Development and application of a fully automated,battery-operated,computerized field-based fluoride monitor

An automated, portable, battery-operated, computerized field-based monitor for the determination of fluoride based on the use of ion-selective electrode (ISE) potentiometry has been developed with the aid of low-powered complementary metal oxide semiconductor (CMOS) devices. The whole analytical cycle involving the rinsing of the cell, sampling, stirring, dosing of standards to the sample and data acquisition and manipulation is under microprocessor control. The modular instrument consists of pumps, valves, a flow-through cell containing a reference electrode, a fluoride ISE, a temperature probe and a stirrer, a microprocessor with a real-time clock, a pump-valve-stirrer interface, a portable terminal and a 12-V lead-acid battery to power all the instrumentation. The software for the application and monitoring functions for the instrument is written at assembler level and programmed into a CMOS erasable programmable read only memory (EPROM). The instrument is currently designed to determine fluoride in natural and fluoridated waters and is based on a double standard addition method, although the monitor can be modified easily to suit other appropriate ISE systems. Instrumental performance was evaluated with synthetic and real water samples both in the batch and continuous modes. The monitor can be used to carry out on-line fluoride determinations of water samples continuously for 1 week without anyone being attendance.     

Kinetic analysis of n-butane hydrogenolysis on a Ru/Al2O3catalyst

Summary Analysis of the kinetics of the hydrogenolysis of n-butane on a Ru/Al₂O₃catalyst permits recognition of the range of H₂:n-butane ratio where carbon formation can be neglected. Variation of the apparent activation energy with H₂pressure results from a variable contribution of its heat of adsorption to the true activation energy. Effects on product selectivities and on response of rate to H₂pressure due to oxidation and low-temperature reduction are also traced to differences in heats of adsorption.</o:p>     

Syntheses of syn and anti doublebent [5]phenylene

[structure: see text] The parent and dipropyl-substituted anti (1a,b) and syn doublebent (2a,b) [5]phenylenes have been assembled by CpCo-catalyzed double cyclization of regiospecifically constructed appropriate hexaynes. (1)H NMR, NICS, and an X-ray structural analysis of 1a reflect the aromatizing effect of double angular fusion on the central ring of the linear [3]phenylene substructure.     

Two new cobalt-zinc orthophosphate monohydrates: hydrothermal synthesis, crystal structures and thermal investigation

Two new cobalt zinc orthophosphate hydrates with similar chemical formula, (CoxZn(1-x))3(PO4)2.H2O, but different composition and structure, have been prepared by systematic hydrothermal synthesis from the system nCo(CH3COO)2 : (1 -n)Zn(CH(3)COO)2 : 3.5H3PO4 : 2.1(CH3)2NH(CH2)3NH2:144H2O (0 相似文献   

Evaluation of some dry ashing methods for anodic stripping voltammetric determination of cadmium and lead in biological materials

Several dry-ashing methods were evaluated for the accurate determination of cadmium and lead in biological materials by anodic stripping voltammetry. The method utilizing sulphuric acid as the ashing aid at 500°C was found to be most suitable for the determination of both elements. However, a carbonaceous residue still required that substantial sample dilution be made after dissolution of the sample ash to avoid interferences to the stripping electrode process(es). The dissolution of the sample ash with hydrochloric acid as preferred to the use of nitric acid in obtaining more reproducible results.     

Continous monitoring of copper and cadmium in zinc plat electrolyte usinga microprocessor-based batter-operated data acquisition system,multiple ion-selective electrodes and redundancy principles

Monitoring of both copper and cadmium is essential in the electrolytic production of zinc because these elemetns must be removed in order to improve the efficiency of the zinc electro-refining process. A new high-volume flow-through cell with an assembly of four ion-selective electrodes (four copper, four cadmium or two copper and two cadmium electrodes), reference electrode and temperature probe coupled with microprocessor-based instrumentattion can be used for this purpose. Determinations can be done continuously for 72-h periods without maintenance in an on-line mode. when multiple electrode determinations and redundncy principles are implemented. A microcomputer system incorporating low-power CMOS technology with multichannel and multiplexing capabilities is used for data acquisition. The use of the battery-powered data acquisition system provides excellent signal-to-noise ratios, meets the special demands of the harsh industrial environment, and is preferable to conventional mains-powered monitoring systems based on ion-selective electodes.     

Chemical analysis with a low energy particle accelerator

The low energy particle accelerator at Brooklyn College is being applied to chemical analysis by studies of: charged particle induced nuclear reactions, proton induced X-ray emission, and inelastic neutron scattering. Fluorine-containing gaseous compounds in the atmosphere and fluorine in airborne particulates will be determined by detection of the prompt gamma-rays and/or alpha particles emitted in the reaction¹⁹F(p,a)¹⁶O. The PIXE technique is being applied to analysis of a variety of environmental samples, and activation by inelastic neutron scattering is being investigated for elements which are not amenable to thermal neutron activation. This work was supported in part by the U. S. Energy Research and Development Administration under Contract E(11-1)-3126.     

Metal polypyrazolylborate complexes : IV. Some reactions of organometallic rhodium(I) chloride derivatives with polypyrazolylborates

Reactions of the 1,5-cyclooctadiene complex [C₈H₁₂RhCl]₂ with the potassium polypyrazolylborates K[H_4?nBPz_n] (Pz = pyrazolyl, n = 2, 3 and 4; Pz = 3,5-dimethylpyrazolyl, n = 2 and 3) in ethereal solvents give the corresponding complexes C₈H₁₂RhPz_nBH_4?n as stable yellow solids. Reaction of [Rh(CO)₂Cl]₂ with potassium bis(pyrazolyl)borate in hexane gives yellow H₂B(C₃H₃N₂)₂Rh- (CO)₂, but similar reactions of [Rh(CO)₂Cl]₂ with the other polypyrazolylborates lead only to decomposition at room temperature. The tris- and tetrakis(pyrazolyl)borate rhodium 1,5-cyclooctadiene complexes all appear stereochemically non-rigid at room temperature.     

The analytical performance of direct current,normal pulse and differential pulse polarography with static mercury drop electrodes

The recently developed static mercury drop electrode (SMDE) provides a fundamentally new approach to electrodes for polarography. An analytical evaluation of the electrode is presented. For a range of electrode processes, current-sampled d.c. polarography at the SMDE is useful down to at least the 10^-7 M concentration level when short drop times and fast potential scan rates are used. The improvement in the limit of detection for d.c. polarography is therefore very substantial. Improvements in sensitivity associated with normal pulse and differential pulse polarography at the SMDE compared with the dropping mercury electrode (DME) are marginal. It is concluded that at the SMDE, the analytical performance and response characteristics of d.c., normal pulse and differential pulse polarography tend to converge.