Heavy metals testing is used to substantiate environmental safety; metals are not naturally bio-transformed and continue to persist in our surroundings. As heavy metal toxicity is associated with several health risks, there are regulatory limits placed on their presence in soil, water, food, and feed.
If you work in an environmental testing facility or utilise these services, you must be aware of the challenges faced when conducting metals testing in environmental samples. Sub-par and inconsistent processing can often cause confusion, frustration and delays to your important projects.
Cole-Parmer has developed a range of innovative tools that can be leveraged for clean and safe metals digestion. Automate parts of your workflow, save time and obtain accurate metals detection data.
David Smith – Technical Director, Environmental Express
David holds a Bachelor of Science degree in Chemistry from the University of South Carolina. He worked in a commercial environmental lab in Columbia, South Carolina for 8 years. He has been with Environmental Express/Cole-Parmer for the last 9 years. His primary roles include helping others with proper utilization of their equipment, method training, and working with product development. He has volunteered with the Standard Methods Committee since 2008.
Nassima Galloway – EMEA Category Manager, Environmental Express
Nassima Galloway holds a Bsc in Biochemistry from the University of Manchester. She began her career working with Phenomenex and gained a lot of knowledge in HPLC/GC analytical chemistry. From then she worked with Kinesis/Cole Parmer for 6 years and worked very closely with environmental testing laboratories in the UK and EMEA.
Is HPS ISO 17034 certified?
Yes, HPS is ISO 9001, ISO 17025, and ISO 17034 certified.
How have the ILAC standards affected the current lab methodology since its inception?
The ILAC standards are generally always striving to achieve lower levels of detection limits for the ICPMS/OES. Of course, ICPMS/OES instruments have improved a lot since then but you can also improve this by optimizing the digestion stage to make sure that all metals are fully extracted out of the sample. By working toward accurate results (minimizing contamination) and running multiple samples in series on a HotBlock unit this can help improve data quality.
Regarding the filling station, can you add different volumes to different vials?
The unit is designed to have all samples on the block be processed from one digestion method. All samples will receive the same reagents and volume.
Did you say that the watch glasses and the reflux caps can be washed and reused? You said the reflux caps work the same way as the watch glasses?
The watch glasses and reflux caps are intended to be single-use items. This prevents any possible cross- contamination or carryover between samples.
Could I get a copy of the slide with the glove comparisons?
The chart below shows a comparison of the trace amounts of various metals found on gloves compared to when the gloves were rinsed with deionized water.
Do the Ultimate Clean cups come in 15-mL size?
No, the Ultimate Clean cups are only available in the 50-mL version.
Why is microwave digestion not considered with new CEM? i.e. you can have programmed run and safer than open HotBlock?
A microwave system is a valid method for digesting samples. It fits very well in certain situations depending on desired sample throughput, available bench space, and budget. Cole-Parmer does not have a microwave system to offer at this time and we did not have data that we have validated to present for comparison.
What do you suggest drying your gloves with after rinsing with DI water?
The gloves can be rinsed in large batches prior to use and then allowed to dry in a particulate-free environment. When rinsing while being worn, air drying is a good option. Be sure to avoid any cloth towels or paper towels that may cause lint.
We are performing metals digestion using EPA 3050B I believe. The method calls for a 2-hour digestion in nitric and 2-hour in peroxide. Not sure how it was validated here but those times have been cut to 30 minutes and I am observing low bias general. To complete my question, do you have any comments on the approximately 25% digestion period when dealing with typical soils and reference soil standards?
The relevant instructions from 3050B are as follows – “For the digestion of samples for analysis by GFAA or ICP-MS, add 10 mL of 1:1 HNO3, mix the slurry, and cover with a watch glass or vapor recovery device. Heat the sample to 95°C ± 5°C and reflux for 10 to 15 minutes without boiling. Allow the sample to cool, add 5 mL of concentrated HNO3, replace the cover, and reflux for 30 minutes. If brown fumes are generated, indicating oxidation of the sample by HNO3, repeat this step (addition of 5 mL of conc. HNO3) over and over until no brown fumes are given off by the sample indicating the complete reaction with HNO3. Using a ribbed watch glass or vapor recovery system, either allow the solution to evaporate to approximately 5 mL without boiling or heat at 95°C ± 5°C without boiling for two hours. Maintain a covering of solution over the bottom of the vessel at all times.”
The method does call for an initial observance of the sample for 30 minutes to verify no further reaction with the nitric acid. This probably got combined with the next step of digesting for two hours by mistake. We recommend following the method as written to achieve accurate results.
Do you have acid or solvent permeation data on the vinyl gloves?
The manufacturer does not have any data of this sort available that I could find. We can only refer them to the chemical compatibility database that lists PVC (the glove material) as having “Good Compatibility” with both HCL and HNO3 with only mild discoloring.
Are there any suggestions with samples with residual solvents? Such as oil extractions from hemp plants.
We would need to review the specific solvents in use and the method of extraction. Please contact our technical team at firstname.lastname@example.org.
I have a question on filling station... what type of pump does the Environmental Express ABF5000 need? Is the pump included in the instrument or should one be purchased separately?
The unit comes with a peristaltic pump built into it. We use a Masterflex L/S® Easy-Load® Head.
We are using micro pipettors to add acid and to make reagent water. Do we need to use 25-mL etc. HNO3 or HCL to make it use plastic or glass volumetric pipettes?
I prefer repeat pipettors for large amounts of repetitive volume additions as they allow greater speed with acceptable precision and accuracy. For just a few samples or when exact amounts are required, glass pipettes offer the most accurate dispensing at the cost of speed.
You mentioned recycling. Are all those disposable products #2 plastic?
All the digestion cups and filtering products are polypropylene. That carries #5 designation on the recycling charts.
In the presentation, David talked about using plastic cups instead of glass cups since plastic has less chance of metals since glass has some metals in there. Does this concept transfer to using plastic pipettes vs volumetric pipettes?
With pipettes there is less chance of glass being a contributing source since it is not subject to the digestion procedure. For routine analyses either one can be used if they provide the speed and accuracy you need. Be aware that borosilicate glass will often give measurable background amounts of boron, silicon, sodium, potassium and aluminum.
Is it feasible to digest and analyze metals within air particulates (pg to ng of metals) at a well-cleaned station or would this analysis require a cleanroom?
Very good question. In order to achieve optimal results, the best practice for this level of detection is to work in an environment which is specifically for environmental and clinical trace element applications. The more traditional cleanrooms that you see in semi-conductor fans, the pharmaceutical industry, NASA, etc., are not ideal due to the prevalence of metal in the finishes and hoods. Though the general environment of your clean lab is suitable for trace work, it is always best practice to perform the most critical steps within Class 100 polypropylene clean "hoods" (actually HEPA-filtered all polypropylene biosafety cabinets) so that you can work "cleanly" with acids.
Do you have a published method for using the HotBlock unit?
Our HotBlock manual can be downloaded from http://www.envexp.com/product-manuals. Select “HotBlock Manual 10.2018.pdf” for the most current version.
If we have missed any questions, or if you have more questions please contact us at Environmental Express.