Re: Quaternary ammonium salt - didecyldimethyl ammonium chloride

["Ballard, Mary" <BallardM@xxxxxx>]

Karin: You might find hospital texts on sterilization and disinfection
more useful...but after you study the texts though & think about it
awhile, you may decide it is not necessary, since you do not expect
these textiles to be in such environmental conditions again, nor do you
expect them to be handled by sick people or babies susceptible to
microbes. And also the microbes that are pathogenic for humans, are not
those necessarily pathogenic to cellulose or silk...
1) Dialkyldimethylammonium chloride is a principle ingredient on a lot
of household cleaners for non-porous surfaces and other consumer uses
(since 1949 diapers, since 1950 laundry softener). Oftentimes the alkyl
is from tallow--a stearic or oleic...A quat will have the advantages of
being independent of pH, and a lesser tendency to yellow. For
information on quat's you might find Detergents and Textile Washing:
Principles and Practice by Gunter Jakobi and Albrecht Lohr (VCH, 1987).
Cationics do sorb onto fibers--most on wool, then viscose rayon, then
cellulose acetate, then cotton, and nylon (Weatherburn & Bayley, 1952
The Sorption of Synthetic Surface Active Compounds by Textiles Fibers.
Textile research Journal 22:797-804).
2) The germicidal activity of quaternary ammonium compounds was
identified in 1915; their bactericidal potency in 1935.  Some
difficulties were encountered in assessing the antimicrobial efficacy of
quaternary ammonium compounds because cationic surfactants are, in fact,
adsorbed by glassware. Often called "quats" or "QAC's" have been found
extremely effective against Gram-positive bacteria in concentrations as
low as 0.005%, against Gram-negative bacteria, as low as 0.033%.
Although Escherichia coli and Pseudomonas aeruginosa, two Gram-negative
pathogenic bacteria, tend to be more resistant to quats, a 200 ppm rinse
(based on the weight of the laundry) of equal parts alkyldimethylbenzyl
chloride and alkyldimethylethylbenzyl chloride disinfected the fabric.
Wool blankets treated with 0.125% (on dry weight of fabric)of
cetyltrimethylammonium bromide was recommended; 0.036% owf in a ten
minute rinse reduced the general bacterial level 99.6% on woolen
blankets. Laundering with anionic surfactants, by contrast, left a third
of the bacteria in place.
Quats are not sporacidal; they are virucidal against lipophilic viruses
(adenoviruses, Herpes Simplex, influenza, and vaccinia viruses) but not
hydrophilic ones (polio, coxsackie, and other enteroviruses). Benzyl and
alkyl ammonium chlorides have been found effective fungicides for T.
interdigitale. For further information see Disinfection, Sterilization,
and Preservation, 4th ed., edited by S.S. Block. Philadelphia: Lea &
Febiger,1991 or 5th edition, 2001 and Principles and Practice of
Disinfection Preservation and Sterilisation, A.D. Russell, W.B. Hugo,
and G.A.Ayliffe (eds) London/Boston: Backwell Scientific Publications,
1982 (there's a later addition).
3)Benzalkonium chloride is also employed as a topical pre-operative
disinfectant (0.1-0.2%); cetylpyridinium chloride (0.1-0.5% solutions)
is used as an antiseptic and, in lower concentrations, prophylactically,
in face and shaving lotions. Yet, the antimicrobial efficacy of quats is
limited by the presence of organic matter (milk, serum, faeces) and of
fatty substances (nonionic with a high lipophilic component) or in the
presence of acids.
4) Robert Koch, the "father" of microbiology (author of On Disinfection)
found 100% ethanol a relatively ineffective disinfectant. However, later
(in 1903) it was found that the moisture content of the silk thread
affected the efficacy of the ethanol solution. For dried silk, 80% +
concentrations of Ethanol for various lengths of time is ineffective
against S. aureus--but for moist threads 15-30% concentrations are the
only ones ineffective...



Mary W. Ballard
Senior Textiles Conservator,
Museum Conservation Institute, Smithsonian Institution
4210 Silver Hill Road, Suitland MD 20746 U.S.A.
tel: 301-238-1210 fax: 301-238-3709 
email ballardm@xxxxxx