Transcript SWRP Colorimeter and Nutrient Analysis

Nutrient Analysis Using
Colorimetry
Torrey Lindbo
SWRP, PSU-ESR
Safety Equipment
Gloves
Goggles
Material Safety Data Sheets
Other Considerations:
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Alcohol Hand Wash
Table or Tarp (spill prevention)
Colorimetry
Colorimetry: method for quantifying the
concentration of a chemical constituent
by analyzing change in color
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Based on color change for standard
solutions of known concentration
Light usually filtered to specific wavelength
Visible Light Spectrum = ROYGBIV
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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
Filter
Lens
Sample Vial
Light Paths
Absorbance (A) is
logarithmically related
to transmittance (T)
A = - log T
Refracted
Absorbed
Transmitted
Reflected
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
Slope = εL
Absorbance
(A)
A = εLc
Concentration (c)
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
DR/850 Colorimeter
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READ
TIMER
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Enter
Hach DR/700 Colorimeter
Each test requires a “module” that needs
to be turned to the correct program
number. Example:
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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
“Zeroing” the Colorimeter
Sample
Absorbance
Slope = εL
(constant)
Beer’s Law
A = εLc
A
Blank
Absorbance
c = εL / A
Concentration (c)
Other DR/850 Features
Timer
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Beeps when reaction periods for tests are over
Limits colorimeter use; no other tests can be run
while timer is running
Store
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Can store up to 99 readings
Download
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Hach makes infrared computer interface
Hach Glassware
Cleaning is crucial first step
Acid Washing
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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
25 mL
20 mL
10 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
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Hot plate
Strong Acid and Base
Requires fume hood
This test should be run in the lab
Phosphorus
Equipment Needed
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3-5 vials for samples + 1 for blank
PhosVer3 reagent powder pillows
Non-toxic waste container
DR/850 Colorimeter
Procedure Overview
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10 mL sample + reagent in each sample
10 mL sample and no reagent for blank
Shake and wait 2 minutes
The Meniscus
10 mL
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
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.)
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Shake 3 min, wait 2, add reagent 2, shake,
wait 15 min.
Low Range Nitrate Procedure
Equipment Needed:
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6-10 vials for samples + 1 for blank
NitraVer6 and NitriVer3 reagent powder
pillows
Low Range Procedure:
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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:
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3-5 vials for samples + 1 for blank
NitraVer5 reagent powder pillows
Toxic waste container
High Range Procedure:
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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
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Time table; stagger reagent addition to
each vial by 1 minute
Blank is deionized water + reagents
(only need 1 blank)
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DI water source must be PURE
Ammonia Nitrogen
Equipment Needed:
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3-5 vials for samples + 1 for blank
Ammonia Salicylate and Ammonia
Cyanurate reagent powder pillows
Toxic waste container
Procedure Overview:
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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
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3-5 vials for samples + 1 for blank
DPD chlorine reagent powder pillows
Non-toxic waste container
DR/850 Colorimeter
Procedure Overview
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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
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Plastic Bottles work fine
Clearly Labeled
Non-Toxic, Ammonia and Nitrate all should
be stored separately
Organization
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“Callister Carrier” = cardboard 6-pack
container
Non Toxic Waste
DO, pH, Alkalinity, SRP, Chlorine
Disposal
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Neutralize pH (baking soda)
Pour down drain with excess water
Ammonia Waste
Several constituents of concern
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Maximum concentrations in manual
No way to safely reduce volume
Must be disposed of at a hazardous waste
facility
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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