2,078 research outputs found

    Determination of pesticides in fruit and fruit juices by chromatographic methods. An overview

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    In order to combat a variety of pests, pesticides are widely used in fruits. Several extraction procedures (liquid extraction, single drop microextraction, microwave-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, solid-phase extraction, solid-phase microextraction, matrix solid-phase dispersion, and stir bar sorptive extraction) have been reported to determine pesticide residues in fruits and fruit juices. The significant change in recent years is the introduction of the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) methods in these matrices analysis. A combination of techniques reported the use of new extraction methods and chromatography to provide better quantitative recoveries at low levels. The use of mass spectrometric detectors in combination with liquid and gas chromatography has played a vital role to solve many problems related to food safety. The main attention in this review is on the achievements that have been possible because of the progress in extraction methods and the latest advances and novelties in mass spectrometry, and how these progresses have influenced the best control of food, allowing for an increase in the food safety and quality standards

    Development of Authenticity Methods for Apple and Pear Juices

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    Due to its widespread global consumption and economic value, fruit juice is a common target for adulteration through debasing by unscrupulous producers. Two common methods of fruit juice adulteration are debasing with commercial sweeteners and juice-to-juice adulteration. The overarching goal of this research was to develop methods to detect the undeclared addition of less expensive commercial sweeteners to pear juice and the undeclared addition of apple to pear and pear to apple juice. Methods to detect the undeclared addition of high fructose corn syrup (HFCS), hydrolyzed inulin syrup (HIS) and total invert sugar (TIS) to commercial pear juice were developed through oligosaccharide profiling employing high performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) and capillary gas chromatography with flame ionization detection (CGC-FID). Based on the application of these methods to intentional pear juice debasing, these three commercial sweeteners could be detected at levels of 0.5-3.0% (v/v). Coupled with the developed authenticity analysis for pear juice, the developed profiling methods were used to examine the carbohydrate/oligosaccharide profile of pear juice as a function of commercial processing. Chromatographic results showed that the majority of carbohydrate/oligosaccharide formation occurred during the mashing stage of juice production where enzymes (i.e. pectinases, hemicellulases and amylases) are employed. The remaining processing stages were found to have a minimal impact on the carbohydrate/oligosaccharide profile of commercial pear juice. Methods for the detection of juice-to-juice debasing between apple and pear juices were developed using phenolic profiling. High performance liquid chromatography with photodiode array detection (HPLC-PDA) was used to determine the phenolic profiles of commercial apple and pear juice concentrates from major world production regions. The phenolic profiles were used to identify fingerprint compounds for use in juice-to-juice adulteration detection. One phenolic marker was identified in apple juice and two in pear juice (excluding arbutin). These compounds were analyzed by UV-vis and NMR spectroscopic methods, and high resolution MS and LC-MS/MS spectrometry. Results from these analyses identified the fingerprint compounds as 4-O-p-coumarylquinic acid in commercial apple juice, and isorhamnetin-3-O¬-rutinoside and abscisic acid in commercial pear juice. The total phenolic content and antioxidant activities of the 27 apple and 32 pear juices used throughout this research were determined by the Folin-Ciocalteu (total phenolic content), HPLC-PDA (total phenolic chromatographic index), Trolox equivalent antioxidant activity (TEAC) and DPPH methods. The total phenolic content of apple and pear juices were found to be 294.7 ± 128.2 and 246.4 ± 45.1 ppm GAE and the total phenolic chromatographic indices were 128.8 ± 44.9 and 211.7 ± 57.2 ppm, respectively. The TEAC of apple and pear juices were found to be 130.8 ± 60.8 and 150.8 ± 63.9 mM Trolox/100 mL, while the DPPH radical scavenging abilities were 21.5 ± 12.1 and 13.6 ± 5.5 mL of DPPH/mL of juice, respectively

    Characterization of Commercial Pectin Preparations by Spectroscopic and Chromatographic Techniques.

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    Pectin has a long history as a food additive. However, elucidation of its fine structural and property relationships remains elusive. Recent research has focused on pectin\u27s ability to complex with divalent heavy metals to aid in characterizing it. Commercial pectins of unknown composition were obtained from local grocers. Purified pectin samples from orange peel, lemon peel, and apple pomace, each of low and high levels of methyl esterification and of unknown distribution pattern were also purchased. Instead of metal complexation, several highly absorbing dyes such as Ruthenium Red, Nile Blue, and Acridine Orange were used to complex with the pectins and their resulting UV-Vis spectral patterns were employed to determine if one can characterize the different pectins. Chemometric methods are also included to aid in distinguishing them apart

    CHEMICAL COMPOSITION OF SELECT SASKATOON BERRY VARIETIES WITH AN EMPHASIS ON PHENOLICS

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    In this study, three saskatoon berry varieties (Martin, Northline and Pembina) grown in Saskatchewan, Canada were analyzed for their physicochemical properties (berry size, colour, pH and % seeds), proximate composition, amino acids, major carbohydrates/polyols/galacturonic acid, major minerals, oligosaccharides, organic acids and phenolics. In addition, the phenolic subclass composition and antioxidant activities of whole fruit and pomace from commercial and laboratory scale juice production, and aqueous alcohol fractions were determined. Fruit varieties were found to differ in colour and size but showed similar pH and °Brix values. Proximate analysis results ranged from 80.18-82.79% for moisture, 7.39-10.82% for carbohydrate, 1.13-1.79% for protein, 0.28-0.48% for lipid, 4.23-9.42% for total dietary fibre, and 0.53-0.74% for ash. Major carbohydrates and polyol identified were fructose, glucose, and sorbitol. This work represents only the second report of the detection and quantitation of sorbitol in this fruit. Oligosaccharide profiles were determined by high performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) and capillary gas chromatography with flame ionization detection (CGC-FID) and showed the presence of a number of dextrose (DP2-5) and pectin polymers. Oligosaccharide profiles have not been reported previously. Amino acid contents ranged from 0.83-1.22 g/100 g fresh weight (FW), with arginine, aspartic acid/asparagine, glutamic acid/glutamine and leucine predominating. Major minerals quantified were calcium, magnesium, potassium and sodium, with potassium having the highest concentration that ranged from 219-248 mg/100 g FW. The major organic acids identified were malic (304.7-393.9 mg/100 g FW) and succinic (120.4-316.3 mg/100 g FW). Phenolics from the three fruit varieties were extracted employing water, ethanol:formic acid:water, and methanol:formic acid:water (70:2:28 v:v) mixtures. The ethanol:formic acid:water (EFW) extracts from all samples were found to have the highest phenolic concentrations as determined by total phenolic content analysis. Based on total phenolic chromatographic index (TPCI) results as determined by high performance liquid chromatography with photodiode array detection (HPLC-PDA), the Northline variety had the highest TPCI at 504.2 mg/100 g FW. This variety was also shown to have the highest antioxidant activities by both the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2´-azinobis-3-ethylbenzthiazoline-sulphonic acid (ABTS) radical scavenging assays, of 23.1 1/IC50/100 mg FW and 327.5 mM TEAC/100 mg FW, respectively. Solid phase extraction (SPE) using Amberlite® XAD16N resin and aqueous ethanol (40, 70 and 100%) was employed to produce phenolic fractions from the three fruit varieties. It was found that hydroxybenzoic acids eluted in the 40% ethanol fraction; hydroxycinnamic acids and anthocyanins eluted in the 70% ethanol fraction; and anthocyanins, flavanols and flavonols eluted in the 100% ethanol fraction. The 70% ethanol fraction had the highest TPCI and DPPH/ABTS radical scavenging abilities for all saskatoon berry varieties. Wet and dry pomace from commercial saskatoon berry juice production had TPCI values of 404.2 mg/100 g and 250.0 mg/100 g, respectively. The ABTS values of wet and dry pomace were found to be 304.8 and 327.8 mM TEAC/100 mg, while the DPPH results were 19.4 and 16.8 1/IC50/100 mg FW, respectively. These results show that pomace from commercial juice production was a good source of phenolics with high antioxidant capacities. Results from laboratory scale juice production of the Northline variety employing commercial conditions (i.e. time, temperature, and enzymes and dosages) showed that 29% of the phenolics remained in the pomace after juice production as determined by TPCI analysis

    Organophosphorus Pesticides Analysis

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    An inexpensive, microcomputer-based, video densitometer for quantitating thin-layer chromatographic spots

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    An inexpensive video densitometer based on an Apple II microcomputer using commercially available components was developed. The device was used to quantitate charred lipid and colored spots on thin-layer chromatography plates. The method is useful for lipid samples weighing 0.1 to 4 [mu]g on high-performance plates and 1 to 20 [mu]g on ordinary plates. The software automatically corrects for baseline drift due to dirt or nonuniformity in the plate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25173/1/0000611.pd

    QuEChERS: a sample preparation for extraction of carbaryl from rat feces

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    Carbamate compounds are an important group of cholinesterase inhibitors. There is a need for creating awareness regarding the risks of the inadequate carbamate use in the residential areas due to potential adverse human effects. Carbaryl is a commonly used pesticide worldwide. A simple, fast, and high throughput method was developed employing liquid chromatography with fluorescence detector to determine carbaryl residues in rat feces. The extraction was performed by using a rapid, easy, cheap, effective, reliable, and safe (QuEChERS) method, using acetonitrile as the extracting solvent. The parameters for the performance of the extraction method were optimized, such as ratio of mass of sample per volume of extraction solvent, QuEChERS content, and cleanup columns. Linear response was obtained for all calibration curves (solven and matrix-matched) over the established concentration range (5 500 mg/L) with a correlation coefficients higher than 0.999. The achieved recovery was 97.9% with relative standard deviation values of 1.1% (n D 4) at 167 mg/kg fortified concentration level and the limits of detection and quantification were 27.7 and 92.3 mg/kg respectively

    Studies in hydrogel microfluidics and development of low cost imaging for quantitative TLC in the undergraduate teaching laboratory

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    Microfluidics is the micrometer-scale manipulation of small volumes of fluids, which allows the miniaturization of benchtop biological and chemical assays. Small volume analyses provide analytical and practical advantages like high precision, temporal resolution, throughput, speed, portability, and low cost and reagent consumption. Microfluidics is particularly suited to studying microscale problems, and so has been used to model biological systems like the microvasculature. Such biomimics have been produced in many ways, including 3-D printing and self-organization through various extracellular matrices. An attempt at templating a perfusable microvessel mimic through hydrogel in a microfluidic device is described in chapter 2.Thin-layer chromatography (TLC) is a simple microfluidic separation technique offering much lower cost, time requirement, and reagent consumption than other separation methods. These attributes make TLC attractive for use in point-of-care, preparatory, and pedagogical applications, and it is often used qualitatively in these ways. TLC can be quantitative as well, but generally requires expensive imaging instrumentation that can be cost-prohibitive. A simple and inexpensive quantitative TLC imaging experiment for the determination of counterfeit drugs was developed for undergraduates, and is described here in chapter 3. This imaging method was expanded for the quantitation of amino acids utilizing a cellphone camera as described in chapter 4, and future directions for the method are discussed in chapter 5
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