Manual sampling devices

Filters are used on almost all analyses many types or different materials are used in automated and manual sampling. Validation of the pre-wetting or discard volume is critical for both the sample and standard solutions. Plugging of filters is a common problem, especially with automated devices and with Apparatus 4. 

Our sampling device, the automatic radon counter and aerosol sampler (AR-CAS), was used to collect the continuous set of aerosol samples. This instrument also counted the radon daughter-product decay and printed a nearly real-time record for each sample (see Reference 6 for photographs and details of operation). The ARCAS I system consists of a deck-mounted sampling unit and an indoor electronic unit containing sampler controls, calendar clock with display, thumbwheels for manual data entry, and a thermal printer. 

Water samplers can be either automatic or manually operated. Automatic samplers are used to collect samples at either fixed time-intervals or in proportion to the flow and then to retain the water sample in a separate container. These are commonly used, for example, in rivers or from a point source (effluent outfall). In addition, automatic samplers can be used to allow the collection of time-averaged samples or precipitation. In the case of the latter, the onset of rainfall triggers the collection mechanism. Manually operated samplers are essentially open tubes of known volume (typically 1 to 30 1) fitted with a closure mechanism at each end. They are constructed of stainless-steel or PVC. Manually operated samplers are particularly useful when sampling from open waters (e.g. oceans, seas, lakes, etc.) at specific depths. The sampling device is lowered on a calibrated line to the specific sampling depth, the sample is taken and then the top and bottom lids are closed and sealed. 

A typical manual water-sampling device is shown in Figure 3.4. 

Frantz and Hare [7.10] described in an internal report in 1973 a system where a sample was inserted into a nonsegmented stream by manually breaking a capillary of a defined volume. A colorimeter was used to measure reaction product. Hare later joined Beecher and Stewart who replaced the awkward sampling device by a chromatographic injection valve... 

Reduction of bulk sample size is performed either manually by successive quartering the bulk sample, by increment sampling or by using rotation sampling devices. 

Automatic devices cause required acts to be performed at given points in an operation without human intervention. For instance, an automatic titrator records a titration curve or simply stops a titration at an endpoint by mechanical or electrical means (such as a relay) instead of manually. Automated devices, on the other hand, replace human manipulative effort by mechanical and instrumental devices regulated by feedback of information, so, the apparatus is self-monitoring or selfbalancing. An automated titrator may be intended to maintain a sample at some preselected (set point) state— for example, at pH = 8. To do this, the pH of the solution is sensed and compared to a set point of pH = 8, and acid or base is added continuously so as to keep the sample pH at the set point. This type of automated titrator is called a pH-stat [2]. 

When a study of the vertical migration of organics in soil is needed, samples will have to be obtained from various known depths. Sampling techniques to accomplish this include manual excavation of a pit or trench, various types of hand or motor driven core sampling devices, or sampling thieves. In a study of this type, the sampling technique should provide an accurate measurement of the depth of the sample below the original surface. It should also minimize any contamination of the sample with soil from either above or below the layer sampled. 

On a technical note, the opening of the sampling device must be 2.5-3 times the top size of the coal to meet requirements (ASTM, 201 Ih) and the ISO has established design criteria for several types of hand tools (Figure 8.1) that can be used for manual sampling. One consideration is that the device be able to hold the minimum increment weight specified without overflowing. 

Coal samples may be obtained by either manual or mechanical sampling devices, the latter being more appropriate where large tonnages are experienced (e.g., at coal shipment terminals with throughputs up to 10 000 tons h ) and where continuous operations or operator safety dictate their use. 

Manual sampling systems involve minimal equipment but they are costly and time consuming for routine monitoring. They may simply allow a large (bulk) sample to be obtained, which is then divided into one or more sample containers appropriate to the subsequent analyses. Sometimes samples are required from known depths, for example, in a raw water reservoir, when a depth sampler will be needed. These devices can be lowered to the known depth and then opened and closed before being recovered to the siu face. This type of sampHng is usually done by sample collecting personnel. 

To the best of this author s knowledge, 3DDfW preforms have been only produced in small demonstration samples on some manually operated devices. This author is not aware of any industrial-scale automated machines for their production. By the nature of this particular 3D weaving process, the fabric cross-sectional dimensions will be always relatively small (similar to the well-known situation with 3D braided fabrics), and the weaving speed will be always much slower than in the production of... 

They may be injected through the SPE cartridge directly into the injection valve of the ion chromatograph or into autosampler vials. The most common manual SPE device is a vacuum-driven accessory for simultaneous pretreatment of up to 12 samples (Eigure 10.410). Such a sample preparation station has individual stopcock valves for each 5 cm sample reservoir to allow control of individual flow rates. Samples can also be transferred directly to various autosampler vials. 

Figure 12.1 TLC Sample Streaker. A manually operated device used to apply large volumes of solution as a continuous, narrow band (1 mm width) onto a preparative plate up to 40 cm wide. Solution is applied through the mechanical action of forcing the plunger of a 250 or 500 pi syringe downward as it is pushed across a sloping stainless steel bar. (Photograph courtesy of Alltech—Applied Science Labs.)...

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