Objective:To establish a rapid method for urinary iodine determination based on arsenic-cerium catalytic spectrophotometry using semiconductor water bath rapid cooling digestion technology (rapid cooling method) and an automated iodine analyzer.Methods:Urine samples were collected from three staff members randomly selected at the Gansu Provincial Center for Disease Control and Prevention. The samples were mixed and divided into three equal portions. Using rapid cooling method instead of traditional natural cooling method, the mixed urine sample was lowered from 100 ℃ to the measurement temperature (30 ℃), and then the urine iodine was determined by arsenic cerium catalytic spectrophotometry using a fully automatic iodine analyzer. The differences between the two cooling methods were compared. Additionally, the rapid cooling-arsenic-cerium catalytic spectrophotometry method was validated in terms of the linear equation of the standard curve, precision, accuracy (using urinary iodine reference materials GBW09110e and GBW09109m, and spike recovery experiments), and detection limit.Results:Using the rapid cooling method, the temperature of urine samples reached 30 ℃ in 40 minutes, while the natural cooling method required 120 minutes to reach the same temperature. Urinary iodine levels determined by the rapid cooling method in the three samples were (158.3 ± 1.9), (133.7 ± 2.7), and (219.2 ± 3.1) μg/L, respectively, while those determined by the natural cooling method were (155.5 ± 2.7), (136.2 ± 2.3), and (215.1 ± 3.9) μg/L, respectively. There was no statistically significant difference between the results of the two methods ( t = 1.43, P = 0.192). In the validation experiments for the rapid cooling method, the linear equations for the low-concentration (0 - 300 μg/L) and high-concentration (300 - 1 200 μg/L) iodine standard series were y = - 0.003 0 x + 0.117 5 ( r = - 0.999 7) and y = - 0.001 5 x + 0.649 3 ( r = - 0.999 8), respectively. The precision experiments showed that the relative deviation values of the repeated tests for two different iodine concentrations (300 and 600 μg/L) were 1.99% and 1.90%, respectively. The accuracy experiments demonstrated that the repeated test results for the national urinary iodine reference materials (GBW09110e and GBW09109m) were 216.8 and 134.7 μg/L, respectively, with relative standard deviations of 1.04% and 1.35%, respectively, all within the reference ranges[(218 ± 15) and (135 ± 10) μg/L]. The detection limit was 1.20 μg/L. The spike recovery rate ranged from 92.90% to 99.10%, with an average recovery rate of 96.77%. Conclusions:The rapid cooling-arsenic-cerium catalytic spectrophotometry method not only shortens the time required for urinary iodine determination and improves the speed of measurement, but also provides accurate results, which can be applied when a large number of urine samples need to be measured in a short period of time.

Objective:To establish a rapid method for urinary iodine determination based on arsenic-cerium catalytic spectrophotometry using semiconductor water bath rapid cooling digestion technology (rapid cooling method) and an automated iodine analyzer.Methods:Urine samples were collected from three staff members randomly selected at the Gansu Provincial Center for Disease Control and Prevention. The samples were mixed and divided into three equal portions. Using rapid cooling method instead of traditional natural cooling method, the mixed urine sample was lowered from 100 ℃ to the measurement temperature (30 ℃), and then the urine iodine was determined by arsenic cerium catalytic spectrophotometry using a fully automatic iodine analyzer. The differences between the two cooling methods were compared. Additionally, the rapid cooling-arsenic-cerium catalytic spectrophotometry method was validated in terms of the linear equation of the standard curve, precision, accuracy (using urinary iodine reference materials GBW09110e and GBW09109m, and spike recovery experiments), and detection limit.Results:Using the rapid cooling method, the temperature of urine samples reached 30 ℃ in 40 minutes, while the natural cooling method required 120 minutes to reach the same temperature. Urinary iodine levels determined by the rapid cooling method in the three samples were (158.3 ± 1.9), (133.7 ± 2.7), and (219.2 ± 3.1) μg/L, respectively, while those determined by the natural cooling method were (155.5 ± 2.7), (136.2 ± 2.3), and (215.1 ± 3.9) μg/L, respectively. There was no statistically significant difference between the results of the two methods ( t = 1.43, P = 0.192). In the validation experiments for the rapid cooling method, the linear equations for the low-concentration (0 - 300 μg/L) and high-concentration (300 - 1 200 μg/L) iodine standard series were y = - 0.003 0 x + 0.117 5 ( r = - 0.999 7) and y = - 0.001 5 x + 0.649 3 ( r = - 0.999 8), respectively. The precision experiments showed that the relative deviation values of the repeated tests for two different iodine concentrations (300 and 600 μg/L) were 1.99% and 1.90%, respectively. The accuracy experiments demonstrated that the repeated test results for the national urinary iodine reference materials (GBW09110e and GBW09109m) were 216.8 and 134.7 μg/L, respectively, with relative standard deviations of 1.04% and 1.35%, respectively, all within the reference ranges[(218 ± 15) and (135 ± 10) μg/L]. The detection limit was 1.20 μg/L. The spike recovery rate ranged from 92.90% to 99.10%, with an average recovery rate of 96.77%. Conclusions:The rapid cooling-arsenic-cerium catalytic spectrophotometry method not only shortens the time required for urinary iodine determination and improves the speed of measurement, but also provides accurate results, which can be applied when a large number of urine samples need to be measured in a short period of time.