Determination of Major Inorganic Ions in Solution of the Nutrient Film Technique Hydroponic System by CZE with Capacitively Coupled Contactless Conductivity Detection

Major nutrients in a NFT spinach hydroponic solution, cations (K+, Ca2+, mg(2+), Na+) and anions (NO3-, SO42-, H2PO4-), were analyzed by CE with capacitively coupled contactless conductivity detection ((CD)-D-4). (CD)-D-4 was fitted on a fused silica capillary (i.d., 50 mu M; o.d., 375 mu M; total length, 60 cm) at the position of 45 cm from an inlet. Electrophoresis buffers were 12 mol L-3 histidine - 117 mol L-3 acetic acid (pH 3.7) (cation analysis), and 10 mol L-3 histidine - 50 mol L-3 malic acid (pH 3.0) (anion analysis). All peaks were completely separated and linear calibration ranges were between 20 mol L-6 and 500 mol L-6 (K+), 20 mol L-6 and 1000 mol L-6 (NH4+, Ca2+, Na+, Mg2+), 100 mol L-6 and 1000 mol L-6 (anions). The obtained results were verified using ICP-OES and ion chromatography. As an actual application, the major nutrients of the NFT hydroponic solution of spinach cultivation were successfully measured.