Passage IV
In high performance liquid chromatography (HPLC), a sample solution is injected into a continuous flow of solvent, which carries the sample through a column packed with an adsorbent (see Figure 1).
The components of the sample separate from each other in the column. As each component passes through the detector, a peak is plotted on a graph. The portion (fraction) of solvent containing each component of the sample can then be collected and analyzed. The retention time (RT) is the time it takes for half of the component to pass through the column (the time that corresponds to the top of the peak).
Two experiments were done to analyze foods for the presence of sugars (which have the suffix "ose") and sugar alcohols (which have the suffix "itol"）
Experiment 1
A 0.01 mL sample of a solution containing 1 g/L each of several sugars and sugar alcohols was injected into the HPLC apparatus. The flow rate (FR) of solvent through the apparatus was 1.5 mL/min. The detector readings were plotted, and the fraction corresponding to each peak was collected and analyzed to determine its composition. The procedure was repeated at different FRs (see Figure 2).
Experiment 2
For each of 7 foods, a 1 g sample was mixed with 500 mL of ethanol in a blender, then stored overnight. Each mixture was filtered and then diluted to 1.000 L with ethanol. A 0.01 mL sample of this solution was analyzed by HPLC at FR = 0. 5 mL/min (see Table 1).
18. Which of the following lists includes all of the sugars detected in the apple juice sample in Experiment 2 ?
Your Answer is
Correct Answer is G
Explanation
Look at table 1 first, the RTs in apple juice are 4.7, 6.4, 7.6, and 12.8 respectively;
Because FR=0.5 in Experiment 2, you should look at the third picture in figure 2 , the sugars corresponding to the above RT should include sucrose, glucose, and fructose