Method for detecting trace urea in melamine
A detection method and technology for melamine, applied in measurement devices, instruments, scientific instruments, etc., can solve the problems of urea downstream customers unable to stabilize the chemical synthesis of melamine, unstable measurement results, and many interference factors, and achieve short detection time and accuracy. High, easy-to-use effects
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Embodiment 1
[0056] This embodiment provides a method for detecting trace amounts of urea in melamine. Specifically include the following steps:
[0057] (1) Preparation of 0.1mg / mL urea standard solution: Accurately weigh 1.000g of high-grade urea into a beaker, add a small amount of water into an ultrasonic cleaner, ultrasonic frequency: 40KHz, ultrasonic treatment for 10min, so that urea is completely dissolved. Then transfer the dissolved solution into a 1000mL volumetric flask, dilute with water to the mark, and constant volume to obtain 1mg / mL urea standard solution.
[0058]Use a pipette to pipette 10 mL of 1 mg / mL urea standard solution into a 100 mL volumetric flask, and add 90 mL of water to prepare a 0.1 mg / mL urea standard solution.
[0059] (2) Dilute the sample: according to the volume of the urea standard solution in the following table 1, add 0ml, 0.5ml, 1ml, 2ml, 5ml, 10ml, 20ml and 30ml of the 0.1mg / ml urea standard in 8 100ml volumetric flasks Solution, dilute to 100ml...
Embodiment 2
[0071] This embodiment verifies the accuracy of the detection method in embodiment 1. In order to verify the accuracy of the above detection method, a recovery test was carried out.
[0072] Specifically include the following steps:
[0073] Weigh 10g of the sample to be tested and dissolve it in a 500ml volumetric flask, shake well and constant volume to obtain a 0.02g / ml sample to be tested, pipette 90mL into four 100mL volumetric flasks respectively, and accurately Add 0.1mg / mL standard sample 0.5mL, 1mL, 2mL, the addition amount is 0.05mg, 0.10mg, 0.20mg respectively, and then obtain m 样+标 The urea content in (m 样+标 -m 已知待测液尿素含量 ) / m 标 Calculate the recovery rate. The results are shown in Table 2.
[0074] Table 2 Recovery experiment
[0075]
[0076] It can be determined from Table 2 that the recovery rate is 97.73%, which has a good recovery rate and meets the analysis requirements, and also shows that the method has high accuracy.
Embodiment 3
[0078] In this example, the elution conditions and sample processing conditions of Example 1 are used to measure the same sample with different detection wavelengths. Specifically include the following steps:
[0079] Preparation of the sample solution: Accurately weigh 2.0 g of the sample in a 100 ml beaker, add about 60 mL of water, ultrasonic cleaner with an ultrasonic frequency of 40 KHz, ultrasonic for 20 min, transfer to a 100 mL volumetric flask, dilute to the mark with water, shake well, and Set up and filter with a 0.45 μm syringe filter to obtain the sample solution.
[0080] High-performance liquid chromatography analysis conditions: choose a chromatographic column that can withstand pure water phase, with C18 filler (particle size 5 μm), column length 250 μm, inner diameter 4.6 mm; use pure water as mobile phase, flow rate: 1.0mL / min, etc. Speed elution; injection volume 5uL; column temperature 35°C; use different wavelengths for measurement (190nm, 195nm, 200nm...
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