The following data was obtained for an experiment on the gas chromatographic determination of toluene in an unknown sample using the internal standard method. Concentration (mass %) Toluene Peak Area Ethylbenzene Peak Area 0.50 0.539 1.970 1.00 1.150 2.051 2.00 2.174 2.018 3.00 3.308 2.009 unknown 1.382 2.015 a) Plot the calibration curve for this analysis and calculate the slope, y-intercept, and Pearson correlation coefficient. b) Find the % of toluene in the unknown.

The figure below shows a portion of a GC chromatogram for a mixture of two aromatic compounds labeled A and B. The separation employed a 2.50 meter packed column under isothermal conditions (90 °C) and a flow rate of 10 mL/min. Detector Signal 300.0 250.0 200.0 150.0 100.0 50.0 0.0 1.0 1.1 Unretained 1.5 time (min) Find the times that components A and B spend in the stationary phase. 2.0

would column chromatography separate ketone and alcohol

A3

5

1. From spinach, the chromatographic analysis will yield two major substances: (a) B-carotene (C40H56), which will separate from the spinach mixture to form a yellow band, and (b) chlorophyll A (CSSH72MGN4OS), which will separate from the mixture to form a green band. i. Describe the characteristics and draw structures of these molecules. ii. From the spectrophotometric analysis, what wavelength (Amax) would you expect ß-carotene (C40H56) to absorb? What wavelength would chlorophyll A (CssH72MgN4O5) absorb?

the linear trendline equation y= 4.7033x + 0.0045

The following data give the recovery of bromide from spiked samples of vegetable matter, measuredusing a gas–liquid chromatographic method. The same amount of bromide was added to each specimen(Roughan, J.A., Roughan, P.A. and Wilkins, J.P.G., 1983, Analyst, 108: 742).Tomato: 777 790 759 790 770 758 764 ug/gCucumber: 782 773 778 765 789 797 782 ug/g(a) Test whether the recoveries from the two vegetables have variances which differ significantly.(b) Test whether the mean recovery rates differ significantly.

With the following information for a GC analysis using an internal standard, calculate the percentage of alcohol in the sample. The 1% ethanol standard sample has an ethanol peak area of 711 and a 1-propanol peak area of 9253; 3% is 3536 and 14432 for ethanol and 1-propanol respectively; 5% is 3506 and 10693; 7% is 5874 and 10847 and 9% is 5203 and 7522. The beer sample has an ethanol peak area of 5471 and 1-propanol of 14384. 4.95% 5.15% 5.05% 5.25%

A gas chromatogram of a mixture of toluene and ethyl (a) Measure w1/2 for each peak to the nearest 0.1 mm. When the thickness of the pen trace is significant relative to the length being measured, it is important to take the pen width into account. It is best to measure from the edge of one trace to the corresponding edge of the other trace, as shown at the bottom of the left column. (b) Find the number of theoretical plates and the plate height for each peak.