RESUMO
OBJECTIVE: To establish a method of determination of difluorochloromethane in workplace air by direct sampling gas chromatography. METHODS: Difluorochloromethane in workplace air was collected with aluminum plastic composite film airbag and then directly injected. Difluorochloromethane was separated by DB-1 capillary column and detected with hydrogen flame ionization detector. RESULTS: Good linearity was obtained in the range of 1.50-15 042.90 mg/m~3 with the correlation coefficient of 0.999 96. The limit of detection was 1.26 mg/m~3 and the limit of quantitation was 3.78 mg/m~3. The minimum detection concentration was 1.26 mg/m~3 and the minimum quantification concentration was 3.78 mg/m~3. The standard recovery was 98.34%-99.19%. The within-run relative standard deviation(RSD) and the between-run RSD were 1.82%-3.72% and 2.17%-4.17%, respectively. The samples can be stored at room temperature for at least 7 days. CONCLUSION: This method is suitable for difluorochloromethane detection in workplace air.
RESUMO
RESUMO A poluição do ar não está restrita a ambientes abertos, podendo existir elevadas concentrações de poluentes do ar derivados do petróleo, como o benzeno, tolueno, etilbenzeno e xilenos (BTEX), em ambientes internos. Os BTEX, mesmo quando presentes em baixas concentrações, na ordem de parte por bilhão (ppb), causam problemas à saúde humana. O objetivo deste trabalho foi aplicar uma técnica de quantificação dos BTEX, no nível de ppb, em apenas oito horas de amostragem em um ambiente interno. Para tal fim, foram usados tubos amostradores passivos associados a análise por dessorção térmica, cromatografia gasosa e espectrometria de massas. O método de calibração desse sistema analítico também foi apresentado. O uso dessa metodologia permitiu quantificar os BTEX em um laboratório de pesquisa de motores de combustão, em concentrações de 4,64, 7,87, 10,47 e 21,36 ppb respectivamente. Esses resultados estão próximos da faixa encontrada em ambientes internos por outros estudos no Brasil. A avaliação dos BTEX no laboratório de combustão, além de levar apenas 16 horas, somando a amostragem e análise das amostras, confirmou a sensibilidade da metodologia usada.
ABSTRACT Air pollution is not restricted to open air areas. High concentrations of petroleum-based air pollutants may occur, such as benzene, toluene, ethylbenzene and xylenes (BTEX), in indoor environments. The BTEX, even in low concentrations, of the order of parts per billion (ppb), cause human health problems. The objective of this work was to apply a technique of measurement of BTEX, at ppb level, using only eight hours of sampling in an indoor environment. To this end, passive tube samplers were used associated with analysis by thermal desorption, gas chromatography and mass spectrometry. The calibration method applied to this analytical system was also presented. The use of this method allowed the quantification of BTEX in a combustion engines research laboratory, at concentrations of 4.64, 7.87, 10.47 and 21.36 ppb, respectively. These results are close to the range found by other indoor studies in Brazil. The evaluation of BTEX in the combustion laboratory, besides it only takes 16 hours, considering the sampling and the analysis procedures, confirmed the sensitivity of the methodology used.
RESUMO
Effects of microfiltration membrane adsorption for eight types of pesticides with diverse physicochemical properties on direct injection liquid chromatography-tandem mass spectrometric method ( DI-LC-MS/MS) were investigated. The results showed that the adsorption effects ( AE,%) on the loss of signal detection at concentration of 2. 5 μg/L ranged from 8%-92%, 0%-81% and 2%-59% for nylon (NYL), polyethersulfone ( PES) and hydrophilic polypropylene ( GHP) membrane, respectively ( accumulated volume of feed is 1 mL). The pesticides with higher octanol-water partition coefficient (lgKow) values appeared to adsorb onto the membrane surface more readily than those with lower lgKow. The AE was found to be alleviated as the feed volume of samples increased to 10 mL, except the case of profenofos adsorption on PES membrane ( AE=9%) . The effects of PES membrane on the eight pesticides at initial individual concentration of 0 . 25 , 2. 5 and 25 μg/L were also studied. The results showed that, the lower the initial concentration of pesticides, the stronger adsorption effect under the same filtration conditions was obtained. Besides, it was effective in eliminating the membrane adsorption effects by adding 40% methanol ( V/V) into water samples as a modifier, which could consequently improve the accuracy of DI-LC-MS/MS.
RESUMO
Objective: To study the antitumor effects of transmembrane TNF-? and secretory TNF-? in vivo. Methods: Three types of TNF-? cDNA plasmids (wild type TNF-?; transmembrane TNF-? mutant; secretory TNF-? mutant) were directly injected into tumor-tearing mice. Results: The three types of TNF-? could be expressed by tumor cells and all of them could inhibit evidently the rate of tumor growth. The tumor regression after treatment with transmembrane TNF-? mutant at the early stage was more significant than that with the other two types of TNF-?( P