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J C Moltó

Publications and source records attributed to J C Moltó.

30 records · Page 2Linked to original sources
PubMed2000

Pesticide residue determination in fruit and vegetables by liquid chromatography-mass spectrometry.

An overview is given of pesticide residue determination in fruit and vegetables by liquid chromatography-mass spectrometry (LC-MS). Emphasis is placed on the thermospray, particle beam and atmospheric pressure ionization interfaces including advantages and drawbacks and typical detection limits. The capacity of each interface to provide useful data for identification/confirmation of analytes and the possibility of obtaining structural information for the identification of target and non-target compounds is discussed. Finally, sample preparation techniques are dealt with in relation to their influence on further LC-MS determination.

Chromatography, Liquid↗
PubMed2000

Microbial evaluation of Spanish potato omelette and cooked meat samples in University restaurants.

The focus of this study was to evaluate the microbial quality of Spanish potato omelette and cooked meat samples including pork loin, chicken croquettes, long pork sausage, chicken breast, and meatballs from University restaurants. Microbiological analyses of Spanish potato omelette and cooked meat samples resulted in aerobic plate counts from <1.00 to 2.90 and from <1.00 to 6.04 log10 CFU g(-1), respectively. Total coliforms ranged from <3 to 43 most probable number (MPN) g(-1) and from <3 to >2,400 MPN g(-1) for Spanish potato omelette and meat products, respectively. Escherichia coli, coagulase-positive staphylococci, and Lancefield group-D streptococci were detected in 1.7%, 3.5%, and 12.9% of Spanish potato omelette samples, respectively. For cooked meat samples, 8.8%, 7.6%, and 24.6% contained E. coli, coagulase-positive staphylococci, and Lancefield group-D streptococci, respectively. E. coli O157:H7, Salmonella spp., and Shigella spp. were not detected. Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter freundii, Enterobacter cloacae, and Serratia spp. were isolated from Spanish potato omelette samples. For cooked meat samples, C. freundii, E. cloacae, and Aeromonas hydrophila were detected. The results suggest that some handling practices should require more attention, and as a consequence, a hazard analysis and critical control point program should be developed and implemented.

Animals↗
PubMed1998

Comparison of different sorbents for on-line liquid-solid extraction followed by high-performance liquid chromatographic determination of nitrogen-containing pesticides.

LiChrolut EN [poly(styrene-divinylbenzene), PSDVB], Carbograph (graphitized carbon black, GCB), Isolute CN (cyanopropylsilica), Isolute C2 (ethylsilica), and LiChrospher RP18 (octadecylsilica) were studied for on-line solid-phase extraction of twelve nitrogen containing pesticides from water. Determination (UV 210 nm) was performed with a Spherisorb C8 analytical column and an acetonitrile-water gradient. The mean recoveries from 50 ml ranged from 83% for RP18 to 44% for GCB, and decreased in the following order: RP18, CN, LiChrolut EN, C2, and GCB. GCB showed poor recoveries due to incomplete desorption with the acetonitrile-water gradient used, and memory effects were detected. Backflush was needed to elute selected pesticides from GCB and from LiChrolut EN. Breakthrough volumes were 50-100 ml for most selected pesticides with silica-based phases, whereas LiChrolut EN allowed larger sample volumes without observable losses.

Carbon↗
PubMed1997

An analysis of the mechanisms involved in the okadaic acid-induced contraction of the estrogen-primed rat uterus.

The contractile effect of okadaic acid (OA) and its derivatives was investigated in the rat uterus. OA (20 microM) induced a transient contraction which, after plateauing, slowly decreased. The structurally related compound okadanol (20 microM) failed to induce any significant contraction. Conversely, the synthetic compound methyl okadaate (20 microM) and the naturally occurring ester 7'-hydroxy-4'-methyl-2'-methylen-hept-4'(E)-enyl okadaate (20 microM) were as active as the free acid. The OA-induced contraction was unaffected in the presence of neomycin (5 mM), mepacrine (30 microM), 1-[N,O-bis(1,5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperaz ine (10 microM), calphostin C (3 microM) and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (30 microM). The calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (100 microM) did not modify the amplitude of the OA-induced contraction but significantly increased the rate of tension decay. The myosin light chain kinase inhibitor 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (1 mM) significantly reduced the peak amplitude of the contraction. Staurosporine (0.03-0.1 microM) did not modify the contractile component of the OA-induced response but inhibited the subsequent decrease in tension. In freshly dispersed myometral cells loaded with the fluorescent Ca++ indicator indo 1, OA did not produce any significant increase in [Ca++]i. OA (5- to 90-min contact) also failed to modify the intracellular levels of arachidonic acid, compared with basal values. These data suggest that in the rat uterus 1) the contractile effect of OA (20 microM) is specifically mediated by inhibition of protein phosphatases type 1 and/or 2A and is related to a direct interaction with the contractile machinery; 2) the decreasing phase of the OA-induced mechanical response could be mediated by a staurosporine-sensitive protein kinase different from protein kinase C.

Animals↗
PubMed1996

Optimization of a matrix solid-phase dispersion method for the analysis of pesticide residues in vegetables.

A multiresidue method based on matrix solid-phase dispersion (MSPD) is studied to determine chlorfenvinfos, chlorpyrifos, fenarimol, iprodione, procimydone, propiconazole, tetradifon, triadimefon and vinclozolin in artichokes, green beans, lettuces and tomatoes. Alumina, silica and Florisil were assessed as extracting phases, and the extracts from Florisil were the cleanest. To facilitate manual extraction, sand was added to the sample together with the dispersing phase. Three eluting systems were then studied, and dichloromethane proved to be the best. Further purification can be performed using solid-phase cleanup after diluting extracts with aqueous solutions. Octyl- and octadecyl-silica, modifications of the aqueous diluted extracts and several eluting solvents were studied. Determination was done by capillary gas chromatography (GC) with electron-capture detection, and confirmed by GC-MS using the electron impact mode and the selected ion monitoring. The proposed MSPD method was used to analyze 48 samples taken in the course of a year. Procymidone, vinclozolin, chlorpyrifos and chlorfenvinfos were identified in 10 samples at levels below the maximum residue levels allowed by the Spanish Government.

Gas Chromatography-Mass Spectrometry↗
PubMed1996

Current developments in the analysis of water pollution by polychlorinated biphenyls.

A review and discussion of the analytical developments of the last 10 years in the determination of polychlorinated biphenyls (PCBs) in water are presented, including sample treatment, clean-up, identification and determination. Some of the most significant advances have occurred in the area of sample preparation, such as the increased adoption of solid-phase extraction and on-line techniques and the chromatographic separation of PCB congeners, principally by mass spectrometry. Special attention is focused on applications to real samples.

Chromatography, Gas↗
PubMed1993

Solid-phase extraction in multi-residue pesticide analysis of water.

The determination of pesticides in water is fundamental to the solution of environmental problems as natural waters are usually contaminated with a large number of pesticides. The selection of an isolation and/or concentration technique depends largely on the class of pesticides to be determined. It is often necessary to determine simultaneously a wide variety of compounds in a water sample. Application of solid-phase extraction techniques offers a solution. The mechanisms of solid-phase extraction, types of sorbents and their application to multi-residue pesticide analysis are reviewed.

Chromatography↗
PubMed1991

Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction.

Octadecyl (C18)-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 11 of water was passed through small glass columns containing 500 mg of 50-100-microns C18 bonded porous silica. The adsorbed compounds were removed with ethyl acetate, evaporated to 200 microliters and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.

Chromatography, Gas↗
PubMed1990

Aldicarb residues in citrus soil, leaves and fruits.

Aldicarb was applied to the soil of Late Valencia orange field plots. A comparative study between four analytical methods is reported, the NPD-gas chromatography method being the best choice. The work also reports the study of accumulation and persistence of aldicarb and its biologically active metabolites in the soil, leaves and fruits (rind and pulp, separately). Residue content, at the ppb level, was found in the order leaves much greater than rind greater than pulp. Carbamate was found to accumulate mainly in its oxidized forms. Residues had reached a maximum level in about 90 days after application.

Aldicarb↗