In LC, what is the effect on the retention time of a peak (increase, decrease, r

Question

In LC, what is the effect on the retention time of a peak (increase, decrease, remain the same, become zero) by (5 marks)

(a) Decreasing the particle size in packed column HPLC (at constant pressure)? (b) Increasing the column pressure?

(c) Increasing the polarity of the mobile phase in “reversed-phase” HPLC?

(d) Using a less-polar stationary phase in “normal-phase” HPLC?

(e) Using a more efficient column with twice as many plates with the same length, mobile, and stationary phase compositions, operated at the same flow rate?

Explanation / Answer

(a) If decreasing the particle size in packed column HPLC (at constant pressure) then the retention time of a peak in LC is remain the same.

(b) If increasing the column pressure then the retention time of a peak in LC is increases.

(c) If increasing the polarity of the mobile phase in “reversed-phase” HPLC then the retention time of a peak in LC is decreases

(d) If a less-polar stationary phase in “normal-phase” HPLC then the retention time of a peak in LC is decreases

(e) If using a more efficient column with twice as many plates with the same length, mobile, and stationary phase compositions, operated at the same flow rate then the retention time of a peak in LC is remain the same

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