Zinc sulfate heptahydrate

Tacrolimus was a gift from Astellas Pharma Inc. (Tokyo, Japan), and stable isotope-labeled Tacrolimus (Tac¹³C,D₂) was purchased from Toronto Research Chemicals Inc. (Toronto, ON, Canada). The reagents for chromatography are as follows: hyper LC/MS grade methanol and water, as well as zinc sulfate heptahydrate, were purchased from Merck Millipore (Darmstadt, Germany). Hyper LC/MS-grade acetonitrile, formic acid and HPLC-grade tert-butyl methyl ether were obtained from J.T. Baker (Deventer, the Netherlands), whereas ammonium acetate Optigrade was purchased LGC Standards (Wesel, Germany). Reagent-grade deionized water was produced using a Millipore SimPak1, Simplicity 185 (Millipore, France).

The standard-grade dehydroacetic acid, sorbic acid, benzoic acid, methylparaben, ethylparaben, tetra-n-butylammonium hydroxide and phosphoric acid were purchased from Sigma-Aldrich (St. Louis, MO, USA). Ethanol and acetonitrile for an extraction solvent, were obtained from Merck (Frankfurt, Germany). Ultrapure water (resistivity ≥ 18 MΩ) was obtained from a Milli-Q ultrapure water purification system (Millipore, Billerica, MA, USA). Potassium ferricyanide (Sigma-Aldrich, St. Louis, MO, USA) and zinc sulfate heptahydrate (Merck, Frankfurt, Germany) were used as the carrez solution I, carrez solution II. All regents used were analytical grade or better.

Stratification of the sample according to the oral zinc supplementation resulted in the formation of three groups: the control group (CG) received a placebo (10% sorbitol, the same vehicle used in the zinc solution); Group 1 (G1) received 5 mg-Zn/day; and Group 2 (G2) received 10 mg-Zn/day. The supplementation period was three months. Zinc was supplied in the form of zinc sulfate heptahydrate (ZnSO₄·7H₂O; Merck, Darmstadt, Germany). Each drop of the supplement contained 1 mg of the zinc element. zinc sulfate heptahydrate acquisition and the oral zinc solution preparation were performed as described by Brito et al. [19 (link)]. Those responsible for the children were instructed to add the supplement to water, milk or juice at breakfast.

Chemicals employed throughout the study were CH₃COONa (99%, Merck, India), CH₃COOH (99%, Merck, India), ninhydrin (99%, Merck, India), glycylleucine (99%, Loba Chemie, India) and zinc sulfate heptahydrate (99%, Merck, India). All of the above chemicals were used without any further surplus purification. For synthesizing gemini surfactants employed chemicals were 1,6-dibromohexane (>97%), 1,5-dibromopentane (>98%), 1,4-dibromobutane (>98%) and N,N-dimethylhexadecylamine (95.0%). These chemicals were purchased from Fluka, Germany. Other chemicals used in the current experiments were of AR grade. The specific conductivity of water employed during the whole study was (1–2) × 10⁻⁶ ohm⁻¹ cm⁻¹. Stock solutions of reactants and surfactants were prepared by dissolving requisite amounts in CH₃COONa-CH₃COOH buffer solution (pH 5.0). The buffer of pH 5.0 prepared by mixing of 30 cm³ of 200 mmol.kg⁻¹ CH₃COOH and 70 cm³ of 200 mmol.kg⁻¹ CH₃COONa⁴³ . The solutions were made freshly as per the necessities. To note the pH of the solutions, measurements were carried out on pH meter (ELICO LI-122, Hyderabad, India). In respect to achieving the composition of reaction products produced on the title reaction, Job’s method was applied in gemini surfactant media. It was identified that both the reactants (each mole of ninhydrin and [Zn(II)-Gly-Leu]⁺) associated to form the product.

The EG was supplemented with 10 mg Zn per day for 3 months in the form of zinc sulfate heptahydrate (ZnSO₄·7H₂O; Merck, Darmstadt, Germany). Oral zinc solution (152.97 µmol Zn/day) was prepared at the Pharmacotechnical Laboratory of the Department of Pharmacy, UFRN. Each drop contained 1 mg of elemental zinc. The CG received an oral placebo as sorbitol 10%. These solutions were added to milk or juice every morning at breakfast. Zinc supplementation was monitored every 2 weeks during home visits by the same observer.