Cleaning laboratory glassware is an essential issue in chemistry. Sometimes scientists don't realize how crucial this is for experiments. As a result, experiments fail or lead to inaccurate conclusions. When it comes to cleanliness in chemistry, there are two levels: quantitative and normal. Quantitative clean glassware is necessary for applications that require the highest precision. Meanwhile, normal clean glassware may still contain small impurities and oils, so it's used in cases where high accuracy is not required. The following document will guide you on how to clean laboratory glassware correctly.
1. General cleaning process for laboratory glassware:
Cleaning laboratory glassware
The following steps are guidelines for cleaning laboratory glassware when a single solvent isn't enough. If you need quantitatively clean glassware, these are the first steps toward achieving this. Further cleaning methods may be required for more effective results.
- Remove impurities from the glassware:
To do this, use a paper towel to wipe a small amount of ester, acetone, or another solvent. However, it is crucial to wear appropriate gloves and avoid inhaling fumes. Afterward, place the glassware into a concentrated Alconox solution or another cleaning agent and let it sit for a few minutes.
Ensure that the brush is in good condition before scrubbing! No rust, and the bristles should not be shedding! If not, replace it if necessary. - Rinse thoroughly with tap water and finally rinse with DI water:
Water will clean the glass surface if it is generally clean. If the water cannot remove all impurities, repeat the soaking and scrubbing steps. If, after a second cleaning, solid residues remain on the glass or there is a visible amount of grease on the glass, more aggressive cleaning methods must be employed. - Clean each piece of laboratory equipment individually:
Measuring flasks, beakers, Erlenmeyer flasks, burets, and pipettes should only be used for dispensing or storing typical reagents. They should be rinsed three times with a compatible solvent, followed by tap water and a final rinse with DI water. Then, dry the equipment on a rack. In some cases, you may need to be more meticulous with the method below. Additionally, Buchner funnels should be cleaned with an appropriate solvent to remove residual substances. Perform the next steps using tap water, DI water, and dry air.
2. Active cleaning methods for laboratory glassware:
Active cleaning methods
Here are two methods for cleaning laboratory glassware to remove contaminants. These are usually used when regular cleaning fails. However, these steps are often performed in parallel as each is effective in removing different types of contaminants. Care must be taken as the solutions used can be corrosive.
- Metal-containing contaminants:
In this case, immerse the glassware in a 6 M HCl solution. Be aware that this solution can cause severe burns. Laboratory staff should wear appropriate gloves. Once the solid residue has dissolved, rinse thoroughly with tap water and repeat the cleaning steps as described in the general procedure. This method will remove some organic residues, but not grease. - Organic contaminants:
If the contaminants are organic, immerse the glassware in a container with a saturated NaOH or KOH solution in ethanol or methanol. This is very dangerous because the basic solution can damage skin, and alcohol is highly flammable! Wear butyl gloves and keep sources of ignition away from the container. Ensure that the glassware is fully immersed and positioned vertically. After soaking for several minutes, carefully remove the items and rinse thoroughly. If the glassware is not quantitatively clean at this point, you may need to repeat the general cleaning steps or soak it for a longer period.
3. Cleaning laboratory glassware in special cases:
Special cleaning of laboratory glassware
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Glass bottles:
Simply wash glass bottles with an appropriate solvent and dry the exterior immediately after use. However, it's best to first soak the bottle in the solvent and gently remove any solid residue from the sample with a cotton swab.
Do not use a brush to clean this type of laboratory glassware. If this method does not work, an acidic cleaning solution (except HF) may be required. Avoid using the basic solution on glass bottles as it can etch glass surfaces. -
Glass funnels:
These can be cleaned by reversing and allowing the solvent to flow through the frit by gravity. The solvent can also be drawn through the frit under vacuum. The residue can usually be removed by soaking it in acid, followed by rinsing with water under vacuum. Since HF and basic solutions can etch glass, they should not be used on etched funnels. -
Protein contamination:
Proteins can usually be removed by scrubbing with a cleaning agent. However, sometimes protein removal is not entirely successful. In such cases, you can use stronger acidic solutions or prepare a peptidase solution. Peptidase is an enzyme that breaks down proteins. This method is slow but gentler and can be used when the contaminated items are incompatible with acids.
Some tips to keep in mind:
The key to cleaning is to do it promptly. Don’t let dirty laboratory glassware sit for too long as it becomes difficult to clean. You should also take a moment to separate glassware into high and normal levels of cleanliness. Most importantly, consider health and safety when using cleaning chemicals. Always wear protective goggles and gloves to minimize exposure to irritants, thinners, or hazardous materials.
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