An analyzer for determining the concentration of a label in a sample, wherein the label comprises a fluorescent moiety and the analyzer comprises: (a) a capillary flow cell; (b) a source of motive force for moving a sample in the capillary flow cell; (c) a lens (315, 303) that focuses electromagnetic radiation from an electromagnetic radiation source onto a single interrogation space in the capillary flow cell, when the interrogation space is defined to be smaller than the cross-sectional area of a sample stream; (d) one electromagnetic radiation detector operatively connected to the interrogation space that detects photons emitted from the interrogation space during a plurality of bins, wherein each bin represents a uniform predetermined period of time in a series of periods of time; and (e) a processor operatively connected to the detector, wherein the processor determines the concentration of the label in a sample by: (i) determining a threshold photon value corresponding to a background signal in the interrogation space, (ii) analyzing each bin as a "yes" or "no" for the presence of the label, where the total number of photons detected in each bin that exceeds the threshold value indicates that the label is detected and a photon signal having an energy level that is not greater than the threshold value indicates an absence of a label, and (iii) determining the concentration of the label in the sample by interpolation of a standard curve that is generated using one or more samples of known concentrations. (a) a capillary flow cell; (b) a source of motive force for moving a sample in the capillary flow cell; (c) a lens (315, 303) that focuses electromagnetic radiation from an electromagnetic radiation source onto a single interrogation space in the capillary flow cell, when the interrogation space is defined to be smaller than the cross-sectional area of a sample stream; (d) one electromagnetic radiation detector operatively connected to the interrogation space that detects photons emitted from the interrogation space during a plurality of bins, wherein each bin represents a uniform predetermined period of time in a series of periods of time; and (e) a processor operatively connected to the detector, wherein the processor determines the concentration of the label in a sample by: (i) determining a threshold photon value corresponding to a background signal in the interrogation space, (ii) analyzing each bin as a "yes" or "no" for the presence of the label, where the total number of photons detected in each bin that exceeds the threshold value indicates that the label is detected and a photon signal having an energy level that is not greater than the threshold value indicates an absence of a label, and (iii) determining the concentration of the label in the sample by interpolation of a standard curve that is generated using one or more samples of known concentrations. (i) determining a threshold photon value corresponding to a background signal in the interrogation space, (ii) analyzing each bin as a "yes" or "no" for the presence of the label, where the total number of photons detected in each bin that exceeds the threshold value indicates that the label is detected and a photon signal having an energy level that is not greater than the threshold value indicates an absence of a label, and (iii) determining the concentration of the label in the sample by interpolation of a standard curve that is generated using one or more samples of known concentrations.