Abstract: A sample preparation process and apparatus are provided for samples to be analyzed subsequently, such as by liquid chromatography. The sample is passed in contact with an ion exchange polymer which is characterized by being capable of facilitating removal of one or more undesired ions from the sample to be replaced with an ion transferred from the bound exchange site of the polymer and through the polymer. The polymer is prewashed with water to remove substantially all leachable species from the polymer. In one embodiment, the polymer is coated with a color indicator capable of changing color when the polymer is depleted of the ion to be transferred therefrom. The ion exchange capacity of the apparatus can be significantly expanded by using a counter ion donating solution capable of replacing the bound ions at the ion exchange sites as they become exchanged for the undesired ions from the sample.