Before powering the unit, the operator must ensure the physical integrity of the system. The initialization process begins with the flow path. The manual dictates the importance of priming the system with the mobile phase to remove air bubbles, which can scatter light and cause significant baseline noise. Once the fluid path is established, the lamp should be ignited. The SPD-20A utilizes a deuterium (D2) lamp for UV detection and an optional tungsten lamp for the visible range. A critical operational note found in the user manual is the warm-up period; the lamp requires approximately 30 to 60 minutes to stabilize. Attempting to run an analysis before thermal equilibrium is reached will result in baseline drift and unreliable quantification.
variant, it adds a to the standard Deuterium lamp. This allows it to cover the full spectrum (190–900 nm) with simultaneous illumination , meaning no warm-up delays when switching between UV and visible light ranges. UV-VIS detector / Photodiode Array Detector - Shimadzu shimadzu spd20a user manual
| Symptom | Probable Cause | Corrective Action | |---------|----------------|--------------------| | High baseline noise | Air bubbles in cell | Flush with degassed mobile phase or remove cell and rinse. | | Negative peaks | Sample absorbs less than mobile phase at set wavelength | Change wavelength or check mobile phase UV cutoff. | | Lamp fails to ignite | Lamp expired or power supply issue | Check lamp hours; replace D2 lamp. | | No signal at high sensitivity | Flow cell window dirty | Clean cell with 1M HNO₃, then water, then methanol. | | Wavelength error | Stepper motor failure or filter stuck | Run Wavelength Calibration from service menu (qualified personnel only). | Before powering the unit, the operator must ensure
AU max, making it highly sensitive for trace component detection. Up to 2.5 AU (ASTM standard). Bandwidth: 8 nm. Once the fluid path is established, the lamp
Flow Cell CleaningIf you notice ghost peaks or a drifting baseline, your flow cell may be contaminated. Flush with a strong solvent (like Isopropanol).