Column: Chemometrics in Spectroscopy

More About CLS, Part 2: Spectral Results (Not Needing Constituent Values) and CLS

February 01, 2020

A previous analysis of data is compared to the results achieved using classical least squares and principal component analysis. What did we learn?

Using Reference Materials, Part II: Photometric Standards

October 01, 2019

Alignment of the instrument y-axis is a critical step for quantitative and qualitative measurements using spectroscopy. Here, we explain in detail how to use photometric standards for ultraviolet, visible, near infrared, infrared, and Raman spectroscopy.

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July 28, 2019

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More About CLS, Part 1: Expanding the Concept

June 01, 2019

A newly discovered effect can introduce large errors in many multivariate spectroscopic calibration results. The CLS algorithm can be used to explain this effect. Having found this new effect that can introduce large errors in calibration results, an investigation of the effects of this phenomenon to calibrations using principal component regression (PCR) and partial least squares (PLS) is examined.

Using Reference Materials, Part I: Standards for Aligning the X-Axis

February 01, 2019

The use of reference materials to align or test the wavelength–wavenumber axis for optical spectroscopy is essential for quantitative and qualitative methods. This article provides details for using reference materials with ultraviolet, visible, near-infrared, infrared, and Raman spectroscopy methods.

Outliers, Part III: Dealing with Outliers

October 01, 2018

What are the steps to take once an outlier is discovered? There are several options.

Calibration Transfer Chemometrics, Part II: A Review of the Subject

June 01, 2018

Calibration transfer involves several strategies and mathematical techniques for applying a single calibration database consisting of samples, reference data, and calibration equations to two or more instruments. In this installment, we review the chemometric and tactical strategies used for the calibration transfer process.

Outliers, Part II: Pitfalls in Detecting Outliers

February 01, 2018

How can you detect the presence of an outlier when it is mixed with multiple other, similar, samples?

Calibration Transfer Chemometrics, Part I: Review of the Subject

October 01, 2017

Calibration transfer involves multiple strategies and mathematical techniques for applying a single calibration database to two or more instruments. Here, we explain the methods to modify the spectra or regression vectors to correct differences between instruments.

Outliers, Part I: What Are Outliers?

June 01, 2017

Outliers are fundamentally a very fuzzy notion. Here, we try to clear up what outliers are and how they affect your data.