Quality

Reference material	Element	Certified value^a,b (mg/kg)	Obtained value^a (mg/kg)	Recovery (%)
SRM 1515 Apple Leaves	Mg	0.271 ± 0.008^c	0.281 ± 0.014	103.8
	Cu	5.64 ± 0.24	5.55 ± 0.65	98.4
	Ni	0.91 ± 0.12	0.88 ± 0.48	96.8
	Pb	0.470 ± 0.024	0.45 ± 0.032	95.7
	Zn	12.5 ± 0.3	12.4 ± 0.23	99.2
SRM 1573a Tomato Leaves	Cd	1.52 ± 0.04	1.43 ± 0.1	94.4
	Cr	1.99 ± 0.06	1.92 ± 0.09	96.6
	Co	0.57 ± 0.02	0.54 ± 0.07	94.1
	Fe	368 ± 7	375 ± 9	101.8

^aMean ± standard deviation
^bConfidence interval: 95%
^cConcentration in mass fraction (%)

Table 1: Quality control of the method.