In a recent report, two columns were compared for the analysis of organic acids
ID: 556360 • Letter: I
Question
In a recent report, two columns were compared for the analysis of organic acids in fruit juices. The following retention times were recorded:
If column 1 is an Ion exchange column (separation by charge) and column 2 is a reversed phase column (separation by polarity) answer the following questions. Structures and other data may be useful.
a. Based on the above data, describe which column you think is the best for the separation and why.
b. Why is the elution order different for the different columns? Describe in chemical terms.
Chromatographic column data Acid Column 1 -Retention Column 2 Retention k' times (min) k' Times (min) unretained species Oxalic Acid Shikimic acid Succinic acid Quinic Formic acid 1.35 4.3 7.2 7.5 6.2 8.3 0.5 1.45 2.53 5.4 1.81 1.87 column 1 column 2 0.00 1.90 4.06 9.80 2.62 2.74 0.00 2.19 4.33 4.56 3.59 5.15Explanation / Answer
If column 1 is an Ion exchange column (separation by charge) and column 2 is a reversed phase column (separation by polarity)
The separation of solutes in chromatography depends on two factors:
(1) a difference in the retention of solutes (i.e., a difference in their time or volume of
elution
(2) a sufficiently narrow width of the solute peaks (i.e, good efficiency for the separation
system)
Answer (a) Column 2 is a reversed phase column (separation by polarity) is the best for the separation because its rention time is lesser than the Column 1 in all organic acids which are presentin fruit juices therefore, Column 2 has high average migration rate.
Answer(b) The elution order different for the different columns in terms of elution volume instead of elution time. If volumes are used, the volume of the mobile phase that it takes to elute a peak off of the column is referred to as the retention volume (VR) and the amount of mobile phase that it takes to elute a non-retained component is referred to as the void volume (VM).Thus the elution order is different .
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