Sorbent trapping, breakthrough

The field data QA/QC samples consisted of duplicate samples, field spikes with NIST (National Institute of Standards and Technology) traceable spike standards, field blanks, and breakthrough sections. Frontier Global Sciences (FGS), the project laboratory, provided all analytical services as well as all sampling media including spiked sorbent trap. FGS is a NELAP (National Environmental Laboratory Accreditation Program) accredited and ISO 17025 accredited laboratory specializing in the analysis of trace and heavy metals. 

An alternative way of eliminating water in the RPLC eluent is to introduce an SPE trapping column after the LC column (88, 99). After a post-column addition of water (to prevent breakthrough of the less retained compounds), the fraction that elutes from the RPLC column is trapped on to a short-column which is usually packed with polymeric sorbent. This system can use mobile phases containing salts, buffers or ion-pair reagents which can not be introduced directly into the GC unit. This system has been successfully applied, for example, to the analysis of polycyclic aromatic hydrocarbons (PAHs) in water samples (99). 

The breakthrough volume is defined as the volume of gaseous sample that can be drawn through a sample tube before an analyte is eluted from the tube. Every sorbent has a limited capacity for a given analyte which depends on the characteristics of the sorbent, on the type of compound to be trapped and on certain sampling parameters, like the temperature and the humidity of the air (Bertoni et al., 1981 Brown and Purnell, 1979). Breakthrough of a substance can occur if ... 

Thermal desorption from the SPE cartridge is a further possibility [77,122]. In this approach, the sample is introduced at a controlled speed into the packed liner of a PTV injector set to a low temperature with the water eliminated via the split vent. Salts and involatile polar material are rinsed from the sorbent with water and the sorbent dried by purging with a high carrier gas flow rate. The trapped analytes are subsequently desorbed in the splitless mode by rapidly heating the PTV to the injection temperature. The most commonly used sorbents are Tenax and Carbofrit. The method is restricted to a narrow range of applications by the low breakthrough volume of polar analytes on the... 

The breakthrough volxame trends for many sorbate types on the porous polymeric sorbents indicate a limited trapping capacity in the supercritical fluid CO2 above 200 atmospheres. Fractionation and selective retention on these sorbents seems only possible below this specified pressure limit for the odoriferous solutes examined in this study. Adsorbent surface area appears to be the most significant factor contributing to the retention of sorbates on these sorbents as well as activated carbon. For certain synthetic adsorbents (Tenax, XAD-2) employed in this study, pressure-induced morphological changes in the polymer matrix lead to an increase in the sorption capacity, and hence to an increase in breakthrough volumes at intermediate pressures. 

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