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Adjusting the operating range

The operating range of an interaction-based concentration assay is defined in terms of lower and upper limits that can be measured with acceptable performance. The range cannot extend at the lower limit beyond the limit of quantitation (LLOQ) for the assay, which is a combined measure of the observed response in relation to the noise level of the detection system and the experimental variations in sample preparation and measurement. The upper limit (ULOQ) is set by the characteristics of the assay format that determine the shape of the calibration curve. There may in some cases be an upper limit imposed by the detection system. Samples with concentrations above the upper limit of the operating range cannot be measured without prior dilution.

The main factors influencing the operating range of an assay are the affinity of the detecting molecule for the analyte, the concentration of detecting molecule and the contact time of the sample with the sensor surface. The ways in which the operating range can be adjusted differ according to the format of the assay.

See also

List of help files

Assay setup for concentration analysis

Operating range for direct binding assay

Operating range for inhibition assay