Pokegama Technologies is now offering through Kerafast, the first of the MetalloBuffer series of Zinc Ion Calibration Buffer Kits. These kits allow you to easily make buffers with accurate and reproducible levels of free zinc ions at levels between 10-13 and 10-7 molar to calibrate any zinc sensor you might be using: ZinPyr-1, FluoZin-3, Newport Green DCX, etc., as well as the fluorescent zinc biosensors, such as H94N-apoCA-TagRFP.
As many of you know, it is very difficult to accurately make calibration buffer solutions with low (submicromolar) concentrations of free zinc ion, for two reasons: first, even reagent grade buffer salts have significant quantities of metal ion impurities that are likely to interfere, such as Cu2+ or Ni2+ ; and second, they may contain other ligand impurities that bind or precipitate the zinc ion, lowering the effective concentration. To avoid this problem, investigators for many years have formulated buffers with zinc ion and ligands that bind nearly all the zinc ion (in this case), such that only a small, known proportion is free. Thus, if there are interfering metal ions or contaminating zinc ions present, they are bound by the ligand and their effect is minimized; similarly, the effect of contaminating ligands is minimized. A fuller description with references (and much else) can be found on the Pokegama Technologies website.
Now available through Kerafast two zinc MetalloBuffer Calibration kits: one covering pZn 7 – 11 ([Zn2+]free from 10-11 molar to 10-7 molar; Kerafast catalog no. KPG003) and one covering pZn 9- 13 ([Zn2+]free from 10-13 molar to 10-9 molar; Kerafast catalog no. KPG002); both are at pH 7.5. The kits have easy-to-follow directions included.
Kerafast, Inc.: <https://www.kerafast.com/cat/961/free-zinc-biosensors>