Testing water sources is an important step for anybody involved in or affected by the water sector, from government agencies aiming to control waters to protect against environmental and health dangers to homeowners wanting to guarantee their water is safe to drink.
As an industry, we must stay up to date on the latest news, trends and legislation affecting water sources and we must educate customers on how to analyze and treat their water resources properly.
Analytical testing procedures such as colorimetry and spectrophotometer are critical in the water treatment industry.
After all, if you don’t know what’s in the water, you can’t prescribe a correct solution to your consumers and you can’t correctly comply with regulatory rules for pollutant levels and disposal in municipal and industrial settings.
What is the spectrophotometer?
A spectrophotometer is an analytical tool used to determine or confirm a sample’s chemical species, chemical structure, or concentration of substances.
The instrument sends out an energy source that passes through a solution and measures light intensity at various wavelengths.
More light is absorbed when the solution has a high molecular concentration.
Types of spectrophotometers
Based on the application requirements, there are various types of spectrophotometers available.
Spectrophotometers are also classified according to their portability.
In this regard, spectrophotometers can be portable or bench-top.
According to wavelength and application context, spectrophotometers are classified into five types:
Spectrophotometer in visible light
A spectrophotometer measures how much light a sample absorbs or transmits as a function of the wavelength.
The wavelengths measured by visible spectrophotometers are in the visible light range (390 – 700 nm).
Visual spectrophotometry can be used to quantify nucleic acids, study transition metals and visualize organic compounds, among other things.
Many visible spectrophotometer models contain UV and NIR wavelengths that are longer than 390 – 700 nm.
Single-beam and double-beam models are available.
Spectrophotometer for UV-VIS
UV-Vis spectrophotometry is a device for measuring light absorbance across the ultraviolet and visible ranges of the electromagnetic spectrum.
Light can be absorbed, reflected, or transmitted when it strikes matter.
The absorption of UV-Vis radiation results in atomic excitation, which is the transition of molecules from a low-energy ground state to an excited state.
An atom must absorb enough radiation for electrons to move into higher molecular orbits before it can change excitation states.
Shorter band gaps are usually associated with light absorption at shorter wavelengths.
As a result, the energy required for molecules to go through these transitions is electrochemically specific.
Spectrophotometer for infrared light
Infrared (IR) spectrometers determine the wavelength and intensity of infrared light absorption by a sample.
Infrared light has a wavelength range between the visible and microwave portions of the electromagnetic spectrum.
The wavelength of near-infrared light is the same as that of visible light.
On the other hand, Far-infrared light is closest to the microwave range.
Mid-infrared light is powerful enough to raise the energy level of molecular vibrations.
These vibrations, which are caused by changes in the dipole moment of a molecule, occur only at frequencies where the molecule absorbs infrared light.
Infrared spectrometers are commonly used to limit organic and organometallic particles because the wavelengths of infrared absorption zones are characteristic of certain kinds of chemical bonds.
Infrared spectrometers are categorized into two categories.
Fourier transform infrared (FTIR) spectrometers are single-beam instruments that use an interferometer to distribute infrared light across a sample and measure the intensity of the light that is not absorbed by the sample.
A Fourier transform is often used to transform the resulting time-domain digital signal into a frequency-domain digital signal.
Diffusive infrared spectrometers employ visible lasers, grating and charged coupled devices (CCDs) to gather data. The laser acts as a light source, illuminating the sample.
At the same energy as the incoming laser radiation, the majority of the radiation scatters elastically.
A small amount, about one photon in a million (0.00001 percent), diffuser from the sample at a slightly different wavelength than the original wavelength.
Spectrophotometer for fluorescence
Fluorescence spectrophotometry is a technique that studies the interactions of fluorescent probe particles to determine the state of a sample (typically a biological system).
This interaction is tracked by measuring the changes in the optical characteristics of the fluorescent probe.
Fluorescence signal measurement provides a sensitive method of monitoring a fluorophore’s biochemical environment.
Fluorophores are fluorescent polyatomic molecules.
Fluorescence intensity, spectrum, lifetime and polarization have all been measured using instruments.
The apparatus is outfitted with several advanced features that can be used to quantify a wide range of samples.
This can also be used to solve complex biological processes and the mechanism of enzyme inhibition.
This technique can be used to analyze dyes, LEDs, tracers, solar cells and organic electroluminescent materials.
A spectrophotometer for atomic absorption
Atomic absorption spectrophotometry determines the concentration of elements in a liquid sample by absorbing energy from specific wavelengths of light (usually 190 to 900 nm).
Atomic absorption spectrophotometers typically include a flame burner (most commonly a hollow cathode lamp) to atomize the sample, a monochromator and a photon detector.
Some atomic absorption spectrometers are equipped with a tower or fixed lamp socket that can hold multiple lamps (up to eight) to reduce downtime between samples or allow for sequential analysis, relying on the version.
Important considerations when choosing a spectrophotometer /spectrometer
1-Limits of detection
2-The product’s density, shape, or size that you want to measure
3-Wavelength spectrum
4-Analytical operational range
5-Throughput of samples (single sample vs. multi-sample)
6-Data integrity
7-The cost of the instrument and any associated consumable
8-Method options that can be customized and/or pre-configured
9-Measurement period
10-Instrument surface area
Single beam, dual beam and split beam spectrophotometers
A single beam spectrophotometer has one light beam, whereas a double beam spectrophotometer has two light beams, one passing through a reference solution and one passing through the sample.
Because there is only one light path that passes through the sample in single-beam equipment, calibration requires manually going to switch a reference micropipette with the sample separatory funnel.
Double beam spectrophotometers are more efficient and provide more information.
Increasing challenge
The essential principles are simple to follow because they are well-known, yet there have been enormous enhancements in sensitivity, accuracy and precision in analytical instrumentation and other test equipment.
Government rules, as any water treatment dealer serving commercial, municipal, or industrial clients is well aware, have a significant role in the type of tests necessary, the level of accuracy required and the number of tests or testing materials required each month or year.
Water-related crises encourage the government to act quickly to protect citizens from unknown contaminants with new regulations and manufacturers of water tests must respond quickly to ensure consumers can conduct field lab quality testing and verify that water is safe to drink.
While it is generally evident what consumers require – increased precision and tests to ensure compliance with government laws – dealers and manufacturers must also be mindful of the minor details that make their jobs simpler daily.
While the fundamental technologies have not changed, manufacturers have been able to personalize the tests to the demands of their customers while meeting regulatory standards.
References
[1] ANTALYA SCIENTIFIC BLOG TEAM JULY 18, 2013, Using the Spectrophotometer for Analysis, {online} available at https://www.coleparmer.com/blog/2013/07/18/using-the-spectrophotometer-for-analysis/
[2] March 28, 2021, liquid, types of a spectrophotometer, (online) available at https://www.linquip.com/blog/types-of-spectrophotometers/
[3] Lab compare, [on-line], available at https://www.labcompare.com/Spectroscopy/111-Visible-Spectrophotometer/
[4] DeNovix, October 16, 2018, what is UV-Vis spectrophotometry? [Online] available at https://www.denovix.com/blog/what-is-a-uv-vis-spectrophotometer/
[5] Global spec engineering 360 Infrared Spectrometers Information, {Online}, available at https://www.globalspec.com/learnmore/labware_scientific_instruments/spectrometers_analytical_photometers/infrared_spectrometers
[6] PERKIN ELMER, fluorescence Spectrometer, {Online}, available at https://www.lpu.in/cif/fluorescence-spectrophotometer.php
[7] Heather Hall, August 6, 2020, R&D World, what is an atomic absorption spectrometer? (online) available at https://www.rdworldonline.com/what-is-an-atomic-absorption-spectrophotometer/
[8] The modern way to test the water (online) available at: https://www.watertechonline.com/wastewater/article/15544494/the-modern-way-to-test-water
