Metrosep a supp7 250 4.0 mm column

Plant material was lyophilized and finely ground for analysis. After calcination at 550 °C, Na level was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) (Varian Vista-MPX, Varian Australia, Mulgrave, Vic., Australia). Cl⁻ was extracted from ground material (0.4 g) with 20 mL of deionized water. Samples were analyzed in an ion chromatograph (METROHM 861 Advanced Compact IC; METROHM 838 Advanced Sampler) using a METROHM Metrosep A Supp7 250/4.0 mm column.

Pepper leaf samples were oven-dried at 65 °C for 72 h and homogenized with a grinder. Anions were extracted from ground material (100 mg) with 20 mL of deionized water. Samples were analyzed in an ion chromatograph (Metrohm 861 Advanced Compact IC, Metrohm, Herisau, Switszerland) using a Metrohm Metrosep A Supp7250/4.0 mm column. For cation extraction, 50 mg of leaf material were digested at 80 °C in a HNO₃/H₂O₂ solution (5/3, v/v). Cations were dissolved in 0.1 M HCl, diluted with de-ionized water, and filtered. Samples were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES, Vista-MPX, Varian, Australia).