A method of analysing behaviour of a system comprising a chemical and/or biological sample in a liquid medium, the method comprising: a first cycle comprising: - a first reaction step comprising allowing the chemical and/or biological sample to react in a reaction vessel for a first reaction step time in a closed system in a liquid medium; and - a first sampling step comprising the sequential steps of: (i) combining and substantially homogenising a first compensation liquid of known, predetermined weight and composition with the liquid medium; and (ii) removing a portion of the homogenised liquid medium for analysis; and a second cycle comprising - a second reaction step comprising allowing the chemical and/or biological sample to react in the reaction vessel for a second reaction step time in a closed system in the liquid medium resulting from the first cycle; and - a second sampling step comprising the sequential steps of: (i) combining and substantially homogenising a second compensation liquid of known, predetermined weight and composition with the liquid medium from the second cycle; and (ii) removing a portion of the homogenised liquid medium for analysis. a first cycle comprising: - a first reaction step comprising allowing the chemical and/or biological sample to react in a reaction vessel for a first reaction step time in a closed system in a liquid medium; and - a first sampling step comprising the sequential steps of: (i) combining and substantially homogenising a first compensation liquid of known, predetermined weight and composition with the liquid medium; and (ii) removing a portion of the homogenised liquid medium for analysis; and - a first reaction step comprising allowing the chemical and/or biological sample to react in a reaction vessel for a first reaction step time in a closed system in a liquid medium; and - a first sampling step comprising the sequential steps of: (i) combining and substantially homogenising a first compensation liquid of known, predetermined weight and composition with the liquid medium; and (ii) removing a portion of the homogenised liquid medium for analysis; and a second cycle comprising - a second reaction step comprising allowing the chemical and/or biological sample to react in the reaction vessel for a second reaction step time in a closed system in the liquid medium resulting from the first cycle; and - a second sampling step comprising the sequential steps of: (i) combining and substantially homogenising a second compensation liquid of known, predetermined weight and composition with the liquid medium from the second cycle; and (ii) removing a portion of the homogenised liquid medium for analysis. - a second reaction step comprising allowing the chemical and/or biological sample to react in the reaction vessel for a second reaction step time in a closed system in the liquid medium resulting from the first cycle; and - a second sampling step comprising the sequential steps of: (i) combining and substantially homogenising a second compensation liquid of known, predetermined weight and composition with the liquid medium from the second cycle; and (ii) removing a portion of the homogenised liquid medium for analysis.