the sg of
pure ethylene glycol is 1.09678, propylene glycol 0.96527
so sg per se is not definitive re glycol if it is a blanket prohibition
ethylene based is the problem, propylene based is also used as a food additive (I believe)
if you can 'sell' the distinction then sg could be useful
http://cgi.ebay.com/Princo-Specific-...QQcmdZViewItem
these can be had in all ranges to varying accuracy, got to be temp compensated; there are ASTM and DIN procedures for use
- also automated setups
PH's strips are probably the easiest for 'no glycol'