Ultraviolet spectroscopy Santonox

Polyolefins Aqueous, alcoholic, oily Santonox R (4 4 thiobis-6-tert bicresol) antioxidant Ultraviolet spectroscopy a... 

A typical application of the procedure is given below, viz. the determination of down to 0.01% of Santonox R (4,4 -thiobis-3-methyl-6-tert-butyl phenol) in polyethylene. As this procedure determines Santonox R only in its reduced form it does not include any Santonox R which may be present in the oxidized form in the original polymer, for example produced by atmospheric oxidation of the additive during polymer processing at elevated temperatures. Total reduced plus oxidized Santonox R can be determined by ultraviolet spectroscopic procedures, for example, the differential procedure described later (Method 6) and oxidized Santonox can then be obtained by difference from the two methods. Alternatively, total unoxidized plus oxidized Santonox R can be determined by the direct ultraviolet spectroscopy. 

METHOD 6 - DETERMINATION OF SANTONOX R PHENOLIC ANTIOXIDANT IN POLYETHYLENE. ULTRAVIOLET SPECTROSCOPY. 

Determination of Santonox R 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. 

Elution with chloroform removes BHT only as the first fraction. Continued elution of the column with solutions of 10% water in methanol removes Santowhite powder or Santonox R as a separate pure fraction, free from BHT. Additives can then be determined in the respective extracts after they have been diluted to a standard volume with solvent by ultraviolet (UV) spectroscopy. 

Inspection of the ultraviolet (UV) spectra of synthetic cyclohexane solutions of each of these additives (Figure 12.1) shows that the Santonox R could he determined hy direct UV spectroscopy with little or no interference from either lonol CP or DLTDP by evaluation of the maximum occurring at 250 nm. However, lonol CP could not be determined by direct spectoscopy of the extractant by evaluation of its peak at 276 nm as Santonox R also has a maximum at this wavelength. 

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