Análisis físico-químico

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Tanto la olfatometría como el análisis fisicoquímico son 2 métodos adecuados para evaluar la contaminación producida por substancias olorosas. Las dos técnicas tienen sus puntos positivos y negativos y proporcionan una información complementaria. La olfatometría da una indicación directa de la intensidad de los olores pero no puede identificar los compuestos responsables de la molestia. El análisis fisicoquímico permite la identificación de los componentes que forman la mezcla y puede proporcionar información sobre la toxicidad de un gas oloroso. En cambio, no puede ser relacionado con la molestia por malos olores debido a la complejidad de:
  • la percepción de los olores.
  • del gas en si mismo (más de 550 moléculas se han identificado en una muestra de gas de un vertedero tan diferentes como sulfuros, azoados, aldehídos, ácidos, cetonas, alcoholes,compuestos aromáticos, compuestos clorados, esteres y terpenos con una amplia variedad de características (polaridad, estabilidad, punto de ebullición, etc.) diferentes.[1]

  La muestra de gas oloroso se puede recoger en tubos empacados, bolsas Tedlar o contenedores adecuados (canisters) para su análisis posterior en el laboratorio. Asimismo, el gas se puede analizar in situ usando métodos colorimétricos o detectores electrónicos. En algunos casos, es posible llevar la muestra directamente a un cromatógrafo de gases acoplado a un detector adecuado (MS, NPD, FID, PID, FPD, etc.).

Debido al hecho de que los olores están compuestos por multitud de gases a concentraciones extremadamente pequeñas, es muy dificil y costoso determinar la composición exacta de un olor. En la siguiente tabla se expone el umbral de olor para algunos compuestos químicos.

Compuesto químico

Umbral de olor, ppm

 

Aldehidos

 

Acetaldehido

0.21

Propionadehido

0.0095

 

Acidos grasos volátiles

 

Ácido acético

1.0

Ácido Propionico

20.0

Ácido Butyrico

0.001

 

Compuestos nitrogenados

 

Metilamina

0.021

Dimetilamina

0.047

Trimetilamina

0.00021

Skatol

0.019

Amoniaco

46.8

 

Compuestos azufrados

 

Metanotiol

0.0021

Etanotiol

0.001

Propanotiol

0.00074

t-Butiltiol

0.00009

Dimetil sulfito

0.001

Hydrogen sulfide

0.0072


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