Modification of Multiwalled Carbon Nanotubes by Dipyridile Amine for Potentiometric Determination of Lead(II) Ions in Environmental Samples

Table 4

Recovery of determination of Pb(II) ions in certified reference materials.

Sample	Unit	Concentration		Added	Found	Recovery (%)
		Certified	Found
ERM-CA022 (drinking water)	μg L^−1	26 ± 0.9	24.9	—	—	95.8
CRM-SA-C (sandy soil)	mg kg^−1	133.0 ± 0.6	128.3	—	—	96.4
NIST 1572 (citrus leaves)	mg kg^−1	13.3 ± 2.4	13.1	—	—	98.4
Tap water	μg Kg^−1	ND	ND	20.0	19.9	99.7
Distilled water	μg Kg^−1	ND	ND	20.0	19.8	99.4
Sea water	μg Kg^−1	ND	ND	20.0	19.6	98.3
North soil	μg Kg^−1	47.1^a	46.2	20.0	63.7	96.2
South soil	μg Kg^−1	64.7^a	64.2	20.0	81.8	97.1
North leaves	μg Kg^−1	27.4^a	27.2	20.0	46.6	98.6
South leaves	μg Kg^−1	31.9^a	31.8	20.0	51.1	98.5

^aCertified by previously established method [1].