Introduction to pharmacy : Assignment

Pharmacy

Table of Contents
INTRODUCTION ..........................................................................................................................1
MAIN BODY...................................................................................................................................1
1) End capping of C18............................................................................................................1
2a) Functional group chemistry..............................................................................................1
2b) Hydrophilic interaction Liquid Chromatography.............................................................2
3) Discuss four types of HILIC stationary phases..................................................................3
4) Separation of amphetamine................................................................................................4
CONCLUSION................................................................................................................................4
REFERENCES ...............................................................................................................................6

INTRODUCTION
Pharmacy refers to a branch of science and an effective technique to manufacture drugs
and dispensing the same. It involves an appropriate connection among health science and
chemicals. Moreover, it include the process utilizing chemicals to develop useful compounds in
order to make people disease free (Luo and et. al., 2011). It involves various related practice
areas such as pharmacy of community, hospital, clinical, ambulatory care, compounding,
consulting, internet, veterinary, nuclear, military and specialty. The present assignment will
focus on end capping, functional group chemistry and liquid chromatography. It also include
discussion about separation of amphetamine.
MAIN BODY
1) End capping of C18
In context of chromatography, end capping can be described as a process of replacing
silanol groups in a bonded stationary phase by trimethylsilyl groups. C18 columns are high
performance liquid chromatography which can utilise C18 substances as the stationary phase.
Moreover, it is used in environmental sciences, chemical analyses and pharmacological industry
to evaluate particular elements of chemical mixtures.
Advantages of end capping – Firstly, it provide non- acidic and non- polar silica but
bare silica gel is polar with its free silanols. Moreover, the polar interaction facilitate separation
in chromatography but functionalised silica is utilized as reagent and the interaction occur with
grafted function along with not a non- specific binding with surface. Secondly, functional silica
can be put-upon in rough condition and end capping prevents opencast from being attacked or
damaged.
Purpose of end capping – A column can be considered as end capped while a small
silylating agent like trimethylchlorosilane which is utilized to chemical bond residual silanol
groups on surface of packing. The main purpose of end capping is to improve peak shape, reduce
tailing, increase resolution and selectivity (Castelletto and et. al., 2011).
2a) Functional group chemistry
Functional group chemistry refers to part of organic chemistry in which several
functional groups are included such as atoms, ions or group of atoms which has consistent
properties. It involve certain examples including hydroxyl, carbonyl, carboxyl, amino,
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sulfhydryl, phosphate etc. Additionally, there is relation between pKa and pH which can be
expressed by Henderson-Hasselbalch Equation -
pH= pKa + log ([conjugate base]/[weak acid]
pH= pKa + log ([A-]/[HA])
Now, the pH is sum of pKa value and log concentration of conjugate base divided by
weak acid (Liang, Shen and Guo, 2016). Then, at half equivalence point:
pH= pKa
Examples
Name Functional group pKa values
Benzoic acid Carboxylic acid 4.2
Phenol Hydroxyl group 9.8
Acetic acid Carboxylic acid 4.7
2b) Hydrophilic interaction Liquid Chromatography
The Hydrophilic interaction Liquid Chromatography (HILIC) can be described as
techniques which is most popular for ecdysteroid separations for both analytical and preparation
purposes. It is utilized to determine cholesterol and other sterols in foods as well as other tissues
extracts. Moreover, it is also become a method of choice for for separation and purification of
poly-peptides. Additionally, HILIC render an alternate formulation for separating efficaciously
tiny polar compounds on polar stationary forms. Meanwhile, reversed-phase high-performance
liquid chromatography (RP- HPLC) refers to process of separation of molecules on basis of
hydrophobicity. Thus, polar analytes display really contrasting selectivities under HILIC and RP-
LC situations (Mazza and Naegeli, 2016). For example, comparison of various properties of
stationery phases are used in separation of pyrimidines & purines which are polar compounds
and shows different selectivity on HILIC and RP- HPLC columns.
Examples of HILIC systems
Type of packing Mobile phase Detection Groups of detected
compounds
Polyhydroxyethyl A Salt gradient in TEAP UV-Vis Peptides, amino acids
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buffer with ACN
Luna NH2 Isocratic elution, (A)
ACN and (B) 13 mM
ammonium acetate
buffer, pH 9.1
Ion trap mass
spectrometry (MS)
Cancer biomarker in
urine (proteomics
approach)
3) Discuss four types of HILIC stationary phases
The HILIC needs a hydrophilic stationary phase for absorbing water which facilitate for
taking place of analyte partitioning process. Moreover, hydrophilicity provide support to column
packing material in order to make water layer thick that instantly impact on analyte retention. It
involves several HILIC stationary phases which contains ionic ligands bonded to silica surface.
However, utilization of ligands provide help of undergoing electrostatic fundamental interaction
that can add dimension to detachment at the time of analyzing ionizable compounds. Stationary
phases of HILIC are explained further -
Bare Silica – The bare silica phases are utilized to separate of small polar compounds
including carbohydrates, poly peptides and proteins. In this, silica has an acidic surface silanol
groups with pKa value of 3.5 which means that selected groups will become ionized and allow
silica phase for performing as cation ex-changer. Moreover, it will interact and remain positively
charged basic analytes.
Neutral Phases – This HILIC phase preponderantly consider polar functional groups
including amides, aspartamide, diol, cross-linked diol, cyano and cyclodextrin. However, pH of
these groups generally employed for mobile phases in their neutral form. Thus, it is used in
separation of monosaccharides, peptides, amino acids and small polar molecules.
Charged Phases – This phase involve utilization of functional group known as
aminopropyl. Meanwhile, primary group is positively charged and it shows advanced force of
anionic compounds such as amino acids, peptides, antibiotics, carboxylic acids & nucleosides.
Additionally, retention process is based on anion exchange and used in retention as well as
separation of neutral polar compounds (Taylor, 2012).
Zwitterion Phases – These HILIC phases are most versatile and remain primary
selection of column at the time of method evolution. Zwitterion phase involve permanently
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positive - quaternary ammonium or negative- sulfonic acid functional groups. However, it is
used to separate neutral, acidic and basic analytes, polar & hydrophilic compounds as well as
inorganic ions.
4) Separation of amphetamine
In case of separation of Amphetamine, there are two chromatograms which are given
with different chromatographic condition showing in the same. Chromatogram refers to a visible
record which showing results of separating the components of particular compounds of mixture
by chromatography. Moreover, it provides information about present elements along with their
amounts. Additionally, it indicates about accuracy in determining all available elements in
specific mixture with amount which results into peak shape, height and symmetry. Thus, there
are overall similar chromatographic conditions except one in figure 1A and 1B that is 'Mixture B'
contains 0.5% triethylamine while it is not analyzed in 'Mixture A'.
The figure 1B provides more accurate information about present elements in
Amphetamine rather then figure 1A so that separation of amphetamine is better in figure B in
terms of improved peak shape, height and symmetry.
5a) Retention times of analytes
The concentration of analytes are directly proportional to retention time duration because
if concentration increased then it boost up retention power of element and it takes more period of
time for remaining in the column of chromatography (Poole and Poole, 2012). However, in case
of give analytes A and B, retention time get increased while concentration of acetonitrile is
improved from 30% to 50%.
5b) Chromatographic parameters for increasing the retention time
The retention time can be described as specific duration which compound depends on
column after it has been injected to the same. If single chemical compounds contains different
elements then every single factor has differentiated time of retention and remain in column as per
their own properties. Moreover, retention time is calculated in units of seconds and minutes.
Chromatographic parameters which plays an important role equilibrium constant, polar or
non- polar stationary phases, boiling point, column temperature & length, carrier gas flow rate.
Thus, column temperature and length can be increased on which analyte B will be injected so
that retention time will get increased without affecting retention duration of analyte A.
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CONCLUSION
The above report conclude that end capping is utilized to determine every single element
from mixture and it has purpose to improve peak shape, reduce tailing, increase resolution and
selectivity. It include hydrophilic interaction liquid chromatography and its stationary categories
including Bare-Silica, Neutral-Phases, Charged-Phases and Zwitterion-Phases. Moreover, it
involve separation and retention time along with impacts of increased concentration on the same.
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REFERENCES
Books and journals
Castelletto V and et. al., Influence of end-capping on the self-assembly of model amyloid peptide
fragments. The Journal of Physical Chemistry B. 2011 Feb 10;115(9):2107-16.
Liang X, Shen A, Guo Z. Hydrophilic Interaction Liquid Chromatography. Analytical Separation
Science, 5 Volume Set. 2016 Feb 29;1.
Luo Z and et. al., Mesoporous silica nanoparticles end‐capped with collagen: redox‐responsive
nanoreservoirs for targeted drug delivery. Angewandte Chemie. 2011 Jan
17;123(3):666-9.
Mazza JC, Naegeli AH, inventors; Abbott Diabetes Care Inc, assignee. Analyte sensor retention
mechanism and methods of use. United States patent US 9,521,968. 2016 Dec 20.
Poole CF, Poole SK. Chromatography today. Elsevier; 2012 Dec 2.
Taylor LT. Packed column supercritical fluid chromatography of hydrophilic analytes via water-
rich modifiers. Journal of Chromatography A. 2012 Aug 10;1250:196-204.
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