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Significance and Use
Knowledge of the ultraviolet transmittance of monoethylene glycol is required to establish whether the product meets the requirements of its quality specifications.
Dissolved oxygen in organic solvents, such as MEG, forms complexes that shift the solvent absorption from the vacuum ultraviolet range into the measurable UV range (near 190 to 250 nm). Monoethylene glycol has a UV absorption peak at 180 nm. For MEG-oxygen complexes, this peak is shifted to a longer wavelength, thus increasing the absorbability at 220 nm.
However, this effect is not observed in water. There is no significant measurable effect due to dissolved oxygen in water that would require nitrogen sparging prior to using for collection of the reference spectrum.
Nitrogen sparging and re-measurement of suspect or borderline glycol samples at 220 nm can be used as a tool to rule out or confirm the presence of UV affecting contaminants other than oxygen.
1.1 This test method covers a procedure for the determination of the transmittance of monoethylene glycol (1,2-ethanediol; MEG) at wavelengths in the region 220 to 350 nm. The results provide a measure of the purity of the sample with respect to ultraviolet absorbing compounds.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.
1.4 Review the current Material Safety Data Sheets (MSDS) for detailed information concerning toxicity, first aid procedures, and safety precautions.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
E131 Terminology Relating to Molecular Spectroscopy
E169 Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
ICS Number Code 71.040.50 (Physicochemical methods of analysis)
UNSPSC Code 12352121(Organic hydroxides)