Analytical Method: Sulfite in apples treated with sulfite

Instruments and Reagents:

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or

Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or

Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or

Cat.No. 109748  Spectroquant® Photometer NOVA 30 or

Cat.No. 109751  Spectroquant® Photometer NOVA 60 or

Cat.No. 173632  Spectroquant® Colorimeter Move 100

Cat.No. 114946  Rectangular cells 10 mm and/or

Cat.No. 114947  Rectangular cells 20 mm and/or

Cat.No. 114944  Rectangular cells 50 mm
Cat.No. 114394  Spectroquant® Sulfite Cell Test
Cat.No. 101746  Spectroquant® Sulfite Test
Cat.No. 109137  Sodium hydroxide solution 1 mol/l
Cat.No. 109533  MColorpHastTM pH-indicator strips pH 5 - 10
Cat.No. 116754  Water for analysis 
Membrane filter with 0.45 μm pore diameter
Sample preparation:
Chop exactly 100 g of the drained raw material in cooked and oxygen-free water for analysis with a mixer. Transfer the apple puree in a 1-l volumetric flask and fill up to volume with cooked, oxygen-free water for analysis. Stir the suspension in the closed vessel for 30 minutes with a magnetic stirrer. Filter off the solid parts through a folded filter.
Take 50 ml of the filtrate and adjust the pH value to 5 - 8 by using sodium hydroxide 1 mol/l (check with pH-indicator strips). Transfer this solution into a 100-ml volumetric flask and fill up to volume.
Attention! The sample should be prepared quickly to avoid any contact to the air.
Determine with the above mentioned test kits.
Sulfite content in mg/kg SO3 = analysis result in mg/l SO3 x 20


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