Determination of thiabendazole in fruit juices by a new monoclonal enzyme immunoassay

A competitive, indirect enzyme-linked immunosorbent assay (ELISA) for thiabendazole has been developed and applied to the analysis of fruit juices spiked with this fungicide. The immunoassay is based on a new monoclonal antibody derived from a hapten functionalized at the nitrogen atom in the 1-position of the thiabendazole structure. To our knowledge, such a structure has not been previously used to obtain antibodies to thiabendazole. The I50 value and the detection limit of the ELISA for standards were 0.2 and 0.05 ng/mL, respectively. Fruit juices were analyzed by diluting samples in assay buffer, without extraction or cleanup. Samples were not even centrifuged or filtered to remove fruit pulp. Under these conditions, the immunoassay was able to accurately determine thiabendazole down to 1 ng/mL in orange and grapefruit juices, down to 5 ng/mL in banana juice, and down to 20 ng/mL in apple and pear juices. Sensitivity differences of the ELISA were caused by the minimum dilution required by each juice to minimize matrix effects: 1/10 for orange and grapefruit juices, 1/50 for banana juice, and 1/100 for apple and pear juices. In an attempt to further increase the sensitivity of the immunoassay for matrixes showing the strongest interferences, apple and pear juices spiked with thiabendazole at low levels (1-20 ng/mL) were extracted with ethyl acetate before analysis. This simple procedure entailed a significant reduction of matrix effects, which in fact allowed us to determine accurately as low as 5 ng/mL thiabendazole in apple and pear juices. Irrespective of whether samples were analyzed by the direct dilution method or after extraction, the simplicity, sensitivity, and sample throughput of this monoclonal immunoassay makes it a very convenient method for the routine monitoring of thiabendazole residues in fruit juices.     

Spectrophotometric determination of ascorbic acid in pharmaceutical preparations and fruit juices

Conditions were established for the determination of ascorbic acid using phsophovanadotungstic acid as reagent. The method was applied to the determination of ascorbic acid in pure form, pharmaceutical preparations and fruit juices. The method is sensitive (2-24 micrograms ml-1 of ascorbic acid) and rapid and tolerates the presence of common ingredients usually found in fruit juices. The results obtained with the proposed method showed good agreement with those given by the standard method.     

Effect of storage temperature on degradation of methidathion in fortified orange and peach juices

The effect of storage temperature on methidathion degradation in orange and peach juices was studied. The insecticide was aseptically added to packed orange and peach juices, which were stored at 40, 15, and 0 degrees C. Samples were taken at regular intervals and examined for residues of methidathion. Residues were determined with a simple gas chromatographic method; recoveries of methidathion from orange and peach juices ranged from 88.1 to 110% for both juices, and the limits of determination were 0.004 and 0.003 mg/kg, respectively. The experimental data were used to evaluate rate constants, half-lives, and times required to reach legal maximum residue limits, and activation energies for the decomposition of methidathion in orange and peach juices. Storage of fruit juices in refrigerated rooms greatly extended the half-life of methidathion beyond that of methidathion in samples stored at higher temperatures. Half-life values for methidathion in orange and peach juices, respectively, were 4.1 and 3.8 days for storage at 40 degrees C, 115 and 113 days for storage at 15 degrees C, and 330 and 385 days for storage at 0 degrees C. Activation energies for methidathion degradation in orange and peach juices were 22.6 and 21.7 kcal/mol, respectively.     

Simultaneous determination of sorbic and benzoic acids in commercial juices using the PLS-2 multivariate calibration method and validation by high performance liquid chromatography

A new method to determine a mixture for preserving sorbic and benzoic acids in commercial juices is proposed. The PLS-2 model was obtained preparing 40 standard solutions adding concentration of sorbic and benzoic acid to filtered natural juices of apple, lemon, orange and grapefruit. The concentration of analytes in the commercial samples was evaluated using the obtained model by UV spectral data. The PLS-2 method was validated by high performance liquid chromatography (HPLC), finding a relative error less than 12% between the PLS-2 and HPLC methods in all cases.     

High-performance liquid chromatographic analysis of free amino acids in fruit juices using derivatization with 9-fluorenylmethyl-chloroformate

A simple, rapid, and reliable reversed-phase high-performance liquid chromatographic method for the analysis of 16 amino acids of main interest in commercial fruit juices (pear, orange, grapefruit, pineapple, peach, and apricot) is described. No sample cleanup is required. The pH of the fruit juices is adjusted to alkaline value (8.5) using 200 mM borate buffer, then amino acid is converted to stable derivatives using 9-fluorenylmethyl-chloroformate. The excess of derivatization reagent is removed by a hydrophobic amine, 1-amino-adamantane hydrochloride. The derivatization procedure is simple, fast, and described in detail. Amino acids are detected at 263 nm and eluted within 35 min. The calibration, precision (< or = 6.1%), and recovery (102% +/- 4%) of the method are reported. The conditions of separation are optimized; however, serine partially overlapped with aspartic acid. The amino acid profile of fruit juices is consistent with data from the literature.     

An optimized direct method for the determination of carboxylic acids in beverages by HPLC

Summary A direct method for the simultaneous determination of tartaric, malic, lactic, acetic, citric, shikimic, fumaric and succinic acids in fruit juices and wines by isocratic reversed phase HPLC is reported.The variables (pH, ionic strength, flow and temperature) have been optimized by a modification of the original simplex method. The separation factor (s) and calibrated resolution product (r^*) have been used as criteria for selectivity optimization. After validation, the method has been applied to the determination of carboxylic acids in apple, orange and lemon juices, white and red wines and musts during the fermenation process.     

Use of high-performance liquid chromatography with diode array detection coupled to electrospray-Qq-time-of-flight mass spectrometry for the direct characterization of the phenolic fraction in organic commercial juices

We have developed a direct method for the qualitative analysis of polyphenols in commercial organic fruit juices. The juices were diluted with water (50/50), filtered and directly injected. The analysis of phenolic compounds was carried out by reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to photodiode array detection (DAD) and electrospray ionisation-Qq-time-of-flight mass spectrometry (ESI-Qq-TOF-MS). A unique gradient program has been optimized for the separation of several phenolic classes and the analysis time was only 5 min. The fruit juice samples were successfully analysed in positive and negative ionisation modes. In positive mode the anthocyanins were identified whereas the vast majority of polyphenols were identified using the negative ionisation mode. The sensitivity, together with mass accuracy and true isotopic pattern of the Qq-TOF-MS, allowed the identification of the phenolic compounds. Moreover, the advantage of the proposed method is the combined search of MS and MS/MS spectra, which improves the identification of compounds considerably, reducing ambiguities and false positive hits. Therefore the total fragmentation of the compound ion leading to the aglycone ion or other fragments was corroborated by MS–MS. The method was successfully employed to characterize diverse phenolic families in commercially available organic juices from four different fruits and consequently could be used in the future for the quantification purposes to compare different content of polyphenols in juices.     

液相色谱-串联质谱法快速筛查测定浓缩果蔬汁中的156种农药残留

建立了浓缩果蔬汁中156种农药多残留的液相色谱-电喷雾串联质谱(LC-ESI-MS/MS)测定方法。样品用1%醋酸乙腈溶液萃取,经Waters Sep-Pak Vac固相萃取柱净化,乙腈-甲苯(体积比为3∶1)洗脱,旋转蒸发浓缩,用乙腈-水（体积比为3∶2）溶解,以Agilent ZORBAX SB-C18色谱柱分离,以电喷雾电离串联质谱在正离子多反应监测(MRM)模式下进行测定。对156种农药在5种浓缩果蔬汁(橙汁、苹果汁、葡萄汁、白菜汁、胡萝卜汁)中两个添加水平下的回收率进行了测定,回收率范围为57.2%～122.7%,相对标准偏差范围为0.9%～19.8%。方法的检出限(S/N=3)和定量限(S/N=10)范围分别为0.10～56.77 μg/kg和0.33～189.23 μg/kg。该方法样品前处理简单、快速、分析时间短,灵敏度、准确度和精密度均符合农药多残留检测技术的要求,适用于苹果汁、橙汁、葡萄汁、白菜汁、胡萝卜汁等浓缩果蔬汁中156种农药多残留的快速筛查测定。     

Study on the Kinetics of Vitamin C Degradation in Fresh Strawberry Juices

Vitamin C is an essential nutrient needed for maintaining the human health. Strawberry fruit have a relatively high content of vitamin C, which is around 40-70 mg/ 100 g strawberries. However, vitamin C which is also known as ascorbic acid is easily degraded during storage. The objective of this research is to study the kinetics of degradation of vitamin C in fresh strawberry juices upon storage and to investigate the effect of storage temperatures and sugar addition on the ascorbic acid loss in strawberry juices. Four different types of fresh strawberry juices were prepared, namely A, B, C, and D. Juices A and C were stored at a room temperature of 28 °C, while samples B and D were stored at a refrigerated temperature of 8 °C. Furthermore, juices A and B were prepared without sugar addition, while sugar was added to juices C and D. The concentration of ascorbic acid in the juice was analyzed using iodimetric titration method. It was monitored every one hour for 8 hours of storage for the kinetics of ascorbic acid degradation study. The results showed that the degradation reaction of vitamin C followed zero-order kinetic models in all types of juices. The degradation reaction rate constants obtained for juices A, B, C, and D were 4.42; 3.63; 2.32; and 1.85 mg vitamin C/(100 ml. h), respectively. The activation energy for the vitamin C degradation in fresh strawberry juices with sugar and without sugar addition was estimated to be 1.90 kcal/ mol and 1.65 kcal/ mol, respectively. In conclusion, the storage at a lower temperature combined with sugar addition could effectively slow the rate of degradation of vitamin C.     

Spectrophotometric determination of vitamin C in citrus fruits using peri-naphthindan-2,3,4-trione

Analytical and Bioanalytical Chemistry - A spectrophotometric method for the determination of vitamin C in lemon, orange, and grapefruit juices is described. It is based on the reaction with...     

超高效液相色谱-串联质谱法快速测定浓缩果汁中噻菌灵和多菌灵的残留量

建立了同时测定浓缩果汁中噻菌灵和多菌灵残留的超高效液相色谱-串联质谱快速检测法。样品用乙酸乙酯提取,以ACQUITY UPLC BEH C18色谱柱(50 mm×2.1 mm, 1.7 μm)进行超高效液相色谱分离,以电喷雾电离串联质谱正离子多反应监测(MRM)模式进行测定,以基质匹配标准溶液外标法定量。结果表明:在试验条件下,噻菌灵和多菌灵在0.5~10 μg/kg范围内线性关系良好,相关系数大于0.99,不同基质中的检出限(S/N=3)范围为0.12~0.23 μg/kg。在0.5、1.0和5.0 μg/kg 3个水平下噻菌灵和多菌灵的加标回收率为76.98%~108.7%,相对标准偏差(RSD)为2.95%~9.99%。同时,本研究对浓缩果汁中噻菌灵和多菌灵残留检测的基质效应进行了考察。本方法具有操作简便、快速、准确的特点,可用于浓缩果汁中噻菌灵和多菌灵残留量的日常检测。     

Optimization and validation of a methodology based on solvent extraction and liquid chromatography for the simultaneous determination of several polyphenolic families in fruit juices

A solvent extraction procedure of freeze-dried aliquots followed by the analysis of phenolic compounds by reversed-phase high-performance liquid chromatography (RP-HPLC) with photodiode array detection (DAD) has been developed for the analysis of polyphenolic compounds in fruit juices. This methodology is focussed on the characterization of fruit juices, mainly for quality control purposes. The effects of experimental variables, such as solvent composition and volume and time and temperature on extraction, have been studied. A unique gradient program for the separation of several phenolic classes (hydroquinones, hydroxybenzoic acids, flavan-3-oles, hydroxycinnamic acids, coumarins, flavanones, flavones, dihydrochalcones and flavonols) has been optimized, using standards of 55 commercially available phenolic compounds present in fruits, as well as representative real extracts from fruit juices. All phenolic compounds showed a high repeatability within-day (n=5) and between days (n=3) in peak area (RSD<8%) and excellent stability of their retention times. High precision was also observed in calibration slopes (RSD<8%). Detection limits ranged between 0.005 and 0.03 microg/mL for the different detected polyphenols. Complete recoveries (98-100%) were obtained for the majority of the phenolic structures of all representative phenolic families present in fruits. The method was successfully employed to measure diverse phenolic families in juices from 18 different fruits and consequently could be used for evaluate the quality of fruit juices.     

Evolving window zone selection method followed by independent component analysis as useful chemometric tools to discriminate between grapefruit juice, orange juice and blends

This study investigates the use of high resolution ¹H NMR as a suitable alternative to the standard chromatographic method for the determination of adulteration of orange juice (Citrus sinensis) with grapefruit juice (Citrus paradisi) based on flavonoid glycoside content. Fifty-nine orange juices (OJ), 23 grapefruit juices (GJ) and 10 blends (OG), obtained from local retail outlets were used to assess the performance of the ¹H NMR method. The work presented here introduces the Evolving Window Zone Selection (EWZS) function that holds promise for the automatic detection of spectral regions tailored to discriminate predefined groups. This technique was applied on the pre-processed ¹H NMR spectra of the 92 juices. Independent Component Analysis (ICA) is a good alternative to Principal Component Analysis (PCA) for recovering linearly-mixed unobserved multidimensional independent signals and has been used in this study to build supervised models that classify the samples into three categories, OJ, GJ, OG. The regions containing the known flavonoid glycoside markers were selected as well as another zone containing the signals of sucrose, α-glucose and other components that were tentatively attributed. ICA was applied on three different groups of selected variables and showed good results for both discrimination and interpretation of the signals. Up to 97.8% of the juices were correctly attributed. This method gave better results than the commonly used PCA method. In addition, the time required to carry out the ¹H NMR analysis was less than half the time of the standard chromatographic method.     

Effect of probiotication on antioxidant and antibacterial activities of pomegranate juices from sour and sweet cultivars

There is an increasing interest in using pomegranate juice as a natural antioxidant rather than synthetic compounds. In this study, the antioxidant capacities of probioticated and nonprobioticated aril juices of sweet (SWV) and sour (SV) pomegranate cultivars were determined by two different methods: ferric reducing antioxidant power (FRAP) and 1,1-diphenyl 2-picrylhydrazyl assay. Total counts of Lactobacillus casei GG increased by about 3 log in SWV and 2 log in SV juices after incubation for 48 h. Probiotication improved the antioxidant activity of SWV juice from 74.4% to 91.82%, and SV juice from 82.64% to 97.8%. Based on the FRAP value, the reducing power of the probioticated pomegranate juices was also much stronger than the nonprobioticated juices. The FRAP values for SWV and SV probioticated juices were 97.34 and 120.7 mmol L(-1), respectively, which were notably higher than 85.87 and 93.4 mmol L(-1) for SWV and SV nonprobioticated juices. Both fermentated and nonfermentated juices exhibited a potent and wide-spectrum antibacterial effect, with the highest activity against Pseudomonas aeruginosa. SV juice showed wider zones of growth inhibition. The results of this study verify for the first time that probiotication of SWV and SV pomegranate juices can add to their beneficial antioxidant activities.     

Validation of a method for the determination of multiclass pesticide residues in fruit juices by liquid chromatography/tandem mass spectrometry after extraction by matrix solid-phase dispersion

A multiresidue method was developed and validated for the determination of pesticide residues (omethoate, dimethoate, carbendazim, propoxur, thiabendazole, carbaryl, pirimicarb, azinphos-methyl, methidathion, and iprodione) in fruit juices. The samples were extracted by matrix solid-phase dispersion with diatomaceous earth and analyzed by liquid chromatography/tandem mass spectrometry. The method detection limits were <0.2 ppb for all pesticides; the relative standard deviations for analyses of samples fortified over the range of 2-50 ng/g were <9%, and the recoveries for each pesticide were all between 77 and 102%. The proposed method was used to analyze 21 commercial fruit juices; pesticide residues were found in 71% of the samples.     

Biosensor discrimination of meat juice from various animals using a lectin panel and ellipsometry

In this work, simple microcontact printed gold-wafers were used to make a lectin panel for investigation and discrimination of different meat juices from fresh meat of cattle, chicken, pig, cod, turkey and lamb. Seven different lectins were thus attached to gold surfaces using the streptavidin-biotin method. Lectins recognize and bind specifically to carbohydrate structures present on different proteins. The biorecognition was evaluated with null ellipsometry and the data obtained was related to an internal standard of lactoferrin. The data was evaluated with multivariate data analysis techniques to identify possible discrimination or grouping of data. Scanning ellipsometry was used for visualization of the binding pattern of the lectins and the meat juice proteins. The two-dimensional images obtained could be used to visualize the protein distribution, furthermore, to exclude anomalies. The results showed that the different meat juices from the six different species: cattle, chicken, pig, cod, turkey and lamb could be discriminated from each other. The results showed to be more repetitive for the mammalian meat juices. Using a simple model based on an artificial neuronal net, it was also possible to classify meat juices from the mammals investigated.     

Evaluation of pesticide residue in grape juices and the effect of natural antioxidants on their degradation rate

Various studies have been drawn toward the beneficial properties of fruit juices because they have several components, such as phenols, vitamins, and flavonoids, with antioxidant effects. However, fruit juices can also contain residues of pesticides used as standard pest control methods in crops. Many of these pesticides are degraded through oxidative mechanisms, and their persistence in juices can be enhanced by antioxidants. This study covers the degradation of four pesticides, aldicarb, demeton-S-methyl, fenamiphos, and methiocarb, to their respective sulfoxide and sulfone in grape juices, water (pH 3.5) and water (pH 3.5) with quercetin (one of the most important flavonoids of grape) added in an attempt to establish whether the presence of antioxidants can affect the degradation rate of pesticides. For this purpose, a multiresidue method based on solid-phase extraction (SPE) was developed for the simultaneous determination of these pesticides and their metabolites in commercial juices. The extraction procedure was carried out in C₁₈ columns. The subsequent elution of pesticides was performed with dichloromethane prior to the determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS), using two precursor-product ion transitions. Average recoveries for all the pesticides studied were higher than 80%, with relative standard deviations lower than 15% in the concentration range 0.005–0.05 μg/mL, and the quantification limits achieved ranged from 0.1 to 4.6 μg/L. The results demonstrated that degradation was slower in fruit juices and aqueous solutions with quercetin than in water. Several commercial grape juices were also analyzed to establish the levels of these pesticides. Methiocarb, fenamiphos, and demeton-S-methyl were found at low levels in some samples.     

High-performance liquid chromatographic determination of furfural and hydroxymethylfurfural in apple juices and concentrates

Summary A rapid and sensitive method for determining 2-furaldehyde (FUR) and 5-hydroxymethyl-2-furaldehyde (HMF) in apple juices and juice concentrates has been developed. The method for FUR and HMF involves the solid-liquid extraction of the juice by using a C-18 cartridge prior to reversed-phase separation with detection at 280 nm. The mobile phase was acetonitrile-water (8/92, v/v) at a flow rate of 1.0 ml/min. Recoveries from apple juices and juice concentrates spiked at different levels ranged from 94.1 to 104.0 (FUR) and 94.5 to 100.5 (HMF). The quantification limit for both, FUR and HMF, was 5 ppb.     

Detection of sugar addition to citrus juices by capillary GC

A method is described for the detection of citrus juices adulterated by addition of industrial sugar products. The oligosaccharides maltotriose (DP3) and maltotetraose (DP4), both of which are absent from the natural sugar profile of citrus fruits, serve as markers. The sample preparation method includes clean-up on a solid phase ODS cartridge, fractionation of DP3 and DP4 carbohydrates by LC on aminopropyl silica gel, and derivatization of the collected sugars to form the oxime-trimethylsilyl derivatives. Capillary GC analysis is performed on a 30 m × 0.32 mm i.d. polydimethylsiloxane fused silica column applying cool on-column injection and FID detection. The detection limit for maltotriose and maltotetraose is about 1 mg l^?1. Several orange and grapefruit juices were evaluated on their authenticity. Adulteration with crystalline sugar products cannot be detected with the described procedure.     

Determination of saccharides in fruit juices by capillary electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A fast method for the detection of cheap sweeteners is presented. Detecting the adulteration of foods rich in carbohydrates is complicated by the presence of variety of commercial sweeteners that are designed to match exactly the major carbohydrate profiles of these foods. Electrophoretic and mass spectrometric assays for the determination of fruit juice authenticity were developed. Capillary zone electrophoresis with indirect detection was employed to detect adulteration of juices demonstrated by the ratio of the concentrations of major low molecular mass saccharides (glucose, fructose and sucrose). Traces of oligosaccharides, which are not present in the sugar profiles of citrus fruits but are present in inexpensive sweeteners, were evaluated as the other group of target compounds. The fast determination of oligomeric starch hydrolysates in a complex matrix was tested by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and applied to orange juice. MALDI-TOFMS was shown to be a suitable method for the identification of adulteration of fruit juices by starch hydrolysates. The effects of the presence of salts and low molecular mass saccharides on the detection of oligosaccharides by MALDI-TOFMS were studied. Low molecular mass saccharides and organic acids decrease the detectability of oligosaccharides by MALDI-TOFMS, but the concentration of maltooligosaccharides present in juices sweetened with starch hydrolysates is high enough to be detected with good sensitivity.