TOC History – Multifunctionality and High Sensitivity
In the year 2000, Shimadzu introduced the TOC-V combustion TOC analyzer, which further improved the functionality of its unique ISP module by expanding the 4-port valve to an 8-port valve. Experience with this change had already been gained with the introduction of the TOC-4000 series and had proven to be very effective. In combination with various additional devices, the TOC-V expanded the range of applications to include volatile organic carbon (POC) measurement and simultaneous measurement of TOC and total nitrogen (TNb). The new autosampler ASI-V could be equipped with inbuilt magnetic stirrers and a mechanism that allowed samples to be acidified and sparged in the sampler; both functions being essential in proper handling of particle-containing samples. A new NDIR infrared detector that uses only one beam path but has an auto-zero function has been introduced for the TOC-V. This eliminated the need for users to manually zero the baseline.
TOC-V’s PC software, “TOC-Control V” had inbuilt functions necessary for GMP and GLP use, such as user administration and audit trail. Furthermore, TOC-V had the possibility to be integrated into Shimadzu’s CLASS-Agent client/server software platform to facilitate electronic record and electronic signature functions. The TOC-V series thus allowed compliance with related regulations, such as FDA 21 CFR Part 11. With an increasingly wide range of possible applications, the TOC-V has become a best-seller for Shimadzu, further consolidating its market leadership.
To enable precise measurement in even lower concentration ranges, Shimadzu expanded the TOC-V series two years later with the TOC-V wet chemical TOC analyzer (TOC-V W). Water injected into a hot furnace does create strong pressure surges, which is why the maximum injection volume in combustion analyzers is limited in order to prevent damage. In the TOC wet chemical series, samples are oxidized by a combination of UV-irradiation, persulfate oxidizer solution and heat (80°C). This system allows much higher injection volumes to be used compared to combustion analyzers and thus facilitates lower limit of detection and increased precision in low measurement ranges. While the oxidation is not as powerful as combustion, it is nevertheless commonly used for the analysis of pure water in pharmaceutical or semi-conductor laboratories.
The TOC-4110 Online TOC Analyzer, released in 2003, benefited from many improvements introduced in the TOC-V laboratory series. The injection syringe was improved so that maintenance was only required after many movement cycles. The TN detector unit, first introduced in the TOC-4100, was miniaturized and its robustness increased. By sharing parts between the online and laboratory instruments, the price of the system could be reduced. All optimizations and improvements together led to a significant reduction in maintenance costs for the system operators.
Saline samples, such as seawater or process water, are often a challenge for TOC analysis. Shimadzu's 680°C high-temperature catalytic oxidation (HTCO) method simplified analyses by the very fact that the combustion temperature is below the melting points of common salt. Salts do not form solid melts here, but precipitate on the catalyst as powder which is carried away with the condensate. At high TOC levels, the sample can additionally be automatically diluted to reduce the injected salt content. But at high salt and low TOC levels, where dilution is not feasible, even this powdered salt can cause clogging and thus requires frequent maintenance. Shimadzu's answer to this is the so-called high salt combustion tube, made available for the first time in the TOC-4110 series. It has an optimized geometry, so that particulate salt can very easily pass through the combustion tube. This new catalyst rapidly proved its worth in online analysis, so that further cost reductions in maintenance could be realized.