Health and Safety Considerations with Cleaning Agents

Question:
What are health and safety considerations when selecting and using a cleaning agent?

Answer:
Human health and safety considerations include detergent toxicity, corrosivity, reactivity, and flammability. These considerations can be evaluated by reviewing a Material Safety Data Sheet for the solvent, chemical, or detergent with which you intend to clean. The detergent(s) you choose for your application preferably should:

• be formulated to minimize health-safety concerns while still offering outstanding cleaning performance
• not contain any hazardous ingredients listed on the OSHA standard and Hazardous Substance List 29CFR1910 subpart Z
• not have flash points or stability hazards.

Many detergents strong enough to remove fingerprints can remove oils from skin and, therefore, have the potential to dry out skin and cause "dishpan hands." This is especially true of detergents designed for machine spray washing which, in order to perform in the limited contact time afforded during spray cleaning, are considered to be aggressive cleaners.

Protective neoprene, butyl, rubber, or vinyl gloves are recommended for any extensive manual cleaning operation. In addition, many detergents are potential eye irritants, and should not be used without eye protection.

Alconox, Inc has downloadable MSDS at www.alconox.com for each brand of cleaner.

Aqueous Cleaning Consideration Questions

Question:
What are important questions to consider when selecting an aqueous cleaner?

Answer:
Today's aqueous critical-cleaning detergents are blended for specific applications-substrate, degree of soil load, and cleaning process-these, are all important considerations when selecting a detergent. Here are a few questions to ask about a detergent brand to ensure that it meets your specific cleaning needs:

1. Does it have good detergency on the types of soils that you need to remove? A broad range of organic and inorganic soils are readily removed by mild-alkaline cleaners that contain a blend of surfactants and sequestering agents. Metallic and inorganic soils are often readily solubilized by acid cleaners. Proteinaceous soils are effectively digested by protease enzyme cleaners.

2. Is it free-rinsing? Will it rinse away without leaving interfering detergent residue? A properly formulated detergent will contain rinse aids to help the rinse water remove the detergent and soil solution. Rinsing is a critical part of high-performance cleaning. The detergent usually loosens all the soil from the surface and then the rinse water sweeps it away. Use a non depositing nonionic rinse aid. Many rinse aids are cationic positively charged compounds that are attracted to a surfaces that repel the water, this can leave a surface covered with the water repelling rinse aid.

3. Is the detergent recommended for the desired cleaning method? Use low foam cleaners for high agitation cleaning (pressure spray wash, dishwasher, etc. ). Use high foam cleaners for immersion or soaking (manual, ultrasonic, etc.).

4. How hazardous is it? For example, is it highly alkaline or acidic, presenting a personal health hazard? Is it corrosive? Does it present a reactivity hazard with soils? Is it a flammable or volatile solvent? These considerations can be evaluated by reviewing a Material Safety Data Sheet for the agent. Preferably, it should not contain any hazardous ingredients listed on the OSHA standard and Hazardous Substance List 29CFR 1910 subpart Z.

5. Can it be disposed of easily? Any detergent chosen should be readily disposable and biodegradable, containing no RCRA Hazard Classification or EPA Priority.

6. Is it environmentally friendly? Considerations include ozone depletion potential and volatile organic compound (VOC) content regulated by the Clean Air Act Amendments. Approval under anticipated future restrictions should be weighed as well.

7. How economical is it? The detergent should be widely available and affordable. For optimal economy, a concentrated detergent is typically used at 1:100 dilutions.
In choosing an appropriate detergent, one must consider the equipment being cleaned, the cleaning method, the degree of cleanliness and residue removal that are necessary and the performance of the detergent. Key questions to ask about selecting a cleaner are:

- Does it have fillers? There are a number of ways to tell whether the powder or liquid brand you're considering contains excess fillers or is optimally concentrated.

- What are the ingredients?

Powders: When selecting a powdered brand, look at the label, technical bulletins, and MSDS to see if it contains any sodium chloride or sodium sulfate compounds which do not perform a useful cleaning function but merely add to volume and weight (and shipping costs).

Liquids: With liquid detergents, the most common filler is water. It is important, however, that no more water is used than necessary to ensure a good solution, maintain stability, and prolong shelf life.

- What is the concentration?
Powders: It is rare that a detergent will require more than a 1 percent solution of detergent to water (1:100) for good detergency. For long bath life, in some cases higher concentrations up to 3 or 4 percent are acceptable.

Liquids: Typically, an alkaline cleaner will not require a dilution greater than one percent (1:100). Whereas, a semi aqueous or solvent-containing cleaner may require a dilution of two percent (2:100) or more. Again, for long bath life, higher concentrations are acceptable.

- What are the operating costs? Operating costs for aqueous cleaners are generally low since these cleaners are usually concentrated-typically using only one to five percent of cleaner solution to water. In addition, aqueous cleaning baths last a relatively long time without recycling.

Strong acid cleaners generally require constant system maintenance since their aggressive chemistry can attack tank walls, pump components, and other system parts as well as the materials to be cleaned. (Inhibitors can be used to reduce such attack.) Another disadvantage of strong acid cleaners stems from soil loading-particularly metal loading-which requires frequent decanting and bath dumping, leading to relatively high operating costs compared with alkaline cleaners.
In contrast, alkaline cleaners are often more economical compared to acid chemistries, because they do not cause excessive maintenance problems.

Cleaning Semiconductors

Question:
Which cleaner is best for removing alcohol and other outgassing residue from storage of semiconductors and related high purity components in plastic bags?

Answer:
Semiconductors and related high purity precision manufacturing components are sometimes stored in bags during processing. Those bags can sometimes have plasticizers, plasticizer residues, or residues of cleaners used to clean the bags. To remove those residues you need either a good high emulsifying cleaner or a good solvating cleaner. For immersion cleaning, it is more efficient to use an emulsifying cleaner if that cleaner is compatible with your semiconductor substrate. Many emulsifying cleaners contain metal salts, particularly sodium salts that would be incompatible with many silicon semiconductors. If you are cleaning less sodium sensitive semiconductors then you can use a high emulsifying cleaner like Liquinox to remove organic residues such as alcohols and alcohol derivatives such as cleaner or plasticizer residues from plastic bags. Typically you might ues a warm 1% solution of Liquinox in a soak or ultrasonic tank. If you cannot tolerate sodium residues, then you would use a cleaner that relies on solvation like Detergent 8. Detergent 8 does not contain sodium. Of course since solvation is a less efficient process than emulsifying, you have to use higher concentrations of Detergent 8 to achieve cleaning. Typically you would use a 3-5% concentration of Detergent 8 to soak or ultrasonic clean with.

Aquatic Toxicity

Question:
What is the aquatic toxicity of the surfactant in Liquinox?

Answer:
In order to evaluate proper disposal in compliance with some local regulations, you sometimes need to know the aquatic toxicity of detergents that you might wish to dispose of in to a locally regulated sewerage treatment plant. Liquinox, Alconox, Tergazyme, Citranox, and Alcotabs all contain roughly 5-20% sodium dodecylbenzene sulfonate surfactant. The aquatic toxicity for sodium dodecylbenzene sulfonate for Phoxinus phoxinus minnow is an LC50 of 5,633 ug/L (lethal concentration for 50% of the population). Using this information, knowing how much detergent you plan to discharge you can determine the concentration of surfactant and what the contribution to aquatic toxicity from the surfactant will be and if it meets the local discharge limits. Typically with normal amounts of detergent discharge, you will find that it is acceptable to discharge the detergent in accordance with your local regulations.

Total Organic Carbon

Question:
How much Total Organic Carbon (TOC) is in Alcojet and Citrajet?

Answer:
Alcojet contains 1.5% (w/w) Total Organic Carbon. This means that in 100 g of Alcojet there is 1.5 grams of TOC. In terms of concentration, this means that a 1% solution of Alcojet (10 g Alcojet/L) would contain 0.15 g TOC/L (10 g Alcojet * 0.015 g TOC/g Alcojet). Note that there is substantial IC content in Alcojet (just roughly estimating in my head without calculating precicely, there is around 10% IC in Alcojet). This means you must adequately acidify the sample to drive off the IC to avoid IC interference in your TOC reading.

Citrajet contains 14% (w/w) Total Organic Carbon (and no inorganic carbon). This means that 100 g of Citrajet contains 14 g of TOC. In terms of concentration this means that a 1% solution of Citrajet (10 g Citrajet/L) contains 1.4 g TOC/L (10 g Citrajet * 0.14 g TOC/g Citrajet).

You can derive any concentration information regarding TOC in Alcojet and Citrajet from the relationships given in these examples of how to do the calculation.

In the Alconox, Inc Cleaning Validation References it states:
Total Organic Carbon (TOC) analysis has been reported to detect the organic surfactants present in ALCONOX®(11% w/w), LIQUI-NOX®(21% w/w), (TERG-A-ZYME® 11% w/w), ALCOJET®(1.5% w/w), ALCOTABS®(20% w/w), DETERGENT 8®(38% w/w), LUMINOXtm(26% w/w) CITRANOX®(17% w/w) and CITRAJET® (14% w/w). You must go through the acid neutralization step or use the inorganic carbon channel on the TOC analyzer to account for inorganic carbon.

Need cleaning validation assistance? Ask the Critical Cleaning Experts at Alconox.

Detergent Last to Rinse

Question:
What does "detergent is the last to leave the equipment surface" after rinsing mean? This seems like a broad statement, can it be supported by literature/documentation?

Answer:
The only source of "detergent last to rinse" that I am aware of is based on the physical behavior of surface active agents and the interchangeable use of the word detergent and surfactant in common usage. More properly you should say the surfactant is the last to rinse. Surfactants or surface active agents are made of molecules that have one end that is hydrophilic (water loving) and the other end is hydrophobic (water hating). Surface active agents in aqueous solutions are attracted to solution surface interfaces because the hydrophobic end of the surfactant molecule is repelled from the bulk water solution while the hydrophilic end of the molecule is attracted to the water solution.

In theory the surfactant is most stable when arranged in a film. The film's structure is made up of one side where the hydrophobic tails are facing outwards towards the solution/surface interface and the hydrophilic ends of the molecules are facing inward towards the water solution. By increasing the concentration of surfactants by adding detergent to a water, a monolayer surfactant film will form in the solution until a critical micelle concentration is achieved (micelles are balls of surfactants arranged with their hydrophobic ends facing inwards and their hydrophilic ends facing outwards - micelles are responsible for emulsifying because the inner regions of micelle can hold hydrophobic oily molecules emulsified in the water solution). Cleaning is typically done with surfactant concentrations above the critical micelle concentration. As the cleaning solution is rinsed away, you drop below the critical micelle concentration of surfactant, promoting mass displacement of the micelles as well as the remaining surfactant molecules (either individual or monolayer) by rinsing. Continued rinsing further dilutes the monolayer and removal of the surfactants, thereby essentially being the last molecules from the cleaning system to rinse away.

As a practical matter with the limits of quantitation in the analytical methods used for cleaning validation studies and crude successive rinse studies, Alconox, Inc technical support has never heard of detecting different rates of rinsing among highly water soluble detergent ingredients. As a practical matter with highly water soluble detergent ingredients, all ingredients seem to rinse at the same rate in dip rinsing studies. Over 4 rinses, in the 3rd rinse all ingredients were detected, and by the 4th rinse they were all gone. Successive rinse methods were not fine enough to detect the subtle effect of the last to rinse away surfactant.

Need help selecting a cleaner for you manufacturing equipments? Ask the Critical Cleaning Experts at Alconox, Inc.

Ingredients in Alconox Brand Cleaners

Question:
In addition to surfactants, what other types of ingredients can be found in Alconox brand cleaners?

Answer:
Dispersant-This is a cleaner ingredient that helps disperse or suspend solid particles in solution. Dispersants include water-soluble surfactants or water-soluble polymers (long-chain organic molecules) that are electrostatically attracted to particulates, creating a bridge between the water and the water insoluble solid particulate (in some cases even repelling the solid surface to help lift the particles into suspension).

Emulsifiers-These cleaner ingredients help emulsify water insoluble oils into solution by helping to create a liquid-liquid mixture. Surfactants that use their hydrophobic (water-hating or repelling) or oleophilic (oil-loving) end of their molecule to mix with water-insoluble oils and their hydrophilic (water-loving) end to mix with water create a bridge to emulsify water insoluble oils into solution. The specific structure of the bridge is called a micelle that can be thought of as a hollow, oil-filled round ball with a skin made of surfactants with their hydrophilic ends facing out in contact with the water solution and the hydrophobic ends facing in to the oil-filled ball.

Wetting agents-These are surfactants that lower the surface tension of water and allow the cleaning solution to wet surfaces and penetrate into, under and around soils and surface crevices. They create a bridge between the water and any hydrophobic (water-hating or repelling) surface. You can think of a wetting agent as having one end of the molecule attracted to the surface while pulling the water solution towards the otherwise water-repelling surface, allowing the water solution to be in contact with more of the surface that needs to be cleaned. You might say that wetting agents make water wetter.

Builders-These cleaner ingredients react with interfering calcium, magnesium, or iron ions that may be present in the water solution. They stop them from reacting with soils and other detergent ingredients to form water insoluble and difficult-to-clean calcium, magnesium, or iron salts. These metals are present to varying degrees in all water, particularly tap water. Builders are usually alkaline salts, chelating agents, and/or sequestering agents.

Alkaline salt builders-These are inorganic salts such as sodium carbonate or sodium phosphates. They react with calcium, magnesium, or iron to form water soluble or water dispersible compounds that tie up the calcium, magnesium, and iron.

Chelating agents-These are negatively charged or oxygen containing molecules that react with positively charged metal ions to form a stable complex. They have multiple locations in the molecule to react with multiple positive charges that may be present on multivalent metal ions that have more than one positive charge on them. An example of a chelating agent is EDTA, ethylene diamine tetraacetic acid. EDTA has four acetic acid groups giving it a potential for four negatively charged acetates to bond with up to four positively charged sites on metal ions with multiple positive charges, such as calcium which has two (2) positive charges associated with it.

Trying to validate a pharmaceutical cleaning process, ask the Critical Cleaning Experts at Alconox.

Types of Surfactants

Question:
What are the different types of surfactants?

Answer:
Anionic surfactants - These have a negatively charged end of the molecule that gives it the hydrophilic part of the molecule. These negatively charged parts of the molecules are usually sulfonates, sulfates, or carboxylates that are usually neutralized by positively charged metal cations such as sodium or potassium. Examples include sodium alkylbenzene sulfonates, sodium stearate (a soap), and potassium alcohol sulfates. Anionic surfactants are ionic and are made up of two ions—a positively charged, usually metal, ion and a negatively charged organic ion.


Nonionic surfactants - These are surfactants that have no ions. They derive their polarity from having an oxygen--rich portion of the molecule at one end and a large organic molecule at the other end. The oxygen component is usually derived from short polymers of ethylene oxide or propylene oxide. Just as in water chemistry, the oxygen is a dense electron-rich atom that gives the entire molecule a partial net-negative charge which makes the whole molecule polar and able to participate in hydrogen bonding with water (as discussed in the first chapter). Examples of nonionic surfactants are alcohol ethoxylates, nonylphenoxy polyethylenoxy alcohols, and ethylene oxide/propylene oxide block copolymers.

Cationic surfactants - These are positively charged molecules usually derived from nitrogen compounds. They are not commonly used as cleaning agents in hard-surface cleaners because of the tendency of the cationic positively charged molecule to be attracted to hard surfaces (that usually have a netnegative charge). Many cationic surfactants have bacteriacidal or other sanitizing properties that are useful in creating disinfectants that leave a cationic disinfectant film on the surface.

Cationic surfactants are usually incompatible with anionic surfactants, because they will react with the negatively charged anionic surfactant to form an insoluble or ineffective compound.

Amphoteric surfactants - Those surfactants that change their charge with pH. They can be anionic, nonionic, or cationic depending on pH. Usually, any one amphoteric can be any two of the three charge states.

Need help with Cleaning Validation? Ask the Critical Cleaning Experts at Alconox.