Contamination free

Recycling is not the total answer to the soUd waste problem. However, efficiently operated recycling programs can easily divert 35% or more of municipal soUd waste away from disposal. Curbside coUection systems offer the opportunity to coUect the greatest amount of recyclables in the most cost-efficient manner. It is imperative that communities and recyclers operate programs that are glass-friendly and which result in color-separated, contaminant-free material. 

The very low Hg concentration levels in ice core of remote glaciers require an ultra-sensitive analytical technique as well as a contamination-free sample preparation methodology. The potential of two analytical techniques for Hg determination - cold vapour inductively coupled plasma mass spectrometry (CV ICP-SFMS) and atomic fluorescence spectrometry (AFS) with gold amalgamation was studied. 

For optimum splitting, a contamination of less than 2% was found. By operating at slightly higher flow rates, one stream could be made contamination free. Thus, a clean product phase can be obtained when performing the nitration in the T-piece/ tube reactor. 

Dion J-L (2009) Contamination-free high capacity converging waves sonoreactors for the chemical industry. Ultrason Sonochem 16 212-220... 

Surface-water samples are usually collected manually in precleaned polyethylene bottles (from a rubber or plastic boat) from the sea, lakes, and rivers. Sample collection is performed in the front of the bow of boats, against the wind. In the sea, or in larger inland lakes, sufficient distance (about 500 m) in an appropriate wind direction has to be kept between the boat and the research vessel to avoid contamination. The collection of surface water samples from the vessel itself is impossible, considering the heavy metal contamination plume surrounding each ship. Surface water samples are usually taken at 0.3-1 m depth, in order to be representive and to avoid interference by the air/water interfacial layer in which organics and consequently bound heavy metals accumulate. Usually, sample volumes between 0.5 and 21 are collected. Substantially larger volumes could not be handled in a sufficiently contamination-free manner in subsequent sample pretreatment steps. 

A conventional analytical method, like solvent extraction-graphite furnace atomic absorption spectrometric detection, requires a contamination-free technique. Moreover, it is time-consuming and troublesome, as litres of the sample solution must be treated because the dissolved concentration of iron in oceanic waters is extremely low (lnmol/1 = 56ng/l). Martin et al. [341] recently found that the dissolved concentration of iron was less. 

Batley and Matousek [390,778] examined the electrodeposition of the irreversibly reduced metals cobalt, nickel, and chromium on graphite tubes for measurement by electrothermal atomisation. This method offered considerable potential for contamination-free preconcentration of heavy metals from seawater. Although only labile metal species will electrodeposit, it is likely that this fraction of the total metal could yet prove to be the most biologically important at the natural pH [779]. 

All of the samples analyzed were standard one-inch diameter polished thin sections. Whenever feasible the samples received a final, cleansing polish with 1 pm diamond compound made from commercial graded diamonds embedded in "vaseline". Commercial diamond paste has proved unsatisfactory due to high levels of K, Na, Cl, Si, F, and Ca. Samples are then cleaned with carbon tetrachloride, rinsed in ethanol, and coated with vacuum evaporator. This sample preparation technique was developed during our studies of minor elements [16,17] and has proved to produce consistently contamination-free samples. 

The authors of this study divided their dataset into harbour and offshore sediments, assuming that the latter are contaminant-free, and used Li as the normalizing agent. All samples were compared to the regression equation based on the offshore sediments, which indicated considerable Zn contamination -with some samples >3 times background... 

In either of the above-mentioned cases, two types of information need to be obtained before sampling and analysis are performed. First, information about the background level of the component of interest is needed. It might be assumed that transect samples can be taken in the area starting from one place that is contamination free and continuing across the contaminated area to another point where there is no contamination. This would delineate the area of interest or concern. 

It is extremely important that all sampling equipment and containers be clean and compatible with the sample to be contained before they are used. This must include caps and cap liners. In many cases, containers will be new and used containers never used. In some cases, containers will be certified as being contaminant free. These types of containers are always to be preferred for sample storage. 

Provision of adequate ventilation is one of the keys to development and maintenance of a contaminant-free workplace. Design of a proper ventilation system is normally a task undertaken by a professional engineer or a qualified industrial hygienist. All that will be attempted here is to present the principles so that the topic can be considered with some meaningful background. 

There are other metals for which compelling cases can be made to produce contamination-free oceanic reference seawater. These include other bioactive metals (e.g., zinc, cobalt, cadmium, and copper), tracers of anthropogenic contamination (e.g., lead, Box 3.1), and non-bioactive metals used as tracers of geochemical and physical processes (e.g., aluminum). 

Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from Gainesville, FL with individual fractions of three individual petroleum products at 24-25 °C for 24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method 625. Average acenaphthene concentrations reported in water-soluble fractions of unleaded... 

Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from Gainesville, FL with individual fractions of three individual petroleum products at 24-25 °C for 24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method 602. Average benzene concentrations reported in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were 8.652, 0.349, and 0.200 mg/L, respectively. When the authors analyzed the aqueous-phase via U.S. EPA approved test method 610, average benzene concentrations in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were lower, i.e., 1.107, 0.073, and 0.066 mg/L, respectively. 

Source Thomas and Delfmo (1991) equilibrated contaminant-free groundwater collected from... 

---