Gas chromatographic analysis of fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether

A method for producing fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether, said method comprising the steps of:

• (1) reacting together 1,1,1,3,3,3-hexafluoroisopropyl alcohol, hydrogen fluoride and a member selected from the group consisting of formaldehyde and paraformaldehyde, in the presence of sulfuric acid, such that a first crude fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether containing a first fluorinated ether by-product is prepared;
• (2) bringing said first crude fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether into contact with a member selected from the group consisting of an aqueous alkali solution and water, such that an acid component or said 1,1,1,3,3,3-hexafluoroiospropyl alcohol remaining after the step (1) is removed from said first crude fluoromethyl-1,1,1,3,3,3 hexafluoroisopropyl ether, and thus a second crude fluoromethyl-1,1,1,3,3,3 hexafluoroisopropyl ether containing a second fluorinated ether by-product is prepared;
• and
• (3) distilling said second crude fluoromethyl-1,1,1,3,3,3 hexafluoroisopropyl ether, thereby to produce said fluoromethyl-1,1,1,3,3,3 hexafluoroisopropyl ether,
• wherein at least one of an adjustment to the step (1) and an adjustment to the step (2) is conducted in said method, said adjustment to the step (1) being conducted by subjecting said first crude fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether to a first gas chromatography using a cross-linked cyanopropylmethylphenylsilicone capillary column, to determine a first content of said first fluorinated ether by-product, and then adjusting the step (1) depending on said first content, to decrease said first content, said adjustment to the step (2) being conducted by subjecting said second crude fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether to a second gas chromatography using a cross-linked cyanopropylmethylphenylsilicone capillary column, to determine a second content of said second fluorinated ether by-product, and then adjusting the step (2) depending on said second content, to decrease said second content.