Magnesium 2 chloride hexahydrate

All reagents were analytical grade. Ultrapure water (18.2 MΩ·cm) from a Mill-Q system (Merck Millipore, Darmstadt, Germany) was used throughout. Laboratory containers were rinsed with H₂O prior to use. Standard solutions of all metals (lead(II) nitrate, cadmium(II) nitrate tetrahydrate, potassium dichromate(VI), iron(III) chloride hexahydrate, nickel(II) sulfate hexahydrate, copper(II) sulfate pentahydrate, manganese(II) chloride tetrahydrate, magnesium(II) chloride hexahydrate, iron(II) sulfate heptahydrate, aluminum(III) sulfate hydrate, barium(II) chloride, vanadium(III) chloride, and cobalt(II) sulfate pentahydrate) were purchased from Sigma-Aldrich (St. Louis, MO, USA). L-ascorbic acid (97%), L-cysteine, Tris base (99.9%), bathophenanthroline (97%), dimethylglyoxime (99%), dithiooxamide (98.5%), and sodium fluoride were purchased from Sigma-Aldrich. Sodium acetate, ammonium acetate, hydrochloric acid, sodium hydroxide, and glacial acetic acid were obtained from Fisher Scientific (Pittsburgh, PA, USA). Whatman (grade 1) filter paper was purchased from Apollo Presentation Products (Booneville, MS, USA).