BS ISO 15033:2018 pdf download – Plastics — Determination of caprolactam and its cyclic and linear oligomers by HPLC This document describes a high-performance liquid chromatography (HPLC) method for determining the concentrations of cyclic oligomers of caprolactam, from 0,01 % by mass upwards, and linear oligomers of caprolactam, from 5 mg/kg upwards, both up to and including the hexamer of caprolactam (n = 6), in samples of polyamide 6, caprolactam and mixtures of rearrangement products in water. A second, significantly faster, HPLC method is included for determination of caprolactam and its cyclic dimer, based on the same principle and using the same equipment as the first method. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 472, Plastics — Vocabulary 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 472 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia.org/ — ISO Online browsing platform: available at https://www.iso.org/obp 4 Principle A test sample is dissolved in, or diluted with, formic acid and the oligomers separated in the presence of a low-pH mobile phase using a column filled with reversed-phase packing material. The cyclic oligomers are detected by UV absorption at 200 nm. If desired, the linear oligomers can be detected by fluorescence after post-column reaction of the primary amino group with 1,2-phthalic dicarboxaldehyde and 3-mercaptopropionic acid. The concentrations are calculated by comparison of the measured values with those of calibration solutions. 5 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade. 5.1 Water, ultrapure or double-distilled. 5.2 Phosphoric acid, 85 % by mass. 5.23 Post-column derivatization reagent. Dissolve 76 g of sodium tetraborate decahydrate (5.18) and 6 g of sodium hydroxide (5.19) in 2 l of water (5.1). Dissolve 1,6 g of 1,2-phthalic dicarboxaldehyde (5.20) in 40 ml of methanol (5.21) and add this solution to the sodium tetraborate decahydrate reagent. Add 1,5 ml of 3-mercaptopropionic acid (5.22) and mix well. The stability of the post-column derivatization reagent is limited. Do not keep for longer than 3 days. NOTE The cyclic dimer, the cyclic...
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