Atomic Spectroscopy Atomic Spectrophotometry Atomic Adsorption AAS Atomic Emission AES

1. ATOMIC
SPECTROPHOTOMETRY
Prepared by: Sarah Khallad
MSc Pharmaceutical Sciences – UOP
1

2. Contents
 Introduction
 Atomic Emission Spectrophotometry (AES)
• Introduction
• Instrumentation
• Applications in Pharmaceutical Analysis
• Examples of Quantitation by AES
• Assays Based on the Method of Standard Additions
• Interferences in AES Analysis
• Conclusion for AES
 Atomic Absorption Spectrophotometry (AAS)
• Introduction
• Instrumentation
• Applications in the Pharmaceutical Industry
• Examples of Assays Using AAS
• Conclusion for AAS
• Comparison between AAS and AES
 References
2

3. Atomic
Spectroscopy
Optical
Atomic
Spectroscopy
Atomic
Emission
Spectroscopy
Atomic
Absorption
Spectroscopy
Atomic
Fluorescence
Spectroscopy
Atomic Mass
Spectroscopy
(MS)
3

4. Introduction
• The interactions of radiation and matter are the subject of the science
called spectroscopy.
• Spectroscopic analytical methods are based on measuring the
amount of radiation produced or absorbed by molecular or atomic
species of interest.
• We can classify spectroscopic methods according to the region
of the electromagnetic spectrum used or produced in the
measurement. The g-ray, X-ray, ultraviolet (UV), visible, infrared (IR),
microwave, and radio-frequency (RF) regions have been used.
• Indeed, current usage extends the meaning of spectroscopy yet
further to include techniques such as acoustic, mass, and electron
spectroscopy in which electromagnetic radiation is not a part of the
measurement.
4

5. Atomic Spectroscopy
• Atomic spectroscopic methods are used for the
qualitative and quantitative determination of more than
70 elements.
• Typically, these methods can detect parts-per-million
(PPM) to parts-per-billion amounts(PPB), and in some
cases, even smaller concentrations.
• Atomic spectroscopic methods are also rapid,
convenient, and usually of high selectivity.
5

6. Regions of the Electromagnetic Spectrum
6

7. Visible Light
7

8. The Particle Nature of Light: Photons
• In many radiation/matter interactions, it is useful to
emphasize the particle nature of light as a stream of
photons or quanta.
8

9. ATOMIC EMISSION
SPECTROPHOTOMETRY
(AES)
9

10. Atomic Emission Spectrophotometry (AES)
• Atoms contain various energy
states, as illustrated the figure for
the sodium atom.
• The normal unexcited state is the
ground state.
• Sodium contains one electron in its
outer (3p) orbital and, if external
energy is gained by the atom
(absorbance), this electron may be
excited to a higher state(3p, 4p,
5p) and then after a few
nanoseconds lose its energy
(emission) by falling back to a
lower energy orbital as photons of
visible or ultraviolet radiation.
Principle
10

11. Principle cont.
• When elements are transformed into atomic vapour at
high temperatures, emission or absorption of light may
occur and this can be accurately measured at a unique
resonant wavelength, which is characteristic of the
emission/ absorption lines of the elements concerned.
• Using this basic process, the concentrations of most
elements may be estimated by measuring the amount of
radiation either emitted by the sample (emission
spectrometry) or absorbed by the sample following
production by a primary radiation source (absorption
spectrometry).
11

12. Instrumentation
12

13. Instrumentation cont.
An atomic emission spectrophotometer is composed of the following
components:
(i) Flame(Atomizer, Emission source).
In all atomic spectroscopic techniques, we must atomize the sample,
converting it into gas-phase atoms, and ions.
Samples usually enter the atomizer in solution form, although we sometimes
introduce gases and solids.
(ii) Monochromator/Filter.
The radiation emitted by the excited atoms is passed through a filter, or a
monochromator in more expensive instruments.
Thus a narrow band of emitted radiation is selected and interfering
sources of radiation such as the flame and other components in the sample
are screened out.
(iii) Detector.
The intensity of the selected radiation is then measured using a
photosensitive cell.
13

14. Instrumentation Continue..
Atomization Method
Note: Atomization is a critical step in atomic spectroscopy.
Atomization is a process in which a sample is converted into gas-phase atoms
or elementary ions.
The ICP is now the most popular source for emission spectrometry.
Atomization
Method
Typical Atomization
Temperature Common Name and Abbreviation
Inductively
Coupled
Plasma 6000–8000
Inductively coupled plasma atomic
emission spectroscopy, ICPAES
Flame 1700–3150 Atomic emission spectroscopy, AES
Direct-current
plasma 5000–10,000 DC plasma spectroscopy, DCP
Electric arc 3000–8000 Arc-source emission spectroscopy
Electric spark
Varies with time and
position Spark-source emission spectroscopy
Atomization Method
Typical Atomization
Temperature
Common Name and
Abbreviation
Inductively Coupled Plasma 6000–8000
Inductively coupled plasma
atomic emission spectroscopy,
ICPAES
Flame 1700–3150
Atomic emission spectroscopy,
AES
Direct-current plasma 5000–10,000 DC plasma spectroscopy, DCP
Electric arc 3000–8000
Arc-source emission
spectroscopy
Electric spark Varies with time and position
Spark-source emission
spectroscopy
14

15. Monochromator
15

16. .
16

17. Applications in Pharmaceutical Analysis
1. Quantification of alkali metals in: alkali metal salts,
infusion and dialysis solutions.
2. Determination of metallic impurities in some of the other
inorganic salts used in preparing these solutions.
(Potential metallic contamination).
3. Cleaning validations.
4. Elemental fingerprinting.
17

18. Quantification of alkali metals in: alkali
metal salts, infusion and dialysis solutions.
18

19. Determination of metallic impurities in some of the
other inorganic salts used in preparing these solutions.
19

20. Determination of metallic impurities in some of the
other inorganic salts used in preparing these solutions
20

21. Cleaning Validations
21

22. Elemental Fingerprinting
22

23. 23

24. Examples of Quantitation by AES
• In order to measure a sample by AES, a calibration
curve is constructed by aspirating solutions of known
concentration into the flame.
24

25. Examples of Quantitation by AES:
25

26. Table 6.1
26

27. Assay of Sodium and Potassium Ions in an I.V. Infusion cont.
1000ml
Standard Solution
NaCl 0.5092 g
KCl 0.1691 g
Dilutions on standards:
Step 1:
20 ml 100ml
Diluted standard solution
Step 2:
Calibration Series
0 ml 5 ml 10 ml 15 ml
100ml100ml100ml100ml100ml
Infusion Solution
(Sample)
25 ml
Step 1:
5 ml
250ml 100ml
Step 2:
10ml
27

28. Examples of Quantitation byAES :Assay of Sodium and Potassium Ions in
an I.V. Infusion
Calculation
28

29. Calculation cont.
1000ml
Standard Solution
NaCl 0.5092 g
KCl 0.1691 g
Dilutions on standards:
Step 1:
20 ml 100ml
Diluted standard solution
Step 2:
Calibration Series
0 ml 5 ml 10 ml 15 ml
100ml100ml100ml100ml100ml
Infusion Solution
(Sample)
25 ml
Step 1:
5 ml
250ml 100ml
Step 2:
10ml
X5
X20
X50 X10 Total dilution in
sample:
50x10=500
29

30. Calculation cont.
30

31. Self Test 6.1
31

32. Assays Based on the Method of
Standard Additions
• The method of standard additions can be used with many
analytical techniques where interference from the
matrix has to be eliminated and is of general use in
residue or trace analysis.
• Essentially the technique involves addition of increasing
volumes of a standard solution to a fixed volume of the
sample to form a calibration series.
• An advantage of the technique is that, since several
aliquots of sample are analyzed in order to produce the
calibration series, the method gives a measure of the
precision of the assay.
32

33. Method of StandardAdditions
33

34. Standard Additions Curve
34

35. Interferences in AES Analysis
Ionisation
At high flame temperatures, atoms such as K may completely lose an
electron, thus reducing the observed emission from the sample.
(To suppress the ionisation, we can add another readily ionised
element to the sample, which produces electrons).
Viscosity
Organic substances in a sample can either increase or decrease the
rate at which it is drawn into the flame relative to a standard
solution(blank) by increasing or decreasing the viscosity.
Anionic interference
Anions such as sulphate and phosphate form involatile salts with
metal ions and reduce the reading of the sample solution.
(These anions may be removed by precipitation).
35

36. Conclusion for AES
 Principles
Atoms are thermally excited so that they emit light and the radiation emitted is
measured.
 Applications in pharmaceutical analysis
Quantification of alkali metals in: alkali metal salts, infusion and dialysis
solutions.
Determination of metallic impurities in some of the other inorganic salts used in
preparing these solutions.
 Strengths
Flame photometry provides a robust, cheap and selective method based on
relatively simple instrumentation for quantitative analysis of some metals.
 Limitations
Only applicable to the determination of alkali and some alkaline earth metals.
36

37. ATOMIC ABSORPTION
SPECTROSCOPY
37

38. Introduction
• Flame atomic absorption
spectroscopy (AAS) is currently the
most widely used of all the optical
atomic methods because of its
simplicity, effectiveness, and
relatively low cost.
• AAS is a much more sensitive
technique than AES.
• Only a single element can be
determined at a time, this is the
major drawback of AA.
38

39. Principle
Metal atoms are volatilized in a flame and radiation is passed through the flame.
In this case, the volatilized atoms, which are mainly in their ground state and
thus not emitting energy, will absorb radiation with an energy corresponding
to the difference between their ground state and the excited state.
39

40. Instrumentation
40

41. Instrumentation
(i) Light source. A hollow cathode lamp coated with the
element being analyzed.(The most useful radiation source
for atomic absorption spectroscopy)
(ii) Flame cell
(iii) Monochromator
(iv) Detector
41

42. Light source: A Hollow Cathode Lamp
• A Hollow Cathode Lamp contains a cathode of the
analyte element and an anode, and are filled with
a noble gas.
42

43. Instrumentation
43

44. Instrumnetation cont.
Atomization Methods for AAS
Atomization Method
Typical Atomization
Temperature C
Common Name and
Abbreviation
Flame 1700–3150
Atomic absorption
spectroscopy, AAS
Electrothermal 1200–3000 Electrothermal AAS
44

45. Applications in Pharmaceutical Analysis
1. Determination of metal residues remaining from the
manufacturing process in drugs.
2. Determination of metallic impurities, that could be toxic
like Pb, Hg, As and Cd.
3. Cleaning validations.
4. Determination of some drugs. (Directly or Indirectly)
45

46. 46

47. Determination of metal residues remaining from the
manufacturing process in drugs.
47
https://www.sciencedirect.com/science/article/abs/pii/S0039914001003241

48. Determination of metallic impurities, that could be toxic
like Pb and Cd.
48

49. Cleaning Validations
49

50. Metals in Pharmaceuticals (Examples)
https://www.sciencedirect.com/science/article/pii/S0731708510006734
50

51. Determination of Drugs Using AAS
51

52. Determination of Drugs Using AAS
52

53. Examples of Assays Using AAS
53

54. Examples ofAssays Using AAS cont.
Assay of Calcium and Magnesium in Haemodialysis Fluid
100ml
100ml
250ml
Haemodialysis Fluid
(Sample)
Standard Solution
Conc.: 10.7 mg/100 ml
Standard Solution
Conc.: 11.4 mg/100 ml
10 ml
10 ml
5 ml
(For Ca analysis)
Diluted
Standard
Solution
X50
X10
X10
54

55. Table 6.3
55

56. Examples ofAssays Using AAS cont.
Calculation
56

57. Conclusion for AAS
Principles
Atoms of a metal are volatilised in a flame and their absorption of
a narrow band of radiation produced by a hollow cathode lamp,
coated with the particular metal being determined, is measured.
Applications in pharmaceutical analysis
Determination of metal residues remaining from the
manufacturing process in drugs.
Strengths
More sensitive than AES. A highly specific method of analysis
useful in some aspects of quality control.
Limitations
Only applicable to metallic elements.
Each element requires a different hollow cathode lamp for its
determination.
57

58. Comparison between AAS and AES
58
AAS AES
Process measured Absorption(light
absorbed by unexcited
atoms in the flame)
Emission(light emitted by
exited atoms in a flame)
Use of flame Atomization Atomization & Excitation
Instrumentation Light source No light source
Beer Lambert’s Law Applicable Not Applicable
Data obtained Abs. vs. Conc. Intensity vs. Conc.

59. Comparison between AAS and AES
59

60. References (Books):
• Watson,D.(2012).Pharmaceutical Analysis.(3rd Edition).
• Skoog,D., West,D., Holler,F., Crouch,S.(2013).Fundamentals of
Pharmaceutical analysis.(9th Edition).
• Abu Dayyih.W., Mallah, E., Hamad, M. Main Concepts in
Quantitative Analysis Analytical Chemistry.
• Christian,D.(2014).Analytical chemistry.(7thEdition).
• Harris, D.(2018).Quantative Chemical Analysis.(8th Edition)
• Akash,M.,Rehman,K.(2020).Essentials of Pharmaceutical
Analysis(1ST Edition)
60

61. References (Articles):
• R. Raghavan, J.A. Mulligan, Low-level (ppb) determination of cisplatin in cleaning validations (rinse water) samples. I. An atomic absorption
spectropho- tometric method, Drug Dev. Ind. Pharm. 26 (2000) 423–428.
• N. Lewen, D. Nugent, The use of inductively coupled plasma-atomic emission spectroscopy (ICP-AES) in the determination of lithium in cleaning
validation swabs, J. Pharm. Biomed. Anal. 52 (2010) 652–655.
• T. Wang, S. Walden, R. Egan, Development and validation of a general non- digestive method for the determination of palladium in bulk
pharmaceuticals and their synthetic intermediates by graphite furnace atomic absorption spec- troscopy, J. Pharm. Biomed. Anal. 15 (1997) 593–
599.
• The United States Pharmacopeia/The National Formulary, USP 32/NF 27. Chapter 851, Spectrophotometry and Light Scattering. The United
States Phar- macopeial Convention, Rockville, MD, 2010, pp. 373–378.
• O.E.Orisakwe,J.K.Nduka,Leadandcadmiumlevelsofcommonlyadministered pediatric syrups in Nigera: a public health concern? Sci. Total Environ.
47 (2009) 5993–5996.
• K. Sugisawa, T. Kaneko, T. Sago, T. Sato, Rapid quantitative analysis of magne- sium stearate in pharmaceutical powders and solid dosage
forms by atomic absorption: method development and application in product manufacturing, J. Pharm. Biomed. Anal. 49 (2009) 858–861.
• [50] M.M. Issa, R.M. Nejem, M. Al-Kholy, N.S. El-Abadla, R.S. Helles, A.A. Saleh, An indirect atomic absorption spectrometric determination of
ciprofloxacin,
• amoxicillin and diclofenac sodium in pharmaceutical formulations, J. Serbe.
• Chem. Soc. 75 (2008) 569–576.
• M.A. El Ries, S. Khalil, Indirect atomic absorption determination of atropine, diphenhydramine, tolazoline, levamisole based on formation of ion-
associates with potassium tetraiodomercurate, J. Pharm. Biomed. Anal. 25 (2001) 3–7. [73] A. Lásztity, Á. Kelkó-Lévai, I. Varga, K. Zih-Perényi,
É. Bertalan, Development of atomic spectrometric methods for trace metal analysis of pharmaceuticals,
• Microchem. J. 73 (2002) 59–63.
https://www.sciencedirect.com/science/article/pii/S0731708510006734
• https///www.researchgate.net/publication/287337891_Elemental_Fingerprint_of_Herbal_Medicines_Formed_by_Inductively_Coupled_Plasma_At
omic_Emission_Spectroscopy_ICP-AES/link/57a8de9708ae0107eee7154f/download
• https///www.ncbi.nlm.nih.gov/pubmed/11274852
• https///www.ncbi.nlm.nih.gov/pubmed/20227219
• https///www.researchgate.net/publication/47348865_The_application_of_atomic_absorption_spectrometry_for_the_determination_of_residual_acti
ve_pharmaceutical_ingredients_in_cleaning_validation_samples/link/5416baa20cf2bb7347db6d54/download
• https///www.sciencedirect.com/science/article/abs/pii/S0039914001003241?via%3Dihub
• https///www.researchgate.net/profile/Rafat_Nejem/publication/26513471_An_indirect_atomic_absorption_spectrometric_determination_of_ciproflo
xacin_amoxycillin_and_diclofenac_sodium_in_pharmaceutical_formulations/links/0f31752da502e50bd3000000.pdf
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