ICP Contaminants of Ethanol in HDPE

Robert and his associates were working on a health problem that he assumed was caused by an unidentified contaminant in ethanol. The ethanol was 96%, shipped in 50 gallon HDPE barrels, and then diluted with water to 36% for drinking. Robert suggested a possible source for a toxic contaminant might be a substance in the polyethylene matrix. He asked Paul for any suggestions of what substances present in HDPE could be leached out by 96% ethanol.

Dear Robert,

Hopefully the following will be of help in your investigation:

1) Trace metals from the catalyst residue. HDPE is prepared by a catalytic process where the catalyst is incorporated (entrapped) in the final product. The catalyst is typically an alumina or alumina/silica based catalyst with a mixture of Ti, and Mg chlorides (Ziegler-Natta type catalyst) plus other elements. Therefore look for trace metals such as Si, Al, Ti, Mg, Cr, Zn, Fe, etc. ICP-OES is a good technique to use for both qualitative and quantitative purposes.

2) If the drum has a 'color' then a dye or pigment is used. Take a sample of the drum HDPE and ash it in a Pt crucible by first igniting the HDPE with a propane flame and then taking the ash up to 500 °C in a muffle furnace. If there is no ash then a dye is the color agent. The presence of an ash that has the color of the drum is an indication of a pigment. In the case of a pigment the use of EDXRF can identify the elemental components and indicate the pigment used. Many pigments contain toxic elements such as As, Pb, Sb, and Cd. If an organic dye is used then extraction of the HDPE with a more non-polar solvent (such as methylene chloride) and identification by molecular spectroscopy (UV/VIS, IR and NMR) is adequate for identification (i.e., current data bases may allow for identification by IR alone).

In summary, catalyst residues and certain inorganic pigments should be of concern. Please note that contaminants do not have to be soluble, i.e., biological systems can be poisoned by particulate matter when ingested as could be the case with inorganic pigments and catalyst residuals. Organic dyes may have long term health problems but are less likely to be a problem.

If you have any other questions, please let me know.

Serving you in chemistry,

Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist

DISCLAIMER: Advice offered by the chemists at Inorganic Ventures is intended for the individual posing the question. Feel free to contact us to verify whether these suggestions apply to your unique circumstances.