Voluntary end to the use of chromated copper arsenate in favour of alkaline copper quaternary for wood preservatives in the USA presents a challenge for titration
Very recently in the USA the Environmental Protection Agency and leading companies in the wood-preservative industry have come to an agreement to end the use and sale of all wood products treated with CCA (chromated copper arsenate).
CCA has been the most effective and economical wood preservative used in the industry to prevent against decay and rot.
There was however, a deal of concern about the environmental and possible health risks associated with the exposure and leaching of chromium and arsenic.
A result of this concern was that the EPA announced a voluntary decision by the wood-treating industry to phase out the use of CCA by the end of 2003, and will not permit the manufacturing of residential materials containing CCA after this date.
ACQ (alkaline copper quaternary), a quaternary ammonium cationic surfactant, will be the most widely used alternative to CCA in the United States.
It has been estimated that ACQ will cost 15-70% more than wood treatment with CCA.
This has introduced an increased cost to the chemical wood treatment industry.
To control these costs, it is essential to measure the ACQ by titration.
To be specific we are actually analysing for DDAC (didecyldimethyl ammonium chloride).
The American Wood Preservers Association (AWPA) method A18-99 calls for a lengthy two-phase Epton chloroform/water titration.
Traditionally surfactant titrations have been performed using the classic Epton titration method.
This method, although universally accepted, has several restrictions associated with it.
Chloroform is used in this titration which is now deemed hazardous, and due to the nature of the titration it can not be automated.
A Metrohm 809 Titrando with the Ionic Surfactrode (6.0507.120) using Hyamine as the titrant, can do the same titration.
The advantages are that the chemistry is virtually identical to the successful Epton titration, but without the chloroform, and the results obtained correspond exactly to that of the Epton titration.
In addition, the whole titration can be fully automated.
The AWPA method A17-97 describes the analysis of ACQ in solutions.
It is almost impossible to detect the endpoint colorimetrically.
Again a Metrohm 809 Titrando with a NIO Non-Ionic Surfactrode (6.0507.010) is the answer.
NIO electrode because as per method A17-97 lists using the NIO Surfactrode with the titrant sodium tetraphenylboron as a norm.
The NIO electrode is currently the only electrode on the market that the AWPA specifies is able to analyse suitably these quaternary surfactants.
Metrohm claims the largest range of surfactant electrodes available and a level of experience in surfactant analysis second to none.
