List of commonly used solutes with stock and working concentrations, as well as notes.

Name Abbreviation CAS Number Molecular Weight (g/mol) Solvent Stock Concentration Working Concentration Storage Solution Lifespan Notes
Ampicillin (Sodium) Amp, A 69-52-3 371.4 Water 100 mg/mL 100 ug/mL -80°C 1-3 months Amp is less stable than Carb. Use carb when possible, even though it is more expensive. Carb reduces satellite colony formation. Ampicillin is stable at -80C for a year, and degrades within a month at -20C.
Carbenicillin (Disodium) Carb, C 4800-94-6 422.4 Water 100 mg/mL 100 ug/mL -20°C 12 months Prioritize this over Ampicillin.
Gentamicin Sulfate Gent, G 1405-41-0 477.6 Water 10-50 mg/mL 7 ug/mL -20°C 12 months
Isopropyl β-D-Thiogalactopyranoside (IPTG) IPTG 367-93-1 238.3 Water Variable-200 mg/mL Variable. 40ug/mL for DH10Bac plates -20°C 12 months I generally make fresh and immediately before use. Stocks can kept for a year.
Kanamycin Monosulfate Kan, K 25389-94-0 582.6 Water 50 mg/mL 50 ug/mL -20°C 6-12 months Generally stable.
Ruthenium Red RR 12790-48-6 786.4 Water 10mM 10uM -20°C 12+ months (likely more) Dissolve in milliQ water first. Transfer to tissue culture, and filter using 0.45um filter. Dispense into 2mL centrifuge tubes. Will turn rust brown when frozen.
Tetracycline Hydrochloride Tet, T 64-75-5 480.9 100% Ethanol/ DMSO 5 mg/mL 10ug/mL -20°C 12 months Ideal stock is 10 mg/mL, however tetracycline is rather insoluble. Dissolve 5 mg/mL on gentle rotation overnight in foil covered tube (is light sensitive, will turn brown when degraded) to solubilize. Store wrapped in foil to protect contents from light.
X-Gal X 7240-90-6 408.63 DMSO/DMF 20 mg/mL 100 ug/mL -20°C 6-12 months Light sensitive, store wrapped in foil. Consider making small aliquots to avoid freeze/thaw as this can degrade the compound.