The physics
Copper(II) complexes absorb light in the red and orange region through d-d electronic transitions, transmitting blue. The exact shade depends on the coordinating atoms, which is why GHK-Cu has its particular blue rather than the colour of another copper salt.
Why it is useful
The colour is a genuine, if coarse, indicator. A GHK-Cu preparation that is colourless has a problem: either the copper is absent or the complex has not formed. That is a check available without instrumentation.
It is not a purity assay. Colour confirms a copper complex is present, not how much or how pure.
What to expect
Lyophilized GHK-Cu is a blue powder and gives a blue solution on reconstitution. Depth of colour varies with concentration. A marked change in shade or precipitation of coloured material suggests the complex has been disturbed.
Research use only. This page is explanatory and does not recommend any use, quantity or procedure. REVIVE LAB supplies reference materials for laboratory research. These are not medicines and are not for human or veterinary consumption. Anyone considering the use of any compound in humans should do so only under qualified medical supervision.