Separation and Direct Chemical Determination of Nitrosamines by High Performance Liquid Chromatography (HPLC)

Abstract

Volatile and non-volatile nitrosamines are determined at subparts per million levels in a continuous, inexpensive, low-temperature procedure when samples are compatible with the aqueous-alcoholic solvents. Individual nitrosamines are resolved by gradient elution on appropriate HPLC columns, converted to nitrite ion by ultra-violet light, combined with modified Griess reagent and the red-colored product measured at 540 nanometers. Inorganic nitrite may be determined and two, organic compounds are known to interfere. The detection level for N-nitrosodimethyl amine is 0.1 parts per million.     

Quantitative yields of underivatized peptides by HPLC

New methods for peptide separation are being developed. Resolution of peptide mixtures on HPLC with good reproducibility indicates the progress that has already been made in development of supports with useful separation capabilities. At present adsorptive characteristics of the stationary phases may place limitations on the applicability of the technique to underivatized peptides. Hopefully, the application of ionpairing techniques and the development of new support materials will expand the range of application for protein and peptide purification.     

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     

HPLC法拆分粉唑醇对映体

HPLC法拆分粉唑醇对映体;粉唑醇;对映体;分离;手性固定相     

Analytical Separation of Closantel Enantiomers by HPLC

Closantel is an antiparasitic drug marketed in a racemic form with one chiral center. It is meaningful to develop a method for separating and analyzing the closantel enantiomers. In this work, two enantiomeric separation methods of closantel were explored by normal-phase high-performance liquid chromatography. The influences of the chiral stationary phase (CSP) structure, the mobile phase composition, the nature and proportion of different mobile phase modifiers (alcohols and acids), and the column temperature on the enantiomeric separation of closantel were investigated in detail. The two enantiomers were successfully separated on the novel CSP of isopropyl derivatives of cyclofructan 6 and n-hexane-isopropanol-trifluoroacetic acid (97:3:0.1, v/v/v) as a mobile phase with a resolution (Rs) of about 2.48. The enantiomers were also well separated on the CSP of tris-carbamates of amylose with a higher Rs (about 3.79) when a mixture of n-hexane-isopropanol-trifluoroacetic acid (55:45:0.1, v/v/v) was used as mobile phase. Thus, the proposed separation methods can facilitate molecular pharmacological and biological research on closantel and its enantiomers.     

紫锥花种属中酚类化合物的HPLC分析

本文报道了一种测定紫锥花草药中咖啡酸、对羟基苯甲酸、对-香豆酸、原儿茶酸、丁香酸、阿魏酸、香草酸、咖啡奎尼酸、洋蓟酸、菊苣酸和紫锥花苷等11种酚类化合物的高效液相色谱分析方法。本法可应用于各种紫锥花草药中酚类化合物的测定。结果表明,在紫锥菊种属中含量最多的酚类化合物是菊苣酸、咖啡奎尼酸和紫锥花苷;在狭叶紫锥菊种属中含量较丰的是紫锥花苷和菊苣酸;而在白花紫锥菊种属中则以紫锥花苷以含量较多。     

热致相分离聚丙烯微孔膜

对聚丙烯－稀释剂体系热致相分离过程制备聚丙烯微孔膜的意义、原理、过程及研究现状进行了评述。     

On-Line Coupling of Separation Techniques to NMR

The hyphenation of chromatographic separation techniques with NMR spectroscopy is one of the most powerful and time-saving methods for the separation and structural elucidation of unknown compounds and molecular compositions of mixtures. Most of the routinely used NMR flow-cells have detection volumes between 40–180 μL for conventional separations with analytical columns, and the newest designs employ detection volumes in the order of 200 nL for capillary separations. The low flow rates used in capillary chromatography permit the use of deuterated solvents. Unequivocal structural assignment of unknown chromatographic peaks is possible by two-dimensional stopped-flow capillary HPLC-NMR experiments.     

超临界流体色谱法分离手性药物

对超临界流体色谱技术（SFC）在手性药物分离方面的研究与应用状况做了评述,对超临界流体色谱手性分离的分离方式、操作条件及影响因素作了介绍。     

HPLC法测定醋酸纤维素膜材料界面参数

以醋酸纤维素(CA-398)膜材料为填料,用HPLC法测定无机溶质(如氯化钠,硫酸镁)和多官能团的有机溶质(如糖等)的保留体积V_R’,平衡分配系数K_A’。由HPLC实验数据来确定聚合物膜材料界面参数。     

Separation and Detection of Arsenic and Selenium Species in Environmental Samples by HPLC-ICP-MS

A method is presented for arsenic speciation analysis of an oyster sample using ion chromatography coupled with an inductively coupled plasma mass spectrometry (ICP-MS) instrument. A strong anion exchange resin was employed with a step gradient elution of 0.1 mM/0.1 M K 2 SO 4 at pH 10.2. Arsenobetaine and dimethylarsinic acid were determined following extraction based on trypsin enzymolysis with 95-100% extraction efficiency. Limits of detection in the range 0.1-0.3 mg kg m 1 of arsenic were obtained for organic arsenic species. No inorganic arsenic was detected. Validation was performed using TORT-2 as a certified reference material. Although high performance liquid chromatography (HPLC) coupled to ICP-MS is an effective method for speciation analysis it is not always necessary to obtain such a detailed picture. A simple liquid chromatographic separation technique based upon mini-column technology is presented. It was developed to obtain a fast, efficient and reliable separation of inorganic from organic, i.e. assumed toxic from non-toxic, arsenic and selenium species suitable for use as an initial screening method for environmental analysis. Two types of strong anion exchange resin were tested. Excellent separation was obtained for both min-column resins and analysis times were within 7 min. Limits of detection obtained for inorganic arsenic, organic arsenic, selenomethionine, Se IV and Se VI were 1.6, 1.8, 66, 32 and 22 µg kg m 1 , respectively.     

Separation of 28 to 114°C hydrocarbons with glass capillary columns

Techniques have been developed for the rapid separation (about 20 minutes) of the 39 compounds in crude petroleums, or petroleum distillates, which boil between 28 and 114°C. A 300 meter glass column (0.25 mm i.d.) which is etched, coated with a mixture of normal hexadecane and Kel-F10157 is utilized to perform this separation at room temperature. The separations obtained with this non–polar liquid mixture and the «inert» glass surface are much more rapid than those previously obtained with stainless steel capillary columns.     

HPLC of antibiotics. 1. Streptolydigin and related compounds

Two new acyltetramic acids related to streptolydigin have been isolated from fermentations of Streptomyces lydicus. The principal members of this complex were resolved by TLC on silica gel. However, the methods of detection, permanganate spray or bioautography, were not suitable for both crude fermentation broths and purified extracts. Gas chromatography is unsuitable for the detection of either underivatized or silylated streptolydigins. High performance liquid chromatography (HPLC) particularly on triethylaminoethyl cellulose is rapid and sensitive and is the method of choice for the analysis of both crude and purified samples. Using high performance liquid chromatography, two components were detected in the complex, which are not observed using any of the other chromatographic procedures.     

液相色谱和毛细管电色谱连续床固定相技术

连续床作为一种新型的色谱固定相，具有制备简单、渗透性好、柱效高等优点，已广泛应用于HPLC和CEC。本文重点评述了连续床制备技术的进展。附参考文献65篇。     

Application of HPLC to characterization and control of individual acids in apple extracts and ciders

Summary Three HPLC methods have been tested in order to compare their separation of apple and cider organic acids. Optimum results for simultaneous determination of malic, citric, quinic, succinic, lactic and shikimic acids have been obtained using an RP-18 column with phosphate buffer as the mobile phase.This method was applied to organic acids monitoring during the ripening of apples and throughout the fermentation process. After filtration and degasification the organic acids in the sample were separated, and quantified by using a diode array detector.Recovery studies show good results for all solutes (88%–106%). The coefficients of variation show excellent precision (5%).     

Determination of the immunosuppressive drug tacrolimus in its dosage forms by high-performance liquid chromatography

Summary A high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of FK506, a new immunosuppressant, in bulk drug samples and dosage forms. Equilibration between FK506 (I) and its tautomeric compounds (II and III) was accomplished artificially in water-dehydrated alcohol (11) employed as an extraction solvent. After reaching equilibrium, separation of I, treated as the representetive of equilibrated FK506, from its related substances was achieved by reversed-phase HPLC on a C₁₈ column with water-isopropyl alcohol-tetrahydrofuran (522, v/v) as the mobile phase, and detection at 220 nm. Component I in dosage forms could be recovered satisfactorily and determined with good precision. The calibration graph was linear over the range 2–6 g for I.