Table 2. The Contents and Their Recoveries of CN^– and [Fe(CN)₆]^3– in Water Samples Using the Hg²⁺-GQD System (n = 3).

	CN–			[Fe(CN)6]3–
water sample	added (μM)	found (μM)	recovery (%) ± SD	added (μM)	found (μM)	recovery (%) ± SD
drinking water brand 1	5.0	4.29	85.89 ± 0.32	5.0	5.10	102.09 ± 2.52
	50.0	47.32	94.64 ± 0.47	50.0	50.33	100.65 ± 1.64
	100.0	95.52	95.52 ± 0.64	250.0	248.35	99.34 ± 2.18
drinking water brand 2	5.0	4.83	96.64 ± 0.96	5.0	5.20	104.08 ± 3.11
	50.0	53.18	106.36 ± 1.09	50.0	50.89	101.78 ± 2.32
	100.0	112.66	112.66 ± 2.0	250.0	245.18	98.07 ± 0.84
drinking water brand 3	5.0	4.62	92.42 ± 2.38	5.0	4.32	86.33 ± 2.47
	50.0	52.34	104.68 ± 1.22	50.0	44.52	89.04 ± 2.32
	100.0	106.36	106.36 ± 0.95	250.0	232.07	92.83 ± 1.46
drinking water brand 4	5.0	4.73	94.89 ± 1.19	5.0	5.44	108.72 ± 2.34
	50.0	51.12	102.23 ± 2.48	50.0	55.23	110.46 ± 1.43
	100.0	104.42	104.42 ± 2.14	250.0	258.15	103.26 ± 1.66
drinking water brand 5	5.0	4.78	95.67 ± 1.21	5.0	4.31	86.27 ± 2.42
	50.0	52.21	104.42 ± 2.11	50.0	42.44	84.88 ± 1.37
	100.0	101.43	101.43 ± 1.22	250.0	225.92	90.37 ± 2.06
tap water 1	5.0	4.42	88.49 ± 2.37	5.0	4.71	94.21 ± 6.72
	50.0	52.45	104.90 ± 1.76	50.0	50.36	100.71 ± 1.74
	100.0	109.86	109.86 ± 2.55	250.0	242.20	96.88 ± 1.35
tap water 2	5.0	4.98	99.64 ± 2.54	5.0	5.37	107.34 ± 2.56
	50.0	52.12	104.32 ± 2.51	50.0	55.36	110.72 ± 2.34
	100.0	110.02	110.02 ± 2.49	250.0	264.95	105.98 ± 2.11
tap water 3	5.0	4.75	94.97 ± 2.14	5.0	5.70	113.92 ± 6.38
	50.0	51.82	103.63 ± 1.27	50.0	55.17	110.34 ± 2.49
	100.0	107.48	107.48 ± 1.30	250.0	269.20	107.68 ± 2.85