How can refractive indexes be dealt with for specific sample types?

Document ID

Document ID TE7965

Version

Version 3.0

Status

Status Published

Published Date

Published Date 05/21/2019
Question
How can refractive indexes be dealt with for specific sample types?
Summary
Dealing with refractive indexes for samples
Answer
To deal with refractive indexes, it depends on the type of sample being run and whether or not all samples are of the same matrix.

When working with a specific matrix it may be necessary to match carrier to the sample matrix. Lachat has many methods developed for specific matrixes. See the full Lachat methods list to see if a method already exists for the matrix you intend to run.

In some cases it may not be possible to match the matrix with the carrier. For example, if sea water is being tested at various salinities for each sample, it may not be possible to match the carrier to all samples. In these cases, there are a couple of considerations that can make it possible to analyze these samples:
  • Omnion software allows the analyst to use brackish integration. Brackish integration allows us to use an additional integration window (box within the box) to integrate the portion of the sample peak which is not influenced (or is less influenced) by the presence of a refractive index. Lachat offers brackish methods for using this integration. To set the integration windows, spikes must be performed on a sample with a refractive index. The brackish integration must then be adjusted so as to get the best spike recovery results to determine the correct integration setting.
  • If samples contain a high but variable salinity, consider using artificial sea water as a carrier solution. Even if all samples cannot be matched, the refractive index can be minimized so that it can be ignored or make it easier to apply brackish integration.

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