Molecular Biology Problem Solver 9. Sách được nhiều nhà khoa học có uy tín, nhiều kinh nghiệm trong nghiên cứu thực nghiệm trình bày những vấn đề thường hay phát sinh trong phòng thí nghiệm. Do vậy mà sách không trình bày các protocol hay quy trình như các sách khác, thay vào đó các tác giả sẽ trình bày các vấn đề nhằm giúp giúp đọc giả: Tự nâng cao khả năng chẩn đoán nguyên nhân khi gặp các vấn để về kỹ thuật, quy trình, hóa chất, thuốc thử trong quá trình thực nghiệm trong phòng thí. | Nosecone Maximum Volume Tip Ejector Sleeve dottom Component or Lower Housing Figure Pipette anatomy. Reproduced with permission from Brinkmann Instruments Inc. you can reduce the amount of time redoing experiments if a problem is found. How Can You Monitor the Performance of a Pipette All of the internal components of the pipette must be tested to determine that they are fully first thing that should be checked is the free movement of the piston. The piston should move up and down very smoothly. Next verify that the internal parts are working properly by performing a leak test. Although this test does not measure accuracy and reproducibility it is a quick and easy determination of the proper functioning of the internal parts. Please remember that this type of test will only ensure that the internal parts of the pipette are not contributing to a leak in the pipette or tip system. It does not test if the pipette is delivering the specified volume set on the volume display. Two methods to detect leaks are described below. These tests are appropriate for pipetted volumes greater than 10ml smaller volumes do not displace a sufficient amount of air to visually check the performance of the pipette. How to Properly Use and Maintain Laboratory Equipment 71 The first and easiest approach is to set the pipette to the maximum rated volume attach a pipette tip aspirate liquid into the pipette tip and hold the pipette in a vertical position for 15 seconds. If the liquid does not drip out the fit of the seals and Orings around the piston is good and there is no need to replace them. A leak will appear as a droplet on the pipette tip which indicates that the pipette needs to be serviced. A second method is to monitor the stability of a column of liquid in an attached 20 cm segment of PVC tubing. Hold the pipette vertically aspirate the liquid colored liquid can be used and mark the meniscus level on the tubing. Wait one minute then check if the meniscus level .
