A visible spectrophotometer is in a class of spectroscopy instruments that monitor the interaction of a substance with light from the visible part of the electromagnetic radiation spectrum. A visible spectrophotometer typically measures the absorption level of one monochromatic visible frequency at a time and then sums up those individual absorption levels to draw a spectrum. This type of spectrophotometer provides high-quality, reliable analytics. However, you need to consistently maintain your equipment for it to perform optimally.
The following is a general list of good maintenance practices for a visible spectrophotometer:
- Place your visible spectrophotometer in a clean, dry, and dust-free environment.
- When using your spectrophotometer, ambient temperature and light levels should remain as constant as possible.
- Adherance to standard operating procedures and good laboratory practice should be monitored with regular calibration checks and a suitable quality control program if required.
- Ensure that there is nothing additional in the sample chamber which could block the light path during calibration and sample measurement.
- Do not divert the light path using a mirrored surface within the sample compartment.
- The correct selection of sample containers is imperative for accurate and reproducible results.
- Samples and standards should not be stored in open cuvettes or sample containers as evaporation will change the value and lead to staining of the walls which may be irreversible. If stored in stoppered and sealed cuvettes, they should be filled with little or no air space and the values regularly checked against a reference standard or quality control material.
- Samples should be allowed to equilibrate to ambient temperature before measurement (unless a suitable temperature controlled sample holder is in use). Temperature change during measurement may cause air bubbles to form on the walls of the sample holder. This is a common cause of drift during measurement.
- In the preparation of samples and standards, high-grade borosilicate glass and AR grade chemicals and reagents must be used. Good quality deionized water or other suitable solvents must be used for dissolving or diluting samples, chemicals, and reagents.
- All measurements require calibration to a blank, for maximum accuracy this should be prepared with care using the same deionized water or solvent used for dissolving or diluting the sample. Where reagents are added to the sample to produce a color proportional to its concentration a ‘sample based’ blank should be used. In this case, the blank should consist of all reagents or chemicals to be used, except the sample which will produce the color to be measured.
- Deviations from the Beer-Lambert Law may occur at high and low concentrations giving non-linear response during sample concentration measurements. For all new methods, a linear range should be defined by the preparation of a calibration curve. The quantitation mode may be used to construct such a curve against which sample results are automatically measured.
- Cuvettes and sample holders must be filled to a minimum level which covers the light path.
- Be sure to consult your owner’s manual for maintaining your specific type of equipment.
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