An instrumental analysis experiment based on engineeringliberal arts integration：determination of Na+，K+，Ca2+，and Mg2+ in mural ground layers by capillary electrophoresis with capacitively coupled contactless conductivity detection

In the context of the construction of new engineering disciplines, this paper designs an undergraduate instrument analysis experiment based on the cross fusion of "engineering and culture", using the practical issues of cultural relic protection as the carrier.

The experiment focused on salt damage to the Maijishan murals and established an analytical method for simultaneous determination of Na+, K+, Ca2+, and Mg2+using capillary electrophoresis capacitance coupled non-contact conductivity detection (CE-C4D) technology. This method was applied to the quantitative analysis of four cations in the basement of Maijishan cave murals. The figure numbered 1 is the abstract diagram of the paper; Figure 2 is Figure 1 in the paper, which is a schematic diagram of capillary electrophoresis separation; Figure 3 is Figure 2 in the paper, which is a schematic diagram of the C4D detection pool; Figure 4 is Figure 3 in the paper, which shows the electrophoretic spectra of cations under different concentrations of (a) imidazole and (b) tartaric acid; Figure 5 is Figure 4 in the paper, which shows the electrophoresis spectra of four cations under different separation voltages; The figure numbered 6 is Figure 5 in the paper, which includes (a) the electrophoresis spectra of four cations at different injection times, and (b) the scatter plot and linear fitting results of peak area variation with injection time; Figure 7 is Figure 6 in the paper, which shows the electrophoretic spectrum of cations in the sample water extraction solution.