The goal of my wok was to evaluate if oil spots found in roads or parking lots could be analyzed using simple extractions. This post shows final results of th analysis and provide some comments.
After the fist few attempts to conduct measurements it was noticed that alignment of the spectrometer unit and the cell holder needed to be adjusted in order to maximize detection. A piece of cardboard (2mm thick was located under the spectrometer body at about 7-8 cm from the slit window to maximize spectrum detection. This procedure had to be conducted each day. One of the diluted standards (80W90) was used to verify spectral quality. I think that this issue is created by the flexibility of the material used and the coupling of the spectrometer and the cell holder unit.. a more rigid material may be used for the base of the cuvette holder which may be better suited to keep alignment issues to a minimal.
The following are the resulting graphs of each standard, unknown or field sample. Standard samples were mostely diluted 1 drop in 1mL unless indicated otherwise. I would not recommend diluting further.
OTK standards 80W90: https://spectralworkbench.org/sets/3031; Crude Oil: https://spectralworkbench.org/sets/3030; 5w30 5 drops per mL mineral oil: https://spectralworkbench.org/sets/3027; Diesel: https://spectralworkbench.org/sets/3026; 5W30 1 drop per 1 Ml mineral oil: https://spectralworkbench.org/sets/3025; 20W50: https://spectralworkbench.org/sets/show/3021; Field Samples Boq 1: https://spectralworkbench.org/sets/show/3020; This sample showed Boq 2: https://spectralworkbench.org/sets/3033; Boq 3: https://spectralworkbench.org/sets/show/3032 Boq 4 (road blank): https://spectralworkbench.org/sets/3024; Mineral Oil Blank: https://spectralworkbench.org/spectrums/64118.
Of the field samples Boq 1 was the one with greater response (a 1/3 dilution of the original extract was used for the analysis) in contrast with other samples from oily spots (Boq 2 and Boq 3) which extracts needed to be analyzed without dilution to be able to record a visible spectral structure. Boq 2 produced a slight signal in the green zone of the spectrum. Boq 4, the asphalted road extract without oily spots, could not be distinguished from the Mineral Oil Blank.
Overall, this work confirmed that extraction from pavement is feasible with little or no interference under the conditions studied. The pavement from which oily residues were extracted was either paint covered cement or weathered asphalt. We expected that the sample collected from the painted surface would produce the best spectral structure, however, it was the least detectable (Boq2). The other sites consisted of porous weathered asphalt which may have provided with additional surface for the accumulation of oil contamination.
These preliminary results are promising, however, more work should be conducted with extracts of asphalted roads at different weathering stages. In addition, samples from parking lots soon after the onset of rains should be collected to evaluate the possibility of sampling quantifying oil-sheens that are discharged into the storm sewage systems. Furthermore, the detection of other types of other fluorochromes should be evaluated as the kit may be adapted to other techniques in microbiology or water transport studies.