1. Symptom → Cause → Fix Matrix

Symptom	Most likely causes	First fix
Noisy baseline	Lamp ageing, dirty windows, air bubbles in cell	Clean cells; degas sample; check lamp hours
Baseline drift over time	Warm-up not complete, temperature change	Warm up 30 min; control lab temperature
Absorbance spikes	Air bubbles, particles in beam path, cell not seated	Tap/fill cell; check alignment; filter sample
Poor repeatability	Cell orientation, evaporation, dirty windows	Mark orientation; cover cell; clean windows
Negative readings	Blank mismatch, dirty reference cell	See negative absorbance guide
Flat/low signal	Wrong Z dimension, cell too empty	Check Z dimension; fill above beam

2. Cell Checks (5 Minutes)

• Windows clean? — inspect both optical faces; clean per protocol.
• Matched pair? — sample vs reference transmission should match within tolerance.
• Same path length? — mixing 10 mm and 5 mm cells in one run gives nonsense.
• Filled correctly? — sub-micro cells need volume above the beam; check the Z dimension.
• No bubbles? — gently tap the cell after filling.

3. Instrument Checks

• Warm-up 15–30 minutes before critical measurements.
• Verify wavelength calibration with a holmium or didymium filter.
• Check lamp age — deuterium lamps fade in the UV end first.
• Run an air baseline and a water baseline to separate cell vs instrument problems.

4. When to Call It a Cell Problem

If the instrument baseline is clean with empty cells but degrades with a specific cell, the cell is the problem — usually a scratched window, etched surface or a failing glue line. Replacement is cheaper than a service call.

Related: Cuvette Care Guide · Path Length Guide · Size Calculator · Path Length Calculator · Brand Alternatives · Contact Scuvette

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