Plasticware

Plasticware is treated similarly except that it is rinsed well with water before use instead of baking. Note that dichloromethyl silane is highly TOXIC and VOLATILE, and the whole operation should be carried out in an efficient fiime cupboard. 

An alternative procedure used for large apparatus is to rinse the apparatus with a 5% solution of dichloromethyl silane in chloroform, followed by several rinses with water before baking the apparatus at 180°/2h (for glass) or drying in air (for plasticware). 

Miscellaneous glass and plasticware, such as pipets, centrifuge tubes, microscope slides, and number-one cover slips. 

Phytohemagglutmin (PHA) (Gibco-BRL, Gaithersburg, MD) reconstitute as directed and add sufficient quantity to Ham s F-10 medium (usually about 1-2 mL/100 mL). Colcemid stock solution (Gibco-BRL) 10 ag/mL in phosphate-buffered saline (PBS). Miscellaneous glass and plasticware, such as pipets, centrifuge tubes, microscope slides, and number-one coverslips. 

Once cleaned, glassware (and plasticware) should be covered or kept inverted. Even dust can be a troublesome contaminant. 

The Ames II test is reported to use at least threefold less test compound and sixfold less plasticware than the traditional Ames test (Xenometrix), and whilst it is still rather plastic-hungry for profiling purposes, one study reported screening 2698 compounds in a little more than a year [21]. An interlaboratory ring trial with 19 coded compounds concluded that the method provides an effective screening alternative to the standard Ames test [22]. 

Plasticware sterile 35-mm and 90-mm Petri dishes, autoclaved yellow and blue pipet tips, 1.5- and 0.5-mL Eppendorf tubes. 

The methods of preparation of glassware are indicated in Chapter 8, and if sterilisation is monitored as described the glassware should not be a source of contamination. Likewise plasticware is obtained from the manufacturer in a sterile condition. Usually sterilisation of plastic is achieved using ethylene oxide or irradiation procedures and vessels are supplied wrapped in cellophane. 

All plasticware should be sealed in special bags for autoclaving (Sterilin Ltd. Appendix 3). 

This chapter deals exclusively with cleaning glassware. There are some guidelines and suggestions on cleaning plasticware on page 90. 

In our experience, most cases of contamination stem from carryover of previous PCR amplifications performed in the laboratory. This type of contamination can be curbed by physical separation of the area where DNA extractions are carried out and PCR experiments are set up from the area where PCR products are handled and analyzed after amplification. To be effective this separation has to be absolutely rigorous and include isolation of pipettes, plasticware, reagents, water, etc. It should be noted that micropipettors used to aliquot amplification products or concentrated DNA solutions may during aliquotting contaminate specimen extracts or new PCRs by aerosols for substantial times after the initial contamination occurred. 

Table 9 summarizes procedures of blood collection for aluminum determination. Steps to avoid contamination, the analytical technique, and the aluminum levels found in the serum of healthy individuals are listed. It can be seen that, as a general procedure, plasticware was used, all materials that entered in contact with the sample were acid-washed, usually by nitric acid, and the analyses were carried out inside clean rooms. 

Considering more complex samples or samples that demand a more laborious pretreatment, a more laborious contamination control should be adopted. Slavin and coworkers [104], in order to determine aluminum in bone, wore powderless gloves and used tantalum knives and scrapers (made from ultra-pure tantalum, relatively free from aluminum) to remove adhering tissue from bone. They also used a diamond-disc saw to cut small segments of the sample for analysis, besides using only plasticware and sub-boiling distilled HN03. 

Note For this assay, use reagent-grade chemicals with the lowest practicable Sb, As, Bi, Cd, Cu, Pb, Hg, Ag, and Sn levels, and use only high-purity water and gases. Rinse all glass- and plasticware twice with 10% nitric acid and twice with 10% hydrochloric acid, and then rinse thoroughly with High-Purity Water. 

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