With some flavors I can tell the PH is high because the nicotine gives me a bitter aftertaste in my mouth. PG has a low PH level and VG has a higher PH level so I usually just add a little PG to tone it down a bit. It's not very scientific but it works for me. Some flavors I don't seem to notice it at all.
Just read what I wrote... does that make
sense? lol