Chemical instrument cleaning method

In the analysis work, washing glass instruments is not only a preparatory work that must be done before the experiment, but also a technical work. Whether the instrument washing meets the requirements will have an impact on the accuracy and precision of the test results. Different analytical work has different requirements for instrument cleaning. We use general quantitative chemical analysis as an introduction to the washing method of the instrument.
(A) Cleansing agents and the most commonly used cleansing agents are soaps, soaps (special products), washing powders, decontamination powders, lotions, and organic solvents.
Soap, soap, washing powder, decontamination powder, for instruments that can be brushed directly with a brush, such as beakers, flasks, reagent bottles, etc.; lotions are used for instruments that are inconvenient for brush scrubbing, such as burettes, pipettes Specially shaped instruments such as flasks, distiller, etc., are also used to wash scales that have not been used for a long period of time. Washing the instrument with the wash solution removes the contaminants by using the wash solution itself to react chemically with the contaminants. So need to soak for a certain chance full effect; Organic solvent is for the dirt belongs to a certain type of greasy nature, but with the help of organic solvents can dissolve the role of oil, or with some organic solvents can mix with water and play fast The particularity of rinsing the instrument with water will not wash away. For example, toluene, xylene, gasoline, etc. can be washed oil stains, alcohol, **, ** can be washed just washed with water instruments.

(II) Precautions for the preparation and use of the washing liquid The washing liquid is referred to as the washing liquid, and there are various kinds of washing liquid according to different requirements. The more common types of introduction are as follows.
1. Strong Acid Oxidant Lotion The strong acid oxidizer lotion is made up of dichromate (K2Cr2O7) and concentrated ** (H2SO4). K2Cr2O7 has strong oxidizing power in acidic solution, and it has little erosion effect on glass instruments. Therefore, this lotion is most widely used in the laboratory.
The preparation concentrations vary from 5 to 12% in various concentrations. The preparation method is roughly the same: take a certain amount of K2Cr2O7 (industrial product can be), first dissolve it with about 1-2 times of water, and after slightly cold, add the required volume of H2SO4 for industrial product into K2Cr2O7 solution (thousands). Never add water or solution to H2SO4.) Stir with a glass rod, and be careful not to spill it out. Mix well. After the crucible cools, place it in the wash bottle. The newly formulated lotion is red-brown and has a strong oxidizing power. When the lotion turns dark green for a long time, it means that the lotion has no oxidizing power.
For example, the preparation of 12% lotion 500mL. Take 60 grams of industrial K2Cr2O7 placed in 100mL of water (the amount of water is not fixed, in order to dissolve the degree), dissolved by heating, cooling, slowly adding concentrated H2SO4340mL, while stirring After cold, bottling spare.
When using this kind of lotion, care must be taken not to splash it on the body to prevent “burning” clothes and damaging the skin. The lotion is poured into the instrument to be washed, and the instrument shall be fully immersed in the peripheral wall and then stopped for a while and then poured back into the lotion bottle. After flushing the newly-washed instrument with a small amount of water for the first time, the waste water should not be poured into the pool or the sewer. It will corrode the pool and the sewer for a long time. It should be poured into the waste liquid tank. When the tank is full, it is poured into the garbage. Waste tank, when poured into the pool, rinse with plenty of water while pouring.
2. Alkaline lotion Alkaline lotion used to wash oily equipment, use this lotion is a long time (more than 24 hours) immersion method, or immersion method. When using instruments from the alkaline wash, wear latex gloves to prevent skin burns.
Commonly used alkaline washings are: sodium carbonate solution (Na2CO3, ie soda ash), sodium bicarbonate (Na2HCO3, baking soda), sodium phosphate (Na3PO4, trisodium phosphate) solution, and disodium hydrogen phosphate (Na2HPO4) solution.
3. Alkaline **** lotion with alkaline **** for lotion, slow action, suitable for washing oily utensils. Method: Take **** (KMnO4) 4g plus a small amount of water dissolved, then add 10% sodium hydroxide (NaOH) 100mL.
4. Pure acid soda ash washing solution according to the nature of the container's dirt, directly immersing or immersing the vessel with concentrated oxalic acid (HCl) or strong ** (H2SO4), strong ** (HNO3) (temperature should not be too high, otherwise concentrated acid Volatile to stimulate people). The soda ash lotion is mostly soaked in 10% or more of concentrated caustic soda (NaOH), potassium hydroxide (KOH), or sodium carbonate (Na2CO3) liquid or in a vessel (boiled).
5. Organic solvents Containers with fatty dirt can be scrubbed or soaked with organic solvents such as gasoline, toluene, xylene, **, alcohol, ****, **, etc. However, the use of organic solvents as a lotion is a waste, large instruments that can be scrubbed with as much alkaline scrubs as possible. Only small pieces or specially shaped instruments that cannot be used with brushes are washed with organic solvents such as piston bores, pipette tips, burette tips, burette piston bores, droppers, and vials.
6. Decontamination liquids Carcinogens for the detection of carcinogenic chemicals should be soaked in decontamination liquids that destroy the carcinogenic substances before they are washed to prevent damage to the human body, and then washed.
Detergents often used in food inspection are: 1% or 5% sodium hypochlorite (NaOCL) solution, 20% HNO3 and 2% KMnO4 solution.
The 1% or 5% NaOCL solution is destructive. After immersing the contaminated glassware in a 1% NaOCl solution for half a day or immersing it in a 5% NaOCl solution for a while, the aflatoxins can be destroyed. Matching method: take 100 grams of bleach, add 500 mL of water and mix well. In addition, dissolve 80 g of Na2CO3 for industrial use in warm water 500 mL, mix the two liquids, stir, and filter after clarification. The filtrate contains NaOCL 2.5%; In powdered formulations, the weight of NaCO3 should be doubled and the resulting solution should have a concentration of about 5%. If a 1% NaOCl solution is required, the above solution may be diluted in proportion.
20% HNO3 solution and 2% KMnO4 solution have a destructive effect on benzo(a) pyrene. Glass instruments contaminated with benzo(a) pyrene can be soaked in 20% HNO3 for 24 hours. After removal, residual acid is washed off with tap water. Wash it. The latex gloves and micro syringes contaminated with benzo(a)anthracene can be soaked in 2% KMnO4 solution for 2 hours and then washed.

(c) Steps and requirements for washing glass instruments
1. Always wash the instrument with the scrubbing instrument. Wash the hands with soap first, so that the oil on the hands is attached to the instrument and the difficulty of washing is increased. If the instrument is stored for a long time with dust, rinse it with clean water first, and then use the cleaning agent to wash or wash as required. If using a decontaminating powder, brush the brush with a small amount of decontaminating powder, brush the inside and outside of the instrument all over again, and then brush while washing with water to the naked eye to see a decontamination powder, wash with tap water 3 to 6 times, and then washed with distilled water More than three times. A fine, clean glass instrument should be unsustainable. If you can still hold the water, you still need to wash it again. When rinsing with distilled water, use a flushing method and shake it thoroughly. After washing with distilled water, check with the indicator that it should be neutral.
2. The glass instrument used for trace metal analysis was soaked in a 1:1 to 1:9 HNO3 solution and then washed in a conventional manner.
3. When performing fluorescence analysis, the glass instrument should avoid the use of detergent washing (due to the fluorescent brightener contained in the detergent powder, it will bring errors to the analysis results).
4. When analyzing carcinogens, they should be properly soaked overnight and then washed in the usual way.

(d) Drying of glass instruments The instruments that should be used frequently for experiments should be washed and dried after each experiment. For different experiments, there are different requirements for drying. Generally, the beakers and conical flasks used for quantitative analysis can be used finely. However, many instruments used for food analysis are dry, and some require no water marks. The requirements are anhydrous. The drying equipment should be based on different requirements.
(1) Drying instruments that are not used for rush, etc., can be placed in a dust-free place after the distilled water is rinsed in place to control the moisture, and then naturally dried. The instrument can be placed in a shelf with wooden pegs or in a glass cabinet with a vent.
(2) Drying and washing the instrument to control the moisture, and put it in an oven for drying. The temperature of the oven is about 105-110°C for about one hour. Can also be placed in infrared drying oven drying. This method is suitable for general instruments. The weighing bottle, etc. shall be placed in a desiccator for cooling and preservation after drying. Glass and thick-walled instruments with solid glass plugs must be warmed up slowly when they are dried and the temperature must not be too high to prevent them from breaking. The gauge must not be baked in an oven.
Rigid test tubes can be heated and dried with alcohol lamps. Bake from the bottom and place the nozzle downwards to prevent the water droplets from falling back and bursting the test tube.
(3) Drying with hot (cold) air Drying can be done for instruments that are eager to dry or larger instruments that are not suitable for placement in the oven. Usually use a small amount of ethanol, ** (or ** last) poured into a controlled moisture removal instrument, and then blow with a hair dryer, start blowing with cold wind for 1 to 2 minutes, when most of the solvent volatilization after blowing in The hot air is completely dry, and then the residual steam is blown away with cold air so that it does not condense in the container again.