Paolo Cabras

Solid-phase extraction and high-performance liquid chromatographic determination of organic acids in honey

Abstract A high-performance liquid chromatographic method is reported that allows the determination of organic acids in honey after sample purification by solid-phase extraction. The chromatographic separation was achieved with two Spherisorb ODS-1 S5 columns connected in series and sulphuric acid (pH 2.45) as the mobile phase. The average recoveries of the acids ranged from 89% to 104% and the detection limits from 0.002 to 3 ppm (w/w).

Control of Postharvest Diseases of Fruit by Heat and Fungicides: Efficacy, Residue Levels, and Residue Persistence. A Review

Extensive research has been done in recent years to reduce the heavy dependence on chemical fungicides to control postharvest diseases and disorders of horticultural crops. Alternative strategies were based on improved cultural practices, biological control, plant-defense promoters, and physical treatments such as UV illumination, radiofrequency treatment, heat therapy, and storage technologies. Among these, postharvest heat treatments such as hot water dips, short hot water rinsing and brushing, and hot air conditioning have reduced rot development and enhanced fruit resistance to chilling injury in sensitive cultivars while retaining fruit quality during cold storage and shelf life. Additive or synergistic increases in effectiveness were observed by integrating heat therapy with various chemical compounds, thus leading to significant reductions in the application of active ingredients to protect produce from decay. This paper highlights the knowledge on this topic with emphasis on heat therapy effects and factors affecting the uptake, persistence, and performance of fungicide residues when they are applied in combination with hot water.

Phenolic compounds in virgin olive oils I. Low-wavelength quantitative determination of complex phenols by high-performance liquid chromatography under isocratic elution

Abstract An HPLC method that allows the determination of complex phenolic compounds at low λ (225 nm) after solid-phase extraction from virgin olive oils is reported. The separation was achieved on ODS-2, ODS-1 and C8 columns in eluting mixtures 10−3 M H2SO4CH3CN employed with different ratios. The method was employed for the quantitative determination of phenolic compounds in oils. It allows the presence of some new unknown compounds to be shown. The preliminary spectroscopic data of these compounds, probably phenolic, are reported. The reactivity with protic solvents of the deacetoxy oleuropeine aglycon is discussed.

Methyl Syringate: A Chemical Marker of Asphodel (Asphodelus microcarpus Salzm. et Viv.) Monofloral Honey

During the liquid chromatographic study of the phenolic fraction of monofloral honeys was detected in the asphodel honey ( Asphodelus microcarpus Salzm. et Viv.) chromatogram a distinctive peak not detected in other monofloral honeys such as Arbutus unedo L., Hedysarum coronarium , Eucalyptus spp., and Galactites tomentosa . After thin layer chromatography (TLC) purification and characterization by NMR and LC-MS/MS, the compound was identified as methyl syringate (MSYR) and confirmed against an original standard. Levels of MSYR were measured in honeys of 2005, 2006, and 2007 by HPLC-DAD analysis. Level determination of MSYR was repeated in 2008 for 2006 and 2007 honeys to evaluate chemical stability of this phenolic compound. Levels of MSYR measured 1 year after the sampling did not show significant statistical differences (p < 0.05). The stability of MSYR was also confirmed by 12 asphodel honey samples collected in 2005 that showed amounts of methyl syringate comparable with those found in fresh honey. For the evaluation of MSYR origin, samples of nectars were collected from flowers and the content of MSYR was measured. Levels of MSYR in honeys are originated from the nectar with an average contribution of the nectar to the honey of 80%. Melissopalinological analysis did not allow the attribution of the honey monofloral origin because levels of asphodel pollen were <6% for all analyzed samples. Previously reported levels of MSYR for robinia, rape, chestnut, clover, linden blossom, dandelion, sunflower, thyme, manuka, and fir honeys were <5 mg/kg. For this reason, a minimum level of 122.6 mg/kg for MSYR in asphodel honeys can be considered as a chemical marker and, unlike the melissopalynological analysis, can be used for the origin attribution and to evaluate the percent of asphodel nectar in the honey.

Residues of azoxystrobin, fenhexamid and pyrimethanil in strawberry following field treatments and the effect of domestic washing.

Residues of the pesticides azoxystrobin, fenhexamid and pyrimethanil were determined in strawberry after field treatment. The effect of ‘home’ washing with tap water and a commercially available vegetable detergent on residue levels was also studied. After treatment, azoxystrobin and pyrimethanil residues on strawberry were on average 0.55 and 2.98 mg kg−1, respectively, values below the maximum residue level (MRL) fixed by the European Union (2.0 and 5 mg kg−1, respectively), while fenhexamid residues were on average 2.99 mg kg−1, which is very close to the MRL of 3.0 mg kg−1, but some samples were over the MRL. Thereafter, all residues declined, with a half-life of about 8 days (azoxystrobin and fenhexamid) and 4.8 days (pyrimethanil). Washing the fruit with tap water reduced the residues of azoxystrobin and fenhexamid but did not affect pyrimethanil residues. Finally, when fruits were washed with a commercial detergent, greater amounts were removed (about 45% of azoxystrobin and pyrimethanil and 60% of fenhexamid).

Simplified multiresidue method for the determination of organophosphorus insecticides in olive oil

Abstract A simple and rapid method for the determination of 13 organophosphorus insecticides and theie metabolites in olive oil by GC is described. The pesticide was extracted from oil with acetonitrile and no cleanup was needed. GC-nitrogen-phosphorus detection response factors of pesticides were affected by solvents and coextractive substances. Pesticides in hexane showed on average higher response factors. Standards were prepared in the residue-free oil extract solubilized in hexane to handle effects of matrix and solvent. The low amount of coextractive substances does not decrease the column efficiency, even after a few hundred analyses. Recovery at three fortification levels (ca. 0.1, 1.0 and 3.0 mg/kg) ranged from 74 to 118%, with coefficients of variation ranging from 1 to 16.

Floral Markers of Strawberry Tree (Arbutus unedo L.) Honey

Strawberry tree honey, due to its characteristic bitter taste, is one of the most typical Mediterranean honeys, with Sardinia being one of the largest producers. According to specific chemical studies, homogentisic acid was identified as a possible marker of this honey. This work, based on HPLC-DAD-MS/MS analysis of strawberry tree (Arbutus unedo L.) honeys, previously selected by sensory evaluation and melissopalynological analysis, showed that, in addition to the above-mentioned acid, there were other high levels of substances useful for the botanical classification of this unifloral honey. Two of these compounds were isolated and identified as (+/-)-2-cis,4-trans-abscisic acid (c,t-ABA) and (+/-)-2-trans,4-trans-abscisic acid (t,t-ABA). A third compound, a new natural product named unedone, was characterized as an epoxidic derivative of the above-mentioned acids. Structures of c,t-ABA, t,t-ABA, and unedone were elucidated on the basis of extensive 1D and 2D NMR experiments, as well as HPLC-MS/MS and Q-TOF analysis. In selected honeys the average amounts of c,t-ABA, t,t-ABA, and unedone were 176.2+/-25.4, 162.3+/-21.1, and 32.9+/-7.1 mg/kg, respectively. Analysis of the A. unedo nectar confirmed the floral origin of these compounds found in the honey. Abscisic acids were found in other unifloral honeys but not in such high amount and with a constant ratio of about 1:1. For this reason, besides homogentisic acid, these compounds could be used as complementary markers of strawberry tree honey.

Liquid chromatography-tandem mass spectrometric ion-switching determination of chlorantraniliprole and flubendiamide in fruits and vegetables.

The anthranilic and phthalic diamides, chlorantraniliprole (CAP) and flubendiamide (FLU), respectively, represent a new class of very effective insecticides that activate the ryanodine-sensitive intracellular calcium release channel (ryanodine receptor). This paper reports an analytical method for the simultaneous determination of the two insecticides on fruits and vegetables by liquid chromatography-electrospray tandem mass spectrometry operated in the positive and negative ionization switching mode. The two diamides were extracted with acetonitrile and separated on a Zorbax Column Eclipse XDB C8 (4.6 mm x 150 mm i.d., 3 microm) by isocratic elution with a mobile phase consisting of acetonitrile and water with 0.1% formic acid pumped at a flow rate of 0.4 mL/min. The diamides were selectively detected by multiple reaction monitoring for transitions of proton adduct precursor ions simultaneously: positive m/z 484.3-->285 for CAP, m/z 445.5-->169 for internal standard, and negative m/z 681.4-->253 for FLU. For CAP calibration in the positive mode was linear over a working range of 2 to 1000 microg/L with r > 0.992. The limit of detection (LOD) and limit of quantification (LOQ) for CAP were 0.8 and 1.6 microg/kg, respectively. For FLU in the negative mode the corresponding values were 1-1000 microg/L for linear working range, with r > 0.996 and 0.4 and 0.8 microg/L for LOD and LOQ, respectively. Moreover, the presence of interfering compounds in the fruit and vegetable extracts was found to be minimal. Due to the linear behavior of the MS detector response for the two analytes, it was concluded that the multiple reaction transitions of molecular ions in the ion-switching mode can be used for analytical purposes, that is, for identification and quantification of diamides in fruit and vegetable extracts at trace levels.

Influence of Postharvest Hot Water Treatment on Nutritional and Functional Properties of Kumquat (Fortunella japonica Lour. Swingle Cv. Ovale) Fruit

The present study investigated the influence of a hot water dip (HWD) for 2 min at 50 degrees C, a standard and effective treatment for postharvest decay control of citrus fruit, on the nutritional and health-related properties of kumquats. The results show that most of the parameters examined, including titratable acidity, soluble solids content, maturity index, glucose, fructose, sucrose, ascorbic acid, dehydroascorbic acid, alpha- and gamma-tocopherols, beta-carotene, zeaxantin, rhoifolin, and antioxidant activity, were not significantly affected by treatment. The levels of beta-cryptoxanthin, narirutin, and total flavonoids increased after HWD, whereas lutein and total phenols decreased. The concentration of the essential oil and the relative percentage of the individual components of the essential oil were not affected by HWD except for the minor compound p-menta-1,5-dien-1-ol, which increased after HWD. After storage, lower levels of glucose, total sugars, beta-carotene, beta-cryptoxanthin and lutein were recorded in HWD fruit. A decrease in antioxidant activity and increases in alpha-tocopherol and total vitamin E were found both in control and HWD fruit. The influence of HWD at 50 degrees C for 2 min on individual nutraceuticals and health-related properties was thus generally low and may depend on storage conditions.

Chilling injury and residue uptake in cold-stored 'Star Ruby' grapefruit following thiabendazole and imazalil dip treatments at 20 and 50°C.

‘Star Ruby’ grapefruit (Citrus paradisi Macf.) were harvested from November through June and subjected to a 3-min dip in water at room temperature (20°C) with or without 1200 or 200 mg:l imazalil (IMZ) or thiabendazole (TBZ) at 50°C. Fruit were then stored at 2°C and 90‐95% relative humidity (RH) for 6 weeks and 1 additional week at 20°C and approximately 80% RH to simulate a marketing period (SMP). Fruit harvested in April and June and treated with 1200 mg:l TBZ at room temperature or with 200 mg:l at 50°C contained higher levels of TBZ residue than fruit picked in November and January. Fruit uptake of IMZ was not affected by harvest date. Within each date, conventional treatments with IMZ or TBZ fungicides at room temperature and treatment at 50°C produced similar levels of residues in most samples. Susceptibility to chilling injury (CI) was highest in fruit harvested in November and January, lower in April and negligible in June. Water dips at 50°C significantly reduced CI, the extent depending on harvest date and storage duration. The influence of 1200 mg:l IMZ dips at 20°C on CI control was not significant in most samples. Treatments with 200 mg:l IMZ at 50°C produced effects in CI control similar to that of water dips at 50°C. Beneficial effects were also achieved after treatment with 1200 mg:l TBZ at 20°C, although its efficacy in reducing CI was markedly improved with reduced doses (200 mg:l) at 50°C.