色譜作業(yè)解答.ppt

1、20. 在一根2m長(zhǎng)的色譜柱上,分析一個(gè)混合物,得到以下數(shù)據(jù):苯、甲苯、及乙苯的保留時(shí)間分別為120, 22及31；半峰寬為6.33 8.73, 12.3，求色譜柱對(duì)每種組分的理論塔板數(shù)及塔板高度。,解：三種組分保留時(shí)間及理論塔板數(shù)分別為： t苯 = 120 = 80 n = 5.54(80/6.33)2 = 887 H = 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長(zhǎng)的色譜柱上，分離一試樣，得如下的色譜圖及數(shù)據(jù)：（1）用組分2 計(jì)算色譜柱的理論

2、塔板數(shù)；（2）求調(diào)整保留時(shí)間tR(1)及tR(2)；（3）若需達(dá)到R =1.5，所需的最短柱長(zhǎng)為幾米？,解：tR(2)=17min, Y2=1min, n = 16(t/Y)2 =16172 = 4624 tR(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. 分析某種試樣時(shí)，兩個(gè)組分的相對(duì)保留值r21=1.11, 柱的有效塔板高度H=1mm，需要多長(zhǎng)的色譜柱才能完全分離？,解：根據(jù)公式：,L=3.6

3、6m,25. 丙烯和丁烯的混合物進(jìn)入氣相色譜柱得到如下數(shù)據(jù)：,解： k = t/tM = (4.8-0.5)/0.5=8.6 R = t丁 t丙2/(Y丁+Y丙) = (4.83.5)2/(1.0+0.8) =1.44,29.測(cè)得石油裂解氣的氣相色譜圖（前面四個(gè)組分為經(jīng)過衰減1/4而得到），經(jīng)測(cè)定各組分的f 值并從色譜圖量出各組分峰面積為：,30. 有一試樣含甲酸、乙酸、丙酸及不少水、苯等物質(zhì)，稱取此試樣1.055g。以環(huán)己酮作內(nèi)標(biāo)，稱取環(huán)己酮0.1907g，加到試樣中，混合均勻后，吸取此試液3mL進(jìn)樣，得到色譜圖。從色譜圖上測(cè)得各組分峰面積及已知的S值如下表所示：,求甲酸、乙酸、丙酸的質(zhì)量分

4、數(shù)。,解：內(nèi)標(biāo)法,w甲酸 = (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%,儀器分析補(bǔ)充練習(xí),1、Ethanol and methanol are separated in a capillary GC column with retention times of 370 and 385s, respectively, and base widths (w

5、b) of 16.0 and 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 1.0

6、5?,RAB =0.88; 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. T

7、he recovery rate (回收率) is 92%. What is the concentration of phenol in the sample?,解：外標(biāo)法標(biāo)準(zhǔn)工作曲線法定量,繪制峰高-濃度 標(biāo)準(zhǔn)工作曲線,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 Benzen