was placed in an ultra sonication bath at 40 C/20 min. 2 ml of carrez
solution no. 1 was added and mixed, followed by addition of
2 ml of carrez solution no. 2. The solution was shaken vigorously
and allowed to stand at room temperature for 10 min; the final volume
was made up to 100 ml. It was then filtered through whatman
no. 1 filter paper. The filtrate was introduced into the SPE cartridge
for pre-purification.