Identifying Organic Contaminants in Sub Tier Castings Using FTIR Fingerprinting
Attenuated total reflectance FTIR identifies organic parting agents on raw castings before expensive coating processes fail on customer lines.
Solvent Desorption
Meaning
Laboratory process of removing adsorbed gas or liquid molecules from a solid surface or a porous material using a solvent. In environmental monitoring and industrial hygiene, solvent desorption is used to extract captured pollutants from charcoal tubes or air filters for analysis. The solvent competes for the binding sites on the adsorbent, releasing the target chemicals into the liquid phase.
Analytical Procedure
Extraction efficiency depends on the choice of solvent and the duration of the contact. Carbon disulfide is frequently used because it has a high affinity for a wide range of organic vapors and does not interfere with gas chromatography results. The sample is agitated in the solvent for a fixed period to ensure the maximum amount of the contaminant is recovered.
This liquid is then injected into the instrument to measure the concentration of the original air sample. Such measurements allow for the calculation of the total mass of the pollutant present in the sampled air volume.
Regulatory Compliance
Chinese national standards for workplace air quality specify the desorption methods for hundreds of industrial chemicals. Factories must conduct regular air sampling to ensure that exposure levels for workers remain below the occupational exposure limits. The results of these tests are filed with the local health and safety bureau.
Accurate desorption is necessary to avoid underreporting the actual chemical exposure in the plant.
Process Limit
Effectiveness of the technique decreases if the adsorbent is overloaded or if the chemicals have reacted with the surface. If the desorption rate is low, the final measurement will not reflect the true amount of material captured. Heating the solvent or using ultrasonic baths can help improve the recovery rate for difficult compounds.