Nutrient Analysis Using Colorimetry

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Nutrient Analysis Using Colorimetry

• Torrey Lindbo
• SWRP, PSU-ESR

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Safety Equipment

• Gloves
• Goggles
• Material Safety Data Sheets
• Other Considerations
• Alcohol Hand Wash
• Table or Tarp (spill prevention)

3
Colorimetry

• Colorimetry method for quantifying the
  concentration of a chemical constituent by
  analyzing change in color
• Based on color change for standard solutions of
  known concentration
• Light usually filtered to specific wavelength
• Visible Light Spectrum ROYGBIV
• Red 700 nm
• Violet 400 nm

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Colorimeter

• Color change measured using colorimeter
• Colorimeter determines amount of transmitted
  light absorbed by sample

Transmitted Light Detector
Lens
Filter
Sample Vial
Light source Tungsten Lamp
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Light Paths
Absorbance (A) is logarithmically related to
transmittance (T) A - log T
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Beers Law

• A eLc
• Where,
• A absorbance
• e absorptivity experimentally derived constant
  for each substrate
• L path length of light through sample
• c concentration of substance in solution

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Beers Law
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Hach DR/850 Colorimeter

• Has pre-programmed filters and calibration curves
• Cap doubles as light cover
• Sample color change compared to blank what
  ZERO looks like
• Blank may be stream sample with no reagent added,
  or it may be deionized water with reagent

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Hach DR/700 Colorimeter

• Each test requires a module that needs to be
  turned to the correct program number. Example
• Nitrate module 50.01
• Low range procedure program 50.07.1
• High range procedure program 50.05.1
• Need to perform Lamp Intensity Adjustment
• Use film canister as light cover

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Zeroing the Colorimeter
Slope eL (constant)
Sample Absorbance
Beers Law A eLc c eL / A
A
Blank Absorbance
Concentration (c)
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Other DR/850 Features

• Timer
• Beeps when reaction periods for tests are over
• Limits colorimeter use no other tests can be run
  while timer is running
• Store
• Can store up to 99 readings
• Download
• Hach makes infrared computer interface

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Hach Glassware

• Cleaning is crucial first step
• Acid Washing
• Soak in 10 acid bath
• Choose acid depending upon tests (i.e., dont use
  nitric acid if youre testing for nitrate)
• Rinse thoroughly with DI water
• Etching on Hach glassware may erode after long
  soaks

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Colorimetric Analyses

• Soluble Reactive Phosphorus (SRP)
• Total Phosphorus
• Ammonia Nitrogen
• Nitrate Nitrogen
• Chlorine

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Phosphorus

• Clean glassware crucial
• SRP test is quick and easy (2 minute reaction
  time) good for flexibility with colorimeter
  sharing
• Total Phosphorus requires digestion
• Hot plate
• Strong Acid and Base
• Requires fume hood
• This test should be run in the lab

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Phosphorus

• Equipment Needed
• 3-5 vials for samples 1 for blank
• PhosVer3 reagent powder pillows
• Non-toxic waste container
• DR/850 Colorimeter
• Procedure Overview
• 10 mL sample reagent in each sample
• 10 mL sample and no reagent for blank
• Shake and wait 2 minutes

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The Meniscus

• Meniscus the curved, lens-like surface of water
  in glass
• Glass has a negative charge that attracts the
  positive H from water
• Read volumes from bottom of meniscus

10 mL
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Nitrate Nitrogen

• Vigorous Shaking
• 2 Procedures Low (lt 0.5 mg/L) and High (0.6 20
  mg/L) Range
• Toxic waste Cadmium (heavy metal) used to
  reduce nitrate
• Time requirement (i.e., Low Range takes 20
  mins.)
• Shake 3 min, wait 2, add reagent 2, shake, wait
  15 min.

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Low Range Nitrate Procedure

• Equipment Needed
• 6-10 vials for samples 1 for blank
• NitraVer6 and NitriVer3 reagent powder pillows
• Low Range Procedure
• 30 mL sample NitraVer6 in each sample (shake 3
  mins)
• 10 mL treated sample NitriVer3
• 10 mL sample and no reagent for blank

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High Range Nitrate Procedure

• Equipment Needed
• 3-5 vials for samples 1 for blank
• NitraVer5 reagent powder pillows
• Toxic waste container
• High Range Procedure
• 10 mL sample NitraVer5 in each sample
• 10 mL sample and no reagent for blank

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Ammonia Nitrogen

• Timing measure each sample immediately after
  reaction time
• Time table stagger reagent addition to each vial
  by 1 minute
• Blank is deionized water reagents (only need 1
  blank)
• DI water source must be PURE

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Ammonia Nitrogen

• Equipment Needed
• 3-5 vials for samples 1 for blank
• Ammonia Salicylate and Ammonia Cyanurate reagent
  powder pillows
• Toxic waste container
• Procedure Overview
• 10 mL sample reagents in each sample
• 10 mL DI water reagents for blank

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Chlorine

• Sample needs to be collected in glass
• Best measured immediately in field

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Chlorine

• Equipment Needed
• 3-5 vials for samples 1 for blank
• DPD chlorine reagent powder pillows
• Non-toxic waste container
• DR/850 Colorimeter
• Procedure Overview
• 10 mL sample reagent in each sample
• 10 mL sample and no reagent for blank
• Shake and wait 2 minutes

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Waste Management

• Appendix A, pages 1-3
• Collection
• Plastic Bottles work fine
• Clearly Labeled
• Non-Toxic, Ammonia and Nitrate all should be
  stored separately
• Organization
• Callister Carrier cardboard 6-pack container

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Non Toxic Waste

• DO, pH, Alkalinity, SRP, Chlorine
• Disposal
• Neutralize pH (baking soda)
• Pour down drain with excess water

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Ammonia Waste

• Several constituents of concern
• Maximum concentrations in manual
• No way to safely reduce volume
• Must be disposed of at a hazardous waste facility
• METRO or PSU Waste Consortium
• Talk to your local waste handler, administrator
  or local college for other disposal sites

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Nitrate Waste

• Cadmium is only constituent of concern
• Manual has instructions for precipitating heavy
  metals
• Most teachers bring entire waste container to
  hazardous waste facility