As per USP what is the % RSD criteria for Normality or Molarity of three replicates of standardizations and for potentiometric standardization of sodium thiosulphate, Lead nitrate VS solutions which type electrode is used?
Volumetric solutions do not differ from the prescribed strength by more than 10 per cent. The molarity of the volumetric solutions is determined by an appropriate number of titrations. The repeatability does not exceed 0.2 per cent (Relative Standard Deviation). This is as per EP.
As per my knowledge the same limits should be applied to Volumetric Solutions as per USP.
Volumetric solutions of very low concentrations (i.e. 0.002M) is it possible to get %RSD 0.2%?
Yes, it is possible. This depends upon sharpness of the change of colour near the end point if manual titration is performed using colour indicator.
In potentiometric titrations (using electrodes) you should get desired RSD of 0.2%