Gas Chromatography

by Warangkana Punrattanasin and Christine Spada

Table of contents

  Introduction
    Basic Components of a GC
    Theory of Gas Chromatography
    Example Chromatograms
    EPA 500 Series Methods
    Key to Terminology
    Pop Quiz
    Web Links to Related Topics
    References

Introduction

Gas chromatography (GC) is an analytical technique for separating compounds based primarily on their volatilities. Gas chromatography provides both qualitative and quantitative information for individual compounds present in a sample. Compounds move through a GC column as gases, either because the compounds are normally gases or they can be heated and vaporized into a gaseous state. The compounds partition between a stationary phase, which can be either solid or liquid, and a mobile phase (gas). The differential partitioning into the stationary phase allows the compounds to be separated in time and space.

Figure 1. Gas Chromatographic System

Figure 2. Schematic of a Gas Chromatographic System

Basic Components of a GC

Gas supply or Carrier Gas

Figure 3. Gas Supply

The carrier gas is usually helium, hydrogen, or nitrogen. This serves as the mobile phase that moves the sample through the column. The carrier gas flow can be quantified by either linear velocity, expressed in cm/sec, or volumetric flow rate, expressed in mL/min. The linear velocity is independent of the column diameter while the flow rate is dependent on the column diameter.

---

Injector

Figure 4. Auto Sampler Injection System (Hewlett-Packard Model No. 7673)

The injector is a hollow, heated, glass-lined cylinder where the sample is introduced into the GC. The temperature of the injector is controlled so that all components in the sample will be vaporized. The glass liner is about 4 inches long and 4 mm internal diameter.

---

Column

Figure 5. Capillary GC Column (Supelco ® PAG)

The GC column is the heart of the system. It is coated with a stationary phase which greatly influences the separation of the compounds. The structure of the stationary phase affects the amount of time the compounds take to move through the column. Typical stationary phases are large molecular weight polysiloxane, polyethylene glycol, or polyester polymers of 0.1 to 2.5 micrometer film thickness. Columns are available in many stationary phases sizes. A typical capillary column is 15 to 60 meters in length and 0.25 to 0.32 mm ID. A typical packed column is 6 to 12 feet long and 2.2 mm ID.

---

Oven

Figure 6. GC Oven with column in place

The column is placed in an oven where the temperature can be controlled very accurately over a wide range of temperatures. Typically, GC oven temperatures range from room temperature to 300�C, but cryogenic conditions can be used to operate at temperatures from about -20�C to 20�C.

---

Detector

Figure 7. Electron Capture Detector (ECD) and Flame Ionization Detector (FID) (Shown actual size)

As compounds come off the column, they enter a detector. The compound and detector interact to generate a signal. The size of the signal corresponds to the amount the compound present in the sample. There are several different types of detectors that can be employed, depending on the compounds to be analyzed. These detectors can measure from 10^-15 to 10^-6 gram of a single component.

---

Data Recorder System

Figure 8. Data Recorder

The data recorder plots the signal from the detector over time. This plot is called a chromatogram. The retention time, which is when the component elutes from the GC system, is qualitatively indicative of the type of compound. The data recorder also has an integrator component to calculate the area under the peaks or the height of the peak. The area or height is indicative of the amount of each component.

Theory of Gas Chromatography

Retention Time (t_R)

The retention time is the total time that a compound spends in both the mobile phase and stationary phase. Retention time is generally reported in minutes.

Dead Time (t_m)

The dead time is the time a non-retained compound spends in the mobile phase which is also the amount of time the non-retained compound spends in the column. Dead time is generally reported in minutes.

Adjusted Retention Time (t_R^')

The adjusted retention time is the time a compound spends in the stationary phase. The adjusted retention time is the difference between the dead time and the retention time for a compound.

Capacity Factor (or Partition Ratio) (k^')

The capacity factor is the ratio of the mass of the compound in the stationary phase relative to the mass of the compound in the mobile phase. The capacity factor is a unitless measure of the column's retention of a compound.

Phase Ratio (ß)

The phase ratio relates the column diameter and film thickness of the stationary phase. The phase ratio is unitless and constant for a particular column and represent the volume ratioß.

Distribution Constant (K_D)

The distribution constant is a ratio of the concentration of a compound in the stationary phase relative to the concentration of the compound in the mobile phase. The distribution constant is constant for a certain compound, stationary phase, and column temperature.

Selectivity (or Separation Factor) (alpha)

The selectivity is a ratio of the capacity factors of two peaks. The selectivity is always equal to or greater than one. If the selectivity equals one the two compounds cannot be separated. The higher the selectivity, the more separation between two compounds or peaks.

Linear Velocity (u)

The linear velocity is the speed at which the carrier gas or mobile phase travels through the column. The linear velocity is generally expressed in centimeters per second.

Efficiency

The efficiency is related to the number of compounds that can separated by the column. The efficiency is expressed as the number of theoretical plates (N, unitless) or as the height equivalent to a theoretical plate (HETP, generally in millimeters). The efficiency increases as the height equivalent to a theoretical plate decreases, thus more compounds can be separated by the column. The efficiency increases as the number of theoretical plates increases, thus the column's ability to separate two closely eluting peaks increases.

Example Chromatograms

Sample contains 6 aromatic hydrocarbons dissolved in a solvent (methanol). The compounds' properties are summarized in Table 2.


The compounds were separated on an nonpolar, 95% methyl, 5% phenylpolysiloxane column, 30 m long, 0.25 mm ID, and 0.25 micrometer film thickness. About 1 microliter of the hydrocarbon sample were injected. Approximately 5 nanograms (ng) of each component was injected per 1 microliter. A flame ionization detector (FID) was used.

---

Temperature Programming Effects

Figure 9.

Temperature Program: 50�C (min) - 10�C/min - 100�C

Head Pressure: 12 psi

Split Ratio: 1/50

This chromatogram shows an ideal temperature program for separation of the 6 aromatic compounds on this column. The first peak is the solvent, methanol. The compounds elute in order of increasing boiling point, that is, compounds with higher boiling points are more retained by the stationary phase. Note that para-xylene and meta-xylene cannot be separated on this column; the peak (#5) containing these compounds is broad at the baseline and shows a distinct shoulder.

Figure 10.

Temperature Program: 60�C Isothermal

Head Pressure: 12 psi

Split Ratio: 1/50

This chromatogram shows the effects of an isothermal* temperature program at 60�C. The result is an increase in the retention time of all compounds. The heights of the later eluting peaks are reduced and the peak widths increased because they are more affected by the lower temperature program used. (*isothermal means a constant oven temperature was used throughout the run.)

---

Flow Rate Effects

Figure 11.

Temperature Program: 50�C (1 min) - 10�C/min - 100�C

Head Pressure: 9 psi

Split Ratio: 1/50

This chromatogram shows the effects of a reduced head pressure while using the ideal temperature program. The flow rate was reduced by decreasing the head pressure. The retention time is slightly increased due to the low flow rate used. All of the peak heights were reduced and the peak widths are increased.

Figure 12.

Temperature Program: 50�C (1 min) - 10�C/min - 100�C

Head Pressure: 15 psi

Split Ratio: 1/50

This chromatogram shows the effects of a higher head pressure while using the ideal temperature program. The flow rate was increased by increasing the head pressure. The retention time was reduced and all of the peak heights were increased.

---

Split Ratio Effects

Figure 13.

Temperature Program: 50�C (1 min) - 10�C/min - 100�C

Head Pressure: 12 psi

Split Ratio: 1/25

This chromatogram shows the effects of a low split ratio while using the ideal temperature program. All of the peak heights were increased due to the greater amount of the sample introduced into the column.

Figure 14.

Temperature Program: 50�C (1 min) - 10�C/min - 100�C

Head Pressure: 12 psi

Split Ratio: 1/75

This chromatogram shows the effects of a high split ratio while using the ideal temperature program. All of the peak heights were reduced due to the smaller amount of the sample introduced into the column.

---

Effect of Stationary Phase on Separation of Para-Xylene and Meta-Xylene

Figure 15.

This chromatogram shows the separation of benzene, toluene, para-xylene, meta-xylene and ortho-xylene. The first peak is the solvent, hexane. A polyalkylene glycol fused silica capillary column 30 m long, 0.25 mm ID, and 0.25 micrometer film thickness was used for separation. Para-xylene (peak #4) and meta-xylene (peak #5) can be separated on this column. This illustrates the matching of the stationary phase with the desired compounds to be separated.

EPA 500 Series Methods

• Method 502.1: Volatile haloginated organic compounds in water by purge and trap gas chromatography
• Method 502.2: Volatile organic compounds in water by purge and trap capillary column gas chromatography with photoionization and electrolytic conductivity detectors in series
• Method 503.1: Volatile aromatic and unsaturated organic compounds in water by purge and trap gas chromatography
• Method 504: 1,2-dibromoethane (EDB) and 1,2-dibromo-3-chloropropane (DBCP) in water by microextraction and gas chromatography
• Method 505: Analysis of organohaline pesticides and aroclors in drinking water by microextraction and gas chromatography
• Method 507: Determination of nitrogen-and phosphorus-containing pesticides in water by gas chromatography with a nitrogen-phosphorus detector
• Method 508: Determination of chlorinated pesticides in water by gas chromatography with an electron capture detector
• Method 510.1: Determination of the maximum total trihalomethane potential
• Method 515: Determination of chlorinated herbicides in drinking water
• Method 524.1: Volatile organic compounds in water by purge and trap gas chromatography/ mass spectrometry
• Method 524.2: Volatile organic compounds in water by purge and trap capillary column gas chromatography/ mass spectrometry
• Method 525: Determination of organic compounds in drinking water by liquid-solid extraction and capillary column gas chromatography/ mass spectrometry

Key to Terminology

Pop Quiz

---

1. What is the component that most influences the separation of compounds?

a) injector

b) mobile phase

c) stationary phase

---

2. Given napthalene (boiling point = 218�C), phenol (boiling point = 181.7�C), and toluene (boiling point = 110.6�C). Which compound will elute first on a nonpolar column?

a) naphthalene

b) phenol

c) toluene

---

3. What will happen to the retention time if the flow rate is increased?

a) increase

b) decrease

c) no change

---

4. If a variable temperature program is used rather than an isothermal temperature program, what parameter will not be affected?

a) order in which compounds elute

b) retention time

c) peak height

---

5. What will happen to the peak height if the split ratio is decreased?

a) increase

b) decrease

c) no change

---

Five metals of five planets can cure variety of diseases

 

Gold and silver jewelry, steel items, brass coins and many other metal things have been known as healers since ancient times. However, most people do not treat metal as a method of treatment and consider it to be remnants of the past. Yet, metal therapy continues to help people. The most important aspect in this method is its simplicity, accessibility and the absence of side effects.

Metals of planets

In ancient times, there were only seven metals known, which corresponded to the number of planets that people knew. It was thought that metals were formed in Earth's interior under the influence of celestial bodies. They attributed metals to each celestial body. Gold was attributed to the sun, tin - to Jupiter, silver to the Moon, iron - to Mars, mercury - to Mercury, lead - to Saturn and copper - to Venus. Modern scientists count about 83 metals, but some of them possess intermediate properties and can hardly be regarded as metals.

Carry and apply

Jewelry made of different metals that people wear on the body for beauty show a permanent effect on the energy field.  As a rule, a person does not pay attention to that. In ancient times it was known that metals and their alloys had not only the material value, but also healing and energetic properties. Metals were used to treat and prevent various diseases. Nowadays, the action of metals on the human body continues to be studied, and their beneficial properties find new applications in traditional and alternative medicine.

Applying metal plates to different parts of the body that correspond to active points to improve health and heal people is known as metallotherapy or siderism. They can be used in various ways. One can apply metal plates to the affected area for a short period of time either directly or through cloth. One can also wear plates all the time. When metal gets into contact with the skin, this connection produces barely perceptible electric current, which affects energy flows in the body. Doctors and scientists proved that with the application of gold, copper, lead or zinc on the affected area, the current flows from the metal piece to the skin. When silver or tin is used, the current flows in the opposite direction - that is, from the skin to the metal. Therefore, gold, copper and lead are recommended to treat the diseases related to impaired functions of organs. Silver and tin are recommended for diseases of excessive functions.

  Gold

This highly reactive metal has unique healing properties. It is capable of attracting heat to the body, which is important when the body produces insufficient amount of energy. It is preferable to have old gold items of round shape. For example, family gold jewelry passed on from generation to generation have an ability to accumulate energy potential. Therefore, it is highly undesirable to part with them. In ancient times, gold was considered a powerful remedy to strengthen spirit and prolong life. A belief preserved from those times says that gold jewelry turn the evil eye away, strengthen the energy of the solar plexus. It is also believed that wearing a gold ring on a finger of the right hand extends life for a few years.

Modern scientists proved that this metal has a positive effect on the mood, invigorates and inspires confidence in the future. In addition, its sunny and bright glow shows a beneficial effect during seasonal depression. People who suffer from arrhythmia, can wear a gold medallion or a cross. Noteworthy, if gold jewelry gets dark or discolors over time, it means that there is a large percentage of metal-additives in this item. One should replace such an item without additives, since metals affect the body in different ways.

Gold has anti-inflammatory and anti-aging properties, so it is used in the production of a new generation of cosmetics. The precious metal is also used for age correction surgeries.

Silver

Women love to decorate themselves with various trinkets of silver, but not everyone knows that this metal is excellent doctor. For example, decorations on the neck calm the nerves. And if you wear silver on the ring finger of right or left hand - it removes excessive energy in blood circulation and reduces blood pressure. A ring on the index finger of both right and left hand normalizes the work of gastrointestinal tract. For heart invigoration, it is recommended to constantly wear a silver ring on the little finger of the left hand. Silver is also a great diagnostician. Silver things blacken, if a person has a problem in the endocrine system. And it may also happen that a silver item may become brighter than it was. This may indicate a serious kidney disorder, since sweat releases substances containing nitrogen, which comes into reaction with silver decorations and makes them shine. Medical drugs containing silver, unlike antibiotics, have a broader antibacterial spectrum. More importantly, they do not suppress the immune system.

People have long known that an alloy of gold and silver is a powerful health improver. Silver and gold-plated cutlery and crockery can disinfect food and water from harmful substances. Our ancestors knew that and used silver spoons to feed children. Coins of silver, when placed in water tanks, kill bacteria.

People's honor and respect to these metals can be seen even in etiquette. Dishes served on gold or silver plates have always been considered an expression of hospitality.

Iron

If you cut an apple with a steel knife, the cut will quickly darken due to the production of glandular salt of malic acid. The consumption of this substance contributes to the normalization of blood composition, especially after infectious diseases. It is recommended to eat grated apples twice a day, which is conducive to the work of the spleen and the liver. It also strengthens muscles and prevents anemia.

It is not recommended to wear things made of iron all the time. It can also be harmful to stay in a room for a long time, if there are many things made of iron in that room. A long stay in such a room will quickly lead to fatigue. In addition, it is bad to sleep with your head to a heater (a radiator), it leads to the destruction of the human biofield. Afterwards, a person may suffer from tiredness, irritability and headaches.

During an unpleasant conversation it is good to hold a iron object in your hand and mentally transmit negative emotions to this object.

Steel

This alloy of iron and carbon has the ability to "clean" the spine. To do this, one should run a steel knife upward along the whole spine (from the coccyx to the crown of the head) at a distance of 10-15 cm from the body. The exercise can be done with someone else's help several times a day.

Copper

Applying copper coins to the body can cure many diseases. This method is the most simple-minded kind of reflexology. Applications of copper remove fever, bruised pain, possess strong antibacterial properties, stop bleeding, improve metabolism, calm the nervous system, enhance the effect of insulin and heal inflammation in the body.

Treatment with copper

Metallotherapy technique is valuable because it can be applied to people of all ages, children and pregnant women. Copper coins or plates can be used for the treatment. The therapeutic effect will significantly increase if you polish the plate and drill holes in it. Before applying them to your body, heat them up for 10-20 minutes in a pan for 10-20 minutes, then let them cool down and rub them with sandpaper "to release copper" so to speak. You can put a copper plate in a glass containing an aqueous solution of sodium chloride (1 table spoon for a glass) for 1 hour. When dried, apply the plates to the affected area. Hold for at least 15 minutes and repeat the procedure every day for two weeks.

Siderism can be supplemented with the use of decoctions or infusions of herbs that help in heal the disease.

Useful tips

Headache will subside in 15-20 minutes if a copper coin is placed on the forehead, temples or back of the head, depending on the location of pain.

When having problems with digestion, put 2-4 coins in the area of the esophagus.

Blood pressure will reduce if you wear a copper rim on the head.

A bruise will disappear faster if you put a copper coin on it.

It is good to wear a copper bracelet on the wrist. It protects against insomnia, neurosis, hypertension crises, facilitates joint and muscle pains.

Green Laws: Is India in line with rest of the world?

Dec 28, 2013, 04.12 PM IST

Green Laws: Is India in line with rest of the world? There is a problem of quality of personnel, both at the industry level -- the consultants they employ -- and at the ministry level -- the quality of the experts who man the expert committees. If these issues are sorted out and there’s an intent to work together, then the delay in environment clearance can be avoided, feels Pradipto Ghosh of TERI

Two successive environment ministers in the UPA cabinet have been seen as obstructive of investments. Is India Inc unable to come to terms with environmental costs or is the ministry being unreasonable? According to environment ministry’s website, 72 coal mining projects are awaiting environmental clearance, out of which only nine came in 2013. The rest of them are pending for over a year. Ninety one mining projects awaiting environment clearance, only 25 came in this year. 118 industrial projects awaiting environment clearance, only 13 came in this year. If one does the math, 83 percent of the projects have waited well over one year. That’s the number of projects awaiting environment clearance, more than double that number of projects at any point in time await terms of reference from the ministry. Why this inordinate delay in clearance? Aren't there well laid out standards in most industries? Is the delay on account of haggling by the industry which doesn’t want to meet its obligations or is unable to understand the obligations or is it that the administration is either incompetent or the wrong people are in the assessment space?

Also Read: No files will be kept pending in Environment Min: Moily Below is the edited interview transcript

Q: Quickly if you can tell us what is a typical process that a project travels from the moment it enters the environment ministry to its final disposal? Ghosh: We are talking about the category A projects that is projects which are required to be appraised at the level of these central government. And there are other projects which are cleared at the level of the states. We are talking about the ones which require clearance at the central level. The process starts with the proponent submitting an application with a check list of the impacts of the proposed project to the ministry, which in turn submits it to the notified expert group. The expert group in consultation with the proponent and their consultants, develop the terms of reference for the environmental impact assessment (EIA) study. We need to understand that the EIA study is not a checklist which is tick-marked. It is a detailed technical examination which requires a year to produce and which typically is about 400-500 pages long.If this seems onerous, let me clarify that this is the worldwide practice, whether it is in the US, whether it is in Europe, whether it is in Australia, it is exactly the same kind of document. Then once the proponent has prepared the EIA document, and I must emphasize it is up to the proponent to prepare it, it is then submitted to the environment ministry and the expert committee has a 145 days to deliberate upon it in consultation with the project proponent and their consultants. Then at the closer of the period of 145 days they are supposed to send their recommendation within 15 days to the regulator, which happens to be the ministry. Then the ministry, which includes the minister concerned, can take another 45 days to take a final decision and of course if the ministry does not take a final decision at the level of minister within 45 days then the project proponent is deemed to have got environment clearance in clear legal terms on the basis of the minutes of the expert committee’s deliberation. So this is the process in short. Now in the course of this conversation I can point out to some of the reasons why it takes longer than that by way of comparison. The notified period in the World Bank for their own projects after submission of the EIA is one year, the notified period in the case of Canada is two years and this is -- in two years ago -- after they had comprehensively overhauled that environment clearance system. So the Indian system -- the way it is designed to work is not out of line by any means with the worldwide practice.

Q: If it is a 145 days or maybe 200 days at best that the ministry should take after a proposal is submitted for environment clearance, my numbers show that out of some 300-odd projects only 85 have come in this year, clearly many projects are waiting for well-over 365 days to get environmental clearance. I am sure you must have gone through environmental clearances for many of your projects, where is the bottleneck? Rao: As Dr Ghosh has explained there are category A and category B. So in the case of category A, the steps, which are involved, either for getting approval of expert appraisal committee (EAC) for terms of reference (TOR) and then preparing an environmental impact assessment report and then doing a public hearing. After public hearing again approaching environmental clearance and if at all it is located in the forest again forest 1 clearance, forest 2 clearance is a prerequisite for environmental clearance. There is no time limit for the forest clearances. After the forest clearance, it is referred for environmental clearance, if it is located near the wildlife sanctuary or any such area, wildlife departmental approval is required. That takes time. So if you see the whole process which is involved, it is not parallel, it is sequential. There is no single window clearance. If there is a problem at one stage then the project gets delayed. Q: Is that the only issue that it is not parallely done, these several clearances, or is it that even otherwise there is an unconscionably long time? Rao: It is unconscionably long time why I am saying again in a public hearing for instance if you have to have a public hearing, in my view, it should be restricted only to the items which are there in the environmental impact assessment study and will impact the environment. Today public consultation when it is happening, first the people who are not affected, outsiders will come to the public hearing, they also raise irrelevant issues which are nowhere connected with the project nor EIA. So all those grievances sought to be addressed before again we approach back, based on the minutes of the public hearing.

Read more at: http://www.moneycontrol.com/news/economy/green-laws-is-indialinerestthe-world_1015413.html?utm_source=ref_article

Dec 28, 2013, 04.12 PM IST Green Laws: Is India in line with rest of the world? There is a problem of quality of personnel, both at the industry level -- the consultants they employ -- and at the ministry level -- the quality of the experts who man the expert committees. If these issues are sorted out and there’s an intent to work together, then the delay in environment clearance can be avoided, feels Pradipto Ghosh of TERI Pradipto Ghosh, Distinguished Fellow ,TERI More about the Expert... Tags Environment Ministry, Pradipto Ghosh, TERI, Seshagiri Rao, JSW Steel Indianomics Share . Email . Print . A+ Two successive environment ministers in the UPA cabinet have been seen as obstructive of investments. Is India Inc unable to come to terms with environmental costs or is the ministry being unreasonable? According to environment ministry’s website, 72 coal mining projects are awaiting environmental clearance, out of which only nine came in 2013. The rest of them are pending for over a year. Ninety one mining projects awaiting environment clearance, only 25 came in this year. 118 industrial projects awaiting environment clearance, only 13 came in this year. If one does the math, 83 percent of the projects have waited well over one year. That’s the number of projects awaiting environment clearance, more than double that number of projects at any point in time await terms of reference from the ministry. Why this inordinate delay in clearance? Aren't there well laid out standards in most industries? Is the delay on account of haggling by the industry which doesn’t want to meet its obligations or is unable to understand the obligations or is it that the administration is either incompetent or the wrong people are in the assessment space? Former Environment Secretary and currently with TERI Pradipto Ghosh and Seshagiri Rao, Group CFO at JSW Steel, discuss the issue on CNBC-TV18. Also Read: No files will be kept pending in Environment Min: Moily Below is the edited interview transcript Q: Quickly if you can tell us what is a typical process that a project travels from the moment it enters the environment ministry to its final disposal? Ghosh: We are talking about the category A projects that is projects which are required to be appraised at the level of these central government. And there are other projects which are cleared at the level of the states. We are talking about the ones which require clearance at the central level. The process starts with the proponent submitting an application with a check list of the impacts of the proposed project to the ministry, which in turn submits it to the notified expert group. The expert group in consultation with the proponent and their consultants, develop the terms of reference for the environmental impact assessment (EIA) study. We need to understand that the EIA study is not a checklist which is tick-marked. It is a detailed technical examination which requires a year to produce and which typically is about 400-500 pages long.If this seems onerous, let me clarify that this is the worldwide practice, whether it is in the US, whether it is in Europe, whether it is in Australia, it is exactly the same kind of document. Then once the proponent has prepared the EIA document, and I must emphasize it is up to the proponent to prepare it, it is then submitted to the environment ministry and the expert committee has a 145 days to deliberate upon it in consultation with the project proponent and their consultants. Then at the closer of the period of 145 days they are supposed to send their recommendation within 15 days to the regulator, which happens to be the ministry. Then the ministry, which includes the minister concerned, can take another 45 days to take a final decision and of course if the ministry does not take a final decision at the level of minister within 45 days then the project proponent is deemed to have got environment clearance in clear legal terms on the basis of the minutes of the expert committee’s deliberation. So this is the process in short. Now in the course of this conversation I can point out to some of the reasons why it takes longer than that by way of comparison. The notified period in the World Bank for their own projects after submission of the EIA is one year, the notified period in the case of Canada is two years and this is -- in two years ago -- after they had comprehensively overhauled that environment clearance system. So the Indian system -- the way it is designed to work is not out of line by any means with the worldwide practice. Q: If it is a 145 days or maybe 200 days at best that the ministry should take after a proposal is submitted for environment clearance, my numbers show that out of some 300-odd projects only 85 have come in this year, clearly many projects are waiting for well-over 365 days to get environmental clearance. I am sure you must have gone through environmental clearances for many of your projects, where is the bottleneck? Rao: As Dr Ghosh has explained there are category A and category B. So in the case of category A, the steps, which are involved, either for getting approval of expert appraisal committee (EAC) for terms of reference (TOR) and then preparing an environmental impact assessment report and then doing a public hearing. After public hearing again approaching environmental clearance and if at all it is located in the forest again forest 1 clearance, forest 2 clearance is a prerequisite for environmental clearance. There is no time limit for the forest clearances. After the forest clearance, it is referred for environmental clearance, if it is located near the wildlife sanctuary or any such area, wildlife departmental approval is required. That takes time. So if you see the whole process which is involved, it is not parallel, it is sequential. There is no single window clearance. If there is a problem at one stage then the project gets delayed. Q: Is that the only issue that it is not parallely done, these several clearances, or is it that even otherwise there is an unconscionably long time? Rao: It is unconscionably long time why I am saying again in a public hearing for instance if you have to have a public hearing, in my view, it should be restricted only to the items which are there in the environmental impact assessment study and will impact the environment. Today public consultation when it is happening, first the people who are not affected, outsiders will come to the public hearing, they also raise irrelevant issues which are nowhere connected with the project nor EIA. So all those grievances sought to be addressed before again we approach back, based on the minutes of the public hearing.

Read more at: http://www.moneycontrol.com/news/economy/green-laws-is-indialinerestthe-world_1015413.html?utm_source=ref_article

SPECTROPHOTOMETRIC DETERMINATION OF IRON

SPECTROPHOTOMETRIC DETERMINATION OF IRON

Spectrophotometry:
For chemical species that appear to have color, it is a logical assumption that the intensity of the color is proportional to the concentration of the species in solution. We see color as a complement of the visible wavelength being absorbed by the sample. Things that appear red absorb blue visible light and reflect other visible colors to our eyes. Conversely, things that appear blue are absorbing red light. Absorption of light or more precisely electromagnetic radiation is related to available energy levels in the molecule or ion. A molecule in its "ground state" or lowest energy level can absorb energy to jump to an "excited state" or higher energy state. The amount of energy and therefore the wavelength of radiation involved in this transition is a function of the electronic structure of the molecule or ion.
The eye can only see a limited range of electromagnetic radiation, from approximately 400 to 700 nm. However, molecules, atom, and ions are capable of absorbing many different energies of radiation ranging from ultraviolet (UV) to microwaves depending on the specific energy levels being excited. For some types of energy changes, the wavelengths of light are very specific for certain types of chemical structure resulting in a method of qualitatively identifying chemical species. Other types of energy absorption may be less qualitative since it may relate only to bond types. In both cases however, our initial premise that intensity of absorption is related to concentration can be used for quantitative analysis.
Since our vision if not quantitatively calibrated, an electronic instrument called a spectrophotometer is used to precisely measure light intensities at given energy (wavelength) settings. A spectrophotometer is an instrument that measures the amount of transmission of light through a substance. The drawing below illustrates a simple spectrophotometer system consisting of a light (energy) source, a monochromator to select a given energy range, a sample, and a light intensity detector.

When light is absorbed by a sample, the radiant power or intensity of the light beam decreases. Radiant power, I, refers to the energy per second per unit area of the beam. In the figure, light passes through a monochromator that selects one wavelength. Light of this wavelength, with radiant power I0, passes through a sample of pathlength b. The radiant power of the beam emerging from the other side of the sample is I. Mathematically, the amount of light that is absorbed (A) is given by

Note that if no light is absorbed, A = 0 and if all the light is absorbed ( I = 0) then A = ¥. The amount of light absorbed by the sample should be proportional to the probability that the molecule or ion will absorb the electromagnetic radiation (a), the number of absorbing molecules or ions per unit volume that the light beam passes through (C), and the length of the light path (b). This relationship is quantified in the Beer-Lambert (or Beer's) Law which is 

A = a × b × C 

Note that this equation is in the form of Y = m × X + b where the intercept, b, is zero when X or the concentration, C, is zero. If we measure a series of solutions of known C at a given wavelength in a cuvet or sample cell with a constant pathlength, b, then we can determine the proportionality constant, m, which is a × b. This procedure generates a "calibration curve" which allows the determination of an unknown concentration, C_unk, from the measurement of the absorbance of the unknown, A_unk. Determination of the slope, m, and intercept, b, of the calibration curve gives

In this experiment, we will use a fiber optic diode array spectrophotometer.  A schematic diagram of this instrument is shown below.

The advantage of this instrument is that all wavelengths are recorded at once.  Therefore we can signal-average to reduce noise and apply other digital spectral smoothing techniques.  The spectrometer uses an incandescent tungsten lamp to produce radiation in the visible region.  In this experiment, we will only use spectral data between 400 and 6005 nm although every spectrum records data from 360 to 900 nm.

Fe(II)-phenanthroline spectrum	Structure of 1,10-phenanthroline

Many of the transition metal ions such as copper, nickel, cobalt, and chromium exhibit color in solution. However, this color can be made more intense by reacting the metal ion with a molecule that increases the absorbance of the metal ion. Iron(II), Fe²⁺, exhibits little color in solution. When Fe²⁺ reacts with the ligand o-phenanthroline (or 1,10-phenathroline), a stable, intensely colored red complex is formed that can be used to determine iron. The intensity of the color varies over the pH range of 2 to 9. In this procedure an ammonium acetate buffer will adjust the pH to between 6 and 9.  The iron must be in the +2 oxidation state, requiring a pre-reduction step before formation of the colored complex. Hydroxylamine is used as a reducing agent.
2 Fe³⁺  +  2 NH₂OH  +  2 OH^-      2 Fe²⁺  +  N₂  +  4 H₂O

Reagents:
	hydroxylamine solution	1:1 H2SO4
	sodium acetate solution	1,10-phenanthroline solution
	ferrous ammonium sulfate hexahydrate

EXPERIMENTAL PROCEDURE

Preparation of Standards and Determination of a Calibration Curve
You will be divided into groups to prepare the following solutions: 

1. Prepare a stock Fe solution by accurately weighing to the nearest 0.1 mg approximately 0.07 g of pure iron (II) ammonium sulfate hexahydrate and quantitatively transferring to a 1 L volumetric flask. 
2. Add 200 mL water and shake to dissolve any remaining solid. 
3. Add 5 mL of 1:1 sulfuric acid. 
4. Dilute to the mark with distilled water and homogenize thoroughly. 
5. Calculate the concentration of the solution in mg Fe/L.  
6. Prepare a series of standards by pipetting into each of five 100 mL volumetric flasks, 1.00, 5.00, 10.00, 25.00, and 50.00 mL aliquots of the stock Fe²⁺ solution (a buret can be used for this addition). 
7. Into a sixth 100 mL volumetric flask add approximately 50 mL of distilled water to serve as a blank. 
8. To all of the solutions add, in sequence 
         1 mL of hydroxylamine hydrochloride solution,
         10 mL of 1,10-phenanthroline, and
         8 mL of sodium acetate buffer.
9. Dilute to the mark, mix thoroughly, and allow to stand for 10 minutes. 

It is important to add all reagents in proper sequence.
Determination of Unknown Ferrous Ammonium Sulfate:

In order to prepare your unknown in the desired concentration range for the spectrophotometric measurement it will be necessary to do a serial dilution. Each student will individually prepare their own unknown. Be sure to record your unknown number in your lab notebook. 

1. Accurately weight 0.70-0.75 g of your unknown to the nearest 0.1 mg. 
2. Quantitatively transfer the solid to a 1 L volumetric flask. 
3. Add 200 mL of water, 5 mL of 1:1 H₂SO₄ and dissolve. 
4. Dilute to the mark and mix thoroughly 
5. Pipet a 10.00 mL aliquot into a 100 mL volumetric flask. 
6. Dilute to the mark and mix thoroughly 

Finally prepare the actual sample for analysis. 

1. Take a 20 mL aliquot (2 × 10 mL) of this second solution and place it in a 100 mL volumetric flask. 
2. Treat this as you did your standards by adding ·
         1 mL of the hydroxylamine solution,
         10 mL of the 1,10- phenanthroline solution, and
          8 mL of sodium acetate. 
3. Dilute to the mark, mix thoroughly and allow to stand for 10 minutes.

At this point each group should be ready to run their spectra.  Each should have 6 known solutions: the blank plus 5 different iron(II) concentrations plus one unknown for each group member.

Operating Procedure for the Red Tide/Logger Pro Spectrometers
Detailed Procedure for running a spectrum can be found on the Honors Chemistry 294L Web page.  The links are: Red Tide/Logger Pro Instructions

Calculations:
In order to calculate the concentration of iron in your unknown sample, a calibration plot must be calculated. A calibration plot or working curve is a plot of the analytical signal (the instrument or detector response; in this case the absorbance (A) on the y axis) as a function of known analyte concentration (C) on the x axis. This must be done at a specific wavelength.  These calibration plots are obtained by measuring the absorbance from a series of standards of known concentration at the wavelength of maximium absorbance. The calibration plots are then used to determine the linearity of response of an analytical method.
Use a spreadsheet to generate a plot of your data. Perform a least-squares regression analysis of your data to determine the slope and intercept. If you are using Excel, you can use the "add trendline" feature to draw your best regression line and choose the "show equation" option to obtain the slope and intercept. Use the standards to prepare a calibration curve as directed by your instructor. Plot absorbance vs. concentration. Check the linearity of the curve to see if Beer's Law is obeyed.

Spectrophotmetric Determination of Iron  —  Sample Data
Solution	Fe(II) conc.  (mg/L)	Absorbance
blank	0.00000	0.000
1	0.00025	0.056
2	0.00050	0.119
3	0.00100	0.194
4	0.00250	0.509
5	0.00500	1.046
unknown	0.00181	0.377
slope		207.8	=slope(y-values,x-values)
intercept		0.0001	=intercept(y-values,x-values)
unknown	mg Fe(II) /L	0.00181	=(y-intercept)/slope
			y=0.377