Current and future screening systems.
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Chemistry Techniques, Analytical↗
Biomedical subjects
S Cárdenas
Publications and source records attributed to S Cárdenas.
Combining headspace gas chromatography with mass spectrometry detection for confirmation of hydrocarbon residues in virgin olive oil following automatic screening.
Hydrocarbon residues can be present in virgin olive oils either naturally or as contaminants. Presence of benzene, toluene, ethylbenzene, xylene isomers and styrene (BTEXS) in virgin olive oil, demanded the establishment of a cut-off level to discriminate oil samples containing these residues at normal levels from those at high levels caused by contamination. By introducing volatile components present in the headspace (HS) of the oil samples (without prior chromatographic separation) into the ionization source of a mass spectrometer, samples were classified as containing normal or high levels of BTEXS (recommendable or non-recommendable forhuman consumption). Confirmation and quantification of contaminated virgin olive oils were achieved by combining HS sampling with gas chromatography-mass spectrometry (GC-MS). No sample pretreatment was necessary for the chromatographic method, but the addition of 600 microl of ethyl acetate as chemical modifier for 10 ml of virgin olive oil. Detection limits ranged between 3 and 9 ng/ml. Oil analysis showed the presence of toluene in all samples, as well as the absence of benzene, ethylbenzene and o-xylene.
Automation↗
Direct automatic screening of soils for polycyclic aromatic hydrocarbons based on microwave-assisted extraction/fluorescence detection and on-line liquid chromatographic confirmation.
An integrated screening-confirmation system for PAHs in soils is presented. The sample screening configuration comprises on-line microwave-assisted extraction of the selected pollutants, followed by continuous preconcentration and sample clean-up on RP-C18. Those samples for which the total concentration is close to or above the threshold limit established (10 microg/g) are subjected to liquid chromatographic separation for confirmation. An evaluation of the qualitative data obtained was also carried out, by calculating the unreliability zone as well as the false positive and false negative rates. The whole method (extraction/determination/confirmation) was validated using industrial soil and harbour sediment certified reference materials (IRMM, European Commission CRM 524 and CRM 535). Application to the screening of solid environmental samples with subsequent confirmation of the results is also presented.
Chromatography, High Pressure Liquid↗
Scorpion envenoming in two regions of Colombia: clinical, epidemiological and therapeutic aspects.
To determine clinical and epidemiological features of scorpion stings in two departments of Colombia, a descriptive study was performed in the hospitals of 10 towns from Antioquia (2 256 071 inhabitants) and five from Tolima (630 424 inhabitants). One hundred and twenty-nine cases were admitted during one year, 51 in Antioquia, 78 in Tolima and 41 were children less than 15 years old. Most stings (70.5%) occurred inside the house; 27.9% were on the hands and 26.4% on the feet. The scorpion species involved were Tityus pachyurus (51), Centruroides gracilis (31), T. fuehrmanni (29), T. asthenes (7) and Chactas spp. (1). In 10 cases the scorpion involved was not identified. Systemic envenoming signs (e.g. vomiting, tachypnea) were significantly more frequent in children than in adults (P < 0.05). Four children had hypertension, but none developed pulmonary oedema. One 3-year-old girl, stung by T. asthenes, had acute oedematous pancreatitis. Ninety-eight patients had mild envenoming. Moderate (27 patients) and severe (four patients) envenoming was significantly more frequent in children than in adults (P = 0.003; relative risk = 2.97). A pepsin-digested anti-Centruroides spp. antivenom was administered to 19 of 31 patients presenting systemic envenoming signs. No adverse reactions to antivenom were observed.
Adolescent↗
Oogenesis in the bluefin tuna, Thunnus thynnus L.: a histological and histochemical study.
Histology and histochemistry are useful tools to study reproductive mechanisms in fish and they have been applied in this study. In the bluefin tuna, Thunnus thymus L., oocyte development can be divided into 4 principal phases based on the morphological features of developing oocytes and follicles. The primary growth phase includes oogonia and basophilic or previtellogenic oocytes classified as chromatin-nucleolus and perinucleolus stages. The secondary growth phase is represented by vitellogenic oocytes at early (lipid globule and yolk granule 1), mid (yolk granule 2) and late (yolk granule 3) vitellogenesis stages. The maturation phase involves postvitellogenic oocytes undergoing maturation process. During the spawning period, both postovulatory follicles, which indicate spawning, and atretic follicles can be distinguished in the ovary. Carbohydrates, lipids, proteins and specially those rich in tyrosine, tryptophan, cystine, arginine, lysine and cysteine, as well phospholipids and/or glycolipids and neutral glycoproteins were detected in yolk granules. Moreover, affinity for different lectins (ConA, WGA, DBA and UEA) was detected in vitellogenic oocytes (yolk granules, cortical alveoli, follicular layer and zona radiata), indicating the presence of glycoconjugates with different sugar residues (Mannose- Man- and/or Glucose -Glc-; N-acetyl-D-glucosamine- GlcNAc- and/or sialic acid- NANA-; N-acetyl-D-galactosamine- GalNAc-; L-Fucose -Fuc-). Histochemical techniques also demonstrated the presence of neutral lipids in globules (vacuoles in paraffin sections) and neutral and carboxylated mucosubstances in cortical alveoli. By using anti-vitellogenin (VTG) serum, immunohistochemical positive results were demonstrated in yolk granules, granular cytoplasm and follicular cells of vitellogenic oocytes. Calcium was also detected in yolk granules and weakly in follicular envelope. In females, the gonadosomatic index (GSI) increased progressively from May, during early vitellogenesis, until June during mid and late vitellogenesis, where the highest values were reached. Subsequently, throughout the maturation-spawning phases (July), GSI decreased progressively reaching the minimal values during recovering-resting period (October).
Animals↗
Selective enrichment of 17 pyrethroids from lyophilised agricultural samples.
The screening of agricultural samples to determine 17 synthetic pyrethroids was investigated. Samples were lyophilised without losses of the insecticides, and then extracted with n-hexane. A simple, continuous preconcentration-elution system was developed, which included a silica sorbent column (packed with 50 mg) and used an air stream to carry the eluent (ethyl acetate) which minimised the eluate volume thus increasing the preconcentration factor; so no evaporation step was required. Pyrethroids were determined by gas chromatography-electron capture detection (GC-ECD) by using a 5% phenylmethylpolysiloxane-coated fused-silica capillary column; gas chromatography-mass spectrometry was used to identify the pyrethroids detected by GC-ECD monitoring. Limits of detection varied between 0.1 and 0.8 ng/ml (except for piperonyl butoxide, 25 ng/ml) with linear ranges from 1 to 200 ng/ml; the precision of the method was high (3-6%). Recoveries of 17 insecticides from 14 different agricultural samples fortified at levels of 20-100 ng/g ranged from 66 to 102% (bifenthrin and deltamethrin were those providing the lowest values, 66-87%). Pyrethroids were detected in eight samples (from the 100 unfortified agricultural samples tested) at concentrations lower than the established maximum residue limits (MRLs).
Chromatography, Gas↗
A solid phase extraction method for the screening and determination of pyrethroid metabolites and organochlorine pesticides in human urine.
A screening method has been developed for the determination of 23 organochlorine pesticides (OCPs) and 3-pyrethroid metabolities [cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid, cis-3-(2,2-dibromovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid and 3-phenoxybenzoic acid] from human urine. OCPs were directly detected in urine samples while pyrethroid metabolites required acid-induced hydrolysis to convert their conjugates into free acids; all compounds were then cleaned-up/preconcentrated using solid phase extraction. Determination and quantitation was achieved by gas chromatography with a mass spectrometer detector operating in selected ion monitoring mode. Limits of detection varied between 0.1 and 0.3 ng/mL with linear ranges from 0.3 to 700 ng/mL; the precision of the method was high (4.3-7.2%). Recoveries of all analytes from urine samples fortified at levels of 30 ng/mL for each OCP and 15 ng/mL for each pyrethroid metabolite ranged from 88 to 101% (captan gave the lowest recovery). The results obtained from the analysis of real urine samples show the suitability of the proposed method for monitoring people exposed to organochlorine and pyrethroid pesticides.
Biotransformation↗
Multiresidue screening of pesticides in fruits using an automatic solid-phase extraction system.
About 20 pesticides were determined in lyophilized fruits using a semiautomatic multiresidue method, based on solid-phase extraction (SPE) with a silica column. The lyophilization of the sample, besides the SPE procedure selected, provided clean extracts despite the complexity of the matrixes studied. In addition, the lyophilization process allows sample preservation for at least three months without changes in the concentrations of the pesticides. Determination and quantitation of organochlorine and pyrethroid residues was carried out using a gas chromatograph equipped with an electron capture detector (GC-ECD), and a mass spectrometric detector (GC-MS) was used for confirmation purposes. Organochlorine pesticides provided average recoveries (spiked at three concentration levels in eight different fruits) near 93 +/- 4%, being lower (89 +/- 8%) for pyrethroids as a consequence of their higher degradation and interaction with the sample matrix. On the other hand, the detection limits achieved for all pesticides (0.5-8 ng per g of lyophilized fruit) allow their determination at the MRLs established by the European Union, with good precision ( approximately 5%). Finally, from the 100 different fruits screened, only 10 positive responses were obtained, which were further confirmed by GC-MS.
Automation↗
Adrenalectomy regulates apoptotic-associated genes in rat hippocampus.
Morphological studies of granular neurons of the hippocampus have shown that adrenalectomy (ADX) induces the cell death of granular neurons, an effect prevented by corticosterone replacement. We addressed the hypothesis that corticosterone regulates the expression of the apoptotic bcl-2 gene family. Five days after adrenalectomy, we observed morphological changes related to hippocampal granule cell apoptosis that was accompanied by terminal dUTP nick and labeling (TUNEL) labeling in nuclei located in the hilus region. Corticosterone replacement prevented the cell death induced by ADX. Using RT-PCR we found a reduction in mRNA levels of the antiapoptotic gene bcl-2 in whole hippocampus, an effect which was prevented by corticosterone administration to ADX rats. However, Bcl-2 protein levels were not altered by this treatment. We did not observe modifications in the level of bcl-X(L) mRNA however, we did find a 40% reduction in Bcl-X(L) protein levels, an effect not reversed by corticosterone. In contrast, we found a reduction in the mRNA of the antiapoptotic gene bax and Bax levels after ADX; both effects were prevented by corticosterone. The reduction in proapoptotic bax and in antiapoptotic bcl-2 mRNA levels in the whole hippocampus, suggests that local variations in these molecules could account for both neuronal viability of the CA1-CA3 and granular cell death detected by morphological means and observed after ADX.
Adrenalectomy↗
Simplified method for the determination of chlorinated fungicides and insecticides in fruits by gas chromatography.
A fast, reliable method for the determination of more than twenty chlorinated fungicides and insecticides in a variety of fruit samples is presented. The pesticides are extracted from chopped samples with magnetic stirring, after adding 13 ml of acetone-phosphate buffer-brine solution (12:1, v/v) with 5 ml of n-hexane. The continuous module employed allows sequential decolourization of the organic phase, solvent changeover and solid-phase extraction for clean-up and preconcentration purposes. A 1-microl aliquot of the pesticides in ethyl acetate (eluent) is finally injected into the gas chromatograph for separation and identification. The method provides excellent clean-up despite the complexity of the matrices involved. Fruit samples (5-20 g) containing 0.1-1250 ng/g pesticides were analysed with a high precision (4-6%). After contamination of the fruit samples for 12 h, average recoveries >90% at fortification levels of 5-25 ng/g were obtained for most of the pesticides. Positive findings of these pesticides in fruits purchased at local markets were confirmed by GC-MS.
Chromatography, Gas↗
Fast urinary screening for paracetamol using on-line microwave assisted hydrolysis and spectrophotometric detection.
A fully automated urinary screening system for paracetamol and its metabolites is proposed. The method comprises on-line acid microwave assisted hydrolysis of the drug to p-aminophenol followed by reaction with o-cresol in alkaline medium. The indophenol blue dye formed can be continuously monitored at 620 nm. The detection limit achieved, 0.1 microgram ml-1, allows a high dilution of the samples, thus reducing potential interferences from the sample matrix (mainly protein degradation during urine hydrolysis). The proposed screening system also possesses an adequate selectivity, as the major interferent, epinephrine, is tolerated at concentrations higher than those that could be found in the positive urine samples. The reproducibility, expressed as relative standard deviation, was 3.0% and the sample frequency 20 h-1. The reliability of the method was established at five concentrations (between 0.5 and 4 times the detection limit). Finally, it was applied to the screening of several human urine samples. The results obtained were compared with those provided by batch acid hydrolysis, and were similar in all instances.
Acetaminophen↗
Semiautomatic method for the screening and determination of 23 organochlorine pesticides in horticultural samples by gas chromatography with electron-capture detection.
A rapid, simple, efficient device for the extraction-preconcentration of 23 organochlorine pesticides currently applied to vegetables is proposed. Pesticide residues are extracted from chopped samples by using a mixture of distilled water and light petroleum (1:1, v/v). After phase separation, an aliquot of the organic layer is continuously evaporated to dryness under a N2 stream as it is dropped into a glass tube containing distilled water. The aqueous phase, containing the analytes, is then passed through a miniaturized RP-C18 column for preconcentration, clean-up and subsequent elution with 150 microliters of ethyl acetate. A volume of 1 microliter of the extract containing pesticides is injected into the gas chromatograph, fitted with an electron-capture detector, for their selective determination. Limits of detection vary between 0.04 and 10 ng/ml, with linear ranges from 0.2 to 500 ng/ml; the average relative standard deviation at the low nanogram-per-millilitre level is 5.3%. The potential of the proposed method was realized by applying it to the screening/determination of organochlorine pesticides in horticultural commodities.
Automation↗
Discrimination of structural isomers of chlorinated phenols in waters using gas chromatography-mass spectrometry in the negative chemical ionization mode.
The analysis and identification of structural isomers of mono-, di- and trichlorophenols is reported. The fragmentation of the phenols was examined by GC-MS in both electron impact (EI) and negative chemical ionization (NCI) modes, using methane as reagent gas. The ability of NCI to discriminate these isomeric compounds from differences in relative intensities for selected peaks is demonstrated. 3- and 4-chlorophenols have similar retention times; however, they can still be discriminated because their negative mass spectra and rather different. In dichlorophenols, the presence of one chlorine atom in the ortho position decreases their retention time and the relative intensity of the fragment ion at m/z 140. The NCI mass spectra for trichlorophenols are different from the rest, particularly for the m/z value corresponding to the chlorine atom. Tetra- and pentachlorophenols were also studied and sequential losses of Cl observed. An automatic solid-phase extraction system can optionally be used to preconcentrate chlorophenols in waters prior to determination at legally established toxic levels.
Gas Chromatography-Mass Spectrometry↗
Gas chromatographic-mass spectrometric confirmation of selected benzophenones from benzodiazepines in human urine following automatic screening.
This paper reports a simple, expeditious procedure for confirming the presence of benzodiazepines in previously screened positive urine samples. Samples are manually hydrolysed to the corresponding benzophenones in an acid medium. The hydrolysis products are continuously aspirated into a photometric flow system for screening; positive samples are then confirmed and benzodiazepines identified by using a different flow system that conditions the analytes for gas chromatographic separation and unequivocal mass spectrometric confirmation. Detection limits for benzodiazepines in the nanogram-per-millilitre region are thus achieved by using 0.5 ml of hydrolysed urine; also, repeatability, as R.S.D., is less than 6.5%. The high specificity and sensitivity of the proposed method enables the confirmation of different benzodiazepines in urine samples obtained from drug addicts and patients from a local hospital.
Benzodiazepines↗
Rapid solid-phase extraction/derivatization system for sample preparation and gas chromatographic/mass spectrometric determination of drugs in human urine.
A novel automatic system has been developed for the rapid solid-extraction and derivatization of different drugs and their metabolites from urine, prior to further analysis. Manual injection of underivatized/derivatized drugs in a GC/MS system, in which the quadrupole mass filter was operated conventionally, provided high sensitivity and selectivity at the selected m/z value. The precision (2.1-6.8%) is acceptable and the overall recovery from urine was determined to be ca. 95%. The effectiveness of this approach is demonstrated with data obtained from different urine samples which had tested positively.
Calibration↗
A partially automated pretreatment module for routine analyses for seventeen non-steroid antiinflammatory drugs in race horses using gas chromatography/mass spectrometry.
A partially automated module for the routine determination of illicit non-steroid antiinflammatory drugs (NSAIDs) in biological fluids from race horses was built, tested, refined, and shown to work. This pretreatment module retains 17 NSAIDs on an Amberlite XAD-2 column before back-elution derivatization with methyl iodide in acetonitrile. Methylated derivatives are manually injected into a gas chromatograph connected to a mass spectrometer. The quantification limits thus achieved are 50-100 ng/mL in 1 mL of urine or plasma. The proposed method is more expeditious than its manual liquid-liquid and liquid-solid extraction counterparts and is similar in speed to a typical gas chromatographic program.
Animals↗
Cytogenetic analysis of gilthead seabream Sparus aurata (Pisces, Perciformes), a deletion affecting the NOR in a hatchery stock.
We have cytogenetically characterized a hatchery stock of gilthead seabream, Sparus aurata. The study included larvae, juveniles and adults. In S. aurata (diploid chromosome number 2n = 48), a pair of NORs is located at the ends of the short arms of the first submetacentric pair of chromosomes. In this stock we discovered a polymorphism which affects the NORs, and, by means of several cytogenetic and molecular techniques, we demonstrate that this polymorphism is due to the complete deletion of one of the two NORs in a high number of individuals. The significance of these cytogenetic characteristics for this species are discussed since they may be the source of aquaculture problems.
Aging↗
[Hypertension programs and the risk of ischemic cardiopathy].
OBJECTIVE: To find the risk of ischaemic cardiopathy in a sample of hypertension patients. DESIGN: Crossover study. SETTING: Almanjáyar and Cartuja Health Centres (Granada). PATIENTS AND OTHERS TAKING PART: 202 Hypertension patients included in the programme and belonging to three practices in the above-mentioned centres. MEASUREMENTS AND MAIN RESULTS: We determined the variable of age, gender, overall cholesterol, cholesterol-HDL, TAS, HVI in ECG and we recorded the number of check-ups over the last year, tobacco consumption and diabetes. The 47% of men and 46% of women presented a RCI higher than that of the population as a whole for their age and gender group, in spite of treatment and intervention on these risk factors. Men between 45 and 64 presented higher RCI than women (p < 0.001) and had fewer check-ups. CONCLUSION: We consider that our programme did not sufficiently affect the prevention of ischaemic cardiopathy. It was especially deficient in the monitoring of men between 45 and 64 years. We think that the maintenance of programmes oriented round particular pathologies, instead of integrated programmes, is not sufficient to reduce ischaemic cardiopathy, which clearly has a multiple-cause origin.
Adult↗