Click here to enlarge imageFor this reason, several water quality laboratories have chosen Ratiometric Photometry as their liquid handling quality assurance method in order to produce volume verifications that are quicker, more accurate and immune to environmental conditions. Also, the technology can verify minute volumes with a high degree of accuracy, while providing automated verification and documentation of calibration results to meet federal and state water quality testing standards.
For example, calibration systems based on Ratiometric Photometry can perform a 10–point calibration in three to four minutes, as compared to gravimetric methods requiring 15 to 60 minutes. This time–saving encourages more frequent pipette calibration (sometimes called interim verification or functional checks), and therefore helps ensure more consistent and reliable pipetting.
No Room for Error
The need for a rigorous calibration process at water quality laboratories is due to the large role that pipettes play in testing for the nearly 100 substances identified as toxic, ranging from microbiological contaminants and metal to radiological constituents, bacteria, viruses and protozoans. A large majority of these tests are highly volume–dependent, requiring the addition of specified volumes of sample and reagents for accurate analysis.
Volume is critical in microbiology tests, for example, because each volume addition has a specified number of bacteria colonies present, and altering this quantity can affect test results.
Consider the impact of using an under–delivering pipette to conduct a test for cryptosporidium or giardia, two potentially lethal microbiological contaminants. If the original dispense volume is just two or three microliters below its target, the results could show the contaminant level to be two or three micrograms less than its actual presence. The sample could be cleared as fit for human consumption when in fact the contaminant level exceeds the maximum permitted by the Environmental Protection Agency (EPA).
Another water quality laboratory process affected by pipetting error is the addition of preservatives to samples, which is required for tests for certain contaminants that break down readily. Adding an inaccurate quantity of preservatives could lead to premature contaminant breakdown and a failure to identify a harmful presence.
Accuracy in pipetting is very important, and this depends not only on the instruments’ mechanical function but also proper pipetting technique. A regular calibration program can minimize the risk of using malfunctioning pipettes in critical tests by quickly identifying pipettes operating outside specified tolerances. Yet pipetting technique can also affect delivered volume, and operator training is necessary.
Pipette technique training can help technicians hone their pipetting skills for greater accuracy and precision. Ratiometric Photometric calibration systems immediately produce volume verification, providing users with instant verification of proper pipetting technique and ongoing training.
About the Author
Trena M. Penney is Technical Marketing Representative at ARTEL, providing liquid delivery process support for the customers in pharmaceutical and biotechnology laboratories. Penney has received awards from the American Society of Microbiology for research regarding the prevalence and detection of E. coli. ARTEL is a worldwide provider of equipment for low–volume liquid delivery measurement and quality assurance. Website: www.artel–usa.com