Table 3. Ni²⁺ Contents and Its Recoveries of the Water Samples Using the GQD–DMG.

		proposed method		ICP–OES
sample	spiked (μg L–1)	found (μg L–1) ± (SD, n = 3)	recovery (%)	found (μg L–1) ± (SD, n = 3)	recovery (%)
drinking water 1		n.d.a		n.d.
	125	110.52	88	115.38	92
	200	182.05	91	176.44	88
	500b	516.03	103	520.03	104
drinking water 2		n.d.		n.d.
	125	125.35	100	118.22	95
	200	194.76	97	190.46	95
	500b	508.82	102	517.43	103
drinking water 3		n.d.		n.d.
	125	120.01	96	118.09	94
	200	209.56	105	215.88	108
	500b	505.86	101	514.65	103
drinking water 4		n.d.		n.d.
	125	106.64	85	100.44	80
	200	185.24	93	180.52	90
	500b	480.17	96	485.38	97
drinking water 5		n.d.		n.d.
	125	115.41	92	118.44	95
	200	215.93	108	208.87	104
	500b	510.59	102	504.38	101
tap water 1		n.d.		n.d.
	125	135.56	108	130.3	104
	200	213.91	107	206.45	103
	500b	510.68	102	515.55	103
tap water 2		n.d.		n.d.
	125	129.92	104	121.32	97
	200	210.34	105	202.45	101
	500b	515.4	103	512.34	102

^an.d. = not detectable.

^bDiluted 5-fold.