Phthalates in soil: GC reveals industrial contamination
- Published: Jan 26, 2015
- Author: Steve Down
- Channels: Gas Chromatography
Ubiquitous phthalate esters
The prevalence of phthalate esters in all areas of our environment is indisputable. These manmade chemicals were manufactured for specific applications, mainly as plasticisers to make plastics more flexible but they are also added to adhesives, detergents, lubricating oils, and personal-care products such as soaps, shampoos, hair sprays and nail polishes. However, their physical binding to plastics rather than more permanent chemical binding has seen them leach out of the products and into the environment.
Countless reports have been published for detecting and measuring phthalates in milk, cosmetics, inhalers, plastic film, toys, soils, aerosols and water, to name just some of their common matrices. It is this pervasiveness that makes the regulatory authorities jittery because various phthalate esters, including the common ones, are thought to have adverse health effects on humans. Once ingested, they are excreted rapidly in urine but the continual exposure raises the risk. Some phthalates are potential carcinogens and others may affect the reproductive system.
One of the primary exposure routes around manufacturing facilities is soil and, from here, phthalates can evaporate or drain into water courses to spread their pollution. Despite the establishment of a number of methods for measuring phthalate esters in soil, generally by GC/MS or LC/MS, a team of Chinese scientists has developed a further method that uses GC with flame ionisation detection.
Yi-Kai Zhou and coresearchers from Huazhong University of Science and Technology, Wuhan, and the Suzhou Center for Disease Prevention and Control collected soils near to a factory that produced batteries, wires and cables and used a semi-automated procedure to extract the phthalates for analysis.
Gas purge microsyringe extraction
A total of 142 soils were taken from the roadside, farmland, non-cultivated fields and residential areas, all within 1 km of the factory. Other soils were collected from a remote control area that had little commercial activity or perceived industrial pollution.
In order to avoid contamination from phthalates in the apparatus, no plastic equipment was used as they inevitably contain phthalates. In addition, all glassware, filter papers and other equipment were thoroughly decontaminated before use.
Each sample was prepared for analysis by a technique known as gas purge microsyringe extraction. A small amount of soil was placed in the syringe then heated and purged with nitrogen gas to drive the phthalates from the soil into the gas phase. From here, they became adsorbed in a drop of ethyl acetate held at the tip of the microsyringe.
This drop was injected directly into the GC system and the phthalates were separated and detected with a flame ionisation detector. Their concentrations were measured from the GC peak areas relative to a known amount of benzyl benzoate that was added to each sample as an internal standard. Six common phthalates were targeted: the dimethyl, diethyl, dibutyl, butyl benzyl, diethylhexyl, and dioctyl esters of phthalic acid.
Phthalate distributions in different soils
The six esters were extracted in four minutes and analysed rapidly by GC, providing a simple and efficient method for their analysis in soils. Unsurprisingly, they were detected in all of the samples from the vicinity of the factory and from nearly all of the remote areas. The total concentrations were 8.63-171.64 and 2.21-157.62 mg/kg, respectively.
The most contaminated soils in the control area were farmland, followed by roadsides, residential areas and non-cultivated soil. Around the factory, the roadside soils were the worst, followed by residential areas, farmland and non-cultivated soil. In all cases, the most abundant ester was diethylhexyl phthalate which made up about 80% of the total concentrations in all types of soil. Other abundant phthalates near the industrial site were diethyl and dibutyl phthalate.
The levels of dibutyl and diethylhexyl phthalate were 3- and 10-fold higher in the soils from residential areas near the factory compared with remote residential areas. The concentrations of the phthalates from other types of soil differed by similar factors between the industrial and remote areas.
A statistical analysis of the levels of the individual phthalates in the various soils from the industrial and non-industrial areas indicated that the concentration of diethylhexyl phthalate had the closest correlation with total phthalate levels. So, this method could be used to gauge the total concentrations, without having to measure them all.
Science of the Total Environment 2015, 508, 445-451: "Analysis of phthalate esters in soils near an electronics manufacturing facility and from a non-industrialized area by gas purge microsyringe extraction and gas chromatography"
Article by Steve Down
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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