Closure , centrifuge tubes

Plankton, periphyton (plants) Ti Mn Fe Ni Cu Zn Se Rb Sr Pb Digest with HNO3/H2O2 in a PEP centrifuge tube with loosely fitted closure [WDC] Measure with TXRF spectrometer [WDC-TXRF] Pettersson and Olsson 1998... 

Samples are prepared in disposable 15-ml polypropylene centrifuge tubes with an aliquot of the final extract being transferred to borosilicate glass autosampler vials (2 ml capacity) with Teflon-lined septum closures. 

It is best not to decant, or pour off, supernatant material from centrifuge tubes. Decanting will always result in some liquid spilling down the outside of the tube or becoming trapped between the rim of the tube and the closure (cap or plug), and will remain to contaminate the hands or, in a subsequent centrifugation step, biohazardous fluid may be spun off as droplets that form an aerosol (209,... 

Specimen tubes should be centrifuged with stoppers in place. Closure reduces evaporation, which occurs rapidly in a warm centrifuge with the air currents set up by centrifugation. Stoppers also prevent aerosolization of infectious particles. Specimen tubes containing volatiles, such as ethanol, must be stoppered while they are spun. Centrifuging specimens with the stopper in place maintains anaerobic conditions, which are important in the measurement of carbon dioxide and ionized calcium. Removal of the stopper before centrifugation allows loss of carbon dioxide and an increase in blood pH. Control of pH is especially important for the enzymatic measurement of acid phosphatase, which is labile under alkaline conditions engendered by CO2 loss. Indeed, once the serum is separated for acid phosphatase tests, a tablet of disodium citrate should be added to stabilize the pH at about 6.2. 

Pnor to automated sequencing or mass spectrometry, one may wish to concentrate the peptide in a somewhat smaller tube Transfer the sample to a 1500 or 500 uiL Eppendorf polypropylene tube and combine with a rinse of the 12 x 75 mm tube (rinse with 100 pL of 80% MeCN/0.01% TFA it is advisable to rinse the tube several times if practicable). Immediately remove the solvent by vacuum centrifugation. We advise using only the transparent (uncolored) Eppendorf tubes to handle peptide solutions. Do not use tubes of any kind with O rings or septum closures because they have been shown to contain compounds that can interfere with mass spectral analysis. If a microbore HPLC system is available,... 

Some of the older clinical centrifuges have been shown to be hazardous (390). The microhematocrit centrifuge, in particular, has been shown to produce aerosols. One frequently sees blood samples centrifuged in tubes without closures or with cotton plugs secured in the tubes by means of tape or other unsecure means. Remember that some tissue specimens contain viable infectious microorganisms, particularly hepatitis virus, and that open tubes, contaminated closures, and concomitant release of aerosols from blood sam-... 

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