TOC History – How everything began
While Shimadzu has been instrumental in shaping TOC analysis over the past few decades, the foundation was laid further back in time.
The Flemish scientist Jan Baptist van Helmont realized in the 1630s that an air-like substance was released when wood and coal were burned - known today as carbon dioxide (CO2). He called it "gaz sylvestre" and thus coined the term "gas”. In 1756 Joseph Black demonstrated that CO2 occurred in natural air. He found that it could be created from other compounds, would extinguish a flame and was exhaled by humans. While doing research on magnesium carbonates, Black invented the analytical balance and promptly used it to measure CO2 by loss on ignition (LOI). The LOI test, in which samples are heated and the resulting reduction in mass is measured, was the first quantitative test for carbon. In 1938 carbon dioxide became directly quantifiable, when Erwin Lehrer and Karl Friedrich Luft introduced the “URAS” NDIR spectrometer. It is used for the selective determination of components in gases, such as CO2 in air. In 1967, James Teal at Dow Chemical Company patented a “Method and Apparatus for Determination of Total Carbon Content in Aqueous Systems.” This combustion device manually injects aqueous samples into a stream of oxygen flowing through a 700–900 °C furnace measuring the CO2 generated from oxidized carbon by infrared absorbance. Teal’s device appears to be the first combustion TOC analyzer for water.
The same year, Shimadzu began work on their first internal prototype for a TOC instrument, the “TOC-1”, but it was not until 1972 that the first instruments were released to the market, the TOC-10 laboratory TOC analyzer and the TOC-100 Online TOC analyzer. Both systems were optimized and ideas for improvements were generated. Through these improvements, Shimadzu's unique TOC analyzers took shape. As a result, shortly after the Online TOC analyzers TOC-401 and TOC-402 could be released as successors of TOC-100, as well as the laboratory successor model TOC-10A. TOC-10A allowed manual injection of water samples into a 950°C hot furnace under oxygen atmosphere using a micro syringe. The unit hat separate injection channels for Total Carbon (TC) and Inorganic Carbon (IC) determination, so that Total Organic Carbon (TOC) could be determined by the difference method (TOC = TC-IC). The sealing of these injection ports was further improved in the TOC-10B, which was released in 1975. The initial TOC analyzer models were quite successful in Japan, so that Shimadzu became a major player for TOC instruments in their domestic market by the end of the 1970s. However, since the market in Japan was still relatively small and the company wanted to expand its business, it was decided to introduce the devices overseas as well. The first overseas debut of Shimadzu TOC analyzers was at an international exhibition held in Tianjin, China in 1980, where the TOC-10B was exhibited as one of Shimadzu's various analytical instruments.
Back then, CO2 peaks were not integrated, but printed on chart paper and compared with a prior calibration by peak height. In order to be able to read as accurately as possible, the peaks had to be particularly sharp and narrow, which was achieved by the high combustion temperatures of up to 1000°C. A single measurement took about 4 minutes. However, at these temperatures, salts contained in samples became a problem, as molten salts damage catalysts and combustion tubes, resulting in high maintenance requirements. But the developers at Shimadzu were able to find a practical solution here as well.