Sample splitter

The choice of interface is dependent on both the particular analysis and the instrumentation available. Some interfaces require the use of very low flow rates and therefore necessitate the use of either microbore or capillary LC equipment, or a sample splitter if standard-bore equipment is used. Thermospray ionization is the most frequently quoted interface, owing to compatibility with standard-bore instruments. However, the upper molecular weight limit for thermospray ionization is low, and the electrospray interface is becoming popular. The maximum flow rates for different interfaces are listed in Table 3.8.54... 

FIGURE 7 Subsampling (a) coning and quartering (b) table sampler [6] (c) oscillating hopper (paddle) sample divider [6] (d) spinning riffler (BSI) (e) riffle/chute splitter (BSI) if) revolving sample splitter [14]. 

A sample splitter described by Fooks [24] consists of a feeder funnel through which the sample is fed. It passes on to the apex of two resting cones, the lower fixed and the upper adjustable by means of a spindle. Segments are cut from both cones and by rotation of the upper cone the effective area of the slits can be varied to vary the sampling proportion. Material, which falls through the segmental slots, is passed to a sample pot. The residue passes over the cone and out of the base of the unit. 

MACKAY, K. M., SUTTON, K. J. and WATT, R., A glass-Teflon continuously variable sample splitter assembly for the Autoprep 705, Journal of Chromatography, Elsevier Publishing Co., 29, 1967, 223-4. 

Sample splitter A device that permits the introduction of small and reproducible portions of sample to a chromatographic column. In capillary gas chromatography, a reproducible fraction of the injected sample is introduced onto the column, while the remaining portion goes to waste. 

Soil Core Splitting and Analysis. A mechanical sample splitter was constructed to remove frozen soil from the steel cylinders and divide it longitudinally into three portions. This device was an electronically controlled hydraulic pump that pushed the frozen soil past two steel blades and into three shoots which channeled the samples into collection containers one for moisture determination, one for quantitative chemical analysis and one for physical analyses. Soil samples were kept frozen for about 2 weeks before being split and two weeks more were required to split the samples. 

Fig. 9.10 Laboratory test equipment a) mixers, b) sample splitters and screen, c) feeder and mills, d) ovens...

Fig. 9.9 Agglomerate strength testers top) hydraulic four-column press for the determination of compression strength bottom) from left, rotating tube for measuring degradation at transfer points, drop test arrangement, and drum abrasion tester Fig. 9.10 Laboratory test equipment a) mixers, b) sample splitters and screen,...

The most widely used silica open tubular columns have inside diameters of 0.32 and 0.25 mm, Higher-resolution columns arc also available with diameters of 0.20 and 0.15 mm. Such columns arc more troublesome to use and arc more demanding on the injection and detection systems. Thus, a sample splitter must be used to reduce the size of the sample injected onto the column and a more sensitive detector system with a rapid response time is required. 

The second type of inlet, called a splitter (Fig. 22.7), again uses a syringe to inject the sample. The sample is vaporized and effectively mixed with carrier gas in the mixing tube, after which the vapor passes over a tapered hollow needle. Because of the difference between the inside diameter of the mixing tube outlet and that of the tapered needle, a fraction of the total sample is introduced into the column as a narrow zone. The splitting ratio is a function of the pressure in the inlet, and can be varied. Such a sample splitter is used with capillary columns and high-resolution columns because of their relatively low capacity. 

The sampling station has a dust collection system. The dust precipitated in the latter is returned to the sample splitter, so that no dust losses occur. 

The quantitative agreement between the two columns gives additional information for the identification. Discrimination is always possible when a sample splitter is used. 

Valves—Valves or sample splitters, or both, are required to permit switching, backfluishing, or for simultaneous analysis. 

Figure 1.3 Examples of sample splitters (a) rotating sample splitter (Courtesy of R. Snellings, Flemish Institute of Technological Research, Mol, Belgium.) and (b) static sample splitter.

Great care must be taken to ensure that the sample examined is representative of the material to be analyzed. Differences in shape and SG in heavy mineral fractions can easily lead to sampling errors, and if a small sample splitter (Wentworth et al. [1934] Muller [I960]) is not available, the whole of the heavy fraction should be subjected to quartering procedure until a suitable quantity is obtained. 

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