How to Achieve the Lowest Level of Metals Digestion

The Ultimate Clean Cup is the cleanest cup on the market today.
The Ultimate Clean Cup is the cleanest cup on the market today.

Regulatory entities along with competitive markets are driving the demand for lower and lower detection levels of samples. When it comes to achieving low detection capabilities for metals testing, laboratories recognize not only the importance but also the difficulties associated with keeping a clean lab and clean testing supplies. We found that you can achieve ultra-low detection capabilities with a clean lab and the Ultimate Clean Cup metals digestion cup from Environmental Express.

To achieve and generate metals data at ultralow and trace levels (part-per-billion and part-per-trillion) you must first eliminate as much contamination as possible. The most obvious step in achieving a clean laboratory environment is to give it a deep cleaning. Dust is a major contributor of metals contamination, especially for Zinc (Zn). Mopping could be added to remove contaminants as well. It is a good idea to establish a regular cleaning schedule in your laboratory.

Next, you want to keep your sampling area and sample prep area free of contaminants. Consider a benchtop enclosure system with a high-efficiency particulate air (HEPA) filter through which air is drawn by a small fan at the top of the unit.

Once you tackle the sample areas, focus on getting rid of contamination from materials that encountered the samples. You can stop using glass throughout your sample preparation. It’s important to do this because borosilicate glass has the potential to leach silicon (Si), boron (B), and sodium (Na) as well as absorb lead (Pb) and chromium (Cr). Glassware tends to exhibit “memory” effects from previous solutions.

It is also important to use standards that have not expired and ensure your standards are certified and carry a robust Certificate of Analysis (CoA) with information on background contaminants. Use high-purity acids such as sub-boiled distilled hydrochloric and nitric acids.

A well-maintained clean deionized (DI) water system is also crucial as it is used in every aspect of the laboratory, everything from sample prep to cleaning and soaking. One option is to run your water through an initial large-scale DI system off the main water supply and then through a benchtop DI water system. Periodically test your water at various points to ensure no contamination enters your system. It’s always a good practice to change the peristaltic pump sample intake tubing every other day to prevent build-up. In addition. you can use a low-metals, pre-rinsed pump tubing which saves time because it rinses down much faster than traditional pump tubing during instrument setup. Soaking everything not in use, with a weak acid solution, is a crucial step to reducing contamination.

Don’t forget to look at your calibration process. Preparing the calibration curve requires a steady hand, patience, and precision. The more steps that can be eliminated, and the less the calibration curve is handled, the more consistency can be achieved. You can use dilutions and a balance to make your calibration curve. Consider making it daily to every other day to ensure optimal instrument calibration.

Sample preparation introduces many opportunities for contamination to occur if you are not attentive. You may want to make smaller batches of digestion solution. Depending on how many samples are prepared, a few batches may be made. Each time a new batch is made, it offers the potential for contamination.

Look at your fume hood and consider installing a HEPA filter so the air being drawn over your samples doesn’t contaminate them. It is equally important to make sure your fume hood stays clean from dust, spills, and other chemicals.

In a clean lab, safety apparel not only protects lab personnel from potential hazards in the lab but also protects the lab equipment and samples from lab personnel. Metals can be found in everything including deodorant, cosmetics, lotions, lint on clothes, and soil on shoes. It is good practice to wear lab coats, safety glasses, pull free-flowing hair back, and remove as much jewelry as possible.

As in any lab, and especially a clean lab, gloves are imperative. Using vinyl gloves instead of powder-free nitrile gloves provides a cleaner handling. Another practice to aid in cleanliness is to wash gloves with deionized water once the gloves are placed over your hands and before use to greatly decrease contamination.

Whenever possible, do not run other tests in the same vicinity of your clean lab. These tests may produce fumes, leave a residue, create ash, etc., that could cause contamination. Another practice that may benefit a clean lab is the separation of making standards and prepping samples either in different hoods or different areas. This creates an environment where cross-contamination from splashes, spills, or mishandling is less likely.

The need and capability in achieving trace and ultratrace detection levels drive a demand for contaminant-free products to run these tests. It only made sense to use the Environmental Express Ultimate Clean Cup. These 50 mL digestion cups are specifically designed for trace metals analysis and carry the most robust certification on the market today. The Ultimate Clean Cup is certified for 68 elements at part-per-billion and part-per-trillion levels. The moment each cup comes off the mold, it is carefully handled to avoid common means of contamination. Specially-designed packaging ensures the Ultimate Clean Cup arrives ready to use in any clean environment.

Proper training is essential for lab personnel performing low metals analysis, as well as those working in a clean lab environment. Not only is it necessary to understand what the best practices are but also the reasoning and repercussions behind those practices. Contaminant-free products will not benefit a lab if clean lab procedures and techniques aren’t followed. When you have a new lab employee, it’s a good idea to start them in the prep role to learn the basics. Fundamentals are key and the data produced can only be as good as your preparation. Ultimately, each individual lab needs to develop its own system of best practices and develop standard operating procedures to fit its clean lab needs.

If you want to talk to an expert about any challenges you may have with your clean lab needs, call our technical experts at 1-800-323-4340.

1 Comment on "How to Achieve the Lowest Level of Metals Digestion"

  1. locks Elisabeth | August 11, 2017 at 5:35 am | Reply

    WOW !!! great 

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