Water Quality Monitoring

Read LaMotte Direct Reading Titrator Manual before proceeding. The Titrator is calibrated in parts per million (ppm) dissolved oxygen.

Steps 1 through 4 below describe proper sampling techniques in shallow water. For collection of samples at depths beyond arm's reach, special water sampling apparatus is required (e.g., the LaMotte Water Sampling Chamber, Code 1060; Model JT-1 Water Samplers, Code 1077; or Water Sampling Outfit, Code 3103).

1. To avoid contamination, thoroughly rinse the Water Sampling Bottle (0688-DO) with sample water.
   
   
2. Tightly cap the bottle and submerge to the desired depth. Remove cap to allow the bottle to fill.
   
   
3. Tap the sides of the submerged bottle to dislodge any air bubbles clinging to the inside. Replace the cap while the bottle is still submerged.
   
   
4. Retrieve the bottle and examine it carefully to make sure that no air bubbles are trapped inside. Once a satisfactory s;ample has been collected, proceed immediately with Steps 5 & 6 to "fix" the sample.
   
   
   • NOTE: Be careful not to introduce air into the sample while adding the reagents in Steps 5 & 6. Simply drop the reagents into the sample. Cap carefully and mix gently.
   
   
   
5. Add 8 drops of *Manganous Sulfate Solution (4167) and 8 drops of *Alkaline Potassium Iodide Azide (7166). Cap and mix by inverting several times. A precipitate will form. Allow the precipitate to settle below the shoulder of the bottle before proceeding.
   
   
6. Use the 1.0 g spoon (0697) to add one level measure of *Sulfamic Acid Powder (6286). Cap and gently shake until the reagent and the preciptate have dissolved. A clear-yellow to brown-orange color will develop, depending on the oxygen content of the sample.
   
   
   • NOTE: Following the completion of Step 6, contact between the water sample and the atmosphere will not affect the test results. Once the sample has been "fixed" in this manner, it is not necessary to perform the actual test procedure immediately. Thus, several samples can be collected and "fixed" in the field, and then carried back to a testing station or laboratory where the test procedure is to be performed.
   
   
7. Fill the titration tube (0299) to the 20 ml. line with the "fixed" sample and cap.
   
   
   • NOTE: If the color of the "fixed" sample is already a very faint yellow, skip to Step 9.
   
   
   
8. Fill the Direct Reading Titrator (0377) with *Sodium Thiosulfate, 0.025N (4169). Insert the Titrator into the center hold of the titration tube cap. While gently shaking the tube, slowly press the plunger to titrate until the yellow-brown color is reduced to a very faint yellow.
   
   
9. Remove the Titrator and cap. Be careful not to disturb the Titrator plunger, as the titration begun in Step 2 will be continued in Step 10. Add 8 drops of Starch Indicator Solution (4170WT). The sample should turn blue.
   
   
10. Replace the cap and Titrator. Continue titrating until the blue color just disappears. Read the test result where the plunger tip meets the scale. Record as ppm Dissolved Oxygen.
    
    
    • NOTE: Each minor division on the Titrator scale equals 0.2 ppm.
      
      
    • NOTE: If the plunger tip reaches the bottom line on the Titrator scale (10 ppm) before the endpoint color change occurs, refill the Titrator and continue the titration. When recording the test results, be sure to include the value of the original amount of reagent dispensed (10 ppm).

*WARNING: Reagents marked with a * are considered hazardous substances. Material Safety Data Sheets (MSDS) are supplied for these reagents. For your safety, read the label and the accompanying MSDS before using.

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