EPA Method 8141 Standard Rev 1 Back Catalog number: 98131 Manufacturer: ABSOLUTE STANDARDS Availability: In the manufacturer's stock Price on request - + Recommended 11184.22-K-ME Sildenafil,1000 µg/mL,MeOH,1mL Price on request 682169 (-)-delta-9-THC, 10.0 µg/ml, Methanol, 1ml Price on request 50184 Ammonium (NH4+) Price on request