2.2. Reagents
Deionized water was used to prepare all solutions. All the glassware
was kept overnight in a 5% (v/v) nitric acid solution. All the reagents used
were of analytical grade.Working solutions of Mn at μg L−1 levels were
prepared daily by diluting a 1000 μg L−1 metal stock solution purchased
from Merck (Darmstadt, Germany). Hydrochloric acid solutions were
prepared by direct dilution of the concentrated solution (Merck) with
deionized water. Acetate (pH 4.0–6.0), borate (pH 7.0–8.5) and
ammonia (pH 9.0–10.0) buffer solutions [21] were used to adjust the
pH of solutions of manganese. Solutions of the Me-BTABr reagent were
prepared by dissolving appropriate amounts of the laboratory-prepared
dye [22] in absolute ethanol (Merck). Solutions of Triton X-114 were
prepared by dissolving the surfactant in deionized water. Solutionscontaining various ratios of surfactant and reagent Me-BTABr were
prepared and used in the system. For accuracy studies, two certified
reference materials were analyzed: apple leaves NIST 1515 and spinach
leaves NIST 1570a.