Table 3.

Combined standard uncertainties arising from the equipment (volumetric flasks and pipettes) used in the preparation of the solution, that is digestion and dilution, calculated using the rule of the root sum of the squares [28] from the standard uncertainties of fixed volume certified Eppendorf Research Plus® pipettes [29] as well as uncertainties of batch-certified DURAN® volumetric flasks

			Volumetric flask
			5 mL	25 mL	50 mL
			0.2% ± 0.010 mL	0.06% ± 0.015 mL	0.04% ± 0.020 mL
Pipette	10 μL	0.55% ± 0.055 μL	0.57% 500 ± 2.8	0.53% 2500 ± 13	0.53% 5000 ± 26
	20 μL	0.17% ± 0.034 μL	0.26% 250 ± 0.66	0.18% 1250 ± 2.3	0.17% 2500 ± 4.4