Apparatus and methods for detecting and quantifying analytes

A method for detecting and quantifying analytes in a sample, the method comprising:

• preparing a sample solution containing any analytes of interest in the sample and one or more internal standards;
• performing a chromatographic separation step on the sample solution using a chromatographic column, the chromatographic resolution (R) being less than about 1.5, the separation step operative to differentially retard progress of different ones of the one or more internal standards and analytes of interest such that at an output of the separation step, concentrations of different ones of the internal standards and analytes of interest reach maxima at different times;
• passing aliquots of the sample solution eluted from the chromatographic column to a flow cell;
• performing an electrochemical detection step using the flow cell, the electrochemical detection step comprising acquiring a time series of electrochemical signatures of the sample solution present at the output of the separation step, the detection step operative to conduct electrochemical measurements on some or all batches of eluent introduced into the flow cell and to take electrochemical measurements during intervals in which the flow is stopped or slowed down;
• and
• processing the time series of electrochemical signatures to separately, for each of the analytes of interest, determine whether or not a detectable amount of the analyte of interest is present in the sample and, if a detectable amount of the analyte of interest is present in the sample, quantify the amount of the analyte of interest present in the sample.