A high throughput method to determine an amount of a comonomer in a copolymer sample of a copolymer system comprises the steps of providing a plurality of copolymer samples; creating an array of the copolymer samples; measuring a sample complex modulus of each of the copolymer samples at a comparison phase angle; and determining the amount of a comonomer in the copolymer sample by comparing the sample complex modulus to a calibration curve, wherein the calibration curve relates a concentration of the comonomer in the copolymer sample to a complex moduli of the copolymer sample determined at the comparison phase angle. A method of determining the amount of a comonomer in both a single copolymer sample, and in a high throughput scheme using the crossover modulus is also disclosed.