摘要:

High performance liquid chromatography in reversed-phase system was used to control the synthesis ofFinasteride{17β (N-tert-carbamoyl)-4-aza-5α-androst-1-ene-3-one} - the drug used in the therapy of prostatic carcinoma. The objective of these investigations was the finding of such composition of mobile phase which would separate the semi-products obtained in individual stages of synthesis from final products and UV detection at 210 nm. For this purpose we adopted the method of triangle optimisation.

ISSN:1082-6076    

DOI:10.1081/JLC-100101799

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The capacity factors (k′) were determined by reversed phased high-performance liquid chromatography (RP-HPLC) on a C18column for 18 substituted indoles. The linear relationship between the (k′) values and the percentage of the methanol in the eluent was tested for each compound. The molecular connectivity indices and quantum chemical parameters were calculated for the tested chemicals and used to develop quantitative structure-retention relationships (QSRR).

ISSN:1082-6076    

DOI:10.1081/JLC-100101800

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

High performance liquid chromatography-tandem mass spectrometry (LS/MSn) utilizing an ion trap mass spectrometer has been used for the analyses of representative cardiac steroids. In the case of bufotoxin having a polar residue (suberoylarginine), the positive-electrospray ionization (ESI) was 50 times more sensitive than the atmospheric pressure chemical ionization (APCI) and provided information concerning the molecular weight as well as the structures of both aglycone and suberoylarginine. The corresponding bufogenin showed 2 times better sensitivity in the positive-APCI than ESI. The mass spectrum of digoxin with the positive-APCI showed fragment ions not only derived from aglycone but also formed by losses of sugars.

ISSN:1082-6076    

DOI:10.1081/JLC-100101801

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A liquid chromatographic method is described for the determination of albendazole in cattle feeds. Samples are extracted with acetonitrile, and the extracts, after partitioning with hexane, are analyzed by ion-pair liquid chromatography with detection at 292 nm. Albendazole is eluted from the column well resolved from its oxidation byproducts. The method shows analytical characteristics well within acceptable limits. Recovery was in the range of 98.2–100.4%, while precision, expressed as percent relative standard deviation, in the range of 1.6–3.1%. Limit of detection was estimated at 0.5 μg/g, and limit of determination at 1.0 μg/g.

ISSN:1082-6076    

DOI:10.1081/JLC-100101802

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Solid phase extraction (SPE) for the treatment of bovine urine samples in the analysis of β2-agonist multi-residues by gas chromatography-mass spectrometry (GC-MS) was evaluated. Mabuterol, mapenterol, clenproperol, terbutaline, clenbuterol, salbutamol, clenpenterol, bromobuterol and hidroxi-metilclenbuterol (NA1141) were tested with five different mechanisms: adsorption, reverse phase, polar, ion exchange, and mixed phase, and eleven sorbents: diatomaceous earth, octadecyl (C18), octyl (C8), native silica (Si), diol (2OH), amine (NH2), trimethylaminopropyl (SAX), propylbenzenesulphonic (SCX), Bond Elut Certify® (C8+SCX), Clean Screen DAU® (CSDAU) and Multimode (C18+SCX+SAX).

ISSN:1082-6076    

DOI:10.1081/JLC-100101803

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple and sensitive liquid chromatographic method has been developed for the determination of digoxin and digitoxin by derivatization. The method is based on the derivatization of digoxin and/or digitoxin with derivatizing agent, 1-naphthoyl chloride, in pyridine at 50?C. Under the mild condition, the digoxin and digitoxin were derivatized into their highly sensitive derivatives. After the derivatization reaction, a dimethylamine- acetonitrile solution was added to the reaction mixture to eliminate the interference from the excess derivatizing agent. The derivatives obtained were performed on a reversed-phase C8column with 88% acetonitrile as the mobile phase. The parameters affecting the derivatization of digoxin and digitoxin, including reaction temperature, reaction time, and the amount of derivatizing agent, were investigated. The linear ranges of the method for the determination of digoxin and digitoxin were over 1–50 nmol/mL and 5–50 nmol/mL; the detection limit (signal to noise ratio = 5; injection volume, 20 μL) were 0.25 nmol/mL and 0.30 nmol/mL, respectively. Partial application of the method to the analysis of digoxin in commercial tablets has proven to be satisfactory.

ISSN:1082-6076    

DOI:10.1081/JLC-100101804

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A high performance liquid chromatographic method for the simultaneous determination of five organochlorine pesticides (aldrin, p,p’-DDT, dieldrin, endrin, and heptachlor) was developed. The method was used to determine the levels of these pesticides in medicinal plant samples. Analysis was carried out using a Merck LiChrospher 100 RP C18(5 μm) column with a gradient solvent system of acetonitrile-water and PDA UV detection (224 nm). Quantification was carried out by the external standard method. The limit of detection for the utilized method was below the local legal limits (ANZFA) for similar plant materials for all 5 pesticides excepting endrin. Medicinal plant extracts were further analyzed by conventional GC-ECD and GC-NPD means using SPE and GPC cleanup as required.

ISSN:1082-6076    

DOI:10.1081/JLC-100101805

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The retention behaviour of some alkaloids, as test samples, on reversed-phase pre-coated thin layer chromatography in the presence of different ion-pair reagents was investigated. Trifluoroacetic acid (TFA), pentafluoropropionic acid (PFPA), and heptaflluorobutyric acid (HFBA) were used as counter ions. The dependence of RFvalues on the eluent composition, the chain length of the ion-pair reagent and the ratio of two ion-pair reagents in the eluent is described. The retention values of the tested alkaloids after impregnation of the plate with the counter ion, were investigated.

ISSN:1082-6076    

DOI:10.1081/JLC-100101806

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Single UV-absorbing background electrolyte (BGE) has been designed for simultaneous detection of alkali metals and anions. The BGE is composed of a cationic buffer component and an anionic chromophore. Tris, sulfosalicylic acid, trimellitic acid, 1,5-naphthalenedisulfonic acid were tested as the cationic and anionic components in the BGE, respectively. 1,5-naphthalenedisulfonic acid was selected as the anionic chromophore of the BGE for the separation of cations and anions. In Tris/1,5-naphthalenedisulfonic acid BGE, K+, NH4+, Na+, Li+, ascorbate, sorbate, benzoate, lactate, acetate, HCO3−, phosphate, formate and fluoride could be detected within 9 minutes with detection limits ranging from 0.1 to 1 ppm under the optimized conditions. This newly developed method allows a larger choice of components to define BGE in simultaneous detection of cations and anions in indirect photometric detection. The applicability of this type of BGE has been demonstrated in the analysis of a real sample. The results obtained were comparable to those obtained by inductively-coupled plasma spectroscopy (ICP) and ion chromatography (IC).

ISSN:1082-6076    

DOI:10.1081/JLC-100101807

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The reduced form of vitamin C is referred to as L-ascorbic acid (AA), and the oxidized form is referred to as L-dehydroascorbic acid (DHAA). In humans, both forms are biologically active. The total vitamin C activity is defined as the sum of both forms. This review discusses HPLC methodologies for total vitamin C activity with references to their applications mainly in citrus juices and related drink products.

ISSN:1082-6076    

DOI:10.1081/JLC-100101808

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor