In The Name Of God

Mohammad Javad Hosseinishahi

Solid-Phase Microextraction in Targeted and Nontargeted Analysis:

Displacement and Desorption EffectsSanja Risticevic and Janusz Pawliszyn

Supervisor: Dr.M.Saraji

Introduction Experimental section

Results and discussionConclusionsReference

This nonexhaustive and environmentally friendly technique integrates sampling, extraction, concentration, and sample introduction into a simple solvent-free procedureSPME involves the use of a fibre coated with an extracting phase, that can be a liquid (Polymer) or a solid (Sorbent)

Solid-phase microextraction (SPME) was introduced in 1990

After extraction, the SPME fibre is transferred to the injection port of separating instruments, such as a GC

Introduction

volume of the extraction phase

the extracted amount at equilibrium

fiber coating/sample matrix distribution constant of the analyte

Initial concentration of analyte in the sample

Introduction

volume of the extraction phase

fiber constant

fiber coating/sample matrix distribution constant of the analyte

Introduction

A) Chemicals and Materials

B) Sample Preparation

C) SPME Procedure

D) Instrument

Experimental section

The automated SPME holder and10 and 20 mL screw cap vials were purchased from Supelco

HPLC-grade methanol and acetone

Analyte standards were all of >97% purity (except for >95% purity for heptanal, nonanal, citral

isomers, farnesol isomers, dodecanal, tridecanal, and linalool)

Commercial SPME fiber assemblies in 23-gauge needle sizes and automated formats (100 μm PDMS), 85

μm (PA), 60 μm (CW) [metal], 65 μm PDMS/ (DVB), 85 μm (CAR)/PDMS, 50/30 μm DVB/CAR/PDMS,

and 16 μm of Carbopack Z/PDMS [metal]) were obtained from Supelco

Chemicals and Materials

250 ml NaCl

250 ml Water

100 g of apple tissue

Sample Preparation3ml

SPME Procedure

The aqueous extraction standards and apple samples were analyzed fresh by HS-SPME at 30 °C using a 500 rpm agitation speed and 60 min extraction time

t test was used to determine whether extraction equilibrium was reached for a particular component.

To compare DVB/CAR/PDMS and PDMS/DVB coatings interms of extraction kinetics and desorption efficiency, extraction time profiles were performed with 5, 30, 60, and 120 min points .

Interanalyte displacements were examined by analyzing aqueous calibration standards with 30 and 60 min extraction times and apple samples with 1, 5, 15, 30, 60, 120, and 180 min extraction times. All samples were analyzed at 30 °C

Instrumental

GC × GC/ToFMS

Primary dimension columns employed

Secondary dimension columns employed

Details:

)30 m × 0.25 mm i.d. × 0.25 μm(

(1.15 m × 0.10 mm i.d. × 0.10 μm)

A) Trends in Coating Selectivity and SensitivityB) Desorption Efficiency of Commercial CoatingsC) Determination of the Linear Dynamic Range and Interanalyte Displacements

Results and Discussions

PDMS, PDMS/DVB, and DVB/CAR/PDMS coatings extracted all of the investigated metabolites

Trends in Coating Selectivity and Sensitivity

PDMS/DVBDVB/CAR/PDMS

while only 47, 50, 44 and 39 peaks were extracted with PA, CAR/PDMS, CW, andCarbopack Z/PDMS coatings, respectively

PACAR/PDMSCWCarbopack Z/PDMS

Some nonpolar components such as: a) octane b) nonane

Moderately polar such as:a) 2-hexanoneb) Hexanalc) ethyl butanoate

Not detected

CW Nonpolar analytes octane to undecane

Moderately polar Analytes such as:a) 2-hexanone b) Hexanalc) ethylbutanoated) α-pinenee) eucalyptol

Not detected

Carbopack Z/PDMS

This extraction phase was found to be unsuitable for the extraction of small molecular weight analytes

Pore size is 100 Å

Fiber constants are reported for PDMS, PA, DVB/CAR/PDMS, and PDMS/DVB coatings, since the implementation of these coatings in spiked water analysis resulted insatisfactory reproducibility.

In the worst-case scenario, for the PA coating, RSD ranged from 0.9% for linalool to 25.4% for ethyl stearate

This result is attributed to the difference in the average sizes of the micropore diameter between Carboxen 1006 in DVB/CAR/PDMS and CAR/PDMS coatings and DVB in PDMS/DVB and DVB/CAR/PDMS coatings (12 and 16 Å, respectively).

The trends in extraction efficiencies obtained with PDMS/DVB and CAR/PDMS coatings are also illustrated in Figure

Contour plots of extracted ion chromatograms (the x- and y-axes represent the retention times in the first and second dimensions) corresponding to 60 min HS-SPME extraction of an aqueous sample spiked with 52 metabolites and obtained with (A) PDMS/DVB and (B) CAR/PDMS coatings.

S1 TablePage 2 - 3

Likewise, since the ability of an adsorbent to extract a particular analyte is strongly dependent on the average size of the micropore diameter, KfsVf improvements of 11-fold for 2-pentanol and 4-fold for α-pinene, 1-pentanol, e2-hexanone, and 2-hexanol were detected when DVB /CAR /PDMS was compared to PDMS/DVB

A – < 100 g/molB – between 100 and 120 g/mol

C – between 180 and 215 g/mol

The largest improvement in extraction sensitivity was achieved with DVB /CAR /PDMS for analytes having molecular weights of <185 g/mol.

Above this molecular weight threshold, the performance of the two coatings was similar across the hydrophobicity and volatility range

PDMS/DVB performed slightly better only for the latest eluting members of each homologous series.

Desorption Efficiency of Commercial Coatings

Memory Effect For DVB /CAR /PDMS

& CAR/PDSM

Desorption Efficiency of Commercial Coatings

5, 30, 60 and 120 min extraction A – 1-nonanol, B – 1-undecanol, C – 1-pentadecanol and D-1-heptadecanol

Determination of linear dynamic range (LDR, 9-point calibration curve, each point run in triplicates) and method repeatability for actual spiked metabolite concentrations employed in coating evaluation study for experimental design involving DVB/CAR/PDMS coating and 60 min HS-SPME extraction

S3 TablePage 15-16

Determination of the Linear Dynamic Range and Interanalyte Displacements

Figure 2. SPME calibration curves for 2-pentanol (A; 60 and 30 min extraction times employed) and 2-heptadecanone (B) for aqueous samples spiked with 52 metabolites and analyzed with DVB /CAR /PDMS fiber coating at 30 °C

Extraction time (1−180 min) uptakes of major components in the apple matrix exhibiting high HS-SPME sensitivity and selectivity: (A) ethyl butanoate, (B) ethyl 2-methylbutanoate, (C) hexyl hexanoate.

DVB/CAR/PDMS extraction time profiles of nonane (plot A), nonanal (plot B) and 1-nonanol (plot C)

HS-SPME extraction time profiles of representative low S/N and low KfsVf polar compounds in the apple matrix: (A) (2Z)-2-penten-1-ol and (B) (3Z)-3-hexen-1-ol

HS-SPME extraction time profiles of selected compounds in apple homogenate for which the occurrence of interanalyte displacement was detected: (A) 1-methoxybutane, (B) 2-methylpropanol

HS-SPME extraction time profiles of selected compounds in apple homogenate for which the occurrence of interanalyte displacement wasdetected: (A) 1-methoxybutane, (B) 2-methylpropanol

Conclusions

The wide volatility, hydrophobicity, polarity, and molecular weight ranges of compounds considered in this systematic study allowed for a comprehensive evaluation of performance characteristics of commercially available SPME−GC fiber coatings in terms of extraction sensitivity, desorption efficiency, and feasibility in complex sample analysis

The investigation of complex mixtures with DVB/CAR/PDMS revealed that interanalyte displacements are infrequent.

the results obtained in this study clearly demonstrate that nonpolar high Henry’s constant compounds that have high Kfs are not displaced

The only analytes that were affected by interanalyte competition for adsorption sites included small molecular weight and early-eluting compounds with medium to high polarity and low fiber constants

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Thanks a lot for attention

In The Name Of God

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