Detection of chlorophyll a by Thermo Scientific UV-Visible Analyzer - Database & Sql Blog Articles

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What is chlorophyll?

a?

Chlorophyll is a green pigment found in plants and algae that plays a key role in photosynthesis. It captures light energy, which is then used to convert carbon dioxide and water into glucose and oxygen.

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Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy. Chlorophyll a is the primary pigment involved in this process, and it's often used as an indicator of the health and productivity of aquatic ecosystems.

Chlorophyll a

Pigments are suitable for all plant species, while other chlorophylls (such as

b

,

C1

,

C2

,

d

,

f

) are only found in certain plants, algae, or cyanobacteria. These variations help scientists identify different algal groups in a sample. The Thermo Scientific UV spectrophotometer is widely used for accurate chlorophyll measurement.

Why measure chlorophyll a?

a?

The influx of nutrients like nitrogen and phosphorus into inland or coastal waters can lead to excessive algal growth. This overgrowth can cause oxygen depletion when the algae die and decompose, harming fish, shellfish, and other aquatic life. The image on the right shows the relationship between chlorophyll a and dissolved inorganic nitrogen (DIN).

High levels of chlorophyll a indicate poor water quality and potential eutrophication. Algae blooms can reduce water clarity, impact underwater vegetation, and even create "dead zones" where oxygen levels are too low to support marine life. In extreme cases, toxic algal blooms can harm both wildlife and human health.

In terms of water quality monitoring, chlorophyll a is one of the most reliable indicators of phytoplankton biomass and its potential to cause water turbidity and oxygen depletion.

Chlorophyll a is typically measured in units of Gg/L or μg/L. Levels above 100 μg/L may start affecting aquatic life. Even the cleanest water contains at least 5 μg/L of chlorophyll a. Different water bodies have specific standards based on their intended use, and accurate measurement using tools like the Thermo Scientific UV-Visible Analyzer helps determine the actual condition of the water.

Which users need to measure chlorophyll a?

Water treatment facilities that rely on surface water sources often monitor chlorophyll a to manage algal blooms and prevent issues like clogged filters or increased organic load. Institutions such as the US Army Corps of Engineers, US EPA, NOAA, USGS, and academic research centers regularly conduct these measurements.

How to measure chlorophyll a?

A known volume of water is filtered through a glass fiber filter. The filter is then ground in acetone, and the sample is analyzed. Common methods include spectrophotometry, fluorescence, and high-performance liquid chromatography (HPLC). Spectrophotometry is the most widely used method due to its simplicity and low cost. It typically takes 1–5 minutes per sample and can detect levels as low as 0.08 mg/L.

HPLC allows for more detailed analysis, distinguishing between different types of chlorophyll and accessory pigments, but it is more time-consuming and technically complex. Fluorescence-based methods are ideal for remote or continuous monitoring applications.

Spectrophotometers used for chlorophyll a analysis require narrow spectral bandwidths and multiple wavelengths for accurate readings. For example, wavelengths like 750 nm (for turbidity correction), 664 nm (for chlorophyll a), 647 nm (for chlorophyll b), and 630 nm (for chlorophyll c1 and c2) are commonly used. Some methods also involve acidification to improve accuracy.

Approved methods for measuring chlorophyll a include US EPA 446.0, Standard Methods 10200H, ASTM D3731, DIN 38412-16, and ISO 10260. Equipment like the Thermo Scientific Orion AquaMate 8000 UV-visible water quality analyzer is recommended for reliable, precise results. It offers a wide spectral range (1.8 nm), supports various path lengths (1–10 cm), and ensures accurate and convenient measurements.

Additional accessories and consumables include:

• 1 cm (10 mm) glass cuvette (PN 331709-000)

• Wavelength accuracy verification filters (PN 333150)

• Standard filter recalibration service (PN 333150, PN 701-101600)

• Spectrophotometer performance calibration service (once per year)