How do I dilute the primary Chlorine Standard Solution (Catalog No. 1426810 or 1426820) to prepare calibration standards for calibrating my Pocket II Colorimeter for Chlorine (Catalog No. 5870000)?

Document ID

Document ID TE493

Published Date

Published Date 27/05/2017
Question
How do I dilute the primary Chlorine Standard Solution (Catalog No. 1426810 or 1426820) to prepare calibration standards for calibrating my Pocket II Colorimeter for Chlorine (Catalog No. 5870000)?
Summary
Prepare primary standards to calibrate Pocket Colorimeter II for chlorine
Answer
In order to calibrate a Pocket Colorimeter II for chlorine, several primary standards (typically 5 to 7) at different concentrations will need to be prepared. The calibration standards should span the full concentration range of the test. For example, if using a Hach method that measures from 0 - 2.00 mg/L, prepare calibration standard concentrations that span this range. For example, 0.3, 0.6, 0.9, 1.2, 1.6, and 1.9 mg/L Cl2.

The following procedure is one way to accurately prepare 6 chlorine calibration standards from a Hach Chlorine Standard Solution:

Required Items:
-Chlorine Standard Solution, 50-75 mg/L (actual concentration on label): Flasks (Catalog Number 1426810)
 -Volumetric, class A, glass, 200-mL: Catalog No. 1457445
-Pipets, volumetric, class A, glass:
                       1 mL: PN 1451535
                       2 mL: PN 1451536
                       3 mL: PN 1451503
                       4 mL: PN 1451504
                       5 mL: PN 1451537
                       6 mL: PN 1451506
Pipet Filler: Catalog No. 1218900
Deionized water: Catalog No. 27256

Diluting the Chlorine Standard Solution:
1. Fill a 200-mL volumetric flask approximately half full with deionized water. Open a chlorine standard solution ampule.
2. Pipet 1 mL of the chlorine standard solution into the flask.
3. Fill the flask to the mark with deionized water, stopper, and invert repeatedly to mix. This makes an approximately 0.3 mg/L Cl2 standard solution. (Use the equation below to find the exact concentration.)
4. Prepare additional standards by repeating the above steps, substituting 2, 3, 4, 5, and 6 mL of the chlorine standard solution for the 1 mL shown in step 3.

Calculating the Concentration: Because Chlorine Standard Solutions are difficult to prepare accurately, Hach targets a concentration range, in this case 50 to 75 mg/L, and then determines the actual concentration by amperometric titration. The actual concentration is on the label. Use this concentration to calculate each of your calibration standard concentrations. Multiply the concentration from the Chlorine Standard Solution label by the multipliers in the following table:

Standard #    Pipet volume (mL)    Multiplier
     1                         1                        0.005
     2                         2                        0.01
     3                         3                        0.015
     4                         4                        0.02
     5                         5                        0.025
     6                         6                        0.03 

Diluted concentration = chlorine ampule concentration x multiplier.

Example: the chlorine standard solution value is 63.1 mg/L. One mL was pipetted into a 200-mL flask and diluted to the mark. The concentration of the diluted standard is 63.1 x 0.005 = 0.32 mg/L chlorine. Enter 0.32 in the calibration mode of your Pocket II Colorimeter for standard 1. Measure the absorbance of this standard after adding the DPD reagent.

Note: Use the diluted standard solutions as soon as possible after mixing.

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