A single character vector (or collection of character vectors)
from
"Compound", "CAS", "MW", "Raw.Experimental.Percentage.Unbound",
"Entered.Experimental.Percentage.Unbound", "Fub", "source_PPB",
"Renal_Clearance", "Met_Stab", "Met_Stab_entered",
"r2", "p.val", "Concentration..uM.", "Css_lower_5th_perc.mg.L.",
"Css_median_perc.mg.L.", "Css_upper_95th_perc.mg.L.",
"Css_lower_5th_perc.uM.","Css_median_perc.uM.","Css_upper_95th_perc.uM.",
and "Species".