The carbazole method and m-hydroxybiphenyl method are used to determine the content of alginate in urea formaldehyde slow-release compound fertilizer containing alginate.With carbazole method,urea formaldehyde nitrogen will cause serious interference to the color development system,making it deviate from Lambert-Beer law,leading to larger results;With the m-hydroxybiphenyl method,urea formaldehyde nitrogen has no interference to the color development system,the measurement conditions are sodium tetraborate sulfuric acid solution added amount of 5.00 mL,chromogenic agent added amount of 100 μL,color development time of 10 minutes,and the measurement wavelength of 525 nm.The relative deviation of this method is 0.22%-0.25%,and the recovery rate is 85.46%-103.64%,the accuracy is high and the precision is good.
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