Total Organic Carbon (TOC) analysis provides valuable data information for processes that require organic carbon analysis.Accurately measuring low TOC concentration (mg/L) is crucial for protecting equipment, controlling processes, and ensuring product qualityHowever, when the concentrations of sodium chloride (NaCl), chlor alkali, drug extracts, and extracts are too high, it can cause significant difficulties in TOC analysis, including:

Sievers^®The InnovOx TOC analyzer is particularly suitable for analyzing organic carbon in high salt samplesIts supercritical water oxidation (SCWO) technologyProvide precise, accurate, and sensitive TOC quantitative analysisBy eliminating inorganic interference, the oxidation efficiency is maximized. This technology can increase the amount of analyte in the reactor and more accurately control the gas and sample flow rates, thereby achieving a carbon detection limit (LOD) of 50 μ g/L in 6M NaCl.

SCWO technology oxidizes organic carbon molecules into carbon dioxide, which is then quantitatively analyzed using non dispersive infrared (NDIR) detection technology. The sample is heated and pressurized above the thermodynamic critical point of water. Under these conditions (375 ℃ and 220 bar), water becomes a supercritical liquid, and organic matter is highly soluble, while inorganic salts are insoluble. Even with high concentrations of inorganic salts in the solution, these conditions can improve oxidation efficiency, enabling the instrument to effectively measure TOC in corrosive and complex matrices.

The NDIR detector is stable and reliable, with a calibration frequency of 6 months.InnovOx TOC analyzer can accurately measure TOC in samples containing suspended and dissolved solids (<800 microns).

The LOD specification of InnovOx is 50 μ g/L. LOD is different from Method Detection Limit (MDL). pass15 repeated measurementsDetermine MDL using 6M NaCl blank sample made from ultrapure water. The standard deviation of the TOC result is σ, so the MDL is equal to 3 σ. In Figure 1, the standard deviation of the TOC data is 20 μ g/L, resulting in an MDL of 60 μ g/L. This is similar to the instrument's 50 μ g/L LOD specification, indicating that InnovOx's ability to detect organic carbon at a concentration of 250 μ g/L in Z is not affected by saturated NaCl solution.

Figure 1: Detection limit data of 6M NaCl method

Add 250, 400, and 600 μ g/L sucrose to a 6M NaCl solution respectively, and then analyze with InnovOx to determine the accuracy and precision of TOC recovery rate. The analysis parameters are: 3% (volume percentage) HCl, 25% (volume percentage) sodium persulfate oxidant, and 0.8 minutes of blowing time. The results in Table 1 show that the deviation of the recovery rate relative to the spiked value is within 5%. Even below 500 μ g/L, the relative accuracy is better than 15%. Figure 2 shows the comparison of recovery rate/standard sample. The recovery performance in the range of 250 μ g/L to 600 μ g/L further indicates that InnovOx is not affected by the 6M NaCl matrix, even below 1 mg/L TOC.

Table 1: Below 1mg/L in 6M NaCl

InnovOx TOC analysis performance

Figure 2: TOC recovery rate below 1 mg/L in 6M NaCl