ISO Approves Photometry Standard for Liquid Volume Measurement

The International Organization for Standardization (ISO, www.iso.org) has approved the use of the photometric method for liquid delivery performance verification. Artel (Westbrook, ME, www.artel-usa.com), a manufacturer of precision testing and calibration systems for liquid handling instruments, uses the photometric method to calibrate pipettes and automated liquid handlers.

This method, standardized in ISO 8655-7, uses light absorption to verify volume accuracy. The traditional gravimetric method, which uses a balance to measure liquid volume, is difficult to implement at very low volumes and cannot be used with high-throughput liquid handlers. Artel uses a dual-dye approach to photometry, using two proprietary solutions to avoid the accuracy problems often associated with low-volume measurement verification. According to Artel?s data, in the last ten years, more than 18 million pipettes and 16,000 automated liquid handlers have been sold in the United States. At any given time, as many as 30% of these may be malfunctioning. "Liquid delivery failure is generally silent and random," said Kirby B. Pilcher, president of Artel. "The best way to prevent failure is to have a robust calibration program."