A method differing from the original method of activated carbon separation was introduced. Acetate fibre film separation

similar to that of cGMP determination was used. Comparison between the two methods showed that the efficiencies of isotope measurements are approximate while the significance test of the difference in regression cofficients for the two standard curves revealed

P

<

0.001

and that variations within and between batches were smaller than 10%

and the recovery more than 95%. However

the improved method was increased in sensitivity of measurement

regularity of results and simplicity of operation. It also had advantages such as higher working efficiency and less isotope pollution.