Air & Water Quality Analysis
Optical spectroscopy techniques are ideal for air and water quality monitoring, where chemical, biological and other parameters can be measured in situ with portable, flexible and robust UV-Vis and NIR spectrometers available from Ocean Optics.
We collaborate with customers on air and water quality monitoring applications by providing spectrometers, accessories, subsystems and complete solutions. Our customers have monitored air quality in areas affected by the Deepwater Horizon oil spill, developed a handheld water quality system to measure the interaction of sunlight with surface water constituents, and detected air pollutants in the exhaust systems of vehicles.
Example Setup: Absorbance of Gases
Absorbance measurements are used to quantify the concentration of solutions and gases (as described in this setup) that absorb light in a media that transmits light. The signal in absorbance units is proportional to the molar absorptivity, pathlength and concentration of the sample (see Beer’s Law).
In a system configured to measure the absorbance of a gas with distinct deep UV absorption characteristics — benzene, for example, which is found in vehicle and other atmospheric emissions — a good place to start is a Maya2000 Pro, which has great response <300 nm. In this setup, the spectrometer uses an H7 grating set for the 200-300 nm wavelength range. Optical bench accessories include a detector collection lens for increased throughput and an optical bench optimized to transmit UV light. With a 5 µm slit, optical resolution of ~0.07 nm (FWHM) is possible. Our D-2000 deuterium light source (discontinued light source) is a good option for UV measurements.
There are many spectrometer-light source combinations available for measuring gas absorbance. For high resolution and faster integration times, the HR2000+ES is a good option. Also, a light source such as the DH-2000-BAL will allow you to illuminate across the UV-NIR range.
A 10-cm pathlength CUV-UV-10 cuvette holder, a CV-Q-10 cylindrical quartz cell and a pair of 455 µm extreme solarization-resistant optical fibers (one fiber illuminates, the other reads signal) comprise the system’s sampling optics. For applications requiring shorter pathlengths or open-air monitoring, use an optical fibers-with-collimating lenses or fibers-with-Gershun tube configuration.
The Maya2000 Pro has response <200 nm, but its configuration for VUV applications requires special attention to the optical bench components specified, as well as purge accessories and the use of free space versus fiber-coupled sampling. Nitrogen purging of the optical bench is necessary to help mitigate water and oxygen absorption that occurs in the vacuum UV. Contact an Application Sales Engineer for assistance.
Gas Absorbance System Components
|Maya2000 Pro||This high-resolution spectrometer is configured for UV absorbance in the sample setup.We use Grating #H7 set for 200-300 nm, with a 5 µm slit as entrance aperture and a detector collection lens for increased sensitivity.|
|D-2000||Deuterium source produces continuous output from ~215-400 nm|
|CUV-UV-10||Cuvette holder for 10-cm pathlength cuvettes|
|CV-Q-100||Cylindrical quartz cell with Teflon stopper; has volume of 28.2 ml|
|QP455-025-XSR-BX||Pair of extreme solarization-resistant patch cord assemblies, 455 µm diameter, 0.25 m length|
|OceanView||Spectrometer operating software|
Chlorophyll analysis provides important information about key parameters of water quality.
Analysis of dissolved organic matter in surface waters can be useful in assessing water quality.
Spectroscopic techniques are ideal for monitoring the interaction of solar radiation with the atmosphere.