Determination of neonicotinoid insecticides residues in bovine milk samples by solid-phase extraction clean-up and liquid chromatography with diode-array detection.

In this paper we have developed an analytical method for the simultaneous determination of four nicotinoid insecticides [acetamiprid (ACT), imidacloprid (ICL), thiacloprid (TCL) and thiamethoxam (TMX)] in bovine whole milk. These analytes were extracted, in a single step with dichloromethane, from fortified milk samples, using Chem Elut cartridges, containing diatomaceous earth material. Insecticide's determination and quantification were performed by HPLC with diode-array detection (DAD). Average recoveries of the four insecticides from bovine milk samples were between 85.1 and 99.7% at spiking levels 0.01, 0.05 and 0.1 mg kg(-1). Relative standard deviations (RSDs) were no larger than 10% for all of the recovery tests. The calculated limits of quantitation (LOQ) ranged from 0.01 to 0.04 mg kg(-1) for the four insecticides, being equal to or lower than the maximum residue limits (MRLs) established by European legislation (0.01-0.05 mg kg(-1)). The developed method is linear at concentrations within the tested interval, with coefficients of determination higher than 0.9990. According to Commission Decision 2002/657/EC, decision limit (CCalpha) and detection capability (CCbeta) have been calculated. The proposed method is rapid, simple and could be utilized for the routine analysis of pesticides residues.

Application of solid-phase extraction and liquid chromatography-mass spectrometry to the determination of neonicotinoid pesticide residues in fruit and vegetables.

A rapid and simple method for simultaneous analysis of four neonicotinoid insecticides including acetamiprid, imidacloprid, thiacloprid and thiamethoxam in fruit and vegetable matrices has been developed. For instance, ready-to-use cartridges filled with a macroporous diatomaceous material were used to extract in a single step insecticide residues with dichloromethane from aqueous-acetone extracts of fruits and vegetables. The eluate was evaporated, the residue redissolved with methanol and then analyzed by liquid chromatography-mass spectrometry in the electrospray ionization (ESI) positive mode. Average recoveries of the four pesticides were between 74.5 and 105% at both spiking levels 0.1 and 1.0 mg kg(-1) in peach, pear, courgette, celery and apricot. Relative standard deviations (RSDs) were less than 10% for all of the recovery tests. The calculated limits of quantitation (LOQs) (0.1-0.5 mg kg(-1)) were equal or lower then the maximum residue limits (MRLs) established by European legislation (0.1-0.5 mg kg(-1)). The proposed method is fast, easy to perform and could be utilized for monitoring of pesticides residues.

Analysis of nicotinoid insecticides residues in honey by solid matrix partition clean-up and liquid chromatography-electrospray mass spectrometry.

An analytical method for the routine simultaneous determination of four nicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid and thiamethoxam) in commercial multifloral honey was developed. Fortified honey samples, dissolved in water, were cleaned up through Extrelut NT20 column and, finally, insecticides were eluted with dichloromethane. The eluate was evaporated, the residue redissolved in methanol and then analyzed by LC-ESI(+)-MS. Average recoveries of the four analytes were in the range of 76% and 99% at both spiking levels 0.1 and 1.0 mg kg(-1). Relative standard deviations (RSDs) were less than 10% for all of the recovery tests. The detection limits (LODs) of the method ranged from 0.01 to 0.1 mg kg(-1) for the different insecticides studied. The developed method is linear over the range assayed, 0.5-5.0 microg mL(-1), with linear correlation coefficients higher than 0.9993.

Determination of cymoxanil in drinking water and soil using high-performance liquid chromatography.

We describe a method for determination of cymoxanil, 1-2-cyano-2-methoxy(iminoacetyl)-3-ethylurea, in drinking water and in soil, using reversed-phase HPLC with UV detection at 240 nm and a mobile phase of acetonitrile-water (30:70, v/v). Fortified water samples (1.0 L) were extracted with solid-phase extraction on Strata X. Soil samples (20 g) were extracted with acetone and the extracts were transferred onto Strata C18E. The recoveries of cymoxanil from water and soil samples were over 85% for each fortification level. The RDS were within the range 1.7-4.1% for water and 0.9-1.2% for soil samples. After optimization of the extraction and separation conditions, the method was validated.

High-performance liquid chromatographic mass spectrometric identification of the photoproducts of cymoxanil.

The photochemical degradation of the fungicide cymoxanil {2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino) acetamide} was studied in aqueous buffer solution (pH 5.9+/- 0.1) under UV light and in laboratory conditions. The degradation followed a pseudo- first-order kinetic with significant correlation coefficient. The main photoproducts were separated and tentatively identified by HPLC/UV and HPLC/MS data, as 3-ethyl-4-(methoxyamino)-2,5-dioxo-4-imidazolidinecarbonitrile, 1-ethyl-5-(methoxyimino)-2,4-imidazolidin-2,4-dione, ethylimidazolidinetrione and {[(ethylamino)carbonyl]-amino}oxoacetic acid. A photolysis pathway of cymoxanil is proposed.

Liquid chromatographic determination of nine N-methylcarbamates in drinking water.

A multi-residue method for the simultaneous extraction from drinking water using solid-phase extraction on LiChrolut EN [poly(styrene-divinylbenzene), PSDVB] and determination of nine N-methylcarbamate pesticides (NMCs) (aldicarb, its metabolites i.e. aldicarb sulfone and aldicarb sulfoxide and carbaryl, carbofuran, dioxacarb, ethiofencarb, methomyl and propoxur) using reversed-phase liquid chromatography was studied. A 1000-fold pre-concentration was achieved and the method was used for determination of the nine pesticides in water, with limits of detection in the range 3-15 ng L(-1). For all compounds the recoveries determined at the 0.1 and 1 microg L(-1) level generally ranged from 85 to 104% with relative standard deviations (RSD) of 1.4-8.8%.

Identification of photoproducts from imazosulfuron by HPLC.

Photolysis of imazosulfuron was studied in aqueous solution under UV light. The reaction followed a pseudo-first-order kinetic with significant correlation coefficient. The major photodegradation products of imazosulfuron after irradiation under UV light were separated and tentatively identified by HPLC-MS analysis as (4,6-dimethoxypyrimidine-2-yl)aminocarbonylsulfamic acid, 4,6-dimethoxy-2-ureidopyrimidine and 2,2'-dichloro-[3,3'] bi [imidazo[1,2-a] pyridinyl]. The results indicate that different reaction pathways are followed: (1) cleavage of the sulfonylurea bridge; (2) desulfonylation, which can proceed either by a carbon-sulfur cleavage or a nitrogen-sulfur cleavage. A mechanism for the formation of the photoproducts is proposed.

Kinetics and mechanism of cymoxanil degradation in buffer solutions.

The kinetics and mechanism(s) of the hydrolytic degradation of a compound are needed to evaluate a compound's abiotic degradation in the environment. In this paper, the hydrolysis of cymoxanil [2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino) acetamide] was investigated in dark sterile aqueous solutions under a variety of pH conditions (pH 2.8-9.2) and temperatures (15-50 degrees C). Hydrolysis of cymoxanil was described by first-order kinetics, which was dependent on pH and temperature. Cymoxanil degraded rapidly at pH 9 (half-life = 31 min) and relatively slowly at pH 2.8 (half-life = 722 days). The effect of temperature on the rate of cymoxanil degradation was characterized using the Arrhenius equation with an estimated energy of activation of 117.1 kJ mol(-)(1). An increase in temperature of 10 degrees C resulted in a decrease in half-life by a factor of approximately 5. Three competing degradation pathways are proposed for the hydrolysis of cymoxanil, with two of the pathways accounting for approximately 90% of cymoxanil degradation. These two pathways involved either initial cyclization to 1-ethyldihydro-6-imino-2,3,5(3H)-pyrimidinetrione-5-(O-methyloxime) (1, Figure 1) or direct cleavage of the C-1 amide bond to form cyano(methoxyimino) acetic acid (7). The third pathway of degradation involved initial cyclization to 3-ethyl-4-(methoxyimino)-2,5-dioxo-4-imidazolidinecarbonitrile (8), which rapidly degrades into 1-ethyl-5-(methoxyimino)-2,4-imidazoline-2,4-dione (9). All three pathways eventually lead to the formation of the polar metabolite oxalic acid.

Degradation of imazosulfuron in different soils-HPLC determination.

Imazosulfuron, 1-(2-chloroimidazo [1,2-a] pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea, is a new sulfonylurea herbicide applied once per growing season. It is highly active at low application levels and is used to control most annual and perennial broad-leaf weeds and some grasses in cereal crop. In this work the degradation of imazosulfuron in four different soils was investigated under aerobic laboratory conditions to evaluate its environmental fate. Test soils were treated with this herbicide in acetonitrile to obtain a final concentration of 0.2 mg kg(-1) (100 g ha(-1)), extracted with methylene chloride and analyzed by reversed-phase liquid chromatography (RP-HPLC) using a C(18) column coupled with UV detection. Recoveries of spiked soils ranged from 84.3 to 99.8% (RDS 0.0-4.9%; n = 4). The limits of quantitation ranged from 0.002 to 0.004 mg kg(-1). Imazosulfuron half-life, t(1/2), was calculated in each of the investigated soil. In aerobic conditions it ranged between 1 and 50 days.

Protective effect of the phenolic fraction from virgin olive oils against oxidative stress in human cells.

This paper reports the protective effect of the phenolic fraction extracted from extra virgin olive oils (OOPEs) against the cytotoxic effects of reactive oxygen species in human erythrocytes and Caco-2 cells, employed as model systems. Pretreatment of cells with various OOPEs, indeed, provides a remarkable protection against oxidative damages: this effect was strictly dependent on the o-diphenolic content of the extracts. Moreover, the protective effects observable in cellular systems were compared with in vitro antioxidant properties, measured by using the FRAP (ferric reducing/antioxidant power) assay; the reducing ability of OOPEs strictly parallels their o-phenolic content. The linear relationship demonstrated between biological effects and antioxidant capacity measured by the FRAP assay allows us to propose the use of this rapid colorimetric method in assessing and certifying the antioxidant power of extra virgin olive oil.