Measurement of Respirable Superabsorbent Polyacrylate (SAP) Dust by Ethanol Derivatization Using Gas Chromatography-Mass Spectrometry (GC-MS) Detection

Abstract

Superabsorbent polyacrylate (SAP) is an important industrial chemical manufactured primarily as sodium polyacrylate but occasionally as potassium salt. It has many applications owing to its intrinsic physical property of very high water absorption, which can be more than 100 times it own weight. SAP is commonly used in disposable diapers and feminine hygiene products and is known by a number of synonyms—sodium polyacrylate, superabsorbent polyacrylate (SAP), polyacrylate absorbent (PA), and superabsorbent material (SAM). Germany and The Netherlands have adopted a nonbinding scientific guideline value 0.05 mg/m³ (8-hr time-weighted average, TWA) as the maximum allowable workplace concentration for the respirable dust of SAP (<10 μm particle diameter). Three industry associations representing Europe, the United States, and Asia have adopted the German scientific guideline value of 0.05 mg/m³ (8-hr TWA) as a voluntary guideline. A new test method based on alcohol derivatization of the acrylate was developed and validated for the analysis of respirable superabsorbent polyacrylate dust collected on filter cassettes in the workplace environment. This method is an alternative to the commonly used sodium-based method, which is limited owing to potential interference by other sources of sodium from the workplace and laboratory environments. The alcohol derivatization method effectively eliminates sodium interference from several classes of sodium compounds, as shown by their purposeful introduction at two and six times the equivalent amount of SAP present in reference samples. The accuracy of the method, as determined by comparison with sodium analysis of known reference samples, was greater than 80% over the study range of 5–50 μg of SAP dust. The lower reporting limit of the method is 3.0 μg of SAP per sample, which is equivalent to 3 (μg/m³) for an 8-hr sampling period at the recommended flow rate of 2.2 L/min.

Keywords:

• SAP
• sodium polyacrylate
• superabsorbent material
• superabsorbent polymer

ACKNOWLEDGMENTS

The authors would like to thank the principal investigators, Mr. Timothy Fields, Mr. Patrick Coonan, and Dr. Kristine Kurtz of Bureau Veritas North America laboratory in Novi, Michigan, for their efforts in investigating, refining, and studying the ethanol esterification method, as well as Dr. Ottmar Wink and Mr. Ferdinand Schack of AllessaChemie GmbH (Frankfurt, Germany) for additional work on laser diffraction studies of milled samples and comparative esterification studies. This project was funded by The Institute for Polyacrylate Absorbents, Inc.