Significance and Use
5.1 Preliminary studies have identified polymeric organic compounds as contaminants in treated drinking water, wastewater, surface water, ground water, and marine waters. These polymers may be harmful to the environment and adversely affect human health, and in these circumstances, mass estimation is commonly required. A universal, analytical method will help to normalize data from around the world and better understand which polymers are most frequently found in various climatic and geological locations (5-7). Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has many advantages in that both polymer identification and mass quantification can be easily accomplished by chromatographic separation in combination with mass spectral analysis.
Scope
1.1 In this pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) test method, an analytical protocol validated specifically for the analysis of water with high to low suspended solids is described. This test method will standardize the identification and simultaneous quantitation of organic polymer particles and fibers in water. It has been designed for and applies to all microplastic particles and fibers, and is intended for use with treated drinking water, surface waters, wastewater influent and effluent (secondary and tertiary), and marine waters. This test method is not limited to these particular water matrices; however, the applicability of this test method to other aqueous matrices shall be demonstrated.
1.2 Microgram quantities of a sample containing microplastics are pyrolyzed (Py) at 600 °C. The pyrolyzates are separated on an analytical column (GC) and detected using a 70-eV electron impact mass spectrometer (MS). Polymers often have similar pyrograms, making it difficult to differentiate the pyrolyzates for a given polymer from those of the composite sample. In this test method, ion ratios at predetermined retention times to facilitate the identification of each polymer present in a sample containing microplastics are compared.
1.3 This test method is to be used in conjunction with Practices D8332, D8333, and D8402. These ASTM International standards enable the collection and preparation of water samples with high, medium, or low suspended solids for the identification and quantification of microplastic particles and fibers without compromising the integrity of the microplastics. This test method is applicable to microplastic fibers and particles, including sizes defined as a nanoparticle; this is a natural extension of this test method because Py-GC/MS technology responds to the total mass of the sample independent of individual particle sizes. The uniformity of particle size influences the reproducibility of the pyrogram and samples with microplastics should be reduced to a fine powder with the final particle size diameter on the order of less than 0.2 mm.
1.4 It is the responsibility of the user to ensure the validity of this test method for untested matrices.
1.5 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
