The construction of a simple sensor for the simultaneous detection of nitrite and thiosulfate by heme catalysis

Several simple sensors were fabricated through a one-step method. By depositing electro-active compounds, such as β-cyclodextrins (β-CD), heme, dopamine (DA), or Fc-ECG, onto a screen-printed electrode (SPE), the successful simultaneous detection of nitrite (NO₂ ^-) and thiosulfate (S₂O₃ ^2-) ions was observed. Under optimal operating conditions, the notable electrocatalytic abilities of a Heme/SPE sensor were detected for the oxidation of NO₂ ^- and S₂O₃ ^2-, with remarkable peak potential differences, after characterization via SEM, CV, and DPV. Linear relationships were obtained in the ranges of 5.0-200.0 μmol L^-1 and 1.0-100.0 μmol L^-1 for the current response versus concentration of NO₂ ^- and S₂O₃ ^2-, respectively. The limits of detection were determined to be 1.67 and 0.33 μmol L^-1 while the sensitivities of detection were noted to be 0.43 and 1.43 μA μM^-1 cm^-2, respectively. During the detection of NO₂ ^- and S₂O₃ ^2-, no interfering common ions were observed. Furthermore, average recoveries from 96.0 to 104.3% and a total R.S.D. of less than 3.1% were found for the detection of NO₂ ^- and S₂O₃ ^2- in pickled juice and tap water using the simple sensor. These results showed that rapid and precise measurements for actual application in NO₂ ^- and S₂O₃ ^2- detection could be conducted in food samples, indicating a potential use in food safety.