Emissive compositions with internal standard and related techniques

A method for quantitative determination of the concentration of an analyte, comprising:

• providing a particle comprising a polymer material and a species, wherein, upon exposure to a set of conditions, the polymer material has a first emission and the species has a second emission, wherein the maximum of the first emission and the maximum of the second emission are separated by at least 50 nm;
• determining a first ratio between a characteristic of the first emission and a characteristic of the second emission;
• exposing the particle to an analyte, wherein the analyte interacts with the polymer material to produce a third emission;
• determining, upon exposure to said set of conditions, a second ratio between a characteristic of the second emission and a characteristic of the third emission, wherein the second ratio is different than the first ratio;
• and
• determining the difference between the first ratio and the second ratio, thereby quantitatively determining the concentration of the analyte.