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Chelators …. Disodium EDTA vs Sodium Gluconate
Just recently started using Disodium EDTA as a chelator while working on formulas. But as I am working with a new emulsifier that is asking for Sodium Gluconate (as a stabilizer) which I understand is also a chelator, and a whole lot cheaper… Can I just use Sodium Gluconate as an across the board chelator, or are there some drawbacks (less effective?) ….or reasons that Disodium EDTA is so popular?
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5 Replies
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EDTA is one of the strongest chelates which can be used for many different applications/industries over a broad pH range. Depending on what you want to do, it may be better or worse than alternative chelates such as gluconate.Gluconate has one major drawback in cosmetics: with many metals it only forms stable complexes at high pH. It can also quite easily be broken down metabolically by all microbes -> a formulation which starts failing fill probably fail hard. -
Pharma said:EDTA is one of the strongest chelates which can be used for many different applications/industries over a broad pH range. Depending on what you want to do, it may be better or worse than alternative chelates such as gluconate.Gluconate has one major drawback in cosmetics: with many metals it only forms stable complexes at high pH. It can also quite easily be broken down metabolically by all microbes -> a formulation which starts failing fill probably fail hard.So what I hear you saying is: If I am using a formula that requests gluconate for the emulsifier…. I should still keep the EDTA in the formula?
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Which emulsifier does require gluconate and why?
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Pharma said:Which emulsifier does require gluconate and why?
AminoSensyl™ SC from Inolex….. they just say…it is a formula stabilizer. (It is cationic…if that factors in?)
Here is direct quote from their instructions: It is recommended to neutralize AminoSensyl™ SC with calcium gluconate or sodium gluconate.
Strong bases are not recommended for pH adjustment (e.g. sodium hydroxide).
• AminoSensyl™ SC performance is optimal at pH < 5.0
• The recommended ratio of AminoSensyl™ SC to calcium gluconate is 7:1. Specific levels of calcium gluconate
required will be formulation dependent.
The brassicyl valinate esylate provides a cationic charge at pH < 5.0
• AminoSensyl™ SC, like most cationic ingredients, is generally not compatible with anionic components
such as anionic emulsifiers, co-emulsifiers, polymers, etc.
• AminoSensyl™ SC is HLB independent. Additional emulsifiers are typically not required to form a stable emulsion. -
Okay, I see. The rather large amount of gluconate required (1/7 AminoSensyl) indicates that adding gluconate has nothing to do with chelation (gluconate at pH 5 does not act as chelate) but instead is an anion-exchange like turning sodium stearate into TEA stearate and salt. Gluconate is larger and more hydrophilic than the esylate anion. Although a weaker acid which probably reduces zeta potential, this 1:1 (estimated on a molar basis) switch mostly increases apparent HLB, increases Helmholtz plain thickness (= reduced coalescence), greatly increases interface curvature (= smaller emulsion particles), and ultimately boosts emulsion stability.Switching gluconate to EDTA also in an equimolar ratio (which is, from a chelation point of view, utter nonsense) might be somewhere between the effects of esylate and gluconate if it were not for the fact that EDTA at pH 5 carries two negative charges. As an educated guess, this makes it highly likely that you lose instead of win. Imagining you were to use phytate instead of EDTA, things would go from bad to worse. Using citrate instead… hard to say; it carries 1 1/2 negative charges at pH 5 but is comparatively small. What you gain from it as a weak chelate may not be worth the downsides regarding emulsion stability.However, if you need adding a chelate (as mentioned, gluconate at pH 5 is of no use as such), small amounts of EDTA might/should be tolerated. Noteworthy, do not subtract the amount EDTA from gluconate but add it in addition.
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