Food & Flavour Analysis by PFPD
Introduction • Sulphur compounds are an important component of flavour analysis • Responsible for specific and distinctive flavours in many foods & beverages • Difficult to analyse and identify because present at minimal concentrations • MS or FID commonly used, but not sensitive enough to detect sulphur compounds at trace levels
GC Configuration MS/FID/PFPD Agilent FID in Front for Sulphur Marking OI Analytical PFPD in Back For Quantitation PFPD FID 6890N GC with 5973N MS
Column Configuration for 3 Detectors LDV connector 3-hole ferrule 3 transfer lines Detector end split using low dead volume connector and a 3-hole ferrule Standard installation at injection port
Headspace Apparatus Line carrying He purge gas GC inlet liner packed With 100 mg Tenax ~20 grams coffee
Coffee Headspace by MS/FID/PFPD 3 Simultaneous Chromatograms From Coffee “A” MS FID Sulfur by PFPD Over 200 sulfur peaks detected
PFPD Used To Identify Sulfur RTs MS PFPD A NIST search results for peak “A”
Compound Retention Times • MS MS and PFPD (and FID) chromatograms very slightly offset by 4-5 seconds 23.67 min – Reproducible • Due to fact that MS is under vacuum and PFPD and FID are under slightly PFPD positive pressure • Offset easily determined with a standard prior to analysis of unknowns 23.75 min
Competitive Analysis Sulfur by PFPD • The sulfur chromatogram, or “fingerprint” is unique for each coffee blend • Can be used to identify differences between specific blends • Determine which sulfur compounds contribute distinctive flavor and aroma
Competitive Analysis of 3 Coffees Sulfur in Coffee “A” Sulfur in Coffee “B” Note differences Sulfur in In the 3 chros Coffee “C”
Sulfur in Galbanum Oil by PFPD MS • Essential oil distilled from the galbanum plant • Green, fresh leafy odor, dry woody FID undertones, pine Expanded view of sulfur highlights • Used in production of fragrances • Using an FPD only 4 sulfur peaks were Sulfur by PFPD detected
Sulfur in Fishwort Oil • 0.1 L injection MS • Essential oil distilled from the fishwort, or “Chinese Lizard Tail”, plant (2 varieties) • Corriander aroma or FID Mint Sulfide only lemon/orange odor Detectable with • Used in production of The PFPD flavors • Using an FPD no sulfur peaks were detected Sulfur by PFPD
Sulfur in Beverage Grade CO 2 Each compound present at ~2.0 ppm in CO 2 COS CS 2 H 2 S Chromatogram courtesy of JAS
Sulfur in Strawberry by PFPD Sweet Charlie Sweet Charlie Camaorsa Camaorsa Chromatogram courtesy of Russell Rouseff, PhD, at University of Florida
Sulfur in Grapefruit by PFPD Chromatogram courtesy of Russell Rouseff, PhD, at University of Florida
Ethanethiol Methyl sulfide Sulfur in Beer by Headspace 2-Methylpropanethiol Thiophene 1-Methylpropanethiol Dimethyl disulfide Amyl sulfide Heptanethiol tert -Butyl disulfide repeatability better than at 10 ppb PFPD 10%
Sulfur in Beer by PFPD Miller Genuine Draft Budweiser Unk MTHIOAC MS MDS Unk ES Miller Lite Sam Adams Sulfur concentrations in beers tested ranged from 0.1 ppbS to ~4 ppbS
Sulfur in Wine and Rum by PFPD ~4.5 ppbS MDS White Rum Red Wine “A” As MDS M 0.5 ppbS S As MS Unk Unk Un 0.15 ppbS 0.3 ppbS k As ES As MTS Red Wine “B” Dark Rum ~0.1 ppbS In Unknown
Sulfur in Liquor by PFPD 15 uV 240 Crown Royal Jack Daniels k n o w n 220 U n b 1 . 4 p p 200 180 Methyl sulfide 160 <0.5 ppb 140 120 0 2 4 6 8 10 12 14 16 min Finnish Cranberry Liquor Kaluha 15 uV 1000 Dimethyl disulfide 900 0.6ppb M e t h y l s u l f i d e 800 700 8 . 4 p p b 600 500 400 300 200 100 2 4 6 8 10 12 14 16 min
Sulfur in Coffee & Tea by P&T/PFPD Brewed Coffee ~4 ppbS As MDS 0.65 ppbS As MS 1.0 ppbS As MTS Iced Tea Unknown <0.05 ppb S
Sulfur in Juice by P&T/PFPD Grapefruit Juice 1.0 ppbS as MS Orange Juice MS saturated The detector Apple Juice MS reached “Self-Quenching”
PFPD-MS Configuration Split/Splitless OI 5380 Injector PFPD HP-5MS 30 cm, 0.25 mm ID 0.4 mL/min He HP-5973A HP-5MS 30 meter, 0.25 mm ID, 0.25 m film MS 1.0 mL/min He DB-1 20 cm, 0.1 mm ID, 0.1 m film 0.6 mL/min He
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