How does the QbD1200 Auto-Range function work?
In dissolved phase, ppb is an expression of mass, e.g. 1ppb in 1 liter of water has a mass of 0.000000001kg (assuming the 1 liter of water has a mass of 1kg). If a 1 liter solution containing 100ppb of TOC is diluted with a TOC-free 1 liter solution, then the resultant TOC level will be halved, i.e. 50ppb.
The QbD1200 has a measurement range of 0 to 5,000ppb. This range is extended by accurate dilution of the sample to be tested by a factor of up to 20x, utilizing a high-accuracy syringe pump (+/-1% accuracy). Thus the QbD1200 can analyze samples of up to 100,000ppb.
In applications where the TOC level in the samples is expected to be >4,000ppb, the auto-ranging function can be enabled by the user using the configuration settings. First the QbD1200 draws 1mL of One Reagent into the syringe, followed by 1mL of the sample and then 8mL more of One Reagent. The combined solution is then dispensed into UV reaction module, a quick estimation of the TOC level is made to determine whether there is a need for sample dilution. The level of dilution depends on the amount of TOC present in the sample. The auto-range function can be turned off through the QbD1200 menu.