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ATOMIC EMISSION SPECTROMETRY


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Proses Absorpsi Energi Oleh Atom Dilanjutkan Dengan ProsesEmisi Energi Oleh Atom Yang Tereksitasi.


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Hubungan antara populasi keadaan dasar dan keadaan eksitasi

sebagai fungsi temperatur diberikan oleh persamaan boltzmann

kT

E

i eg

g

N

N

00

1

Dimana :

gi/go = angka banding bobot-bobot statistik untuk keadaan dasar dan keadaan eksitasi

E = Energi pada keadaan tereksitasi relative ke keadaan ground state (Eo=0)

k = konstanta Boltzmann (1.3807 x 10-23 J/K)

T = temperature (K)

N1 = banyaknya atom dalam keadaan eksitasi

N0 = banyaknya atom keadaan dasar


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I. Introduction

Basic Schematic

Scanning instruments can detect multiple elements.

Many lines detected so sometimes it is a quantitativelydifficult method.

Source can be flame, but more commonly plasma because it is

much hotter.


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Jenis-jenis teknik atomisasi

Jenis Atomisasi Temperatur Atomisasi (oC)

Flame (nyala) 1700-3150

Electrothermal vaporisation 1200-3000

Inductively coupled argon plasma (ICP) 4000-6000

Direct current argon plasma (DCP) 4000-6000

Microwave-induced argon plasma (MIP) 2000-3000

Glow-discharge plasma (GD) Nonthermal

Electric arc 4000-5000

Electric spark 40000 (?)


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Fotometer nyala

Li

K

Na

Ca

Ba

Pemilihan

digunakan filterDetektor : foto sel


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II. PLASMA SOURCESPlasma - Campuran gas yang sebagian terion : Ar, Ne, He

There are three types of plasma sources:

A) Inductively coupled plasma (ICP) , plasma induktif gel radioB) Direct current plasma (DCP), plasma arus searah

C) Microwave induced plasma (MIP) , plasma induksi gel mikro

ICP is the most common plasma source.


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A. INDUCTIVELY COUPLED PLASMA (ICP) Constructed of three concentric quartz

tubes.

Ke pipa Cu dilewatkan arus bolak

balik dgn kekuatan 0,5-1,5 KW.

Gas plasma berputar ke atas

Arus listrik lewat kumparan

menghasilkan medan magnit.

Pemancing plasma kumparan

tesla

Kumparan tesla menghasilkan listrik

tegangan tinggi

Medan magnit menghalangi muatanelektron

Dorongan dari bawah dan hambatan

dari atas timbul panas

Di dalam panas timbul plasma

Gas naik mngelilingi tabung sekaligusendin in


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A. INDUCTIVELY COUPLED PLASMA (ICP)1. Sample Introduction

Sample nebulized in a stream of argon

with a flow rate of 0.3

1.5 L/min. Sample aerosol enters the plasma at the

base through the central tube.

a. Liquid Samples

Nebulizer similar to FAAS

b. Solid Samples

Sample atomized by electrothermal

atomization and carried into the

plasma by a flow of argon gas.


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A. INDUCTIVELY COUPLED PLASMA (ICP)2. Plasma Appearance

Radiation from this region is a

continuum with the argon line

spectrum superimposed.

Temperature: 8000-10000K

a. Excitation Region

The bright, white, donut shaped

region at the top of the torch.

b. Observation Region

The flame shaped region above the

torch with temperatures ~1000-8000K.

The spectrum consists of emission

lines from the analyte along with

many lines from ions in the torch.


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A. INDUCTIVELY COUPLED PLASMA (ICP)

3. Analyte Atomization and Ionization Advantage of ICP over flame:

a) Temperature is two to three times higher than in a flame or

furnace, which results in higher atomization and excitationefficiencies.

b) There is little chemical interference.

c) Atomization in the inert (argon) atmosphere minimizes oxidation

of the analyte.

d) Linear calibration curves can cover up to five orders of

magnitude.


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B. DIRECT CURRENT PLASMA (DCP) Constructed of two graphite anodes in a Y

formation with a tungsten cathode.

The argon flows out around the anodesand the plasma forms at the split in the Y.

The plasma is ignited by bringing the

cathode in contact with the anodes.

Sample is introduced into the plasma in a

stream of argon that flows from between

the two anodes.

The plasma excitation temperature is

10,000 K and the observation

temperature is 5000 K.Advantages vs. ICP

Fewer emission lines.

Less argon required.

Less expensive and bulky.

Disadvantages vs. ICP

Poorer sensitivity

Higher maintenance.

Few commercially available.


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ULTRASONIC NEBULIZER WITH DESOLVATION

Sampel yang masuk digetarkan oleh gel, menjadi kabut, di

dorong oleh gas masuk ke dalam nyala


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III. PLASMA SOURCE INSTRUMENTS Two basic instrument designs; sequential and multi-channel detection

Monochromator yang scan spektrum, berhenti pada masing-masing panjang

gelombang analitis untuk mencapai rasio signal-to-noise diinginkan

A. Sequential (Scanning) Instruments

Secara teoritis, tidak ada batas

jumlah analisa yang ditampilkanpada sampel yang sama.

Pada kenyataannya, jumlah

analisa dibatasi oleh jumlah

sampel, tingkat konsumsi sampel,

dan waktu yang diperlukan untuk

masing-masing analisa.


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III. PLASMA SOURCE INSTRUMENTSB. Multi-channel Instruments

Multi-channel analyzer

allows for simultaneous

acquisition from eachPMT.

60 elements can be

analyzed in the same

amount of time that it

takes to analyze oneelement on a scanning

instrument.

Sampai 60 photomultiplier tubes( PMT) ditempatkan secara langsung di

bidang fokus yang dibengkokkan suatu diffraction grating cekung.

1. Rowland Circle Instrument

Saves time, sample, and

money.


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III. PLASMA SOURCE INSTRUMENTSB. Multi-channel Instruments

Low resolution grating disperses the radiation onto a prism.

2. Echelle Polychromator Instrument

Radiasi satu dimensi dilewatkan melalui sebuah prisma lebih lanjut

diuraikan kembali ke arah yang berbeda sehingga terjadi spektrum dua

dimensi yang dipusatkan pada celah plate yang dicocokkan dengan PMTs

or diode arrays.

Menyediakan resolusi lebih baik dibanding monochromator tunggal danmemungkin pendeteksian bersama beberapa unsur-unsur.


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ULTRASONIC NEBULIZER WITH DESOLVATION

Sampel yang masuk digetarkan oleh gel, menjadi kabut, di

dorong oleh gas masuk ke dalam nyala


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PICTURE OF AN INDUCTIVELY-COUPLED PLASMA ATOMIC

EMISSION SPECTROMETER

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