Patent ID: 7317111

Claim:
A fluorescent compound of the general structure: where M is one of the alkali metals (Li, Na, K), ammonium (NH4), or pyridinium (Py), R 1 is a spacer comprised of 2 to 20 carbon, oxygen or nitrogen atoms, with the carbon containing sequences chosen from alkyl, alkenyl, arylalkyl, or alkoxy groups, which can bear any of several substitutions along the carbon chain, including but not limited to amino, carbonyl, carboxyl, hydroxyl, sulfonyl, sulfonamide, oxyethylene, ethylene oxide, or hydroxyl moieties, and, R 2 =—COOH, —SH, —NH 2 , —NCS, —NCO, —CO 2 NHS, NHNH 2 , -Maleimide, or Hydrazine.