Curious fact
Nobel chemistry laureate Bruce Merrifield said that the spectrophotometer was “probably the most important instrument ever developed towards the advancement of bioscience.” Do you know that not only a scientific laboratory needs and spectrophotometer but also wine-makers? The spectrophotometer is an important device if you are thinking about equipping your laboratory.
What is a spectrophotometer?
A spectrophotometer is an instrument that measures how much light a substance absorbs. It measures the amount of photons absorbance after it passes through a solution. Every substance will transmit (reflect) and absorb light slightly differently. Like how a fingerprint identifies each individual human, knowing exactly how much red (or green, or blue, etc.) gets absorbed allows us to identify and quantify varied materials. In chemistry, spectrophotometry is the quantitative measurement of transmission properties of a material based on the wave light.
What is a spectrophotometer used for?
A spectrophotometer is used in many areas of science including microbiology, biochemistry, forensics, physics, and medical health. It is used to measure certain ingredients in a drug to make sure it is effective and safe for consumers. You can measure bacterial growth, or diagnose a patient based on how much uric acid is present in their urine. Even non-scientists use spectrophotometers. Wine-makers, for example, use them to determine how much malic acid (reducing sugars) a wine has in it.
When was the Spectrophotometer invented?
There were several models of spectrophotometer before 1940 but they were unable to absorb the ultraviolet properly. Arnold O. Beckman optimizes the model in the company “National Technical Laboratories” They developed many different models (A, B, C). Their model D was widely accepted and it became a canon from 1940 to 1976. Hewlett-Packard created the first commercially available diode-assay spectrophotometer in 1979 known as the HP 8450A, which had a single-beam microprocessor that could scan different wavelength at a time in seconds. Since then spectrophotometry has been consolidated and spectrophotometers are considered to be one of the most innovative instruments.
Types of spectrophotometers
There are two basic types:
– Uv-visible: it uses light over the ultraviolet range and visible range, near-infrared region, as well. This type of spectrophotometers are used to estimate dissolved organic carbo-concentration and Bial’s test for concentration. It is also used in the analysis of DNA, RNA and proteins.
– IR Spectrophotometer: uses an infrared range of electromagnetic radiation spectrum. It is based on the IR light, such as thermal radiation.
– A spectrophotometer has two basic sections: a spectrometer and a photometer. The spectrometer disperses and measures light, while the photometer indicates the intensity of light.
Parts of Spectrophotometer:
The spectrophotometer has six general sections:
- Light sources.
- Condensing lens.
- A monochromator.
- Sample holders.
- Sample detectors.
- Recorder.
The basic functioning starts with light. There are three possible sources: a tungsten lamp (for visible light), a deuterium or hydrogen lamp (for UV light) and LED. The light is reflected using a mirror and passes through the condensing lens, to get to the monochromator. The monochromator produces radiations of a single wavelength and it is based on the refraction or diffraction (using a prism or a grating) and the light is focused on the exit slit to be measured. Readings are recorded to determined different wavelength and absorbance. The detector depends on the photons (UV-visible) or temperature (IR).
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