Using UV Abs. as a TOC Surrogate
Total Organic Carbon (TOC)
Total Organic Carbon (TOC) is a measurement of the total amount of carbon in an organic compound. TOC is commonly used as measurement of water quality and along with UVT provides a comprehensive scope of organic contamination in water. You can find TOC measurement devices in laboratories, Water Treatment Plants (WTPs) and Wastewater Treatment Plants (WwTPs). Measuring TOC involves oxidizing all the carbon-containing compounds in a sample to carbon dioxide (CO2) this can then be quantified and therefore monitored. Measuring TOC can help determine the integrity of water treatment processes. TOC is a recognised parameter and is used in a regulatory manor for meeting environmental standards.
UV Absorption can be used as a surrogate measurement for Total Organic Carbon (TOC). This is because organic compounds absorb UV radiation at a characteristic wavelength UV254. As a result, the amount of UV radiation absorbed by a sample at 254 nm can be used to estimate the concentration of organic compounds in the sample, which is a measure of its TOC content.
The Ultraviolet Absorption (UVA) measurement is often expressed as Spectral Absorption Co-efficient (SAC) and is used as a surrogate for TOC in applications where a direct TOC measurement is not required or is not feasible. However, it's important to note that the correlation between UV Absorption and TOC can vary depending on the specific nature of the organic compounds in the sample, and other factors such as the presence of inorganic compounds, pH, and temperature can also affect the UV absorption measurement.
Using Ultraviolet Absorbance (UVA) to obtain surrogate Total Organic Carbon (TOC) results has several benefits. Here are some of the advantages:
Cost-Effective: The use of UVA as a surrogate for TOC measurement can significantly reduce the capital expenditure required for a TOC analyser. There is no need to purchase expensive reagents or chemicals, and the device itself is simple with no moving parts, leading to low maintenance and repair costs.
Time-Efficient: UVA analysis is fast, providing 35 times more results in the same time as a flash test and 700 times more results than a lab reagent test. This enables quick monitoring and trend analysis of TOC levels, including detecting short spikes or dips.
Portable: UVA systems are portable and can be easily relocated as needed, making it a cost-effective option for monitoring TOC levels in different locations. This portability also makes it easier to track changes in TOC levels in real-time.
Complementary Measurement: UVA can serve as a complementary measurement tool to fill in the gaps between flash measurements, detecting spikes and dips in TOC levels during the gap between readings.
Non-Destructive: UVA analysis is non-destructive and non-invasive, which means the same sample can be used for other tests or analyses without further preparation. Without the use of consumables.
In conclusion, the use of UVA to obtain surrogate TOC results offers several benefits, including affordability, efficiency, portability, comprehensive measurement and non-destructive analysis. It is a useful tool for monitoring TOC levels in various applications, such as wastewater treatment plants, pharmaceuticals, and food and beverage production facilities.
How do you measure Total Organic Carbon?
Traditional methods of measuring Total Organic Carbon (TOC) involve the use of chemical reagents and advanced laboratory equipment. The most common methods include:
High-Temperature Catalytic Oxidation: This method involves heating the sample at high temperatures (typically around 1,200°C) in the presence of a catalyst to convert all the organic carbon into carbon dioxide (CO2). The CO2 is then measured using infrared detectors to determine the amount of TOC in the sample.
Wet Chemical Oxidation: In this method, the sample is chemically oxidized using strong oxidizing agents, such as potassium permanganate or dichromate. The CO2 produced during the oxidation is then measured using infrared detectors to calculate the TOC content.
Ultraviolet Oxidation: This method uses ultraviolet light to oxidize the organic carbon in the sample to CO2, which is then measured using infrared detectors to determine the TOC content.
Non-Dispersive Infrared Spectroscopy: In this method, the sample is oxidized using a strong oxidizing agent, and the resulting CO2 is measured using infrared spectroscopy.
All of these traditional methods have their advantages and disadvantages, but they all require significant time and investment in equipment and reagents. They also tend to be less accurate and precise compared to more modern techniques such as UV254 monitoring.