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Zeta potential of Polish copper-bearing shale in the absence and presence of flotation frothers

Peng M., Ratajczak T., Drzymała J.

Mining Science

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2014

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Vol. 21

57--63

EN

In this paper, zeta potential as a function of pH of copper-bearing shale, which is mined in Poland by KGHM, was investigated. The measurements were conducted in water and aqueous solutions of selected flotation frothers. It was established that for investigated copper-bearing shale, after dispersion in water, the isoelectric point (IEP) occurs at pH=3.5. Addition of frothers decreased the IEP on the pH scale and the IEP for butanol was 1.93, for MIBC 2.90 and for eicosaethylene glycol hexadecyl ether (C16E20) 2.76. In the case of introducing frothers changed, the zeta potential becomes less negative. An empirical equation, having two adjustable parameters, was used in the paper to approximate the course of the zeta potential-pH curve. The equation showed a very good approximation of the zeta potential of the investigated shale either in water or frother aqueous solutions.

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Late Glacial and Holocene vegetation and climate history of an alpine wetland on the Qinghai-Tibetan Plateau

Liu D. L., Chen G., Lai Z., Weis H., Zhou G., Peng M.

Geological Quarterly

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2013

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Vol. 57, No. 2

261-–268

EN

This study provides a vegetation and climate history of an alpine wetland in the centre of China’s Qinghai–Tibetan Plateau (QTP) over the last 14.8 ka. High resolution climate proxies include vegetation (pollen), geochemical (Ba, Rb, δ13C) and physical (particle size and magnetic susceptibility) data; optically stimulated luminescence (OSL) and AMS radiocarbon dating were used to reconstruct the environmental changes in the wetland ecosystem. Based on physical and geochemical proxies, the sucession divided into five stratigraphic units encompassing time intervals of 14.76–14.31, 14.31–13.17, 13.17–4.47, 4.47–0.51 and 0.51–0 ka. The average sedimentation rate of all these units was 0.098 mm/a. The study showed that this ecosystem was sensitive to climate change.

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A simple and sensitive gas chromatographic-tandem mass spectrometric method for the determination of cantharidin in cosmetic products

Peng M., Yang Y.

Acta Chromatographica

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2011

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Vol. 23, no. 4

611--619

EN

The analysis of cantharidin, a potent antitumor yet highly toxic chemical, is reported in this article. In regions including the United States, Europe, and China, cantharidin is either a banned ingredient or being highly regulated in cosmetic products. In this article, a gas chromatographic-tandem mass spectrometric (GC-MS/MS) method has been established for the determination of cantharidin in cosmetic products. Cosmetic samples were divided into two groups according to whether they contained aqueous ethanol or not. Samples containing aqueous ethanol in the formulation were dried under an air flow prior to extraction by methanol. The multiple reaction monitoring (MRM) mode with the parent ion at m/z 128 and the product ions at m/z 55 and 85 was employed. The linear range covered from 0.1 to 30.00 μg mL-1 (R = 0.9996) for cantharidin. The detection limit (LOD) was 0.3 μg kg. -1. The intraday and between-day relative standard deviations (RSDs) were <8.7%. The mean recoveries were within the range 101.5–110.5%. The developed GC-MS/MS method was applied on 12 commercial cosmetic product samples, and is shown to be simple and sensitive and can be used for the qualitative and quantitative analysis of cantharidin in cosmetic products.