The HI746-25 are high quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Iron Low Range Checker® HC. These reagents follow the TPTZ Method in which the reaction between iron and reagents causes a violet tint in the sample. By simply adding the packets of HI746-25 reagents to the sample, the reaction will take place and the HI746 will determine the concentration from the color that is produced. The results will be displayed in ppb of iron. These reagents are designed to be used with samples that have an expected range of 0 to 999 ppb iron.