Solid-Phase Microextraction Liquid Chromatography/Tandem Mass Spectrometry To Determine Postharvest Fungicides in Fruits

• Published in: Analytical chemistry (Washington) 2003-07, Vol.75 (14), p.3606-3615
• Main Authors: Blasco, Cristina, Font, Guillermina, Mañes, Jordi, Picó, Yolanda
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Calibration; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, Liquid; Exact sciences and technology; Fruit - chemistry; Fungicides, Industrial - analysis; Indicators and Reagents; Mass Spectrometry; Other chromatographic methods; Pesticide Residues - analysis; Reference Standards; Spectrometric and optical methods; Spectrophotometry, Ultraviolet
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac0341362

A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-μm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were investigated, and their impact on the SPME-LC/MS was studied. Dynamic and static modes of desorption were compared and the variables affecting desorption processes in SPME-LC optimized. Static desorption provided the best recoveries and peak shapes. Recoveries at the limit of quantification (LOQ) levels were between 10% for prochloraz and 60% for o-phenylphenol, with relative standard deviations from 13.6% for prochloraz to 3.1% for o-phenylphenol. The versatility of the method was also exhibited by its excellent linearity in the concentration intervals between 0.0005 and 5 mg kg-1 for dichloran and 0.01−10 mg kg-1 for tolclofos methyl and prochloraz. LOQs ranged from 0.25 to 1 μg g-1 using DAD, from 0.002 to 0.01 μg g-1 using LC/MS, and from 0.0005 to 0.01 to μg g-1 using LC/MS/MS. LOQs obtained in the present study using LC/MS and LC/MS/MS are lower than maximum residue limits established for all the fungicides in any matrix studied. The method enables to determine polar pesticides at low-microgram per gram levels in fruits.