Precautions for detecting potassium ions in water

1. Problems to be paid attention to when dealing with potassium ion water samples 1. The sample should be analyzed as soon as possible after collection, otherwise it will be adsorbed on the container wall and the final measurement result of the water sample will be low. 2. Do not evaporate the sample to dryness after digestion, otherwise it is easy to lose. When the sample composition is complex, it can be digested repeatedly with nitric acid-perchloric acid until the solution is clear and can be used. 3. Before adding perchloric acid, pre-digest with nitric acid to destroy a large amount of reducing organic matter, then add perchloric acid for final digestion, so as to better remove impurities. 4. Neutral or alkaline water samples should not be used in glass bottles, especially soft glass bottles, otherwise they will be easily polluted by potassium and sodium. 5. Water samples should be stored in plastic bottles, and the pH should be adjusted with nitric acid<2. 2. Details that need to be paid attention to when measuring potassium ions in water 1. Potassium is an alkali metal with a low ionization potential, which is prone to interference in flames. The method of adding sodium as a 'deionizer' can suppress interference. 2. Gas cylinders should avoid heat, impact, sunlight and baking. When carrying gas bottles, protective caps and shockproof rubber rings should be put on, and they should be handled and placed with care to prevent throwing, knocking, rolling or violent vibration. Yan Fen beat the valve with a metal tool. It is strictly forbidden to exhaust the gas in the bottle, and a residual pressure of not less than 0.05MPa must be kept. Oxygen cylinders and flammable gas cylinders should not be placed in laboratories or corridors, but should be placed upright and fixed with shelf collars. Oxygen cylinder valves and pressure reducing valves are strictly prohibited from adhering to grease, and it is not allowed to wear grease-sticky gloves to open the valves. It must be more than 10m away from an open flame and must be upright when used. The oxygen pressure reducer can be used for O2, N2, Ar, He, air, and the thread is right-handed (commonly known as positive buckle). The hydrogen pressure reducer can be used for H2 and CO combustible gases, and the thread is left-handed (commonly known as reverse buckle). When using acetylene gas as fuel, the acetylene cylinder contains fillers such as acetone and diatomaceous earth. When the pressure is lower than 0.5MrPa, the steel cylinder should be replaced to prevent the acetone and other substances in the cylinder from flowing into the flame along the pipeline, resulting in unstable flame combustion and increased noise. When the acetylene cylinder is used, the outlet of the cylinder valve is equipped with a special pressure reducer and a flashback preventer, and the venting pressure shall not exceed 0.15MPa. It is strictly forbidden to use it in the case of leakage. Check the pipeline frequently to prevent gas leakage and strictly abide by the relevant operating procedures. The selection of the pressure reducer should pay attention to the pressure range of high pressure and low pressure, and ensure that the pressure upper limit of the high pressure gauge of the reducer is greater than the gas pressure of the cylinder, and the upper limit of the pressure of the low pressure gauge is greater than the operating pressure. After the pressure reducer is installed, it should be checked with soap liquid to make it tight and airtight. When opening the high-pressure gas cylinder, first check whether the screw of the pressure reducing valve is loose. The operator should stand on the side of the gas cylinder outlet and move slowly to reduce air friction and prevent static electricity. Before opening the cylinder, turn off the low-pressure gauge first, and then open the low-pressure gauge after the cylinder is opened and adjust the output pressure to the required value. 3. Concentration in nitric acid>8%, sulfuric acid concentration>2%, the absorbance is low. When the concentration of hydrochloric acid and perchloric acid increases, the absorbance decreases obviously. Therefore, the acidity of the standard series and water samples should be consistent during operation. Generally, 2% nitric acid is suitable. 4. Potassium and sodium are constant elements and must be handled carefully, paying attention to the pollution caused by utensils and reagents. If possible, it is recommended to use quartz glassware. 5. For high-concentration samples, use a sub-sensitive line or rotate the combustion head to a certain angle to shorten the optical path to avoid errors caused by dilution. 6. During the measurement, the liquid level of the tested water sample and the standard solution should be kept as consistent as possible, so that the inhalation volume should be as consistent as possible. 7. If the purpose of measuring potassium ions is to determine the concentration multiple of circulating cooling water, the water sample can be diluted according to the operating conditions, so that the salt content is close to that of the supplementary water, and then measured, which can relatively eliminate interference.