Total Organic Carbon (TOC) – More than just an Assessment of Water Quality

Introduction

Assessing water quality and our environmental impact is something that has become more and more important in recent years. In addition to naturally occurring cycles in the world climate, we have seen the accelerated effects of human living on our planet, our ecosystems and our water supplies. TOC analysis is an efficient way of checking water quality and our impact on the environment in a more environmentally friendly way. Unlike similar analysis such as chemical oxygen demand (COD) testing, it doesn’t use the same levels of harsh chemicals like potassium dichromate, so there is very little in terms of waste chemicals for disposal. This makes it a more sustainable and green approach. It is also versatile. Samples that can be analysed range from wastewater, seawater, solid samples right up to ultrapure water and water for injection. There are also other applications that can be adapted to fit the TOC analytic technique.

Preparation of clean drinking water and how TOC is a critical analytical aid. Image Source: Shimadzu

As we also move forward with sustainable initiatives such as green hydrogen generation, monitoring of carbon cycles and gaining a better understanding of how to utilize carbon sinks, we will see an increased need for TOC. Another key area which is often overlooked is the ability to treat and re-use water in large scale industries such as lithium-ion battery manufacturing which consume high volumes of water in their processes. The ability to re-use water multiple times before having to release to municipal treatment facilities has a significant positive effect on the overall environmental impact of a company with high water demands in addition to the cost savings that can be achieved by reduced consumption of water from local supplies.

What is TOC and how is it measured?

TOC is the amount of carbon in a sample that can be attributed to organic matter. This essentially allows the analyst to gauge the amount of microbial activity in the sample. TOC is measured by oxidizing the sample to form carbon dioxide and the levels of carbon dioxide are quantified by a detector. The most common detector is the non-dispersive infrared detector (NDIR) due to its combination of sensitivity and analytical range. TOC is most commonly quantified in one of two ways depending on the levels of organic carbon that are expected in the sample. The first way is to measure the total carbon and the inorganic carbon (IC) and perform a calculation of (TC-IC) to give the total organic carbon. The second way is to acidify the sample and purge it with carbon dioxide free air or nitrogen. This remaining carbon is then oxidized, and the resulting carbon dioxide is measured. This method is called the NPOC measurement as it measures the non-purgeable organic carbon in the sample.

What is Green Hydrogen and why is it important?

Hydrogen is produced as a fuel source or potential fuel source for consumption in heavy industries such as steelmaking, powering of heavy goods vehicles and aviation to decarbonize these industries. It is also being used as a long-term energy store which could be used to ensure sufficient grid capacity during high usage seasonal periods such as we currently see in Winter months.

There are two types of hydrogen production currently ongoing around the world; grey and green production. Grey hydrogen is hydrogen that’s generated by electrolysis of ultrapure water using fossil fuels such as coal or gas. Green hydrogen is generated by the same electrolysis process of ultrapure water but uses renewable energy sources. Hydrogen generation requires a large volume of ultrapure water, and the efficiency of the generation technique is dependent on both a consistent high throughput of this water which in turn is reliant on a consistent supply of electricity. For green hydrogen the electricity must come from sustainable sources such as offshore wind farms or solar energy or a combination of renewable sources. Maintaining a steady source of electricity from these renewable means will pose challenges but the benefits will be large given the potential to decarbonize heavily polluting industries.

Online monitoring of water quality for TOC and conductivity is a key part for any water purification plant. Monitoring water quality in this setting will help to ensure the quality of the water is sufficient for the hydrogen generation process. This in turn will help to ensure equipment is maintained in a good state by ensuring that adjustments are made and allowing processes to be paused if there is a change in water quality. This should keep any downtime to a minimum by signaling when maintenance work is needed to the water purification process and ensuring equipment will not be damaged or compromised with poor quality water unknowingly entering the process

The Importance of the Carbon Cycle 

Atmosphere carbon exchange cycle in nature

The carbon cycle is nature’s way of reusing carbon atoms, which travel from the atmosphere into organisms in the Earth and then back into the atmosphere over and over again. Most carbon is stored in rocks and sediments, while the rest is stored in the ocean, atmosphere, and living organisms. The events that comprise the carbon cycle are key to making the Earth capable of sustaining life.

Current trends in climate change will lead to higher ocean temperatures and acidity, thus modifying marine ecosystems. Also, acid rain and polluted runoff from agriculture and industry changes the ocean’s chemical composition. Such changes can have dramatic effects on highly sensitive ecosystems such as coral reefs, thus limiting the ocean’s ability to absorb carbon from the atmosphere on a regional scale and reducing oceanic biodiversity globally. We have already seen negative effects on the famous Great Barrier Reefs in Australia which have been increasingly affected by pollution and global warming events over the past 30 years. Arctic methane emissions indirectly caused by global warming also affect the carbon cycle and contribute to further warming.

Carbon sinks will also play an important role in this sustainability. A carbon sink is anything that absorbs more carbon from the atmosphere than it releases. Rainforests which have long played a significant role in this, have been depleted for farming and other developments over a number of years. Replacing these and reducing our impact on the climate and in turn the carbon cycle should be a focus going forward. Trying to maintain it in an optimal state should be a key area of focus for scientists and leaders around the world as this will be important for the sustainability life on Earth.

TOC can be used to measure the amount of organic, inorganic and total carbon in gas, liquid and solid samples so this analytic technique will continue to play a huge role in monitoring carbon cycles. This can be used to assess the impact of both naturally occurring and anthropogenic (caused by people) climate change on the carbon cycles.

Shimadzu and Mason Technology – Excellence in Science

Shimadzu, available exclusively from Mason Technology, offers a comprehensive range of Total Organic Carbon (TOC) analysers, renowned for their precision, reliability, and innovative technology, catering to diverse applications in environmental, pharmaceutical, and industrial water quality testing.

Highlights from their TOC Instrument Range 

• TOC-L – Benchtop TOC instrument with a wide range of 4 μg/L to 30,000 mg/L that can be customised to analyse solid samples with the SSM-5000A module and also total nitrogen using the TNM-L module
• TOC-1000e – The pioneering TOC-1000e system has the world’s smallest and lightest cabinet and provides high-sensitivity detection, making it ideal for fields requiring high-purity water applications, such as precision manufacturing, pharmaceuticals and semiconductors
• Full range of Shimadzu TOC Instruments