Zinc Citrate Dietary Supplement USP Grade:
C12H10O14Zn3-2H2O --- 610.36
2-Hydroxy-1,2,3-propanetricarboxylic acid zinc salt, dihydrate CAS 5990-32-9
Anhydrous CAS 546-46-3

DEFINITION
Zinc Citrate contains NLT 31.3% of zinc (Zn), calculated on the dried basis.

ASSAY
Procedure
Sample: 350 mg of Zinc Citrate, previously dried at 105C for 2 h
Blank: 60 mL of water
Titrimetric system
Mode: Direct titration
Titrant: 0.05 M edetate disodium
Endpoint detection: Visual
Analysis: Dissolve the Sample in 60 mL of water. Add 10 mL of ammonia-ammonium chloride buffer and 0.1 mL of eriochrome black. Titrate with the Titrant to a blue endpoint. Perform a blank determination.

Calculate the percentage of & zinc (Zn) in the portion of Zinc Citrate taken:
Result = [(V − B) x M x F x 100]/W

V = sample titrant volume (mL)
B = blank titrant volume (mL)
M = titrant molarity (mM/mL)
F = equivalency factor, 65.4 mg/mM
W = sample weight (mg)
Acceptance criteria: NLT 31.3% on the dried basis.