One critical advantage of full-spectrum analysis is the ability to isolate multiple absorbance curves from the total sample absorbance. This allows us to measure multiple chemical analytes simultaneously with a single analyzer, without using filters or moving parts.
Let's look at the example of measuring H2S and SO2 simultaneously:
We can isolate the curve of H2S from the total sample absorbance spectrum. This is extremely useful for background correction — when lurking components in the process stream have overlapping absorbance with the target analyte. The high-resolution raw data allows for de-convolution of up to 5 chemical species, meaning that the OMA can be optionally configured to monitor additional chemicals.
As illustrated above, each measurement wavelength contributes an equation to a matrix which is continuously solved by the ECLIPSE multi-component algorithm. Due to the resolution of the spectrophotometer, this procedure isolates the absorbance curve of H2S with very high accuracy and is not susceptible to cross-interference. Each equation takes the form:
A'(x+y) = A'x + A'y = e'xbcx + e'ybcy
Where A' is the absorbance at wavelength ', e' is the molar absorptivity coefficient at wavelength ', c is concentration, and b is the path length of the flow cell.
For example, the equation for measuring H2S and SO2 simultaneously at wavelength 225 nm:
A225'(H2S+SO2) = A225'H2S + A225'SO2 = e225'H2SbcH2S + e225'SO2bcSO2
The OMA's ECLIPSE™ Software continuously solves a matrix of these equations sourced from all measurement wavelengths simultaneously to produce an extremely accurate analysis. False positives and cross-interference are eradicated by the statistical averaging effect of using so many confirmation wavelengths.
Photometers that offer multi-component analysis will often use crude techniques like rotating "chopper" filter wheels or a group of line source lamps. These solutions implement moving parts that are prone to malfunction and multiple light sources that all require replacement, while delivering inferior accuracy.
Through the power of rich data, the OMA provides robust multi-species measurement using a solid state design and a single light source.
This article applies to Applied Analytics systems that use the nova II Spectrophotometer.