Directly after its introduction in 1989, UniQuant™ has given a boost to the analytical power of sequential X-Ray Fluorescence (XRF) spectrometers. In 2008, UniQuant was introduced on an energy dispersive instrument, the Quant'X.

Notably, XRF spectrometry became widely accepted for the analysis of polymers, oil, catalysts, environmental and forensic samples. In many research laboratories, UniQuant made the XRF spectrometer a more versatile tool.

There are now well over 3000 XRF laboratories using UniQuant.

Position of UniQuant in Materials Analysis

What is UniQuant

UniQuant represents a total method (all in one) in XRF analysis, and is a commercially available Product. UniQuant is for standardless semi-quantitative to quantitative XRF analysis using the intensities measured by a sequential X-ray spectrometer or an energy dispersive X-ray spectrometer.

As its name suggests, it Unifies all types of samples into one and the same analytical program and it is Unique in that respect. UniQuant is highly effective for analysing samples for which no standards are available.

Sample preparation is usually minimal or not required at all. Samples may be of very different natures, sizes and shapes. Elements from Be up to Am, (or their oxide compounds) are analysed in samples like a piece of glass, a screw, metal drillings, lubricating oil, loose fly ash powder, polymers, phosphoric acid, thin layers on a substrate, soil, paint, the year rings of trees and in general those samples for which no standards are available.

The reporting is in weight% along with an estimated error for each element.

In general terms, UniQuant is used to provide:

  a quantitative analysis if no standards are available.

  a quantitative analysis with highest accuracy if standards are available.
   About 50% of the current UniQuant   users (about 500) only use UniQuant and do
   not use conventional XRF analysis (calibration by regression). Part of them had
   little choice because no standards are available (Waste materials, Polymers). But
   there is also a tendency by many users to replace the conventional method by
   UniQuant using standards to firm it up for ‘families’of samples.

  determination of the % Sulphur present as Sulphide (reported as %S) and
   the % Sulphur present as Sulphate (reported as %Sx). For WD only.

  determination of the % Phosphor present as Phosphide (reported as %P) and
   the % Phosphor present as Phosphate (reported as %Px). For WD only

  an analysis of small and/or odd shaped samples.

  an analysis of a thin composite layer, along with the mass / area.
   The layer may be on a substrate containing   some elements that are also in the layer.
   Or, the layer may be on a ‘neutral’ substrate, like with dust on a filter.

  the determination of the masses of layers in a multi-layer structure, usually on a substrate.

  screening samples and detection of unexpected elements.
   UniQuant supports 79 elements.
   Contrary to the general belief,Wavelength Dispersive XRF spectrometry +
   UniQuant is much faster than Energy Dispersive XRF spectrometry. The intensities
   per analytical line are two orders of magnitude higher with WD-XRF which also
   has far less problems with spectral interferences.

  a fast pre-analysis of totally unknown samples, prior to decide on further analyses
   
  a chemical analysis to support phase analysis by X-ray diffraction.

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Major Features

Elements Analysed

The following table shows 79 elements which may be analysed by UniQuant.
Colored : Analysed Elements (except H and Li, which may occur as absorbants)
Grey : Not known by UniQuant
Argon is included because it may be found in materials made under an Argon atmosphere.

Nature of samples

The unknown samples may take a great variety of physical forms such as:
- a solid disk of metal or a synthetic material
- a multi-element mono-layer on a substrate
- a mono-element multi-layer on a substrate
- a small piece of solid sample placed on a supporting film
- a pressed powder that may include a binder
- a very small amount of powder on a supporting film
- a solid solution of a mineral (a glass bead)
- a liquid sample from a small drop to a full cup
- a filter aerosol sample

Analysis time

A totally unknown sample may be measured by the full set of prescribed measuring channels (about 115 spectral positions) including one or two lines of up to 79 elements (Be to Am). The spectrometer time then is about 20 minutes.

Usually, the ultra-light elements are only included in special applications.
Without the ultra-light elements, the spectrometer time is about 12 minutes.

Samples belonging to a known family may be measured by a smaller sub set of the full set of measuring channels. For example, the analysis of routine waste disposal samples may be limited to say 55 measuring channels with extra long measuring times for relevant traces. The spectrometer time can then be as low as 5 minutes.

UniQuant is intended to cover the widest possible concentration ranges while using one single set of calibration data. Here we are not thinking about a wide range of alloys or of oxide samples.The range that we mean includes samples like oils, polymers, beads, thin layers and all types of alloys! Errors are smallest for thick full-area homogeneous samples and are quite acceptable for less favorable physical conditions.

For specific applications, where very high accuracy is required, UniQuant may use specially calibrated data sets, for example one for Alloys and one for Beads or Glass. Then international or own standards are used to firm up the calibration. This way of working may lead to the same high accuracy as with conventional analysis using regression analysis of standards. Although using specialised data sets has not been the primary philosophy behind UniQuant, its application allows replacing conventional methods by the UniQuant method with far less specialised analytical programs. Several UniQuant users have indeed done so.

Trace Analysis

Reliability
We here introduce ‘Reliability’. An analysis is not Reliable if once and again one or more concentrations are completely out of range. We have seen this happening with semi-quantitative methods (based on scanning). In one such case, 23 %Fe was calculated whilst in fact there was less then 100 ppm Fe in the sample.
The sample contained a high % of Lead and the 2nd order of one of the Pb lines strongly overlapped FeKa. The program then cleverly diverted to FeKb which however was not well calibrated by the standards in the ‘library’. Hence, the gross error for Fe resulted. UniQuant can hardly make such enormous errors. UniQuant gives reliable (plausible) results.

Precision
Precision (reproducibility) of the analysis of a given sample specimen depends only on counting statistics. For each analysed element, UniQuant reports the Standard Deviation (Sigma) in ppm.

For large (full area) samples which are not or not highly diluted, the Sigma’s are surprisingly small. For example 1 or 2 ppm for measuring times of 4 or 10 seconds per analytical line. The Sigma is smallest with lighter matrix samples, for higher atomic numbers and with longer measuring times.

Trace elements (with Z>20) in heavier matrices can be well determined from 20 ppm onward. For light matrix samples like polymers, this value is 5 ppm or even lower accuracy.The accuracy for traces is depending on the quality of the corrections made for:

- background	well done by UniQuant.
- spectrometer’s spectral impurities	well done by UniQuant.
- spectral line overlaps	uniquely solved by UniQuant. Very important!
- matrix effects	solved by FP (Fundamental Parameters)
- physical effects	UniQuant has special ways to compensate for certain physical effects.




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Thin Layer Samples

Mono-layer Samples
UniQuant can calculate the sample mass along with its associated standard deviation. At the same time the composition of the layer is calculated. If the layer is on a substrate with elements that are also in the layer, UniQuant can take their effect into account.
Multi-layer Samples UniQuant may calculate the masses of the layers in a multi-layer structure.

Interactivity

UniQuant has been designed for a maximum of interactivity. A pre-condition is speed of entering data and speed of calculation. The user interface has been designed for an absolute minimum of key strokes or mouse operations.The need for fast interactivity is illustrated by the following example:

A totally unknown powder sample is evaluated by UniQuant in a first calculation (5 seconds) for which the analyst assumes that a mineral sample consists of oxides. The results however may show a very high content of Sulphur. The analyst concludes that the sample is a Sulphide ore. Elements like Pb, Zn, Fe, Mo are as sulphide whilst elements like Si and Al occur as oxides. The original assumption would assume most
elements to be as oxides, even Sulphur. The sum of concentrations would end up at a level higher then 100%. Now, the analyst just changes Oxides to Sulphides in the General Data and starts a second calculation. All this is a matter of a few seconds only.

Batch Modes

In order to short-cut a lot of work at the PC, Batch Modes are provided. These may be used for evaluation of calibration (set-up) samples as well as for evaluating a suite of unknown samples. Samples are ‘tagged’ in a directory and the ‘process’ is started.

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