Severino Ghini

Multiresidual method for the gas chromatographic analysis of pesticides in honeybees cleaned by gel permeation chromatography.

The analysis of several organophosphorus and carbamate pesticide residues in the bodies of honeybees using gas chromatography (GC) and gel permeation chromatography (GPC) clean-up is described. Freeze-dried or lyophilized insect samples were blended with diatomaceous earth (Extrelut) then underwent elution with methylene chloride. This extraction method has shown good recovery on various spike standard levels. Samples are cleaned up by GPC with a Bio Beads SX 3 column and a cyclohexane-ethylacetate (1:1) eluant. Organophosphorus and carbamate compounds are quantified using capillary gas chromatography. Good linearity ranges were observed for all compounds. The extraction process was rapid and results were good, despite the complexity of the matrix on which it was applied. It allowed a reduction both in cost and the consumption of solvents, thereby safeguarding the health of the analyst and the environment. Environmental monitoring using bees was confirmed to be a valid procedure.

Application of matrix solid phase dispersion to the determination of imidacloprid, carbaryl, aldicarb, and their main metabolites in honeybees by liquid chromatography-mass spectrometry detection

A method based on matrix solid phase dispersion (MSPD) using C18 as dispersant and dichloromethane-methanol as eluent and liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) has been developed for the simultaneous determination of imidacloprid, 6-chloronicotinic acid, carbaryl, aldicarb, aldicarb sulfoxide, and aldicarb sulfone in honeybees. The proposed method was compared with liquid-liquid extraction (LLE) combined with LC-APCI-MS analysis. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. Recovery studies were performed at different fortification levels. Average recoveries by MSPD varied from 61% of 6-chloronicotinic acid to 99% of aldicarb sulfoxide and relative standard deviations were equal or lower than 14%. Limit of detections ranged from 0.004mgkg(-1) for imidacloprid to 0.09mgkg(-1) for 6-chloronicotinic acid. Results obtained by both methods were compared, MSPD showed higher recoveries and sensitivity than LLE for most pesticides, except for carbaryl. As MSPD is easier to perform, faster, consumes less sample and organic solvents than LLE, its application for pesticide analysis in honeybees is suggested.

Determination of organophosphorus pesticides in honeybees after solid-phase microextraction.

A method based on solid-phase microextraction (SPME) followed by gas chromatography with nitrogen-phosphorus detection was developed for the purpose of determining 18 organophosphorus pesticide residues in honeybee samples (Apis mellifera). The extraction capacities of polyacrylate and poly(dimethylsiloxane) fibers were compared. The main factors affecting the SPME process, such as the absorption time profile, salt, and temperature, were optimized. The method involved honeybee sample homogenization, elution with an acetone:water solution (1:1) and dilution in water prior to fiber extraction. Moreover, the matrix effect on the extraction was evaluated. In samples spiked at the 0.2 mg kg(-1) level, the coefficient variation was between 1 and 13% and the detection limits were below 10 microg kg(-1). The SPME procedure was found to be quicker and more cost-effective than the solvent extraction method commonly used. The method was applied successfully to environmental screening. Parathion methyl was detected and confirmed in the real samples analyzed.

Chemiluminescent flow sensor for the determination of Paraoxon and Aldicarb pesticides

Abstract A chemiluminescence-based flow method for the determination of some organophorus and carbamate pesticides based on inhibition of acetylcholinesterase was developed. Acetylcholinesterase in solution or immobilized on methacrylate beads (Eupergit C) was coupled to choline oxidase and peroxidase immobilized on Eupergit C. In this system choline formed by acetylcholinesterase was oxidized by choline oxidase and the H 2 O 2 produced was determined via the luminol/peroxidase luminescent reaction. The detection limits (3 σ) for Paraoxon and Aldicarb were 0.75 μg 1 −1 and 4 μg 1 −1 , respectively, when soluble acetylcholinesterase was used under the following optimized experimental conditions: 56 μM luminol in working solution, sample volume 60 μl, flow-rate 0.3 ml min −1 and 60 min incubation time. The flow sensor device using all the three enzymes in the immobilized form had a higher detection limit of 125 μg 1 −1 for Paraoxon. The mid-range relative standard deviation ( n =10) using 1 mM standard substrate solution was 3.7%. The recovery from contaminated samples (soil, vegetables) varied from 81 to 108%. The results obtained by the developed methods were in good agreement with those obtained by a commonly used colorimetric test.

Honey bees and their products as indicators of environmental radioactive pollution

Samples of honey, pollen and honey bees have been collected in some regions of Italy after the Chernobyl accident, and subjected to gamma spectrometry in order to assess their possible use as markers of the radioactive environmental contamination. Pollen has resulted in the best indicator, since it reflects exactly the air contamination and therefore it is suitable for obtaining a map of fallout. Also bees can be used for the purpose, even if their collection is more difficult, whereas honey gives only an indication.

Direct quantitative chemiluminescent assays for the detection of viral DNA

Abstract A direct chemiluminescent dot blot hybridization assay for the detection of B19 Parvovirus DNA is described. The hybridization test uses digoxigenin-labelled probes which are immunoenzymatically revealed by anti-digoxigenin Fab fragments conjugated with alkaline phosphatase (AP) or with horseradish peroxidase (HRP). The chemiluminescent signal, obtained from an enzyme-triggerable dioxetane for Ap or from the luminol-amplified reaction for HRP, is directly measured by placing the spot cut from the nylon solid support in a cuvette and inserting it into a luminometer. Both the enzymatic systems using this direct chemiluminescent detection gave reproducible results for calibration graphs and positive clinical samples, with higher reproducibility and long lifetime emission (15 days) for the AP-dioxetane system. This direct method allowed up to 0.2 pg of homologous target DNA to be revealed. The results obtained with the quantitative chemiluminescent assay described were compared with those obtained in a hybridization assay with colorimetric detection or photographic chemiluminescent detection and good agreement among the tests was found.

Bioluminescent flow sensor for D-(-)-lactate

Abstract Previously, a bioluminescent flow sensor was developed for the determination of the content of l -lactate in biological fluids (serum, plasma, ventricular fluid) by monitoring the reduced form of nicotinamide adenine dinucleotide (NADH), produced by immobilized lactate dehydrogenase (LDH), with bacterial bioluminescent enzymes immobilized on a separate nylon coil. Based on a similar scheme, a sensor has now been developed for d -(−)-lactate. The co-immobilization of alanine aminotransferase (ALT) with d -LDH improved the lactate transformation to 40–60%. The response was linear from 1 to 100 μmol 1 −1 at 25 °C for the LDH-ALT reactor. The intra- and inter-assay relative standard deviations were less than 75% and the recoveries ranged from 93 to 106%. The results agreed well with those obtained with a spectrophotometric method and applications to d -(−)-lactate determination in serum, milk and microorganism extracts are reported together with those for l -(+)-lactate.

Continuous flow analyses of nadh using bacterial bioluminescent enzymes immobilized on nylon

Abstract A continuous flow bioluminescent method for NADH analysis has been developed using nylon 6 as a solid support. Bacterial luciferase and NAD:FMN oxidoreductase are covalently co-immobilized to a nylon coil (1 m × 1.0 mm ID). The reactor (nylon coil) is placed in front of a photomultiplier tube inside a luminometer linked to an air segmented continuous flow system. Response is linear from 1 to 2500 pmol/tube allowing determination of NADH at picomolar levels. Inter and intra assay precision of the method is satisfactory (5-10%). Range of sample volume injected is 5-100 μl. More than 20 samples per hour can be analyzed and no carryover was observed. The stability of the nylon immobilized enzymes is high (over 2 months) and over 500 samples can be analyzed with a few mg of enzymes.

Bioluminescent flow sensor for the determination of L-(+)-lactate

The amount of L-lactate in biological fluids (serum, plasma and cerebrospinal fluid) was determined by monitoring the reduced form of nicotinamide adenine dinucleotide (NADH) produced by immobilised lactate dehydrogenase (LDH), with bacterial bioluminescent enzymes immobilised on a separate nylon coil. The LDH catalysed the reaction of L-lactate with NAD; this reaction took place in a nylon coil that preceded the coil for the bioluminescent detection. The co-immobilisation of alanine aminotransferase (ALT) with LDH improved the lactate transformation by 117-183%. The response was linear from 0.1 to 50 micron mol l(-1) at 25 degrees C for the LDH - ALT reactor. The intra- and inter-assay coefficients of variation were less than 5% and the recoveries ranged from 93 to 106%. The results agreed well with those obtained with a spectrophotometric method and with the normal reference values.

Quantification of Thiram in Honeybees: Development of a Chemiluminescent ELISA

Abstract A Chemiluminescence Enzyme‐Linked Immuno‐Sorbent Assay (CL‐ELISA) for determination and quantification of the fungicide thiram in honeybees was developed in an indirect competitive format. The assay was optimized by determining: the optimal coating conjugate concentration and anti‐thiram antiserum dilution, the effect of the incubation time on the competitive step, the tolerance to organic solvents. The IC50 and the limit of detection (LOD) values were 60 ng mL−1 and 9 ng mL−1, respectively, similar to those of colorimetric ELISA with a calibration range of 9–15,000 ng mL−1. Cross reactivity of some related compounds such as some dithiocarbamates, a thiocarbamate, the ethylenethiourea and the tetramethylthiourea were tested. The assay was then applied to honeybees sample extracts obtained by using the liquid‐liquid extraction or the graphitized carbon‐based solid phase extraction. The calibration curves in honeybee extracts from liquid‐liquid procedure gave an IC50 of 141 ng mL−1 and a LOD of 17 ng mL−1. In case of extracts obtained by SPE these values were 139 ng mL−1 and 15 ng mL−1, respectively. The average recovery value from honeybee extracts spiked with 75 ng mL−1 of thiram was 72% for SPE, higher than for liquid‐liquid extraction (60%). On the opposite, when the honeybees were directly spiked with 2 and 10 ppm the average recovery was higher for liquid‐liquid extraction (54%), than for SPE (31%). Finally, the assay was applied to honeybee samples collected during monitoring activities in Italy and Russia.