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Current Pharmaceutical
Analysis
ISSN: 1573-4129
Current Pharmaceutical
Analysis
Volume 3, Number 4, November 2007
Contents
Chromatographic Performance of Silica-Based Stationary
Phases in High Temperature Liquid Chromatography: Pharmaceutical
Applications Pp. 221-229
Davy Guillarme, Rossana Russo, Serge Rudaz, Carlo Bicchi
and Jean-Luc Veuthey
[Abstract]
New Trends in Analysis of Biopharmaceutical Products
Pp. 230-248
Alexis Oliva, José B. Fariña and Matías
Llabrés
[Abstract]
Sequential-Injection Analysis: A Useful Tool for Clinical
and Biochemical Analysis Pp. 249-261
Anastasios Economou, Paraskevas D. Tzanavaras and Demetrius
G. Themelis
[Abstract]
Novel Metformin Carbon Paste and PVC Electrodes
Pp. 262-267
Elmorsy Khaled, Hassan N.A. Hassan, Manal S. Kamel and
Barsoum N. Barsoum
[Abstract]
Comparative Study of the Derivative and Partial Least
Squares Methods Applied to the Spectrophotometric Simultaneous
Determination of Atorvastatin and Amlodipine from their Combined
Drug Products Pp. 268-272
Siavash Riahi, Mohammad R. Ganjali, Eslam Pourbasheer
and Parviz Norouzi
[Abstract]
Development and Validation of TLC-Densitometric Method
for Resolution and Determination of Enantiomeric Purity of
Ropivacaine, Using Different Cyclodextrins as Chiral Selector
Pp. 273-277
Elham A. Taha
[Abstract]
Abstracts
[Back to top]
Chromatographic Performance of Silica-Based
Stationary Phases in High Temperature Liquid Chromatography:
Pharmaceutical Applications Pp. 221-229
Davy Guillarme, Rossana Russo, Serge Rudaz, Carlo Bicchi
and Jean-Luc Veuthey
High temperature liquid chromatography is currently well established
in separation sciences. The decrease of mobile phase viscosity
with temperature provides fast separations with high efficiency,
limiting excessive backpressure. Furthermore, the water polarity
decreases with temperature allowing a reduction of the organic
modifier content in the mobile phase. These advantages are
already observed for temperature below 100°C.
Recently, the commercialization of dedicated instrumentation
for preheating and cooling the mobile phase, and of new stationary
phases stable at high temperature containing carbon, zirconia,
titania or polymeric material, allows a routine use of high
temperature liquid chromatography (HTLC). The latter stationary
phases could however exhibit high retentions and different
selectivity in comparison with the traditional silica-based
columns. Therefore, embedded, hybrid or new silica-based stationary
phases, possessing similar chromatographic behaviour and good
thermal resistance at temperatures as high as 100°C, are
often selected.
Kinetic, stability and chromatographic performance of a silica-based
stationary phase (Zorbax Stable Bond) were evaluated up to
a temperature of 120°C. This chromatographic support was
successfully used for separating numerous drugs at ambient
and high temperatures. Improvements of performance due to
temperature increase were reported, such as the decrease in
analysis time (separations in only few seconds) and the peak
shape improvements (higher efficiency and lower asymmetry).
Furthermore, several modifications of selectivity and the
possibility to use a lower content of organic modifier into
the mobile phase were demonstrated.
[Back to top]
New Trends in Analysis of Biopharmaceutical Products
Alexis Oliva, José B. Fariña and Matías
Llabrés
Protein and peptides production through recombinant techniques
has benefited from numerous years of successful research,
and is widely accepted as the approach of choice. As a result
of these advances, many peptides and proteins are being formulated
as bio-pharmaceuticals; however, to develop these macromolecules
into stable formulations still remains a great challenge.
Formulation problems in solution arise from the complex native
structure of these macromolecules and are often manifested
as physical instability, e.g. unfolding, aggregation, and/or
precipitation. Understanding these effects is fundamental
for research, development, production, and quality control.
A variety of different techniques including HPLC, SEC, native
gel electrophoresis and other electrophoretic techniques,
analytical ultracentrifugation, fluorescence spectroscopy,
Fourier transform/IR spectroscopy, mass spectrometry, light
scattering, membrane osmometry, and UV spectroscopy have been
used to study these processes.
The assessment of product quality i.e. identity, content and
purity has a major role in the manufacturing process of biopharmaceuticals.
The biotechnological production process itself usually shows
high variability, which introduces high product diversity.
Even from production batches, only limited amounts of material
may finally be approved for use and made available, requiring
sensitive analytical technology. The purpose of the current
review is to describe and discuss the latest advances in analytical
methodologies used to secure final product quality.
[Back to top]
Sequential-Injection Analysis: A Useful Tool for Clinical
and Biochemical Analysis
Anastasios Economou, Paraskevas D. Tzanavaras and Demetrius
G. Themelis
Sequential-injection analysis (SIA) is a sample handling and
manipulation technique developed to address some limitations
of traditional on-line analysis approaches, mainly flow-injection
analysis (FIA). The heart of a SIA manifold is a multi-position
selection valve. The common port of this valve is connected
to a so-called “holding coil” (essentially a long
piece of coiled tubing) while the selection ports of the valve
can be connected to various flow-through modules. The sample
to be analyzed is initially aspirated and stored in the holding
coil and can be further serially processed by directing it
to appropriate modules in which both physical manipulation
and/or chemical transformations may take place. SIA has found
numerous applications in the field of clinical and bio-analytical
chemistry by exploiting its potential as a sample-handling
and manipulation technique. This review will cover the most
significant applications of SIA in this area including on-line
dilution/mixing, liquid and solid-phase extraction and pre-concentration,
immunoassays, enzymatic methods, coupling to separation modules,
miniaturization and other approaches for the determination
of compounds with biological and clinical significance.
[Back to top]
Novel Metformin Carbon Paste and PVC Electrodes
Elmorsy Khaled, Hassan N.A. Hassan, Manal S. Kamel and
Barsoum N. Barsoum
Two metformin carbon paste and PVC electrodes are proposed
for the determination of metformin. Different methods for
electrode fabrication (including formation of the ion pair
in situ, soaking of the electrode in the ion pair aqueous
solution, in addition to the classical modification of the
electrode matrix with the ion pair) are described for both
carbon paste and PVC electrodes. Electrodes based on in situ
ion pairs of metformin with sodium tetrakis (4-fluorophenyl)
borate or tungstophosphoric acid respectively showed the best
performance compared with the other methods of preparation.
These electrodes exhibit a linear response with a good Nernstian
slope over a concentration range 10-5-10-1
M of metformin in a working pH range between 4 and 8. The
effect of the electrode matrix composition and plasticizer
on the performance of both carbon paste and PVC electrodes
are investigated for each fabrication method. The proposed
technique was applied successfully for the determination of
metformin in pure solutions and in dosage forms with good
accuracy and precision. The results were compared statistically
with those given by the reported method.
[Back to top]
Comparative Study of the Derivative and Partial Least
Squares Methods Applied to the Spectrophotometric Simultaneous
Determination of Atorvastatin and Amlodipine from their Combined
Drug Products
Siavash Riahi, Mohammad R. Ganjali, Eslam Pourbasheer
and Parviz Norouzi
The simultaneous spectrophotometric determination of Atorvastatin
calcium (ATV) and Amlodipine besylate (AML) in tablets in
the presence of the overlapping spectra was accomplished with
the derivative spectrophotometry (DS) and the partial least
squares (PLS) approaches without using any chemical pre-treatment.
In this study, the concentration model was based on the absorption
spectra in the range of 220-400 nm for 25 different mixtures
of ATV and AML. The calibration curve was linear over the
concentration range of 10-160 and 3-33 μg
mL-1 for ATV and AML, respectively.
These two methods were tested by analyzing the synthetic mixtures
of the above drugs and they were applied to the real samples,
containing two commercial pharmaceutical preparations of the
subjected drugs. A comparative study was carried out using
the experimental results obtained from the two analytical
methodologies. The root mean squares differences (RMSD) with
PLS and DS were 0.6618 and 1.2555 for ATV and 0.1589 and 0.3490
for AML, respectively. It should also be mentioned that the
accuracy of the PLS method was better than that of DS.
[Back to top]
Development and Validation of TLC-Densitometric Method
for Resolution and Determination of Enantiomeric Purity of
Ropivacaine, Using Different Cyclodextrins as Chiral Selector
Elham A. Taha
A novel economic procedure for stereoselective separation
and determination of R(+) - and S(-)- ropivacaine was described
using different thin layer chromatographic plates and different
cyclodextrins at different temperatures. The spots were detected
either with iodine vapors or UV lamp 254nm, followed by densitometric
measurements at 262nm. Comparative study was achieved using
different cyclodextrins namely, hydroxypropyl-β-cyclodextrin
(HP-β-CD),
methyl-β-cyclodextrin
(M-β-CD),
and Dimethyl-β-Cyclodextrin
(DM-β-CD)
as chiral selectors. The mobile phase enabling successful
resolution of (±) ropivacaine was acetonitrile: water
(17:3 v/v) containing 1mM of DM-β-CD
at ambient temperature 25±20C.
All variables affecting the resolution, such as concentration
of different chiral selectors, temperature, and pH were investigated
and the conditions were optimized. The procedure provided
a linear response over the concentration range of 1.25 - 35
μg/spot
for determination of R (+)- and S- (-)enantiomers (r = 0.9998,
n = 8), (r = 0.9998, n = 6) with acceptable precision (% RSD
<1.5) and accuracy (% RE= -1.18 to 2.00). Limits of detection
and quantification were found to be 0.29μg/spot
and 0.96 μg/spot
for -(R) and 0.26μg/spot
and 0.86µg/spot for -(S) respectively. The developed
method was validated and proved to be robust. Ropivacaine
sample solution was found to be stable for one weak in methanol.
The proposed method was found to be selective and accurate
for identification and quantitative determination of enantiomeric
purity of ropivacaine in bulk powder and pharmaceutical dosage
form.
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