February 17, 2019
Dr. Brian Drollette, Ph.D., senior scientist at Exponent, had recently co-authored an article, "Oligomer-Specific, Short Chain Linear Alcohol Ethoxylate Quantification via Comprehensive Two-Dimensional Gas Chromatography" that was published in Environmental Science and Technology Letters. This article details an analytical method to detect and quantify a class of surfactants in environmental samples. The method uses comprehensive two-dimensional gas chromatography (GCxGD) coupled with a novel quantification procedure to help understand the concentration nonionic surfactants in a wastewater effluent discharged to a river. This article is the first of its kind to demonstrate the capability of GCxGC for quantification of nonionic surfactants.
Non-ionic linear alcohol ethoxylated surfactants (LAEs) make up a broadly utilized class of compounds commonly employed in unconventional hydraulic fracturing activities. However, current detection and quantification methods fail to operate in relevant concentration ranges and are limited in specificity because of a lack of access to all analytical standards for individual LAE oligomers. Here, we present a novel extraction and quantification technique for aqueous samples containing both petroleum hydrocarbons and short chain LAEs with alkyl chain lengths of 6 — 10 carbons and 0 — 9 ethylene oxide groups. Using liquid — liquid extraction and two-dimensional gas chromatography with flame ionization detection, the method provided over 80 and 100% recovery of LAEs and n-alkane hydrocarbons, respectively. Individual LAE oligomers were quantified using calibration curves of n-alkanes and adjusted response factors based on the effective carbon number (ECN) concept, and we present a detailed framework for calculating ECN using primary alcohol standards and ether functional group contributions. This method was applied to a centralized waste treatment facility effluent discharging directly into a local river in Pennsylvania and indicated parts per million-level discharges of individual oligomers. This first demonstration of LAE and petroleum hydrocarbon quantification will gain utility as researchers seek to understand the environmental fate of these industrially important chemicals.
To read the full article, click here.