There are plenty of reasons to include halogens in plastic, including impressive performance, relatively low cost, and availability. Unfortunately, these benefits come at a risk. Halogens are highly reactive and, if ignited in a fire, release toxic gases harmful to people and the environment. In addition, halogens can also be contaminants, causing corrosion or poor bonding.
To control the risk of halogens, environmental agencies in the US and Europe have standards for the use of and disposal of halogens. While these regulations don’t currently preclude the use of halogens, even more restrictions are on the horizon.
For companies who use plastics in manufacturing, measuring halogens in products and plastic waste is essential for remaining compliant in the future. And, as consumers are increasingly seeking out halogen-free products, tracking halogen levels may help companies determine ways to make more environmentally friendly products.
Combustion with Ion Chromatography (IC) is the ideal materials-analysis technique to determine if halogen levels are within regulation. The method is extremely sensitive, versatile and can simultaneously identify multiple halogens, including fluorine, chlorine and bromine. Plus, both the sample preparation and the testing process are relatively quick, allowing for results within one business day.
The Combustion Ion Chromatography Process
The process starts with Parr bomb combustion. A sample of the plastic is placed in an oxygen combustion vessel with sodium hydroxide. The vessel is then sealed and pressurized with oxygen. At this point, a nickel alloy wire is used to create a spark and combust the sample.
Combustion with oxygen converts the solid sample into soluble forms for IC analysis. After the vessel has cooled, the product is removed, and the vessel is rinsed with deionized water to recover the combustion products.
At this point in the analysis, Ion Chromatography is used to quantify the halogens in the sample. This is done by injecting the solution containing the combustion products into an Ion Chromatograph (a High Performance Liquid Chromatography (HPLC) system using a conductivity detector). The ions in the sample are separated in a column with an ion-exchange resin which attracts either anions or cations. Ion Exchange resins exchange anions for hydroxyl ions and cations for hydrogen ions. The column separates the cations and anions by their ionic strength. The existing ions are measured, and that information is captured in a chromatogram.
This IC chromatogram shows halogen concentration in parts per million (ppm) per gram weight of the sample. Based on the reported levels of fluorine, chlorine and bromine, a manufacturer can determine how best to dispose of their plastic waste.
Is Ion Chromatography Right For Your Next Job?
Measuring Halogen content is one of many applications for Ion Chromatography. For example, we have used it to validate the cleaning procedure for plastic parts and determine the source of ionic contamination on circuit boards.
The versatility of IC testing makes it a valued analysis technique for the environmental, industrial, biological, pharmaceutical, chemical and food testing sectors. But it may or may not be the perfect choice for your project.
With over 30 years of expertise in all the popular materials analysis techniques, you can count on us to find the perfect solution for any testing project — whether your goal is to identify halogens, quality control testing for plastic, or build better plastics.
Contact us to learn more.