Questions & Answers from the live event
Are ultra-trace grade acids worth their expensive cost for elemental analysis?
It depends on your analysis. For scoping work or method development, when you are not concerned with some contamination, you can use lower cost acids. Trace-level analyses, however, requires ultra-trace grade acids to make sure the acid is not contributing excessive elemental interference.
Why should I be concerned with common contamination if they are not my target elements?
Most target elements have interferences with combinations of gases and other elements, so there are contaminating elements which can form polyatomic molecules and cause an interference that mimics your target. These elements are problematic, even if they are not your target.
Do laboratory cleaners add or decrease contamination? Which ones should I use?
Each cleaner has a different formulation with its own possible contamination. In general, acid and water are the best inorganic cleaners. When a cleaner is needed, pick one which clearly states it is for inorganic or ionic processes. Clean well and then rinse very well. Sometimes you may have to soak the labware with clean water or acidified water to ensure all the cleaner is removed.
What is the best way to prepare sticky samples for digestion without contamination of extra vessels and lab tools?
You can freeze sticky samples before preparation, or you can use liquid nitrogen (LN) to flash freeze samples. If you use cryogenic grinding, you have a short window to get the frozen material weighed and into the vessel. If the sample melts in the weigh boat before dispensing, a small amount of LN can be added to the weigh boat to refreeze the sample and make it solid. Just ensure the weigh boat material can withstand the LN.
Can the plastic containers and grinding media hold up to cryogenic temperatures?
If the materials are provided by Spex for cryogenic or cold sample processing, then they will easily withstand the temperatures. Other plastic materials, such as ordinary centrifuge tubes etc., can be prone to breaking or shattering since they are not intended for freezing or subfreezing temperatures.
What concentration and time, and then number of rinses do you use for your acid wash?
Any additional acid washes and rinses will help reduce potential contamination. For some work, you can use concentrated acid for a first rinse, or first digestion, then follow up with subsequent washes. The best approach is to start with the lowest amount of acid and test the rinse against a blank after set periods of time (i.e., 24 hours, 48 hours, 1 week, etc.). The composition of your final material stored in the container matters. If your solution or sample is acidic, then you will need to wash with a solution at least as acidic as your intended final sample.
Can sonicating a syringe potentially damage it?
Sonication can be used sometimes to clear a clog in a syringe but not sure if routine use would ultimately damage the syringe. If you want to use sonication as a routine method of cleaning, consider contacting the syringe manufacturer to discuss.
We currently use food processors to homogenize food samples. What would you suggest besides stainless steel blades?
If you are testing for metals, then stainless steel blades add contamination. Whether or not that matters for your sample depends on the level of testing. If you are doing heavy metals or trace metals testing, then yes, you should avoid the stainless steel, especially the material most food-grade blenders or mills use. Laboratory-grade blenders and laboratory-grade mills are designed with consideration for potential contamination and leaching whereas most food mills are not.
Is sodium element an environment contaminant?
When I try to detect arsenic at ppb concentrations, I always find sodium signal more than arsenic (10 ppb). Sodium is a ubiquitous element in both the environment, agriculture, and the laboratory. There is very little you can do to eliminate sodium from the samples themselves, but you can reduce the sodium from containers by using compatible plastic, not glass, sample containers, thus reducing sodium contamination at the bench.
How do we control contaminations if we have a very busy inorganic laboratory (many people work there)?
Establishing good laboratory practices, which include clean lab procedures and processes, is the first step. The second is to make sure everyone follows those procedures. If there are only a few critical trace processes or samples, then those can be contained in a clean box, hood, or room where ultra-trace level policies are followed.
What's the best way to dry gloves once they've been rinsed?
There are several methods for drying gloves: air drying, forced-air dryer, and paper towels with thought about possible contaminants. You can spray or squirt a small amount of methanol or IPA on the washed gloves to help evaporate the water.
What solution do you use to clean high-density polyethylene (HDPE) bottles to avoid possible contamination before you store your working standards?
For some work, you can use concentrated acid for a first rinse, and then follow up with subsequent washes of lower acid or water. For most work, the best approach is to start with low acid and test the rinse against a blank after a period of time. The composition of your final material stored in the container matters. If your solution or sample is acidic, then you will need to wash or soak it with a solution that is, at least, as acidic as your intended final sample.
Is the presentation available? Can I get a copy of the presentation in a PowerPoint or PDF format? Can we get your viewgraphs?
You may access the webinar On-Demand at any time on the Cole-Parmer website here.
Where should you read on a disposable syringe when you want to measure a volume?
All measurements are meant to be taken from the lowest point of the meniscus or plunger. Most of us take measurements from the most visible point along the wall of the syringe.
Any recommendation on acid cleaning PES filters vs. not cleaning them due to low residence time and possibilities of contamination during cleaning?
Any cleaning process can potentially add contamination. The best policy is always to track or monitor contamination against blanks and compare if the cleaning added or subtracted from the background.
We have experience clogging when sample type was clear solution and had sugars. I feel this could have resulted in clogging after testing for a few days. Is this hypothesis reasonable. How can we avoid clogging?
Without knowing your sample preparation and analysis procedure, it is hard to tell if that could be the issue. If your sample is acid digested, then the sugars should have been broken down before testing. If your sample is high in silicates, then the solid silicates, which resist digestion without HF acid, could be causing clogging. If you are sampling without digestion, then yes, the sugars can be clogging the system. However, you should be sampling without prep to an ICP/MS system. You can sample organic samples to an ICP but often need to change the nebulizer to an organic nebulizer and change the settings.
Regarding W.R.T. contamination, any suggestion on how to clean bottles. Can we wash glassware using a washing machine?
Residential dishwashers are not recommended for laboratories. Laboratory dishwashers often have pipes and tubes to ensure the labware is cleaned on the inside and outside. The type of cleaner will depend on the elements of concern. At Spex, we sell a pipette washer/dryer to clean reusable pipettes with DI water. This greatly cleans the pipettes to near undetectable contamination. Any system using DI water, and a method to repeatedly rinse each bottle or vessel over multiple cycles, will help reduce contamination.
I perform dilution of my rare earth-based solution samples with utmost care, but my results vary each time I do MPAES test analysis. I am not able to figure out the problem. Could you please help me?
MPAES runs on air rather than other combustible gases. If you are using an air purifier and generator, then it is possible those could be the source of variability, if the system is not clean or maintained. If the signal bounces around between each analysis, then start with looking at the AES system including the air, the autosampler, the torch, etc. Do you see the variation on other samples? If so, then check the autosampler and replace the tubing. If you see more variation over time or between testing batches, then it may be laboratory issues or contamination.
How are Antylia Scientific™ gloves, both nitrile and latex, superior to other general brands?
The study of gloves did not include brands, and I am unaware of any data comparing the quality of the latex or nitrile gloves.
