An insight into pipettes and pipetting

The pipettes are an important instrument used in laboratories to transfer a calculated amount of liquid.  They are used in analytical chemistry, molecular biology and some medical tests. They are available in many designs and styles differing in precision and accuracy levels. Two types of pipettes which are most commonly used are air displacement pipettes and positive displacement pipettes.

Air displacement pipettes – In this type of pipette, a definite quantity of air remains between the liquid and the piston. They are used for general function with aqueous solutions. There is a piston available inside this pipette which will be enthused to appropriate place when the quantity is set. After pressing the operating button, the piston will drive out same quantity of air which is set. The operating push button will be released only after submerging the tip into the liquid. It will create a fractional vacuum and the specific quantity of liquid is aspirated into the tilt. When the button is pushed to the first stop another time, the air bestows the liquid. To vacant the tip totally, the button is pushed to the second stop. There are many factors which may influence the precision of air displacement pipettes like density, temperature and altitude, and needs to be taken care of.

Positive displacement pipettes – These pipettes are generally used for volatile and high viscosity liquids. The special thing about this pipette is that the piston is in express contact with the liquid. Its tip contains a disposable needle, which will help in displacing the solution without any problem. The main advantage of this pipette is that it is the most accurate in performance. However, it is very expensive and cannot be used for general purposes.

There are many points which need to be considered when using a pipette. One should mop the pipette with ethanol daily to remove the dirt. Make sure that the amount is in specific range. For maximum accuracy, the tip, liquid and pipette should be reserved at equal temperature. It is recommended to use good quality tips made from infectivity-free polypropylene for the pipettes. It is good to pre-rinse the tilt 3 to 4 times with the fluid to be used; this will increase the accuracy when one is making use of positive displacement tips. Do not revolve the pipette on side when liquid is present in its tip; the liquid will go inside and pollute it.  If the pipettes are used daily, calibration should be checked every three months.

You can get more information about Pipettes by visiting Dispensers Pasteur Pipettes