Possible Cause
Solution
| Negative direction (gradient elution) - absorbance of mobile-phase A | Use non-UV absorbing mobile phase solvents; use HPLC grade mobile phase solvents; add UV absorbing compound to mobile phase B. |
| Positive direction (gradient elution) - absorbance of mobile phase B | Use higher UV absorbance detector wavelength; use non-UV absorbing mobile phase solvents; use HPLC grade mobile phase solvents; add UV absorbing compound to modile phase A. |
| Positive direction - contamination buildup and elution | Flush column with strong solvent; clean up sample; use HPLC grade solvents |
| Wavy or undulating - temperature changes in room | Monitor and control changes in room temperature; insulate column or use column oven; cover refractive index detector and keep it out of air currents. |