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An automatic collector for density gradients

Journal of Automatic Chemistry
Hindawi Publishing Corporation
Publication Date
DOI: 10.1155/s1463924680000259
  • Research Article


An automatic collector for density gradients Rex Mottershead, Medical Research Council Cell Mutation Unit, University ofSussex, Brighton, Sussex BN1 9QG, UK. Introduction The paper strip method of Carrier et al for collecting density gradients eliminated some of the tedium associated with the earlier filter disc technique of Bollum 2]. The automatic collector described here was developed to further improve the technique by removing the need for the operator to count drops or time or to move the strips by hand at short intervals. This has advantages in that it speeds the process considerably without loss of accuracy andfurther eliminates tedium for the operator. Description of collector The principle component of the collector is a ’Minipump’ type IV peristaltic pump made by Schuco Scientific Ltd., London, England. The pump is used to remove the contents of a density gradient and to dispense them onto a paper tape which is continuously advanced by a transport mechanism connected directly to the rotor of the pump (Figure 1). The pump is attached to a base plate which also carries a holder for a reel of Whatman grade 17.1 cm cellulose paper tape. A short channel, lcm wide, is mounted on the side of the plastic cover of the pump. The channel and the cover are drilled in line with the centre of the pump rotor and a short nylon rod, covered by silicone rubber tubing, is passed through the channel and engaged in the hole in the rotor where it is held by friction. A flat phosphor-bronze spring holds a small idler wheel against the underside of the rod, these two parts together forming the tape transport mechanism. The input of the peristaltic pump is connected by a short length of flexible tubing to a section of 1.3 mm o.d. cannula. The output is attached to a second short length of tubing, the end of which is held by a bracket over the end of the channel. Figure 2 shows the overall layout of the device. Operation of the collector Operation of the collector is very simple; the section of cannula is lower

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