Particles may be injected into a matrix for concentration by scodaphoresis using a quadrupole injection field. Particles may be injected from two or more sample chambers simultaneously. Particle injection may be performed simultaneously with performing scodaphoresis. In some embodiments the particles are concentrated into a well containing fluid. The well can extend out of a plane of the matrix. Altering the relative phases of components of a scodaphoresis field permits concentration of selected particles and exclusion of other particles. Scodaphoresis methods may be applied to DNA, other bio-molecules and other particles.