Rotary sample divider

There are many laboratory devices available for the reduction of the primary sample to an analysis sample. The three most important methods used in the pharmaceutical industry are (i) scoop sampling, (ii) cone and quartering, and (iii) the spinning riffler or rotary sample divider (Fig. A-3). 

The rotary sample divider or spinning riffler was first described in 1934 [20] and conforms to the golden rules of sampling. The preferred method of using this deviee is to fill a mass flow hopper in such a way that segregation does not occur. The table is then set in motion and the hopper outlet opened so that the powder falls into the collecting boxes. The use of a vibratory feeder is recommended to provide a constant flowrate... 

Figure 1.32 Retsch PK 1000 laboratory rotary sample divider 1 feed hopper, 2 on/off switch, 3 time setting controls, 4 upper cone, 5 lower cone, 6 stand, 7 display, 8 start button, 9 sample slot adjustment, 10 sample vessel, 11 reject container...

Scott, K.J. (1972), The CSIR rotary sample divider, CSIP Special Report, Chem., Pretoria, South Africa, 49... 

The yield of between 21 and 23 kg of the final product was stored under argon prior to sample division in a rotary sample divider. This operation yielded 20 sub-samples each of approximately 1 kg. Each sub-sample was protected from oxidation by an argon atmosphere. The samples for analysis were transferred to glass ampoules, previously dried in nitrogen at 28°C in a special box over dry (blue) silica gel. The method of filling the ampoules varied with each coal as follows ... 

Coal 182 sample division by rotary sample divider and direct transfer to the ampoule. 

The rotary sample divider, or spinning riffle, is less prone to operator error than is the static riffle. Basically it consists of a hopper which allows particulate material to flow on to a vibrating chute which then discharges into a number of sample boxes located in a rotating ring. Several units of this type are available commercially. 

Rotary sample dividers or rifflers may or may not use a cone or dome to spread the sample. With one type, the powder is poured through a funnel and falls either directly or down a stationary cone into a set of jars attached to a rotor, so that the sample receivers themselves rotate and similar proportions of the sample fall into all the jars. Another major variant employs a dome which rotates at high speed and flings the powder into an array of stationary receivers. 

Spinning Riffler. A spinning riffler is a rotary sample divider. The sample fills a mass flow hopper so that no heaps are present and then falls from the hopper into collection boxes that are set in circular motion. A vibratory feeder supplies a constant flow rate. This method yields the most accurate results among the many sample reduction devices. 

Mechanical methods also exist for dividing up particulate material into suitably sized samples. Samples obtained by these means are usually representative of the bulk material within limits of less than 1 per cent, and are based upon the requirements established by the British Standards Institution. Sample dividers exist with capacities of up to 10 L and operate either by means of a series of rapidly rotating sample jars under the outlet of a loading funnel, or by a rotary cascade from which the samples are fed into a series of separate compartments. Sample dividers can lead to a great deal of time-saving in laboratories dealing with bulk quantities of powders or minerals. 

Quartering by rotary divider —Arbitrated sample stored in Lab I... 

Retsch rotary divider PK 1000 (Figure 1.32) is designed for representative sampling and dividing of large quantities of bulk material. 

Based on their construction, sampling valves can be divided into rotary, membrane, and piston types. The switching of gas tracks in rotary valves occurs through... 

Imine (Schiff base) formation. Wash the aldehyde-functionalized resin with different methanol solutions, starting with 10% (v/v) methanol and finishing with 100% (v/v) methanol at 10% (v/v) increments (see Note 8). Slurry the methanol-saturated resin in 100% (v/v) methanol (1 mL/g of gel) and place it on a shaker with gentle shaking to prevent the resin from settling. Divide the gel into n aliquots, where n is the number of different amines used to synthesize the combinatorial library (see Note 9). Dissolve a fivefold molar excess (relative to the amount of epoxide in the gel) of each amine in methanol (0.25 mL/mL of slurry). Incubate the n aliquots with the previous mixture at 25°C in a rotary shaker (200 rpm) for 1 h. This procedure allows the amine component to become completely mixed with the supplied resin sample and promote imine formation (22). 

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