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The determination of salicylic acid was carried out by reaction of the drug with copper carbonate entrapped in a polymeric material in a solid-phase reactor; the released cupric ions were monitored by flame atomic absorption at 324.8 nm. The calibration graph is linear over the range 4.0-75 μg ml -1 of salicylic acid, with a relative standard deviation of less than 1.5% and a sample...
Within the past several years significant advances have been made towards the development and incorporation of chemically modified electrodes as selective detectors for high performance liquid chromatography and flow injection analysis. In many cases the chemically modified electrode systems closely approach the ideal detector specifications of chemical and mechanical stability along with a significant...
A highly selective, rapid and direct amperometric method, based on the formation of a complex between tin(II) and 8-hydroxyquinoline (oxine), has been developed for the determination of trace levels of tin(II) using flow injection analysis. Tin(II) electro-oxidation was catalyzed by oxine; its oxidation peak occurred at +0.05 V vs. Ag/AgCl at a glassy carbon electrode in 0.1 mol 1 -1 ...
A multicomponent detection system using optical biosensors and flow injection analysis is described. The analysis of mixtures containing penicillin and ampicillin was realised by evaluating dynamic measurements of Phenol Red spectra in penicillinase optodes in combination with a diode array spectrometer. A variety of optodes has been produced by changing the composition of the receptor gel and the...
A flow-injection method for the ultraviolet spectrophotometric determination of silver, based on its reaction with nickelocyanide ion, Ni(CN) 2-4 , in ammoniacal buffer medium (pH 10) and subsequent measurement of the decrease in the absorption of the Ni(CN) 2-4 complex at 275 nm is described. The calibration graph is linear in the range 10-400 μm silver. At a...
A flow-injection-based kinetic method for the determination of lead ions was developed. In this method, resazurin was reduced to resorufin by sulfide and lead ions. The method has a detection limit of 1 ppb with a relative standard deviation of 5.2% at the 20 ppb level. Interferences can be removed by prior extraction.
An ammonia sensor is described in this work. The sensing membrane is a thin layer of oxidized polypyrrole (PPy) on a platinum substrate. This sensor is used as the working electrode in a conventional three-electrode system for amperometric measurement of ammonia in aqueous solutions in the potential range of +0.2 to +0.4 V (vs. Ag/AgCl). Contact with ammonia causes a current to flow through the...
A new flow injection method for the determination of trace amounts of ammonium ions was developed by using a glassy carbon electrode electrodeposited with a film of cupric hexacyanoferrate coated with Nafion film as the sensor. The electrode gives sensitive but not selective response to potassium and ammonium ions. A gas-diffusion unit was used for the separation of ammonium and potassium ions and...
A highly sensitive detection system using a semiconductor laser (SCL) and a thin long flow-through cell (TLFCT) to match flow-based analysis, such as flow injection analysis (FIA), has been developed. The SCL was a GaAlAs semiconductor laser emitting at 780 nm (5 mW), and the TLFTC, which has a 100 mm thin long light path, was made of a poly(tetrafluoroethylene) (PTFE) rod. The sensitivity was essentially...
The concentration of l-lactic acid was determined by a combination of flow injection analysis with amperometric enzyme sensor detection. The enzyme sensor was prepared by immobilizing lactate oxidase in a layer of polyion complex consisting of poly-l-lysine and poly(4-styrenesulfonate). The sensor-based system can be used for the determination of l-lactate concentration up to 6 mM with a sampling...
A modified graphite electrode was produced by adsorption the bis(diisopropyloxythiophosphone)disulphide {(i-PrO-) 2 P(S)S-} 2 under vacuum. Its electrochemical characteristics in flowing stream were described. The modified electrode has been used for simultaneous determination of Cu(II), Ag(I) by flow injection anodic stripping voltammetry.
A simple flow injection analysis (FIA) system for residual chlorine in tap water has been developed by using a Pb(II) ion-selective electrode (ISE) detector. The method is based on a specific response of the Pb(II)-ISE to residual chlorine. The FIA system consists of a millivolt meter, a peristaltic pump, a Pb(II)-ISE detector and a recorder. A linear working curve between peak height and concentration...
A new catalytic method for the determination of silver(I) was developed based on a metal exchange reaction between ethylenediaminetetraacetatomercury(II) (Hg II -EDTA) in the aqueous phase and bis(diethyldithiocarbamato)copper(II) (Cu II -DDTC) in the organic phase. This exchange reaction (Cu II -DDTC org + Hg II -EDTA → Hg ...
The viability of electrodialysis (ED) for the enhancement of mass transfer through passive neutral membranes in a flow injection system was investigated. A Spectrapore and Technicon type C membrane were evaluated using chloride anions as analyte. Both membranes showed an increase in mass transfer and the proposed electrodialyser/FIA system was applied for the determination of chloride in industrial...
A flow injection procedure for the separation and pre-concentration of inorganic arsenic based on the complexation with ammonium diethyl dithiophosphate (DDTP) and sorption on a C-18 bonded silica gel minicolumn is proposed. During the sample injection by a time-based fashion, the As 3+ -DDTP complex is stripped from the solution and retained in the column. Arsenic(V) and other ions that...
The application of differential electrolytic potentiometry as a detection system in flow injection analysis for precipitation reactions is described. Different combinations of electrodes were investigated. The optimum conditions for the current density and the flow rate were elucidated. In the case of chloride, an Ag/AgCl-Pt pair was found to be successful. For iodide a combination of Ag-Pt electrodes...
Ni(II) and Co(II) have been determined simultaneously by means of adsorptive cathodic stripping voltammetry (AdCSV) in a computerised flow injection system. The working electrode was a glassy carbon disk that was fitted in a wall-jet flow cell. The electrode was initially electrochemically coated with a mercury film at −1.0 V by injecting a Hg(II) solution in the flow stream. Then, the sample, containing...
The concentration of potassium was determined by a combination of flow injection analysis (FIA) with an all-solid-state potassium sensor detection. The all-solid-state potassium-selective electrode possessing long-term potential stability was fabricated by coating an electroactive polypyrrole/poly(4-styrenesulfonate) film electrode with a plasticized poly(vinyl chloride) membrane containing valinomycin...
The controlled release of coreactants at the sensing tip of a biosensor is a possible approach to develop self-contained devices. For luciferin which is a firefly luciferase cosubstrate, a new method of retention is evaluated. The two-step procedure consists of incorporating the substrate in acrylic microspheres during their formation, these last being then confined in a PVA SbQ film. When associated...
A continuous system for the determination of fish freshness with double enzyme reactors was developed and applied to the determination of the freshness indicator KK=100(HxR+Hx)/(IMP+HxR+Hx),where IMP, HxR and Hx are Inosine monophosphate, Inosine and Hypoxanthine, respectively. The system was assembled with a three electrode screen-printed element (graphite as working electrode, silver as counter...
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