Abstract
To quantify inorganic phosphate (PO43-) in salts for this study, we used transient isotachophoresis (tITP) / capillary zone electrophoresis (CZE) with indirect UV detection. As a slight modification of a PO43- detection method developed earlier for seawater, a terminating ion (TI) was intentionally not introduced into the background electrolyte (BGE) in the capillary. Instead, a UV-absorbing compound in the BGE served as the TI: 2,6-pyridinedicarboxylic acid (PDC). Furthermore, instead of 200 nm, a 273 nm detection wavelength was used because of its better signal-to-noise (S/N) ratio. The relative standard deviation (RSD) values (n ＝ 4) for peak area, peak height, and migration time of PO43- were, respectively, 3.8 ％, 3.6 ％, and 0.53 ％. The limit of detection (LOD, S/N ratio ＝ 3) and limit of quantification (LOQ, S/N ratio ＝ 10) for PO43- were, respectively, 0.013 and 0.044 mg/L (as P (PO43--P)). These LOD and LOQ values correspond to 0.40 and 1.3 mg/kg (per kilogram of salt). After applying the proposed method to quantify PO43- in various salt samples, including seaweed salt, the obtained CZE results showed agreement with those obtained using molybdenum blue absorptiometry (conventional method). These findings demonstrate this method as valid for detecting PO43- in salts.
