Badge samplers solvent desorption

As for workplace monitoring, there have been two main types of diffusive sampler used for monitoring of indoor air (i) badge type samplers containing a strong adsorbent such as charcoal that requires solvent desorption for GC analysis and (ii) tube type samplers with weaker adsorbents such as the porous polymer Tenax that can be thermally desorbed. The samplers most widely used have been developed for monitoring of workplace atmospheres and applied to indoor air through modification of the exposure period and the analytical method. 

The badge type samplers have higher diffusive uptake rates and, because strong sorbents are used, are not prone to reverse diffusion effects. They require solvent desorption (which is not easily automated) and the use of toxic solvents, and recovery of some compounds is poor. Contaminants in the solvent can reduce sensitivity as does the dilution effect typically 2 ml of solvent is used to desorb and 1 pi (i.e. 0.05 % of the collected mass of analyte) is used for GC analysis. 

Figure 2 Types of diffusive samplers. From the left a colorimetric length-of-stain sampler a tube-type sampler for thermal desorption a badge-type sampler with multiple channels and no windscreen, containing a removable sorbent pad for solvent desorption a badge-type sampler with multiple channels and an internal windscreen, containing granular sorbent for in situ solvent desorption a badge-type sampler with an external vtrind-screen, behind which is an open diffusion path, and containing a sorbent pad for in situ solvent desorption.

One important consideration is the possibility of reuse of thermal desorption tubes, since they are cleaned in the desorption step. Charcoal badge-type samplers are of single-use nature but cheaper. Solvent desorption also allows multiple analyses from a single sample to give greater accuracy. 

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