Monday, May 26, 2008

MASS SPECTROMETER (3) - Knowing what happen in


As Featured On Ezine Articles

The need for a vacuum

It's important that the ions produced in the ionisation chamber have a free run through the machine without hitting air molecules.

Ionisation



The vaporised sample passes into the ionisation chamber. The electrically heated metal coil gives off electrons which are attracted to the electron trap which is a positively charged plate.
The particles in the sample (atoms or molecules) are therefore bombarded with a stream of electrons, and some of the collisions are energetic enough to knock one or more electrons out of the sample particles to make positive ions.
Most of the positive ions formed will carry a charge of +1 because it is much more difficult to remove further electrons from an already positive ion.These positive ions are persuaded out into the rest of the machine by the ion repeller which is another metal plate carrying a slight positive charge.


Acceleration





The positive ions are repelled away from the very positive ionisation chamber and pass through three slits, the final one of which is at 0 volts. The middle slit carries some intermediate voltage. All the ions are accelerated into a finely focused beam

Deflection



Different ions are deflected by the magnetic field by different amounts. The amount of deflection depends on:
· the mass of the ion. Lighter ions are deflected more than heavier ones.
· the charge on the ion. Ions with 2 (or more) positive charges are deflected more than ones with only 1 positive charge.
These two factors are combined into the mass/charge ratio. Mass/charge ratio is given the symbol m/z (or sometimes m/e).
For example, if an ion had a mass of 28 and a charge of 1+, its mass/charge ratio would be 28. An ion with a mass of 56 and a charge of 2+ would also have a mass/charge ratio of 28.
In the last diagram, ion stream A is most deflected - it will contain ions with the smallest mass/charge ratio. Ion stream C is the least deflected - it contains ions with the greatest mass/charge ratio.It makes it simpler to talk about this if we assume that the charge on all the ions is 1+. Most of the ions passing through the mass spectrometer will have a charge of 1+, so that the mass/charge ratio will be the same as the mass of the ion. Assuming 1+ ions, stream A has the lightest ions, stream B the next lightest and stream C the heaviest. Lighter ions are going to be more deflected than heavy ones.

Detection


Only ion stream B makes it right through the machine to the ion detector. The other ions collide with the walls where they will pick up electrons and be neutralised. Eventually, they get removed from the mass spectrometer by the vacuum pump. When an ion hits the metal box, its charge is neutralised by an electron jumping from the metal on to the ion (right hand diagram). That leaves a space amongst the electrons in the metal, and the electrons in the wire shuffle along to fill it.
A flow of electrons in the wire is detected as an electric current which can be amplified and recorded. The more ions arriving, the greater the current.

Detecting the other ions
How might the other ions be detected - those in streams A and C which have been lost in the machine?
Remember that stream A was most deflected - it has the smallest value of m/z (the lightest ions if the charge is 1+). To bring them on to the detector, you would need to deflect them less - by using a smaller magnetic field (a smaller sideways force).
To bring those with a larger m/z value (the heavier ions if the charge is +1) on to the detector you would have to deflect them more by using a larger magnetic field.If you vary the magnetic field, you can bring each ion stream in turn on to the detector to produce a current which is proportional to the number of ions arriving. The mass of each ion being detected is related to the size of the magnetic field used to bring it on to the detector. The machine can be calibrated to record current (which is a measure of the number of ions) against m/z directly. The mass is measured on the 12C scale

Wednesday, May 21, 2008

MASS SPECTROMETER - (2). The Process in Mass Spectrometer

Atoms can be deflected by magnetic fields - provided the atom is first turned into an ion. Electrically charged particles are affected by a magnetic field although electrically neutral ones aren't.

The sequence is :

Stage 1: Ionisation
The atom is ionised by knocking one or more electrons off to give a positive ion. This is true even for things which you would normally expect to form negative ions (chlorine, for example) or never form ions at all (argon, for example). Mass spectrometers always work with positive ions.


Stage 2: Acceleration
The ions are accelerated so that they all have the same kinetic energy.


Stage 3: Deflection
The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected.
The amount of deflection also depends on the number of positive charges on the ion - in other words, on how many electrons were knocked off in the first stage. The more the ion is charged, the more it gets deflected.


Stage 4: Detection
The beam of ions passing through the machine is detected electrically.

MASS SPECTROMETER - (1). The Basic Principle

Mass spectrometer is one of very important tool in analytichal technique to determine isotope composition.

This page describes the basic principle of mass spectrometer.

If something is moving and you subject it to a sideways force, instead of moving in a straight line, it will move in a curve - deflected out of its original path by the sideways force.
Suppose you had a cannonball travelling past you and you wanted to deflect it as it went by you. All you've got is a jet of water from a hose-pipe that you can squirt at it. Frankly, its not going to make a lot of difference! Because the cannonball is so heavy, it will hardly be deflected at all from its original course.
But suppose instead, you tried to deflect a table tennis ball travelling at the same speed as the cannonball using the same jet of water. Because this ball is so light, you will get a huge deflection.
The amount of deflection you will get for a given sideways force depends on the mass of the ball. If you knew the speed of the ball and the size of the force, you could calculate the mass of the ball if you knew what sort of curved path it was deflected through. The less the deflection, the heavier the ball.

Tuesday, May 6, 2008

Nuclear Engineering '86 (Gadjah Mada University) Collegiate Reunion

Front Shadow Man: Hilman Ramli (IT Consultant)

Front (from right to left):
- Molasewarto (QA Manager at Matshusita)
- Herdin Ekalaksana (Conveyor & Welding QA Manager)
- Guntoro 'Bunder' (IT Ass Manager at Indomobil Suzuki)
- Nur Dewanto (Bakery Business Owner)
- Me
- Sarjono (BATAN)
- Pribadi Agung (Business & Investment Consultant)

Rear (from right to left):
- Kus Harjanto (Corporate Planning at Garuda Indonesia)
- Tubagus Ichsan Nurjaman (Leading Internet Marketer)
- Andryansyah (BATAN)
- Gatot Suhariyono (BATAN)
- I Made Surawan (Business Owner of Prod. House, Computer Course, Diploma Course etc.)
- Wardiyo (Marketing Coordinator at Nissan Diesel)

Located at our villa at Cipanas, the Nuclear Engineering collegiate reunion particapated by 14 persons from 38 persons total collegiate. Many of us could not participate caused by their workload.

We are so happy could meet our old friends. We talk about our old memories. Yes, we very happy to meet all of you my friends

The Study of the Lake Galunggung Crater Leakage

In 1992, our team was made the study of dam/lake water leakage at Mount Galunggung. The lake was formed from the Mount Galunggung Crater which is loaded the water from rain fall and springs. About 3 million m3 lake water at the crater could be a potential seriously threat if the crater wall is fall. We have to find out if there is any leakage at that wall, cause of it could make the wall structure more porous and after all can fall.

From the IAEA Feature story below, we know that the study like we did, was done by others at many country.


Isotopes to study and trace water leakage

In recent years, the use of isotope techniques to study the origin and path of water leakage from dams and reservoirs has been given specific emphasis.
In 1998, Specialized Teams, established to investigate the origins of dam leakage in Africa, achieved a great deal of success in less than one year. Teams consisting of four experts in hydrogeology, hydrochemistry, and isotope hydrology investigated three dams in Algeria, Morocco, and Namibia. The origin of the leakage in one of them has already been identified and appropriate solutions recommended, while in the case of the others, additional tests are underway to confirm initial results. The projected savings directly attributable to the timely identification of the origin of leakage in the Moroccan dam are estimated to be in the range of several million dollars.

In Venezuela, isotopic investigations pinpointed the area of leakage at the La Honda dam, resulting in millions of dollars of savings in remedial measures.
The flow rate of the Arenal river in Costa Rica increases dramatically downstream of the El Arnel dam. If this increase was due to leakage or seepage from the reservoir, the stability of the dam- accountable for 65% of the country’s electricity production- would have been endangered. An isotopic study showed that the river flow increased due to groundwater discharge and not leakage from the reservoir.
Another important use of isotope techniques is in investigating the effectiveness of surface reservoirs.

In Jordan, for example, millions of dollars have been invested to construct surface reservoirs in order to capture flood water for replenishing underground aquifer systems. Isotopic investigations have concluded that these surface reservoirs do not function properly, since no effective recharge to the aquifers could be substantiated. Any loss of water in the reservoir could be accounted for by surface evaporation. In view of these findings the use of such reservoirs should be reviewed by national water authorities in order to incorporate the engineering measures that will make them function cost effectively

POTENTIAL OF GROUNDWATER RESOURCES IN THE SPRING

DETERMINATION OF RECHARGE AREA AND GROUNDWATER AGE


1. INTRODUCTION AND BACKGROUND OF THE STUDY
Fresh or mineral water is very important in this new era. Production of fresh or mineral water can be done by make the well or explore from springs. The problem of the water explored by making well is the threat of the sea water infiltration to the land. The salty water is very dangerous for the building construction at all. Then the best healthy fresh or mineral water is produced from the spring.
The springs water that come out from the ground surface is a component of hydrologycal system within the hydrologycal cycle. In principle, the hydrologycal cycle involves process of cloud formation and condensation in the atmosphere cause rain when air is cooled to its dew point. The cooling is normally caused by adiabatic expansion of the uplifted air due to the decrease in atmospheric pressure with height. Part of the rainfall that reaches the earth will disappear by evaporation, and the remaining water may partly run off along the surface and partly infiltrate downward recharging the soil layer until it reached the water bearing zone.
Depend on the hydrogeologic condition, water in an aquifer system may originate from direct rainfall occurred above the ground that is called local recharge, or it may originate from rainfall occurred at higher area away from its water bearing zone. In the hydrological cycle of specific hydrological system, the stable isotope composition of water molecules are varies, depend on temperature this molecules are formed. Similar values of stable isotope composition of water populations in the hydrological system indicate that these populations are coming from similar resources.
Understanding of water resources, where the water comes from, how it moves, what its characteristics, to what extent the water will be utilized etc. is vital to its proper management.

Environmental isotope technique offers a broad range of possibilities for studying characteristics and process within the water cycle. The stable isotope label in water molecule containing 2H and 18O is heavier than normal molecule containing 1H and 16O. In condensation and evaporation, fractionation of heavier and lighter molecules is taken place. Condensation forming raindrops from a cloud will be enriched with heavy molecules than the remaining cloud in atmosphere. It is because most of the heavier molecules of water condense first and the cloud moisture subsequently will be a more depleted in heavy molecule of water as it goes upward toward a lower temperature. Thus rainfall takes place at a cooler temperature will have more depleted isotope composition than rainfall at a higher temperature. This phenomenon is the basic principle of the study to identify the recharge origin of groundwater.
The age of groundwater flowing out as spring water visualized residence time of water inside the water-bearing zone in the aquifer. There is an exchange process of CO2 in the atmosphere with carbonate compound dissolved in water; therefore the 14C content dissolved in water, as far as the water is still exposed to the atmosphere, is always constant. Once the water infiltrated into the ground, the radioactivity of 14C will decay exponentially according to its half-life (5730 years). By measuring the activity of 14C in groundwater, the residence time of the groundwater in corresponding points in the aquifer can be evaluated. When the age of water is relatively old, it means that the population of water has been retained for a long time in the aquifer system. This data suggest that as far as the recharge area is still conserved, the ground water reserves are relatively great.


2. OBJECTIVE OF THE STUDY
Objective of the study is:
· To determine the location of recharge origin in term of elevation ranges within the hydrological system.
· To assess the potential of groundwater resources through the determination of groundwater age


3. SCOPE OF WORK
Scope of work will consist of the following activities:
· Analysis of stable isotope composition of rainwater to represent the correlation of isotope composition of rain water with elevation. A graph representing the correlation of stable isotope composition (18O) with elevation will be used to estimate the recharge area of the respective groundwater. Rainfall collectors are set up successively at respective elevation in the study area. Trapped rainwater in the collectors is taken once or twice a month during period of rainy season. The mean values of isotope composition during sampling period are plot against corresponding elevation. This linear correlation will become isotope index of the rainfall that infiltrate into the ground and accumulated as groundwater.
· Analysis of stable isotope composition of spring water from the study area. Stable isotope of the spring water is fitted to the above-mentioned graph. The corresponding elevation in the graph will be an estimate of elevation of recharge area.
· Analysis of 14C of spring water from the study area to identify the age of groundwater

4. METHODOLOGY
Stable isotope 2H and 18O from rainwater or from groundwater is collected in a 20-ml of vial. These samples are brought to the laboratory for analysis of their composition.

Analysis of 2H
The 2H is prepared from the reaction of 10ml water sample with 0,25 gram of active Zinc in a closed tube heated to 4500C for about 30 minutes. The reaction is as follows:

H2O + Zn 450oC ZnO + H2
(Liquid) (Solid) (Solid) (Gas)


The hydrogen gas is discarded into a special tube for further analysis in mass spectrometer

Analysis of 18O
2 ml of water sample is reacted with CO2 gas. The exchange of oxygen-18 of water molecule and oxygen-16 of CO2 gas will take place, according to the reaction:

H218O + C16O2 H216O + C16O18O
(Liquid) (Gas) (Liquid) (Gas)

The reaction was carried out in an isoprep-18 on-line with the mass spectrometer


Analysis of 14C
About 60 liters of groundwater sample is poured into a precipitator plastic container. The dissolved carbonate is precipitated by adding 500 ml BaCl2 in basic condition to get precipitation of BaCO3. In the laboratory, precipitation of BaCO3 was converted to C6H6 in the benzene synthesis line according to the following reaction :

BaCO3 + 2HCl BaCl2 + H2O + CO2

2CO2 + 8Li 2C + 4Li2O

2C + 2Li Li2C2

Li2C2 + 2H2O C2H2 + 2LiOH

3C2H2 C6H6
(Benzene)
Carbon-14 of the benzene compound is counted using liquid scintillation counter to measure its 14C radioactivity