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D2930-03 – Standard Test Method Technical Guide
The ASTM D2930-03 standard defines a potentiometric titration method for quantifying free maleic acid in refined maleic anhydride. This technique is essential for assessing moisture contamination, as maleic anhydride readily hydrolyzes to maleic acid. The method is applicable for all concentrations but is primarily used for levels below 0.5%.
📋 Test Method Overview and Significance
This test method covers the determination of free maleic acid in refined maleic anhydride by direct titration with a tertiary amine base in an anhydrous solvent system. The titration is followed potentiometrically using a pH meter. Tertiary amines are specifically chosen because they do not react with anhydrides, and only one carboxylic acid group is titrated. The maleic acid content serves as a critical indicator of product quality, reflecting exposure to moisture during handling or storage. For purposes of determining conformance, observed or calculated values must be rounded to the nearest unit in the last right-hand digit of the specification limit, in accordance with Practice E 29.
⚙️ Apparatus and Reagent Specifications
The standard requires specific apparatus for accurate titration. The electrodes of the titrimeter or pH meter must extend well below the liquid level. A mechanical stirrer is needed for rapid stirring but must avoid drawing air bubbles to the electrodes. An automatic titrator can be used as an alternative. All reagents must be reagent grade conforming to ACS specifications, and water used must be Type IV per ASTM D 1193. Other grades may be used only if they do not lessen the accuracy of the determination.
| 🟦 📏 Apparatus | 📐 🎯 ⚡ Specification |
|---|---|
| Titrimeter or pH Meter | With glass and calomel electrodes mounted below liquid level |
| Microburet | 5 or 10 mL capacity, graduated 20 divisions/mL |
| Mechanical Stirrer | Rapid stirring without air bubble formation |
| Beaker | 250 mL, tall-form |
| 🟦 📏 Reagent | 📐 🎯 ⚡ Requirement |
|---|---|
| Chemicals | Reagent grade, per ACS Committee on Analytical Reagents |
| Water | Type IV, per ASTM D 1193 |
📊 Titration Procedure and Key Parameters
The sample is dissolved in an anhydrous solvent and titrated directly with a tertiary amine base. The endpoint is detected potentiometrically using a pH meter. Proper electrode immersion and stirring intensity are critical for repeatable results, avoiding air bubbles that could interfere with the reading. The method is specific to maleic acid, with no interference from the anhydride, and is optimized for concentrations below 0.5%. An automatic titrator can be substituted to streamline the process while maintaining accuracy.
💡 Tip: Calibrate the pH meter before each use and ensure electrodes are clean and fully submerged to achieve consistent potentiometric readings.
⚡ Warning: Consult Section 7 of the standard for specific hazard statements. Use appropriate personal protective equipment when handling reagents, and follow OSHA regulations as referenced (29 CFR 1910.1000 and 1910.1200).
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D2930-03?
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.