What effect does the size of an amino acid on the retention factor?

According to proteomic data analysis, the N-terminus residues highly influence the retention of amino acids due to their role in ion-pairing. Every amino acid has a retention coefficient factor depending on the N-terminus residues it contains. Therefore, the longer the amino acid the higher the likelihood of it having high N-terminus residues and consequent high retention co-efficient.  

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is correct hope this   also i learnd this in middle school