A method for attaching reaction components to charge sensors, comprising (a) providing a solid support comprising a plurality of charge sensors, wherein each of the charge sensors is a field effect transistor and has a capacity to attach a plurality of reaction components; (b) providing a fluid comprising a plurality of reaction components of a particular type; (c) contacting the solid support with the fluid under conditions wherein (i) the plurality of reaction components of the particular type are in fluid communication with the plurality of charge sensors, (ii) a greater number of reaction components of the particular type is in the fluid than the number of charge sensors on the solid support; and (iii) reaction components of the particular type from the fluid attach to the charge sensors, thereby forming modified charge sensors that are attached to multiple reaction components of the particular type from the fluid; and (d) removing, degrading or inactivating one or more of the reaction components of the particular type from each of the modified charge sensors to leave a single one of the reaction components of the particular type attached to at least one of the modified charge sensors, wherein one of: (iv) removing involves cleaving cleavable tethers to which the reaction components are attached; or (v) degrading involves binding a protection moiety to the single one of the reaction components, and then degrading any non-protected reaction components; or (vi) inactivating involves binding a chemically or photochemically active oligonucleotide analog to one or more polymerase active sites, and then applying a chemical or photochemical treatment to render the one or more of the reaction components inactive; or (vii) removing, degrading, or inactivating of the excess reactive components from the charge sensors is monitored to determine the extent of removal, degradation or inactivation; or (viii) removing, degrading, or inactivating is monitored with a different sensor to distinguish the presence of reaction components at the surface of the reaction components. (a) providing a solid support comprising a plurality of charge sensors, wherein each of the charge sensors is a field effect transistor and has a capacity to attach a plurality of reaction components; (b) providing a fluid comprising a plurality of reaction components of a particular type; (c) contacting the solid support with the fluid under conditions wherein (i) the plurality of reaction components of the particular type are in fluid communication with the plurality of charge sensors, (ii) a greater number of reaction components of the particular type is in the fluid than the number of charge sensors on the solid support; and (iii) reaction components of the particular type from the fluid attach to the charge sensors, thereby forming modified charge sensors that are attached to multiple reaction components of the particular type from the fluid; and (i) the plurality of reaction components of the particular type are in fluid communication with the plurality of charge sensors, (ii) a greater number of reaction components of the particular type is in the fluid than the number of charge sensors on the solid support; and (iii) reaction components of the particular type from the fluid attach to the charge sensors, thereby forming modified charge sensors that are attached to multiple reaction components of the particular type from the fluid; and (d) removing, degrading or inactivating one or more of the reaction components of the particular type from each of the modified charge sensors to leave a single one of the reaction components of the particular type attached to at least one of the modified charge sensors, wherein one of: (iv) removing involves cleaving cleavable tethers to which the reaction components are attached; or (v) degrading involves binding a protection moiety to the single one of the reaction components, and then degrading any non-protected reaction components; or (vi) inactivating involves binding a chemically or photochemically active oligonucleotide analog to one or more polymerase active sites, and then applying a chemical or photochemical treatment to render the one or more of the reaction components inactive; or (vii) removing, degrading, or inactivating of the excess reactive components from the charge sensors is monitored to determine the extent of removal, degradation or inactivation; or (viii) removing, degrading, or inactivating is monitored with a different sensor to distinguish the presence of reaction components at the surface of the reaction components. (iv) removing involves cleaving cleavable tethers to which the reaction components are attached; or (v) degrading involves binding a protection moiety to the single one of the reaction components, and then degrading any non-protected reaction components; or (vi) inactivating involves binding a chemically or photochemically active oligonucleotide analog to one or more polymerase active sites, and then applying a chemical or photochemical treatment to render the one or more of the reaction components inactive; or (vii) removing, degrading, or inactivating of the excess reactive components from the charge sensors is monitored to determine the extent of removal, degradation or inactivation; or (viii) removing, degrading, or inactivating is monitored with a different sensor to distinguish the presence of reaction components at the surface of the reaction components.