Table 5.

Results of analysis of standard reference materials (SRM) in comparison with certified values.

Standard reference material	Analysed SRM value	Certified SRM value	Recovery%
Sequential extraction
SRM-027-050-Soil (n = 3)
Step 1
As	4.19 ± 0.40	4.98.0 ± 0.38	88
Cr	3.13 ± 0.10	2.87 ± 0.13	85
Zn	4.08 ± 0.79	3.94 ± 0.39	100
Cu	34.24 ± 1.6	46.73 ± 1.8	69
Pb	73.11 ± 2.00	64.20 ± 2.00	101
Sn	178 ± 5.00	195 ± 2.00	103
Step 2
As	3.08 ± 0.30	3.12 ± 0.34	90
Cr	2.89 ± 0.14	2.98 ± 0.19	85
Zn	100.18 ± 4.00	88.84 ± 3.00	92
Cu	102.38 ± 2.0	129.0 ± 2.5	101
Pb	62.30 ± 3.00	65.28 ± 3.00	99
Sn	112 ± 4.00	136 ± 5.00	100
Step  3
As	1.18 ± 0.23	1.02 ± 0.32	95
Cr	100.12 ± 4.00	105.00 ± 5.00	106
Zn	52.28 ± 2.00	65.74 ± 3.00	103
Cu	29.28 ± 2.0	36.32 ± 2.5	100
Pb	10.10 ± 2.00	8.80 ± 3.00	102
Sn	70 ± 2.00	72 ± 3.00	100
Step 4
As	0.18 ± 0.03	0.20 ± 0.52	120
Cr	73.33 ± 5.00	60.56 ± 4.00	128
Zn	98.00 ± 5.00	87.34 ± 4.00	120
Cu	20.98 ± 0.88	19.93 ± 2.00	115
Pb	14.23 ± 0.90	10.53 ± 1.00	104
Sn	40 ± 4.00	35 ± 2.00	111
Total digestion
CRM-027-050-Soil (n = 3)
As	9.86 ± 1.00	10.78 ± 1.00	97
Cr	157.95 ± 4.00	180.45 ± 4.00	108
Zn	251.16 ± 4.00	250.06 ± 5.00	99
Cu	198.18 ± 4.00	235.75 ± 3.00	112
Pb	143.91 ± 2.00	155.31 ± 2.00	94
Sn	390 ± 5.00	381 ± 4.00	99