Air displacement pipette

An air displacement pipette (Fig. 33) and an applicator (Fig. 34) are used with a nominal volume of 32 pi. It is not necessary to rinse the tip of the pipette, since it is entirely impractical (and in fact impossible) to rinse the tip when drawing blood from the finger pad or ear lobe. However, the test strip must 

There is no special need to service the pipette if the user observes the rules governing volume dosage via air displacement pipettes. 

This did away with centrifuging. However, possible effects could be that the volume of serum (or plasma) produced from the whole blood sample may be too low, or the erythrocytes may burst or may rub on and haemolyse the sample. Comparison of the methods of the Reflotron system vs. conventional analysis showed that this kind of serum (plasma) separation does not influence the routine methods in clinical chemistry. 

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If the slide is ready to receive the sample, a green lamp lights up at the DTSC module (Fig. 18) and a beep is emitted. 10 pi of the sample is now applied by means of the electric air displacement pipette. Application of the sample is monitored by an automatic sample detector system. After successful application of the sample the slide travels fully automatically to the pre-incu-... 

The Reflotron system consists of the reagent carrier, reflection photometer and an air displacement pipette or applicator. It is easy to operate. The required blood sample is obtained by puncturing the finger pad or ear lobe with... 

After turning on the instrument, the requisite measurement module is inserted. The user must calibrate the instrument before performing the first analysis of a patient sample. This is done by means of the calibrators. Two different calibrators must be used per method. After calibration - which is now stored for 7-30 days analysis of control or patient samples can be performed. Depending on the method, either undiluted or diluted serum or plasma can be employed. Following insertion of the reagent carrier in the transport slide of the instrument, the material to be examined is transferred on the test area by means of a 30 pi air displacement pipette. The start key is pressed directly and the transport slide pushed in. After the reflectance measurement the result is displayed by the instrument. 

The dwelling time covers the period that elapses between the application of the sample to the test slide and its insertion into the measurement device. Since the sample is inserted by the analyser in the Ektachem, Cobas Ready and Stratus instruments, this factor can be neglected as far as these systems are concerned. It is only with the Ektachem DT-60, Reflotron and Seralyzer that dosage of the sample is effected by means of an air displacement pipette via the user. No time error can occur with the Ektachem DT-60 because an inter-... 

Inasmuch as the right conditions for crystallization cannot be predicted, a large number of conditions (precipitant, pH, temperature, protein concentration, additives, etc.) need to be screened to produce a crystal suitable for data collection. To minimize the amount of precious protein material used in these preliminary experiments and avoid the large amount of manual labor involved, automation is becoming very common.8 When setups are done by hand, the pipetting is usually done using standard air-displacement pipettes, which are extremely inaccurate under 1 pi, making this the minimal practical protein volume per experiment. All of the various robotic systems can use sample volumes as low as 50 nl, and some as little as 1 nl. 

The pipettes are all based on air displacement with a simple plunger and are provided with non-wettable plastic (usually polypropylene) disposable tips to contain the solution, preventing any contamination of the pipette itself. Most micropipettes have a double action plunger system, i.e. calibration and overshoot positions, which ensures that the sample is completely dispensed. There are many manufacturers offering a complete range of volumes in addition some have available a selection of pipettes with adjustable volumes. 

Since the Seralyzer system partly requires the use of diluted serum or plasma, a pipette system or a dilutor unit must be kept ready (Fig. 43). The entire system consists of one each 30 pi and 100 pi air displacement micro-pipette, a... 

Determination of C02.—Dilute 10 c.c. of the mash to 25 c.c. in a measuring flask and transfer 10 c.c. of the diluted liquid by means of a pipette to a small distilling flask which is directly connected to a nitrometer. To the solution add about 0-2 g. of yeast made into a cream with a little water and then at once displace the air by passing in carbon dioxide from above through a tube which does not dip into the liquid. Close the delivery tube by means of stop-cock or spring clip, fill the nitrometer with water saturated with carbon dioxide, and allow... 

If the sample needs to be sealed in an atmosphere of nitrogen, the inlet of the protecting tube is connected to a low-pressure supply of the gas when the syringe or pipette has been withdrawn. When all the air has been displaced the tube may be slowly withdrawn and the ampoule sealed. Filled ampoules containing volatile samples should be thoroughly chilled in a suitable cooling bath... 

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