Determination of neonicotinoid insecticides in environmental samples by micellar electrokinetic chromatography using solid-phase treatments.

A sensitive and reliable method based on MEKC has been developed and validated for trace determination of neonicotinoid insecticides (thiamethoxam, acetamiprid, and imidacloprid) and the metabolite 6-chloronicotinic acid in water and soil matrices. Optimum separation of the neonicotinoid insecticides was obtained on a 58 cm long capillary (75 µm id) using as the running electrolyte 40 mM SDS, 5 mM borate (pH 10.4), and 5% (v/v) methanol at a temperature of 25°C, a voltage of 25 kV and with hydrodynamic injection (10 s). The analysis time was less than 7 min. Prior to MEKC determination, the samples were purified and enriched by carrying out extraction-preconcentration steps. For aqueous samples, off-line SPE with a sorptive material such as Strata-X (polymeric hydrophobic sorbent) and octadecylsilane (C18) was carried out to clean up and preconcentrate the insecticides. However, for soil samples, matrix solid-phase dispersion (MSPD) was applied with C18 used as the dispersant. Good linearity, accuracy, and precision were obtained and the detection limits were in the range between 0.01 and 0.07 µg mL⁻¹ for river water and 0.17 and 0.37 µg g⁻¹ for soil samples. Recovery levels reached greater than 92% for all of the assayed neonicotinoids in river water samples with Strata-X. In soil matrices, the best recoveries (63-99%) were obtained with MSPD.

Rapid characterization of fatty alcohol ethoxylates by non-aqueous capillary electrophoresis.

Fatty alcohol ethoxylates (FAE) (a mixture of nonionic surfactants) have been characterized using NACE with UV detection. Phenyl polyurethane derivatives of these compounds were previously obtained by reaction with phenyl isocyanate. The derivatization reaction only requires microwave irradiation for 30 s (600 W). Phenyl polyurethanes were separated and characterized using a BGE containing a mixture of ammonium nitrate (15 mM), acetic acid (1.5%) and 9:1 v/v methanol/ACN. After optimization of the instrumental conditions for the separation, phenyl polyurethane compounds (formed from the corresponding FAE) with ethylene oxide numbers (EON) of 6 (certified standard and industrial samples), 7 and 10 (both as industrial samples), and 5.5 (microemulsion phase) were successfully separated and characterized. The properties of these FAE nonionic surfactants are very important in the petroleum industry, which requires characterization of the quality of the purchased materials as well as the final products in the microemulsion-oil-water stream process. This analytical objective has been achieved by the proposed NACE methods, allowing FAE to be distinguished from 5.5 to 10 EON with errors below 4%, and shows advantages against to HPLC methods.

Method of determination of nitrosamines in sausages by CO2 supercritical fluid extraction (SFE) and micellar electrokinetic chromatography (MEKC).

In this paper, the use of supercritical fluid extraction (SFE) and micellar electrokinetic capillary chromatography (MEKC) is proposed for the complete analysis of volatile nitrosamines in sausages. The extraction fluid used was CO2 and variables such as density, temperature of thimbles, extraction time, modifier, fluid flow, and kind of traps were investigated. Several experiments were carried out to obtain the most favorable conditions for analysis of volatile nitrosamines in sausages. The recoveries ranged from 21 to 82% for the five nitrosamines studied. The optimal condition of extraction was 0.2 g of sample fortified with 10 mg/kg, using dynamic extraction during 20 min and with adsorbent Florisil in the trap. The solvent selected for the elution of the analytes was methanol.

The Premature Infants in Need of Transfusion (PINT) study: a randomized, controlled trial of a restrictive (low) versus liberal (high) transfusion threshold for extremely low birth weight infants.

OBJECTIVE: To determine whether extremely low birth weight infants (ELBW) transfused at lower hemoglobin thresholds versus higher thresholds have different rates of survival or morbidity at discharge. STUDY DESIGN: Infants weighing <1000 g birth weight were randomly assigned within 48 hours of birth to a transfusion algorithm of either low or high hemoglobin transfusion thresholds. The composite primary outcome was death before home discharge or survival with any of either severe retinopathy, bronchopulmonary dysplasia, or brain injury on cranial ultrasound. Morbidity outcomes were assessed, blinded to allocation. RESULTS: Four hundred fifty-one infants were randomly assigned to low (n = 223) or high (n = 228) hemoglobin thresholds. Groups were similar, with mean birth weight of 770 g and gestational age of 26 weeks. Fewer infants received one or more transfusions in the low threshold group (89% low versus 95% high, P = .037). Rates of the primary outcome were 74.0% in the low threshold group and 69.7% in the high (P = .25; risk difference, 2.7%; 95% CI -3.7% to 9.2%). There were no statistically significant differences between groups in any secondary outcome. CONCLUSIONS: In extremely low birth weight infants, maintaining a higher hemoglobin level results in more infants receiving transfusions but confers little evidence of benefit.

Development of a new method for the determination of nitrosamines by micellar electrokinetic capillary chromatography.

A new method was developed for separation and quantification of nitrosamines by micellar electrokinetic capillary chromatography (MEKC). The effects of composition of the buffer, concentration of sodium dodecyl sulfate (SDS), gamma-cyclodextrin (CD) and pH on the separation and migration times of the nitrosamines were investigated. The different instrumental variables affecting sensitivity and resolution, such as power supply, injection mode and wavelength for measurement, were carefully optimized. The direct application of this method to aqueous synthetic samples allowed the separation and determination of nitrosamine mixtures at the mg x L(-1) level. The calibration curves revealed a linear range between 0.25 and 10 mg x L(-1), with detection limit (DL) varying from 0.16 to 0.27 mg x L(-1), quantification limit (QL) varying from 0.52 to 0.90 mg x L(-1), and RSD relative standard deviation (RSD) from 4.5% to 8.5%. The proposed method was successfully applied to the determination of dimethylnitrosamine (DMN), diethylnitrosamine (DEN), N-nitrosopyrrolidine (NPYR), N-nitrosomorpholine (NMOR) and N-nitrosopiperidine (NPIP).

Determination of nitrosamines in preserved sausages by solid-phase extraction-micellar electrokinetic chromatography.

A new methodology for extraction, pre-concentration and analysis of nitrosamines in meat derived products was developed. The samples (canned sausages) were distilled in vacuum steam and the nitrosamines were pre-concentrated by solid-phase extraction with active carbon. Then, micellar electrokinetic chromatography was used for the separation and determination of the different nitrosamines contained in a real sample and gas chromatography with mass spectrometry detection was used as the confirmation technique. The method allowed the determination of nitrosamine compounds at trace levels with relative standard deviation ranging from 4.0 to 22%.

Gestión de la calidad

Contenido:!)Principios generales sobre la calidad analitica; 2)Normativas; 3)Aspectos relacionados con el control de calidad: trazabilidad, incertidumbres, materiales de referencia, calibracion, validacionde metodologias; 4)Documentos del sistema de calidad; 5)Evaluacion de resultados analiticos; 6)Acreditacion de laboratorios; 7)Anexos

Gestión de la calidad

Contenido:!)Principios generales sobre la calidad analitica; 2)Normativas; 3)Aspectos relacionados con el control de calidad: trazabilidad, incertidumbres, materiales de referencia, calibracion, validacionde metodologias; 4)Documentos del sistema de calidad; 5)Evaluacion de resultados analiticos; 6)Acreditacion de laboratorios; 7)Anexos

Estudio dermatológico en el Regional Marianao durante el año 1967

Se hace un estudio de las enfermedades dermatológicas más frecuentes en este regional las cuales representaron el 13(por ciento) de todas las consultas dadas, de donde, el 65(por ciento) de las entidades son producidas por dermatitis; 14,8 por hongos superficiales; 8.2(por ciento) bacterianas; 5(por ciento) zooparasitarias; 3(por ciento) virales y el 4(por ciento) misceláneas. De los casos consultados fueron ingresados el 2.6(por ciento). Los tumores malignos de piel fueron pocos frecuentes(AU)

Carcinoma basaloide de la vulva: presentaciòn de un caso

Se presenta un caso de carcinoma basaloide de la vulva, de difìcil diagnòstico clìnico, el cual se basa esencialmente en la histopatologìa. Se hace una breve revisiòn de la literatura.El carcinoma basaloide es un tumor originado a partir del tejido epitelial, cuyas cèlulas recuerdan el estrato basal de la epidermis(AU)

Reacciòn leprosa y lepromatosa

Se hace una breve revisiòn de la reaciòn lepròtica lepromatosa y sus distintas variantes, tanto el aspecto clìnico, histològico, bacteriològico y su fisiopatologìa. Enfatizando que frente a todos los cuadros de eritema nudoso, polimorfo y vasculitis en nuestro medio, debe descartarse siempre la posibilidad de lepra(AU)

Lepra tuberculoide

Hemos hecho una breve revisión de la literatura sobre la lepra tuberciloide, se revisa el concepto, la historia sus formas clínicas, la histopatología la bacteriología, donde se hace referencia a la introducción reciente del test de concentración de Khanolkar por el cual se ha podido demostrar más fácilmente la presencia del Mycobacterium tuberculoide combinado con 2 tinciones fluorescentes y mediante el auxilio del microscopio de lámpara con luz fluorescente, todo lo cual permite encontrar fácilmente los organismos acidograso en tejidos cuando ellos no pueden ser visto por métodos histológicos corrientes. En la inmunología se hace mención sobre la opinión de algunos autores de que no existe la positividad del Mitsuda en un 100 (por ciento) de los casos solamente en ciertas formas clínicas. También se realiza un breve diagnóstico diferencial de la forma tuberculoide, de las demás formas(AU)