Abstract:

According to the zinc cadmium reduction method in China Specification for Oceanographic Survey, surface area of circular zinc coil of 1.5 cm diameter is 30 cm 2 for the 50 mL sample. We improved the circular coil to the Archimedes′ spiral coil of the interval 2πa greater than 10 mm, the nitrate concentrations with the spiral coil are 11% higher than that with the circular coil. In the area tests of the spiral coil and for 4 μM concentrations of standard nitrate solution, the concentration value becomes saturated beyond 35 cm 2. As for 14 μM concentration, the concentration value approaches saturated until at 45 cm 2. So the 30 cm 2 area of the circular coil in the Specification is not enough. In the range between 1 and 17 μM, the relative errors of nitrate concentrations with the spiral coils of the F98072 and 931210 serial numbers (Shanghai Chemical Reagent Co.) are about 19%-23%.