August 4, 2020

What Is Blank Correction and Why Is It Important?

You may have seen our recommendation for all standards under 1 ppm to be blank corrected in your quotes or order confirmations. What does blank correction mean and why is it important for your analysis?

Accurate measurements of analytes at low to very low concentrations require accurate corrections for solvent blanks or other sources of background. Many of the solvents or matrices that are used to prepare standards have a very low concentration of analyte, i.e. such as sulfur or chlorine.

We refer to the starting material as having impurities as it is virtually impossible to provide blank material without some analytes or elements present. If the starting impurities are greater than a requested concentration, ASI won't be able to provide the standard for XRF analysis even with a blank correction. Check out our previous post on how impurities can vary from lot to lot. 

When a request comes through for a certified reference material that is “ultra-low”, i.e. below 1 ppm, there is a risk of going below the detection limit and limit of quantification of the instrument. A blank solvent is used to minimize this error. 

Impurities of the blank are not counted (assumed to be 0 ppb or ppm) into the calculation of the check standard/standards. The analyte is added to the “solvent blank” when preparing the standards. When the analysis is conducted, a correction value must be used to subtract the effect of the blank on the standards. This reduces the impact of the limit of detection and limit of quantification of the instrument on the results of the calibration as well as ensures the linearity and accuracy of the calibration curve. This subtraction is the blank correction!

If blank correction is not applied to a standard or set of calibration standards that are blank corrected, all the measured values will be off by the amount of analyte that is in the “solvent blank” and will throw off the linearity and accuracy.

If a calibration set is blank corrected, then the check standard for the set must also be blank corrected to ensure they are in agreement with each other and to obtain accurate results.

Blank correction is important for accurate analysis of reference materials, and we strongly recommend it for calibration standards and check standards below 1 ppm. It is good practice to include a blank concentration in a calibration set.

As always, you can reach us at if you have any questions.

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