Oxygen Demand, Chemical
Oxygen Demand, Chemical
OxygenCOD_None_Mid_RCD_Eng_Ody.fm Page 5 of 8
Accuracy Check
Standard Solution Method
1. Check the accuracy of the 3 to 150 mg/L range with a 100 mg/L standard.
Prepare by dissolving 85 mg of dried (120 °C, overnight) potassium acid
phthalate (KHP) in 1 liter of deionized water. Use 2 mL as the sample
volume. The result should be 100 mg/L COD. Or dilute 10 mL of 1000-mg/L
COD Standard Solution to 100 mL to produce a 100-mg/L standard.
• To adjust the calibration curve using the reading obtained with the
100 mg/L COD standard solution, touch
Options on the current program
menu. Touch
Standard Adjust.
• Touch On. Touch Adjust to accept the displayed concentration. If an
alternate concentration is used, touch the number in the box to enter the
actual concentration, then touch
OK. Touch Adjust.
2. Check the accuracy of the 20 to 1,500 mg/L range by using either a 300 mg/L
or 1000 mg/L COD Standard Solution. Use 2 mL of one of these solutions as
the sample volume; the expected result will be 300 or 1000 mg/L COD
respectively. Or, prepare a 500 mg/L standard by dissolving 425 mg of dried
(120 °C, overnight) KHP. Dilute to 1 liter with deionized water.
• To adjust the calibration curve using the reading obtained with the
300 mg/L or 1000 mg/L COD standard solution, touch
Options on the
current program menu. Touch
Standard Adjust.
• Touch On. Touch Adjust to accept the displayed concentration. If an
alternate concentration is used, touch the number in the box to enter the
actual concentration, then touch
OK. Touch Adjust.
3. Check the accuracy of the 200 to 15,000 mg/L range by using a 10,000 mg/L
COD standard solution. Prepare the 10,000 mg/L solution by dissolving
8.500 g of dried (120 °C, overnight) KHP in 1 liter of deionized water.
Use 0.2 mL of this solution as the sample volume; the expected result will be
10,000 mg/L COD.
• To adjust the calibration curve using the reading obtained with the
10,000 mg/L COD standard solution, touch
Options on the current
program menu. Touch
Standard Adjust.
• Touch On. Touch Adjust to accept the displayed concentration. If an
alternate concentration is used, touch the number in the box to enter the
actual concentration, then touch
OK. Touch Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
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