Ultraviolet spectroscopy phenolic antioxidants

METHOD 5 - DETERMINATION OF lONOL PHENOLIC ANTIOXIDANT IN POLYETHYLENE. ULTRAVIOLET SPECTROSCOPY. 

METHOD 7 - DETERMINATION OF 2,6-DITERT-BUTYL-4-METHYLPHENOL AND 4 SUBSTITUTED 2,6-XYLENOL PHENOLIC ANTIOXIDANTS IN POLYPROPYLENE. DERIVATIVE ULTRAVIOLET SPECTROSCOPY. ... 

Derivative ultraviolet spectroscopy is used to determine down to 0.01% 2,6 ditert-butyl-4-methylphenol and 4 substituted 2,6 xylenol phenolic antioxidants in polypropylene. 

Determination of lonol phenolic antioxidant in polyethylene. Ultraviolet spectroscopy... 

Ultraviolet spectroscopy is applicable to the determination of phenolic antioxidants in aqueous and alcoholic simulant liquids and also to one of the fatty simulants, liquid paraffin, recommended by the British Plastics Federation (BPF). Full details of the procedure, which is capable of determining down to 1-2 ppm of Santonox R in the simulent liquids, is given next. With the exception of the 5% citric acid simulent, errors are generally of the order of less than 10% of the determined concentration. Typical recoveries of Santonox R in the 5% citric acid extractant were between 15% of the expected result. 

These surfactants often contain a hindered phenol antioxidant to stabilize the polymer against degradation. Usually, a single antioxidant is present, and it may be determined by ultraviolet spectroscopy. The determination is also conventionally performed by reversed-phase HPLC or by gas chromatography, with or without prior derivatization. Positive identification of the stabilizer can usually be made by direct mass spectrometry. 

Soncek and Jelinkova have also used this differential principle to determine in polypropylene two antioxidants (2,6-ditert-butyl-4-methylphenol and 4-substituted 2,6-xylenol) which have virtually identical ultraviolet absorption spectra in the absence of alkali (method 7). The antioxidants can be distinguished in alkaline medium, where 4 substituted 2,6-xylenol forms phenolate readily, thus allowing the utilisation of the bathochromic shift for its determination. The use of derivative spectroscopy reduces light scattering and matrix interferences when extracts from polypropylene samples are measured. 

Methods 17 and 18, respectively, determine Cyasorb UV 531 (2-hydroxy-4-n-octoxybenzophenone) in polyolefins by direct infrared spectroscopy and thin-layer chromatography. Phenolic and organophosphorus type antioxidants do not interfere in these procedures. Method 19 describes an ultraviolet spectroscopic method for the determination of Tinuvin 326 ultraviolet absorber in polypropylene. 

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