摘要:

The ability to distinguish functional group and the presence of specific elements in vapor phase infrared spectra is demonstrated using pattern recognition techniques. Kth nearest neighbors analysis was found to be superior to hyperplane separations. Weight-sign feature selection was used to elucidate the significant wavelengths which exhibited agreement with established group frequencies. The use of vapor phase infrared spectra for gas chromatographic peak identification is discussed.

ISSN:0003-2719    

DOI:10.1080/00032717908059776

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Transformation of data with skew distributions into symmetrie ones is an important aid by evaluation of histograms and accentuates class groupings in multivariate principal components analysis.

ISSN:0003-2719    

DOI:10.1080/00032717908059777

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Heterogeneous membranes of 2.0 cm diameter were prepared from a 60:40 mixture of thallium(I) molybdoarsenate and Araldite, These membranes gave near Nernstian response to thallium(I) ions over the concentration range 10−1to 10−3M but could be used for determination of thallium(I) down to 10−5M. Slope of the log concentration-potential plot is improved in 10 and 25 percent acetone-water mixture. The response was independent of pH over the range 4.0 to 6.0, The response time of the electrode is few seconds and potentials generated are reproducible. The selectivity of the electrode over a large number of cations was studied. The values of selectivity coefficients are of the order 10−2for monovalent and 10−3for bivalent cations. Anions did not interfere. Potentiometric-titration of thallium nitrate with potassium chromate was also done using the membrane as an end point indicator electrode.

ISSN:0003-2719    

DOI:10.1080/00032717908059778

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Thorium has been determined amperometrically at an applied e. m. f. of -1.2V with fifteen maleanilic acids. Out of these o-tolyl, p-tolyl, 1-naphthyl, 2-naphthyland 4-amino maleanilic acid were found promising analyticalreagentsand most effective. Th(IV) in the range 6.60 to 2350.0 mg per 100 ml can be determined with an error of ± 0.2%. The interference of fifty-five ions were studied and only five ions Zn(II), Pb(II), Fe(III), UO2(II) and Zr(IV) interfered. which could be masked by the addition of S2O23or SCN−, Cl−or SO2-4, SCN−or citrate, citrate or tartrate and P2O4-7respectively.

ISSN:0003-2719    

DOI:10.1080/00032717908059779

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The methyl esters of 2-methoxy-3, 6-dichlorobenzoic acid and three phenoxyacetic acids were prepared by the admixture of an excess of both methyl iodide and anhydrous alkali-metal carbonate to a solution of the carboxylic acids in acetone. The reaction was completed within the shortest period of time when cesium carbonate was used, and the reaction mixture was injected without further work-up into a gas chromatograph fitted with a flame ionization detector. Further reduction of reaction time was achieved by heating the mixture to 50°C and by ultrasonic treatment; this technique is also suitable for esterification of microliter quantities and obviates the need for a microrefluxer. Butylesters of 2, 4-D and 2, 4, 5-T were prepared in an analogous manner. The methyl esters of 2, 4-D and 2, 4, 5-T, and the butyl ester of 2, 4-D were obtained in better than 90% yield.

ISSN:0003-2719    

DOI:10.1080/00032717908059780

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Fluorescamine reacts with primary amines, it does not react with secondary or tertiary amines, to yield bright acquamarine fluorescent products. This reaction has been developed into a spot test useful for differentiation of amphetamine from methamphetamine; previous spot tests did not have this degree of specificity. The fluorescent products of several primary amines have been demonstrated to have sufficient stability to permit thin-layer chromatography comparisons with authentic materials. The fluorescent derivative of amphetamine has been demonstrated to be capable of differentiation from other fluorescent products formed from fluorescamine based on its unique migration in three different TLC systems.

ISSN:0003-2719    

DOI:10.1080/00032717908059781

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A highly sensitive, selective, and rapid method for the spectrophotometry determination of vanadium(V) at trace levels is described. The method is based on the selective extraction of vanadium(v) from strongly acidic (3–6 M hydrochloric acid) met ium with solution of N-0-methoxyphenyl-2- thenohydroxamic acid (0MTHA) in chloroform. The extract is then equilibrated with 3-(0-carboxyohenyl)-1-phenyltriazine-N-oxide(CPPTNO) at pH ≃ 1.5 and the resulting colour is measured at 445 nm. The colour system obeys Beer's law over the range 0–20 -μg/ml of vanadium; the molar absorptivityat the wavelength of maximum absorption (445 nm), and the Sandell sensitivity of the method are 1.1 × 1041. mole−1cm−1and 0.005 μg/ml respectively.

ISSN:0003-2719    

DOI:10.1080/00032717908059782

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The first experiment in which stepwise photoionization of atoms is used for analytical purposes is reported. A detection limit of 12 pg/ml has been achieved for sodium in aqueous solutions. The results are compared with atomic fluorescence measurements. The potentialities of the new method are discussed.

ISSN:0003-2719    

DOI:10.1080/00032717908059783

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The tris (hydroxymethyl)aminomethane salt of d-10-camphorsulfonic acid (TRIS-CSA) provides a convenient, non-hygroscopic alternative to the parent compound in the calibration of circular dichrometers. The molecular ellipticities, [6], of TRIS-CSA at 291 and 191 nm are 8015± 11 and -16, 130± 40 deg cm2dmol−1, respectively. The circular dichroism (CD) maxima in terms of δϵ are 2.429 1 cm−1mol−1at 291 nm and -4.888 1 cm−1mol−1at 191 nm. TRIS-CSA has an ORD peak at 306.5 nm, a zero crossover at 292 nm, and a trough at 270.5 nm (molecular rotation, [M]306.5=4475± 10, [M]270.5= -5615± 10 deg cm2dmol−1), and a molar absorptivity, ϵ, of 35.9± 0.2 1 cm−1mol−1at 286 nm.

ISSN:0003-2719    

DOI:10.1080/00032717908059784

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The oxidative destruction of unsymmetrical dimethylhydrazine (UDMH) by a molar excess of Ca(OCl)2leads mainly to formaldehyde dimethylhydrazone and tetramethyl tetrazene, but not to N-nitrosodi-methylamine (NDMA). An alternate method using H2O2/CuSO4leads to ca. 25% NDMA. The amount of UDMH destroyed is affected by the order of addition of the H2O2, and CuSO4: when the CuSO4is added first, only ca. 65% of the UDMH is destroyed, while the reverse order of addition leads to 100% destruction of UDMH.

ISSN:0003-2719    

DOI:10.1080/00032717908059785

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor