Standards Preparation: How to prepare Orion calibration standards by serial dilution

Learn what a serial dilution is and review the basic lab equipment needed, including volumetric glassware, pipettors, graduated cylinders, and graduated pipettes for the preparation process.

Use the dilution formula V1C1=V2C2 to determine the volumes needed for creating 100 ppm, 10 ppm, 1 ppm, and 0.1 ppm ammonia standards from a 1000 ppm stock solution, plus a 2 ppm check standard.

Using a 100 mL volumetric flask, transfer 10 mL of the 1000 ppm stock solution from a clean beaker into the flask using a clean pipette, then fill to the volumetric line with deionized water and mix by inverting.

Starting from the 100 ppm solution, create a 10 ppm dilution using the same volumetric technique with a fresh clean beaker and glassware while maintaining consistent lab practices to minimize contamination.

Document the opening date of the stock solution and the creation date of each serial dilution. Continue preparing the 1 ppm and 0.1 ppm standards following the same clean technique and record-keeping procedures.

Create a 2 ppm check standard by diluting 2 mL of the 100 ppm solution to 100 mL total volume using a volumetric flask. This mid-range standard validates calibration accuracy within 10 percent recovery.

Run the 2 ppm check standard after calibration to verify the electrode is working correctly and the calibration is valid. If recovery is not within 10 percent, troubleshoot the electrode or reassess the serial dilution quality.