Field fluorometers as dispersed oil-in-water monitors

A laboratory study of the Turner Instrument flow-through models 10AU and 10 fluorometers was conducted to review their ability to measure real-time oil-in-water concentrations, to compare the results to other total petroleum hydrocarbon (TPH) procedures and to improve the understanding of the relationship of the fluorescence to the chemical composition of the oils. Comparison of the fluorometer results to standard infrared and gas chromatography laboratory procedures showed all methods capable of detecting and differentiating between small changes in oil concentration. The infrared and gas chromatography generated similar values while the fluorometer values were of the same order of magnitude but typically 20-80% higher. The chemical composition of the oils was determined by gas chromatographic techniques and compared to the signal outputs of the fluorometers. It was found that the fluorometer data could not be directly linked to the concentration of any specific aromatic hydrocarbon such as naphthalene or to the sum of the polycyclic aromatic hydrocarbon (PAH) compounds. Evidence suggests that the fluorescence signal is generated by a combination of PAH compounds. Also, the response of the fluorometers may also be influenced by the presence of volatile aromatic compounds such as benzene, toluene, ethyl benzene and xylene (BTEX) and C3-benzenes (BTEX + C3B) in combination with the PAH compounds.

Solvent vapour monitoring in work space by solid phase micro extraction

Solid phase micro extraction (SPME) is a fast, solvent-less alternative to conventional charcoal tube sampling/carbon disulfide extraction for volatile organic compounds (VOC). In this work, SPME was compared to the active sampling technique in a typical lab atmosphere. Two different types of fibre coatings were evaluated for solvent vapour at ambient concentration. A general purpose 100 microm film polydimethylsiloxane (PDMS) fibre was found to be unsuitable for VOC work, despite the thick coating. The mixed-phase carboxen/PDMS fibre was found to be suitable. Sensitivity of the SPME was far greater than charcoal sorbent tube method. Calibration studies using typical solvent such as dichloromethane (DCM), benzene (B) and toluene (T) showed an optimal exposure time of 5 min, with a repeatability of less than 20% for a broad spectrum of organic vapour. Minimum detectable amount for DCM is in the range of 0.01 microg/l (0.003 ppmv). Variation among different fibres was generally within 30% at a vapour concentration of 1 microg DCM/l, which was more than adequate for field monitoring purpose. Adsorption characteristics and calibration procedures were studied. An actual application of SPME was carried out to measure background level of solvent vapour at a bench where DCM was used extensively. Agreement between the SPME and the charcoal sampling method was generally within a factor of two. No DCM concentration was found to be above the regulatory limit of 50 ppmv.

An evaluation of field total petroleum hydrocarbon (TPH) systems

An evaluation of several field kits and petroleum hydrocarbon measuring systems was conducted. The field kits were the immunoassay based EnviroGard petroleum fuels in soil test kit (EnviroGard, Millipore Canada, Mississauga, Ont., Canada), the turbidimetric based PetroFlag hydrocarbon test kit for soil (Dexsil, Hamden, CT, USA), a DR/2000 field kit (Hach Company, Loveland CO, USA) employing colorimetric test procedures and a total organic carbon (TOC) analysis instrument (Dohrmann Division, Rosemount Analytical Inc., Santa Clara, CA, USA) using oxidation principles. These procedures were compared to the traditional technique of extraction of the petroleum hydrocarbons using trichlorotrifluoroethane (Freon 113) as the solvent and subsequent infrared (IR) analysis using a portable fixed wavelength analyzer (Buck Scientific, East Norwalk, CT, USA). The EnviroGard kit was affected by the sample matrix. The soil type and the presence or lack thereof specific chemical components affected the capability to detect the petroleum hydrocarbon concentration. The PetroFlag soil test kit tended to generate results higher than the accepted concentration. The IR method was better capable of producing results similar to the expected concentration values of the prepared samples. Results indicate that the total organic carbon analysis technique evaluated is best suited for samples containing dissolved hydrocarbons in water and is not a preferred procedure for water samples containing dispersed or floating oil. At low concentrations of 10ppm and less, the TOC method and IR method have concentration values within a few parts-per-million (ppm) of each other, however, an examination of the trends in the results for all samples shows no similarity. This would indicate that the traditional extraction and infrared method and the total organic carbon method are not measuring the same parameter.Finally, the colorimetric field kit was capable of quantifying the concentration of oil in water samples within limits. The results from the oil-in-water method built into the unit at the factory were not comparable with analysis carried out by the infrared technique. With specific methods for each oil incorporated into the spectrophotometer, the comparability of data increased significantly. Results generated by the kit are dependent upon the color and amount of the oil in the sample. The kit is best suited for dark colored oils and the water samples with concentrations in the range of 10 to 85ppm by weight.