Determination of the Levels of Fungicides on Citrus Fruits

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Determination of the Levels of Fungicides on
Citrus Fruits

• By Miseung Borgers
• Chem 4101, Fall 2008

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Introduction

• Fungicides applied on the surface of
  post-harvest citrus fruits are possible health
  threats since they can be easily absorbed into
  the body through peeling and eating with hands.
  Controlling and monitoring the appropriate levels
  of fungicides would reduce the possible harmful
  effects by the ingestion.

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Maximum residue limits for five fungicides and
their structures
(Ref. 1, 3)
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Method

• HPLC/MS
• - Since the fungicides have different
  polarities, they are retained to the stationary
  phase by different degrees. This allows
  separation by HPLC.
• - High sensitivity proved by the limit of
  detection (lt 0.03 ppm)
• - No derivatization is needed
• - Fastness (No additional clean-up for sample
  preparation)
• - Highly automated (reduced manual labor and
  human intervention)
• (Ref. 2)

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Procedure
www.thesun.co.uk
www.buchi.com
Homogenization
ic3db.ou.edu
Extraction
www.hhsc.ac.uk
LC/MSD system
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Preparation of standards, controls and samples

• (1) Homogenization
• - Blend chopped oranges with ethyl acetate,
  anhydrous sodium sulphate
• - For controls, use
• oranges without post
• harvest fungicide
• treatment

• (2) Extraction
• - Use sodium sulphate for filtering
• - Add acetonitrile, Dry
• - Dissolve in acetonitrile 2 mM ammonium
  formate
• (5050, v/v)
• - For standards, controls mixed with fungicide
  solutions
• - Standard Concentrations
• 0.05, 0.5, 5 ppm

(Ref. 3)
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Conditions for HPLC

• Injection volume 5 µL
• Solvents used for mobile phase methanol, 2 mM
  ammonium formate in water
• Gradient elution with flow rate of 1 mL/min

(Ref. 3)
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Conditions for interface and MS

• APCI Interface
• - Vaporizing temp. 325 ºC
• - Nebulizer gas Nitrogen at 4.0 bar
• - Drying gas Nitrogen at 4 L/min at 350 ºC
• - Capillary voltage 4000 V
• - Corona current 4 µA
• - LOD 0.01 µg/mL except for benomyl at 0.1 µg/mL

• MS
• Use SIM mode, fragmentor voltage 70 V

(Ref. 3)
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Chromatogram
A) Standard with concentration of 0.5 ppm, B)
Control, C) Sample Peak identification (1)
Carbendazim, (2) thiabendazole, (3) thiophanate
methyl, (4) benomyl, and (5) imazalil
(Ref. 3)
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Results and Conclusions

• HPLC/MS provides a reliable, sensitive analytical
  tool in determining the levels of fungicides on
  citrus fruits.
• By monitoring the levels of fungicides, the
• possible health threats can be minimized.

(Ref.3)
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Instrument Specifications

• HP-1100 Series LC/MSD
• - quadrupole based LC/MSD system
• - HPLC column- Zorbax Rapid Resolution SB-C18
  (30 x 4.6 mm I.D., 3.5 µm) column with a guard
  column of LiChrosorb RP-8 (10 x 4.6 mm, 5 µm)
• - standard API source that can be configured as
  APCI or ES
• 
  
  (Ref. 3)
• - mass range 2-3000 m/z
• - mass accuracy 0.13 u within the calibrated
  mass range in scan mode
• - mass axis stability 0.13 u over 8 hours
• - scan speed 2500 u/s standard mode
• 5250 u/s fast scan mode
• - SIM sensitivity ESI at 400 µL/min
• APCI at 1000 µL/min
• - multiple signal acquisition ability to cycle
  through four different acquisition modes on a
  scan-by-scan basis within a single run
  (Ref. 4)

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References

• 1) http//postharvest.ifas.ufl.edu/MRLs/FL20Citru
  s20
• MRLs20-209.2.08.pdf accessed December 2nd,
  2008
• 2) http//cvuas.xn--untersuchungsmter-bwnzb.de/pdf
  /
• poster_israel1999_orgzinn.pdf accessed
  December 3rd,
• 2008
• 3) Fernández, M. Rodríguez, R. Picó, Y. Mañes,
  J.
• J. Chromatogr. A. 2001, 912, 301-310
• 4) http//www.gentechscientific.com/10156.htm
  accessed
• December 3rd, 2008

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