Nutrient Analysis Using Colorimetry Torrey Lindbo SWRP, PSU-ESR

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

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

Colorimeter Color change measured using colorimeter Colorimeter determines amount of transmitted light absorbed by sample Transmitted Light Detector Light source Tungsten Lamp Lens Sample Vial Filter

Light Paths Refracted Absorbed Transmitted Reflected Absorbance (A) is logarithmically related to transmittance (T) A = - log T

Beer’s Law A = εLc Where, A = absorbance ε = absorptivity; experimentally derived constant for each substrate L = path length of light through sample c = concentration of substance in solution

Beer’s Law Concentration (c) A = εLc Absorbance (A) Slope = εL

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 I/ READ DR/850 Colorimeter TIMEREnter

Hach DR/700 Colorimeter Each test requires a “module” that needs to be turned to the correct program number. Example: Nitrate module = Low range procedure = program High range procedure = program Need to perform Lamp Intensity Adjustment Use film canister as light cover

“Zeroing” the Colorimeter Concentration (c) Beer’s Law A = εLc c = εL / A A Slope = εL (constant) Sample Absorbance Blank Absorbance

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

Hach Glassware Cleaning is crucial first step Acid Washing Soak in ~10% acid bath Choose acid depending upon tests (i.e., don’t use nitric acid if you’re testing for nitrate) Rinse thoroughly with DI water Etching on Hach glassware may erode after long soaks 10 mL 20 mL 25 mL

Colorimetric Analyses Soluble Reactive Phosphorus (SRP) Total Phosphorus Ammonia Nitrogen Nitrate Nitrogen Chlorine

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

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

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

Nitrate Nitrogen Vigorous Shaking 2 Procedures: Low (< 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.

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

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

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

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

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

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

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

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

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

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