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Content available remote Cobalt(II) ion-selective electrode with solid contact
Open Chemistry
tom 6
nr 4
A new all plastic sensor for Co2+ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10−6 mol L−1 and almost theoretical Nernstian slope in the activity range 4.0 × 10−6–1 × 10−1 mol L−1 of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co2+ in real samples and as an indicator electrode in potentiometric titration of Co2+ ions with EDTA. [...]
Ethambutol (ETB) is a first-line antitubercular drug effective against actively growing Mycobacterium tuberculosis. Resistance of the mycobacterium to ethambutol among tuberculosis (TB) patients results from inadequate or inappropriate dosing of treatment or using low quality medication. It is therefore necessary to develop reliable methods for determining ethambutol metabolic profiles of patients at point of care for proper dosing. Herein an efficient ETB sensor device is illustrated. It consists of a graphite-polyurethane composite electrode. In order to characterise the electrochemical behaviour of ethambutol at pH = 8.0 voltammetric studies were performed. The detector was assembled in a flow injection apparatus and operated at +1.2 V (vs. Ag/AgCl(NaCl sat.)). The influence of sample volume and flow rate was studied. The linear response for the method was extended up to a 1.1 mmol L−1 ethambutol solution with a detection limit of 0.0634 mmol L−1. The reproducibility of current responses for injections of 0.7 mmol L−1 ethambutol solution was evaluated to be 5.1% (n = 30) and the analytical frequency was 161 determinations h−1. Two different samples were successfully analysed and the results were in good agreement with those obtained using capillary zone electrophoresis (CZE). [...]
In this work, a flow-injection spectrophotometric method for dipyrone determination in pharmaceutical formulations was developed. Dipyrone sample solutions were injected into a carrier stream of deionized water and the reaction was carried out in a solid-phase reactor (12 cm, 2.0 mm i.d.) packed with Cu3(PO4)2(s) entrapped in a matrix of polyester resin. The Cu(II) ions were released from the solid phase reactor by the formation of Cu(II)-(dipyrone)n complex. When the complex is released, it reacts with 0.02% m/v alizarin red S in deionized water to produce a Cu(VABO3)3 complex whose absorbance was monitored at 540 nm. The calibration graph was linear over the range 5.0×10−5–4.0×10−4 mol L−1 with a detection limit of 2.0×10−5 mol L−1 and relative standard deviation for 10 successive determinations of 1.5% (2.0×10−4 mol L−1 dipyrone solution). The calculated sample throughput was 60 h−1. The column was stable for at least 8 h of continuous use (500 injections) at 25°C. Pharmaceutical formulations were analyzed and the results from an official procedure measurement were compared with those from the proposed FIA method in order to validate the latter method. [...]
New methods for the determination of metoclopramide, antiemetic and gastroprokinetic pharmaceutical, were developed, using differential pulse voltammetry (DPV) and flow injection analysis (FIA) with amperometric detection on a boron-doped diamond film electrode. Electrode pretreatment necessary to ensure the stable results was investigated and it was found, that while DPV requires frequent electrode cleaning, FIA with a sufficiently high flow rate can maintain a stable signal with no signs of electrode passivation. The calculated quantification limits of the DPV and FIA with amperometric detection were 0.13 μmol L−1 and 0.015 mmol L−1, respectively. The applicability of the new methods was verified by the determination of metoclopramide in a pharmaceutical preparation. FIA with amperometic detection proved to be sensitive, accurate and, due to the resistance of the electrode to the passivation, also simple to handle. [...]
Modern analytical techniques are expected to fulfil high requirements in terms of both the quality of the obtained analytical results as well as caring for the environment. The methods should be developed in accordance with the rules of so-called Green Analytical Chemistry. Flow analysis techniques meet these assumptions. Their rapid development, especially in terms of instrumental solutions has been observed in recent years. Instrumental solutions employed in the flow analysis techniques allow for shortening the time of analyses, minimization of samples and reagents consumption as well as waste production, reduction of the costs of analyses and the risk of exposure of laboratory personnel on toxic substances. Their use, in many cases, has also a beneficial effect on improving the precision and accuracy of the analytical determinations. The article presents selected instrumental solutions used in various flow analysis techniques. Flow analysis techniques can be divided, inter alia, according to: the way of sample introduction into a flow system (continuous or intermittent sampling), the type of the liquid stream (segmented (with gas) or unsegmented flow) as well as the applied elements of instrumental system. In analytical practice, the techniques of flow injection analysis and sequential injection analysis are used most often. Due to constructional reasons, the use of systems containing valves of the type: Lab-on valve and various instrumental solutions of multicommutated techniques: multicommutated flow injection analysis, multi-syringe flow injection analysis and multi-pumping flow systems deserves special attention.
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