分光光度法和导数分光光度法测Cr和Co含量

'两组分混合物的同时测定——分光光度法和导数分光光度法测Cr和Co含量huangsir一、实验目的1.掌握分光光度法两组分同时测定的方法;2.学习导数光谱的绘制;3.掌握导数分光光度法同时测定两组分的方法特点huangsir二、实验原理（1）分光光度法同时测定两组分混合物：当体系中有几个组分时，根据吸光度的加和性，体系总吸光度为各组分吸光度之和：nnA总=∑∑AbCi=εii（1）ii=11=式中：A总为各组分吸光度Ai之和；ci和εi分别为i组分的浓度和摩尔吸收系数。各组分的吸收光谱既是部分重叠，只要服从吸收定律，就可根据上式测定混合物中各组分的含量。最简单的例子时两组分混合物的测定。例如,在试样中含有两个组分x和y，其浓度分别为cx和cy,在波长λ1和λ2下，测得总吸光度Aλ和Aλ。根据式（1），可以得出以下方程组：12xy+xyAcc=εε+λλλ111xyxy+xyAcc=εε+λλλ222xy式中，ε和ε为x,y在波长为λ和λ时，组分x和y的摩尔吸收系数，可用已知浓度λ1λ212的纯组分溶液获得，即分别配制x和y的系列标准溶液，在λ和λ波长下测量x和y系列标准12的吸光度，并绘制标准曲线，两标准曲线的斜率极为x和y在λ和λ处的摩尔吸光系数，代12入解方程组，可求得cx和cy。用这种方法，原则上可以同时测定多组分混合物中各组分的含 量，但组分增多，误差增大。（2）导数分光光度法同时测定两组分混合物：现代的紫外-可见分光光度计一般都能对吸收光谱进行微分处理，获得导数光谱。利用导数光谱进行分光光度测定，称为导数分光光度法。这样的分光光度计，一般可以获得1～4阶导数光谱。在各阶导数光谱中，吸光度对波长的微分值与溶液中组分的浓度仍保持线性关系：nndAdε=bCnnddλλ式中，c为组分的浓度；n为导数的阶数。因此可以利用导数光谱进行定量测定。由于导数光谱灵敏度高，对于试样纯度检验，多组分混合物的测定，消除共存杂质的干扰与背景吸收，测定浑浊试样都具有特殊的优越性。huangsir图1两组分吸收光谱（I：吸收光谱不重叠；II：二组分吸收光谱重叠）导数光谱数值的测定方法有切线法、峰高法和峰零法，即量取两个极值之间的距离。如下图所示：P：峰高法t：切线法z：峰零法2 图2导数光谱数值的测定方法本实验分别用分光光度法和导数分光光度法测定huangsirCr和Co混合物的浓度。三、主要仪器和试剂仪器：GBC-cintra10e分光光度计；容量瓶：25mL18个；试剂：Co(NO3)2标准溶液0.350mol/L;Cr(NO3)3标准溶液0.100mol/L;Co和Cr混合试样。四、实验步骤(1)分光光度法同时测定两组分混合物组成：配制标准系列溶液：在4个25mL容量瓶中，分别加入2.50,5.00,7.5,10.00mL的Co(NO3)2标准溶液。另取4各25mL容量瓶，分别加入2.50,5.00,7.5,10.00mL的Cr(NO3)3标准溶液。分别用去离子水稀释至刻度，摇匀。2+3+绘制Co和Cr标准溶液的吸收光谱：用1cm吸收池，以去离子水做参比溶液，在可见2+3+光区分别绘制Co和Cr溶液的吸收光谱，并由曲线上找出λ和λ。12标准曲线的绘制：以蒸馏水为参比，在λ1和λ2分别测定配制的Co(NO3)2和Cr(NO3)3系列标准溶液的吸光度，并分别绘制二者的标准曲线。混合试样吸收光谱：用1cm吸收池，以去离子水作参比溶液，绘制混合试样的吸收光谱，读出试液在波长λ和λ处的吸光度A和A。12λ1λ23 （2）导数分光光度法测定两组分混合物：绘制Co和Cr标准溶液的导数光谱：以去离子水作参比溶液，分别绘制标准溶液1～4阶导数光谱。选择适当阶数的导数光谱作为定量分析的依据。绘制混合试样的导数光谱：在上述条件下，绘制混合试样的1～4阶导数光谱。注意事项：（1）在分光光度法同时测定两组分混合物时，根据吸收光谱决定最大吸收峰的λ和λ；12（2）导数光谱的条件确定后，在测定过程中不能随意变动。五、数据处理1、原始数据（见附录huangsir）2、实验条件实验条件狭缝宽度光度测定形式扫描速度扫描范围强度倍数全波段扫描1.5nm吸光值1000nm/min350nm-800nm1固定波长扫描1.5nm吸光值1000nm/min453,511,542,575nm13、数据计算I分光光度法(1)固定波长的选定CrCo0.7Co0.6Cr0.50.4Cr0.30.20.10.0300400500600700800wavelength4 在设定实验条件下，分别对配制好的相同浓度的两个标准液进行全波段扫描，将两个扫描谱图做重合处理，选出两交叉点（453nm,542nm）和另外两点(511nm,575nm)作为固定波长。(2)绘制标准曲线①用作图软件origin8.0画四个测量值的标准曲线表1Cr-a-575nm0.010.020.030.04A10.13300.26690.40340.5467A20.13300.26700.40370.5469A30.13320.26710.40380.5469A0.13310.26700.40360.5468AhuangsirLinearFitofA0.60.50.4A0.30.20.10.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99965ValueStandardErrorAIntercept-0.00680.0041ASlope13.7770.14961即斜率k=13.777，一元线性相关系数r=0.999655 表2Cr-a-542nm0.010.020.030.04A10.09950.20170.30580.4155A20.09950.20170.30600.4155A30.09950.20170.30610.4157A0.09950.20170.30600.4156ALinearFitofA0.450.40huangsir0.350.300.25A0.200.150.100.050.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99962ValueStandardErrorAIntercept-0.007450.00326ASlope10.5260.11917即斜率k=10.526，一元线性相关系数r=0.999626 表3Cr-a-511nm0.010.020.030.04A10.05250.10610.16010.2178A20.05270.10610.16040.2180A30.05290.10610.16050.2182A0.05270.10610.16030.2180ALinearFitofA0.240.220.20huangsir0.180.160.14A0.120.100.080.060.040.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99951ValueStandardErrorAIntercept-0.003250.00193ASlope5.5010.07062即斜率k=5.501，一元线性相关系数r=0.999517 表4Cr-a-453nm0.010.020.030.04A10.08050.14460.20880.2766A20.08080.14540.20990.2780A30.08110.14570.21060.2793A0.08080.14520.20980.2780ALinearFitofA0.30huangsir0.250.20A0.150.100.050.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99971ValueStandardErrorAIntercept0.01440.00177ASlope6.5620.06471即斜率k=6.562，一元线性相关系数r=0.999718 表5Co-a-575nm0.0350.070.1050.14A10.02040.04640.07060.0963A20.02120.04660.07090.0963A30.02090.04670.07090.0967A0.02080.04660.07080.09640.100.090.08huangsir0.070.06A0.050.040.030.020.010.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.99978ValueStandardErrorAIntercept-0.00415.87E-04ASlope0.717140.00613即斜率k=0.71714，一元线性相关系数r=0.999789 表6Co-a-542nm0.0350.070.1050.14A10.09760.20090.30390.4103A20.09830.20130.30490.4112A30.09810.20190.30540.4122A0.09800.20140.30470.41120.450.400.35huangsir0.300.25A0.200.150.100.050.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.99992ValueStandardErrorAIntercept-0.00690.00149ASlope2.979710.01551即斜率k=2.97971，一元线性相关系数r=0.9999210 表7Co-a-511nm0.0350.070.1050.14A10.16530.33670.50820.6857A20.16560.33680.50880.6860A30.16570.33720.50890.6863A0.16550.33690.50860.6860ALinearFitofA0.70.6huangsir0.5A0.40.30.20.10.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.9999ValueStandardErrorAIntercept-0.009050.0028ASlope4.9520.02922即斜率k=4.952，一元线性相关系数r=0.999911 表8Co-a-453nm0.0350.070.1050.14A10.07960.16520.24950.3373A20.07990.16550.25010.3375A30.08000.16560.25010.3376A0.07980.16540.24990.3375ALinearFitofA0.35huangsir0.300.25A0.200.150.100.050.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.99992ValueStandardErrorAIntercept-0.006250.00119ASlope2.450290.01239即斜率k=2.45029，一元线性相关系数r=0.9999212 表9Cr-b-575nm0.010.020.030.04A10.13100.26990.40820.5523A20.13140.27010.40860.5529A30.13150.27030.40880.5537A0.13130.27010.40850.5530ALinearFitofA0.6huangsir0.50.4A0.30.20.10.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99984ValueStandardErrorAIntercept-0.010150.00277ASlope14.0350.10117即斜率k=14.035，一元线性相关系数r=0.9998413 表10Cr-b-542nm0.010.020.030.04A10.09910.20510.31050.4216A20.09940.20500.31070.4222A30.09930.20530.31090.4227A0.09930.20510.31070.4222ALinearFitofA0.450.40huangsir0.350.300.25A0.200.150.100.050.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99974ValueStandardErrorAIntercept-0.009250.00274ASlope10.7430.09991即斜率k=10.743，一元线性相关系数r=0.9997414 表11Cr-b-511nm0.010.020.030.04A10.05380.10970.16440.2249A20.05410.10980.16470.2268A30.05400.11000.16490.2255A0.05400.10980.16470.2257ALinearFitofA0.240.22huangsir0.200.180.160.14A0.120.100.080.060.040.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99915ValueStandardErrorAIntercept-0.003950.00263ASlope5.70.09597即斜率k=5.7，一元线性相关系数r=0.9991515 表12Cr-b-453nm0.010.020.030.04A10.07990.14800.21270.2853A20.08060.14870.21380.2862A30.08120.14910.21400.2872A0.08060.14860.21350.2862ALinearFitofA0.30huangsir0.250.20A0.150.100.050.0100.0150.0200.0250.0300.0350.040c(mol/L)Equationy=a+b*xAdj.R-Square0.99926ValueStandardErrorAIntercept0.01180.00293ASlope6.8170.10707即斜率k=6.817，一元线性相关系数r=0.9992616 表13Co-b-575nm0.0350.070.1050.14A10.02940.05080.07710.0993A20.02960.05100.07770.1005A30.02870.05120.07810.1004A0.02920.05100.07760.1001ALinearFitofA0.110.100.09huangsir0.080.07A0.060.050.040.030.020.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.99786ValueStandardErrorAIntercept0.004650.00175ASlope0.683710.01826即斜率k=0.68371，一元线性相关系数r=0.9978617 表14Co-b-542nm0.0350.070.1050.14A10.10670.20610.31140.4109A20.10700.20640.31200.4126A30.10730.20680.31280.4134A0.10700.20640.31210.4123ALinearFitofA0.450.40huangsir0.350.30A0.250.200.150.100.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.9998ValueStandardErrorAIntercept0.004050.00231ASlope2.918860.02411即斜率k=2.91886，一元线性相关系数r=0.999818 表15Co-b-511nm0.0350.070.1050.14A10.17480.34210.51710.6850A20.17490.34210.51750.6858A30.17500.34270.51790.6863A0.17490.34230.51750.6857ALinearFitofA0.7huangsir0.60.5A0.40.30.20.10.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.99989ValueStandardErrorAIntercept0.00320.00289ASlope4.878860.03012即斜率k=4.87886，一元线性相关系数r=0.9998919 表16Co-b-453nm0.0350.070.1050.14A10.09040.17060.25880.3400A20.09080.17070.25900.3403A30.09080.17080.25920.3405A0.09070.17070.2590.3403ALinearFitofA0.35huangsir0.300.25A0.200.150.100.050.020.040.060.080.100.120.14c(mol/L)Equationy=a+b*xAdj.R-Square0.99948ValueStandardErrorAIntercept0.00590.00302ASlope2.391710.03146即斜率k=2.39171，一元线性相关系数r=0.9994820 ②由A=εbc可知，理论上标准曲线应过原点，引入原点分析（即5个点）：表17Cr-A标准液（引入原点）吸收度A浓度(mol/L)575nm542nm511nm453nm0.000.00000.00000.00000.00000.010.13310.09950.05270.08080.020.26700.20170.10610.14520.030.40360.30600.16030.20980.040.54680.41560.21800.2780AALinearFitofBLinearFitofC0.60.40.5huangsir0.30.40.20.3AA0.20.10.10.00.00.000.010.020.030.040.000.010.020.030.04c(mol/L)c(mol/L)λ=575nmEquationy=a+b*xAdj.R-Square0.99971ValueStandardErrorBIntercept-0.002720.00286BSlope13.6410.11673即斜率k=13.641，一元线性相关系数r=0.99971λ=542nmEquationy=a+b*xAdj.R-Square0.99955ValueStandardErrorCIntercept-0.002980.0027CSlope10.3770.11016即斜率k=10.377，一元线性相关系数r=0.9995521 AALinearFitofDLinearFitofE0.250.300.200.250.150.200.15A0.10A0.100.050.050.000.000.000.01huangsir0.020.030.040.000.010.020.030.04c(mol/L)c(mol/L)λ=511nmEquationy=a+b*xAdj.R-Square0.99958ValueStandardErrorDIntercept-0.00130.00136DSlope5.4360.05541即斜率k=4.90029，一元线性相关系数r=0.9998λ=453nmEquationy=a+b*xAdj.R-Square0.99753ValueStandardErrorEIntercept0.005760.00417ESlope6.850.17042即斜率k=6.85，一元线性相关系数r=0.9975322 表18Co-A标准液（引入原点）吸收度A浓度(mol/L)575nm542nm511nm453nm0.0000.00000.00000.00000.00000.0350.02080.09800.16550.07980.0700.04660.20140.33690.16540.1050.07080.30470.50860.24990.1400.09640.41120.68600.3375ALinearFitofBALinearFitofC0.100.40.080.30.06huangsirA0.2A0.040.10.020.000.0-0.020.000.020.040.060.080.100.120.140.16-0.020.000.020.040.060.080.100.120.140.16c(mol/L)c(mol/L)λ=575nmEquationy=a+b*xAdj.R-Square0.99838ValueStandardErrorBB-0.001640.0012BB0.693710.01398即斜率k=0.69371，一元线性相关系数r=0.99838λ=542nmEquationy=a+b*xAdj.R-Square0.99972ValueStandardErrorCIntercept-0.002760.0021CSlope2.940290.02446即斜率k=2.94029，一元线性相关系数r=0.9997223 AALinearFitofDLinearFitofE0.70.350.60.300.50.250.40.20A0.3A0.150.20.100.10.050.00.00-0.1huangsir-0.05-0.020.000.020.040.060.080.100.120.140.16-0.020.000.020.040.060.080.100.120.140.16c(mol/L)c(mol/L)λ=511nmEquationy=a+b*xAdj.R-Square0.9998ValueStandardErrorDIntercept-0.003620.00294DSlope4.900290.03429即斜率k=4.90029，一元线性相关系数r=0.9998λ=453nmEquationy=a+b*xAdj.R-Square0.99967ValueStandardErrorEIntercept-0.00250.00187ESlope2.414570.02183即斜率k=2.41457，一元线性相关系数r=0.9996724 表19Cr-B标准液（引入原点）吸收度A浓度(mol/L)575nm542nm511nm453nm0.000.00000.00000.00000.00000.010.13130.09930.05400.08060.020.27010.20510.10980.14860.030.40850.31070.16470.21350.040.55300.42220.22570.2862AALinearFitofBLinearFitofC0.50.60.40.50.4huangsir0.30.3AA0.20.20.10.10.00.00.000.010.020.030.040.000.010.020.030.04c(mol/L)c(mol/L)λ=575nmEquationy=a+b*xAdj.R-Square0.99964ValueStandardErrorBIntercept-0.004060.00321BSlope13.8320.13095即斜率k=13.832，一元线性相关系数r=0.99964λ=542nmEquationy=a+b*xAdj.R-Square0.99947ValueStandardErrorCIntercept-0.00370.00297CSlope10.5580.12139即斜率k=10.558，一元线性相关系数r=0.9994725 ALinearFitofD0.250.300.200.250.150.200.15A0.10A0.100.050.050.000.00huangsir0.000.010.020.030.040.000.010.020.030.04c(mol/L)c(mol/L)λ=511nmEquationy=a+b*xAdj.R-Square0.99935ValueStandardErrorDIntercept-0.001580.00176DSlope5.6210.07177即斜率k=5.621，一元线性相关系数r=0.99935λ=453nmEquationy=a+b*xAdj.R-Square0.9982ValueStandardErrorEIntercept0.004720.00366ESlope7.0530.14962即斜率k=7.053，一元线性相关系数r=0.998226 表20Co-B标准液（引入原点）吸收度A浓度(mol/L)575nm542nm511nm453nm0.0000.00000.00000.00000.00000.0350.02920.10700.17490.09070.0700.05100.20640.34230.17070.1050.07760.31210.51750.25900.1400.10010.41230.68570.3403ALinearFitofBALinearFitofC0.100.40.08huangsir0.30.06A0.2A0.040.10.020.000.0-0.020.000.020.040.060.080.100.120.140.16-0.020.000.020.040.060.080.100.120.140.16c(mol/L)c(mol/L)λ=575nmEquationy=a+b*xAdj.R-Square0.99726ValueStandardErrorBIntercept0.001860.0016BSlope0.710290.01861即斜率k=0.71029，一元线性相关系数r=0.99726λ=542nmEquationy=a+b*xAdj.R-Square0.99983ValueStandardErrorCIntercept0.001620.00165CSlope2.9420.0193即斜率k=2.942，一元线性相关系数r=0.9998327 AALinearFitofDLinearFitofE0.70.350.60.300.50.250.40.20A0.3A0.150.20.100.10.050.00.00-0.1huangsir-0.05-0.020.000.020.040.060.080.100.120.140.16-0.020.000.020.040.060.080.100.120.140.16c(mol/L)c(mol/L)λ=511nmEquationy=a+b*xAdj.R-Square0.99993ValueStandardErrorDIntercept0.001280.00174DSlope4.897140.02034即斜率k=4.89714，一元线性相关系数r=0.99993λ=453nmEquationy=a+b*xAdj.R-Square0.99952ValueStandardErrorEIntercept0.002360.00228ESlope2.425430.02662即斜率k=2.42543，一元线性相关系数r=0.9995228 ③原4个测量值与引入原点后（即5个点）的线性比较：表21线性相关系数比较575nm542nm511nm453nmCr-A0.999710.999510.999620.99965Cr-A(引入原点)0.999710.999550.999580.99753Co-A0.999920.999780.99990.99992Co-A(引入原点)0.998380.999720.99980.99967Cr-B0.999260.999150.999740.99984Cr-B(引入原点)0.999640.999470.999350.9982Co-B0.999480.99980.999890.99786Co-B(引入原点)0.997260.999830.999930.99952比较结果：引入原点后，大多数标准曲线的线性相关系数反而降低了。造成此结果可能是存在较大的系统误差，所得标准曲线不会过原点，故引入原点反而降低huangsir了相关系数。故，本实验处理数据时直接用4个测得值，不用引入原点。(3)摩尔吸收系数：整理以上数据，列出两种离子在不同波长的摩尔吸光系数如下：表22铬离子和钴离子在不同波长的摩尔吸收系数A组575nm542nm511nm453nmCr-A13.77710.5265.5016.562Co-A0.717142.979714.9522.45029B组575nm542nm511nm453nmCr-B14.03510.7435.76.817Co-B0.683712.918864.878862.39171(4)混合样品组分浓度计算实验测得未知混合样品数据如下：29 表23混合样品紫外吸收(稀释5倍)混合样品-A吸收值波长/nm575542511453A10.15790.20210.22480.1625A20.15810.20220.22220.1623A30.15800.20240.22270.1616A0.15800.20220.22320.1621混合样品-B吸收值波长/nm575542511453A10.16470.20990.23080.1681A20.16550.21040.23110.1693A30.16540.21080.23150.1692A0.16520.21040.23110.1689根据方程：huangsirxy+xyAcc=εε+λλλ111xyxy+xyAcc=εε+λλλ222xy计算结果如下表：表24混合样品组分浓度计算结果浓度混合样品A混合样品B波长Cr浓度（mol/L）Co浓度（mol/L）Cr浓度（mol/L）Co浓度（mol/L）λ=575nm,542nm0.009720.033510.010060.03504λ=575nm,511nm0.009680.034320.010030.03564λ=575nm,453nm0.009320.041190.009670.04305λ=542nm,511nm0.009410.034620.009840.03587λ=542nm,453nm0.001990.060830.001760.06559λ=511nm,453nm0.013450.030130.013820.03122结果分析：从计算结果看，λ=575nm,453nm，λ=542nm,453nm和λ=511nm,453nm时的三组数据明显属于异常值，按照分析化学异常数据取舍原则应与舍掉。整理计算平均浓度结果如下：表25混合样品组分平均浓度混合样品A混合样品BCrCoCrCo0.009720.033510.010060.03504浓度（mol/L）0.009680.034320.010030.035640.009410.034620.009840.03587平均浓度（mol/L）0.00960.034150.009980.03552相对平均偏差1.36%1.21%0.90%0.89%相对标准偏差1.76%1.68%1.20%1.21%30 保留三小数点后三位：3+A组：[Cr]=0.010mol/L[Co]=0.034mol/L3+B组：[Cr]=0.010mol/L[Co]=0.036mol/L3+A、B平均值：[Cr]=0.010mol/L[Co]=0.035mol/L测试样品被稀释5倍，故混合样品的浓度为：3+[Cr]=0.050mol/L[Co]=0.1725mol/LⅡ导数分光光度法我们用分光光度计对各样品的谱图进行微分处理，获得1阶导数光谱，并以峰零法对个样品进行定量分析计算。huangsir(1)峰零法取值的大致波段确定：BB0.0150.0200.0150.0100.0100.0050.0050.000AA0.000-0.005-0.005-0.010-0.010-0.015-0.015300400500600700800300400500600700800Co-A-4Cr-A-4上图是Cr离子标准液（右）和Co离子标准液（左）的一阶导数光谱谱图，从谱图中我们可看出，钴离子在波长为500nm左右位置都有明显的波峰，铬离子在350nm左右出现波峰。故，我们选取500nm左右作为钴离子的峰高参考位置和选取350nm左右作为铬离子的峰高参考位置。31 (2)标准溶液的一阶导数光谱图及相应标准曲线的绘制：使用origin8.0作图软件画导数一阶光谱并读出峰高值。①A组标准Cr溶液：BB0.0080.0040.0060.0030.0040.0020.0020.001AA0.0000.000-0.002-0.001-0.002huangsir-0.004-0.003-0.006300400500600700800300400500600700800BCr-A-1BCr-A-20.0200.0100.0150.0100.0050.005AA0.0000.000-0.005-0.005-0.010-0.015-0.010300400500600700800300400500600700800Cr-A-4Cr-A-332 表26导数分光光度法峰高值Cr-A浓度（mol/L）0.010.020.030.04波高值0.003650.0068170.0099480.013805BLinearFitofB0.0140.0120.010huangsirB0.0080.0060.0040.0020.0100.0150.0200.0250.0300.0350.040AEquationy=a+b*xAdj.R-Square0.99608ValueStandardErrorBIntercept1.56E-043.33E-04BSlope0.335960.01217即曲线斜率k=0.33596，截距为-0.000156，线性相关系数r=0.99608截距很小可忽略不计，则方程为：p=0.33596c33 ②A组标准Co溶液：B0.0100.0030.0020.0050.0010.0000.000AA-0.001-0.005-0.002huangsir-0.003-0.010-0.004300400500600700800300400500600700800λ/nmλ/nmCo-A-3Co-A-1BB0.0150.0060.0100.0040.0050.0020.0000.000AA-0.002-0.005-0.004-0.010-0.006-0.015-0.008300400500600700800300400500600700800λ/nmCo-A-4Co-A-234 表27导数分光光度法峰高值Co-A浓度（mol/L）0.0350.070.1050.14波高值0.0017140.0034820.0052170.007006BLinearFitofB0.0070.006huangsir0.005B0.0040.0030.0020.0010.020.040.060.080.100.120.14AEquationy=a+b*xAdj.R-Square0.99995ValueStandardErrorBIntercept-4.80E-051.91E-05BSlope0.050322.00E-04即曲线斜率k=0.05032，截距为-0.000048，线性相关系数r=0.99995截距很小可忽略不计，则方程为：p=0.05032c35 ③B组标准Cr溶液：BB0.0040.0080.0030.0060.0020.0040.0010.002AA0.0000.000-0.001huangsir-0.002-0.002-0.004-0.003-0.006300400500600700800300400500600700800Cr-B-1Cr-B-2BB0.0200.0100.0150.0100.0050.005A0.000A0.000-0.005-0.005-0.010-0.010-0.015300400500600700800300400500600700800Cr-B-3Cr-B-436 表28导数分光光度法峰高值Cr-B浓度（mol/L）0.010.020.030.04波高值-0.002621-0.005561-0.008547-0.011553BLinearFitofB0.0160.0140.0120.010huangsirB0.0080.0060.0040.0020.0100.0150.0200.0250.0300.0350.040AEquationy=a+b*xAdj.R-Square0.99983ValueStandardErrorBIntercept2.80E-047.23E-05BSlope0.347180.00264即曲线斜率k=0.34718，截距为-0.00028，线性相关系数r=0.99983截距很小可忽略不计，则方程为：p=0.34718c37 ④B组标准Co溶液：BB0.0030.0060.0020.0040.0010.0020.0000.000AA-0.001huangsir-0.002-0.002-0.004-0.003-0.006-0.004-0.008300400500600700800300400500600700800Co-B-1Co-B-2BB0.0100.0150.0100.0050.0050.0000.000AA-0.005-0.005-0.010-0.010-0.015300400500600700800300400500600700800Co-B-3Co-B-438 表29导数分光光度法峰高值Co-B浓度（mol/L）0.0350.070.1050.14波高值0.0017270.003470.0052510.007002BLinearFitofB0.0070.0060.005huangsirB0.0040.0030.0020.0010.020.040.060.080.100.120.14AEquationy=a+b*xAdj.R-Square0.99998ValueStandardErrorBIntercept-3.90E-051.36E-05BSlope0.05031.42E-04即曲线斜率k=0.0503，截距为-0.000039，线性相关系数r=0.99998截距很小可忽略不计，则方程为：p=0.0503c39 (3)未知混合液的组分浓度计算：导数分光光度法所得未知混合液的峰高值如下表：BB0.0040.0040.0030.0030.0020.0020.001BB0.0010.0000.000-0.001-0.001-0.002-0.002300400500huangsir600700800300400500600700800未知混合样品A未知混合样品B表30导数分光光度法峰高值未知混合样品A、BCr(350nm附近)Co(500nm附近)ABAB峰高值0.0034820.0035340.0022070.002267整理（2）中的方程：A组：Cr：p=0.33596cCo：p=0.05032cB组：Cr：p=0.34718cCo：p=0.0503c将表30中的数据代入计算得：AB平均值Cr0.010360.010180.01027Co0.043860.045070.044465测试液稀释5倍，故原未知液组分浓度为：[Cr]=0.051mol/L[Co]=0.222mol/L40 4、结果讨论3+分光光度法测得的结果为：[Cr]=0.050mol/L[Co]=0.1725mol/L分光导数法测得的结果为：[Cr]=0.051mol/L[Co]=0.222mol/L从两个不同方法的测量结果看，铬离子的浓度相差不大，但钴离子的浓度相差较大。应该是由于在500nm左右，钴离子和铬离子都有较强的吸收，故此处存在谱图重叠想象，而对此处作一阶导数处理不足以将重叠部分分开，故在此处用导数分光光度法测钴离子的浓度误差较大。对于导数分光光度法，波峰和波高位置的判断也会引起引起实验误差，从波长的范围来看，即使已经定位了两组分的共同的波长范围，单组分导数图像的最高点的位置和混合样的最高点的位置并不完全重合，有微小的波长范围差。六、注意事项huangsir1.比色皿每用完一次要冲洗干净，并用被测溶液润洗内壁3次2.比色皿使用时注意保护其透光面，拿取比色皿时注意不要用手指触碰透光面3.比色皿的一个透光面的上部标记有“7Q”的字样，确保每次改面朝向同一个方向，以消除比色皿的影响4.溶液配制尽量让同一个人完成，以消除中间的主观人为误差，提高准确度。5.实验过程中，仪器的参数设定后，在测定过程中不能随意改动。七、实验思考1、导数分光光度法中，两组分同时测定时，如何选择择定波长λ1，λ2？答：在可见-紫外的光谱范围，分别对于两个组分的标准试样进行扫描，将两个扫描结果吸光度图谱重叠比较，选出两个吸收峰线的交点或其旁边的点，要求使其对两个组分的吸光度都比较大。此两点对应的波长即为测定波长λ1，λ2。2、导数光谱条件（光谱带通、扫描速度、步长）的改变，对导数光谱是否产生影响？试加以说明。答：（1）光谱带通又称单色仪的光谱通带或带宽。指单色仪出射狭缝的辐射波长区间宽度。如出射狭缝为S(mm)，单色仪的倒线色散率为D(nm/mm)，则光谱通带Δλ=D×S(nm)。由狭缝射出后投射到被测物质上的光，是一个有限宽度的谱带——光谱通带。随光谱通带宽度的增大，吸收光谱的分辨率降低，并偏离朗伯一比尔定律。41 （2）一旦狭缝确定下来，扫描速度的快慢影响了图谱分辨率的高低；（3）狭缝设定的越窄，图谱分辨率越高，但信噪比下降；当狭缝过宽时，图谱的重现性变好，但峰形变宽，有时会将有用的小峰掩盖在其中；（4）如果狭缝选择的较窄，扫描速度应该放慢；因为检测器尽管比人的眼睛灵敏，但也有惰性；当狭缝窄扫描速度快时，检测器的响应速度下降，尤其是类如硅光二极管的检测器更甚；一般仪器说明书中均给出了在某某狭缝下扫描速度的上限，其目的就是保证了分辨率；（5）当仪器的狭缝、扫描速度和采样间隔确立后，仪器的另一个指标“响应速率”对图谱的分辨率也会产生影响；响应速率就是你提到的fast和slow，响应速率的快慢就是对已设定的采样间隔进行集合后的平均处理的效果；响应速率快，采样的点少，对图谱处理的快，真实性和分辨率强，但信噪比略差；响应速率慢，采样的点多，图谱的重现性和光滑性好，但对于小峰的分辨率变差，甚至会使图谱峰值变低和后滞；一般使用时均采用中速，即huangsir“Medium”方式。42 附录：原始数据CrA1os.[nm]575542511453Sample10.1330.09950.05250.0805Sample20.1330.09950.05270.0808Sample30.13320.09950.05290.0811CrA2Pos.[nm]575542511453Sample10.26690.20170.10610.1446Sample20.2670.20170.10610.1454Sample30.26710.20170.10610.1457CrA3huangsirPos.[nm]575542511453Sample10.40340.30580.16010.2088Sample20.40370.3060.16040.2099Sample30.40380.30610.16050.2106CrA4Pos.[nm]575542511453Sample10.54670.41550.21780.2766Sample20.54690.41550.2180.278Sample30.54690.41570.21820.2793CoA1Pos.[nm]575542511453Sample10.02040.09760.16530.0796Sample20.02120.09830.16560.0799Sample30.02090.09810.16570.08CoA2Pos.[nm]575542511453Sample10.04640.20090.33670.1652Sample20.04660.20130.33680.1655Sample30.04670.20190.33720.1656CoA3Pos.[nm]575542511453Sample10.07060.30390.50820.2495Sample20.07090.30490.50880.2501Sample30.07090.30540.50890.250143 CoA4Pos.[nm]575542511453Sample10.09630.41030.68570.3373Sample20.09630.41120.6860.3375Sample30.09670.41220.68630.3376SPA1Pos.[nm]575542511453Sample10.15790.20210.22480.1625Sample20.15810.20220.22220.1623Sample30.1580.20240.22270.1616CrB1Pos.[nm]huangsir575542511453Sample10.1310.09910.05380.0799Sample20.13140.09940.05410.0806Sample30.13150.09930.0540.0812CrB2Pos.[nm]575542511453Sample10.26990.20510.10970.148Sample20.27010.2050.10980.1487Sample30.27030.20530.110.1491CrB3Pos.[nm]575542511453Sample10.40820.31050.16440.2127Sample20.40860.31070.16470.2138Sample30.40880.31090.16490.214CrB4Pos.[nm]575542511453Sample10.55230.42160.22490.2853Sample20.55290.42220.22680.2862Sample30.55370.42270.22550.2872CoB1Pos.[nm]575542511453Sample10.02940.10670.17480.0904Sample20.02960.1070.17490.0908Sample30.02870.10730.1750.090844 CoB2Pos.[nm]575542511453Sample10.05080.20610.34210.1706Sample20.0510.20640.34210.1707Sample30.05120.20680.34270.1708CoB3Pos.[nm]575542511453Sample10.07710.31140.51710.2588Sample20.07770.3120.51750.259Sample30.07810.31280.51790.2592CoB4Pos.[nm]575542511453Sample10.09930.41090.6850.34Sample2huangsir0.10050.41260.68580.3403Sample30.10040.41340.68630.3405SPB-1Pos.[nm]575542511453Sample10.16470.20990.23080.1681Sample20.16550.21040.23110.1693Sample30.16540.21080.23150.169245'