Stability enhancement agents for use in a solidification matrices and solid detergent compositions are described. Stability enhancement is provided by a hydratable salt, water and phosphinosuccinic acid (PSO) derivative binding agents forming a dimensionally stable composition. Preferred phosphinosuccinic acid (PSO) derivatives include phosphinosuccinic acid and mono-, bis- and oligomeric phosphinosuccinic acid (PSO) derivatives. The stability enhancement composition for use in a solid detergent and solid detergent compositions are preferably biodegradable and substantially free of phosphate and NTA-free.