PHARMACEUTICALS
This question is especially relevant in products formulated near-neutral pH. Many traditional organic-acidbased preservation approaches lose efficiency as pH rises, while some alternative multifunctional systems require use levels that are difficult to justify in high-volume products. In these systems, chelation is more than an optional add-on; it supports oxidation control, helps maintain foam consistency in hard-water conditions, strengthens preservative performance and contributes to overall shelf stability
Multi- vs. single-function
One approach is to move beyond a strictly single-function chelator mindset to a multifunctional metalmanagement system. Geogard NEU *, a patent-pending technology based on hydroxyacetophenone and copper gluconate, was developed in this context for personal care systems requiring product protection support at low use levels, particularly in neutral pH formulations. The material is water-soluble, supplied as a powder and typically used at 0.02-0.08 %, with 0.03 % identified as a practical starting point in many systems.
The formulation is notable because the two components address different but related stability pathways. The gluconate portion contributes intrinsic chelation and antioxidant support, while hydroxyacetophenone contributes antioxidant and skin-conditioning functionality. In practical terms, this means the blend changes the architecture of the formulation by combining trace metal management, oxidative protection and preservation support in a single low-dose system unlike traditional chelators.
From a chelation standpoint, the most relevant ions are usually not calcium and magnesium, although these remain important for surfactant performance and hard-water robustness. Iron and copper are often the more critical triggers for visible instability because they participate so readily in redox
Preservation system pH 5 pH 6 pH 7 Sodium benzoate Potassium sorbate systems 0.5 % sodium benzoate Pass Fail Fail
0.03 % Geogard NEU + 0.075 % potassium sorbate + 0.15 % sodium benzoate
0.03 % Geogard NEU + 0.15 % potassium sorbate + 0.30 % sodium benzoate
0.03 % Geogard NEU + 0.225 % potassium sorbate + 0.45 % sodium benzoate
Sodium dehydroacetate system
0.03 % Geogard ® NEU + 0.1 % sodium dehydroacetate
p-Anisic acid systems
0.03 % Geogard NEU + 0.5 % p-anisic acid
0.03 % Geogard NEU + 1.0 % p-anisic acid
cycling that accelerates downstream oxidation chemistry.
While EDTA is traditionally used to reduce the availability of trace metals and the trigger that initiates oxidative degradation, oxidation in personal care formulations is rarely driven by a single pathway. The copper gluconate / hydroxyacetophenone system takes a broader approach to product protection, addressing both the trigger and the downstream consequences of oxidation at similar levels.
The gluconate component contributes trace-metal management, helping to reduce the initiation of metal-catalysed oxidation, while hydroxyacetophenone provides complementary antioxidant support by helping to moderate oxidative processes that may still occur within a formulation matrix. As a result, the system is positioned as a multifunctional stability strategy that combines metal management and antioxidant support within a single low-use-level ingredient package.
Notably, copper is only a problem in an uncontrolled, reactive form. Geogard NEU uses copper in a managed form, alongside
Pass Fail Fail
Pass Pass Fail
Pass Pass Pass
Pass
Pass
Pass
Table 2- Representative rinse-off challenge-test matrix across pH
Note: Green cells- passing systems, red cells – failures, grey cells- conditions not shown in the source data
Pass
Fail
Pass
gluconate for metal control and hydroxyacetophenone for antioxidant support, so the formulation can benefit from copper without the typical stability concerns linked to free trace metals.
Comparison data shows gluconate salts to have very high reported stability constants for iron and copper in this comparison set, with values of log K 37.2 for Fe 3
+ and 36.6 for Cu 2
+, compared with 25.1 and 18.8 respectively for tetrasodium EDTA( Table 1). From the same data, 0.04 % of the Geogard NEU system provides approximately 0.79 mM gluconic acid and its salts, compared with about 0.75 mM delivered by a typical 0.05 % disodium EDTA use level. The log K values provide a useful screening rationale, but finished-formula performance still depends on pH, metal speciation, competing ligands and the full formulation matrix.
These values do not prove universal one-to-one replacement under all formulation conditions, but they do provide a strong rationale for investigating partial or full EDTA reduction in systems where transition-metal control is the primary objective. In practice, chelation
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