Can I use the Hach total organic carbon (TOC) lab method for testing seawater?
Testing for Total Organic Carbon in seawater or brine
Seawater or brine samples cannot be measured with the Hach TOC method due to the high levels of chloride in these samples. Chloride interferes with LR TOC (method 10129) at 500 mg/L, LR (method 10267) at 1000 mg/L, at MR (method 10173) at 1500 mg/L, HR (method 10128) at 5000 mg/L and HR (method 10267) at 1400 mg/L. Chloride interferes by generating chlorine gas during the digestion and bleaching the indicator, which gives lower than actual results. Seawater contains about 19,000 mg/L chloride.