Roberto Dommarco

Selective, solid-matrix dispersion extraction of organophosphate pesticide residues from milk

A rapid procedure has been developed that allows a single-step, selective extraction and cleanup of organophosphate (OP) pesticide residues from milk dispersed on solid-matrix diatomaceous material filled into disposable cartridges by means of light petroleum saturated with acetonitrile and ethanol. Recovery experiments were carried out on homogenized commercial milk (3.6% fat content) spiked with ethanolic solutions of 24 OP pesticides, viz., ethoprophos, diazinon, dimethoate, chlorpyrifos-methyl, parathion-methyl, chlorpyrifos-ethyl, malathion, isofenphos, quinalphos, ethion, pyrazophos, azinphosethyl, heptenophos, omethoate, fonofos, pirimiphos-methyl, fenitrothion, parathion, chlorfenvinphos, phenthoate, methidathion, triazophos, phosalone, azinphos-methyl, at levels ranging for the different OP pesticides from 0.02 mg/kg to 1.11 mg/kg. Average recoveries of four replicates were in the range 72-109% for the different OP pesticides, with relative standard deviations (R.S.D.) from ca. 1 to 19%, while dimethoate and omethoate were not recovered. Coextracted fatty material amounted to an average of about 4.0 mg/ml of milk. The extraction procedure requires about 30 min. The main advantages are that extraction and cleanup are carried out in a single step, emulsions do not occur, several samples can be run in parallel by a single operator, reusable glassware is not needed and simple operations are required.

Multiresidue analysis of organochlorine and pyrethroid pesticides in ground beef meat by gas chromatography-mass spectrometry

A multiresidue method was developed and optimized for the identification/quantification of organochlorine pesticides (OCPs) and pyrethroids (PYRs) in beef meat samples. Samples extraction was performed by an automated solvent extractor and the extracts were cleaned-up by a tandem-cartridge system consisting of an Extrelut NT3 combined with a Sep-Pack C18 cartridge and a florisil minicartridge. Analysis was finally carried out by gas chromatography coupled with quadrupole mass spectrometry (GC/MS). The performance of the method was investigated in terms of linearity, accuracy, precision, detection limit (LOD) and quantification limit (LOQ). Good linearity was obtained, with correlation coefficients (r2) higher than 0.98. Mean recoveries were found in the ranges 70–110 % and 84–99 % for the investigated OCPs and PYRs, respectively, with the exception of extremely volatile hexachlorobenzene (HCB). RSD% turned out to range from 2 to 15 %. LOQ values were in the range 0.005–0.1 mg/kg for either class of compounds. The method developed was successfully tested on 50 commercial beef meat samples from the market area of Rome (Italy), proving to be a useful tool in routine multiresidue analysis of OCPs and PYRs for monitoring purposes. None of the compounds of interest were observed above their respective LOQ.

Application of solid-phase partition cartridges in the determination of fungicide residues in vegetable samples

Disposable, ready-to-use cartridges filled with a macroporous diatomaceous material are used to extract in a single step fungicide residues with dichloromethane from aqueous acetone extracts of vegetables. This procedure takes the place of some functions (such as separating funnel partition, drying over anhydrous sodium sulphate and clean-up) usually performed by separate steps in classical schemes. Fourteen fungicides (dichloran, vinclozolin, chlorthalonil, triadimefon, dichlofluanide, procymidone, hexaconazole, captan, folpet, ditalimfos, iprodione, captafol, pyrazophos and fenarimol) were determined using the described procedure with recoveries between 83 and 107% at spiking levels ranging for the different compounds from 0.04 to 0.40 mg/kg. Crops subjected to the described procedure included lettuce, strawberry, apple, yellow pepper and peach, and gave extracts containing a mass of co-extractives between 5 and 30 mg. Compared with classical schemes, the described procedure is simple, less labour intensive, allows parallel handling of several extracts and does not require preparation and maintenance of equipment. Troublesome emulsions such as those frequently observed in separating funnel partitioning do not occur.

Solid-phase extraction for multi-residue analysis of pesticides in honey

A fast and simple multi-residue method for the analysis of 15 organophosphorus (OP), 17 organochlorine (OC), 8 pyrethroids (PYR), 12 N-methyl-carbamate (NMC) pesticide residues and bromopropylate in honey is presented. Ready–to–use EXtrelut®NT 20 column, eluted with dichloromethane, was used to extract the pesticide residues from the aqueous-acetone honey sample, obtaining a clean extract directly analyzable. Determination was carried out by gas chromatography (GC) coupled with flame photometric detector (FPD) for OP compounds and by GC coupled with mass spectrometry detector (MSD) for OC and PYR pesticides and bromopropylate. The NMC pesticides were analysed by liquid chromatography-double derivatization coupled with spectrofluorimetric detector (LC/DD/Fl). This method allows the determination of the 53 pesticide residues at low concentrations (0.0005–0.074 mg/kg) and can be used to assess the compliance with the Maximum Residues Levels (MRLs) set by the European Union. The performance of the method was evaluated and specificity, linearity, recovery, repeatability, reproducibility, limit of quantification (LOQ) and limit of detection (LOD) were determined. A good linearity (r2⩾ 0.99) was found in the range 0.0005–0.074 mg/kg for the majority of the compounds studied. Most of the pesticides had recoveries in the range 70–103 % and values of relative standard deviation (RSD) < 20 for repeatability and reproducibility, showing good accuracy and precision of the method. Aldicarb partially degraded in aldicarb sulphoxide during the analytical procedure, giving anomalous values. The LOQ for all pesticides investigated was from 0.0005 to 0.025 mg/kg while the LOD ranged from 0.0002 to 0.008 mg/kg.

Solid-matrix partition for separation of organochlorine pesticide residues from fatty materials

A fast, single step and efficient partition between n-hexane and acetonitrile on ready-to-use, disposable cartridges of Kieselghur-type material has been developed for the separation of organochlorine (OC) pesticide residues from oils and fats. The extract is cleaned up with Florisil minocolumn chromatography, followed by a solid-matrix sulphuric acid treatment. Carry-over of lipid material through the partition step is lower comapared to conventional, separatory-funnel partition. Recovery of eighteen OC pesticides from 1.0 g olive oil was between 72% and 104% at spiking levels between 0.01 and 0.15 mg/kg for the different compounds.

Simultaneous quantitative determination of thirteen urea pesticides at sub-ppb levels on a Zorbax SB-C18 column

A simple multi-residue method is described for simultaneously determining ten urea and three benzoylurea pesticides residues in drinking water with quantitation limits below the European regulatory limit of 0.1 microgram/l. The residues were extracted from drinking water with dichloromethane and analysed by HPLC on a Zorbax 5 microns SB-C18 column with diode array detection (DAD) at 240 nm. Recoveries were determined by spiking drinking water with 13 pesticides (benzthiazuron, metoxuron, monuron, fluometuron, isoproturon, diuron, linuron, chloroxuron, chlorbromuron, diflubenzuron, neburon, triflumuron and flucycloxuron) at the 0.05-0.50 microgram/l level.

Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Human Milk from Rome (Italy) and Surroundings

Organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) in human milk have been the subject of many studies. Surveys carried out in Italy are all eight years old with the exception of the latest work. Because of recent improvements in analytical methodology, the authors believe an up-to-date study would provide additional information. Thus, this paper presents a survey of the levels of human milk contamination, in Rome and surroundings, by organochlorine pesticides and PCBs. This survey is a part of a larger monitoring program covering also geographical areas outside of Rome.

Determination of acidic herbicides in cereals by QuEChERS extraction and LC/MS/MS.

A simple and rapid method has been studied for the determination of acidic herbicides (2,4-D, Dichlorprop, Dichlorprop-p, Fluazifop, Fluroxypyr, MCPA, Mecoprop and Mecoprop-p) on cereals (rye). The method involves an alkaline hydrolysis with sodium hydroxide in order to release covalently bound compounds, prior to QuEChERS extraction, followed by neutralization and analysis via liquid chromatography-double mass spectrometry LC/MS/MS. The performance of the method either with or without alkaline hydrolysis was studied in terms of recovery rates and limit of quantification (LOQ). In either case, recoveries were determined at four spiking levels (0.02 mg/kg, 0.05 mg/kg, 0.1 mg/kg and 0.5 mg/kg) with 5 replicates for each level. Mean recoveries ranged from 90 to 120 %, whereas relative standard deviations (RSD %) proved to be less than 20 %. Quantitative analysis was carried out by the internal standard (Nicarbazin) and the LC/MS/MS analysis was performed in electrospray ionisation (ESI) negative mode using a Zorbax XCB Eclipse column. The developed method was applied to the analysis of several cereals commercially available like as rye flour, oat meal, oat flakes and dehusked oat. Residue levels were found below the limit of quantification (LOQ) of the method. The method has been tested in EU Proficiency Tests for cereals with good results.

Fast determination of phenoxy acid herbicides in carrots and apples using liquid chromatography coupled triple quadrupole mass spectrometry

A fast, simple and inexpensive method has been developed for the analysis of phenoxy acid herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2-(4-chloro-o-tolyloxy)propionic acid (MCPP), 2-(4-aryloxyphenoxy)propionic acid (Fluazifop) and 2-(4-aryloxyphenoxy)propionic acid (Haloxyfop) in carrots and apples by liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS). The compounds were analyzed by QuEChERS (quick, easy, cheap, effective, rugged, safe) methodology without cleanup. The recoveries were performed at two spiked levels (0.05 and 0.5 mg/kg) for both matrices with six replicates for each level. The mean recoveries ranged from 70–92% for both apples and carrots. The precision of the method expressed as relative standard deviation (RSD%) was found to be in the range 3–15%. For all compounds, good linearity (r2 > 0.99) was obtained over the range of concentration from 0.05 μ g/mL to 0.5 μ g/mL, corresponding to the pesticide concentrations of 0.05 mg/kg and 0.5 mg/kg, respectively. The determination limits (LOQs) ranged from 0.01 ng/mL to 1.3 ng/mL in solvent, whereas, the LOQs calculated in matrix ranged from 0.05 ng/g to 21.0 ng/g for apples and from 0.06 ng/g to 10.2 ng/g for carrots. The developed methodology combines the advantages of both QuEChERS and LC/MS/MS producing a very rapid, sensitive and cheap method useful for the routine analytical laboratories.

Vertical Mobility of Soil Contaminants: Preliminary Results of a Survey on the Herbicide Atrazine

Abstract Atrazine is considered a potential contaminant of water bodies, where it has been repeatedly detected. Its use in Italy is almost limited to the Northern part of the country where corn monocultures are common. Northern Italy is characterized by the presence of an area with soil quite permeable and where ground waters are often present at not very deep levels. In this area well waters, which represent the main source of drinking water, have been frequently found contaminated by atrazine. A program has been started aimed at studying the role of soil nature and local factors in the process of groundwater contamination. Two atrazine application rates were used at two sites with loamy and loamy-sandy soils. Results clearly show a different mobility of atrazine in the two soil types. Since the two sites have similar organic carbon levels, the major proportion of clay to sand and the lower pH of loamy soil may explain the lower vertical mobility of atrazine in this soil. Work is in progress to study atr...