Determination of Fluorine in Fluorinated Polymers. Oxygen Flask Combustion - Spectrophotometric Procedure

Method 2.4 Determination of Fluorine in Fluorinated Polymers. Oxygen Flask Combustion - Spectrophotometric Procedure [39] 

This oxygen flask combustion spectrophotometric procedure is capable of determining fluorine in fluorinated polymers such as PTFE in amounts down to 0.5%. 

The combustion apparatus consists of a silica or boronfree glass 500 ml Erlenmeyer flask constructed of suitable glass (see Method 2.2). Into the stopper is fused one end of a length of platinum wire, 1 mm in diameter, to the free end of which is attached a piece of 36 mesh platinum gauze, 1.5 cm x 2 cm to act as a sample holder. The flask shall be essentially free from boron and aluminium. Low results are obtained using borosilicate glass flasks. 

Optical densities were measured in 4 cm cells with a Unicam SP600 visual range 

Alizarin complexan, 0.0005 M, transfer 0.385 g of alizarin complexan to a 2 litre calibrated flask by means of 20 ml of recently prepared 0.5 N sodium hydroxide and set aside for 5 minutes with occasional swirling, to ensure complete solution. Dilute to about 1500 ml with water, add 0.2 g of hydrated sodium acetate and adjust the pH to about 5 by careful addition of 1 N hydrochloric acid. Dilute to the mark and filter into a brown glass bottle. Tbis solution is stable for at least 4 months. 

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