dispersion and may be for example metallic sodium dispersed in mineral oil when detection limits below the percentage level are needed the fame content of a sample may be concentrated by adsorbing the esters onto a solid phase and then eluting into a liquid phase at a higher concentration than in the original sample for instance biodiesel contamination in jet fuel is carefully monitored for even part per million levels of fame in the fuel a jet fuel sample may be contacted with an adsorbent by for example mixing the fuel with an adsorbent or by passing the fuel sample over a column of adsorbent the adsorbent may be any material that cart efficiently adsorb fame while not having a specific affinity for hydrocarbons adsorbents may include for example silica gel alumina and florisil in one set of embodiments a column containing florisil has been found to efficiently remove the methyl esters from the fuel sample after passing a volume of fuel over the adsorbent the methyl esters can be desorbed via a solvent or cosolvents with an affinity for fame cosolvents may be for example a mixture of a hydrocarbon and an alcohol in some embodiments a cosolvent of 20.