Apparatus for treating a liquid sample containing organic material comprising: (a) a reactor having reactor inlet and outlet ports and a reactor interior for containing a liquid sample under above-ambient temperature and pressure conditions; (b) high-pressure fluid reactor valve members (28,29) at said reactor inlet and outlet ports; (c) a reactor heating system; and, (d) a reactor cooling system; characterized in that: said reactor valve members are adapted to allow fluid flow respectively into or out of the reactor interior when in an open-valve mode or, alternatively, to seal the reactor interior when in a closed-valve mode; said reactor heating system is adapted to rapidly and cyclically heat the reactor interior and a liquid sample sealed in the reactor interior to a temperature of 150°C to 650°C or higher, while the reactor interior and the reactor valve members maintain the sample under sealed conditions; and, said reactor cooling system is adapted to rapidly and cyclically cool the reactor interior and a reactor product sealed in the reactor interior following a heating cycle; and that said apparatus further comprises (e) a chemical detector for detecting carbon, nitrogen or sulfur oxidation products downstream of the reactor; and one or more additional inlets selected from an acid reagent inlet, an oxidizer reagent inlet and a dilution water inlet; a mixing/sparging chamber upstream from the reactor where a combination of a liquid sample and one or more other liquids can be either mixed or mixed and simultaneously sparged with sparge gas. (a) a reactor having reactor inlet and outlet ports and a reactor interior for containing a liquid sample under above-ambient temperature and pressure conditions; (b) high-pressure fluid reactor valve members (28,29) at said reactor inlet and outlet ports; (c) a reactor heating system; and, (d) a reactor cooling system; characterized in that: said reactor valve members are adapted to allow fluid flow respectively into or out of the reactor interior when in an open-valve mode or, alternatively, to seal the reactor interior when in a closed-valve mode; said reactor heating system is adapted to rapidly and cyclically heat the reactor interior and a liquid sample sealed in the reactor interior to a temperature of 150°C to 650°C or higher, while the reactor interior and the reactor valve members maintain the sample under sealed conditions; and, said reactor cooling system is adapted to rapidly and cyclically cool the reactor interior and a reactor product sealed in the reactor interior following a heating cycle; and that said apparatus further comprises said reactor valve members are adapted to allow fluid flow respectively into or out of the reactor interior when in an open-valve mode or, alternatively, to seal the reactor interior when in a closed-valve mode; said reactor heating system is adapted to rapidly and cyclically heat the reactor interior and a liquid sample sealed in the reactor interior to a temperature of 150°C to 650°C or higher, while the reactor interior and the reactor valve members maintain the sample under sealed conditions; and, said reactor cooling system is adapted to rapidly and cyclically cool the reactor interior and a reactor product sealed in the reactor interior following a heating cycle; and that said apparatus further comprises (e) a chemical detector for detecting carbon, nitrogen or sulfur oxidation products downstream of the reactor; and