Solid-phase extraction method for the determination of free and conjugated phenol compounds in human urine.

A rapid flow system for automatic sample conditioning for the determination of phenol compounds in human urine has been developed and optimised. Free phenols are detected directly in urine samples while total phenols require acid hydrolysis to convert their conjugate fraction into free phenols, all compounds then being cleaned up and preconcentrated by solid-phase extraction. Separation and determination are done by gas chromatography, using mass spectrometry operating in the selective ion monitoring mode for quantitation. The linear range was 1-160 ng/ml of urine for most of the phenols. Limits of detection for phenol compounds (phenol, alkylphenols and chlorophenols) in the nanogram-per-millilitre range (0.3-0.6 ng/ml) are thus achieved by using 1 ml of urine; also, the repeatability, as RSD, is less than 6.5%. Based on the results for urine samples from unexposed individuals, 2-methylphenol, 2-chlorophenol and 2,4-dichlorophenol are largely detected in hydrolysed urine samples, whereas phenol and 4-methylphenol are detected in hydrolysed and unhydrolysed urine. Other chlorophenols such as trichlorophenols and pentachlorophenol are not detected. The results obtained in the analysis of urine from an individual before and after dietary intake reveal that the levels of phenol compounds in urine look related to food intake.

Study of the degradation of the herbicides 2,4-D and MCPA at different depths in contaminated agricultural soil.

Two phenoxyacid herbicides (2,4-D and MCPA) and their six corresponding phenols were determined in soil by using gas chomatography with electron impact mass spectrometry (GC/MS) for confirmation/quantitation. An automatic extraction (leaching), preconcentration, and cleanup (sorption) module was developed to extract the eight compounds from soil. The average recovery of all species, spiked to soil at microg/kg-mg/kg levels, was 95% (average standard deviation +/- 5%). A plot of agricultural clayey soil (approximately 12 m2) was contaminated with both herbicides (approximately 96 g/m3, depth 10 cm, density 1.23 g/cm3) and irrigated with (17 mm) at variable time intervals. Both herbicides and their corresponding phenol compounds were monitored at different soil depths over a 50 day period. The degradation of both herbicides in the surface layer (t(1/2) approximately 5 days) is a result of photodecomposition and microbial action; in the deeper layers, the degradation products occur in lower proportions by effect of leaching and are also the result of microbial action. The six phenol metabolites are only detected in the surface layer as they form preferentially by photodecomposition. The main metabolites (viz. 2,4-DCP for 2,4-D and 4-C-2-MP for MCPA) are formed within 24 h after the soil is contaminated; their concentration peaks are at day 8 in the absence of irrigation.

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.

Procedimiento excisional electroquirúrgico con asa diatérmica para el tratamiento de la neoplasia intraepitelial cervical / Electrosurgical excisional procedure with diatermic asa for the treatment of intraepithelial cervical neoplasia

Objetivo: evaluar la excisión de la zona dr transformación con ASA (EZTA), en nuestras manos. Población y método: un total de 407 pacientes con citología anormal, a las que se les practicó EZTA después de colposcopía con o sin biopsia dirigida, sugestivas de lesión intraepitelial escamosa (LIE) o glandular, del 26 de abril de 1993 al 20 de febrero de 1995. Resultados: el porcentaje de curación fue de 95.09 por ciento el 84.03 por ciento de las pacientes en las que el procedimiento de consideró suficiente como tratamiento, acudieron a control citológico posterior; un 15.74 por ciento con complicaciones graves. CONCLUSION: la excisión de la ZT con ASA, por ser efectiva, barata y relativamente fácil de practicar, parece ser un procedimiento terapéutico con el que se puede disminuir la mortalidad por Cáncer del Cuello Uterino en nuestro país, implementandolo a la par de detección masiva.