Yes, mass-spectrometry-based metabolomics can be performed on as little as 20ul in certain cases, and 80ul is certainly enough. Below are a few studies from other authors and platforms, and there are many more out there.

https://arthritis-research.biomedcentral.com/articles/10.118... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8340475/

Specifications by an academic metabolomics facilty: https://www.embl.org/groups/metabolomics/faq/

Regarding your Theranos comment: You are absolutely right. This is something we will have to deal with, and where are actively working on our messaging.