1. GC-TRIPLE QUADRUPOLE MASS SPECTROMETRY MS/MS vs GC-HRMS FOR THE ANALYSIS OF POLYCHLORINATED DIOXINS AND FURANS
UNIVERSITY OF MURCIA
Agricultural Chemistry Dep.
Andreo, P.(a), Almela, P.(a), Veracruz, C.(a), García, N.(a), Almela, L.(a), Valero, A.(b), Coll, L.(b), Albaladejo, J.A.(b) (a)University of Murcia. Campus Espinardo Murcia. Spain. (b) ECOSUR Lab . Pol. Base Lorquí (Murcia). Spain
Material and Methods
Introduction O 1 2 3 4 6 7 8 9
Clm
Cln
Samples: Fats, feeds and foods where frozen or lyophilized (preferably).
Extraction and concentration: Soxhlet extraction (EPA 1613 method) or QuEChERS. Pre-concentration with a rotary evaporator and final dry under N2 stream.
Clean-up: Multiple-phase columns (anhydrous Na2SO4/ silica-10%AgNO3/ silica-22%H2SO4/ silica-44% H2SO4/ silica- 2%KOH) from SUPELCO®.
PCDDs/PCDFs separation. Column chromatography using deactivated Florisil® like stationary phase.
GC MS/MS: Column elution was pre-concentrated, micro- filtered (0,45 μm) and concentrated to 0,1 mL under N2 stream. After this, 10 μL of n-nonane and 10 μL of Internal Standard was added before the injection.
Standards: Standard solutions were of Wellington Lab.
Instrument: Varian 450–GC equipped with triple quadrupole detector Varian 300–MS. Column DB m x 0,32 mm x 0,25 μm. Analytical conditions on demand.
Quantification: By means of isotope dilution (EPA 1613).
Persistent organic pollutants (POPs) are a group of compounds originated from anthropogenic activities. Between them, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), generally referred as “dioxins”, are of great concern due to their high toxicity. The main exposure to dioxins and furans (90 %) occurs through food.
Laterally chlorinated compounds (2,3,7,8-position) are resistant to metabolism and they are the only congeners found in living organisms. For this reason, toxic equivalence factors (TEFs) have been developed to establish the total toxic equivalence (TEQ) and to predict their biological effects. Seventeen PCDDs and PCDFs have already been incorporated to TEFs concept.
The EPA 1613 method advises the use of HRMS for the analysis of “dioxins”. As alternative, we have studied the use of triple quadrupole mass spectrometry MS/MS, a less expensive technique. O 1 2 3 4 6 7 8 9
Clm
Cln
Results
Results
Monitorized ions
PCDD’s/PCDF`s
Precursor 1
m/z
Precursor 2
Product 1
Product 2
TCDD
320
322
257
259
TCDF
304
306
241
243
PeCDD
354
356
291
293
PeCDF
338
340
275
277
HxCDD
388
390
325
327
HxCDF
372
374
309
311
HpCDD
424
426
361
363
HpCDF
408
410
345
347
OCDD
458
460
395
397
OCDF
442
444
379
381
MCounts
Concentrations (pg/μL)
y= *x
R2 =
Chromatogram of a standard mixture of PCDDs/PCDFs
-Chromatographic data were processed using a developed software that included TEFs to quantify PCDDs and PCDFs.
Although HRMS shows the advantage of the mass accuracy, tandem quadrupole MS/MS achieved high specificity through multiple reaction monitoring. Each compound was identified by means of precursor ions M and (M+2) and two transitions corresponding to (M-COCl-) and (M+2-COCl-), respectively.
The analytes did not co-eluted in our system due to high length of the column.
The used methodology provided a clear background for all types of matrix analyzed.
The different recovery of the congeners and their specific response was offset by means of the isotopic dilution, to reach a recovery ratio higher than EPA recommendations.
-In conclusion, triple quadrupole mass spectrometry is a feasible and cost-effective alternative to HRMS.
Calibration curve for a native PCDDs
(similarly for the rest of PCDDs/PCDFs)