Biocides sampling

The agar difihision test is used to qualitatively assess the efficacy of textiles treated with diffijsible biocides. Samples are plamd in the centre of nutrient agar plates which have been inoculated widi the test bacteria. The samples are incubated at 37°C for 18-24 hours. The evaluation of this test is based on the level of growth both under and around the sanqrie. (Fig. 2) The zone of inhibition around the test material is measured and any growdi present underneath the sample is scored. 

Therefore, in laboratory testing, it is extremely important that the addition of biocide to the polymer dispersion copies as far as possible the conditions that would occur at the production plant. In almost every case a polymer dispersion sample that has been stored prior to addition of biocide will show less degradation of the bioeide than if the bioeide was added when the polymer dispersion was freshly made. This requires all additions of biocide samples to unprotected polymer dispersions to be made at the polymer dispersion plant or laboratory where the polymer dispersion is produced. As a consequence the additions must be made while the polymer dispersion is at the same temperature, pH and redox state that would occur during biocide addition to a production batch. 

Aqueous GPC can also be semiprepped in manner just like nonaqueous GPC. In this case one must consider carefully the buffers, salts, and biocides used in the eluant. If the fractions are destined for nuclear magnetic resonance experiments it will be imperative to either reduce the salt concentration in the eluant or remove salt after the initial fractionation. Likewise, if the collected samples are destined for infrared (IR) analysis, it is important to choose salts and buffers that have good IR transparency in the wavenumber ranges of interest. 

API Serial Dilution Method. The API serial dilution method is the most widely used method for the detection of microorganisms. Field test methods for estimating bacterial populations have been standardized. A standard method dealing with the dose-response (time-kill) testing for evaluating biocides has been established. Sampling methods are of special importance because effective sampling is essential to any successful analysis. 

Paint 1 - pH 9.44, Paint 2 - pH 9.18, samples tested after storage of biocides/paints at 40°C for four weeks... 

SFE has been used extensively in the analysis of solid polymers. Supercritical fluid extraction of liquid samples is undertaken less widely because dissolution or entrainment of the matrix can occur. As illustrated elsewhere SFE has also been applied for the analysis of liquid poly(alkylene glycol) (PAG) lubricants and sorbitan ester formulations [370]. The analysis of PAG additives (antioxidants, biocides and anticorrosion, antiwear and antifoaming agents) is hindered by the presence of the low molecular weight PAG matrix (liquid) and therefore a method for the selective separation of additives from PAG is required. The PAG... 

Emara [53] developed a rapid, simple, accurate and reproducible method for the quantitative determination of niclosamide ethanolamine salt (NES), the most widely used molluscicide against snail vectors of schistosomiasis, in both distilled and natural canal waters. The biocide was extracted completely from water samples by passing through Sep-Pak Ci8 cartridge and eluting the cartridge with methanol. The eluate was then analyzed directly for NES by UV Vis spectrophotometry at 330 nm [53]. 

The ECHA (Cardiff, England) Biocide Monitor is a qualitative test developed for environmental samples and is based on measurement of dehydrogenase activity [41,42]. This test is performed with a small plastic strip carrying an absorbent pad impregnated with a sensitive microorganism, nutrients, and an indicator of metabolic activity and growth. Solid samples are tested directly without extraction. Semiquantitative results are evaluated after 5-24 hours with this assay, which is available as a commercial kit. 

This product was among the top three effective performers in all systems. This product s main advantage over the others tested is that it effectively controlled the Methylobacterium sp. in all slurry samples. This is also a combination biocide that provides beneficial synergy and enables the use of lower dosages. The result is a safe biocide that decreases exposure to the handler and the end-user. The product is FDA-approved under the specified clearances. It is very effective over a pH range of 8.3-9.S and unlike the 1,5-pentanedial, it produced no offensive odour. 

Biocides most often found in the indoor environment are chlorinated hydrocarbons like chlordane, DDT, dieldrin, lindane, heptachlor and methoxychlor, pyrethroids like cyfluthrin, cypermethrin, and permethrin, organophosphates like chlorpyrifos, diazinon, dichlorvos, isofenfos, and malathion, carbamates like ben-diocarb, carbaryl and propoxur and chlorophenols like pentachlorophenol (PCP), chlorocresol (4-chloro-3-methylphenol) and o-phenylphenol. Residues formed in house dust may vary in different countries (Butte, 2003), but biocides like chlorpyrifos, DDT, methoxychlor, permethrin, pentchlorophenol and propoxur seem to be the active compounds in biocide formulations even in different continents, as they are found equally in house dust samples form Germany and the USA (Becker et al., 2002 Butte, 2003 Camann, Colt and Zuniga, 2002). Concentrations of biocides in house dust are mostly in the milligram per kilogram range, they seldom exceed a microgram per cubic meter in indoor air. 

Samples may also contain microorganisms, which may degrade the sample biologically. Extreme pH (high or low) and low temperature can minimize microbial degradation. Adding biocides such as mercuric chloride or pentachlorophenol can also kill the microbes. 

Some months after installing a biocide dosing system on the cooling water unit, one of the dosing tanks overpressurized and ruptured. The explosion propelled the dosing liquids about 20 ft. (6m) in the air. The unusually warm temperature of the tank was a clue that some form of exothermic chemical reaction occurred. Samples analyzed of the liquids and... 

Acidification to below pH2 is particularly suitable for trace metals since it minimises adsorption of metals to container walls and also reduces biological activity. Acidification before filtration will release metals bound to particulates, giving a false reading only if dissolved metals are required. Samples for anion analysis are generally not acidified. Biocides such as sodium azide are commonly added to samples... 

Production equipment that cannot be sterilized must be sanitized and disinfected by an appropriate method. This can be done by use of biocides like alcohols (70%), hydrogen peroxide, or formaldehyde-based chemicals or a combination of these. These can either be used for surface disinfections by wiping or spraying or even better by use of gas or dry fog systems for application of the disinfectants. The effect of cleaning and sanitation should be monitored. Microbiological media contact plates can be used to test critical surfaces, as inside the hot cells or glove boxes. The test samples must then be handled and monitored as radioactive contaminated units. 

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