Patent ID: 7897331

Claim:
A method of measuring an analyte contained in a biological fluid, the analyte adapted to produce a proportional color change upon a reaction, the method comprising the acts of: providing a tetrazolium salt as an indicator, said tetrazolium salt having the formula of wherein: A=counter-ion a=1-3 b=0-3 X=1-6C alkyl or heteroalkyl R 1 =1-6C alkyl one of R 2 and R 3 is alkyl and the other is XN+H b (R 1 ) 3−b , or R 2 and R 3 form a methylene dioxy group one of R 4 and R 5 is halogen and the other is a halogen substituted 1-6C alkyl, both of R 4 and R 5 being XN+H b (R 1 ) 3−b , or R 4 and R 5 are joined to form an aromatic ring or a substituted aromatic ring; and determining the concentration of said analyte in said biological fluid with the assistance of said tetrazolium salt as the indicator.