Chromogenic peroxidase substrates

A method for detection of a target in a sample by chromogenic detection, comprising:

• incubating a sample supposedly comprising a target in an aqueous solution, wherein the target comprises peroxidase activity or the target is directly or indirectly linked to a peroxidase enzyme, wherein the aqueous solution comprises:
• a) at least one chromogenic conjugate, wherein the chromogenic conjugate is a compound of Formula I:
• where X is —OH, —ORX or —NRXRXX,
• where Y is ═O, ═NRY, or ═N+RYRYY;
• wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, RX, RXX, RY, and RYY are independently selected from hydrogen and a substituent having less than 40 atoms;
• L is a linker comprising a linear chain of 5 to 29 consecutively connected atoms;
• and
• PS is a peroxidase substrate moiety;
• and
• b) a peroxide compound,
• at a time and temperature sufficient to form a colored precipitate of the chromogenic conjugate;
• detecting the colored precipitate of the chromogenic conjugate in the sample, thereby detecting the target in the sample.