Principle

The method involves reacting a sample which contains residual H2O2 with titanium sulfate to produce a yellow peroxo-complex. The sample is then analyzed by spectrophotometer at 405 nm, and the absorption compared to a standardized curve.

Scope of Application

This procedure is appropriate for determining residual H2O2 present in waters and wastewaters in concentrations ranging from 1 - 10 mg/L in undiluted samples, or higher concentrations provided an appropriate dilution.

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.

Safety Precautions

Titanium sulfate 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 is 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

1. Deionized or distilled water.
2. Titanium sulfate. Heat 500 mLs conc. sulfuric acid to 180 deg-F (in a vacuum hood). Add 20 gms TiSO4 - 8H2O very slowly while stirring - CAUTION: H2SO4 will splatter when TiSO4 is added. After the TiSO4 has dissolved in the acid, allow the solution to cool overnight. Slowly add the TiSO4 / H2SO4 solution to 3000 mLs of DI water that is immersed in an ice bath. Allow to cool. (TiSO4 - 8H2O may be obtained from GFS Chemical Co., P.O. 23214, Columbus OH 43223).

Procedure

Sample Treatment

1. Sample pretreatment -- Filter the sample if it is cloudy and prepare appropriate dilutions per the table below.
   
   
   

   Expected H2O2 Concentration	Suggested Sample Dilution
   1-10 mg/L	none
   10-100 mg/L	1:9
   100-1000 mg/L	1:99

   
   
   
2. Transfer 1.0 mL sample to a 25-50 mL beaker.
3. Pipet 9.0 mLs DI water into the beaker and stir to mix.
4. Add 1.0 mL TiSO4 solution to the beaker and stir to mix.
5. Allow the solution to develop color for 2 minutes.

Spectrophotometric Measurement

1. Turn on the instrument and allow it to warm up for 5 - 10 minutes.
2. Set the instrument wavelength to 405 nm, and adjust the zero control for 0% Transmittance.
3. Insert DI water blank and adjust instrument needle to full scale (0% Absorbance).
4. Insert sample and read Absorbance.
5. Determine H2O2 concentration by referencing the chart below, or similar chart prepared from known H2O2 concentrations.