What, precisely, does the term "total RNA" mean

I'm a science editor and the manuscript I'm working on treats the phrase as both singular and plural in different parts of the paper, probably because there are multiple authors. My problem is that I don't know if the wording should be "total RNA was extracted" or "total RNA were extracted." I'm assuming it should be treated as singular, like cDNA, etc. because I'm assuming that various types of RNA are extracted as a lumped-together product. I would ask this in the grammar area but I doubt anyone but a cell biologist-type will know the answer.

In my opinion as a non-native English speaker, but experienced molecular biologist, it should be singular, so "total RNA was extracted". Sometimes, you might see "mRNAs were extracted" but that clearly refers to multiple molecules.

Total RNA refers to all RNA from a sample, so including mRNA, tRNA, and rRNA.