Phosphates for Hach DR2000 and DR2800

Acid Persulfate Digestion Method (USEPA Accepted for Reporting, Method Number 8048)

DUE TO THE NECESSITY OF BOILING SAMPLES, START THIS TEST AS SOON AS POSSIBLE.

WEAR GLOVES AND EYE PROTECTION AT THIS STATION.

Turn on hotplate to preheat to 600 before beginning tests. 

1.  Samples will be poured into pre-cleaned blue capped centrifuge tubes marked with a P at the fill station.  Pour 25 mL of each sample into a pre-cleaned 50 mL Erlenmeyer flask.  Mark the flask with the sample number using a pencil.  Place the tubes back into the trays in order for later.

2.  Add the contents of one Potassium Persulfate Powder Pillow (marked with a 1) from the top right desk drawer to the Erlenmeyer

flask.  Cut the bag with scissors.  Swirl to Mix.

3.  Using the dropper attached to the lid, add 2.0 mL of 5.25 N Sulfuric Acid Solution to the flask.  Each dropper full is 1.0 mL, as designated on the dropper.  If a spill occurs, sprinkle baking soda

over it and wipe up with a small disposable sponge.

4.  Place the flask on the preheated hot plate set to 600.  Allow the sample to boil 30 minutes.

-  Monitor the boiling flasks to be sure the volume remains near 20 mL. 

-  Do not allow the flasks to boil to the point of being dry.        

Carefully add water to the flasks using the DI water bottle as needed.

5.  Carefully move the flask with tongs from the hotplate after 30 minutes and place on the metal cooling tray to cool to room temperature. 

6.  Once cooled, add 2.0 mL of 5.0 N Sodium Hydroxide Solution to the flask, again using the dropper on the lid.  Swirl to mix the solution. 

7.  Pour the sample from the flask into its original blue capped tube.  Rinse the flask with a small amount (about 5 mL) of DI water and fill the tube to the

 25-ml mark again.

8.  Turn ON the DR2000 and enter the code for reactive

phosphorus  (490 for mg/L of PO₄^3-).  Be sure the wavelength dial is set to 890. 

9.  Fill two sample cells with 10 mL of the boiled sample.  Set the first cell aside for a blank.  Label the cells with pencil with their sample numbers. 

10.  Add the contents of 1 PhosVer 3 Powder Pillow to the second prepared sample and shake immediately to mix.  Be sure to empty the entire packet, especially the corners.

11.  Allow a 2-minute reaction period.  Use the timer at

the station.  While reaction period is occurring, use an alcohol

swab, then Kimwipe, to clean fluid and finger prints off the cells.

12.  When the 2-minute period is over, place the blank in the sample holder with the writing facing left.  Cover with light shield.  Press ZERO, wait for 0.00 to be displayed.  Remove the blank and replace it with the prepared sample cell.  Press READ and record the reading on the phosphates data sheet. 

13.  The samples will also be tested in the Hach DR 2800 spectrophotometer. 

            -From the Main Menu, choose Stored Programs.

            -Choose to type in the program, type 490 and hit start.

            -Put the blank sample cell in with the fill line facing right, cover with protective cover,     and press Zero.

            -Put the prepared sample cell in with the fill line facing right, cover with protective cover,            and press Read.  Record this number.  Repeat with each sample.

14.  When finished with a sample, discard the liquid from the blank and measured sample into the designated waste container.  Place the sample cells, flasks, and blue capped tubes into the plastic tub labeled USED PHOSPHORUS GLASSWARE.