PASCO EZ-2337 User Manual

Phosphate ezSample™ (EZ-2337)

0.20- 8.00 ppm (mg/L) PO

Instrument Set-up

The PASPort Water Quality Colorimeter is specifically designed to support PASCO’s ezSample test kits. Set up
the PASPort Water Quality Colorimeter according to the equipment instructions. In the data display software,
choose the appropriate test routine. Set your display to read both high and low values. If the readings are above 1.0
mg/L then use the Phosphate High reading (phosphate (H)). If the readings are below 1.0 mg/L, use the Phosphate
Low reading (phosphate (L)). Readings at 1.0 mg/L are accurate on both scales.

The calibration procedure is listed on the equipment instruction card.

Safety Information

Read the Material Safety Data Sheet (MSDS) before performing this test procedure. Wear safety glasses and
disposable gloves.

Test Procedure

1. Fill the sample cup to the 25 mL mark with the
sample (fig 1).

2. Add 2 drops of A-8500 Catalyst Solution (fig 2).
Cap the sample cup and shake it to mix the
contents.

3. Immediately snap the tip by pressing the ampoule
against the side of the cup. The ampoule will fill
leaving a small bubble to facilitate mixing (fig 3).

4. Mix the contents of the ampoule by inverting it several times, allowing the
bubble to travel from end to end each time. Wipe all liquid from the exterior of
the ampoule.

5. Wait 3 minutes for color development.

6. Use the PASPort Water Quality Colorimeter to measure the concentration value
of the ampoule.

Test Method Description

The phosphate ezSample test method employs the stannous chloride chemistry.1 In an acidic solution,
orthophosphate reacts with ammonium molybdate to form molybdophosphoric acid, which is then reduced by
stannous chloride to the intensely colored molybdenum blue. The resulting blue color is directly proportional to
the phosphate concentration. Results are expressed in ppm (mg/Liter) PO4
and other polyphosphates) and organically bound phosphates do not respond to this test. Sulfide, thiosulfate, and
thiocyanate will cause low test results.

Accuracy and practical detection limit (PDL)

The lower limit of the stated test range is the “Practical Detection Limit (PDL).” Accuracy may be compromised if
test results are outside of the test range. Test results obtained at or below the PDL should be further confirmed for
best accuracy.

Reference

1. Method 4500-P D. APHA Standard Methods, 20th ed., p. 4-145, (1998)

2-

4

Figure 1

Figure 3

2-

. Condensed phosphates (pyro-, meta-

Figure 2

1 012-10112E

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