Patent ID: 7824483

Claim:
A composition comprising a compound of Formula (1) or a salt thereof and compound of Formula (2) or a salt thereof: wherein: A is an aryl or heteroaryl group; Q 1 and Q 2 each independently is an optionally substituted phenylene group; R 1 , R 2 , R a and R b each independently is H, optionally substituted alkyl, optionally substituted aryl or optionally substituted arylalkyl; each W 1 , W 2 , W 3 and W 4 independently is a —CO 2 H, —SO 3 H, —PO 3 H 2 group or an alky substituted with one or more groups selected from the group consisting of —CO 2 H, —SO 3 H, and —PO 3 H 2 ; each S 1 , S 2 , S 3 and S 4 independently is a substituent other than those defined for W 1 , W 2 , W 3 and W 4 ; a and d each independently is from 1 to 5; b and c each independently is from 0 to 4; (a+b) has a value of from 1 to 5; (c+d) has a value of from 1 to 5; e and h each independently is from 1 to 7; f and g each independently is from 0 to 6; (e+f) has a value of from 1 to 7; and (g+h) has a value of from 1 to 7.