Paraphenylenediamine Stock Solution (10 mg/mL)

Prepare a bicarbonate buffer by dissolving 0.42 g of NaHCO₃ in 10 mL of H₂O. Adjust the pH to 9.0 with 5 n NaOH. Dissolve paraphenylenediamine in the bicarbonate buffer to a final concentration of 10 mg/mL. Store 10-µL aliquots in a freezer at −20°C. Discard when aliquots turn dark brown (6–12 mo).

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