摘要:

Two micro-batch flow titration assemblies are proposed in the present work. The first describes the use of a titration microchamber and an injection valve that joins two flow systems. Of the two flow systems, one uses an air carrier and the other a liquid carrier. The sensing elements are placed in the liquid carrier. The second assembly uses a titration microchamber with a miniature sensor placed inside. There is no need for calibrations when performing microtitrations in the two described assemblies. The air carrier moves the injected samples toward the titration chamber without dispersion. An automatic burette introduces a volume of titrant to the chamber.

ISSN:0003-2719    

DOI:10.1080/00032719508006408

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Supercritical fluid extraction (SFE) experiments with composted explosives lagoon soil suggest that recoveries of explosives and metabolites depend more on solvent diffusivity and viscosity than on the solubility of the analytes in the supercritical fluid. Preliminary evidence suggests that SFE recoveries for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX; a particularly difficult to extract explosive) can equal those for an 18 hr. ultrasonic extraction in acetonitrile. Much work is needed to confirm this observation, particularly to optimize the SFE conditions and improve the reproducibility of the extractions.

ISSN:0003-2719    

DOI:10.1080/00032719508006409

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A simple, sensitive and selective spectrophotometric method has been developed for determination of p-benzoquinone, tetrachloro-p-benzo-quinone, 1,4-napthaquinone and menadione (vitamin K3). The method is based on reaction of these quinones with excess piperidine in ethylalcohol. The colored products obtained display a maximum absorption at δ = 370-510 nm, depending upon the type of quinone used, E1%1 cmin the range 72-870. The effects of time, temperature and concentration on the nature of the reaction products have been investigated. The results obtained with an average recovery of 93.75%.

ISSN:0003-2719    

DOI:10.1080/00032719508006410

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Two sensitive spectrophotometric methods have been proposed for the determination of thorium with phenylfluorone (PF) and quercetin (Quer) in the presence of cetylpyridinium bromide (CPB) and polyvinylpyrrolidone (PVP), respectively. The optimum conditions for complexation reactions have been thoroughly investigated. The 1:3:4 (Th-PF-CPB) ternary complex and the 1:3 (Th-Quer) binary complex in the presence of PVP, are formed in the pH range 8.0-8.6 and 9.8-10.6, with molar absorptivities of 1.55 × 105and 6.25 × 1041.mol−1.cm−1, at 568 and 445 nm, respectively. The methods are rectilinear for 0.10-1.66 and 0.21-4.3 mg Th.l−1and their detection limits (signal-to-noise ratio = 3) are 0.082 and 0.139 mg.l−1, respectively. Results of analysis of thorium in monazite samples using these methods were in good agreement with those obtained by x-ray fluorescence spectrometry.

ISSN:0003-2719    

DOI:10.1080/00032719508006411

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Lewisite is generally a mixture of several components with the trans isomer of lewisite being the predominant compound. A geminal isomer has not been previously reported as one of the components of the mixture. In the lewisite samples we examined, the geminal isomer, dichloro(l-chlorovinyl)arsine, comprised 2.7 per cent of the total material compared to 95.2 and less than 1 per cent, respectively, for the trans and cis isomers. The remaining fraction was not identified. The geminal isomer of lewisite has been characterized along with the trans and cis isomers using several spectroscopic techniques. Proton NMR of the geminal isomer produced a coupling constant consistent with vinylic protons in a geminal configuration. Mass spectrometry and infrared spectroscopy characterizations were based on an ethanedithiol derivative of the lewisite isomers with gas chromatography used to first separate the derivatized isomers. The electron ionization massspectra of the trans and cis derivatives were very similar, but significant differences were observed in the mass spectrum of the geminal form. Infrared absorption spectra were obtained for the trans and geminal derivatives with significant differences observed between the two, but the method was not sensitive enough to detect the cis isomer.

ISSN:0003-2719    

DOI:10.1080/00032719508006412

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719508006397

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor