Determination of Metals in Natural Waters by Inductively Coupled Plasma Optical Emission Spectroscopy after Preconcentration on Silica Sequentially Coated with Layers of Polyhexamethylene Guanidinium and Sulphonated Nitrosonaphthols

Table 3

Desorption degree of reagents NRS, NKS, and NNS from the surface of SiO₂-PHMG by washing with 10 mL of HNO₃ or HCl solutions (mass of adsorbents 0.1 g, reagents content 40 µMg⁻¹, n = 5, P=0.95).

, M	, %
	HNO3			HCl
	NRS	NKS	NNS	NRS	NKS	NNS
0.001	0.2	0.2	10	0.4	0.5	6.5
0.01	11	10	50	20	20	45
0.1	30	29	71	46	45	77
1	77	77	81	84	84	86
6	88	90	90	88	88	90
	98	98	97	96	98	97

–desorption with two volumes of hot (50°С) 6 М acid