September 11, 2019

A Quick Explanation of Lot Impurities and Ultra Low-Level Calibration Standards

I Bought This Before, Why Is the Concentration Different This Time?

ASI Standards is a market leader in customizable certified reference materials and calibration standards. We pride ourselves on being able to formulate and manufacture the exact concentration to meet your needs ... but all companies have limits.

It is impossible to have a true 0 ppm or sulfur-free matrix. Trace sulfur impurities in the starting material matrix are always present. We refer to the lowest concentration we can test as a “blank” rather than a “0” for this very reason.

There are two important points to remember about impurities:

  • Each matrix may have a different impurity for the element in question. Nitrogen and chlorine impurities are typically higher than sulfur impurities in our starting material.
  • Each new starting batch, or lot, of a matrix may have different impurities than the previous lot of the same matrix.

Production Technician Justin finishes bottling the latest lot of SMO10                                                                         Production Technician Justin finishes bottling the latest lot of SMO10.

Both points are important to keep in mind when requesting check and calibration standards to test concentrations in the parts per billion, but the second point cannot be stressed enough.

While we may have been able to offer a sulfur in residual oil blank at 2200 mg/kg 3 months ago, the next residual oil lot we make might have sulfur impurities of 2350 mg/kg. If you requested to duplicate your previous order from three months ago, you would still receive an SRO-Blank-100 but the actual reported sulfur value on the Certificate of Analysis would be different.

Don’t forget, we will always provide the actual value of the blank element(s) being tested on the CoA.

Lower-Level Impurities

Things get trickier with lower-level impurities. If our starting material for sulfur in isooctane check standards has natural sulfur impurities of 100 ng/g (parts per billion), we can make a check standard at 200 ng/g. If the next lot of isooctane has natural sulfur impurities of 210 ng/g, we could not offer you the same SIO-0.2-100 at 200 ng/g.

Ask Us About Your Custom Reference Material or Calibration Standard

Clear as oil? We encourage you to email our sales team at with any questions when preparing a purchase order or quotation request from your lab or your customer.

ASI is open and honest with our matrix impurities. We strive to provide you with high quality reference materials that meet your needs. We’re here to help!

Looking Forward,
Geoff – Director of Marketing and Sales

Ready to start?

Latest Posts