TCEQ Method 24

Isokinetic
Heated out of stack filter (M5).
Applicable for the determination of particulate in stack gases containing sulfur oxides and ammonia.
This method is a modification (combination) of EPA Method 5 and EPA Method 8 This particulate weight determined by this method includes the weight of ammonium sulfate [(NH4)2SO4] and ammonium sulfite [(NH4)2SO3] created from the sulfuric acid (H2SO4), suflur trioxide (SO3) and ammonia (NH3) in the stack gas. Stack (NH4)2SO4 and stack (NH4)2SO3 are analyzed and reported by this method. This method also provides analyses for free (unreacted with NH3) H2SO4 and free SO2, so weights for both of these entities are reported.
Most of the particulate matter is collected on the filter. The remainder is collected in the probe wash and in the IPA absorber. This particulate may be water- or acid-soluble and can not be isolated by a filtration technique. Sulfuric acid mist may be caught on the heated filter and combined with ammonia from the stack to form ammonium sulfate. The remaining acid mist and ammonia are trapped by the IPA absorber, which also collects sulfur trioxide and converts it to sulfuric acid. Ammonium sulfate may also be found in the probe wash.

Free Sulfur Dioxide - SO2
- Each peroxide absorber solution is analyzed for sulfate (reported as SO2) using ion chromatography (IC) according to the TECQ Laboratory Methods Manual, Method 26A and Clean Air Engineering's Ion Chromatography procedures;
- From these analyses, the total mass of SO2 is reported;
Total stack ammonium sulfite - (NH4)2SO3;
Total stack ammonium sulfate - (NH4)2SO4;
Total free acid mist - H2SO4; and
Total particulate matter.

The filter is extracted with DI water. A portion of the extract solution is then analyzed for:
- Ammonium sulfite (NH₄)₂SO₃;
- Ammonium sulfate (NH₄)₂SO₄; and
- Free sulfuric acid mist H₂SO₄.
The remaining portion of the extracting solution, along with the filter and undissolved particulate matter, is transferred to a clean, tared teflon beaker liner, is made basic using ammonium hydroxide (to neutralize any free sulfuric acid) and is evaporated to dryness.
The probe rinse and the IPA absorber catches are analyzed separately. Each volume is adjusted using DI water. Then a portion of each solution is analyzed for:
- Ammonium sulfite (NH₄)₂SO₃;
- Ammonium sulfate (NH₄)₂SO₄; and
- Free sulfuric acid mist H₂SO₄.
The remaining portion of the extracting solution, along with the filter and undissolved particulate matter, is transferred to a clean, tared teflon beaker liner, is made basic using ammonium hydroxide (to neutralize any free sulfuric acid) and is evaporated to dryness.

Isopropanol must be shipped as a hazardous material. Please call for IATA codes if you need them.
Samples may be shipped at ambient temperatures.
It may prove more economical to keep isopropanol rinses separate, ship other samples normally, and the IPA as hazardous.
Be sure to include a chain of custody for each shipping container.