D4413-98 – Standard Test Method Technical Guide

🧪 Overview and Scope of the Charcoal Tube Methodology

ASTM D4413-98 (Reapproved 2009) describes the determination of ethylene oxide (oxirane) in workplace atmospheres using charcoal tube methodology. This method is widely used for evaluating exposure to this major industrial chemical, which serves as a raw material and sterilizing agent. The procedure is compatible with low-flow personal sampling equipment operating from 10 to 200 mL/min and is suitable for both personal and area monitoring.

The method produces a time-weighted average (TWA) sample and can be adapted for short-term excursion (STE) measurements. All values stated in SI units are regarded as the standard. Quantitation is based on the comparison of peak heights or peak areas of the samples with those of standard solutions.

⚙️ Sampling Procedure and Analytical Specifications

A known volume of workplace air is drawn through a glass tube packed with activated charcoal. The tube employs a two-section design containing a front and a backup sorbent section. The backup section serves to adsorb vapors that penetrate the front section, enabling the analyst to determine if the collection capacity of the tube has been exceeded during sampling.

Following collection, the ethylene oxide is desorbed using carbon disulfide (CS₂). The resulting solution is analyzed by gas chromatography (GC) equipped with a flame ionization detector (FID). Recovery factors are determined by the same techniques used for the atmospheric analysis applied to known standards.

📊 Applicable Concentration Ranges and Performance

The standard defines specific performance ranges for different sampling objectives to ensure reliable data collection in compliance with occupational exposure limits (OELs). The values stated in SI units shall be regarded as the standard.

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