Total Recoverable Hydrocarbons or Total Petroleum Hydrocarbons
Total Petroleum Hydrocarbons (TPH)is sometimes referred to as mineral oil, hydrocarbon oil, extractable hydrocarbons, and oil and grease.
There are many analytical techniques available that measure TPH concentrations in the environment. No single method measures the entire range of petroleum-derived hydrocarbons. Because the techniques vary in the way hydrocarbons are extracted, cleaned up, and detected, they each measure slightly different subsets of the petroleum-derived hydrocarbons present in a sample.
The chemical composition of petroleum products is complex and change over time following release into the environment. Because petroleum and petroleum-derived products are such complex mixtures, there is no single “best” method for measuring all types of petroleum contamination.
These factors make it difficult to select the most appropriate analytical methods for evaluating environmental samples. There are several analytical methods for quantifying petroleum fractions. These include gas chromatography, infrared spectrometry, gravimetry and immunoassay measurements.
Some methods are appropriate for gasoline-contaminated samples while others are designed for hydrocarbon contamination such as jet or diesel fuel. Some methods measure more compounds than other methods because they employ more rigorous extraction techniques or more efficient solvents.
Total Petroleum Hydrocarbons
The definition of TPH depends on the analytical method used because the TPH measurement is the total concentration of the hydrocarbons extracted and measured by a particular method.
Summary of analytical methods
The results can thus be expressed in relation to hydrocarbon ranges (C6-C9, C10-C15, C16-C28). Best sensitivity for volatile hydrocarbons (C6-C9 range, VOC’s, BTEX) is achieved by using GCMS headspace or ‘purge and trap’ techniques.
Sample collection / preservation
All samples for hydrocarbon analysis should be taken and stored in glass bottles or jars with a tightly sealed lid. Water samples should be filled to the top of the bottle to minimise the headspace.
At MPL Laboratories, we have new instruments and dedicated analysts to help with the assessment of TPH. Contact us to see how we can work together to give you the best solution.
TPH is analysed by GCFID (Gas Chromatography using a Flame Ionisation Detector). The TPH is extracted from the sample with solvent, and injected onto a GC column. A flow of inert gas sweeps the sample through a narrow column, separating the components. The effluent from the GC column passes through the flame of the non-selective detector, which breaks down organic molecules and produces ions. The ions are collected and produce a measurable electrical signal used to confirm the identity and amount of the compounds of interest.
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