@M5 Dan I use the Vanadium pentoxide (V2O5) 99% from russia hooked up on a doser 0.5ml every 2 days for 50 gallon system and my ICP was spot on.
I think this one got to be the same thing or at least very similar from Amazon UK:
Amazon product ASIN B09QJC5SDY
This one is the bottle I purshased from Amazon USA:
Amazon product ASIN B07H8MSKSL
My Recipe is base on the one that Randy posted:
Vanadium oxide (V2O5) is 56% vanadium by weight, so dissolving 4gr of it in a Liter of RODI water will result in a concentration of about 2,200 ug/mL.
1 mL of this added to 100 gallons (378.5 L) will boost vanadium by 2,200 ug/mL * 1 mL / 378.5 L = 5.8 ug/L.
That's too high, so if you dilute that stock solution using 100 mL of the previous mix into 1L of RODI then it is 1/10th as much, or 0.6 ug/L final concentration when dosed 1 mL to 100 gallons.
The Vanadium pentoxide is somewhat insoluble on water so to dissolve it you will need to add 1.8 to 2gr of Sodium Hydroxide (caustic soda/Lye) and stir vigorously.
Amazon product ASIN B0875LR274
I prefer to use a magnetic stirrer to mix my preparations for 30min, it is much eassier that way and I end by using a disposable coffee filter to strain any impurities that didnt get to mix from the final solution.
Amazon product ASIN B091XMT6CS
Note, the stock solution from the first 4gr of Vanadium last's a very long long time... already a year using it and I haven't used half of the diluted bottle hooked up on the doser. It doesn't seem to go bad or anything, and the bottle of V2O5 powder from russia is gonna last a life time.