In the general test section of Japan’s Specifications and Standards for Food Additives (9th edition), the chloride limit test, a visual inspection method, is “designed to demonstrate that the content of chloride in an additive does not exceed the acceptable limit specified in the individual monograph.” Because the chloride limit test is a visual inspection test, it determines the concentration of chloride that can be distinguished visually. The visual inspection method, on the other hand, makes it challenging to distinguish small differences in chloride concentration. The visual inspection method could not distinguish between adjacent chloride standard solutions unless there was a significant difference in concentration of more than 0.1 µg/mL for 0–0.5 µg/mL chloride standard solutions, more than 0.5 µg/mL for 0.5–1 µg/mL of chloride, and more than 1 µg/mL for 1–4 µg/mL chloride standard solutions. As a result, we examined the use of a UV-visible spectrophotometer to measure the absorbance of silver chloride (UV-Vis method). After the absorbance stabilized, a UV-Vis spectrophotometer was used to measure the absorbance at 600 nm after adding silver nitrate solution to either the test or chloride standard solution (approximately one hour). The calibration curve was linear (R2> 0.99) for concentrations ranging from 0.05 to 5 µg/mL, which are difficult to distinguish visually. By spiking samples with chloride equivalent to the criteria for three sample types: glycine, sodium dihydrogen phosphate, and sodium sulfate, this method was validated. After that, the chloride was quantified using the UV-Vis method. The UV-Vis method’s accuracy and precision were comparable to that of ion chromatography for the direct detection of chloride ions, with satisfactory accuracy (≥ 92.6%), precision (≤ 3.7%) and intra-laboratory reproducibility (≤ 7.3%). These results indicate that the UV-Vis method can discriminate against small differences in chloride concentrations that are difficult to determine using visual inspection methods. As a result of this study, it was demonstrated that the UV-Vis method is a simple and effective method for accurately determining chloride concentrations in test solutions
