A method for improving the accuracy of iodometric measurement of samples containing interfering substances
A technology of interfering substances and iodometric method, which is applied in the field of analysis and detection, can solve problems such as difficult and accurate measurement, and achieve the effect of easy operation and low dosage
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Embodiment 1
[0040] Embodiment 1. Direct iodometric method measures vitamin C in a certain sample
[0041] The normal method is:
[0042] Accurately weigh an appropriate amount of vitamin C-containing sample (or prepare an aqueous solution with a suitable concentration in advance), add appropriate amount of pure water, add 10mL 2mol / L acetic acid and 1mL 1% starch solution, and immediately titrate with 0.05mol / L iodine standard solution to Stable light blue, no fading within 30 seconds is the end point. Record the volume of iodine standard solution consumed. At the same time, titrate the reagent blank with pure water, and record the volume of iodine standard solution consumed by the blank.
[0043] When the sample contains interfering substances (OA-12), the titration end point is turbid with the above method, and the starch cannot develop color. The following improved methods can be used to solve the problem:
[0044] Accurately weigh an appropriate amount of vitamin C-containing samp...
Embodiment 2
[0045] Embodiment 2. residual iodometric method measures formaldehyde in a certain sample
[0046] The normal method is:
[0047] Accurately weigh an appropriate amount of formaldehyde-containing sample (or prepare an aqueous solution with a suitable concentration in advance), add 20.00mL 0.1mol / L iodine solution and 15mL 1mol / L sodium hydroxide solution, and let it stand for 15min. Add 20mL of 0.5mol / L sulfuric acid solution and let it stand for 15min. Titrate with 0.1mol / L sodium thiosulfate standard solution until the solution is light yellow, add 1mL of 0.5% starch solution and continue titrating until the blue just fades as the end point. Record the volume of sodium thiosulfate standard solution consumed. At the same time, titrate the reagent blank with pure water, and record the volume of sodium thiosulfate standard solution consumed by the blank.
[0048] When the sample contains interfering substances (1227), use the above method to titrate the end point to be tur...
Embodiment 3
[0050] Embodiment 3: the available chlorine of certain disinfectant is measured by displacement iodometric method
[0051] The normal method is:
[0052] Accurately weigh an appropriate amount of chlorine-containing disinfectant (or an aqueous solution of a suitable concentration prepared in advance) in a 100mL iodine measuring bottle, add 10mL 2mol / L sulfuric acid, 10mL 100g / L potassium iodide solution, and place in a dark place for 5 minutes. Titrate with 0.1mol / L sodium thiosulfate standard solution until the solution is light yellow, add 10 drops of 5g / L starch solution, continue titrating until the blue color disappears, record the volume of consumed sodium thiosulfate standard solution. At the same time, titrate the reagent blank with pure water, and record the volume of sodium thiosulfate standard solution consumed by the blank.
[0053] When the sample contains interfering substances (OA-12), the titration end point is turbid with the above method, and the starch ca...
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