Parameter Migration time, min Peak area ratios   NLB NLX NLT NLB NLX NLT Standard 5.19 4.21 4.55 0.71 0.57 4.35 Acetate buffer pH 3.6 4.0 5.24 5.12 4.14 4.22 4.62 4.46   0.72 0.71   0.57 0.57   4.35 4.35 Acetate buffer concentration, mmolL-1 15 25 5.15 5.30 4.12 4.23 4.35 4.62   0.70 0.71   0.55 0.57   4.34 4.35 Injection time, s 5 7   5.02 5.17 4.20 4.16 4.56 4.48   0.69 0.70   0.56 0.57   4.33 4.35 Applied voltage, kV 13 17 5.34 5.13 4.50 4.30   4.68 4.66   0.71 0.74   0.62 0.57   4.37 4.36 Capillary cartridge temperature, °C 23 27 5.36 5.20 4.32 4.24   4.69 4.63   0.71 0.69   0.63 0.64   4.37 4.38

Table 4: Robustness data using 100 µg mL-1 NLB, 40 µg mL-1 of NLX and 40 µg mL-1 in the presence of 100 µg mL-1 IS.