Any human sample can be used as a sub as long as the sub donor is indeed drug-free and not overhydrated.

As far as synthetics used in the past, Ive used the QF, the Magnum, and Ingology Golden Shower Enhancer brands - all with success. Of the three, Ive used the QF the most frequently, having first used it 13 years ago (back when it was available in the 4 oz bottle).