When conducting trace analysis, contamination during sample preparation is a critical concern. Contaminants can arise from multiple sources—whether it’s the environment, the reagents, the apparatus, or even the analysts themselves. For many trace analyses, the blank used often determines the lower limit of detection, which highlights the importance of minimizing contamination.

Environmental contamination, particularly in an analytical laboratory, is a key source of error. Studies have shown that air in labs can contain up to 200 µg/m³ of particulate matter, containing elements like Ca, Si, Fe, Na, Mg, and others. Additionally, rural areas may have around 1,400,000 airborne particles/m³ greater than 0.5 µm, while urban areas could reach an alarming 53,000,000 particles/m³. This abundance of airborne contaminants presents challenges in maintaining the integrity of trace analysis samples, making contamination control paramount.

Reducing Environmental Contamination

One of the most effective strategies for combating contamination is to use the chemical blank as a performance benchmark. Reducing the blank to the lowest possible value by minimizing contamination is crucial. Achieving this goal requires eliminating contamination from sources such as sample containers, the chemist, and sample preparation apparatus. Here are some key strategies for controlling environmental contamination:

1. Separate Sample Preparation Areas
   Isolate the sample preparation and handling area from other parts of the laboratory to minimize exposure to contaminants. This prevents cross-contamination from other lab activities.
2. Minimize Foreign Objects
   Remove as many foreign objects as possible from the preparation area. Motorized objects likestirring platescould introduce particles into the air and increase contamination risk.
3. Use All-Plastic Hoods
   While hoods are necessary for analyst safety, they often enhance atmospheric exposure, leading to contamination risks. All-plastic hoods can help mitigate this, as plastic surfaces tend to reduce contamination compared to metal.
4. Limit Sample Exposure
   Keep the sample out of the hood area as much as possible, limiting its exposure to environmental contaminants during the preparation process.

One effective solution to reducing contamination in modern laboratories is the use of clean rooms equipped with HEPA (High Efficiency Particulate Air) filters, which are 99.99% efficient at removing particulates down to 0.3 µm. This technology has significantly reduced atmospheric contamination, making it an essential feature for trace analysis labs.

Avoiding Environmental Contamination

Beyond reducing contamination, it’s crucial to adopt practices that help avoid contamination altogether. Here are some recommendations for maintaining a contaminant-free laboratory environment:

1. Teflon or Epoxy Coatings
   Coat any metal objects in the laboratory with Teflon or epoxy paint. This minimizes their potential to corrode and release particles into the environment. Likewise, epoxy paint the walls and clean them weekly to prevent buildup of dust or contaminants.
2. Adhesive Floor Pads
   Use special adhesive floor pads at the entrances of the laboratory. These pads help trap particles from shoes and other sources, preventing them from entering the lab.
3. Disposable Gloves and Lab Coats
   Equip laboratory personnel with disposable plastic gloves and disposable paper lab coats to prevent contamination from human contact.
4. Daily Floor Cleaning
   Floors, especially vinyl-covered, should be mopped daily to remove particulates that may settle on the ground. Laboratories with floor drains make this process easier, allowing for daily washing to reduce contamination.

Minimizing and avoiding environmental contamination is critical for the accuracy and reliability of trace analysis. By implementing these rigorous contamination control strategies, you can ensure the integrity of your samples and achieve more accurate results. Whether it’s separating sample preparation areas, using HEPA-filtered clean rooms, or adopting daily cleaning practices, these methods help maintain a cleaner environment, allowing for more reliable and sensitive analysis. In the world of trace analysis, controlling contamination is not just a best practice—it’s essential to scientific success.