emerging hyphenated and comprehensive multi-dimensional … · 2020. 6. 13. · 23478-pecdf pcdd/f...

Emerging Hyphenated and Comprehensive Multi-Dimensional Techniques for the Measurement of

POPs in Food

J.-F. Focant

Mass Spectrometry LaboratoryBiological and Organic Analytical Chemistry

Persistent Organic Pollutants

9 agrochemicals:-Aldrin -Chlordane-DDT -Dieldrin-Endrin -Heptachlor-HCB -Mirex-Toxaphene

3 industrial substances:-PCBs-PCDDs-PCDFs

Target Analytes2,3,7,8-substituted PCDDs (7)2,3,7,8-substituted PCDFs (10)Non-ortho PCBs (4)Mono-ortho PCBs (8)EU marker ‘Tracer’ PCBs (6)‘Biomonitoring’ PCBs (30)Selected OCPs (12)Selected PBDEs ? (8)

… Σ = 80+

Contributors to human intake

FishMeatMilk

PCDD/Fs + NO-PCBs

35 %32 %

Target Matrices

Animal feedingstuffsHuman specimen

Belgium 2001 (Focant et al., 2002)

EU Directive 1881/2006 ECEU Directive 1883/2006 EC EURACHEM Guide ‘The fitness for purpose of analytical methods’

QA/QC Guidelines

Requirements for analytical procedures:-Sensitivity (LOQs) -Selectivity-Accuracy -Trueness-Robustness -13C-labeled IS-Recovery rates -Separation: ’should be sufficient’

Requirements for analytical procedures– High sensitivity: low MDLs– High selectivity: distinction for PCDDs, PCDFs and

DL-PCBs from co-extracted and interfering compounds

– High accuracy: provide a valid estimate of the true concentration

– Trueness: +/- 20 % and CV< 15%– 13C-labeled IS: addition of PCDD/F and DL-PCB– Recovery rates: 60-120 % (30 - 140 %)– GC separation: “should be sufficient”– Lower - Upperbound: 20 % difference (in the

range of 1 pg/g fat for food)

EU Directive 1883/2006 EC

The Dream

Time Cost Problems

0€101h

Sample

Congener-specific Results

Dreams Sometimes Come True

1970’s

Area of EffortsReducing manual handlingIncreasing sample throughput (# analytes)Increasing analytical speedDecreasing blank levels (improve LOQs)Get a better position in The Triangle

Speed(Low cost)

Selectivity

Sensitivity

POP Analysis SkeletonLLE, Soxhlet, SFE, MAE, SPME,SPE, MSPD, SBSE, PLE, …Extraction

Prep. LC (Silica), HPLC, SEC (GPC), …

Florisil, Alumina, Carbon, PYE, …

GC, GC-GC, GCxGC, …

Sector HRMS, QISTMSn, TOFMS, µECD,EIAs, RBAs, …

Clean-up

Fractionation

Separation

Measurement

Coupling (Instrumental)SPME-GC-MS SBSE-GC-MSSFE-GC-MS

Limited efficiencyfor Dioxins

SPE(or PLE)-Prep.LC-GC-IDMS(or RBA)

Liquids Solids SilicaAluminaCarbon

Automated

ECF Integrated Approach

Time Cost Problems

0.5€4000.5dayGC-MS

AutomatedSPE or PLE

Automated MCLCClean-up System

Samples

Batches of 5-10 samples

Fluid Samples

Sample homogenisation

Spiking, proteins precipitation, ...

SPE (C18) extraction

Side ‘lipid percent’ determination

Clean-up

Reverse Phase

Non-polar phase (C18)Polar solvent (MeOH, …)

Selective retention of the analytes

SPE SchematicSolvated bonded silica

O OH O

C18 C18

Solvated bonded silica

O OH O

C18 C18

PumpGauge

Nitrogentank

Silica

Aqueous waste

1 2 3 4

Sample

1. Hexane2. Hexane-Dichloromethane (1:1)3. Ethyl acetate-Toluene (1:1)4. Toluene

1 2 3 4

1. Water2. Acetonitrile3. Hexane-Dichloromethane (1:1)4. Air

Carbon

Organic waste

1. PCDD/Fs & cPCBs

ECF Integrated System (liquids)

GC-MSIn parallel, 2 h/batch

Extractfor GC-MS

2,3,7,

8 TCDD

1,2,3,

7,8 PeC

,3,4,7

,8 HxC

1,2,3,

2,3,7,

8 TCDF

1,2,3,

7,8 PeC

,4,7,8

1,2,3,

2,3,4,

SoxhletManual SPEIntegrated SPE

Accuracy (milk CRM)

Serum QC Chart

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Run number

PCDD/FsManual SPEIntegrated SPE

(semi)Solid Samples

Sample homogenisation (liquid N2)

Freeze-drying (overnight)

Grinding

Spiking, PLE extraction

Side ‘lipid percent’ determination

Clean-up

Pressurized Liquid Extraction

Na2SO4

Cryo-homogenizationDrying (lyoph, …)120°C, 1500 psiHexane (others)Static and/or dynamic

10-30 min/sample

Na2SO4

PLE Options Z Fat retainer (H2SO4-Si)

Several groups reported the use of H2SO4-Si to remove part of the lipids directly inside the extraction cell.

BUT:- Restricted to few extraction solvents- H2SO4-Si very ‘strong’ in conditions

like 120°C/1500 psi

100ml &nitrogen

On-lineevaporation

20mlsharp pulse

ECF Integrated System (solids)

In parallel, 1.5 h/batch (5-10)

CARP-1 CRM

PCDD/F concentrations

I-PCB concentrations0

2,3,7,

,3,7,8

,3,4,7

,8-HxC

,3,6,7

,8-HxC

,3,7,8

,9-HxC

,3,4,6

,7,8-HpC

OCDD2,3

,7,8-T

1,2,3,

ReferenceMeasured n=2

100000

120000

140000

160000

180000

200000

PCB 52

PCB 101/90

PCB 105

PCB 118PCB 138

/163/16

PCB 153

PCB 180

fwReferenceMeasured n=2(Sample size = 4g)

Referen

SUM PCDD/Fs 13.3 12.6 -5.3SUM PCBs 60.3 66.2 9.8SUM PCDD/Fs+PCBs 73.6 78.8 7.1pgTEQ/g f.w.

How to Measure ?SPE(or PLE)-Prep.LC ??

Liquids Solids Si, Al, C

On-line and Automated

One needs extra dimensionsChromatography, Spectroscopy, …

GC & MS

Sample Dimensionality System Dimensionality

Reference Method(HR)GC-IDHRMS ISO-17025 PTV-LVI-GC-IDQISTMS/MS alternative method

Thermo MAT95 XP Micromass AuSpec Ultima

Could we better match sample dimensionality ?

Separate injectionsDifferent GC phases- PCDD/Fs [RTX-5MS] - PCBs [HT-8]- PBDEs [STX-500]

Thermo Polaris Q

Dimensionality

GC-µECD

GCxGC-µECDGCxGC-TOFMS

Comprehensive two-dimensionnal gas chromatography

Peak capacity enhancer

“Two-dimensional (2D) separations are those techniques in which a sample is subject to two independent (orthogonal) displacement processes”

J. C. Giddings, Anal. Chem. 56 (1984) 1258A-1270A.

Definition of ‘Two-dimensional’

Definition of ‘Comprehensive’

A two-dimensional separation can be called comprehensive if:

1. Every part of the sample is subjected to two independent separative displacements.

Orthogonality rule

2. The separation (resolution) obtained in the first dimension is preserved throughout the process.

Conservation rule

Orthogonality Rule

VolatilityPolarity

Conservation Rule

Peak capacity = = 50 peaks

Classical GC

… …

Injector Detector

30m x 0.25mm x 0.25µm

Injector

1st dimension 2nd dimension

Detector

Column 1 Column 230m x 0.25mm x 0.25µm 2m x 0.25mm x 0.25µm

GCxGC (2 columns)… …

1D = 30 m2D = 2 m

Peak capacity = 1Dnc x 2Dnc= 50 x 19 = 950 peaks

[tTOT GCxGC = tTOT classical GC]

Splitless

1D RTX-500 40m0.18mm ID x 0.11µm df

2D BPX-50 1.5m0.10mm ID x 0.10µm df

LN2-Quad-jetsModulator

1TtR ~ 50 min

PM = 4 sec

Instrumental Setup

Injector

1st dimension

LN2 supplier

Trapping

Detector

1st Oven

2nd dimension2nd Oven

Detector

1st dimension

LN2 supplier

Releasing

1st Oven

Injector

1st dimension

LN2 supplier

Refocusing

Detector

1st Oven

Injector

1st dimension

LN2 supplier

Injection into second dimension

Detector

1st Oven

Injector

2nd Oven

Modulator

Modulation ProcessSampling rate 0.25 Hz

1st Dim tR

2nd Dim tR

4 seconds

Each ‘ slice ’ is a separate seconddimension chromatogram

Signal at the Detector

Signal4 sec

Time15222

Displaying the Data

Contour Plot

2nd Dim tR (4 sec)

1st Dim tR

Signal

3D Plot

1st Dim tR

2nd Dim tR

Contour Plot

1st Dim tR

2nd Dim tR

Why TOFMS ?

ScanningMS

Full Scan

–Comprehensive mass analysis–Slow

–Selective mass analysis–Fast

TOFNon-scanningMS

–Comprehensive mass analysis–Fast

(HRMS, QISTLRMS²)

Simultaneous samplingIon ratio remains constant across peaksSpectral continuity

Deconvolution

Specific Identification

Brunnée, Int. J. Mass Spectrom. (1987) 76 (2) 125.

Ideal Mass Analyzer ?

Time Compression

10 scans/s

TOF up to 500 scans per sec Scanning quad 2-5 scans per sec...

200 scans/s

200 ms peak

Coelution Solving Power

GCxGC TOFMS

Coelution

Peak capacity Deconvolution

Separation

Chromatographicresolution

Analyticalresolution

Symbiotic Relation

- TOFMS is the detector of choice to describe narrow 2D GCxGC peaks

- GCxGC zone compression enhances TOFMSsensitivity

Comprehensive Multidimensionality

1st Dim.GC

2nd Dim.GC

3rd Dim.TOFMS

ThermalModulation

IonisationModulation

Volatility Polarity Mass

OrthogonalityMinutes Seconds MilisecondsTime

PCDD/PCDFs and Planar-PCBs

1tR (s)CB-80

CB-126

CB-169

12378-PeCDD

12378-PeCDF23478-PeCDF

123478-HxCDF

123678-HxCDF

234678-HxCDF

123789-HxCDF

123478-HxCDD

123678-HxCDD123789-HxCDD

1234678-HpCDF

1234789-HpCDF

1234678-HpCDD

2378-TCDF

2378-TCDD

1234-TCDD

2tR (s)

WHO and Tracer PCBs

2tR (s)

1tR (s)

CB-123

CB-118

CB-114

CB-105

CB-167

CB-156CB-157

CB-189

CB-170

CB-101

CB-153

CB-138 CB-180

2000 4000 6000 80000

C12H9ClC12H9ClC12H8Cl2C12H8Cl2

C12H7Cl3C12H7Cl3C12H6Cl4C12H6Cl4

C12H5Cl5C12H5Cl5

C12H4Cl6C12H4Cl6

C12H3Cl7C12H3Cl7

C12H2Cl8C12H2Cl8

C12HCl9C12HCl9

209 PCBs (HT-8/BPX-50 Set)

C12Cl10

1tR (s)

2tR (s)

196 congeners separatedin 150 min

The 3 Dimensions are Needed2Intensity

CB-132

CB-179

CB-1612IntensityIntensity

CB-132

CB-179

CB-161

CB-161CB-179

CB-132

2tRCB-161CB-179

CB-132

CB-161CB-179

CB-132

1tR1tR

Isotope Dilution (13C12-Labels)Area = 1+2+3+4 (12C & 13C)

NativeLabeled

23478-PeCDF

PCDD/F Calibration

Standard Area Certified Calculated Response Expected Calculated Ion Ratio Concentration Concentration Factor Ion Ratio Ion Ratio Result

CDC-07:1 6078 5 4.8 0.97 0.654 0.615 PassedCDC-08:1 9121 7.5 7.5 1.01 0.654 0.643 PassedCDC-06:1 3005 2 2.0 1.01 0.654 0.717 PassedCDC-05:1 1420 1 1.0 0.98 0.654 0.663 PassedCDC-04:1 218 0.5 0.5 0.99 0.654 0.612 PassedCDC-03:1 379 0.2 0.3 1.59 0.654 0.649 Passed

0.20 pg 12C-2,3,7,8-TCDF

50 pg 13C-2,3,7,8-TCDF

Sensitivity

1 µl injected SL

Quan S/N = 10Area = 350

Quality Control Charts

BDE-47

BDE-100

CB-153

‘Cleaned’ Fish Extract

CB-80 recovery std (0.5 ng)

Tracer PCBs in Fish

1.5g sample sizeRSD GCxGC-TOFMS: 1-14%RSD GC-HRMS: 3-5%RSD GC-MS/MS: 2-5%

TriCB-28 TeCB-52 PeCB-101 HxCB-138 HxCB-153 HpCB-180

GCxGC-TOFMSGC-HRMSGC-MS/MS

Non- and Mono-ortho PCBs in Fish

15g sample size

GCxGC-IDTOFMSGC-IDHRMSGC-IDQISTMS/MS

RSD GCxGC-TOFMS: 2-17% (33%)RSD GC-HRMS: 4-8% (34%)RSD GC-MSMS: 6-22%

PCDD/Fs in Fish

15g sample size RSD GCxGC-TOFMS: 12-60% (95%)RSD GC-HRMS: 4-32% (64%)RSD GC-MSMS: 5-30% (44%)

2,3,7,

1,2,3,

4,7,8-

1,2,3,

6,7,8-

1,2,3,

7,8,9-

1,2,3,

4,6,7,

DDOCDD

2,3,7,

1,2,3,

2,3,4,

1,2,3,

4,7,8-

1,2,3,

6,7,8-

1,2,3,

7,8,9-

2,3,4,

6,7,8-

1,2,3,

4,6,7,

1,2,3,

4,7,8,

DFOCDF

fwGCxGC-IDTOFMSGC-IDHRMSGC-IDQISTMS/MS

1547 1549 1551 1553 1555 1557 1559

Labels(~85pg)

Natives(~1pg)

PM = 4s RIC

1,2,3,7,8-PeCDF

29002400190014009000

1tR (s)

2tR (s)

‘Cleaned’ Milk Extract

Analytes of interest

Matrix interferences

Non- and Mono-ortho PCBs in Milk

RSD GCxGC-TOFMS: 5-20% (46%)RSD GC-HRMS: 2-10%RSD GC-MSMS: 7-15%

120g sample size

GCxGC-IDTOFMSGC-IDHRMSGC-IDQISTMS/MS

PCDD/Fs in Milk

RSD GCxGC-TOFMS: 9-55% (75%)RSD GC-HRMS: 7-14% (34%)RSD GC-MSMS: 5-30%

120g sample size

2,3,7,

1,2,3,

4,7,8-

1,2,3,

6,7,8-

1,2,3,

7,8,9-

1,2,3,

4,6,7,

DDOCDD

2,3,7,

1,2,3,

2,3,4,

1,2,3,

4,7,8-

1,2,3,

6,7,8-

1,2,3,

7,8,9-

2,3,4,

6,7,8-

1,2,3,

4,6,7,

1,2,3,

4,7,8,

DFOCDF

fwGCxGC-IDTOFMSGC-IDHRMSGC-IDQISTMS/MS

0.87±0.18

0.85±0.05

0.95±0.05

Mono-ortho PCBs in Pork

RSD GCxGC-TOFMS: 4-22%RSD GC-HRMS: 3-17%RSD GC-MS/MS: 9-18%

30g sample size

PeCB-11

HxCB-15

HxCB-16

241.3 ± 28.3297.9 ± 8.09

268.8 ± 25.6

PCDD/Fs in Pork

30g sample size

2,3,7,8-TeCDD

1,2,3,7,8-PeCDD

1,2,3,4,7,8-HxCDD

1,2,3,6,7,8-HxCDD

1,2,3,7,8,9-HxCDD

1,2,3,4,6,7,8-HpCDDOCDD

2,3,7,8-TeCDF

1,2,3,7,8-PeCDF

2,3,4,7,8-PeCDF

1,2,3,4,7,8-HxCDF

1,2,3,6,7,8-HxCDF

1,2,3,7,8,9-HxCDF

2,3,4,6,7,8-HxCDF

1,2,3,4,6,7,8-HpCDF

1,2,3,4,7,8,9-HpCDFOCDF

RSD GCxGC-TOFMS: 15-71%RSD GC-HRMS: 4-16%RSD GC-MS/MS: 8-35%

Comparison in terms of TEQs

Use of physico-chemical congener-specific dataand WHO-1998 TEFs to estimate the sum ofPCDD/F and PCB TEQs.

Parallel measurement of sample toxicities usingthe DR-CALUX assay on sub-samples.

Pork Milk

fwGCxGC-IDTOFMS GC-IDHRMS GC-IDQISTMS/MS DR-CALUX

Pork Milk

fwGCxGC-IDTOFMS GC-IDHRMS GC-IDQISTMS/MS DR-CALUX GCxGC-IDTOFMS GC-IDHRMS GC-IDQISTMS/MS DR-CALUX

Bottom: PCDD/F TEQTop: PCB TEQ

Comparison in terms of CostBased on 1,000 samples/year over 5 years(including employment, purchases, paying-off,maintenance, licensing, etc…)

GC-IDHRM

GCxGC-ID

GC-IDQIS

DR-CALUX

Scientist employment 23% 35% 35% 36%Extraction 11% 8% 11% 7%Clean-up 28% 27% 33% 29%Measurement 38% 30% 21% 8%Licensing and royalties - - - 20%

Cost per sample (Euros) 500 500 420 270

GCxGC-TOFMS using ID works fine.

QA/QC criteria of ‘reference method’ can beapplied PLUS 2 tR available for specificity.

TOFMS is a robust instrument.

Integration of peaks requires more work.

A sensitivity improvement is still welcome.

MS-based alternative methods not to beassimilated to biological screening methods.

Take Home Message #1

Speed(Low cost)

Selectivity

Sensitivity

Political, economical, …

Real life Pyramid

GC-QISTLRMS²

GC-TOFMS

GCxGC-TOFMS

EIAs, RBAs

GC-HRMS

Take Home Message #2

700 1200 1700 2200 2700

1tR (s)

2tR (s)

35 analyte/45min0.8 analyte/minOne single injection

Multi-Group Analyte Measurement

GCxGC-IDTOFMS

Source tracking (pattern recognition)

144x4 158x10 172x18 TICx-0.5

Metabolite Screening

GCxGC-LRTOFMS

Focant, Sjödin, Patterson Jr., unpublished data.

Sensitivity Backup GCxGC-IDHRMS

Sectors

Selective MSLow data densityTarget analytes

R>10,000

GCxGC-HR(sector)MSCryogenic zone compression on sector HRMS

- Attogram (10-18g)detection level…

- Not much ions inthe MS anymore…

313ag 2,3,7,8-TCDD(S/N=890)

Quantity Number of moles Number of molecules

1 microgram (µg) or 10-6 g 3 nanomoles or 3.10-9 2,000,000,000,000,000 (2.1015)1 nanogram (ng) or 10-9 g 3 picomoles or 3.10-12 2,000,000,000,000 (2.1012)1 picogram (pg) or 10-12 g 3 femtomoles or 3.10-15 2,000,000,000 (2.109)1 femtogram (fg) or 10-15 g 3 attomoles or 3.10-18 2,000,000 (2.106)1 attogram (ag) or 10-18 g 3 zeptomoles or 3.10-21 2,000 (2.103)1 zeptogram (zg) or 10-21 g 3 yaktomoles or 3.10-24 2 (2.100)

1 yaktogram (yg) or 10-24 g Phantom moles 0

Quantity Number of moles Number of molecules

1 microgram (µg) or 10-6 g 3 nanomoles or 3.10-9 2,000,000,000,000,000 (2.1015)1 nanogram (ng) or 10-9 g 3 picomoles or 3.10-12 2,000,000,000,000 (2.1012)1 picogram (pg) or 10-12 g 3 femtomoles or 3.10-15 2,000,000,000 (2.109)1 femtogram (fg) or 10-15 g 3 attomoles or 3.10-18 2,000,000 (2.106)1 attogram (ag) or 10-18 g 3 zeptomoles or 3.10-21 2,000 (2.103)1 zeptogram (zg) or 10-21 g 3 yaktomoles or 3.10-24 2 (2.100)

1 yaktogram (yg) or 10-24 g Phantom moles 0

Patterson Jr., Welch , Turner , Focant, Organohalogen Compds 67 (2005) 107.

Report with undesirable ‘not detected’Report with NO ‘not detected’

Sensitivity not a Dimension…Low level sample

Sample preparation

GCxGC-IDHRMS(Selected Descriptors)

GC-IDHRMS(Multi-Group)

2,3,7,8-TCDD… 17 PCDD/Fs + NO-PCBs

- D. Patterson Jr., W. Turner, A. Sjödinand Lab. staff at CDC

- G. Eppe, C. Pirard, M.-L. Scippo andLab. staff in Liège

- Fluid Management Systems Inc.- Leco Corp.

Thanks to

Related papers (i)• J.-F. Focant, A. Sjödin, D.G. Patterson Jr., 2006. Human Biomonitoringof Persistent Toxicants using Comprehensive Two-Dimensional Gas Chromatography and Time-of-Flight Mass Spectrometry. In: W.M.A.Niessen (Eds.). The Encyclopedia of Mass Spectrometry, Volume 8, Hyphenated Methods. ElsevierAmsterdam, The Netherlands, pp. 553-564.

• G. Eppe, E. De Pauw, J.-F. Focant, 2006. High-Resolution GC Coupled to High-Resolution MS in the Analysis of Dioxins and Related Substances, Principles and Applications. In: W.M.A. Niessen (Eds.). The Encyclopedia of Mass Spectrometry, Volume 8, Hyphenated Methods. ElsevierAmsterdam, The Netherlands, pp. 531-541.

•J.-F. Focant, G. Eppe, M.-L. Scippo, A.-C. Massart, C. Pirard, G. Maghuin-Rogister, E. De Pauw, Comprehensive two-dimensional gas chromatography isotope dilution time-of-flight mass spectrometry for the measurement of dioxins and PCBs in foodstuffs: comparison against other methods, J. Chromatogr. A. 1086 (2005) 45-60. .

Related papers (ii)• J.-F. Focant, C. Pirard, G. Eppe, E. De Pauw, Recent advances in mass spectrometric measurement of dioxins, J. Chromatogr. A. 1067 (2005) 265-275.

• J.-F. Focant, A. Sjödin, W.E. Turner, D.G. Patterson Jr., Measurement of Selected Polybrominated Diphenyl ethers, Polybrominated and Polychlorinated Biphenyls, and Organochlorine Pesticides in Human Serum and Milk using Comprehensive Two-Dimensional Gas Chromatography Isotope Dilution Time-of-Flight Mass Spectrometry, Anal. Chem. 76 (2004) 6313-6320.

• G. Eppe, J.-F. Focant, C. Pirard, E. De Pauw, PTV-LV-GC/MS/MS as screening and complementary method to HRMS for the monitoring ofdioxin levels in food and feed, Talanta 63 (2004) 1135-1146.

• J.-F. Focant, C. Pirard, E. De Pauw, Automated sample preparation-fractionation for the measurement of dioxins and related compounds in biological matrices: A review. Talanta 63 (2004) 1161-1113.

Related papers (iii)• J.-F. Focant, E. Reiner, K. MacPherson, J. Cochran, F. Dorman, A. Sjödin, D.G. Patterson Jr., Measurement of PCDDs, PCDFs, and non-ortho-PCBs by Comprehensive Multi-Dimensional Gas Chromatography-Isotope Dilution Time-of-Flight Mass Spectrometry (GCxGC-IDTOFMS), Talanta 63 (2004) 1231-1240.

• J.-F. Focant, A. Sjödin, D.G. Patterson Jr., Improved Separation of the 209 Polychlorinated Biphenyl Congeners Using Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry, J. Chromatogr. A. 1040 (2004) 227-238.

• J.-F. Focant, J.W. Cochran, J.-M.D. Dimandja, E. De Pauw, A. Sjödin, W.E. Turner, D.G. Patterson Jr., High throughput analysis of selected polychlorinated biphenyls (PCBs) in human serum by gas chromatography/isotope dilution time-of-flight mass spectrometry (GC/IDTOFMS), Analyst 129 (2004) 331-336.

Related papers (iv)•J.-F. Focant, A. Sjödin, D.G. Patterson Jr., Qualitative evaluation of thermal desorption-programmable temperature vaporization-comprehensive multi-dimensional gas chromatography-time-of-flight mass spectrometry for the analysis of selected halogenated contaminants. J. Chromatogr. A 1019 (2003) 143-156.

• C. Pirard, E. De Pauw, J.-F. Focant, A new strategy for comprehensive analysis of polybromodiphenylethers (PBDEs), polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs) and polychlorobiphenyls (PCBs) by gas chromatography coupled with mass spectrometry (GC/MS). J. Chromatogr. A 998 (2003) 169-181.

• J.-F. Focant, E. De Pauw, Fast automated extraction and clean-up of biological fluids for polychlorinated dibenzo-p-dioxins, dibenzofuransand coplanar polychlorinated biphenyls analysis. J. Chromatogr. B 776 (2002) 199-212.

• J.-F. Focant, H. Shirkhan, E. De Pauw, On-line automated pPLE andmulti-column clean-up system for PCDD/F and PCB analysis in foodstuffs. Organohalogen Compds 55 (2002) 33-36.

• C. Pirard, J.-F. Focant, E. De Pauw, An improved clean-up strategy for simultaneous analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in fatty food samples. Anal. Bioanal. Chem. 372 (2002) 373-381.

•J.-F. Focant, C. Pirard, G. Eppe, E. De Pauw, Fast Clean-up for polychlorinated dibenzo-p-dioxins, dibenzofurans and coplanar polychlorinated biphenyls analysis of high fat content biological samples. J. Chromatogr. A 925 (2001) 207-221.

• J.-F. Focant, G. Eppe and E. De Pauw, Optimisation and Use of Tandem Mass Spectrometry in Comparison with Immunoassay and HRGC/HRMS for PCDD/Fs Screening, Chemosphere 43 (2001) 417-424.

emerging hyphenated and comprehensive multi-dimensional … · 2020. 6. 13. · 23478-pecdf pcdd/f...

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calculated risk-

afetação de cargas no transporte rodoviário de...

calculated industries 4020

how is pressure calculated?

calculated for you

a calculated arson

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homes for...

estimates basic calculated

calculated repentance isaiah 58:1-12. calculated repentance...

e del vice presidente cingolani - senato.it · paolucci di...

pengalaman pasien dengan vertigo...

reports/2007_3qtr_n_summa.pdfmonitoring system. ... percent...

warfare can be calculated