THMG273 – TMAH – A chemical analysis

From a recent FB post Mike caught onto this chemical and began a conversation about the oddities of it and the tactical considerations.

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  1. Tetramethylammonium hydroxide. Man that’s a mouthful. And is not something I had heard about until eguine ngai posted something about it on the hazmat group on facebook. The story that he told got me interested in the chemical. It’s found in industrial settings. Specializing in the electronics world and many research applications. While doing more research on it I found it kinda interesting in regards to how lethal this seemed vs what its hazards were listed in the GHS. So i wanted to touch on that as well
  2. Tetramethylammonium hydroxide with a cas# of 75-59-2 is often found in two different types of solutions. It is found as water or aqueous solution as well in solutions of methanol. 
    1. Do you find it odd at all that the cas number for these doesn’t change. I mean methanol and water are so different yet the same cas#?
      1. Talk about that
    2. They are found in concentrations of about 2 to 25%
    3. Besides being in solution a salt form of TMAH exists and can be found in crystallized form. So you might see them like you would a salt
  3. So we were curious just exactly what this stuff does. Like what would one use Tetramethylammonium hydroxide for anyway. And let me tell you the answer to that question left me with more questions than answers. It performs action that i have never even heard of on things i have neer even heard of
    1. this is from wikipedia One of the industrial uses of TMAH is for the anisotropic etching of silicon.[10] 
      1. What is anisotropic?
        1. I am glad you asked because I didn’t have a clue either. It basically makes the surface of a substance different depending on its orientation. When i looked this up because i still didn’t understand what the hell that meant, it gave an example of wood. A log has different characteristics going with the grain then against the grain. It’s easier to chop wood with the grain but hard to break it apart against the grain.
      2. It is used as a basic solvent in the development of acidic photoresist in the photolithography process, and is highly effective in stripping photoresist. TMAH has some phase transfer catalyst properties, and is used as a surfactant in the synthesis of ferrofluid, to inhibit nanoparticle aggregation.
    2. TMAH is the most common reagent currently used in thermochemolysis, an analytical technique involving both pyrolysis and chemical derivatization of the analyte.[11
  4. Let’s take a look at some of the chemical and physical properties of this chemical.
    1. First off it is a very strong base.
      1. When we examine some of the accidents a bit we will see that skin damage and tissue damage was a huge issue.
    2. In a solid form it has a melting point of 153 degrees and will decompose before that liquid boils. 
    3. It has an auto ignition temperature of 878 degree F. So it is clearly toxic long before it will be flammable
    4. It has no available data on the vapor pressure. 
  5. What are some of the hazards of this?
    1. Under the GHS its is 
      1. acute toxicity oral and dermal
      2. Skin corrosive and eye damage
      3. Will have specific target organ toxicity in a single exposure to the central nervous system and with repeated exposure will target thymus gland and liver
    2. The NFPA labels this a 3 in the health hazard. 
  6. Lucky eugene ngai put together a few case study accidents on this chemical. And reading and hearing about them really gives you a pretty deep respect for the chemical. This comes from mEguines company “chemically speaking LLC” and you can find this and all sorts of other info on chemicals on his site.
    1. The first one speaks of a more recent event.
    2. The following is based on news articles and was not confirmed with LG Display: On Jan 12, 2021, piping work was being conducted in the 8th or 5th floor cleanroom at the LG Display  factory in Paju, Gyeonggi-do when a piping connection leaked Tetramethylammonium Hydroxide  (TMAH). The leak occurred at approximately 2 PM and lasted 20 minutes spilling 300-400 liters. This  caused serious respiratory injuries to three employees in the cleanroom. Two were reported to have  gone into cardiac arrest and to have been resuscitated by CPR. This could not be confirmed and may  have been shortness of breath/panic. They appeared to be ok at the hospital. In addition, three in-house  emergency medical personnel were injured with respiratory injuries while rescuing the employees. 
    3. A second case study.

a worker was alone and was splashed with a 25% solution. He immediately went to the safety shower. He was found 15 minutes later barely conscious. Prior to arrival at the hospital he went into cardiac arrest. He was resuscitated but he slipped into a coma and died 8 days later.

High concentration (25%) exposure of 7% of the body is fatal! Even lower concentration can also be

Park et al., J Occup Health, 2013

  • 39 yr old male splashed 8.75% TMAH on his hands, arms and legs
  • 12% body surface area affected
  • Continued working and went to the shower room 25 mins after the spill
  • He was found dead outside the shower ~60 mins later
  • Second degree burns on skin
  2. So what are some conclusions we can draw from this.
    1. The effects of the base work very very rapidly. We usually think of bases as being something that burns over time and is not immediately felt. But in this case it seems to have been. 
      1. And the fact that there were cases that the person had instant access to a shower and that wasn’t enough.
    2. While inhalation will cause severe damage or death it seems that dermal contact is much more severe. And without being able to find a reliable vapor pressure do we lean to a level A right of the bat?
      1. There have been reports of death within 1 min of exposure via the skin. As we sayed before decon after contamination seems to not be effective
      2. In Fact it is recommended to get into a shower within 10 seconds of exposure. While that may be doable to a lab rat or someone who is working next to an emergency shower it’s not going to be possible for us as first responders.
    3. While some of the signs and symptoms of exposure may look like nerve agent exposure atropine has not shown to make any difference in the out come.

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