| Use
of Native and Derivatized Cyclodextrin Chiral Stationary Phases for the
Enantioseparation of Aromatic and Aliphatic Sulfoxides by High Performance Liquid
Chromatography |
| C.Mitchell
/M.Desai /R.McCulla /W.Jenks /D.Armstrong /C.Mitchell /M.Desai /R.McCulla /W.Jenks
/D.Armstrong |
127 |
| The
enantioselectivity of native and derivatized cyclodextrin stationary phases for aromatic
and aliphatic chiral sulfoxides was evaluated using high performance liquid chromatography
HPLC). Many sulfoxide enantiomers could be baseline resolved using the derivatized
cyclodextrin stationary phases in the reverse phase mode.The most important factor
influencing enantioselectivity is the presence of steric bulk alpha to the chiral center.
However, substituents on an aromatic ring bonded to the sulfoxide have less pronounced
effects on enantioselectivity. The 2,3-dimethyl b-cyclodextrin exhibits the broadest enantioselectivity for neutral
chiral sulfoxides. Native cyclodextrins and hydroxypropyl-b-cyclodextrins were much less effective
in separating this class of molecules. The hydrogen bonding ability of the organic
modifier does not significantly affect enantioselectivity. |
|
| Rapid
Liquid Chromatographic-Mass Spectrometric Analysis of Withanolides in
Crude Plant Extracts by Use of a Monolithic Column |
| B.Kaufmann
/S.Souverain /S.Cherkaoui /P.Christen /J.-L.Veuthey |
137 |
| A rapid
analytical method has been developed for the mut ual resolution of thre steroidal
compounds, withaferin A, iochromolide, and withacnistin. Liquid chromatography was
performed on a Chromolith analytical column (4.6 mm i.d. x 50 mm), made from a cylindrical
silica rod, operated at a flow rate of 4 mL min-1 with a simple linear gradient
prepared from 0.1% aqueous formic acid and 0.1% formic acid in acetonitrile. Under optimum
conditions simultaneous separation of the compounds was achieved in less than 7 min, one
eighth the time required for conventional LC separation. The overall analysis time was
reduced without sacrificing chromatographic performance – essential for the
resolution of positional isomers such as iochromolide and withacnistin. The column was
coupled to a single-quadrupole mass spectrometer and the method was characterized by good
performance in terms of repeatability, selectivity, linearity, and sensitivity. Detection
limits in the single-ion-monitoring mode were 0.15 mg mL-1 or below. Finally, the developed method was
successfully applied to the determination of withanolides in extracts from Iochroma
gesnerioides obtained by three different processes – traditional Soxhlet extraction
and two faster methods, microwave-assisted extraction and pressurized solvent extraction. |
|
| Effect
of the Structure of Organic Phosphonate Compounds on Chiral Separations
on Derivatized Cellulose Chiral Stationary Phase |
| Guo-Sheng Yang
/Lan Zhou /Du Wei /Gao-Lan Li /P.Parrilla Vazquez /A.Garrido Frenich |
143 |
| The
enantiomers of eight O,O-dialkyl-2-benzyloxycarbonylaminoarylmethyl phosphonates
have been directly separated on a tris(3,5-dimethylphenylcarbamate)cellulose column. The
results are very different from those obtained by separation on an N-(3,5-dinitrobenzoyl)leucine
(DNBleu) column.The effect of mobile phase composition and column temperature on retention
and enantioselectivity were investigated. The effect on chiral separation of the length
of, and sterichindrance by alkoxyl groups of the phosphonate ester and of the nature of
the substituents p-Cl and p-H on the benzene ring attached to the
chiral carbon atom are also discussed. |
|
| Predictive
Quantitative Structure Retention Relationship Models for Ion-Exchange
Chromatography |
| C.B.Mazza
/C.E.Whitehead /C.M.Breneman /S.M.Cramer |
147 |
| A
database of probe molecules and their reported ion-exchange chromatographic data was
collected from the literature, after which an extensive set of both traditional and novel
molecular property descriptors were computed for each probe molecule. A genetic
algorithm/partial least squares (GA/PLS) approach was then used on the data to create a
predictive Quantitative Structure-Retention Relationship (QSRR) model of retention where a
subset of the original data was used for raining and the remainder of the data as a test
set. The utility of this model was demonstrated by using it to predict the chromatographic
behavior of compounds not included in the training set. The results presented in this
paper demonstrate the utility of modern QSRR modeling to predict chromatographic behavior
in ion-exchange systems. |
|
| Precolumn
Derivatization of Reducing Carbohydrates with
4-(3-Methyl-5-oxo-2-pyrazolin-1-yl) Benzoic Acid. Study of Reaction, High-Performance
Liquid Chromatographic Separation and Quantitative Performance of Method |
| C.B.Castells
/V.C.Arias /R.C.Castells |
153 |
| A simple
method for quantitative determination of carbohydrates by reversed-phase, high-performance
liquid chromatography after pre-column derivatization and UV detection has been developed.
Reducing sugars are condensed with 4-(3-methyl-5-oxo-2-pyrazolin-1-yl) benzoic acid (PMPA)
to yield UV adducts absorbing at 271 nm, which are resolved under typical reversed-phase
conditions. After derivatization, excess PMPA is easily removed from the reaction mixture
by precipitation with mineral acids at pH < 4. The influence of experimental conditions
on reaction yield, as well as chromatographic separation of derivatives, were
investigated. The quantitative performance was evaluated by means of a protocol comprising
replicate measurements at several analyte levels. The calibration curves obtained for 8
sugars showed excellent linearity over 10 – 5000 pmol. Limits of detection and
quantification for several monosaccharides were ca. 10 and 50 picomoles, respectively.
Optimized conditions were successfully used for quantitative determination of
monosaccharides released after hydrolysis from fetuin, mucin, a1-acid glycoprotein,
ovalbumin and transferrin. |
|
| Optimization
and Performance Evaluation of the Analysis of Glyphosate and AMPA in
Water by HPLC with Fluorescence Detection |
| B.Le Bot
/K.Colliaux /D.Pelle /C.Briens /R.Seux /M.Clément |
161 |
| The
object of this work was to optimize and validate an analytical method for the analysis of
glyphosate and its main metabolite AMPA (aminomethylphosphonic acid) in natural and
drinking water, for sanitary control. The method uses derivatization step which transforms
glyphosate and AMPA into fluorescent products by reaction with
9-fluorenylmethylchloroformate (FMOC-Cl). The kinetics and yield of this reaction were
studied by use of different samples. The derivatization products were injected directly
into the liquid chromatograph and separated on an amino-functionalized silica gel column.T
he performance of the method (detection limit, quantification limit, linearity, and
relative standard deviation) was studied and the results obtained showed the method was
suitable for routine analysis of glyphosate and AMPA. An interlaboratory test with five
laboratories confirmed that good results were obtained by use of this method. |
|
| Extraction
of Various Additives from Polystyrene and Their Subsequent
Analysis |
| S.H.Smith
/L.T.Taylor |
165 |
| The
extraction of fifteen polymer additives which are used as antioxidants, uv stabilizers,
process lubes, flame retardants, and antistats from eight formulations of polystyrene is
demonstrated with supercritical carbon dioxide and compared to traditional dissolut
ion/precipitation extractions. The purpose of the study was two fold:1) the development of
a high performance liquid chromatography method(s) for the additives and 2) the
determination of the viability of supercritical fluids for extract ion of the additives
from polystyrene. Nine of the additives were assayed via reversed phase liquid
chromatography while, the remaining six additives could not be assayed in this manner. In
order to develop an extraction method for the additives, the effects of static extraction
time, CO2 density,and temperature were first investigated. These preliminary
extract ions revealed that a static period which afforded an opportunity for the polymer
to swell combined with a high CO2 density and temperature above the polymer
glass transition yielded quantitative recoveries of the additives. Triplicate extractions
of the various polystyrene formulations matched additive recoveries obtained by the
traditional dissolution/precipitation method but the former method was faster and used
less organic solvent. |
|
| Determination
of Rutin and Forsythin in Fruit of Forsythia Suspensa (Thunb.)
Vahl by Capillary Electrophoresis-Electrochemical Detection |
| Xiangjun Li
/Yuping Zhang /Zhuobin Yuan |
171 |
| Capillary
electrophoresis-amperometric detection is evaluated for simultaneous determination of
rutin and forsythin. The cyclic voltammogram, ydrodynamic voltammogram, effect of pH,
buffer concentratrion and SDS, and percent organic modifier on separation and detection
were studied. Conditions were optimized as follows: 1.2 V detection potential; separation
at 12 kV; 5 s at 15 kV for sample injection time and sample injection voltage; mobile
phase 20 mM boric acid buffer; pH 8.4, containing 40 mM SDS and 10 % (v/v)
acetontrile.T he method gave low detection limit as 0.001 mg mL-1 and 0.0005 mg
mL-1 (S/N =3), wide linear range 0.005 – 0.5 mg mL-1 for rutin
and forsythin, respectively. The relative standard deviations of peak current and
migration time for 8 consecutive injections of the standard solution containing 0.1 mg mL-1
each compound were 4.78%, 3.63% and 6.40%, 2.95% for rutin and forsythin, respectively. In
addition, levels of the two compounds in traditional Chinese herbal drugs were easily
determined. |
|
| Ethylbenzene-Modified
Fused-Silica Columns for Capillary Electrophoresis |
| M.V.Russo |
175 |
| Coated
capillaries modified with a hydrocarbon layer have been developed. Modification of the
surface with ethylbenzene greatly improved the electrophoretic performance of the
capillaries. The column efficiency for basic organic compounds was as high as 378000
theoretical plates per meter on a 50 m i.d.ethylbenzene-surface-treated fused-silica
capillary column. This value did not change during 25 replicate analyses and the capillary
columns were very stable against continuous treatment for 30 h with buffer of pH 10 and
treatment for 3 h with HCl of pH 1 and NaOH of pH 12. The relative standard deviation of
run-to-run, day-to-day, and capillary-to-capillary for coating with the ethylbenzene layer
was < 2.6%, and reproducibility was good. The separation of four aromatic amines and
six pharmacological amines at pH 2.5 is reported. |
|
| Development
and Validation of a Gas Chromatographic Method for Analysis of Fosfomycin in Chicken Muscle Samples |
| A.Loste
/E.Hernández /M.A.Bregante /M.A.García /C.Solans |
181 |
| A gas
chromatographic method for the determination of residues of Fosfomycin in chicken muscle
samples has been developed. Muscle samples were homogenised with TRIS buffer, containing
phenylphosphonic acid (as internal standard) and Fosfomycin using a tissue homogenizer.
Afterwards, the samples were ultrafiltered and the ultrafiltrate was evaporated to
dryness. A silylation reagent for derivatization was used in order to reconstitute the
residue. The linear concentration range of application was 10 – 150 µg g -1,
with a detection and quantitation limit of 3.11 and 10 µg g -1, respectively.
The method was efficient with a mean recovery of 87.83% from spiked muscle. The results
obtained show that gas chromatography is a useful method for the determination of
Fosfomycin residues in chicken muscle samples. |
|
| Automated
Liner Exchange – A Novel Approach in Direct Thermal Desorption
– Gas Chromatography |
| J.A.de Koning
/P.Blokker /P.J ngel /G.Alkema /U.A.Th.Brinkman |
185 |
| A system
was developed for fully automated liner exchange in direct thermal desorption – gas
chromatography – mass spectrometry (DTD-GC-MS). Samples are put into a newly
developed liner which is capped with a standard crimp cap. The liners are placed in a
sample tray and transported to the thermal desorption device. Both liner transport and
liner exchange (which can be performed after each analysis) are automated. The system was
tested for spores and pollen, vegetable oil, wood (preservative), car exhaust (BTEX), and
tobacco (nicotine) analysis to demonstrate the robustness and flexibility of the
approach. |
|
| Determination
of Organochlorine Pesticides by Gas Chromatography with Solid-Phase
Microextraction |
| J.P.Pérez-Trujillo
/S.Frías /M.J.Sánchez /J.E.Conde /M.A.Rodríguez-Delgado |
191 |
| A study
of different extraction techniques for the determination of a selected group of
organochlorine compounds in surface waters is presented. Comparison of liquid-liquid
extraction (LLE) with solid-phase extraction (SPE) and solid-phase microextraction (SPME)
with fibers of different polarity shows that SPME with
a recently commercialised fiber of polydimethy siloxane divinylbenzene allows these
compounds to be determined in surface waters with good extraction efficiencies. Extraction
time, effect of temperature, ionic strength and pH were optimised, allowing quantification
in agricultural effluents in the range 1.0 – 60 ng L-1. |
|
| Chromatography-Mass
Spectrometry and Toxicity Evaluation of Selected Contaminants in
Seawater |
| M.Mezcua
/M.D.Hernando /L.Piedra /A.Agüera /A.R.Fernández-Alba |
199 |
| In the
present work a combined analytical study involving gas and liquid-chromatography and
toxicity studies were developed for the determination of various contaminants typically
present in sea water samples.T he compounds investigated were Diuron, Chlorothalonil,
Dichlofluanid, TCMTB (2-thiocyanomethylthiobenzothiazole), Irgarol 1051, Sea nine 211 and
MTBE (methyl-tert-butyl ether). The selected compounds are additives of boat paints and
gasoline and they can release into the aquatic environment in considerable amounts in
areas with intense shipping traffic. The developed analytical protocol consisted on the
use of a solid phase extraction procedure with Oasis HLB cartridges followed by
GC-EI/NCI-MS and LC-ES-MS both in SIM mode. Average recoveries, loading 600 mL of samples
with pH =3, varied from 40 to 95% and the detection limits ranged from 1 – 25 ng L-1.The
developed method was applied to real samples from various marinas of Andalusia (Spain).
Daphnia magna, Vibrio fischeri and Selenastrum capricornotum toxicity
bioassays on individual and mixtures of selected compounds were applied to evaluate EC50
(effective concentration) and LOEC (lowest observable effect concentration) values.
Resulting values were in the range of 0.001 – 720 mg L-1 for EC50
and 0.8 10 –9 – 30mg L-1 for LOEC for all contaminants
except for MTBE where no toxic effect were found up to 680 mg L-1 on Daphnia
magna. Toxicity effects of binary mixtures of the selected compound showed synergistic
effects in the majority of the cases (47.6%) and antagonistic in the lower of the cases
(9.5%). Levels of the contaminants found in the seawater samples showed around a 30% of
inhibition on tested species, during the summer months considering mixture Irgarol
1051-Diuron. Accelerated toxicity processes were observed in mixtures MTBE-Diuron and
MTBE-Dichlofluanid. |
|
| Capillary
Gas Chromatography Separation of Pyrethroic Acid Methyl Esters Using Four Acylated
Cyclodextrin Derivatives as Chiral Stationary Phases |
| X.Y.Shi /H.C.Guo
/M.Wang /S.R.Jiang |
207 |
| Four
cyclodextrin derivatives (CDs) were synthesized by substituting 3-OH of 2,6-di-O-pentyl-b-cyclodextrin with four
different chain lengths of acyl groups (butyryl, valeryl, heptanoyl, octanoyl). The
chromatographic properties of the four CD derivatives as stationary phases of capillary
gas chromatography (CGC) were investigated. These CDs exhibit a wide range of application.
Not only five pairs of enantiomers of pyrethroic acid methyl esters were separated on the
four CDs, but also some other racemic compounds. Among the four CDs, 2,6-di-O-pentyl-3-O-butyryl-b-CD possesses better enantiomer
separation abilities to the studied enantiomers of pyrethroic acid methyl esters than the
other studied CDs. The extension of chain length of the acyl groups in 3-position of CDs
cannot improve the enantiomer separation abilities of the CD derivatives. |
|
| Determination
of Bisphenol-A and Related Compounds in Human Saliva by Gas Chromatography – Mass
Spectrometry |
| A.Zafra /M.del
Olmo /R.Pulgar A.Navalón /J.L.Vílchez |
213 |
A simple
and sensitive method for the determination of trace amounts of bisphenol-A (BPA),
bisphenol-A diglycidyl dimethacrylate (bis-GMA), bisphenol-A dimethacrylate (bis-DMA) and
triethyleneglycol dimethacrylate (TEGDMA) in human saliva is
proposed. These materials are used in dental restorations, as composites and sealants, and
are sometimes detected in human saliva after dental treatment. The proposed method
involves protein precipitation using acetonitrile followed by acidification, evaporation
of the solvent and dissolution with dichloromethane prior to injection into a GC-MS.
Thermal derivatization in the injection system was used for the identification and
quantification of bis-GMA.Clean-up is not necessary using SIM mode. Bisphenol-F (BPF) was
used as internal standard. The linear range was 15 to 1000 mg L-1 for BPA, 50 to
10000 mg L-1
for bis-GMA, 50 to 1000 mg L-1 for bis-DMA and 1 to 100 mg L-1 for TEGDMA. The
detection limits were 3, 15, 10 and 0.3 mg L-1 for BPA, bis-GMA, bis-DMA and TEGDMA, respectively.
Validation of the proposed method was carried out by using the standard addition
methodology.
Samples of 10 mL of human saliva collected 1 h after dental treatment were analysed in
order to assess the applicability of the method to detect and quantify such compounds
originated from methacrylic resins used in odontological treatment. |
|
| Use
of a Database of Plots of Pesticide Retention (RF)
against Mobile-Phase Composition. Part I. Correlation of Pesticide Retention Data in
Normal- and Reversed-Phase Systems and their Use to Separate a Mixture of Ten Pesticides
by 2D TLC |
| T.Tuzimski
/E.Soczewinski |
219 |
| Ten
pesticides have been completely separated by two-dimensional (2D) development on TLC
plates coated with coupled layers of octadecyl silica (reversed-phase, RP) and plain
silica (normal-phase, NP). The binary mobile phases, aqueous-organic for RP chromatography
and non-aqueous for NP chromatography, were chosen from plotsRf against
mobile-phase composition and graphical RF(RP)-RF(NP)
correlations. The different selectivity of the RP and NP systems enabled dispersion of
spots over the plate area and good separation. |
|
| Use
of a Database of Plots of Pesticide Retention (RF)
against Mobile-Phase Composition. Part II. TLC as a Pilot Technique for Transferring
Retention Data to HPLC, and Use of the Data for Preliminary Fractionation of a Mixture of
Pesticides by Micropreparative Column Chromatography |
| T.Tuzimski
/E.Soczewinski |
225 |
| Relationships
between Rf values and mobile-phase composition have been determined for
moderately polar pesticides in normal-phase systems (NP) of the type silica-non-polar
diluent (heptane)-polar modifier (ethylacetate, tetrahydrofuran, or dioxane) and in
reversed-phase systems (RP) of the type octadecyl silica-water-polar modifier
(acetonitrile, methanol, or tetrahydrofuran). These relationships constitute a retention
database which has enabled choice of the optimum conditions for preparative column
chromatographic separation of pesticides into fractions; these were then applied to a
silica plate and chromatographed.T he plate was videoscanned, furnishing a real picture of
the plate showing complete separation of the pesticide fractions. |
|
| Optimization
of the Reversed-Phase High-Performance Liquid Chromatographic Separation
of the Enantiomers of a Cationic Chiral Drug (Tolperisone) on a Heptakis(6-Azido-6-deoxy)
Perphenylcarbamated b-Cyclodextrin Column |
| T.Velmurugan
/C.B.Ching /S.C.Ng /Z.W.Bai /T.T.Ong |
229 |
| Heptakis(6-azido-6-deoxy)
perphenylcarbamated b-cyclodextrin has been synthesized and chemically immobilized on silica gel
for use as a chiral stationary phase (PC-CSP) for analytical separation of the enantiomers
of chiral drugs. Separation of the enantiomers of tolperisone was studied by
high-performance liquid chromatography under reversed-phase conditions. The
chromatographic conditions were optimized by varying mobile phase pH, composition, ionic
strength, and velocity; 40:60 methanol - 1% triethylammonium acetate (TEAA) buffer, pH
5.5, was found to be the most suitable for this separation. |
|
| Direct
Separation of the Enantiomers of Cetirizine and Related Compounds by
Reversed-Phase Chiral HPLC |
| Q.Liu /Z.Zhang
/H.Bo /R.A.Sheldon |
233 |
| Direct
separations of the enantiomers of cetirizine and related compounds have been achieved
byreversed-phase HPLC on the Chiralcel OD-R, polysaccharide-derived chiral
stationaryphase; the mobile phase was usually perchlorate solution supplemented with
acetonitrile. Resolution of the enantiomers of cetirizine and related compounds was good.
The effect of the acetonitrile content of the mobile phase was investigated, and the
effect of the structure of the chiral compounds on their behavior on the Chiralcel OD-R
column is discussed. |
|
| Selective
Solid Phase Extraction of a Drug Lead Compound Using Molecularly
Imprinted Polymers Prepared by the Target Analogue Approach |
| B.Dirion /F.Lanza
/B.Sellergren /C.Chassaing /R.Venn /C.Berggren |
237 |
| Molecularly
imprinted polymers have been evaluated at the sample clean-up stage in the analysis of a
drug lead compound. In order to circumvent quantification problems related to bleeding of
the template, a structurally related analogue of the latter was used. This was selected
based on criteria related to interaction site location, solubility, availability and
stability of the analogue. Selection of suitable polymerisation conditions was then made
using a small batch format (ca. 50 mg) and rapid assessment of binding in the equilibrium
mode. It was found that the amount of template could be greatly reduced compared to the
conventional protocol, requiring only 5 µmol of template per gram of polymer without
seriously compromising the performance of the materials for chromatographic or SPE
applications. |