Abstract:

In recent years, separation and analysis workers have made considerable progress on ultra performance liquid chromatography (UPLC). A lot of separation works have been completed which have never been done before. But the theory about chromatographic dynamics of UPLC from the beginning up to now, is remaining in 1950's. Some people explain the principle of UPLC by the van Deemter equation, but this is not right. In this paper, the dynamic process of UPLC has been studied. According to the chromatographic dynamics principle and starting from the heat conduction equation, the plate height equation of UPLC including the influence of mobile phase friction heat production has been deduced as follows: H=2γD_m/u+((2λd_pu^1/3)/(u^1/3+ω(D_m/d_p)^1/3))+((2ku)/((1+k)²(1+κ₀)κ_d))+ ((θ(κ₀+κ₀k+k)²d_p²u)/(D_mκ₀(1+κ₀)²(1+k)²)) +(κ_i(κ₀+κ₀k+k)²d_p^5/2u^2/3)/(3κ₀Ω D_m^2/3(1+κ₀)²(1+k)²+(r₀²(κ₀+κκ₀k+k)u)/(4(1+k)D_r)exp(-Kr₀²α). The last item on the right represents the contribution of mobile phase friction heat. When the linear velocity of mobile phase is lower, the contribution of mobile phase friction heat tending to become zero, the plate height equation is reduced to the Horvath and Lin equation. When the linear velocity of mobile phase is high, the temperature difference between the column axial center and edge is directly proportional to the mobile phase linear speed square, and the contribution of thermal effect will largely increased. In this paper, the author clearly pointed out that the column efficiency of UPLC has a direct bearing on the column diameter. Using fine diameter column is helpful to implement column efficiency. Too high mobile phase velocity will lead to the column efficiency collapsed.

Key words: chromatographic dynamics, column efficiency collapsed, plate height equation, ultra performance liquid chromatography (UPLC)