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1.1 This test method covers the determination of monomethyl ether of hydroquinone² (MEHQ) in colorless monomeric acrylate esters and acrylic acid. The test method is applicable to the determination of MEHQ in the concentration range from 0 to 1200 parts per million.

1.2 For purposes of determining conformance of an observed or a calculated value using this test method to relevant specifications, test result(s) shall be rounded off “to the nearest unit” in the last right-hand digit used in expressing the specification limit, in accordance with the rounding-off method of Practice E29.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 For hazard information and guidance, see the supplier's Material Safety Data Sheet.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.

4.1 Acrylic acid and its esters are normally inhibited with MEHQ only. This procedure presents a rapid and accurate method of determining the MEHQ content of fresh acrylic acid and acrylate esters in the absence of other inhibitors.

4.2 MEHQ effectiveness may decline with age and this decline in effectiveness may not be indicated by this test method.