All chemical reagents are trace-metal grade. The tracemetal
grade, concentrated nitric acid, and 30% H2O2 that
were used for the digestion of samples and for matrixmatching
of calibration and quality control standards
were purchased from Fisher Scientific (Pittsburg, PA,
USA).
Deionized water (17.8 MΩ cm) was used for the
dilution of samples and standards and was provided by
a Nanopure Infinity ultrapure water system