Avantes, Inc.

Ecosystems around the world face growing threats from industrialization, growing populations, and increasing urbanization. Not surprisingly, researchers, scientists, and governments are investigating tools for monitoring and preventing these environmental hazards. As all sorts of industries advance in the global marketplace, the need for ecological monitoring technology advances as well. Several spectroscopic measurement techniques are proving to be very effective and versatile for environmental applications. 

	Researchers with the Institute of Solar Energy at the Technical University of Madrid, Spain, trust the Avantes AvaSpec-2048-USB2-UA in their research into the use of high-powered UV LEDs as an excitation source for continuous-use fluorescence testing. LED technology has advanced recently, making these cost effective bulbs an appealing alternative. Traditional incandescent mercury bulbs produce a large amount of heat compared to LEDs, which, combined with their short life, make continuous use impossible.

	These scientists are working to bring real-time, continuous monitoring for hydrocarbon pollution to fruition, using LEDs instead of traditional bulbs.

	The Avantes AvaSpec-ULS2048-USB2 is trusted by researchers at the Solar Energy Research Center and Chemical Engineering Department of the University of Almeria, Spain, in the study of LED light sources for tertiary wastewater treatment processes.

	Tertiary treatment is the final stage of wastewater treatment that removes lingering inorganic compounds and other substances such as nitrogen and phosphorous. This photocatalytic process, employing UVA radiation at 365, 385, and 400 nm, is the photo-Fenton reaction in which radiation causes a rapid reaction between hydrogen peroxide and iron.

	Historically, the photo-Fenton reaction relied on solar radiation as the source of catalytic radiation, but weather conditions and solar cycles make artificial illumination an attractive alternative. Recently, this has been accomplished using mercury lamps, which have a limited lifespan and high cost associated with them. The Spanish researchers are testing the effectiveness of newly available LED light sources for UV radiation with positive results. LED bulbs are less expensive than traditional incandescent bulbs and have a longer life span.

	The world's oceans produce more than half of the oxygen in our atmosphere. Protecting our oceans is vital, and researchers are increasingly using spectroscopy to monitor the health of the world's seas and oceans.

	A group of researchers studying ocean and coastal waterways has been developing models to anticipate intense phytoplankton blooms using irradiance spectroscopy. These harmful blooming events adversely affect ecosystems and human health as well. Using unmanned aerial vehicles fitted with an Avantes dual-channel spectro-radiometry solution covering 360 to 1000 nm, the team was able to derive fine-resolution spectral data and obtain timely information on bloom magnitude, making spectral bloom monitoring during algal bloom season a possibility.

	(4) S. Shang et al., Remote Sens Environ, 


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Several spectroscopic measurement techniques are proving to be very effective and versatile for
environmental applications.

Photonics Applications in Environmental Sciences

Many biomedical research applications exploit the natural fluorescence response of amino acids, the essential building blocks of all proteins. These protein fluorescence responses have been used for everything from pharmaceutical manufacturing to biowarfare defense. 

	Proteins, the complex organic compounds made of chains of amino acids, are the most abundant organic molecule in all living things on Earth. They act as catalysts, regulate physiological processes, and they defend the body against disease.

	Three common amino acids, tryptophan, tyrosine, and albumin, responsible for the majority of inherent fluorescence, have a common structure of hydrogen-based rings. These ring structures, called 

 absorb UV radiation and emit a weak fluorescent signal at varying wavelengths.

Fluorescence in Action: Cancer Fighting Weapons

	Spectroscopy has proven to be invaluable in the fight against cancers. In lung cancer detection, for example, use of autofluorescence bronchoscopy employs a narrow probe inserted through the patient's mouth into the upper bronchial tree.

	Autofluorescence has been shown to be far more sensitive than white light bronchoscopy in the detection of carcinomas or dysplastic lesions, but it also has a high rate of false positives. Researchers at the Department of Respiratory Diseases in Rotterdam, the Netherlands (1), are investigating the use of absorbance/reflection optical spectroscopy to improve specificity without losing sensitivity.

	Using a specially designed probe to fit the 2.8 mm bronchoscope channel, the mucosa tissue was irradiated with a tungsten/halogen broadband light source and a blue laser calibrated to 407 nm. The resulting reflectance and fluorescence emissions were collected via a multichannel Avantes spectrometer installation equivalent to two AvaSpec-ULS2048CL-EVOs in parallel.

	The emission peak for autofluorescence of healthy tissue was 500 nm. Areas that display an abnormal fluorescence profile can be rapidly targeted for additional spectral measurements which can be acquired in <1 s. Diseased tissue displayed drastically lower emission intensity at shorter wavelengths compared to healthy tissues. The combined autofluorescence imaging and optical reflectance spectroscopy significantly improved the positive predictive value compared with autofluorescence alone without sacrificing sensitivity.

	The Avantes Engineering team reproduced a series of experiments (2) conducted with samples of tryptophan, tyrosine, and bovine serum albumin to demonstrate our protein detection capabilities. The team used conventional absorbance techniques with a continuous wave (CW) illumination source (AvaLight-DHc) and an AvaSpec-ULS3648-USB2 spectrometer configured for UV (190–400 nm). Absorption measurements, recorded between 190–320 nm, correlated changes in concentration to changes in absorption. Fluorescence was not measured during this experiment.


	Figure 1: Absorption response of amino acids in 0.25 mg concentration solution.

	The team running this experiment prepared three different concentrations for each of the three sample analytes: 1 mg/mL, 0.5 mg/mL, and 0.25 mg/mL, and took broadband absorption spectra profiles for each.

	The absorption profiles of the amino acids correlated directly with the amino acid concentration in solution. As fluorescence is a function of absorbance and quantum yield, the fluorescence can be estimated and would be expected to also correlate with concentration.

	(1) M.P.L. Bard et al., "Improving the specificity of fluorescence bronchoscopy for the analysis of neoplastic lesions of the bronchial tree by combination with optical spectroscopy," 

	(2) P. Held, "Quantitation of peptides and amino acids with a Synergy(tm) HT using UV fluorescence." B.-T. Instruments, Winooski, VT (2003).


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