Method for determining molecular weight of polymers

The invention is a method for mass analysis of polymers by mobility measurements of charge reduced ions generated by electrosprays of polymers using solvents having high dielectric constants. Polymer ions formed by electrospray carry a level of charge proportional to their length and hence their mass. The number of charges on the resulting polymer ions is reduced to unity in a radioactive source. The mobility distribution of the reduced charge polymer ions is then measured in a high resolution differential mobility analyzer (DMA). A relation Z(m) between the mobility Z of a polymer and its mass m is determined using narrowly distributed polymer mass standards. Polymers analyzed in accordance with the invention include both water soluble and water insoluble polymers having weight average molecular weights between 1 kilodaltons (kD) and 500,000 kD.