Sampling special samplers

Terms used, methods of sampling, and sample handling will be different for water and submerged solid and semisolid samples. The methods described earlier (i.e., transect and grid sampling) are also applicable to these situations. However, semisolid samples, such as those obtained from lake bottoms, require a special sampler. 

Samples must be properly labeled. Include at least the date, time of sampling, special notes, name of sampler, and sampling point. 

Two questions, where to monitor or sample and how to obtain representative samples are both important. Surface water samples often are collected by automatic sampling devices controlled by a variety of sensors. The simplest method of collecting water is the grab technique, whereby a container is lowered into the water, rinsed, filled, and capped. Specialized samplers frequently are used to obtain water at greater depths. 

The reactor is draft-loaded with corresponding amounts of butylbromide, tin and butyl alcohol. Then the apparatus is closed with a lid fashioned with an agitator, moved into the operation chamber and connected to all piping. After that the jacket of the reactor is filled with a heat carrier with a temperature of 90-95 °C, the contents of the apparatus are heated at agitation to 85-90 °C, the operation chamber is closed with a protective plug and sources of y-radiation are introduced into the chamber. After certain periods of time the mixture in the reactor is sampled with the help of a special sampler. 8-10 hours after the radiation has started, the reaction is completed and the sources of radiation are taken out of the chamber. The reactive mixture is loaded off and the apparatus is prepared for the next operation. 

Eor toxic materials, it usually is advisable to provide ventilated sampling hoods or breathing-air stations and masks, to assure that the sampler is adequately protected from toxic or flammable vapors and dusts. Special provision for access to and exit from sampling points also may be needed at elevated locations and to avoid tripping or bumping ha2ards and to ensure that the sampler does not transverse areas not intended as walkways, eg, tank covers or roofs. 

As well as the methods discussed above headspace samplers, pyrolyzers, thermal desorbers, and column switching devices could be considered as specialized sample inlet systems. These are treated separately in Chapter 8. 

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... 

The whole atomizer may be water cooled to improve precision and increase the speed of analysis. The tube is positioned in place of the burner in an atomic absorption spectrometer, so that the light passes through it. Liquid samples (5-100 mm ) are placed in the furnace, via the injection hole in the centre, often using an autosampler but occasionally using a micro-pipette with a disposable, dart-like tip. Solid samples may also be introduced in some designs, this may be achieved using special graphite boats. The sample introduction step is usually the main source of imprecision and may also be a source of contamination. The precision is improved if an autosampler is used. These samplers have been of two types automatic injectors and a type in which the sample was nebulized into the furnace prior to atomization. This latter type was far less common. 

To avoid the problems with vacuum cleaner surface dust sampling a special surface dust sampler, HVS-3, was developed (Roberts et al, 1991). The sampler consists of a nozzle that can be adjusted to a well defined distance to the surface, a cyclone that collects the dust particles, an air pump, and an exhaust filter to capture particles that are not retained in the cyclone. SVOCs may break through the cyclone as vapors and a PUF plug can be inserted after the cyclone. HVS-3 has been modified to ensure a more constant suction pressure and volume, and a known sampled area (Gyntelberg et al, 1994). The design and use of the HSV3 has now been standardized (ASTM, 1997, D 5438-94). 

Collecting a representative sample of snow for precipitation chemistry measurements poses special problems. Most electronic sensors on precipitation chemistry samplers do not detect snow, particularly light, dry snow, as efficiently as rain. Light, dry snow may also fall into and then be blown out of an open container or funnel. Snow may stick to sampler parts and later be blown into the sample container. Ice may coat sampler parts and prevent proper operation. Heavy snow may... 

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. 

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