Chemicals are often needed to maintain a sterile, clean environment in a laboratory, hospital, or cleanroom facility. However, there isn’t a specific standard as to what to use — the recommendations vary according to the situation at hand and what kind of environment is needed.
Identifying the need
In their paper “Fungal and Bacterial Spores: Contamination and Disinfection,” Jim Polarine, Carol Bartnett, and Dan Klein of STERIS Corp. in Mentor, Ohio, describe fungal and bacterial spore contamination incidents and the importance of containing these outbreaks. The report notes that “Manufacturing opportunities for fungal and bacterial spores to enter and establish a foothold in a controlled environment, discovering a spore outbreak is more a matter of when, than if.”
The offending pathogen and its source must be identified in order to determine how it may be eradicated. The best way to control spores is with a thorough cleaning and disinfection program, as well as maintaining stringent control of items and personnel entering the cleanroom.
Serving the product
The product itself also helps determine what kind of chemical or cleaning agent needs to be used. Ed Kanesgberg of BFK Solutions in Pacific Palisades, Calif., says, “We’re always addressing a product, whether we’re talking about using chemicals, whether we’re talking about using a cleanroom, whether we’re talking about using a hospital room. The ultimate purpose is to support some sort of product, whether it’s something that’s manufactured — or in the case of a hospital room, the patient is the ‘product’ in that sense. The cleanroom or the hospital room is a tool, just like a mass spectrometer or a pair of pliers.”
“I think we have to take a holistic approach and a balanced approach to achieving the right surfaces and the surface quality, the surface cleanliness, low levels of surface contamination. There really has to be a holistic approach, and that’s on the product,” adds Barbara Kanegsberg, also of BFK Solutions. “The cleanroom is in service of the product – the analytical equipment, the process equipment, it’s all in service of producing an appropriate product. Sometimes you do have to use a harsher chemical. It may not be in the cleanroom or the hospital room … but, for example, if you’re shaping objects that are going to be used for implantables, medical devices, or for surgical tools, sometimes the soils have to be removed with the appropriate chemical.”
Facilities such as hospitals and cleanrooms “can only make claims to clean what they can measure, which is about 99.9 percent or 99.99 percent — what that means is that you’ve left behind at least a mono molecular layer’s worth of material,” says Dr. Robert Baier, a distinguished professor at the University at Buffalo and head of the biomaterials program. “You will not have actually cleaned the surface of ALL debris, you will have cleaned it of MOST of the debris. And so the surface is not really clean in the sense that a physicist or a chemist would say it’s clean. So it depends on what your requirement is.”
The purity of the chemical itself will also play a role in the outcome of the cleaning process, notes Barbara Kanegsberg. “If you run a test and you don’t control the purity of the chemicals used in the laboratory tests … if you don’t have the right cleanliness and purity of the chemicals … that can be a problem for product quality. You’ll get test results that don’t mean anything. I’ve been in situations where I’ll be doing an analytical test and, because chemicals used in that test have had certain contaminants, I have gotten certain results that have been misleading. To minimize that problem, we control the purity of the chemicals. The downside is that people in labs and people who like standards may make unrealistic demands on the purity of the chemical, and it may be very difficult to determine how to reach that number, and the significance of that number may be in question.”
A second paper by Polarine and Klein, “Fungal Contamination and Disinfection,” explains that selecting a disinfectant to control fungal contamination is influenced by many factors. There is a differentiation between fungal cells and fungal spores “in terms of difficulty of kill and inactivation, as the fungal spores are more challenging to kill and inactivate.”
The paper further states that “When compared relative to other microorganisms, enveloped viruses and vegetative bacteria such as Staphylococcus and Micrococcus, which are very commonly isolated in cleanroom operations, are easily killed and inactivated by most antimicrobial chemistries, such as quaternary ammonium compounds, phenolic disinfectants, and alcohols. Gram negative bacteria such as Pseudomonas, Burkholderia cepacia, and E. coli are a bit more challenging, but nonetheless can be addressed with quaternary ammonium compounds, phenolic disinfectants, and alcohols.”
Chemicals to avoid
The type of chemical chosen for a cleaning application will vary by situation, but there are a few universal recommendations on what NOT to use.
“[My] main warning is never use silicones, because they are such enormously strong surface active materials,” says Dr. Baier. “If you have a small contaminant in one corner of a table, by the next week the entire table will be covered [along with] anything on it. It will change the surface properties of a material like silicon or germanium or anything else you may be working on. In, say, an integrated circuit fabrication facility — everything will be siliconized and nearly impossible to be removed.”
“People use [silicones] all the time as coupling agents. It’s in your dye gel, anti-gas tablets, it’s used in making beer, but it’s very useful as a coating agent itself. But it must be done in a facility that won’t otherwise be used for things that you want to be super-clean. If you’re looking for a low-energy surface, a fluorocarbon would be better in that application than silicones. But they can also leave residues, which is the hardest part.”
Another (perhaps surprising) thing to avoid is ultrapure water.
“[People] tend to think of water in the sense of ‘the purer, the better’, and there are times where pure is not necessarily better,” says Ed Kanegsberg. “When you get to that type of purity, it is trying to be both a strong acid and a strong base at the same time, and it just loves to extract ions wherever it can find them, which is why it can be very aggressive. Especially in something like optics.”
“It wants to pick up ions. So where is it going to get those ions?” Barbara Kanegsberg adds. “In part from the thing that you’re trying to wash or rinse, whatever you’re trying to do. That doesn’t mean that we should be using impure water, but it’s a matter of being mindful of what the chemical is. And water in itself, depending on the situation, can be a rather harsh chemical in terms of the quality of the surface.”
Choose your residue
The residue itself is one of the main concerns when selecting which chemical cleaning agent to use. “When we mean ‘clean,’ we mean that no organic residue is left behind,” Dr. Baier says.
Barbara Kanegsberg says that things must be looked at in a situational matter rather than a chemical matter. “There are cases where very complex materials are being processed, and in doing so viscous or heavy process fluids are being used — heavy metal working fluids, for example, at the beginning of the process. If you don’t clean very carefully and very thoroughly, perhaps with an aggressive solvent, and if you do not control the process appropriately then you can have residue that’s left on the product, and that can show up not only in the cleanroom or in the laboratory but in the hands of the ultimate customer and you don’t want to have inappropriate contamination.”
“To get a fastidious cleaning, actual cleaning, it’s almost impossible to do chemically. The best way, then, is physically, but often of course people don’t have the capability to use that physical method, so they have to depend upon chemicals and therefore depend upon a residue being left behind. So now your task becomes basically choosing your residue,” Dr. Baier remarks. “And we have faced and achieved that goal over the years using something called SADS — surface active displacement solution — [which is] a concoction of something that you spray on surfaces that displaces everything else and leaves its own residue behind; this is a desirable residue for achieving your functional goals of what comes next with that part, whether it remains clean, whether it’s coated, whether it’s going to stick to a composite resin.”
“Our concern is with critical cleaning, surface quality, surface attributes,” says Barbara Kanegsberg. “Chemistry doesn’t know that there’s a water shortage. Chemistry doesn’t really think about whether it’s going to harm the ozone layer or the employees or the neighbors. It’s a matter of us being very aware of what we need, what will do the job effectively and efficiently, and to use those chemicals in an appropriate matter. Sometimes no chemical is the right approach — it depends on the situation. We have to look at the entire process, and that means the chemical, the time of exposure to the product, the temperature, and any forces that are associated with that exposure of the chemical.”
References
- Polarine, J., C. Bartnett, and D. Klein. “Fungal and Bacterial Spores: Contamination and Disinfection.” Reprinted from Contamination Control in Healthcare Product Manufacturing. 2013.
- Kanegsberg, B., and E. Kanegsberg. “Chemicals in Cleanrooms.” Controlled Environments, April 1, 2013. http://bit.ly/24jGDFI
- Polarine, J., and D. Klein. “Fungal Contamination and Disinfection.” Reprinted from Environmental Monitoring, Vol. 5, edited by Jeanne Moldenhauer. 2011.
MaryBeth DiDonna is Editor of Controlled Environments. [email protected]; @CEMagazineUS
This article appeared in the May/June 2016 issue of Controlled Environments.
