What are the reasons for low concentration in determination of tablet dosage form by differential pulse voltammtery on hanging mercury electrode? How can I solve this problem?
You are asking why is possible to attain so low concentrations in tablets dosages using mercury electrodes?
There are many reasons; one is because mercury is the best electrode to work in the reductive potential window. If you have low background current, you can go to lower concentrations. The second is because the electrode is renewable and this avoid fouling of its surface. The third is due the fact that the surface of mercury is "perfect" and a good mercury electrode renews its drops with high reproducibility. Other aspects can be enumerated: the good conductivity of mercury. In some cases, some species are "attracted" to the mercury surface (and so we can use the adsorptive process for accumulation of this specie and consequently obtain more sensitivity). Therefore, mercury electrode is a very interesting sensor, unbeatable for many applications.
Dear Wafa, can you describe more precisely your problem. Lucio gave an excellent answer regarding the advantages of mercury electrode in low concentration measurements. However, if you obtain lower concentration than the added quantity it is a problem indeed. Please, describe your experiment and give an example of the problem. May be I can propose you something if i have more info.
Trace determinations are very important and the use of differential pulse mode of voltammetry is to increase the sensitivity by 1000 times than normal pulse technique. In application for tablets determinations is to be sure of the contents and to control the dosage forms. Also you may be able to determine the drug contents in blood, in serum even in urine i.e after time intervals or kinetically. You may determine after what time the drug is converted not only this but, to determine whether it is released from the boody and so on. The advantages of Hg electrode is well known as renewal, its higher overpotential, form amalgam with many metal ions...Still the point is the sensitivity of the technique and the quality of determinations in terms of SD, RSD and the detection limit of the procedure.
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