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).
Figure 1: Elements of the periodic table which can be analyzed using ICP-AES (Charles & Ferdeen, 1997).
Figure 2: Steps in analysis of samples by ICP-AES (Agilent technologies, 1999).
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.
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).
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).
Some of the applications of this technique have been listed in the following table (Agilent technologies, 1999):
|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.|
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.
A couple of years ago, I had my worst experience with Styrofoam. I was travelling from Islamabad to Karachi (its a 24 hour journey by bus) with my parents. We bought some rice from a famous restaurant at I guess 9:00 am. That particular restaurant opened at 9:00 am. Well, we had no idea. We chose to take our food in Styrofoam boxes for convenience. When I opened the box at noon, I observed that they just heated the already packed food from yesterday. Till night, the Styrofoam became moist and started breaking from every where. It was a very uncomfortable situation. I could also spot pieces of foam in the rice. Well, we did ate that but the thought of taking in toxic plastic still haunts me!!
Like always, there is a very good and informative info-graphic at the end of this post…
Why avoid Styrofoam?
Styrofoam is the trade name of polystyrene foam. In United States, polystyrene is the 6th largest source of hazardous waste. Polystyrene is composed of styrene and benzene, both of which are known human carcinogens. Therefore, heating food in Styrofoam must be strictly avoided as it leads to release of harmful chemicals into food.
Moreover, the process of generation of this polymer is energy intensive.
How can I reduce my consumption of styrofoam?
We can take some measures at personal level to avoid the use of these toxic polymers, which include:
1- Avoid buying meat products and other products using Styrofoam. For instance, meat can be bought directly from butcher.
2- Bringing your own containers for takeout food from restaurants (something we know but never do!).
3- Using reusable dishes instead of disposable Styrofoam cups, plates, and boxes.
How can I reuse waste Styrofoam?
There are several ways through which we can reuse Styrofoam for home items. Some of these methods include using it as filler for beanbag chairs and pillows, making models, packaging, making a palette for paints, and insulation.
Anti-fouling paints are used to prevent the growth of living organisms on the ship hulls. Growth of living organisms on ship hulls typically generating resistance in ship movement and subsequently utilization of more fuel.
Assalam, hi, anneyonhaseyo, konnichiwa and sawatdikap! So..Umm..I don’t know where to begin…I have so much to say and I don’t know if anybody cares about it or not…but I thought I should offer my explanation for not posting anything in a while by writing a post for the coming year. So, first of all happy new year! May God help you in achieving all your rightful aims and wishes!
Here are few of the things I did last year;
- I graduated (well almost since we didn’t have a graduation ceremony)
- Maybe I am sharing this for the first time but I am competing for a gold medal in bachelors (though I cant say something for sure because my competitor and I have same CGPA I think…She is a very good friend of mine and is also a blogger @meena114)
- I actually prepared and presented a dissertation. Working in lab was amazing. Love chemistry (I also follow chemistry lovers on facebook :-D) The routine was quite hectic during the thesis!
- I did not read any novels.
- I made many new friends.
- I learned how to party in a chemistry lab :-D.
- I learned that sealing the lid of soft drink bottles with parafilm can help keeping the drink fresh :-D. One of my most favorite things in lab.
- In this year, I shifted from American and Indian shows to Thai dramas and then to Korean dramas and other thingies. I love Korean culture because its a little bit similar to Pakistani culture.
- I tried to learn some Thai and Korean. Hmm, I think I can do some basic stuff.
- I have also started reading webtoons!
- I cooked for others and became head home cleaner :-P.
- Ah..This list wont end!
- Oh, how can I forget I took admission in the same university as before for doing M. Phil in Environmental Sciences (chemistry)
- and that for the first I found a world famous celebrity with the same birth day/month/year as mine. As you may have guessed I was super excited and the testing for similar personality began!I was also going to mention the goals I have for 2018, but I think the readers might get bored.
So, that’s all. Thank you, xiexie, khop kun kha and gumabsabneida for reading this post!
P.S: Reading subtitles has ruined my english. These days I say things like “Don’t remember. Long ago.” Huh! Also, I feel like a kid today. I know its a very childish post.
Serve with french fries or pasta and enjoy!!
I was preparing for Atmospheric Chemistry’s exam when this question popped up in my mind. So, first of all, I hope you all know about our beloved Carbon Cycle. You should also know that carbon dioxide is a major greenhouse gas and recently its concentration in atmosphere has increased to 400ppm mainly due to human activities.
So, now comes the question how carbon cycle acts as a thermostat for our Earth? It does so mainly by positive and negative feedback mechanisms. In positive feedback, the processes that are occurring in nature are enhanced (for example, upon increase in temperature these mechanisms support warming), while in negative feedback mechanisms, the processes are opposed (for example, upon increase in temperature these mechanisms support cooling). Maybe this figure will explain them better than I can!!
Now let’s observe how climate change affects carbon cycle and its feedback mechanisms.
- Terrestrial Environment
In some areas where temperature increases due to climate change, there will be an increase in respiration by plants and this will reduce carbon storage in plants, releasing more carbon dioxide to the atmosphere (positive feedback). Though, in other areas where decrease in temperature occurs, the period of photosynthesis will increase as respiration will be slow, thus carbon will be stored from atmosphere (negative feedback). More carbon dioxide concentrations also support higher rate of photosynthesis.
Similarly, soil stores more carbon at colder temperature and high precipitation as rate of decomposition is reduced.
This table clearly represents how various factors effect feedback mechanisms.
2. Ocean Feedbacks
CO2 is far more soluble in colder water than in warmer water, thus warmer sea surface temperatures will affect the oceans’ ability to dissolve CO2 and their carbon chemistry. A warmer ocean might cause dissolved organic carbon to decompose faster and convert to CO2, reducing the amount of atmospheric CO2 that can be absorbed by the oceans (a positive feedback). Warming might also cause a decrease in the extent of sea ice, which could increase plankton and other marine growth in high-latitude regions. This would result in a greater uptake of atmospheric CO2, thereby acting as a negative feedback (Read more here).
Evidence exists that the relationship between climate change and carbon cycle will be very important in the future for determining emissions and carbon dioxide concentrations in the atmosphere.
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.
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.