Biomolecular Assay Type  Potential Batch to Batch Variability 
Colorimetric Unique buffer components
Chromogenic reagent
Commercial kit active components 
Enzymatic Unique buffer components
Substrates
Enzymes
Cofactors
Detection reagents
Commercial kit active components 
Chromatographic Unique buffer components
Labile mobile phase solvents
Chromatography column resin
Derivatization or conjugation reagents 
Electrophoretic Unique electrode buffers
Gel matrix reagents
Sample treatment reagents
Staining reagents
Commercial kit components 
Immunological Primary antibodies
Secondary antibodies
Conjugated antibodies
Blocking reagents
Detection reagents
Commercial kit active components
Plastic cuvettes or micro titer plates 
Ligand Binding  Unique buffer components
Target receptor
Target ligand
Detection reagents
Commercial kit active components
Plastic cuvettes or microtiter plates 
Cell Based Bioassay  Cell seed stock (homogeneity and viability)
Cell culture (passage number and density)
Media components
Growth factors
Antimicrobial agents
Harvest reagents (e.g., trypsin)
Cell reactants (e.g., induction compounds)
Plastic flasks or plates 
Table 6: Different types of methods and components that can contribute to
variability in performance of an analytical method.