Tech Note 1103 Detail

Water Quality Colorimeter reports non-zero concentrations with a clear ampoule.

Affected Products:

PS-2179 Water Quality Colorimeter

Problem/Symptom:
Water Quality Colorimeter reports non-zero concentrations with a clear ampoule.

PASCO Solution:

During Calibration

Immediately after pressing the green calibration button with a clear calibration ampoule, the transmittance should be 100.0 and the absorbance should read 0.000; however, the reported concentrations of the ions will not be zero, despite there not being any ions in the clear calibration ampoule, which contains only distilled water. There are two reasons for this:

  1. "0.0" concentration is outside the valid range for any of the tests.
  2. The calibrations are based on the assumption that the test dyes are present and fully developed, which may absorb some light even when the concentration of the ion of interest is low.

Ion

Stated Ion Concentration for Distilled Water
[mg/L]

Valid Test Range
[mg/L]

Shelf Life
[months]

Test EZ Test Test Code

Ammonia (Low)

-0.04

0.1-1.0 8 Salicylate EZ-2334 K-1403P

Ammonia (High)

-0.1

1.0-3.0 8 Salicylate EZ-2334 K-1403P

Chlorine

-0.5

0.4-5.0 12 DPD EZ-2339 K-2513P

Fluoride

7.3

(OBSOLETE) - SPADNS - K-4003P

Iron

0.4

1.5-8.0 24 Phenanthroline EZ-2331 K-6203P

Phosphate (Low)

-0.09

0.2-1.0 20 Stannous Chloride EZ-2337 K-8513P

Phosphate (High)

-.3

1.0-8.0 20 Stannous Chloride EZ-2337 K-8513P

Sulfate

9

(OBSOLETE) - Turbidimetric - K-9203P

Nitrate (Low)

0.02

0.25-1.0 12 Zinc Reduction EZ-2333A K-6913P

Nitrate (High)

0.08

1.0-2.0 12 Zinc Reduction EZ-2333A K-6913P

During Measurement

It is also possible to get negative or otherwise erroneous values for the concentration during measurement. Check the following:

  1. The measurement chamber should be clean.
  2. The ampoules must be nearly full and free of air bubbles for both calibration and measurement.
  3. The concentration of the ion of interest being measured must be in the range of sensitivity of the test.
  4. The test kits should not have expired.
  5. The solutions must be left to react for the amount of time specified in the test kit.
  6. The colorimeter is functioning properly.*

* To verify that your system is performing properly, mix or test a standard solution of a concentration that is in the recommended range of the test, checking that the conditions 1-5 above are satisfied. If the water quality colorimeter fails the test, please contact Teacher Support to start a return on the unit.

Creation Date: 08/23/2010
Last Modified: 05/9/2014
Mod Summary: