18-Which of the following(s) is /are correst? 1- Peak tailing of chromatographic peak occur when the amount of sample loaded onto the column is too high. II- Column efficiency increases as the no of theoretical plates increases III-Retention factor in colum chrom intography is the amount of time a solute spends in the stationary phase relative to the time it spends in mobile phase. A) Only II B) Iand II C) I and III D) II and III E) I, II and III

The correct answer is D) II and III.<br /><br />Explanation:<br /><br />I. Peak tailing of chromatographic peak occurs when the amount of sample loaded onto the column is too high. This statement is incorrect. Peak tailing occurs when the sample is overloaded, but it is not the amount of sample loaded onto the column that causes peak tailing. Peak tailing is caused by the interaction of the solute with the stationary phase, which can be influenced by factors such as the composition of the stationary phase, the flow rate of the mobile phase, and the temperature.<br /><br />II. Column efficiency increases as the number of theoretical plates increases. This statement is correct. The number of theoretical plates is a measure of the resolving power of the column, and a higher number of theoretical plates indicates a more efficient column.<br /><br />III. Retention factor in column chromatography is the amount of time a solute spends in the stationary phase relative to the time it spends in the mobile phase. This statement is correct. The retention factor (also known as the retention time) is a measure of the amount of time a solute spends in the stationary phase relative to the time it spends in the mobile phase. It is calculated as the ratio of the time the solute spends in the stationary phase to the time it spends in the mobile phase.