Dear Hamideh Bakhshayeshan-Agdam thanks a lot

Dear Roberta Tardugno thanks a lot

There is no specific difference between Retention Index and Kovats Retention Index, the difference is on the formula content only. In The GC-MS, Kovats retention index, shorter Kovats index or retention index, is used to convert retention times into system-independent constants. Generally, Both formula results are dependent on the compound's RT, hence each formula can be used. It is worth noting that you are free to choose the formula, but for all compounds identified in one chromatogram, one (same) formula must be used to evaluate the accuracy of the assay.