Brief introduction to Inductively coupled plasma- Atomic emission spectrometry (ICP-AES/ICP-OES)

Sorry, I know this post is all about science, but I thought it could help some people who don’t know about this analytical technique (like me).

Inductively coupled plasma- Atomic emission spectrometry (ICP-AES)

(By Zoobia Nadeem)

ICP-AES is a type of emission spectrometry designed for determination of the amount (concentration) of a test element in a sample. This characterization technique involves the atomization and excitation of the test element by inductively coupled plasma (ICP) and determination of amount (concentration) of test element from the intensity of atomic emission spectral line.

ICP-AES can detect more than 70 elements and offers several advantages over other techniques such as Atomic Absorption Spectroscopy. Some of these advantages include:

  • Possibility of rapid and simultaneous multi-elemental analysis.
  • Atomic emission source (ICP) is relatively free of chemical interference owing to its high temperature (6000 to 10,000 K).
  • Low detection limits.
  • Good accuracy and precisions.
  • Elements that are difficult to be determined through AAS, such as Boron and Vanadium, can be measured (Charles & Ferdeen, 1997).1.png

Figure 1: Elements of the periodic table which can be analyzed using ICP-AES (Charles & Ferdeen, 1997).

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Figure 2: Steps in analysis of samples by ICP-AES (Agilent technologies, 1999).

1.1         Instrumentation

An ICP-AES instrument typically involves the following components:

1.1.1        Sample introduction system

Test sample is pumped into a nebulizer, where it is converted into a fine aerosol spray by a stream of argon (Ar) gas. This aerosol enters the plasma through inner tube of the plasma torch.

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Figure 3: Components of ICP-AES (Agilent technologies, 1999).

1.1.2        The ICP discharge system

Following steps are involved in the generation of ICP:

  • Ar gas is directed through a torch comprising three concentric tubes made of quartz or any other appropriate material. The upper portion of this torch is surrounded by a copper coil (load coil) which is connected to a radiofrequency generator.
  • When RF power (700 to 1500 watts) is applied to the load coil, RF electric and magnetic fields are set up in the upper region of the torch.
  • An electric charge is applied to the Ar gas circulating through the torch, which leads to the stripping of electrons from Ar atoms.
  • The stripped electrons are caught up in and accelerated by magnetic field. The increase of energy of electrons by the use of coil in this manner is known as inductive coupling. The high energy electrons then collide with other Ar atoms and strip off more electrons.
  • The process continuous in a chain reaction to generate an inductively coupled plasma consisting of electrons, Ar ions and Ar atoms. The functions of high temperature ICP discharge involve desolvation (removal of solvent to generate microscopic particles), vaporization (decomposition of particles into stream of individual molecules), atomization (disassociation into atoms), excitation and ionization of test sample (Charles & Ferdeen, 1997).

1.1.3        Optical Spectrometer

As mentioned above, in ICP-AES, light emitted by the excited atoms and ions in the plasma is measured to determine the composition of test sample. On the basis of mode of operation, ICP-AES can be divided into two types, which are simultaneous and sequential instruments. Simultaneous instruments detect several spectral lines simultaneously using a polychromater with a detector for each spectral lines. Sequential instruments are relatively more suited for laboratories as they allow the freedom of selection of a set of analytical wavelengths using some monochromater (Agilent technologies, 1999).

Both these types of ICP-AES instruments use focusing optics, a grating spectrometer and a detector. Focusing optics (lenses or mirrors) collect and focus the light emitted from the plasma onto the entrance slit of spectrometer. A grating spectrometer then generates a spectrum of the focused light so that the intensity of light can be measured at very precisely defined wavelengths. Specific wavelengths are then detected using photo-sensitive detectors such as photo-multiplier tube (PMT), charge-induction device (CID), or charge-coupled device (CCD) (Charles & Ferdeen, 1997).

1.1.4        Computers

Computers are used to perform several functions such as background correction, preparation of calibration graphs, calculation and analysis of results. These are also used to access databases and control the instrument (Agilent technologies, 1999).

1.2         Applications

Some of the applications of this technique have been listed in the following table (Agilent technologies, 1999):

Field Applications
Agriculture, food and beverages Determination of micronutrient and toxic elements in agricultural

samples such as soil, plant tissue, grains, forages, animal feeds,

fertilizers, milk, etc.

Biology Determination of essential elements and non-essential elements in human urine, blood, soft and hard tissues, animal samples.
Geology Determination of minerals and radioactive elements in rocks, minerals, ores, concentrates, coal, fly ash, etc.
Water For the monitoring and analysis of surface water, freshwater, drinking water, etc.
Organics Determination of metals in cooking oils, antifreeze, pesticides, etc.

2           References

Charles, B., & Fredeen, K. J. (1997). Concepts, instrumentation and techniques in inductively

coupled plasma optical emission spectrometry. Shelton, CT: Perkin Elmer Corporation.

Agilent technologies. (1999). Liberty II: Analytical methods book. Victoria, VIC: Varian

Australia Private Limited.

 

 

 

 

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Increasing Efficiency of Solar Cells by Mimicking Cabbage White Butterflies

A team of researchers from the University of Exeter has shown that the efficiency of solar panels can be increased by nearly 50% by mimicking the v-shaped posture adopted by Cabbage White butterflies to heat up their flight muscles before take off.

08-sn-univ-butterflies-fig1                              butterfly-technique

The angle at which these butterflies hold their wing is approximately 17 degrees. This is the reason due to which these butterflies take flight before other butterflies on cloudy days.

The research team analyzed and tried to replicate the butterfly wing structure to create a new lightweight reflective material with the capability to produce solar energy. The process produces not only lighter, but also more efficient panels.

 

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Test: How Well Do You Know Your Environment?

Hi. I am thinking about starting a daily quiz on environment. I hope you enjoy it and that it helps us know more about our environment! Please answer my question by typing in the correct option in the comments section. The winner’s name will be shared in the next quiz along with the correct option.

Which element causes the minamata disease?

a) Arsenic

b) Mercury

c) Cadmium

d) Uranium

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Nanoparticle- What???

What comes to your mind when you hear the term ‘nanoparticles’?

Logical answer would be ‘particles with size of 10^-9 m’.

And it’s quite right.

A nanoparticle (or nanopowder or nanocluster or nanocrystal) is a microscopic particle with at least one dimension less than 100 nm.

Hence, in general the size of a nanoparticle ranges between 1 and 100 nm. Metallic nanoparticles have a different physical and chemical properties from bulk materials (higher surface areas, specific optical properties, lower melting points, etc.), properties that might prove attractive in various applications.

Nanoparticles Figure_2

applications-nanoparticles

For example, the bending of bulk copper (wire, ribbon, etc.) occurs with movement of copper atoms/clusters at about the 50 nm scale. Copper nanoparticles smaller than 50 nm are considered super hard materials that do not exhibit the same malleability and ductility as bulk copper.

Nanoparticles often have unexpected visible properties. For example, gold nanoparticles appear dark red to black in solution.

gold-nano-rods-2_crop

Nanoparticles have high surface to volume ratio. This provides a tremendous driving force for diffusion, especially at elevated temperatures.

Air pollution                                                                                               

Air pollution can be remediated using nanotechnology in several ways. One is through the use of nano-catalysts with increased surface area for gaseous reactions. Catalysts work by speeding up chemical reactions that transform harmful vapors from cars and industrial plants into harmless gases. Catalysts currently in use include a nanofiber catalyst made of manganese oxide that removes volatile organic compounds from industrial smokestacks.

Another approach uses nanostructured membranes that have pores small enough to separate methane or carbon dioxide from exhaust.

The substances filtered out still presented a problem for disposal, as removing waste from the air only to return it to the ground leaves no net benefits.

Water Pollution
As with air pollution, harmful pollutants in water can be converted into harmless chemicals through chemical reactions. Trichloroethene, a dangerous pollutant commonly found in industrial waste water, can be catalyzed and treated by nanoparticles.

Also widely used in separation, purification, and decontamination processes are ion exchange resins, which are organic polymer substrate with nano-sized pores on the surface where ions are trapped and exchanged for other ions. Ion exchange resins are mostly used for water softening and water purification. In water, poisonous elements like heavy metals are replaced by sodium or potassium. However, ion exchange resins are easily damaged or contaminated by iron, organic matter, bacteria, and chlorine.

Oil spills

Recent developments of nano-wires made of potassium manganese oxide can clean up oil and other organic pollutants while making oil recovery possible. These nanowires form a mesh that absorbs up to twenty times its weight in hydrophobic liquids while rejecting water with its water repelling coating. Since the potassium manganese oxide is very stable even at high temperatures, the oil can be boiled off the nanowires and both the oil and the nanowires can then be reused.

Climate Change. It Ain’t a Natural Phenomena. It’s Our Fault and it’s Our Problem.

Yesterday, we were shown a documentary film ‘An Inconvenient Truth’ in our Environmental Management class. I loved it. The whole presentation, facts and figures, the graphics, and technology, everything was great and inspiring. Sadly, we couldn’t see the complete documentary due to shortage of time :-(.

An Inconvenient Truth for Kidz-thumb

A graph was presented by Al Gore, which conveyed astonishing facts about carbon dioxide emissions (they were astonishing to me atleast.) Al Gore, through certain facts and figures, proved that climate change is not a natural phenomena, its anthropogenic.24_g-co2-l

So we all have to be responsible citizens and individuals. We cannot grow boundaries on climate change problem. It is our common tragedy and we have to face it together.

You can visit these very interactive website to know what you can do to stop climate change. Just click on the picture.

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So, I thought I should search as to how can we contribute in reducing climate change. Here are a few guidelines (Canada’s Action on Climate Change, 2012)

  1. Adapt to sustainable transport
    Walk or bike whenever possible. Not only will you reduce your carbon footprint, but your overall level of health will improve and you will save money on parking and gasoline.
  2. Reduce your energy use
    For this, adopt energy-saving habits. Make it a habit to turn off the lights when you leave a room. Also, replace standard light bulbs with energy-efficient compact fluorescent bulbs. Turn off your computer and unplug electronics when they are not in use.
  3. Insulate your home
    Insulate yourself and your home. By properly insulating your home, you can ensure that heat stays in or out depending on the season. You can do this by purchasing windows and window coverings that will block out or keep in warmth, and by sealing any existing cracks. In winter, reduce your thermostat by 2 °C to enjoy energy savings and a cozy sweater. In summer, use fans to circulate air, and set air conditioners to make your home a comfortable temperature. Lowering the temperature on your water heater to between 55 and 60 °C and insulating your pipes also makes a difference.
  4. Cool wash and hang to dry
    These are not just washing instructions on a label anymore, but an equation for energy savings. Wash clothing
  5. Make every drop count
    Conserve water by fixing drips and leaks, and by installing low-flow shower heads and toilets. Challenge yourself to a speed shower. Turn off water while brushing teeth or shaving. Treating and transporting water requires energy, while water conservation results in reduced energy requirements and carbon emissions.in cold water and hang clothing to dry outside, or indoors on a drying rack. Taking these steps will reduce your electricity bill and also prolong the life of clothing by reducing wear on the fabric caused by dryers.
  6. High efficiency appliances
    When replacing appliances, look for high efficiency units. Appliances with ENERGY STAR ratings, an international standard for energy-efficient consumer products, typically utilize a minimum of 20 % less energy. This means savings for you and the environment.
  7. Switch to “green power”
    Research where your power is coming from – wind, water, coal, or solar – and talk to your power provider to determine if a greater percentage could be coming from renewable resources. Encourage power providers to switch to green power and, if possible and/or economically viable, switch to a company offering power from renewable resources.
  8. Recycle
    Make recycling part of your daily routine. Recycle all packaging and consumer goods that you can. Aim to purchase items with minimal and recyclable packaging. For certain items with large amounts of packaging, ask retailers if they can recycle or re-use it. For electronics, facilities now exist that can dispose of electronics in an environmentally responsible manner.
  9. Repurpose
    Rather than discarding or recycling clothing and household goods, give them a chance at a second life. Gently used clothing can be donated to charity or exchanged with friends and family. Old T-shirts can be repurposed into rags for cleaning. Household goods can be donated to charity or sold at a garage sale. Through repurposing, the amount of waste being sent to landfill sites is reduced, there is no need to use energy for recycling, and others can benefit from your used items.
  10. Plants, our new best friend
    When gardening, select plants that are well suited to your climate and require minimal watering and attention. Better yet, plant a tree, and it will provide shade and soak up carbon from the atmosphere.

Health Benefits of Lemon

I never knew that our bitter lemon fruit has such a long list health benefits. I used to like lemons before (I love the bitter taste of them), but after acknowledging the benefits of lemons, I like them even more.

Lemon has the power to control and cure a wide range of health problems. Not only it can help you to deal with health issues, but also it can amplify your beauty. The following pictures illustrate most of the health benefits of lemon (Citrus × limon).

Health benefits of lemon

Health benefits of lemon

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