1、20. 在一根2m长的色谱柱上,分析一个混合物,得到以下数据:苯、甲苯、及乙苯的保留时间分别为120, 22及31；半峰宽为6.33 8.73, 12.3，求色谱柱对每种组分的理论塔板数及塔板高度。,解：三种组分保留时间及理论塔板数分别为：t苯 = 120 = 80 n = 5.54(80/6.33)2 = 887H = L / n = 2/887 0.23cm t甲苯 = 22 = 122 n = 1083.7 H 0.18 t乙苯 = 31 = 181 n = 1204.2 H 0.17,21. 在一根3m长的色谱柱上，分离一试样，得如下的色谱图及数据：（1）用组分2 计算色谱柱的理论塔板
2、数；（2）求调整保留时间tR(1)及tR(2)；（3）若需达到R =1.5，所需的最短柱长为几米？,解：tR(2)=17min, Y2=1min, n = 16(t/Y)2 =16172 = 4624tR(1) = tR(1) tM =14-1=13min tR(2) = 16min, = tR2/tR1=16/13=1.231 L=16R2(1.231/(1.231-1)2 Heff Heff = 0.1cm, L=102.2cm 1m,22. 分析某种试样时，两个组分的相对保留值r21=1.11, 柱的有效塔板高度H=1mm，需要多长的色谱柱才能完全分离？,L=3.66m,25. 丙烯和丁
3、烯的混合物进入气相色谱柱得到如下数据：,解： k = t/tM = (4.8-0.5)/0.5=8.6R = t丁 t丙2/(Y丁+Y丙) = (4.83.5)2/(1.0+0.8) =1.44,29.测得石油裂解气的气相色谱图（前面四个组分为经过衰减1/4而得到），经测定各组分的f 值并从色谱图量出各组分峰面积为：,30. 有一试样含甲酸、乙酸、丙酸及不少水、苯等物质，称取此试样1.055g。以环己酮作内标，称取环己酮0.1907g，加到试样中，混合均匀后，吸取此试液3mL进样，得到色谱图。从色谱图上测得各组分峰面积及已知的S值如下表所示：,求甲酸、乙酸、丙酸的质量分数。,解：内标法,w甲酸
4、 = (14.8/133)(0.1907/1.055) 3.831 100% = 7.71% w乙酸 = (72.6/133) (0.1907/1.055) 1.779 100% = 17.55% w丙酸 (42.4/133) (0.1907/1.055) 1.07 100% = 6.17%,仪器分析补充练习,1、Ethanol and methanol are separated in a capillary GC column with retention times of 370 and 385s, respectively, and base widths (wb) of 16.0 a
5、nd 17.0s. An unretained air peak occurs at 10.0s. Calculate the separation factor and the resolution.,2、Three compounds, A, B and C, exhibit retention factors on a column having only 500 plates of kA = 1.40, kB = 1.85, and kC = 2.65. Can they be separated with a minimum resolution of 1.05?,RAB =0.88
6、; RBC=1.22,A B C,3. The phenol (苯酚) in a waste water sample is analyzed by capillary GC. The 1L phenol standard solution with different concentration is spiked. The data are showed in following table. The 1L waste water sample is spiked after enriched 100 times, the peak height is 6cm. The recovery
7、rate (回收率) is 92%. What is the concentration of phenol in the sample?,解：外标法标准工作曲线法定量,绘制峰高-浓度 标准工作曲线,c = 0.00174mg/mL,Enriched 100 times,c = 1.74mg/L,The recovery rate is 92%.,c = 1.89mg/L,4. A water sample is analyzed for traces of benzene using GC. Samples and standards are spiked with a fixed amount of toluene as internal standard. The following data are obtained: What is the concentration of benzene in the sample?,ppb Benzene Peak Area Benzene Peak Area Toluene10.0 252 37615.0 373 37025.0 636 371Sample 533 368,解：内标法作图法定量,c = 21.2ppb,以CBenzene为横坐标,作图：,纵坐标,
