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Method development for the determination of pesticide residues in vegetables and fruits by using solid-phase microextraction
No full textComparison of different types of coatings in headspace solid phase microextraction for the analysis of pesticide residues in vegetables and fruits
No full textDespite the continuing development of solid-phase microextraction (SPME) fiber coatings, their selection presents some difficulties for analytes in choosing the appropriate fiber for a particular application. There are many types of SPME coatings available commercially. The most widely used for determination of pesticide residues in vegetable and fruits are polydimethylsiloxane (PDMS) and polyacrylate (PA). A headspace solid phase microextraction (HS-SPME) procedure using these two commercialized fibers (PDMS and PA) is presented for the determination of selected groups of organochlorine and organophosphorus pesticides. The extraction performances of these compounds were compared using these two fibers. The optimal experimental procedures for the adsorption and desorption of pesticides were determined. An explanation for the extraction differences is suggested based on the different thickness, polarity of the polymeric film of fibers and the different extracting matrices. In addition, the higher detector response of the pesticides after addition of aliquots of water and an organic solvent to the vegetable and fruit samples are also discussed. The SPME fibers were reusable until a maximum of 120 extractions. Finally, the optimized procedures were applied successfully for the determination of these compounds in vegetable and fruits samples. Mean recoveries for all pesticides were between 75.0- 97% with RSD below 7%
Simultaneous determination of nine commercial pesticide formulations by gas chromatography multi-pesticide with an internal standard method
No full textA gas chromatography multi-pesticide with an internal standard method has been developed to analyze simultaneously separate nine active ingredients (acephate, carbaryl,
chlorpyrifos, chlorothalonil, diazinon, dimethoate, malathion, profenofos, quinalphos) in different commercial pesticide formulations. A mixture of pure standard solution spiked with 1-chloro-4-fluorobenzene as the internal standard was injected into the GC-ECD and a six point calibration curve that demonstrated a linear range was established for each target compound. Samples of each formulation, mixed with internal standard were analyzed five times to obtain coefficients of variation which are less than 1%. Three concentration levels of each formulation were determined and the results were within the specification with the accuracies obtained were within 98.1% to 101.9%. This method involves a quick analysis, cost effective and without any sample pretreatment process. This measurement method can be very useful for determining pesticide formulations in routine analysis
Application of solid-phase microextraction for the determination of pesticides in vegetable samples by gas chromatography with an electron capture detector
No full textHeadspace solid phase microextraction in combination with gas chromatography-mass spectrometry for the rapid screening of pesticide residues in vegetables and fruits
No full textA method for the determination of 5 organophosphorus (diazinon, malathion, quinalphos,
chlorpyrifos and profenofos) and 2 organochlorine (alpha endosulfan and beta endosulfan)
pesticides in vegetables (cucumber, tomato, bakchoy) and fruits (star fruit, strawberry, guava)
samples was developed. The samples were diluted with water and extracted with 2% vol/weight (v/w) of a mixture of methanol/acetone (1:1). The analytes in samples were extracted by headspace solid-phase microextraction (HS-SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS) using a selected ion-monitoring (SIM) mode. Limit of detection of the method was between 0.001 to 0.01 mg/kg and limit of quantification was between 0.005-0.05 mg/kg for all investigated pesticides. Relative standard deviations for duplicate analyses of sample fortified at 3 levels were not higher than 10%. Recovery test were performed for concentration between 35-0.25 mg/kg. Mean recoveries for each pesticide were between 77.0-96.4% for vegetables and between 79.7-97.5% for fruits with RSD below 5%. Therefore, the proposed method is applicable in the
analysis of pesticides in vegetable and fruit matrices
Modified dispersive liquid-liquid microextraction using green solvent for determination of polycyclic aromatic hydrocarbons (PAHs) in vegetable samples
No full textPengubahsuaian, pencirian dan penggunaan zeolit asli sebagai bahan penjerap terhadap bahan pencelup sintetik bes
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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