The search for a cost effective alternative to the two most frequently used chelating agents NTA
(nitrilotriacetic acid) and EDTA (ethylenediaminetetraacetic acid) has long been an industry target.
Such an alternative has to possess a good ecological and toxicological profile. Adding a third
requirement; that the product should largely be made from renewable sources, gave the R&D work
a new dimension.

Whilst developments have largely been driven by the I&I formulators desire for a greener portfolio of
raw materials, extra impetus has come from customers of the formulators who have made the
decision in the past to restrict the use of EDTA. In fact, contrary to earlier beliefs, biological pathway
studies have shown that EDTA is biodegradable in the environment and has a well tested and good
toxicological profile. As a consequence, the limited risks to man and his environment are identified
and more importantly they are also easily managed. However, with the decision to replace EDTA
made before this was all known, an alternative is still needed.

There are a number of alternative products on the market which claim to be as effective as EDTA and
NTA but most also have their restrictions. For example; organophosphonates were found to be not
readily biodegradable. Others are readily biodegradable, such as citrates and gluconates, but do not
have a sufficiently strong chelating power compared to NTA or EDTA. It has therefore been difficult to
find a good solution that matches the performance profile of traditional chelating agents.

To meet the stringent -green- requirements, Akzo Nobel has an ongoing R&D program for new products
as part of which it has introduced Dissolvine® GL. This product contains GLDA (GLutamic acid DiAcetic
acid). GLDA is a direct alternative to NTA and EDTA, fulfilling all of the targets set above.

Dissolvine® GL is classified as readily biodegradable (> 60% degraded within 28 days) according to
the internationally recognized OECD 301D test protocol. The product consists only of L-GLDA. This is
significant because the D-form is not biodegradable (see Figure 1). This exclusivity for the L form is
based on the fact that it is made of a naturally occurring amino acid, L-Glutamic acid. This material is
food approved and regarded as a safe food additive (US EPA GRAS). It is used in many foodstuffs to
improve flavor properties. L-Glutamic acid is a toxicologically sound building block.

From a carbohydrate source such as sugar, molasses, corn or rice, GLDA is produced using a
biochemical process to give the pure L-isomer that is required to meet the readily biodegradable
profile. The material is later modified using proprietary Akzo Nobel technology to produce a strong
chelating agent. GLDA has been refined and improved, based on experience gained from other
chelating agents, to yield a product with excellent sequestering power and solubility.

A large number of toxicity tests reveal that GLDA is not a dangerous chemical (no CMR) and has
excellent properties with regard to eco and human toxicity. GLDA can be regarded as non hazardous
when put into water (NWG according to German Water Endangering Class).

With respect to the green nature of the GLDA; the molecule is largely based on natural, replaceable
and sustainable raw materials (see Figure 2). According to the Bra Miljöval protocol of the Swedish
society for Nature conservation it is 86% based on renewable resources, a much higher proportion
than for other chelating agents.

In trials, GLDA has proved to have an optimal balance between biodegradability, metal chelation and
ease of use. Unusual, but interesting physical properties include high water solubility over a wide pH
range (see Figure 3). For example, GLDA is about 40 weight % soluble in water at a pH of 3.
This is high in comparison to the classical chelating agents like EDTA which have approx. 0.1 weight %
solubility under similar conditions. This is significant for cleaning products (such as cleaning in place)
that are formulated at low pH.

EDTA and NTA are known to be thermally stable (> 150 °C). In thermographic experiments GLDA
is surprisingly stable. When tested at temperatures > 300 °C it showed no significant decomposition.
This property has been used to develop water treatment systems for operating boilers to reduce the
effect of hard water metals and other metals released into the water due to operating conditions e.g. iron.

GLDA behaves similarly in cleaning formulations to liquid NTA and EDTA making their replacement
possible without major modifications to the surfactant systems. The benefit of GLDA in such formulations
is its broad effective pH range for the chelation of the hard water ions even at very high pH levels (> pH 11).
This is significant, because it also has a high solubility in sodium hydroxide based systems. Tests have
shown up to 10 times higher solubility levels in 25% NaOH solution compared to products like the sodium
salts of EDTA and NTA (see Figure 4). This creates the opportunity for formulators to work with either more concentrated formulations due to the higher water solubility and / or formulations containing higher levels
of sodium hydroxide that are currently restricted due to the solubility of other chelating agents.

GLDA is an excellent alternative to NTA and EDTA in all of the normal Industrial cleaning applications.
In addition it has further potential uses in the strongly alkaline hard surface cleaning agents used in food
processing, kitchen cleaning and automatic dishwashing products.

There is also an increased interest in the use of disinfectants in formulations. Like EDTA, GLDA can be
used in combination with biocides to improve the biocidal performance of a disinfection system. GLDA is
not a biocide but is believed to chelate calcium ions in the bacteria cell walls whereby the bacteria become
more sensitive to the active biocides. The use of a biodegradable chelating agent in such a system is novel.

GLDA is used in personal care and cosmetic products. The product is listed under INCI as Tetrasodium
Glutamate Diacetate. GLDA is free from genetically modified raw materials and is not irritating to skin or
eyes, properties which are attractive in the development of new products.

Replacing the classical chelating agents, NTA and EDTA, is a difficult task for the formulator. However,
GLDA has proven to be an effective alternative to these products in commercial applications and it
distinguishes itself from other potential replacements in its natural amino acid raw material base, its
strong chelating power and its unusual physical chemical properties. In conclusion, GLDA enables the
formulator to develop products that are cost effective with a brighter environmentally friendly future.

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