I am interested in determining the amount of sodium diclofenac dialysed in a release study experiment. I am trying to avoid HPLC methods and I am oriented towards spectrophotometric methods. However, in a direct UV-VIS determination, the other constituents of my formulation interfere with my assay. I blame it on Tween 80 used as a surfactant in my formulation and in a high amount also. Any ideas on how to change this or maybe any information on other assays?
Dear Mr Cojacuru, it is possible to determine sodium diclofenac by direct UV-VIS in water. Pharmacopeia describes HPLC or potentiometric titration. However, potentiometry is only possible for pure sample (>99%). This is because excipients are Lewis base on acetic acid/acetic anidride medium and titrated by perchloric acid. Besides if you use glass electrode is necessary to change the KCl electrolyte from water to methanol. In this case, water is also a Lewis base in organic medium being also titrated. The article that I suggest (follow in attachment) uses UV-VIs. The principle is very simple. Sodium diclofenac is sparingly soluble in water, but in low concentration is completely soluble. This concentration is near to range of the spectrophotometer response. However, the excipientes when the sample is diluted in water are "insolubles". The measure is made at 276 nm. Another possibility is to use catalytic thermometric titration in organic solvents. I hope to have helped you.
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