Dear Uthreshwaranath,

The following 4 methods are alternatives for KMNO4 method:

1-

Iodometric Titration

Principle

H2O2 oxidizes iodide to iodine in the presence of acid and molybdate catalyst. The iodine formed is titrated with thiosulfate solution, incorporating a starch indicator.

H2O2 + 2 KI + H2SO4 → I2 + K2SO4 + 2 H2O

I2 + 2 Na2S2O3 → Na2S4O6 + 2 NaI

Scope of Application

This method is somewhat less accurate than the permanganate titration, but is less susceptible to interferences by organics, and is more suitable for measuring mg/L levels of H2O2.

Interferences

Other oxidizing agents will also produce iodine, whereas reducing agents (and unsaturated organics) will react with the liberated iodine. The contribution from other oxidizing agents can be determined by omitting the acid and molybdate catalyst.

Safety Precautions

Concentrated sulfuric acid is a corrosive, hazardous material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

Potassium iodide solution (1% w/v). Dissolve 1.0 grams KI into 100 mLs demineralized water. Store capped in cool place away from light. Yellow-orange tinted KI solution indicates some air oxidation to iodine, which can be removed by adding a 1-2 drops of dilute sodium thiosulfate solution.

Ammonium molybdate solution. Dissolve 9 grams ammonium molybdate in 10 mLs 6N NH4OH. Add 24 grams NH4NO3 and dilute to 100 mLs.

Sulfuric acid solution. Carefully add one part H2SO4-98% to four parts demineralized water.

Starch indicator.

Sodium thiosulfate solution (0.1N).

Apparatus

Analytical balance (+/- 0.1 mg/L)

Small weighing bottle (< 5 mLs)

250 mL Erlenmeyer flask

50 mL buret (Class A)

Medicine dropper

Procedure

Weigh to the nearest 0.1 mg an amount of H2O2 equivalent to a titer of 30 mLs (0.06 grms of H2O2) using a 5 mL beaker and medicine dropper. Transfer sample to Erlenmeyer flask.

Add to Erlenmeyer flask 50 mL of demineralized water, 10 mL of sulfuric acid solution, 10-15 mLs of potassium iodide solution, and two drops ammonium molybdate solution.

Titrate with 0.1 N sodium thiosulfate to faint yellow or straw color. Swirl or stir gently during titration to minimize iodine loss.

Add about 2 mL starch indicator, and continue titration until the blue color just disappears.

Repeat steps 2-4 on a blank sample of water (omitting the H2O2).

Calculation

Weight % H2O2 = (A - B) x (Normality of Na2S2O3) x 1.7 / Sample weight in grams

Where: A = mLs Na2S2O3 for sample; B = mLs Na2S2O3 for blank

References

C. T. Kingzett, Chem. News, 41:76 (1880); 43:161 (1881)

I. M. Kolthoff, Chem Weekblad, 17:197 (1920)

2-

Titanium Oxalate (Spectrophotometric)

Principle

The sample is clarified by treatment with aluminum chloride and sodium hydroxide solution and the hydrogen peroxide reacted with potassium titanium oxalate in acid solution to form the yellow pertitanic acid complex. The colored complex is measured spectrophotometrically at 400 nm.

Scope of Application

This method is suitable for the determination of hydrogen peroxide in aqueous effluents and raw sewage in the range 0.1 - 50 µg/mL (or 0.1 - 50 mg/L) as H2O2.

Interferences

Formation of the peroxotitanium complex is specific to hydrogen peroxide. However, wastewaters possessing a strong yellow background color may affect accuracy. Normal background color can be reduced by filtering the sample, or compensated for by zeroing out a blank of unreacted sample. The method includes a flocculation pretreatment step to remove suspended matter – the AlCl3 - NaOH pretreatment step may be omitted when analyzing clear waters.

Safety Precautions

Potassium titanium oxalate is a toxic material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended.

Concentrated sulfuric acid and sodium hydroxide are corrosive, hazardous materials and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

All reagents should be of analytical reagent grade unless otherwise stated

Potassium permanganate solution (0.1N)

Aluminum chloride solution (484 g/L)

Dissolve 121 g of aluminum chloride hexahydrate in 150 mL of demineralized water. Dilute to 250 mL with demineralized water in a measuring cylinder and mix well.

Potassium titanium oxalate solution (50 g/L)

Dissolve 25 g of potassium titanium oxalate, in 400 mL of demineralized water, warming if necessary. Cool and dilute to 500 mL with demineralized water in a measuring cylinder and mix well.

Warning: Potassium titanium oxalate is toxic and solutions must be handled using a safety pipette or burette.

Sodium hydroxide solution (240 g/L)

Dissolve 60 g of sodium hydroxide in 150 mL of demineralized water, dilute to 250 mL with demineralized water in a measuring cylinder and mix well.

Sulfuric acid solution (1+9)

Slowly add 50 mL of sulfuric acid, d 1.84, with continuous stirring to 450 mL of demineralized water in a 1 liter beaker. Cool.

Note: Safety goggles must be worn when handling concentrated sulfuric acid.

Sulfuric acid solution (1 + 17)

Slowly add 20 mL of sulfuric acid, d 1.84, with continuous stirring to 340 mL of demineralized water in a 1 liter beaker. Cool.

Standard hydrogen peroxide solution (stock) 1 mL = 1000 μg

Add 7.50 mL of hydrogen peroxide solution (275 g/Kg) to a 2 liter volumetric flask, dilute to volume with demineralized water and mix well.

This solution must be standardized as described below on the day of use.

Using measuring cylinders, add 10 mL sulfuric acid solution (1 + 9) and 50 mL of demineralized water to a 250 mL conical beaker. Add potassium permanganate solution (0.1N) dropwise to the appearance of a faint permanent pink color.

Pipette 50.0 mL of hydrogen peroxide solution (stock) into the flask and titrate with potassium permanganate solution (0.1N) to the reappearance of the same permanent pink color. Let the titration obtained be T mL.

Then the concentration of the hydrogen peroxide solution (stock) = ((T x N x 17 x 1000 x 1000 x 1000) / (1000 x 50 x 1000)) μg/mL = T x N x 340 μg/mL

Where N is the normality of the potassium permanganate solution.

Let this concentration be G μg/mL.

Standard hydrogen peroxide solution (working) 1 mL = 100 μg

Pipette 25.0 mL of hydrogen peroxide solution (stock) into a 250 mL volumetric flask. Dilute to volume with demineralized water and mix well.

Then the concentration of the hydrogen peroxide solution (working) = G/10 μg/mL

This solution must be freshly prepared on the day of use.

Apparatus

Spectrophotometer capable of measuring absorption at a wavelength of 400 nm and fitted with 10 mm and 40 mm pathlength glass cells.

Procedure

Preparation of Calibration Graph

From a burette add the volumes of hydrogen peroxide solution (working) shown in the table below into a series of 25 mL volumetric flasks.

Volume of Standard Hydrogen Peroxide solution (working) (ml)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Mass of Hydrogen Peroxide taken (ug)

0.0

1.0 x (G/10)

2.0 x (G/10)

3.0 x (G/10)

4.0 x (G/10)

5.0 x (G/10)

6.0 x (G/10)

Using a safety pipette add 2.5 mL of sulfuric acid solution (1 + 17) and dilute each solution to about 20 mL by adding suitable volumes of demineralized water. Mix well and using a safety pipette add 2.0 mL of potassium titanium oxalate solution (50 g/L). Dilute each solution to volume with demineralized water and mix well.

Measurement of Standard Solutions

Set the spectrophotometer to measure absorption at a wavelength of 400 run and select a pair of 10 mm pathlength glass cells.

Adjust the instrument for zero absorption against demineralized water in one of the cells. Using the other cell measure in turn the absorption of each of the standard solutions.

Subtract the absorption of the standard solution containing no added hydrogen peroxide from that of the remaining standard solutions.

Plot the optical densities against the corresponding hydrogen peroxide content of the standard solutions.

Draw in the line of best fit through the series of points and the origin to obtain the required calibration graph.

Repeat the measurements using 40 mm glass cells for the solutions containing up to 5.0 mL of standard hydrogen peroxide (working) solution.

Preparation and Analysis of Sample Solutions

Fill a 500 mL glass bottle with the sample, if possible directly from the source of supply, by means of a rubber tube passing to the bottom of the bottle. Allow the sample to flush out the bottle for two minutes then withdraw the tube and stopper the bottle.

Pipette into the bottle 1.0 mL of aluminum chloride solution (484 g/L) and 1.0 mL of sodium hydroxide solution (240 g/L) with the pipette tips beneath the surface of the liquid. Allow any surplus sample to overflow from the bottle. Replace the stopper and mix the contents by inverting the bottle several times. Allow the precipitate to settle.

Pipette 20.0 mL of the supernatant liquor from the clarified sample into a clean 25 mL volumetric flask.

Prepare a reagent blank solution by pipetting 20.0 mL of demineralized water into a clean 25 mL volumetric flask.

Treat the sample and blank solutions exactly as described under Preparation of Calibration Graph from "using a safety pipette add 2.5 mL of sulfuric acid solution (1 +17) ..."

Prepare a sample blank solution by pipetting 20.0 mL of the supernatant liquor from the clarified sample into a 25 mL volumetric flask. Add 2.5 mL of sulfuric acid solution (1 + 17) and dilute to volume with demineralized water.

Measure the absorption of the sample solution, the sample blank solution and the reagent blank solution as described. Subtract the absorption of the sample blank solution and the absorption of the reagent blank solution from that of the test solution.

Relate the optical density so obtained to the calibration graph to obtain the weight of hydrogen peroxide. Let this weight be A µg as H2O2.

Calculation

Hydrogen peroxide content (as H2O2) = (A/20) mg/L

Sourcing for Titanium Reagent

Titanium potassium oxalate

Alfa Aesar: (978) 521-6401 http://www.alfa.com/

City Chemical: (800) 248-2436 http://www.citychemical.com/

MP Biomedicals: (800) 854-0530 http://www.mpbio.com/

Pfaltz & Bauer: (203) 574-0075 http://www.pfaltzandbauer.com/

References

Solvay Chemicals, Inc.

3-

Cobalt Bicarbonate Method

Principle

H2O2 reacts with cobalt ion to produce a colored peroxo-cobalt complex. The absorbance of 260 nm light by the sample is compared to a reference curve generated by standard H2O2 solutions.

Scope of Application

New applications for H2O2 within the food processing and drinking water industries require the accurate measurement of residual H2O2 to 0.1 mg/L. This method is suitable for these and similar applications where the water matrix is clear and free of turbidity. Samples containing greater than 0.2 mg/L may be diluted with distilled water to a concentration suitable for this method.

Interferences

Reducing agents such as bisulfite (that may be slow to react with free H2O2) may quickly react with the Co-H2O2 complex to provide false negative readings. Also, any contaminate that absorbs ultraviolet light at 260 nm may impact the accuracy and sensitivity of the method.

Safety Precautions

Cobalt salts are persistent contaminants and should not be released into the environment. Spent solutions should be collected and disposed of in an approved manner.

Concentrated sulfuric acid is a corrosive, hazardous material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

Cobalt (II) solution. Dissolve 19 gms of CoSO4:7H2O in one liter of distilled water.

Saturated sodium bicarbonate solution. (solubility in cold water is about 100 g/liter).

Sodium hexametaphosphate solution. Dissolve 10 gms of (NaPO3)6 in one liter of distilled water.

0.1 N potassium permanganate solution (Fisher certified concentrate).

Hydrogen peroxide solution. Prepare a 3,000 ppm (0.3%) stock solution of H2O2 by diluting 35 or 50% H2O2 with distilled water. Standardize the 3,000 ppm solution with 0.1 N KMnO4 and use this solution to prepare a 1.5 mg/L H2O2 calibration solution.

Apparatus

Varian Model 634 UV-Visible Spectrophotometer or equivalent with matched calls of 5 cm.

Procedure

General - It is important that all testing equipment be either clean plastic (e.g., polycarbonate or polyethylene) or passivated glassware. Glassware can be passivated by soaking clean glassware in 10% nitric acid for four (4) hours at 70 deg-C and then twenty (20) hours at room temperature. The glassware is then rinsed with distilled water and oven dried at 110 deg-C. Passivated glassware should be stored by covering the opening with aluminum foil.

Standardization of H2O2 Stock Solution

The 3,000 mg/L stock solution of hydrogen peroxide is standardized before use with 0.1 N KMnO4 Pipet 10 mLs of the solution into a beaker, add 5 mLs of 20% H2SO4 and titrate with 0.1 N KMnO4 until the pink color of KMnO4 appears in the solution.

mg/L H2O2 = (mLs of 0.1 N KMnO4) x 170.1

Wt. % H2O2 = (mLs of 0.1 N KMnO4) x 0.017

Calibration Curve

Add 1 mL of the 1.5 mg/L H2O2 calibration solution to 79 mLs of distilled water in a 100 mL volumetric flask. Add successively 1 mL of the sodium hexametaphosphate solution and 1 mL of the Cobalt Solution, and make up the mixture to 100 mL with the saturated sodium bicarbonate solution. This solution has a H2O2 concentration of 0.015 mg/L.

Lace the solution prepared in (a) into a 5 cm quartz cell and measure the absorbance at 260 nm versus a blank reagent solution in a matched cell.

Repeat (a) with 2 mLs of the diluted 1.5 mg/L H2O2 and 78 mLs of the distilled water; 3 mLs of the diluted H2O2 and 77 mLs of the distilled water; 6 mLs of the diluted H2O2 and 74 mLs of the distilled water; and 12 mLs of the diluted H2O2 and 68 mLs of the distilled water. These solutions have H2O2 concentrations of 0.03, 0.043, 0.090 and 0.18 ppm, respectively.

Plot the absorbance against the concentration. Draw the best straight line through the experimental points. A sample curve is shown in Figure 1 (below).

Sample Analysis

For a sample containing about 0.1 mg/L H2O2, pipet 80 mLs into a 100 mL volumetric flask. Add successively 1 mL of the sodium hexametaphosphate solution and 1 mL of the cobalt solution, and make up the mixture to 100 mLs with the saturated sodium bicarbonate solution.

Place the solution prepared in (a) into a 5 cm quartz cell and measure the absorbance at 260 nm versus a blank reagent solution in a matched cell.

Obtain the absorbance and read the corresponding concentration of H2O2 from the calibration curve.

The H2O2 concentration determined from the curve should be multiplied by a dilution factor five-fourths (1.25) to give the H2O2 concentration of the sample.

References

Masschelen, W., "Spectrophotometric Determination of Residual Hydrogen Peroxide", Water and Sewerage Works, p.69, August 1977.

4-

Peroxidase Enzyme Catalyzer

Principle

Peroxidase enzyme catalyzes the transfer of electrons from H2O2 to a colorimetric indicator. The absorbance of 596 nm light by the sample is compared to a reference curve generated by standard H2O2 solutions.

Scope of Application

New applications for H2O2 within the food processing and drinking water industries require the accurate measurement of residual H2O2 to 0.1 mg/L. This method is suitable for these and similar applications where the water matrix is clear and free of turbidity. Samples containing greater than 0.2 mg/L may be diluted with distilled water to a concentration suitable for this method.

Interferences

The peroxidase-H2O2 reaction is highly selective and not typically subject to interferences. However, excessive turbidity or any contaminate that absorbs ultraviolet light at 596 nm may impact the accuracy and sensitivity of the method.

Safety Precautions

Concentrated sulfuric acid is a corrosive, hazardous material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

Peroxidase (Type II 190 purpurogallin units/mg, Sigma Chemical Co., St. Louis, MO). Dissolve 10 mg of peroxidase in 10 mLs of distilled water.

Leuco crystal violet (Aldrich Chemical Co.). Dissolve 50 mg of leuco crystal violet in 100 mLs of 0.5% HCl solution.

Acetate buffer solution pH 4.5. Mix equal volumes of 2 M sodium acetate and 2 M acetic acid and adjust the pH to 4.5 with glacial acetic acid.

Hydrogen peroxide solution. Prepare a 3,000 mg/L (0.3%) stock solution of H2O2 by diluting 35 or 50% H2O2 with distilled water. Standardize the 3,000 mg/L solution with 0.1 N KMnO4 and use this solution to prepare a 1.5 mg/L H2O2 calibration solution.

Apparatus

Varian Model 634 UV-Visible Spectrophotometer or equivalent with matched cells of 1cm.

Procedure

General - It is important that all testing equipment be either clean plastic (e.g., polycarbonate or polyethylene or passivated glassware). Glassware can be passivated by soaking clean glassware in 10% nitric acid for four (4) hours at 70 deg-C and then twenty (20) hours at room temperature. The glassware is then rinsed with distilled water and oven dried at 110 deg-C. Passivated glassware should be stored by covering the opening with aluminum foil.

Standardization of H2O2 Stock Solution

The 3,000 mg/L stock solution of hydrogen peroxide is standardized before use with 0.1 N KMnO4 Pipet 10 mLs of the solution into a beaker, add 5 mLs of 20% H2SO4 and titrate with 0.1 N KMnO4 until the pink color of KMnO4 appears in the solution.

mg/L H2O2 = (mLs of 0.1 N KMnO4) x 170.1

Wt. % H2O2 = (mLs of 0.1 N KMnO4) x 0.017

Calibration Curve

Add 0.11 mL of the 1.5 mg/L H2O2 calibration solution to 0.89 mL of distilled water in a 20 mL vial. Add successively 1 mL of the leuco crystal violet solution, 0.5 mL of the peroxidase solution, and 6 mLs of the acetate buffer solution. This solution has a H2O2 concentration of 0.01 mg/L.

Mix the solution gently and wait five minutes for color development.

Place the solution in a 1 cm quartz cell and measure the absorbance at 596 nm versus a blank solution in a matched cell.

Repeat (a) with 0.33 mL of the diluted 1.5 mg/L H2O2 solution and 9.67 mLs of distilled water; 0.55 mL of the diluted H2O2 solution and 9.45 mLs of distilled water; 1.1 mL of the diluted H2O2 solution and 8.9 mLs of distilled water; and 2.2 mLs of the diluted H2O2 solution and 7.8 mLs of distilled water. These solutions have H2O2 concentrations of 0.03, 0.05, 0.1 and 0.2 mg/L, respectively.

Plot the absorbance against the concentration and draw the best straight lime through the experimental points. A sample curve is shown below.

Sample Analysis

For a sample containing about 0.1 mg/L H2O2 - add 10 mLs of this solution into a 20 mL vial, add successively 1 mL of the leuco crystal violet solution, 0.5 mL of the peroxidase solution, and 5 mLs of the acetate buffer. Mix the solution gently and wait five minutes for color development.

Place the solution in a 1 cm quartz call and measure the absorbance at 596 nm versus a blank reagent solution in a matched cell.

Obtain the absorbance and read the corresponding concentration of H2O2 from the calibration curve.

The H2O2 concentration determined from the curve should be multiplied by a dilution factor of eight-fifths (1.6) to give the concentration of the sample.

References

Chin, H.S. and Cortes, A., "Determination of Hydrogen Peroxide: A Comparison Between the Potentiometric Titration Method and an Enzyme Catalyzed Procedure", Unpublished Draft, National Food Processors Assn., 1950 Sixth Street, Berkeley, CA 94710, 1982.

Good luck,

Rafik

Dear Uthreshwaranath,

The following 4 methods are alternatives for KMNO4 method:

1-

Iodometric Titration

Principle

H2O2 oxidizes iodide to iodine in the presence of acid and molybdate catalyst. The iodine formed is titrated with thiosulfate solution, incorporating a starch indicator.

H2O2 + 2 KI + H2SO4 → I2 + K2SO4 + 2 H2O

I2 + 2 Na2S2O3 → Na2S4O6 + 2 NaI

Scope of Application

This method is somewhat less accurate than the permanganate titration, but is less susceptible to interferences by organics, and is more suitable for measuring mg/L levels of H2O2.

Interferences

Other oxidizing agents will also produce iodine, whereas reducing agents (and unsaturated organics) will react with the liberated iodine. The contribution from other oxidizing agents can be determined by omitting the acid and molybdate catalyst.

Safety Precautions

Concentrated sulfuric acid is a corrosive, hazardous material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

Potassium iodide solution (1% w/v). Dissolve 1.0 grams KI into 100 mLs demineralized water. Store capped in cool place away from light. Yellow-orange tinted KI solution indicates some air oxidation to iodine, which can be removed by adding a 1-2 drops of dilute sodium thiosulfate solution.

Ammonium molybdate solution. Dissolve 9 grams ammonium molybdate in 10 mLs 6N NH4OH. Add 24 grams NH4NO3 and dilute to 100 mLs.

Sulfuric acid solution. Carefully add one part H2SO4-98% to four parts demineralized water.

Starch indicator.

Sodium thiosulfate solution (0.1N).

Apparatus

Analytical balance (+/- 0.1 mg/L)

Small weighing bottle (< 5 mLs)

250 mL Erlenmeyer flask

50 mL buret (Class A)

Medicine dropper

Procedure

Weigh to the nearest 0.1 mg an amount of H2O2 equivalent to a titer of 30 mLs (0.06 grms of H2O2) using a 5 mL beaker and medicine dropper. Transfer sample to Erlenmeyer flask.

Add to Erlenmeyer flask 50 mL of demineralized water, 10 mL of sulfuric acid solution, 10-15 mLs of potassium iodide solution, and two drops ammonium molybdate solution.

Titrate with 0.1 N sodium thiosulfate to faint yellow or straw color. Swirl or stir gently during titration to minimize iodine loss.

Add about 2 mL starch indicator, and continue titration until the blue color just disappears.

Repeat steps 2-4 on a blank sample of water (omitting the H2O2).

Calculation

Weight % H2O2 = (A - B) x (Normality of Na2S2O3) x 1.7 / Sample weight in grams

Where: A = mLs Na2S2O3 for sample; B = mLs Na2S2O3 for blank

References

C. T. Kingzett, Chem. News, 41:76 (1880); 43:161 (1881)

I. M. Kolthoff, Chem Weekblad, 17:197 (1920)

2-

Titanium Oxalate (Spectrophotometric)

Principle

The sample is clarified by treatment with aluminum chloride and sodium hydroxide solution and the hydrogen peroxide reacted with potassium titanium oxalate in acid solution to form the yellow pertitanic acid complex. The colored complex is measured spectrophotometrically at 400 nm.

Scope of Application

This method is suitable for the determination of hydrogen peroxide in aqueous effluents and raw sewage in the range 0.1 - 50 µg/mL (or 0.1 - 50 mg/L) as H2O2.

Interferences

Formation of the peroxotitanium complex is specific to hydrogen peroxide. However, wastewaters possessing a strong yellow background color may affect accuracy. Normal background color can be reduced by filtering the sample, or compensated for by zeroing out a blank of unreacted sample. The method includes a flocculation pretreatment step to remove suspended matter – the AlCl3 - NaOH pretreatment step may be omitted when analyzing clear waters.

Safety Precautions

Potassium titanium oxalate is a toxic material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended.

Concentrated sulfuric acid and sodium hydroxide are corrosive, hazardous materials and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

All reagents should be of analytical reagent grade unless otherwise stated

Potassium permanganate solution (0.1N)

Aluminum chloride solution (484 g/L)

Dissolve 121 g of aluminum chloride hexahydrate in 150 mL of demineralized water. Dilute to 250 mL with demineralized water in a measuring cylinder and mix well.

Potassium titanium oxalate solution (50 g/L)

Dissolve 25 g of potassium titanium oxalate, in 400 mL of demineralized water, warming if necessary. Cool and dilute to 500 mL with demineralized water in a measuring cylinder and mix well.

Warning: Potassium titanium oxalate is toxic and solutions must be handled using a safety pipette or burette.

Sodium hydroxide solution (240 g/L)

Dissolve 60 g of sodium hydroxide in 150 mL of demineralized water, dilute to 250 mL with demineralized water in a measuring cylinder and mix well.

Sulfuric acid solution (1+9)

Slowly add 50 mL of sulfuric acid, d 1.84, with continuous stirring to 450 mL of demineralized water in a 1 liter beaker. Cool.

Note: Safety goggles must be worn when handling concentrated sulfuric acid.

Sulfuric acid solution (1 + 17)

Slowly add 20 mL of sulfuric acid, d 1.84, with continuous stirring to 340 mL of demineralized water in a 1 liter beaker. Cool.

Standard hydrogen peroxide solution (stock) 1 mL = 1000 μg

Add 7.50 mL of hydrogen peroxide solution (275 g/Kg) to a 2 liter volumetric flask, dilute to volume with demineralized water and mix well.

This solution must be standardized as described below on the day of use.

Using measuring cylinders, add 10 mL sulfuric acid solution (1 + 9) and 50 mL of demineralized water to a 250 mL conical beaker. Add potassium permanganate solution (0.1N) dropwise to the appearance of a faint permanent pink color.

Pipette 50.0 mL of hydrogen peroxide solution (stock) into the flask and titrate with potassium permanganate solution (0.1N) to the reappearance of the same permanent pink color. Let the titration obtained be T mL.

Then the concentration of the hydrogen peroxide solution (stock) = ((T x N x 17 x 1000 x 1000 x 1000) / (1000 x 50 x 1000)) μg/mL = T x N x 340 μg/mL

Where N is the normality of the potassium permanganate solution.

Let this concentration be G μg/mL.

Standard hydrogen peroxide solution (working) 1 mL = 100 μg

Pipette 25.0 mL of hydrogen peroxide solution (stock) into a 250 mL volumetric flask. Dilute to volume with demineralized water and mix well.

Then the concentration of the hydrogen peroxide solution (working) = G/10 μg/mL

This solution must be freshly prepared on the day of use.

Apparatus

Spectrophotometer capable of measuring absorption at a wavelength of 400 nm and fitted with 10 mm and 40 mm pathlength glass cells.

Procedure

Preparation of Calibration Graph

From a burette add the volumes of hydrogen peroxide solution (working) shown in the table below into a series of 25 mL volumetric flasks.

Volume of Standard Hydrogen Peroxide solution (working) (ml)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Mass of Hydrogen Peroxide taken (ug)

0.0

1.0 x (G/10)

2.0 x (G/10)

3.0 x (G/10)

4.0 x (G/10)

5.0 x (G/10)

6.0 x (G/10)

Using a safety pipette add 2.5 mL of sulfuric acid solution (1 + 17) and dilute each solution to about 20 mL by adding suitable volumes of demineralized water. Mix well and using a safety pipette add 2.0 mL of potassium titanium oxalate solution (50 g/L). Dilute each solution to volume with demineralized water and mix well.

Measurement of Standard Solutions

Set the spectrophotometer to measure absorption at a wavelength of 400 run and select a pair of 10 mm pathlength glass cells.

Adjust the instrument for zero absorption against demineralized water in one of the cells. Using the other cell measure in turn the absorption of each of the standard solutions.

Subtract the absorption of the standard solution containing no added hydrogen peroxide from that of the remaining standard solutions.

Plot the optical densities against the corresponding hydrogen peroxide content of the standard solutions.

Draw in the line of best fit through the series of points and the origin to obtain the required calibration graph.

Repeat the measurements using 40 mm glass cells for the solutions containing up to 5.0 mL of standard hydrogen peroxide (working) solution.

Preparation and Analysis of Sample Solutions

Fill a 500 mL glass bottle with the sample, if possible directly from the source of supply, by means of a rubber tube passing to the bottom of the bottle. Allow the sample to flush out the bottle for two minutes then withdraw the tube and stopper the bottle.

Pipette into the bottle 1.0 mL of aluminum chloride solution (484 g/L) and 1.0 mL of sodium hydroxide solution (240 g/L) with the pipette tips beneath the surface of the liquid. Allow any surplus sample to overflow from the bottle. Replace the stopper and mix the contents by inverting the bottle several times. Allow the precipitate to settle.

Pipette 20.0 mL of the supernatant liquor from the clarified sample into a clean 25 mL volumetric flask.

Prepare a reagent blank solution by pipetting 20.0 mL of demineralized water into a clean 25 mL volumetric flask.

Treat the sample and blank solutions exactly as described under Preparation of Calibration Graph from "using a safety pipette add 2.5 mL of sulfuric acid solution (1 +17) ..."

Prepare a sample blank solution by pipetting 20.0 mL of the supernatant liquor from the clarified sample into a 25 mL volumetric flask. Add 2.5 mL of sulfuric acid solution (1 + 17) and dilute to volume with demineralized water.

Measure the absorption of the sample solution, the sample blank solution and the reagent blank solution as described. Subtract the absorption of the sample blank solution and the absorption of the reagent blank solution from that of the test solution.

Relate the optical density so obtained to the calibration graph to obtain the weight of hydrogen peroxide. Let this weight be A µg as H2O2.

Calculation

Hydrogen peroxide content (as H2O2) = (A/20) mg/L

Sourcing for Titanium Reagent

Titanium potassium oxalate

Alfa Aesar: (978) 521-6401 http://www.alfa.com/

City Chemical: (800) 248-2436 http://www.citychemical.com/

MP Biomedicals: (800) 854-0530 http://www.mpbio.com/

Pfaltz & Bauer: (203) 574-0075 http://www.pfaltzandbauer.com/

References

Solvay Chemicals, Inc.

3-

Cobalt Bicarbonate Method

Principle

H2O2 reacts with cobalt ion to produce a colored peroxo-cobalt complex. The absorbance of 260 nm light by the sample is compared to a reference curve generated by standard H2O2 solutions.

Scope of Application

New applications for H2O2 within the food processing and drinking water industries require the accurate measurement of residual H2O2 to 0.1 mg/L. This method is suitable for these and similar applications where the water matrix is clear and free of turbidity. Samples containing greater than 0.2 mg/L may be diluted with distilled water to a concentration suitable for this method.

Interferences

Reducing agents such as bisulfite (that may be slow to react with free H2O2) may quickly react with the Co-H2O2 complex to provide false negative readings. Also, any contaminate that absorbs ultraviolet light at 260 nm may impact the accuracy and sensitivity of the method.

Safety Precautions

Cobalt salts are persistent contaminants and should not be released into the environment. Spent solutions should be collected and disposed of in an approved manner.

Concentrated sulfuric acid is a corrosive, hazardous material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

Cobalt (II) solution. Dissolve 19 gms of CoSO4:7H2O in one liter of distilled water.

Saturated sodium bicarbonate solution. (solubility in cold water is about 100 g/liter).

Sodium hexametaphosphate solution. Dissolve 10 gms of (NaPO3)6 in one liter of distilled water.

0.1 N potassium permanganate solution (Fisher certified concentrate).

Hydrogen peroxide solution. Prepare a 3,000 ppm (0.3%) stock solution of H2O2 by diluting 35 or 50% H2O2 with distilled water. Standardize the 3,000 ppm solution with 0.1 N KMnO4 and use this solution to prepare a 1.5 mg/L H2O2 calibration solution.

Apparatus

Varian Model 634 UV-Visible Spectrophotometer or equivalent with matched calls of 5 cm.

Procedure

General - It is important that all testing equipment be either clean plastic (e.g., polycarbonate or polyethylene) or passivated glassware. Glassware can be passivated by soaking clean glassware in 10% nitric acid for four (4) hours at 70 deg-C and then twenty (20) hours at room temperature. The glassware is then rinsed with distilled water and oven dried at 110 deg-C. Passivated glassware should be stored by covering the opening with aluminum foil.

Standardization of H2O2 Stock Solution

The 3,000 mg/L stock solution of hydrogen peroxide is standardized before use with 0.1 N KMnO4 Pipet 10 mLs of the solution into a beaker, add 5 mLs of 20% H2SO4 and titrate with 0.1 N KMnO4 until the pink color of KMnO4 appears in the solution.

mg/L H2O2 = (mLs of 0.1 N KMnO4) x 170.1

Wt. % H2O2 = (mLs of 0.1 N KMnO4) x 0.017

Calibration Curve

Add 1 mL of the 1.5 mg/L H2O2 calibration solution to 79 mLs of distilled water in a 100 mL volumetric flask. Add successively 1 mL of the sodium hexametaphosphate solution and 1 mL of the Cobalt Solution, and make up the mixture to 100 mL with the saturated sodium bicarbonate solution. This solution has a H2O2 concentration of 0.015 mg/L.

Lace the solution prepared in (a) into a 5 cm quartz cell and measure the absorbance at 260 nm versus a blank reagent solution in a matched cell.

Repeat (a) with 2 mLs of the diluted 1.5 mg/L H2O2 and 78 mLs of the distilled water; 3 mLs of the diluted H2O2 and 77 mLs of the distilled water; 6 mLs of the diluted H2O2 and 74 mLs of the distilled water; and 12 mLs of the diluted H2O2 and 68 mLs of the distilled water. These solutions have H2O2 concentrations of 0.03, 0.043, 0.090 and 0.18 ppm, respectively.

Plot the absorbance against the concentration. Draw the best straight line through the experimental points. A sample curve is shown in Figure 1 (below).

Sample Analysis

For a sample containing about 0.1 mg/L H2O2, pipet 80 mLs into a 100 mL volumetric flask. Add successively 1 mL of the sodium hexametaphosphate solution and 1 mL of the cobalt solution, and make up the mixture to 100 mLs with the saturated sodium bicarbonate solution.

Place the solution prepared in (a) into a 5 cm quartz cell and measure the absorbance at 260 nm versus a blank reagent solution in a matched cell.

Obtain the absorbance and read the corresponding concentration of H2O2 from the calibration curve.

The H2O2 concentration determined from the curve should be multiplied by a dilution factor five-fourths (1.25) to give the H2O2 concentration of the sample.

References

Masschelen, W., "Spectrophotometric Determination of Residual Hydrogen Peroxide", Water and Sewerage Works, p.69, August 1977.

4-

Peroxidase Enzyme Catalyzer

Principle

Peroxidase enzyme catalyzes the transfer of electrons from H2O2 to a colorimetric indicator. The absorbance of 596 nm light by the sample is compared to a reference curve generated by standard H2O2 solutions.

Scope of Application

New applications for H2O2 within the food processing and drinking water industries require the accurate measurement of residual H2O2 to 0.1 mg/L. This method is suitable for these and similar applications where the water matrix is clear and free of turbidity. Samples containing greater than 0.2 mg/L may be diluted with distilled water to a concentration suitable for this method.

Interferences

The peroxidase-H2O2 reaction is highly selective and not typically subject to interferences. However, excessive turbidity or any contaminate that absorbs ultraviolet light at 596 nm may impact the accuracy and sensitivity of the method.

Safety Precautions

Concentrated sulfuric acid is a corrosive, hazardous material and should be handled and disposed of in accordance with the MSDS. Neoprene gloves and monogoggles are recommended, as is working under a vacuum hood.

Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film.

Reagents

Peroxidase (Type II 190 purpurogallin units/mg, Sigma Chemical Co., St. Louis, MO). Dissolve 10 mg of peroxidase in 10 mLs of distilled water.

Leuco crystal violet (Aldrich Chemical Co.). Dissolve 50 mg of leuco crystal violet in 100 mLs of 0.5% HCl solution.

Acetate buffer solution pH 4.5. Mix equal volumes of 2 M sodium acetate and 2 M acetic acid and adjust the pH to 4.5 with glacial acetic acid.

Hydrogen peroxide solution. Prepare a 3,000 mg/L (0.3%) stock solution of H2O2 by diluting 35 or 50% H2O2 with distilled water. Standardize the 3,000 mg/L solution with 0.1 N KMnO4 and use this solution to prepare a 1.5 mg/L H2O2 calibration solution.

Apparatus

Varian Model 634 UV-Visible Spectrophotometer or equivalent with matched cells of 1cm.

Procedure

General - It is important that all testing equipment be either clean plastic (e.g., polycarbonate or polyethylene or passivated glassware). Glassware can be passivated by soaking clean glassware in 10% nitric acid for four (4) hours at 70 deg-C and then twenty (20) hours at room temperature. The glassware is then rinsed with distilled water and oven dried at 110 deg-C. Passivated glassware should be stored by covering the opening with aluminum foil.

Standardization of H2O2 Stock Solution

The 3,000 mg/L stock solution of hydrogen peroxide is standardized before use with 0.1 N KMnO4 Pipet 10 mLs of the solution into a beaker, add 5 mLs of 20% H2SO4 and titrate with 0.1 N KMnO4 until the pink color of KMnO4 appears in the solution.

mg/L H2O2 = (mLs of 0.1 N KMnO4) x 170.1

Wt. % H2O2 = (mLs of 0.1 N KMnO4) x 0.017

Calibration Curve

Add 0.11 mL of the 1.5 mg/L H2O2 calibration solution to 0.89 mL of distilled water in a 20 mL vial. Add successively 1 mL of the leuco crystal violet solution, 0.5 mL of the peroxidase solution, and 6 mLs of the acetate buffer solution. This solution has a H2O2 concentration of 0.01 mg/L.

Mix the solution gently and wait five minutes for color development.

Place the solution in a 1 cm quartz cell and measure the absorbance at 596 nm versus a blank solution in a matched cell.

Repeat (a) with 0.33 mL of the diluted 1.5 mg/L H2O2 solution and 9.67 mLs of distilled water; 0.55 mL of the diluted H2O2 solution and 9.45 mLs of distilled water; 1.1 mL of the diluted H2O2 solution and 8.9 mLs of distilled water; and 2.2 mLs of the diluted H2O2 solution and 7.8 mLs of distilled water. These solutions have H2O2 concentrations of 0.03, 0.05, 0.1 and 0.2 mg/L, respectively.

Plot the absorbance against the concentration and draw the best straight lime through the experimental points. A sample curve is shown below.

Sample Analysis

For a sample containing about 0.1 mg/L H2O2 - add 10 mLs of this solution into a 20 mL vial, add successively 1 mL of the leuco crystal violet solution, 0.5 mL of the peroxidase solution, and 5 mLs of the acetate buffer. Mix the solution gently and wait five minutes for color development.

Place the solution in a 1 cm quartz call and measure the absorbance at 596 nm versus a blank reagent solution in a matched cell.

Obtain the absorbance and read the corresponding concentration of H2O2 from the calibration curve.

The H2O2 concentration determined from the curve should be multiplied by a dilution factor of eight-fifths (1.6) to give the concentration of the sample.

References

Chin, H.S. and Cortes, A., "Determination of Hydrogen Peroxide: A Comparison Between the Potentiometric Titration Method and an Enzyme Catalyzed Procedure", Unpublished Draft, National Food Processors Assn., 1950 Sixth Street, Berkeley, CA 94710, 1982.

Good luck,

Rafik

hi the second method of Rafik Karaman is better

Title:

A simple spectrophotometric determination of hydrogen peroxide at low concentrations in aqueous solution

Analytica Chimica ActaVolume 204, 1988, Pages 349-353

Enzymatic HRP based sensors

Data Biofuel cell based on direct bioelectrocatalysis

Can someone explain the formulae

The concentration of the hydrogen peroxide solution (stock) = ((T*N*17*1000*1000*1000)/(1000*50*1000)) ug/mL