Hello Lindy, I only have information from a question that was answered in the NBA forum. The information which I pasted below states not to use the NI after the hyphen in chemical isotopes.
This question was asked March 25, 2009.
Subject: ELI and NI in chemical isotopes
Question: When brailling isotopes in chemistry such as U-235, Ba-142, Kr-91, etc., are the ELI and NI used? Does it make a difference if the text is narrative or showing a reaction equation?
Answer: (Dorothy asked a Chemical Code Expert and then answered) Here is the answer I got: the Chem Code says that the symbol for an element is not an abbreviation by rule, so ... no ELI with a single element symbol and no NI with the number following the hyphen. I know it looks really weird, but that's the way it is.
Thank you for pointing out my error. After applying the Chemistry Code approach to chemical SYMBOLS (C is *not an abbreviation for carbon, it is the chemical SYMBOL for carbon), Section 11.d of the Nemeth Code is what to follow for C-14: no ELI, no NI. Section 9.f is followed for carbon-14 since carbon is a word: yes contract "ar," yes NI. Here is the path of Nemeth Code rules to follow when searching for hyphen rules:
NC §9.b. The numeric indicator must be used after a punctuation mark. However, the hyphen requires special attention (see section f below). [4 examples]
NC §9.f. The numeric indicator must be used after a hyphen when the hyphen follows a word, an abbreviation, or a mark of punctuation. However, also see §11d. [6 examples]
NC §11.d. The numeric indicator must not be used after a hyphen if the hyphen follows a numeral, a letter, or other mathematical expression. [3 examples]
I will delete my original answer so future readers are not misled.