A water-soluble reference standard is useful for immunoassays of a lipophilic
drugs.
The reference standard is a compound of formula (I):
G-(L)n—Y; (I)
where G is a lipophilic drug; L is a linker which is an alkyl group or heteroalkyl
group containing from 1 to 20 carbon atoms; n is 0 or 1; and Y is a water-solubilizing
group such as —SO3-, —NR—SO3-,
—P(O)(OH)(O-), or —O—P(O)(OH)(O-);
where R is H or an alkyl group of 1 to 10 carbon atoms.
