Inorganic bactericides

The antibacterial effect of metal ions and especially silver, copper and zinc ions is well known. Silver and silver ions are used in medicinal treatments ranging from severe burns to Legionnaires Diseases. Silver-based products are also applied in water purification processes. Metal ions achieve their antibacterial effect by two mechanisms First the metal ions influence the electrochemical potential between the internal and external parts of the cell, and second, after penetration of ions into the cell, they compete with other essential ions like magnesium, calcium and potassium and they aggregate with thiol groups of enzymes and proteins. 

In material protection, silver based biocides are used mainly for the preservation of consumer products like household articles, textile products and pvc floors. The preservation of liquid products with silver-based ingredients is possible with systems which allow controlled release of silver ions. A controlled release systems is necessary, because, if the silver concentration in the liquid phase is to low, microorganisms will grow, but, if the silver concentration is to high, the product will get black. Therefore different releasing systems based on zeolithe or titanium dioxide carriers or on polymers have been developed. 

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Tin is anther ancient metal that continues to have a variety of uses. The inorganic form is used in food packaging, solder, brass, and as an alloy with other metals. The organic forms of tin, triethyltin and trimethyltin, are used as fungicides, bactericides, and generally as antifouling agents for boats. 

Inorganic silver salts are strongly bactericidal. Silver nitrate, 1 1000, has been most commonly used, particularly as a preventive for gonococcal ophthalmitis in newborns. Antibiotic ointments have replaced silver nitrate for this indication. Silver sulfadiazine slowly releases silver and is used to suppress bacterial growth in burn wounds (see Chapter 46 Sulfonamides, Trimethoprim, Quinolones). 

Many other household products can be analysed in similar ways to those described above for chemicals. Household bleach is essentially an inorganic chemical. There has been concern expressed about mercury levels in hypochlorite bleach because of the way it is manufactured. The cold vapour reduction/aeration method referred to above is a good way of determining low mercury levels with minimal matrix problems [82]. In the past organo-mercurial compounds have been used (e.g. as bactericides) in some household products these may be selectively determined by extraction with an organic solvent (e.g. carbon tetrachloride or benzene), and then application of the cold-vapour method following the addition of cysteine acetate, or by coupled gas chromatography/atomic absorption [83],... 

Batch times can range from 12 to 22 hours depending on the desired final concentration and the required number of diafiltration volumes. At the end of a batch run, membranes are chemically cleaned. Cleaning may take up to 3 hours and involve the use of an alkaline or acidic solution, or both, with a final sanitization step (e.g., 200 ppm NaOCI solution, a dilute solution of sodium bisulphite or a bactericide/fungicide). In some cases, steam sterilization may be performed at the end of each run especially when using inorganic membrane filters. 

Organomercurials - particularly the alkyl- and arylmercury compounds - are more active as bactericides or fungicides than the inorganic salts. Phenylmercury acetate prevents the growth of a variety of fungi in vitro at concentrations of approximately 0.125 mg L whereas ethylmercury salts are active at 0.05 mg In contrast, mercuric acetate or chloride are active at 1.0 mg L . The difference may partly be attributed to lipid solubility, where penetra-... 

Among disinfectants, such as inorganic chloramines, chlorine and chlorine dioxide, the latest is the most efficient disinfectant for bacteria, having both the lowest effective dose and the shortest contact time [16], but human health problems can arise with its use [31]. Increasing pH increases the bactericidal activity of chlorine dioxide [32]. However, at higher pH values (> 7.0) chlorine becomes less effective because hypochlorite ions are formed. Increased pH levels (> 7.5) also convert dichloramines to monochloramines which are less bactericidal [16]. On the other hand, monochloramines are more efficient viricides than dichloramines [33]. 

Kwak SY, Kim SH, and Kim SS, Hybrid organic/inorganic reverse osmosis (RO) membrane for bactericidal antifouling. 1. Preparation and characterization of TiOj nanoparticles self-assembled aromatic polyamide thin-film composite (TFC) membrane, Environmental Science and Technology 2001, 35, 2388-2394. 

A whole range of inorganic and organic bases can be used to adjust the pH of NR field latex. However, ammonia remains the most common and the cheapest option and hence is widely used. Additional preservatives are sometimes used to further boost the stability of NR latex concentrates. Very often they function as bactericides, enzyme inhibitors, sequestering agents or stabilizers and are often used in combination. Some early preservative systems that were discontinued mainly because of safety and health hazard concerns are 0.2% sodium penta-chlorophenate and 0.2% ammonia 0.1% sodium pentachlorophenate and 0.1% ethylenediaminetetraacetic acid (EDTA) and 0.1% ammonia 0.2% zinc di-ethyldithiocarbamate (ZDTC) and 0.2% ammonia 0.2% boric acid, 0.05% ammonium laurate and 0.2% ammonia. 

Chlorhexidine possesses marked bactericidal action against a wide range of micro-organisms. The base has a low aqueous solubility (0.008 % w/v) a wide range of salts have been prepared and their solubilities measured (Table 6.8). The dihydrochloride has a solubility of 0.06%, the diacetate 1.8% and as the gluconate has a solubility > 70 % there would appear to be little need for the preparation of solubilized formulations. However, surfactants may be present in chlorhexidine formulations because of the low solubility of chlorhexidine sulphate and related salts with inorganic ions present in water, extemporaneously prepared solutions diluted from concentrates may precipitate. Non-ionic and... 

A. Simchi, E. Tamjid, F. Pishbin and A.R. Boccacdni, Recent progress in inorganic and composite coatings with bactericidal capability for orthopaedic applications. Nanomedicine Nanotechjwl. Biol. Med. 7 22-39, 2011. 

In water flooding, the same types of inhibitors as described for primary production are currently used. The most effective and most frequently used are the quaternary ions of the fatty or the imidazoline types. They are also good bactericides and dispersive agents. Combination of amino-methylene phosphonate and zinc salts have been used successftdly in circulating water systems and have provided more effective protection than the inorganic phosphate-zinc salts. Organic sulfonates have recently been introduced into practice. 

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