On 2018 Feb 01, Misha Koksharov commented:

Use of metallochromic dyes and potentiometric pH-meter titration to detect binding of divalent cations to “Good’s” buffers: 4-morpholinepropanesulfonic acid (Mops) does not bind Mg2+

This is a very useful report and an educative methodological note. I also use MOPS buffer with Mg²⁺ in my work and I was a bit concerned if MOPS could affect the amount of free Mg²⁺ given some uncertainty in the literature.

In a recent review Ferreira et al (RSC Adv., 2015) also summarize that "there is no evidence of complex formation for MES, MOPSO and MOPS with the main metals present in environmental and biological studies. [...] Despite these reports of complexation, most of the authors agree that there is no evidence of significant bonding to metals and several studies specifically chose MES or MOPSO due to their inability to interfere with the most important metals in biological and environmental applications." Though, unfortunately they have missed the current paper.

On 2018 Feb 01, Misha Koksharov commented:

Use of metallochromic dyes and potentiometric pH-meter titration to detect binding of divalent cations to “Good’s” buffers: 4-morpholinepropanesulfonic acid (Mops) does not bind Mg2+

This is a very useful report and an educative methodological note. I also use MOPS buffer with Mg²⁺ in my work and I was a bit concerned if MOPS could affect the amount of free Mg²⁺ given some uncertainty in the literature.

In a recent review Ferreira et al (RSC Adv., 2015) also summarize that "there is no evidence of complex formation for MES, MOPSO and MOPS with the main metals present in environmental and biological studies. [...] Despite these reports of complexation, most of the authors agree that there is no evidence of significant bonding to metals and several studies specifically chose MES or MOPSO due to their inability to interfere with the most important metals in biological and environmental applications." Though, unfortunately they have missed the current paper.