分光光度法测定铬黑T解离常数实验设计

doi:10.3866/PKU.DXHX202112039

Abstract

Abstract:

This work aims to provide an approach to determine the dissociation constant (pK_a) of Eriochrome Black T by using UV-Visible spectrophotometry. The absorbance of Eriochrome Black T was measured at different pH and the data was fitted by ORIGIN with specific function model. Based on the obtained formula, the three pK_a of Eriochrome Black T can be calculated, respectively. This method is highly efficient, accurate, and easy to operate. It can also serve as an expansion for the undergraduates' chemistry laboratory, which can help cultivate the students' comprehensive ability of experimental design, data processing, and model derivation.

Key words: Dissociation constant, Ultraviolet-visible spectrophotometry, Eriochrome Black T

Ruiqing Sun, Ziting Xu, Zhuling Chen, Jiali Lin. Experimental Design on the Determination of Dissociation Constants of Eriochrome Black T by Spectrophotometry[J].University Chemistry, 2022, 37(12): 2112039.

Figures/Tables 14

References 16

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样品编号	pH	样品编号	pH	样品编号	pH
1	2.09	11	5.75	21	10.84
2	2.82	12	5.98	22	11.26
3	3.18	13	6.25	23	11.58
4	3.55	14	6.74	24	11.76
5	3.90	15	7.02	25	11.98
6	4.22	16	7.85	26	12.27
7	4.50	17	8.63	27	12.58
8	4.77	18	8.97	28	12.81
9	4.98	19	10.06	29	12.98
10	5.54	20	10.42

样品编号	pH	A(λ_{618 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $	样品编号	pH	A(λ_{618 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $	样品编号	pH	A(λ_{618 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $
1	2.09	0.103		11	5.75	0.193	?0.940	21	10.84	0.693	?0.470
2	2.82	0.104	?0.903	12	5.98	0.277	?0.570	22	11.26	0.602	?0.240
3	3.18	0.105	?0.540	13	6.25	0.37	?0.310	23	11.58	0.494	0.004
4	3.55	0.106	?0.300	14	6.74	0.622	0.275	24	11.76	0.39	0.238
5	3.90	0.107	?0.100	15	7.02	0.783	0.785	25	11.98	0.301	0.465
6	4.22	0.108	0.097	16	7.85	0.89	2.414	26	12.27	0.195	0.856
7	4.50	0.11	0.544	17	8.63	0.893		27	12.58	0.153	1.131
8	4.77	0.112		18	8.97	0.894		28	12.81	0.134	1.327
9	4.98	0.112		19	10.06	0.853	?1.270	29	12.98	0.098
10	5.54	0.153	?1.260	20	10.42	0.79	?0.820

样品编号	pH	A(λ_{516 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $	样品编号	pH	A(λ_{516 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $
1	2.09	0.276		9	4.98	0.288
2	2.82	0.276		10	5.54	0.289	?1.890
3	3.18	0.277	?1.040	11	5.75	0.291	?1.400
4	3.55	0.28	?0.300	12	5.98	0.303	?0.630
5	3.90	0.282	0	13	6.25	0.316	?0.260
6	4.22	0.285	0.477	14	6.74	0.354	0.706
7	4.50	0.287	1.041	15	7.02	0.365	1.585
8	4.77	0.288		16	7.85	0.367

样品编号	pH	A(λ_{455 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $	样品编号	pH	A(λ_{455 nm})	$ \lg \left( {\frac{{{A_0} - {A_1}}}{{{A_1} - {A_2}}}} \right) $
16	7.85	0.254		23	11.58	0.375	?0.100
17	8.63	0.252		24	11.76	0.407	0.1
18	8.97	0.256	?1.840	25	11.98	0.447	0.371
19	10.06	0.275	?1.040	26	12.27	0.467	0.533
20	10.42	0.28	?0.950	27	12.58	0.493	0.814
21	10.84	0.294	?0.750	28	12.81	0.51	1.111
22	11.26	0.333	?0.390	29	12.98	0.53

波长	拟合方程	pK_a值	R² (可决系数)
516 nm	y = 0.661x + 3.85	pK_a1 = 3.85	0.979
618 nm	y = 1.24x + 3.94	pK_a1 = 3.94	0.966
516 nm	y = 0.441x + 6.35	pK_a2 = 6.35	0.987
618 nm	y = 0.644x + 6.41	pK_a2 = 6.41	0.982
455 nm	y = 1.29x + 11.57	pK_a3 = 11.57	0.980
618 nm	y = 1.07x + 11.43	pK_a3 = 11.43	0.989

Experimental Design on the Determination of Dissociation Constants of Eriochrome Black T by Spectrophotometry

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Figures/Tables 14

References 16

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文献值	测定平均值	相对偏差	样品数n	标准差S	F检验
文献值	测定平均值	相对偏差	样品数n	标准差S	F_表	F_计算
pK_a1 = 3.9	516 nm，pK_a1 = 3.85	?1.38%	5	0.0342	6.26	2.29
pK_a1 = 3.9	618 nm，pK_a1 = 3.94	1.13%	6	0.0518	6.26	2.29
pK_a2 = 6.4	516 nm，pK_a2 = 6.35	?0.78%	6	0.0272	4.95	2.29
pK_a2 = 6.4	618 nm，pK_a2 = 6.41	0.16%	7	0.0412	4.95	2.29
pK_a3 = 11.5	455 nm，pK_a3 = 11.57	0.61%	11	0.0511	3.14	2.79
pK_a3 = 11.5	618 nm，pK_a3 = 11.43	?0.61%	10	0.0306	3.14	2.79

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