Lauric diethanolamide liquid paraffin extractant

Determination of Lauric Diethanolamide in the Liquid Paraffin Extractant... 

Although complete or partial hydrolysis of lauric diethanolamide to DEA occurs with the four aqueous extractants, no such hydrolysis was expected in the case of a solution of lauric diethanolamide in the liquid paraffin extractant. 

DEA is water-soluble and can be determined by applying the periodic acid method to a water extract of the liquid paraffin/cyclohexane mixture. A small amount of DEA was found in the liquid paraffin extractant (less than 20% of the 20 ppm w/v of lauric diethanolamide present in the liquid paraffin before the extraction test, see Table 13.8, some of which was present as an impurity in the original batch of lauric diethanolamide used in this work. 

Table 13.8 Determination of lauric diethanolamide and DBA in the liquid paraffin extractant after 10 days at 60 °C ...

The results of these tests are given in Table 13.11. The total lauric diethanolamide content of the various extraction liqnids at the end of the test was between 3 and 13.5 ppm wiv, and maximum extraction occurred in the case of the liquid paraffin extractant, 5% sodium carbonate and 50% ethanohwater. 

In fact any of this additive which extracts from a polymer into distilled water at 60 °C is hydrolysed fairly completely within a few days. The analytical problem, resolves itself, therefore, into the determination of traces of DBA degradation product in the presence of relatively small concentrations of lauric diethanolamide. A method for the determination of lauric diethanolamide and DBA in the aqueous and alcoholic extraction liquids of the British Plastics Bederation (BPB) test conditions and in liquid paraffin is described next. 

Table 13.8 gives the results obtained in checks for the presence of DEA in synthetic liquid paraffin solutions of lauric diethanolamide after it had been heated for 10 days at 60 C. At the end of the extraction test, the solution (20 ppm w/v lauric diethanolamide) was diluted with cyclohexane and divided into two portions for determination of DEA and undegraded lauric diethanolamide. 

To determine lauric diethanolamide, a further portion of the cyclohexane solution of liquid paraffin was refluxed with 0.5 N sulfuric acid until complete hydrolysis to DBA had occurred. Under these conditions, a twenty-four hour reflux period was needed to hydrolyse lauric diethanolamide completely. Determination of total DBA in the water extract by the periodic acid method (Table 13.8) showed that the lauric diethanolamide recovery was reasonably near to the theoretical value. 

Detailed procedures are given next for the determination of lauric diethanolamide and DBA in amounts down to 3 ppm in aqueous extractants and in liquid paraffin recommended by the British Plastics Bederation. 

Finally, the extractability tests in 5% sodium carbonate and liquid paraffin were repeated several months later, on different samples of the polystyrene containing 1.5% and 2.0% lauric diethanolamide (Set 3), and the results obtained were very similar to those shown nnder Set 2. The extractability test procedure can be quite reproducible when carried ont on different occasions and on different batches of the plastic with a particular additive formulation. 

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