Analytical Methods Multivariate study of parameters in the determination of pesticide residues in apple by headspace solid phase microextraction coupled to gas chromatography–mass spectrometry using experimental factorial design Lukman Bola Abdulra’uf a,b,⇑ , Guan Huat Tan a,⇑ a Department of Chemistry, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia b School of Basic and Remedial Studies, Kwara State College of Education, P.M.B. 1527, Ilorin 240244, Kwara State, Nigeria article info Article history: Received 11 August 2012 Received in revised form 30 April 2013 Accepted 3 July 2013 Available online 12 July 2013 Keywords: SPME Multivariate analysis Factorial design Pesticide residues abstract Solid-phase microextraction (SPME) is a solvent-less sample preparation method which combines sample preparation, isolation, concentration and enrichment into one step. In this study, multivariate strategy was used to determine the significance of the factors affecting the solid phase microextraction of pesti- cide residues (fenobucarb, diazinon, chlorothalonil and chlorpyrifos) using a randomised factorial design. The interactions and effects of temperature, time and salt addition on the efficiency of the extraction of the pesticide residues were evaluated using 2 3 factorial designs. The analytes were extracted with 100 lm PDMS fibres according to the factorial design matrix and desorbed into a gas chromatogra- phy–mass spectrometry detector. The developed method was applied for the analysis of apple samples and the limits of detection were between 0.01 and 0.2 lg kg À1 , which were lower than the MRLs for apples. The relative standard deviations (RSD) were between 0.1% and 13.37% with average recovery of 80–105%. The linearity ranges from 0.5–50 lg kg À1 with correlation coefficient greater than 0.99. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Fruits and vegetables provide the body with micronutrients (minerals and vitamins) that are very vital to the body but are re- quired in small quantities (Lewis & Ruud, 2004). This has led to their production in large quantities to meet the ever growing de- mand. To achieve this, pesticides were introduced to protect fruits and vegetables on the farm and during storage. Pesticides, includ- ing organophosphorous pesticides (OPP), organochlorine pesticides (OCP), carbamate pesticides (CP), phenyl urea pesticides (PUP), pyrethroid pesticides (PP) and carbamate pesticides (CP) have been used effectively in controlling pests, fungi and weeds, thereby ben- eficial to the steady increase in agricultural production (Chai & Tan, 2010; Vazquez, Mughari, & Galera, 2008). However, they persist in the food chain, due to their penetrating effect into the tissues of fruits and vegetables and therefore there is a need to analyse the level of pesticide residues in food. Sample preparation is the most crucial and critical steps in the analysis of pesticide residues from complex fruit and vegetable matrices (Menezes Filho, dos Santos, & de Paula Pereira, 2010). The introduction of solid phase microextraction (SPME) technique in 1990 (Arthur & Pawliszyn, 1990), has helped to overcome the problems inherent in the solvent-based sample preparation tech- niques. Solid phase microextraction is a solvent free sample prep- aration and extraction technique developed by Pawliszyn and his co-workers (Arthur & Pawliszyn, 1990). It is an efficient, simple, versatile and effective adsorption/absorption and desorption tech- nique with minimum matrix interference. It eliminates the use of toxic solvents and combines sampling, isolation, concentration and enrichment in one step (Ouyang & Pawliszyn, 2008; Pawliszyn, 1997). It was developed to overcome the problems associated with solvent-based, time consuming techniques, such as, liquid–liquid extraction (LLE), solid phase extraction (SPE), supercritical fluid extraction (SFE), and accelerated solvent extraction (ASE) (De Kon- ing, Janssen, & Th. Brinkman, 2009). The traditional techniques also required a large volume of sample and solvents which impose environmental pollution and health hazards (Kataoka, Lord, & Paw- liszyn, 2000). The SPME technique is based on the use of a fused sil- ica or metal alloy that is coated on the outside with an appropriate polymerized stationary phase, attached to a stainless steel, mounted on a fibre holder housed in a modified syringe (Arthur, Killam, Buchholz, Pawliszyn, & Berg, 1992; Beltran, Peruga, Pitarch, & Lopez, 2003). The SPME process involves two basic steps which 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.07.022 ⇑ Corresponding authors. Address: Department of Chemistry, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia. Tel.: +60 102343957 (L.B. Abdulra’uf). E-mail address: abdulrauflukman@siswa.um.edu.my (L.B. Abdulra’uf). Food Chemistry 141 (2013) 4344–4348 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem