Preservatives mercury compounds

AppHcations of mercury include use in batteries (qv), chlorine and caustic soda manufacture (see Alkali and chlorine products), pigments (see Pigments, inorganic), light switches, electric lighting, thermostats, dental repair (see Dental materials), and preservative formulations for paints (qv) (1—3). As of the end of the twentieth century, however, increased awareness of and concern for mercury toxicity has resulted in both voluntary and regulatory reduction of mercury usage (see also Mercury compounds). 

Pharmaceuticals. A variety of mercury compounds have had pharmaceutical appHcations over the years, eg, mercury-containing diuretics and antiseptics. Whereas some mercury compounds remain available for use as antiseptics such as merbromin [129-16-8] mercuric oxide, and ammoniated mercury [10124-48-8] or as preservatives such as thimerosal [54-64-8] in dmgs and cosmetics, most have been supplanted by more effective substances. A detailed discussion of mercury-containing antiseptics is available (37). Many hospitals use mercury metal to serve as weight for keeping nasogastric tubes in place within the stomach. 

Organic mercury compounds Silver compounds Preservation or antisepsis Application to wounds Important pharmaceutical preservations Effective against Pseudomonas aeruginosa... 

Some of the chemical strategies used in weatherproofing have been applied to the preservation of cellulosics for indoor storage and display. The historical Wasa sails of 1628 were preserved by copolymerizing acrylates and styrene onto this material (36). Antimicrobial treatment of cotton goods by polymerization in situ of a urea-mercury compound with formaldehyde or immersion in a quaternary ammonium salt solution protected the fabric for up to three years storage provided it did not need to be laundered (37). 

Cathode in the electrolytic production of chlorine and caustic soda lamps arc rectifiers mercury cells switches thermometers barometers laboratory apparatus dental amalgams raw material for various mercury compounds fungicides antiseptics preservatives pharmaceuticals electrodes reagents... 

The use of mercurials in the eye can lead to a bluish-gray deposit of mercuric oxide on the eyelids, conjuncti-vae, and Descemet s layer. Phenylmercuric nitrate used in a 0.004% concentration can cause mercuria lentis. Mercurial compounds have been found in the aqueous humor, having penetrated the eye from hydrophilic-gel contact lenses preserved with thiomersal. Although it remains to be established whether deposition of mercury in the eye is clinically important, the concentrations found are similar to those reported in cases of systemic poisoning by organic mercurials (64). 

Mercury compounds continue to have numerous commercial uses. Besides its use as a preservative, mercury is used in the manufacture of many fechnical and medical instruments including blood pressure measurement devices, manometers, thermometers. 

Phenylmercuric nitrate and other phenylmercuric salts are widely used as antimicrobial preservatives in parenteral and topical pharmaceutical formulations. However, concern over the use of phenylmercuric salts in pharmaceuticals has increased as a result of greater awareness of the toxicity of mercury and other mercury compounds. This concern must, however, be balanced by the effectiveness of these materials as antimicrobial preservatives and the low concentrations in which they are employed. 

Included in the FDA Inactive Ingredients Guide (IM and ophthalmic preparations). Included in nonparenteral medicines licensed in the UK. In the UK, the use of phenylmercuric salts in cosmetics is limited to 0.003% (calculated as mercury, equivalent to approximately 0.0047% of phenylmercuric nitrate) as a preservative in shampoos and hair creams, which contain nonionic emulsifiers that would render other preservatives ineffective. Total permitted concentration, as mercury, when mixed with other mercury compounds is 0.007% (equivalent up to approximately 0.011% of phenylmercuric nitrate). Included in the Canadian List of Acceptable Non-medicinal Ingredients (ophthalmic, nasal and otic preparations only there must be no other suitable alternative preservative). 

Discontinued applications. The use of phenylmercuric acetate as a fungicide in interior latex paints was banned in 1990 (Reese 1990), and its use in exterior paint was banned in 1991 (Hefflin et al. 1993). Both of these bans were prompted because of releases of mercury vapors as the paint degraded. Alkyl mercurial compounds were used until the mid-1970s as a treatment to disinfect grain seeds. Most other agricultural applications of mercury compounds in bactericides and fungicides have been banned due to the toxicity of mercury. Mercuric nitrate was used in the production of felt hats to hydrolyze rabbit fur. The use of mercury as a wood preservative has ceased due to the use of polyurethane (Drake 1981). 

Attention must be paid also to sample preservation to avoid perturbing the distribution of mercury compounds in the sample (Horvat 1996). The preservation of aqueous samples is often accomplished using acidification. However, suspended matter must be removed prior to acidification and dimethylmercury and Hg(0) have to be removed or else conversion of these species into methylmercury and mercury(II) can occur (Horvat 1996). For solid matrices, the preservation method of choice is freezing (Bloom 1993). Freezing preserves all major mercury species indefinitely, although coagulation will occur for sediments thus making it difficult to obtain representative subsamples of the sediment for... 

Many cosmetics, paints, ointments, foods, shampoos, and medicines contain preservatives to combat biological degradation. Toxic chemicals used as preservatives include mercury compounds, formaldehyde, methyl and propyl p-aminobenzoic acids, butylated hydroxyanisol, butylated hydroxytoluene, benzoic acid, and quaternary ammonium compounds. 32 ... 

Mercury compounds continue to have numerous commercial uses. Besides its use as a preservative, mercury is used in the manufacture of many technical and medical instruments including blood pressure measurement devices, manometers, thermometers, and barometers. Mercury is also used in production of certain types of fluorescent lamps and in the chloralkali industry, where chlorine and caustic soda are produced using brine electrolysis in mercury cells. Metallic mercury is used in the production of precious metals such as gold and silver. As part of the production process, metallic mercury can be used to concentrate gold from... 

Other negative aspects of mercury compounds are high human toxicity and the expense of hazardous waste disposal. During method development of EPA Method 532 (for PUHs), copper sulfate has been successfully used as an antimicrobial agent. " Later, another effective strategy for analyte preservation will be illustrated. 

Blood samples are best obtained in metal-free evacuated tubes containing heparin (without mercury as a preservative). Cells and plasma may be separated in order to determine the mercury distribution between plasma and blood cells and, thus, get a picture of which type of mercury compound the subject has been exposed to. The samples may be stored for a couple of days before significant hemolysis occurs. The samples may be refrigerated at 4°C or frozen until analysis. As the levels in cells and plasma may differ, it is essential to shake whole blood samples before analysis. 

C. Mercury The main source of inorganic mercury as a toxic hazard is through the use of materials in dental laboratories and in the manufacture of wood preservatives, insecticides, and batteries. Organic mercury compounds are used as seed dressings and fungicides. 

The cleanliness of equipment and reagents used in the test is of paramoimt concern. Mercury is a ubiquitous contaminant that can show up in suiprising ways, especially at the range of concentrations in the samples. An example of potential contamination is the mercury compounds that may be used as preservatives in certain phosphate buffer solutions. The analyst must be continuously vigilant when choosing reagents and supplies. 

Historically, almost every chemical or compound known to be toxic has been tried and used to inhibit the action of wood-destroying pests. Among the many chemicals used as wood preservatives are compounds based on creosote, mercury, arsenic, thallium, borate, cyanide, chromium, copper, zinc, nickel, fluorides, and pentachlorophenol. The majority fall into 3 classes ... 

Blood and hair samples are often analyzed in order to estimate exposure of humans to mercvny and its compounds. Blood should be taken by venipuncture. Since some commercial containers may contain mercury compounds added as preservatives it is advisable to check each commercial batch before use. The samples should be refrigerated but not frozen, as it is sometimes useful to measure mercvny in plasma and red blood cells separately. The separation of plasma and red blood cells should be performed as soon as possible to avoid hemolysis of the sample. If extensive hemolysis has occurred, the sample should be homogenized before an aliquot is taken for analysis. Blood samples may also be heparinized for total blood, serum, and red blood cell analyses. If unavoidable, samples may be stored deep frozen. However, repeatedly frozen and unfrozen blood samples showed a remarkable decrease in methylmercury concentrations. There is some evidence that methyl-mercvny may be destroyed during lyophilization of blood samples. 

Rubber boots may contain N-isopropyl-N -phenyl-p-phenylenediamine (IPPD), chemically related compounds and mercury compounds which are used for preservation of plasticizers (Cronin 1980 Koch and Nickolaus 1996 Nishioka et al. 1996). Occupational sensitizations to phthalates and coal tar were observed in a factory producing shoes from polyvinyl chloride granulate in former Yugoslavia. Both substances were present in the granulate (Vidovic and Kansky 1985). 

---