Metal samplers

Because soil is abrasive, it can be expected that small amounts of the sampler itself may be transferred from the sampler to the sample during sampling. Many soil samplers are constructed of metal and pose no problems for most samples. Figure 7.3 shows two of many types of metal samplers available. Plastic samplers of similar design are also available. If low concentrations of metals are an important component of the analysis, then knowing the sampler composition may be important. 

In many cases, new samplers will not be used to obtain each sample from a contaminated site, which will often be analyzed for very small amounts of contaminants. Even if this is not the case, it is important that the sampler be cleaned thoroughly between samples. As with sample containers, samplers must be compatible with the sample and with the analysis to be done. Metal samplers may add small but measurable amounts of metals to the sample, causing interference with the analytical procedure to be preformed. 

With very viscous or semi-solid liquids such as syrups, molasses and massecuite, the sample is taken by means of a cylindrical metal sampler in such a way that proportionate amounts are taken at different depths. With very dense products which may have crystallised sugar at the bottom, it is especially necessary to reach with the sampler the very bottom of the vessel. Several samples are withdrawn and mixed and the sample or samples for analysis (about 200 grams each) then stored in glass bottles with ground stoppers. 

The sample is put in a special airproof metallic sampler, filtered from ammonia chloride gaseous ammonia is sent through the filtrate. The reaction is considered complete, if after the passing of ammonia there is no sediment of ammonia chloride. In case there is sediment, coammonolysis is continued and the sample is taken again after 1-2 hours. 

The choice of the appropriate mineral acid and oxidant depends on the final analytical technique to be used. For instance, HC1 is not recommended for furnace analysis as it can cause Cl interferences, while H2S04 is not desirable with ICP-AES or ICP-MS because of transport interferences derived from its viscosity. With ICP-MS HNO3 and H202 are preferred since the effect of polyatomic interferences is minimal as compared with HC1, HC104 and H2S04, which introduce polyatomic ions such as C10+ and SO+ [28-32]. In any case, in order to minimize corrosion of the metal sampler and skimmer cones with ICP-MS, final sample solutions should not contain high acid concentrations (e.g., above 10 percent for HNO3). 

Near surface water samples were collected with a precleaned metal sampler. Samples of 10 to 15 liters were collected at each site and placed in 20 liter glass carboys for in-field extraction as... 

The end or front of the plasma flame impinges onto a metal plate (the cone or sampler or sampling cone), which has a small hole in its center (Figure 14.2). The region on the other side of the cone from the flame is under vacuum, so the ions and neutrals passing from the atmospheric-pressure hot flame into a vacuum space are accelerated to supersonic speeds and cooled as rapid expansion occurs. A supersonic jet of gas passes toward a second metal plate (the skimmer) containing a hole smaller than the one in the sampler, where ions pass into the mass analyzer. The sampler and skimmer form an interface between the plasma flame and the mass analyzer. A light... 

In this work, atmospheric particles (PM 10 and PM 2.5) were collected by a dichotomos air sampler. Several leaching procedures were investigated for decomposition of heavy metals. The digests were pre-concentrated with sodium diethyldithiocarbamate. The determinations were canted out on a Vartan Model AA-220 atomic absorption spectrometer. The instrarment was equipped with a GTA-110 graphite furnace system. Table 1 shows the concentrations of heavy metals associated with PM 10 and PM 2.5 particles. Table 1. Concentrations of heavy metals in PM 10 and PM 2.5 atmospheric particles (ng/m )... 

Several round-robin intercalibrations for trace metals in seawater [26-30] have demonstrated a marked improvement in both analytical precision and numerical agreement of results among different laboratories. However, it has often been claimed that spurious results for the determination of metals in seawater can arise unless certain sampling devices and practical methods of sampler deployment are applied to the collection of seawater samples. It is therefore desirable that the biases arising through the use of different, commonly used sampling techniques be assessed to decide upon the most appropriate technique ) for both oceanic baseline and nearshore pollution studies. 

A modified active method was used for collect gaseous metals from soil air (Wang et al. 2008). The sampling device consists of a cone-shaped sampler, a special Millipore filter (0.45 jam), a liquid collector, and a battery-operated pump. The liquid collector comprises a high... 

Such nonsyringe techniques do not eliminate a prior preparative stage and most of these automatic solid samplers do not take care of measuring the sample volume or quantity that they introduce. These samplers generally are constructed of metal such that the sample could interact with metal surfaces. Samples could evaporate when left in the sample racks for long periods. 

Diffusive samplers have also been developed to determine SVOCs but there have been relatively few studies to date. An example is the passive flux sampler developed by Fujii et al. (2003) to determine the rate of emission of phthalate esters from materials. The sampler consisted of a circular metal disc containing activated carbon particles held within an inert matrix of PTFE. The sampler was placed on the material under test giving a diffusion length of 0.5 or 2 mm depending upon the design and adsorbed phthalate esters were extracted from the sampler with toluene and determined by GC-MS. 

Cells 1 and 2 of the barrier frame were filled with 8-14 SMZ while Cell 3, adjacent to the pilot-test tank wall, was filled with iron/surfactant-modified zeolite pellets (Fe/SMZ pellets, see below). During refilling, sheets of plywood were temporarily placed against the inner faces of the barrier frame to retain the fill material. The SMZ was transferred using a conveyor belt that ran from the outside the pilot-test tank to the appropriate cell. While the SMZ was loaded in the barrier frame the samplers were reinstalled in their original positions. The annular space between the plywood and the outer perforated metal of the frame was filled with aquifer sand. The plywood was then pulled out of the cell using a jack and appropriate blocking. 

Equipment blanks enable us to assess the collected sample representativeness. The purpose of collecting equipment blanks is to detect the presence of contamination from the sampling equipment itself or any cross-contamination with previously collected samples. For example, metal liners for core barrel or split spoon samplers are not always precleaned by the manufacturer or distributor. They must be cleaned in the field prior to sampling to eliminate the potential for sample contamination. 

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