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31.
Two pH-sensitive neutral carrier/PVC electrodes are used simultaneously for the measurement of pH by flow injection. One of these is based on the neutral carrier tridodecylamine and the other on octadecyl isonicotinate, and together they allow the pH range 1–13 to be covered. These electrodes have been used in a very low dispersion miniature potentiometric flow cell designed specifically for use in flow injection in conjunction with a multi-channel data acquisition system. The effects of the solution ionic strength and buffer capacity on the pH measurement are discussed. A flow-injection manifold is proposed which can be used for high-accuracy pH measurements without ionic strength adjustment of the sample and for simultaneous pH and ion concentration measurements with ionic strength adjustment. This has been tested on some synthetic samples for the simultaneous determination of potassium and calcium and the measurement of pH. 相似文献
32.
Near-infrared dyes can be derivatized with appropriate functional groups for use as analytical probes for numerous applications. A dye derivatized with pH-sensitive functional groups may show spectral changes when the pH of its environment is changed. These dyes are valuable to the researcher since they absorb and fluoresce at long wavelengths where interference is minimal and their absorption maxima permit the use of semiconductor lasers. In this paper we have evaluated the sensitivity to pH of a bis-carboxylic acid derivative of a near infrared dye to illustrate its potential as a probe for determining pH. The dye has an absorption maximum at 795 nm in aqueous solution, a region where several commercially available laser diodes have their output maximum. The analytical utility of near-infrared laser diodes for pH determination has also been evaluated. 相似文献
33.
Kalin RM Hamilton JT Harper DB Miller LG Lamb C Kennedy JT Downey A McCauley S Goldstein AH 《Rapid communications in mass spectrometry : RCM》2001,15(5):357-363
Gas chromatography/mass spectrometry/isotope ratio mass spectrometry (GC/MS/IRMS) methods for delta(13)C measurement of the halomethanes CH(3)Cl, CH(3)Br, CH(3)I and methanethiol (CH(3)SH) during studies of their biological production, biological degradation, and abiotic reactions are presented. Optimisation of gas chromatographic parameters allowed the identification and quantification of CO(2), O(2), CH(3)Cl, CH(3)Br, CH(3)I and CH(3)SH from a single sample, and also the concurrent measurement of delta(13)C for each of the halomethanes and methanethiol. Precision of delta(13)C measurements for halomethane standards decreased (+/-0.3, +/-0.5 and +/-1.3 per thousand) with increasing mass (CH(3)Cl, CH(3)Br, CH(3)I, respectively). Given that carbon isotope effects during biological production, biological degradation and some chemical (abiotic) reactions can be as much as 100 per thousand, stable isotope analysis offers a precise method to study the global sources and sinks of these halogenated compounds that are of considerable importance to our understanding of stratospheric ozone destruction. 相似文献
34.
James KJ Crowley J Hamilton B Lehane M Skulberg O Furey A 《Rapid communications in mass spectrometry : RCM》2005,19(9):1167-1175
The potent neurotoxins from cyanobacteria, anatoxin-a (AN), its methyl analogue, homoanatoxin-a (HMAN), and their degradation products, have been studied using nano-electrospray hybrid quadrupole time-of-flight mass spectrometry (QqTOF-MS). The anatoxin degradation products, which are readily produced in vivo by either reduction or epoxidation, were also examined in this study. The high mass accuracy QqTOF-MS data was used to confirm formula assignments for major product ions and quadrupole ion-trap (QIT)-MS was used to construct fragmentation pathways for anatoxins. Significant differences between these fragmentation pathways were observed. Comparisons between the spectra of compounds that differ in side-chain length (the AN and HMAN series) were used to identify ions that are characteristic of the homologues. The application to forensic samples in which the principal neurotoxin had undergone rapid biodegradation has been demonstrated and used to confirm anatoxin poisoning of dogs. 相似文献
35.
A hyperfine field of 46.9±4.0 T at Gd nuclei in the intermetallic compound ZrFe2 was measured by the time-differential perturbed angular correlation method. This result indicates an additional contribution of 81 T to that measured in gadolinium metal and suggests a similarity between the magnetic properties of ZrFe2 and those of the rareearth intermetallic compounds. 相似文献
36.
John de Jersey ZHENG Yuan-zhi FAN Hong-kuan Gary Schenk Luke Guddat Susan Hamilton 《高等学校化学研究》2006,22(2):263-264
Introduction Purpleacidphosphatases(PAPs)compriseofa familyofbinuclearmetal containinghydrolases,some membersofwhichhavebeenisolatedandcharacterized fromanimal,plantandfungalsources[1].PAPsnoton lycatalyzethehydrolysesofawiderangeofphosphate estersandanhy… 相似文献
37.
Tamara D. Hamilton 《Journal of solid state chemistry》2005,178(8):2409-2413
We show how a template-controlled reaction performed in the organic solid state can be used to construct a molecule that functions as an organic building unit of both a metal-organic polyhedron and polygon. The template is a small organic molecule that organizes two olefins via hydrogen bonds for a [2+2] photodimerization. The process of utilizing a molecule to build a molecule that is subsequently used for self-assembly is inspired by the general two-step process of template-directed synthesis and self-assembly of Nature that is used to construct large, functional self-assembled structures. 相似文献
38.
39.
DTA curves were run for the ethylenebisdithiocarbamate fungicides maneb, mancozeb and zineb in a nitrogen atmosphere. Zineb produces a curve quite different from the others, with weak endothermic peaks at 166°C, 252°C and 293°C. Maneb and mancozeb have a relatively strong endothermic peak at 185–190°C corresponding to carbon disulphide evolution and a weaker endothemic peak at 290°C corresponding to hydrogen sulphide evolution. Maneb samples and some mancozeb samples also had a minor endothermic peak at 235°C, but this peak was lost after solvent extraction, which proved that it was due to an impurity or impurities. Elemental sulphur was found in the extract and on mixing sulphur with mancozeb, the peak at 235°C made its appearance. There is no distinguishing feature between the DTA curves for maneb and mancozeb. The shapes of the curves are, within experimental limits, indistinguishable, which means that the temperatures and energies of decomposition are the same. The chemist is left with the question whether differences in structure between maneb and mancozeb should lead to different DTA curves. 相似文献
40.