ionization. On spruce bark cypermethrin persists several months as surface films of 1 μg/cm^2. In soil it is detected as long as seven months after treatment at levels of 0.15–0.7 μg/g. Sunlight-induced cis, trans isomerization on bark and leaves results in an excess of trans-cypermethrin isomers. In soil cis-cypermethrin isomers are more persistent than their corresponding trans-isomers. Enantioselective HPLC demonstrates chiral discrimination of a pair of trans-cypermethrin enantiomers. Analysis of soil metabolites is less meaningful since traces of the investigated products are formed from pyrethroid residues during the extraction and derivatization procedures.     

苯丙醇胺对映体的毛细管电泳分离和定量

采用环糊精及其衍生物作为手性选择对苯丙醇胺对映体进行了分离,研究了环糊精种类和浓度对分离的影响。结果表明,采用２,６－０－二甲基－β－环糊精（ＤＭ－β－ＣＤ）可以使苯丙醇胺对映体达到基线分离。在选定的条件下,考察了苯丙醇 的定量线性范围、检测限和重现性,测得苯丙醇胺的线性范围为２０～２００ｍｇ／Ｌ,检测限为１ｍｇ／Ｌ迁移时间重现性的ＲＳＤ为１．０％,峰面积重现性的ＲＳＤ小于３．５％,并对康泰克实样     

Validated High-Performance Thin-Layer Chromatographic Method for Quantitation of Fluvoxamine in the Presence of Degradation Products Formed under ICH Recommended Stress Conditions

JPC – Journal of Planar Chromatography – Modern TLC - This paper describes a sensitive, selective, precise, and stability-indicating high-performance thin-layer chromatographic method...     

Separation and Characterization of New Forced Degradation Products of Macitentan: A Dual Endothelin Receptor Antagonist

Macitentan (MCT) is an endothelin receptor antagonist used for the treatment of pulmonary arterial hypertension. In the present study, MCT was subjected to forced degradation as per ICH guidelines. The drug degraded extensively in acidic, basic as well as neutral hydrolytic conditions and seven degradation products (DPs) were formed. All these DPs were selectively separated using high-performance liquid chromatography (HPLC) with a stationary phase of Inertsil C₁₈ column (150 × 4.6 mm, 5 μm) and a mobile phase consisting of gradient mixture of 0.02% trifluoroacetic acid (TFA) and acetonitrile (ACN). The developed HPLC method was transferred to LC–ESI–QTOF–MS/MS for identification of DPs. The final mass spectrometric conditions were optimized for better ionization of drug and DPs with optimum mass signal sensitivity. All the formed DPs were new and well separated with sufficient resolution. The developed HPLC method was validated as per ICH-guidelines and can be used in drug testing labs for determination of quality of MCT in bulk and finished formulations.     

Separation of Chlorophylls and Their Degradation Products using Packed Column Supercritical Fluid Chromatography (SFC)

Complex mixtures of chlorophyll degradation products may arise during processing and storage of vegetable oil and green plant materials like broccoli and spinach. Determination of these compounds is important in the area of food chemistry. Therefore a method using packed column supercritical fluid chromatography (SFC) has been developed. The method comprises chromatography using a simple gradient of methanol in carbon dioxide at constant column back pressure of 30 MPa and a column temperature of 40°C. Effects of pressure and mobile phase composition showed the importance of applying a modifier gradient for optimal separation of the chlorophyll products. The method permits separation of 15 chlorophyll derivatives including chlorophyll a and b, pheophytins, and pyropheophytins on a C₁₈ column in about 20 minutes. Identifications of the individual peaks were based on reference compounds, the retention order of the compounds, and their absorption spectra.     

苯乙醇胺对映体的毛细管电泳分离和定量的研究

选用β＿环糊精及其衍生物作为手性选择剂对苯乙醇胺对映体进行了分离,研究了环糊精种类、浓度、电泳缓冲液pH值对分离的影响。结果表明,采用β＿羟丙基环糊精(HP＿β＿CD)可以使苯乙醇胺对映体达到基线分离。在选定条件下,考察了苯乙醇胺的定量线性范围、检出限和回收率,测得苯乙醇胺的线性范围为20～200mg／L,检出限为1mg／L,(R)＿苯乙醇胺和(S)＿苯乙醇胺回收率分别为(101.37±3.04)%(RSD为0.60%)和(98.08±3.10)%(RSD为0.63%)(n＝5),并对Arthrobactersp.BW1010全细胞转化苯乙胺酮合成(S)＿苯乙醇胺的过程进行了监测。     

GLC and HPLC Determination of Diazepam and its Degradation Products in Pharmaceutical formulations

Abstract

Stability-indicating high performance liquid chromatographic (HPLC) and gas-liquid chromatographic (GLC) assays for diazepam in pharmaceutical formulations are described. In HPLC method, the material is extracted with 5 % aqueous methanol and chromatographed on a dimethyloctyl stationary phase using methanol-water-acetic acid (80: 20: 1) and propyl paraben internal standard. The system separated diazepam from the main degradation products, desmethyl diazepam (a synthetic precursor of diazepam) and the excipients present in ampoules and syrups. The GLC method included the extraction of diazepam and 2-methylamino-5-chiorobenzo-phenone (MACB) from aqueous acidic solution into chloro form leaving the other degradation products in the aqueous phase. The chloroform extract is evaporated to dryness, dissolved in chloroform containing diethylhexyl phtha-late as internal standard and chromatographed on an OV-17 stationary phase using flame ionisation detector. The results are compared with the BP method described for each formulation.     

Selection of A Suitable Solvent System for the Separation and Quantitation of Histamine

Abstract

The suitability of 79:21, 85:15 and, 90:10 of phosphate buffer: 50% methanol, as mobile phases, to separate and quantitate histamine in small plasma volume (<300 μl) was investigated by using a Dionex BioLC System coupled to a pulsed amperometric detector. Also, special attempts were made to reduce the time of analysis of each sample. Methylhistamine was used as an internal standard. the best results were obtained with the 79:21 mobile phase with concommittant reduction in analysis time from the current 1 sample per 90 min to 5 samples per 60 min suggesting that the method is suitable and cost effective.     

Chiral HPLC Separation of Rosiglitazone and its Main Metabolites and Studies on Their Racemization

Rosiglitazone (RSG) is marketed as a racemic mixture although the antidiabetic activity is essentially related to the (S)-enantiomer. The chiral center has an adjacent carbonyl group; therefore, the (R)-enantiomer could be transformed to the (S)-enantiomer or vice versa by keto-enolic tautomerism. The literature indicates that this racemization is slow enough to allow the evaluation of the properties of the isolated enantiomers. However, there is no information about the enantioselective kinetic disposition and metabolism of RSG. Additionally, there are no studies on the racemization of its metabolites. Considering these facts, a chiral HPLC method was developed and used for the first time to study the racemization of RSG and its main metabolites. Different conditions, including those used to evaluate the in vitro enantioselective metabolism, were employed. The simultaneous chiral separation of RSG and metabolites was achieved on a Chiralcel OJ-H column by employing methanol/ethanol (90:10, v/v) as mobile phase. The racemization studies showed that the half-life of RSG decreased more than 30 times when the temperature increased from 4 to 37 °C. It was also observed that the half-life of RSG changed from approximately 20 h at pH 3.5 to approximately 2 h at pH 7.4. The same profile was observed for its metabolites. Organic solvents and UV light did not present influence on the racemization process. In addition, a Complete Factorial Design was conducted to evaluate the influence of some parameters that can be changed during an in vitro metabolism study. The results obtained showed that the racemization occurs under in vitro metabolism conditions.

     

Chiral HPLC Separation of Rosiglitazone and its Main Metabolites and Studies on Their Racemization

Rosiglitazone (RSG) is marketed as a racemic mixture although the antidiabetic activity is essentially related to the (S)-enantiomer. The chiral center has an adjacent carbonyl group; therefore, the (R)-enantiomer could be transformed to the (S)-enantiomer or vice versa by keto-enolic tautomerism. The literature indicates that this racemization is slow enough to allow the evaluation of the properties of the isolated enantiomers. However, there is no information about the enantioselective kinetic disposition and metabolism of RSG. Additionally, there are no studies on the racemization of its metabolites. Considering these facts, a chiral HPLC method was developed and used for the first time to study the racemization of RSG and its main metabolites. Different conditions, including those used to evaluate the in vitro enantioselective metabolism, were employed. The simultaneous chiral separation of RSG and metabolites was achieved on a Chiralcel OJ-H column by employing methanol/ethanol (90:10, v/v) as mobile phase. The racemization studies showed that the half-life of RSG decreased more than 30 times when the temperature increased from 4 to 37 °C. It was also observed that the half-life of RSG changed from approximately 20 h at pH 3.5 to approximately 2 h at pH 7.4. The same profile was observed for its metabolites. Organic solvents and UV light did not present influence on the racemization process. In addition, a Complete Factorial Design was conducted to evaluate the influence of some parameters that can be changed during an in vitro metabolism study. The results obtained showed that the racemization occurs under in vitro metabolism conditions.     

Identification and Determination of Nicorandil and its Degradation Products by HPLC and GC/MS

Nicorandil [N-(2-hydroxyethyl)-nicotinamide nitrate NIC] is a novel kind of compound in the treatment of angina pectoris. NIC can be degraded easily in storage. The degradation products include N-(2-hydroxyethy) nicotinamide (HN), nitrate ion (NI), and ni…     

生物质的液化转化及其产物的分离分析实验设计

设计了一个综合性化学实验——生物质的液化转化及其产物的分离分析。实验内容包括生物质（麦秆）的醇解液化;气/液/固产物的收集与分离,以及用气相色谱仪、气相质谱联用仪、红外光谱仪和热重分析仪等对产物成分与结构的检测与表征;液体产物（生物油）的萃取与柱层析分离,以提取苯乙酮、2,6-二甲氧基苯酚等高附加值化学品。该实验从社会能源现状出发,使学生的理论知识与实际应用相结合,可以激发学生对于新能源化学的兴趣;实验中涉及到多种分离纯化手段的运用和产物分析仪器的使用,提高了学生基本实验技能、动手操作能力和数据处理能力;同时鼓励学生进行知识拓展,进行创新方案设计。     

Syntheses of Potential Degradation Products of Phenylephrine in OTC Products

Compound 1 and 2 are potential major degradants in over the counter (OTC) products containing phenylephrine HCl and dexbrompheniramine maleate or chlorpheniramine maleate. Compound 2 matches the unknown peak in the solution of stressed active and excipient and thus was identified as the correct degradation product. Whether the degradation product is racemic or chiral is not known. This article describes synthesis of both compounds. Compound 2 will be useful as an analytical standard for quantitative analysis of the major degradant in OTC products of phenylephrine HCl and dexbrompheniramine maleate or chlorpheniramine maleate.     

Determination of Ibandronate and its Degradation Products by Ion-Pair RP LC with Evaporative Light-Scattering Detection

A simple method has been developed for analysis of ibandronate and related substances by ion-pair reversed-phase high-performance liquid chromatography (RPIC) with evaporative light-scattering detection (ELSD). After optimization of the chromatographic conditions satisfactory separation of the compounds was achieved on an Intersil C₈ column with an isocratic mobile phase—8:4:88 (v/v) acetonitrile–methanol–12 mM ammonium acetate buffer containing 35 mM n-amylamine (pH 7.0). The mobile phase flow rate was 1.0 mL min^?1. The calibration plot was linear in the range 352 to 1760 µg mL^?1 for ibandronate. The precision and reproducibility were 0.3% and 0.5%, respectively. The average recovery of ibandronate was 100.4% and RSD was 0.6%. The method was validated and shown to be precise, accurate, and specific for assay of ibandronate in bulk material and dosage forms. The proposed liquid chromatographic method can be satisfactorily used for quality control of ibandronate.     

Preparation and Use of a Boronic Acid Affinity Support for Separation and Quantitation of Glycosylated Hemoglobins

Abstract

Cross-linked agarose activated with carbonyl diimidazole and subsequently coupled to aminophenyl boronic acid provides a highly efficient matrix for separation and quantitation of glycosylated hemoglobins The method described is highly reproducible. rapid and flexible in that it can be adapted to column or batch formats The method can tolerate moderate fluctuations in temperature and pH of buffeused without significantly altering results Hemoglobin fractions separated by this affinity support were Subjected to isoelectric focusing which revealed a heterogeneous population of glucose modified proteins.     

Spectrophotometric Determination Of Rifampin in the Presence of its Degradation Products in Pharmaceutical Preparations

Abstract

The determination of rifampin in the presence of its main degradation products, 3-formyl rifampin and rifampin quinone using two spectrophotometric methods is described. Both Glenn's method and first derivative spectrophotometry were successfully adopted. No preliminary separation steps were required in either cases. Both methods gave accurate and reproducible results for the determination of the drug in dosage forms. The percentage recoveries ranged from 99.33% ±0.63 to 100.2% ± 0.44. The proposed methods are more simple, rapid than other existing methods and can be readily adopted in control laboratory.