This implies that neutral ammonium acetate solutions electrosprayed in positive ion mode will likely undergo acidification down to pH 4.75 ± 1 in the ESI plume. Ammonium acetate does provide buffering around pH 4.75 (the pKa of acetic acid) and around pH 9.25 (the pKa of ammonium). ![]() Dissolution of ammonium acetate salt in water results in pH 7, but this pH is highly labile. NH4 + and CH3-COO- are not a conjugate acid/base pair, which means that they do not constitute a buffer at pH 7. The buffering range covers the weak acid pKa ± 1 pH unit. ![]() By definition, a buffer consists of a weak acid and its conjugate weak base. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. The present invention relates to a composition comprising : a) 0.01-20% wt/wt acetic acid and b) a physiologically tolerable buffer capable of maintaining acetic acid at a pH in the range of 2-7 and use of such a composition as an antimicrobial agent.The present invention relates to a composition comprising : a) 0.01-20% wt/wt acetic acid and b) a physiologically tolerable buffer capable of maintaining acetic acid at a pH in the range of 2-7 and use of such a composition as an antimicrobial agent.Īddressing a Common Misconception: Ammonium Acetate as Neutral pH " Buffer" for Native Electrospray Mass Spectrometry
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