Pipet washing

Cool die sample in an ice bath and add 1/10 volume of Soln. A. Vortex and allow to precipitate in an ice bath for 30 min. Spin for 5 min at 5000 to 10 000 x g in a refrigerated centrifuge. Remove the supernatant by aspiration with a pipet. Wash the pellet once with 0.5 sample volume ice-cold 10% TCA (w/v) and once with 0.5 sample volume ice-cold ethanol-ether 1 1 (v/v) to remove traces of TCA. Dry the pellet at the air and dissolve in 0.1 N NaOH or 0.1 M Tris pH 8.0. 

Make up all stocks using sterile disposable plastic containers and pipets. Washed glass items can be contaminated with detergents that are toxic to the eggs. Filter aU concentrated stocks through 0.45-pm Milhpore filters into sterile plastic tubes. Store frozen at 20°C. 

A 2-1. two-necked, round-bottomed flask equipped with a magnetic stirrer (Note 1) is fitted with a 250-ml. pressure-equalizing constant-rate dropping funnel and a condenser, the top of which is connected to a mercury trap to prevent the entrance of air during the reaction and for the detection of gas evolution. The dropping funnel is removed, and 35 g. (0.85 mole) of sodium hydride dispersed in mineral oil is added (Note 2). The mineral oil is removed by washing the dispersion four times with 100-ml. portions of benzene (Note 3). The benzene is removed with a pipet after the sodium hydride is allowed to settle (Note 4). 

Sample carryover Watch for potential carryover in pipetting and washing steps... 

Jars containing the same amount of hand wash solution as used to collect the entire hand wash from the test volunteer should be fortified. The samples are fortified with the appropriate amount of active ingredient solution using a 1-mL volumetric pipet, blowing out the remaining solution in the pipet. The solutions are capped, shaken, and placed immediately in a freezer or dry-ice cooler. 

Face wipe samples are treated similarly. The face wipe is placed in an appropriate jar and wet with the appropriate amount of wash solution. The sample is then spiked using a 1-mL volumetric pipet and immediately capped, processed, and frozen. 

Centrifuge the sample for 2 min at 500x to collect the resin, ensuring that it is pelleted evenly at the bottom of the tub. Remove the flow-through supernatant by pipetting (reserving a 3% aliquot) and wash the resin 3 times with 1 ml of buffer BB each. 

Stop the reaction by removing the solution from the beads. This can be done by simply pipetting the solution away from the beads or by physically removing the beads. The beads may be washed once with iodination buffer to assure complete recovery of protein. Exact timing of the reaction is important to obtain reproducible results. 

XANES to ensure the quality of the synthates. Three batches of ferrihydrite were synthesized and precipitates were washed 5-6 times to ensure a chloride-free synthate. Ferrihydrite precipitates were redispersed in 200 mL of double deionized (DDI) water at (1) room temperature (25°C), as well as preheated in water baths to temperatures of (2) 50°C and (3) 75°C. For all of these slurries, pH was kept constant at 10 using 1M KOH. 40 mL samples were pipetted from each reaction vessel after 0, 1,2, 3, and 7 days. Slurries were centrifuged, washed three times with DDI water and air dried for analyses (BET, XRD, and XANES). BET analyses were used to evaluate the decrease in surface areas with increasing crystallinity, and XRD and XANES were used to detail the structural and speciation changes in iron. 

Pipets pose a special problem. Brushes cannot be used because of the shape of some pipets and the narrowness of the openings. If soap is to be used, one must resort to soaking with a warm soapy water solution for a period of time proportional to the severity of the particular cleaning problem. Commercial soaking and washing units are available for this latter technique. Soap tablets are manufactured for such units and are easy to use. 

Add the primary antibody to the living cells at 4°C in BSA-PBS, and incubate for 30 min (1-mL vol for a 35-mm dish). Do not pipet directly onto the cells, but add antibody solutions at the edge of the dish, and add wash solutions from a wide-mouth bottle or beaker to minimize the potential of removing cells by too vigorous a fluid... 

Harvest the primary antibody solution from the dish using a Pasteur pipet and save. Wash the dish again in BSA-PBS at 4°C five times. 

To assess the efficiency with which the pipet is washed between reagent steps, two vials were placed into the reagent carousel. One contained distilled water... 

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