The attached files may be of your use.

Please have a look at these PDF attachments also.

Gravimetric determination of tannins:

About 110 ml of the extract prepared was divided into two portions of 65 ml and 45 ml. The PVP (6.5 g, 50 mg/ml) was added to the former after diluting 1 : 1 with distilled water, the mixture stirred for 15 min at about 4°C, centrifuged and supernatant collected. Two disposable aluminium weighing dishes, one for the PVP treated and other for the untreated extracts were weighed. Aliquots (10 ml of untreated and 20 ml of the PVP treated extracts) were pipetted into the respective dishes and dried to a constant weight (about 30min for the untreated and 60min for the treated extracts) on a hot plate or in an oven at 100°C. The dishes were transferred to a desiccator and weighed when room temperature was achieved. This procedure of drying the aliquots and weighing was repeated three times to obtain four values for each treated and untreated extract. The values observed did not deviate by more than 5% from their mean. The average weight corresponded to 10 ml of the undiluted extracts. Thus, the difference in weight for the treated and untreated extracts gave the weight of tannins in 10ml of the extract or 200mg of the leaves. The results were expressed as percent tannins on dry matter basis.

Thanks a lot to all researchers for providing fruitful information regarding gravimetric determination of tannins.