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When testing TPH in water, the
sample is first shaken up and then 10 mL is measured out and transferred
to an extraction jar.
10 mL of hexane solvent is then added to the jar and the
extract is shaken for about one minute, giving the solvent ample time to
dissolve the contamination. The top layer of hexane extract is then poured
into a glass cuvette and placed into the UVF-3100 for analysis.
Both sample extracts and the oil
were first tested using Sitelab's TPH-Oil Calibration kit (CAL-057), which
produced low concentrations. When tested at a 100 ppm concentration, the oil
only read as 5.9 ppm, about 17 times lower. The lubricating oil used in this
study is very light and contains much higher proportions of non-fluorescent
aliphatic hydrocarbons compared to Sitelab's TPH-Oil standard, intended for
heavier, more aromatic types of oil contamination. For many oil in
water applications, however, the oil is available and can be diluted in
solvent and used for accurate TPH measurement, as illustrated below: |
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