DPD COLORIMETRIC (For Free and Total Chlorine)
- Page ID
- 80377
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Determining rates of Chloramine breakdown using different methods through measuring residual Clorine using DPD Colorimetric
Preparing Standard Solutions
- Introduction:
- What is DPD?
DPD is N,N-diethyl-p-phenylenediamine – The amine DPD reagent reacts with chlorine stoichiometrically to from a Würster dye and an imine.
- Spectrometer Analyzing: ( per slide 35)
Making a Calibration Curve
Beer’s law states that A = ε b c
ε = molar absorptivity (how “potent” the dye is)
b = cell path length
c = concentration
Since the molar absorptivity and the path length are the same for all readings, only the concentration changes. Thus, if the concentration doubles, so should the absorbance ( A). This is a linear relationship.
If calibration data is not linear (r < .995), than there is a problem in either the procedure or calibration stsandard.
- Procedure
- Calibrating Spectrometer:
(Per the APA instruction, we can calibrate using Potassium Permanganate Std or Chlorine. The Powerpoint suggested Permanganate, so I think Potassium Permanganate is the way to go ?
https://www.hach.com/potassium-permanganate-standard-solution-0-1-n-1-l/product?id=7640200693# )
- Obtain 10 mL of 1N Potassium Permanganate, dilute solution to 1L. This should result in a 31.6 ppm solution
- Prepare solutions with range from ~0.06 ppm to 4.7 ppm according to the table
|
Volume of 31.6 ppm solution (mL) |
Final Volume (mL) |
Final Concentration (ppm) |
|
2 |
1000 |
0.0632 |
|
5 |
1000 |
0.158 |
|
10 |
1000 |
0.316 |
|
20 |
1000 |
0.632 |
|
50 |
1000 |
1.58 |
|
10 |
100 |
3.16 |
|
15 |
100 |
4.74 |
If we can afford 1g/L Potassium Permanganate (which is more ideal since dilute 2mL into 1L might result in large error)
https://www.hach.com/potassium-perma...10&callback=qs
Then, dilute 10 mL of such solution into 1L. Then follow the Table.
|
Volume (mL) |
Final Volume (mL) |
Final Concentration (ppm) |
|
5 |
1000 |
0.05 |
|
1 |
100 |
0.1 |
|
5 |
100 |
0.5 |
|
7 |
100 |
0.7 |
|
10 |
100 |
1 |
|
20 |
100 |
2 |
|
50 |
100 |
5 |
- Obtain 7 containers with equal amount of DPD. Pour solutions (keep in the dark to avoid sunlight) into containers (label as needed).
- Set up Spectrometer per slide 30.
Making a Calibration Curve Zeroing the Spectrophotometer Zeroing the Spectrophotometer. Zero the spectrophotometer using the calibration blank, DI water – Make sure the spectrophotometer is set to 515 nm. If this is not possible, use a wavelength between 515-540 nm. – Zero with the same water that was used in creating the calibration standards. – Pour the water from the flask into a clean sample cell. Wipe the cell clean of fingerprints. – Align the reference mark to the light source (or as appropriate), and zero the spectrophotometer.
- Collect and analyze data.