QbD1200 Preparing Reagent Solution

The QbD1200 TOC Analyzer uses a mixture of phosphoric acid (to aid in removal of CO2 from solution) and ammonium persulfate (to aid in oxidizing organic compounds). This mixture is added to each sample and standard prior to oxidation, is used to dilute samples (if needed), and rinse sample lines. Under normal use conditions, a user will prepare a new reagent solution with each tray of samples to measure.

Preparing the reagent solution is very simple. The reagent stock solution is a concentrated mixture of acid and persulfate; a working solution is simply a 1:100 dilution of the stock solution. The stock solution can either be purchased from Hach (PN 9459400), or users can prepare their own (see instructions on reverse).

It is important to note: the final concentration of both acid and persulfate in the 1:100 dilute reagent solution far exceeds of what is required to oxidize organics within the concentration range specified for the instrument and remove CO2 from the sample solution when the carrier gas is flowing. This means that a high degree of precision is not required to prepare the 1:100 dilution.

To prepare the reagent solution, follow these three simple steps:

qbd1200 reagents


  • As always, when preparing solutions used for very sensitive measurements (ppb levels), use clean glassware and ultrapure water (< 50 ppb TOC).
  • A fresh reagent solution is usually prepared each day.
  • Make sure there is enough reagent solution to complete a tray of samples when autosampler is running and instrument is left unattended.

Preparing Reagent Stock Solution Concentrate

If you choose not to purchase stock solution, you can easily prepare your own.

Reagent stock solution concentrate is hazardous. Use caution and proper PPE. Always wear safety glasses and gloves when handling chemicals.

qbd1200 toc analyzer chemicals

Step 1: Weigh 250 g (± 1%) of reagent grade ammonium persulfate, transfer to 1 L volumetric flask.

qbd1200 toc reagent grade ammonium

Step 2: Fill flask approximately half full with ultrapure water.

qbd1200 ultrapure water

Step 3: Measure 50 mL reagent grade phosphoric acid in a graduated cylinder, transfer to same flask above.

qbd1200 reagent grade phosphoric

Step 4: Fill flask to mark with ultrapure water, add stopper to flask, invert flask repeatedly until contents are completely dissolved.

qbd1200 reagent ultrapure



  • Prepared Reagent Stock Solution concentrate should be kept refrigerated and protected from light in a clean amber bottle.

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