UV254nm/SAC - UV Absorption

Definition

UV absoption measurement is used in the testing of water to predict water quality and the amount of dissolved organic carbon. However each chemical species absorbs the UV spectrum differently so the test must be applied carefully. Alternative UV-persulfate TOC analyser methods report true Total Organic Carbon. The Protoc analyser may be configured to rapidly report TOC, TC (Total Carbon) or DOC (Dissolved Organic Carbon) and include MCERTS accreditation.

WTW-trescon uno

Protoc 300 TOC

Methodology

Suspended solids also absorb transmitted light and interfere with the measurement. It is therefore recommended that samples be filtered before analysis. The absorption from a single pre-focussed, pulsed beam passing through a fixed path length can then be continuously reported. The technique is often referred to as reagent-less but cleaning solutions are typically required to maintain and clean optics. Aromatic hydrocarbons and solvents absorb at this frequency.

Limitations Of Test

The results are often arbitrary and need to be carefully interpreted. Only organic chemicals containing a double bond within their structure absorb UV254nm, single bonded chemicals do not. Every organic chemical absorbs different amounts of UV254nm. The technique is not suitable for applications where the contaminant is unknown or variable in its chemical form. The technique can be applied to a known process or to simply alarm but not quantify the presence of some organic chemicals.

Alternative On-line Methodology

Total Organic Carbon - TOC can be used to report the dissolved organic compounds in less than 3 minutes. The test is not compound sensitive and does not suffer interference affects from suspended solids. By determining the TOC or dissolved organic component of a sample stream, a correlation may be set up with other test such as COD and BOD. Peak organic loads may therefore be determined in real-time.

More Information

TOC
On line continuous measurement of Total Organic Carbon for water and waste-water applications

Product Literature

TresCon Uno .pdf (125kb)
On line continuous measurement of Nitrate & SAC (UV) for water and waste-water applications
(single stream)

TresCon Analyser .pdf (125kb)
On line continuous analyser allowing integration of up to 3 measurement modules for water and waste-water applications (multiple stream)

IQ Sensor Net with CarboVis & NicaVis UV- Vis probe for Carbon & Nitrate .pdf (244kb)
In line continual measurement of Nitrate & SAC (UV) for municipal waste-water applications [single and multiple sensor and parameter connection]