Use of pipettes
One, The best range selection and range setting
1. When the pipetting range is selected from 35% to 100% of the full scale, the best accuracy and repeatability can be guaranteed. Choosing a suitable range can increase the pipetting accuracy by 1%. Try to avoid setting the pipette range below 10% of the maximum value.
2. When setting the gear-controlled pipette range, always keep [down" to the required range. When adjusting from a small range to a large range, turn the adjustment knob to a position exceeding 1/3 of the required range, and then return to The accurate position of the required range can reduce the impact of mechanical backlash or gear sliding.
Two, The depth and angle of immersion
1. Immersion of the tip into the proper depth can increase the accuracy by 5%. If the tip is immersed too deeply, it will suck more liquid. On the contrary, if it is immersed too shallowly, air will be sucked in.
The recommended tip immersion depths for various types of pipettes are as follows:
2. The angle of the handheld pipette will also affect the accuracy. Ensure that the deviation from vertical does not exceed 20° during liquid suction or discharge, which can increase the accuracy by 2.5%.
Three, rinse
Rinsing is a quick and easy way to increase the accuracy of pipetting up to 0.2%. why? Because the liquid may remain on the inner wall of the tip to form a liquid film, the error value obtained will be less than the theoretical value. For better pipetting accuracy, after installing a new pipette tip, rinse the pipette tip with the same sample 2 to 3 times, so that the film will remain fairly constant, thereby improving the accuracy and repeatability of pipetting .
Fourth, aspiration
Ensuring the consistency of aspiration can increase the accuracy by 5%. When pipetting different samples, use a consistent pipetting rhythm. The speed of pressing or releasing the button should be stable and consistent, and the force to reach the first stop point should be consistent. Fast or uneven liquid aspiration can cause liquid splashes, aerosols, contamination of the sleeve, and loss of sample volume.
Forward lotion: Normal liquid suction mode. When operating, press the button to the first level to suck liquid and release the button. When discharging liquid, first press the first level to discharge most of the liquid, and then press the second level to discharge the remaining liquid.
Reverse liquid suction: When sucking liquid, directly press the button to the second position and then release it, so that more liquid will be sucked in. When the liquid is discharged, just press it to the first position. The more sucked liquid can compensate for the surface adsorption inside the tip, and the reverse sucking method is suitable for viscous liquids such as glycerin.
When sucking liquid, be sure to loosen your thumb slowly and steadily, and never loosen it suddenly, so as to prevent the solution from being sucked in too fast and rushing into the liquid extractor to corrode the plunger and cause air leakage.
In order to obtain higher accuracy, the tip needs to take a sample solution in advance, and then formally pipette, because when sucking serum protein solution or organic solvent, a layer of "liquid film" will remain on the inner wall of the tip, resulting in a small discharge volume And produce errors.
The pipette is strictly prohibited to absorb highly volatile, highly corrosive liquids (such as concentrated acid, concentrated alkali, organic matter, etc.).
Five, liquid separation
Good dispensing skills can also improve accuracy by 1%. You can get better consistency when you touch the wall of the container with the tip during dispensing. Sliding the orifice end of the tip up along the container wall can remove the remaining liquid at the orifice end. The other two techniques are also very suitable for water-soluble (non-viscous) liquids.
