The accuracy of a spectrophotometer affects the quality of specimen measurements. The proper functioning is determined by the precision of various parameters of its internal optical setup. If you want to guarantee the highest performance possible of your spectrophotometer, it needs to be calibrated. When calibrating a spectrophotometer, a blank solution is required to provide absorbance of the said solution as a zero reference when conducting a spectroscopic analysis. When a spectrophotometer is accurately calibrated, you can quickly determine a substance’s absorbance of light at a specific wavelength. It is essential to calibrate your spectrophotometer to maintain its baseline for future experiments. A specialist best handles spectrophotometer calibration. At Biotechnical Services Inc., we offer efficient and scientific spectrophotometer calibration in San Diego and the larger California region.

Spectrophotometers are usually tested and calibrated according to the pharmacopeia procedure. In the US, the calibration procedures are defined by the United States Pharmacopeia (USP)

Here are the parameters to be tested and calibrated according to USP:

  • Photometric accuracy
  • Wavelength accuracy
  • Photometric linearity
  • Photometric repeatability
  • Resolution
  • Stray light


Here are the parameters that are tested and calibrated but not required by USP:

  • Photometric noise
  • Photometric drift
  • Wavelength repeatability
  • Baseline flatness


Photometric Accuracy

Photometric accuracy refers to a spectrophotometer’s ability to precisely measure the absorbance of a specimen and return the said absorbance closely as possible to the actual value. Photometric accuracy is tested and calibrated by measuring liquid or solid filters of a particular absorbance and concentration values and comparing the measured absorbance with a reference standard value. For instance, a certain amount of potassium dichromate solution can be measured using an ultraviolet range and compared with a neutral density filter to determine if it falls within the acceptable level of the reference material.

Wavelength Accuracy

Wavelength accuracy assesses whether a spectrophotometer can precisely reproduce wavelengths. The wavelength accuracy-test determines the presence of misalignments or shifts in a wavelength axis. A wavelength calibration material should produce well-defined and narrow peaks. Holmium oxide solution is usually used to calibrate wavelength accuracy. The acceptable calibration standard depends on the wavelength range and the material used.

Photometric Linearity

Photometric linearity refers to the linearity of a function of increasing concentration of measured values such as absorbance. When performing the tests and calibration for photometric linearity, the same procedure as photometric accuracy is used except that different filters are used according to the accepted criteria when determining the linearity of three concentrations.

Photometric Repeatability

Photometric repeatability is the capacity or capability to return absorbance from measurements taken multiple times in a repeatable and reliable manner. When conducting photometric repeatability tests and calibration, the same reference materials as photometric accuracy are used only. In this regard, the filters are measured ten times before calculating the standard deviation of the calculated measurements to establish the extent of repeatability.


Resolution refers to the resolving power and the capability of a UV spectrophotometer to resolve the structures within a given spectrum. When testing and calibrating spectrophotometer resolution, a solution of n-Hexane and Toluene is used. The absorption rate of a well-resolved peak at minimum and maximum are assessed. According to the USP testing and calibration standards, the ratio of the given minimum and maximum UV absorbance at a specific wavelength must be more than 1.3 for sufficient resolution to be determined. Our laboratory at Biotechnical Services Inc. has the latest technology for performing your spectrophotometer calibration in San Diego and the greater California region.

Stray Light

Stray light is not part of the test, analysis, or calibration. It is just a light that manages to reach the detector causing biases to the wavelength under study. Stray light does not originate from the specimen being measured. Typically, the stray light alters the sample results, causing a systematic error during the analysis. When testing and calibrating the stray light, a filter made of a solution of potassium chloride under a specified wavelength is used to determine the filter ratio of the solution. The spectrophotometer is calibrated when the stray light exceeds the acceptable criteria.

Automated Verification

The tests mentioned above and calibration can be conducted either automatically or manually. However, manual methods have a higher risk of minimizing calibration precision, are prone to imminent error, and are time-consuming.

Advantages of Automated Verification

  • Faster traceable documentation of results and validation
  • Avoidance of data errors and repetition
  • It is FDA compliant method with high integrity standards
  • Increases productivity and security



An accurate and excellent spectrophotometer is vital for data measurement precision and compliance purposes. For accurate analysis and quality control of your processes, you should keep your spectrophotometer as accurate as possible. At Biotechnical Services Inc., we offer high integrity spectrophotometer calibration in San Diego with complete documentation and onsite installation and qualification for reliable and compliant laboratory operations.