Pitoisuuskäyrä

Pitoisuuskäyrä, sometimes translated as concentration curve or fitted curve, is a graphical representation used in analytical chemistry and related fields to visualize the relationship between a measured signal and the concentration of a substance. This curve is typically generated by analyzing a series of samples with known concentrations, called standards, and plotting their corresponding signal intensities. The resulting data points are then used to construct a curve, often by fitting a mathematical model.

The shape of the pitoisuuskäyrä depends on the analytical method employed. For instance, in spectrophotometry, it often follows Beer-Lambert's law, resulting in a linear relationship within a certain concentration range. However, deviations from linearity can occur at higher concentrations due to various factors. Other methods may yield non-linear curves, such as sigmoidal shapes common in immunoassays or enzyme kinetics.

The primary purpose of a pitoisuuskäyrä is to enable the accurate determination of unknown sample concentrations. Once the curve is established and validated, the signal measured from an unknown sample can be located on the y-axis, and the corresponding concentration can be read off the x-axis. This calibration process is fundamental to quantitative analysis, ensuring reliable and reproducible results. The accuracy and precision of the determined concentrations are directly influenced by the quality and range of the calibration standards used, as well as the appropriateness of the fitting model.