ICP-MS and ICP-AES are the preferred techniques for determining elemental impurities in pharmaceuticals according to recent ICH guidelines. ICP-MS can detect impurities below the ppt level, outperforming other techniques like GF-AAS (ppb range) and ICP-AES (ppb range). Speciation is important as different forms can have different toxicities, and ICP-MS coupled with separation techniques can perform speciation analysis down to ppt levels for quality control of pharmaceutical products.

1. Siva Chaitanya Addala
PA/2015/102

2. Contents
• Introduction
• Speciation studies
• Different instrumental analytical techniques for
elemental impurities
• References

3. Introduction
• Toxic metals like As, Pb, Cd, Hg, Se, Cr, Al, Ni, Cu and U enter
the human body via the food chain including medicines, ambient
air and drinking water leading to health problems.
• In addition, metal ions also can affect the stability and shelf life
of the formulation, catalyze the degradation of the API’s
leading to the formation of unqualified degradates
• Recently ICH has proposed safety standard guidelines for metal
impurities (Q3D) for the purpose of quality assurance of
pharmaceutical products

7. What is Speciation analysis ?
• Speciation analysis was first described in 1993 by Forstner
• The process of separation and quantification of different
chemical forms of an element is more specifically termed
speciation analysis.
• Inorganic As is much more toxic than the common organic
forms, such as arsenobetaine, (the sum of arsenite (As(III))
and arsenate (As(V)) is below the limit.
• Similarly, the Hg limit is based on inorganic Hg (Hg2+),
although methyl mercury (MeHg) is the more toxic form. The
presence of MeHg in pharmaceuticals is considered unlikely, but
it should be separated and measured specifically if samples are
derived from material (for example, fish tissue) that may
contain the compound in significant amounts.

9. • Distribution, Mobility, Bioavailability and Toxicity of
trace metals in environmental and biological systems
depend not simply on their concentrations, but
critically on their chemical forms
• Individual metal species posses different chemical
activity and ability to transform
• Speciation techniques using ICP-MS, ICP-AES, could
be considered as the most sensitive and selective
techniques

11. Different instrumental analytical
techniques for elemental impurities
• Atomic absorption spectrometry (AAS)
• X-ray florescence spectrometry (XRF)
• Instrumental neutron activation analysis (INAA)
• Inductively coupled plasma atomic emission
spectrometry (ICP-AES)
• Inductively coupled plasma mass spectrometry
(ICP-MS)

12. Atomic absorption
spectrometry (AAS)
• This technique is based on the principle that the amount of light
absorbed is a measure of the concentration of a particular analyte
at a particular wavelength
• GF-AAS is a technique which involves injection of a small amount
of solution to be analyzed into a small graphite tube and thus is
suitable for the analysis of metals at ultra-trace levels
• Mercury by ‘cold vapor’ method and some ‘volatile’ elements like
As and Sb can be measured as their hydrides . A major advantage
of cold vapor-AAS is the inherent separation of mercury from
the matrix .

14. Both F-AAS and GF-AAS allow reliable determination of metallic impurities
in pharmaceutical quality control operations.

15. Instrumental neutron activation analysis
(INAA)
• INAA is a relatively straightforward analytical technique for
determining elemental abundance in a wide range of materials.
• This technique relies on the measurement of characteristic radiation
from radionuclides formed directly or indirectly by neutron irradiation
of the material of interest. The energy of the emitted gamma rays is
used to identify the nuclide and the intensity of the radiation can be
used to determine its abundance.

16. • The advantages include,
I. The method is non-destructive, hence the same sample can be
used for other measurements;
II. Sample size can be very small, often as little as a milligram;
III. Detection limits for many elements are in the ng/g range;
IV. No sample preparation is required; and
V. Over 40 elements can be measured simultaneously.
• Because of these advantages, INAA used to be a very popular
analytical technique compared to other analytical methods until
ICPMS came in to use.
• As NAA does not require sample dissolution, it has a great advantage
over solution techniques such as AAS, ICPAES and ICP-MS.
• Despite the above advantages, INAA is certainly not a popular
analytical technique as it is time-consuming, not independent, requires a
reactor nearby and involves longer cooling times for certain elements.

17. X-ray florescence spectrometry
(XRF)
• In recent times XRF analysis
has become increasingly
attractive when compared to
other techniques, especially
due to the ease of sample
preparation.
• XRF spectrometry involves
irradiation of the sample
with high energy excitation
X-rays and measurement of
element-specific
fluorescence X-rays at a
particular wavelength or
energy from the sample .
Samples can be in solid,
powder or liquid form.

18. • Since it is a non-contact analysis, problems such as memory effects
commonly experienced in solution analysis, are not encountered.
• As it is a non-destructive technique, it is possible to reuse the
sample after measurements.
• Both forms, namely, wavelength dispersive-XRF (WD-XRF) and
energy dispersive-XRF (EDXRF) techniques have been successfully
applied for the determination of Zn, Fe and Ni in API’s .
• Though there are several studies on the application of XRF
techniques in pharmaceutical industry, because of the higher
detection limits, they are not very popular for quantitative
determinations of metal impurities in pharmaceutical samples.

19. Inductively Coupled Plasma
What is a Plasma?
•Plasma source provides atomization
•Plasma: “a gas-like phase of matter that
consists of charged particles”
•ICP-AES plasma source is from the carrier
gas
Typically argon is used

20. • ICP is a very powerful ionisation source
• Elements with IP < 8 eV are ionised to > 90%
• LODs for most metals are <ppb level
• Sample introduction is very versatile: liquid, gaseous or even
solid samples can be ionised in the Plasma
• The sample introduction allows a (relatively) straightforward
coupling of chromatographic separation systems (GC, HPLC)
• ICP-MS detection is fast and multi-element capable
• A large variety of element speciation tasks can be tackled by
GC or HPLC coupled to ICP-MS

21. • ICP-AES technique involves measurement of light emitted by
the elements in a sample when introduced into an ICP source.
• The measured emission intensities are then compared to the
intensities of standards of known concentrations to obtain the
respective elemental concentrations in an unknown sample .
.
Inductively Coupled Plasma Atomic
Emission Spectrometry (ICP-AES)

22. • Limits of detection were at least a factor of ten below the USP
limit concentrations confirming that the ICP-AES technique is
well suited for quantitative determination of elemental impurities
in pharmaceutical samples.
•The technique can simultaneously measure up to 60 elements
with high sensitivity and an extraordinarily wide linear dynamic
range which is perhaps the most outstanding feature of the ICP-
AES
• The general chapter USP <233> includes two analytical
procedures involving ICP-AES and ICP-MS for determination of
elemental impurities in pharmaceuticals and includes a
comprehensive validation procedure to ensure acceptability of
results .
• Compared with F-AAS, ICP-AES provides lower detection limits,
has multielement capability and a wider linear dynamic range

23. Inductively coupled plasma mass
spectrometry (ICP-MS)
ICP-MS combines a high-temperature ICP source with a mass
spectrometer. The ICP source converts atoms of the elements in the
sample to positively charged ions. These ions separated on the basis
of mass-to-charge ratio in a mass spectrometer, are directed to a
detector .

25. .
• Further advances such as the advent of HR- ICP-MS and ICP-TOF-
MS, during the last three decades have brought this technique to a
point where this technique can deliver detection limits of one part in
1015 for a majority of elements in the periodic table.
• Detection limits are also far below the target limits in accordance
with the analytical performance criteria described in USP 233. In
fact.
• ICP-MS is one of the two spectroscopic methods which are included
in the General chapter USP <233> for determination of elemental
impurities in pharmaceuticals.

26. COST

27. Detection Limits
• ICP-MS produces the best detection limits (typically 1-10 ppt)
• Followed by GFAAS, (usually in the sub-ppb range) then ICP-AES
(of the order of 1-10 ppb) and finallyFAAS (in the sub-ppm range).

30. References
• V. Balaram ; Recent advances in the
determination of elemental impurities in
pharmaceuticals – Status, challenges and
moving frontiers ; Trends in Analytical
Chemistry