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1

Determination of icariin in bushenqiangshen capsule in high-performance liquid chromatography with fluorescence detection by precolumn chelation with aluminum

100%

Yang G. J. , Lv L.

Acta Chromatographica

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2012

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tom Vol. 24, no. 2

229--239

EN

A simple and sensitive method of high-performance liquid chromatography with fluorescence detection (HPLC-FLD) was developed for the determination of icariin in capsules by precolumn chelation with aluminum. In order to obtain a stable fluorescence signal, the reaction conditions of the fluorescent chelation complex between icariin and aluminum were investigated in detail. Chromatography was carried out on an Agilent Zorbax Extend C18 column (150 mm × 4.6 mm, 5.0 μm) using methanol as mobile phase at a flow rate of 1.0 mL min-1. The excitation and emission wavelengths were set at 430 and 480 nm, respectively. At optimum conditions, the calibration curve was linear in the concentration range from 0.010 to 100.0 μg mL-1 with the limit of detection of 3.5 ng mL-1 (S/N = 3). A comprehensive method was validated for precision and accuracy. The method described here has been successfully applied for the determination of the icariin content in a capsule with satisfactory results.

2

Existence and uniqueness results for fractional differential equations with boundary value conditions

80%

Lv L. , Wang J. , Wei W.

Opuscula Mathematica

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2011

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tom Vol. 31, no. 4

629-643

EN

In this paper, we study the existence and uniqueness of fractional differential equations with boundary value conditions. A new generalized singular type Gronwall inequality is given to obtain important a priori bounds. Existence and uniqueness results of solutions are established by virtue of fractional calculus and fixed point method under some weak conditions. An example is given to illustrate the results.

3

Comparison of grinding characteristics in high-pressure grinding roller (HPGR) and cone crusher (CC)

70%

Liu L. , Tan Q. , Liu L. , Li W. , Lv L.

Physicochemical Problems of Mineral Processing

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2017

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tom Vol. 53, iss. 2

1009--1022

EN

We comparatively studied the ball mill grinding characteristics of comminuted hematite products using a high-pressure grinding roll (HPGR) and a conventional cone crusher (CC). The major properties, including grinding kinetics and technical efficiency (Et), were investigated. The parameters in m-th order grinding kinetics were analyzed, and grinding specific rates were visualized. Ore particles experienced three inherent stages in ball grinding mills, that is i) rapid grinding of coarse fraction, ii) dynamic grinding of medium size fraction, and iii) single grinding of medium size fraction. Particles with size -0.043+0.031 mm were used into dynamic grinding stage earlier than particles -0.105+0.043 mm, and then over-grinding of fines occurred easily. Compared with CC products, HPGR products had significantly shorter turning time points in three breakage stages, implying that HPGR products were ground faster with earlier occurrence of fines over-grinding. HPGR products gave lower Et at a decreasing rate than the CC products for -2.0 mm and -0.5 mm feeds. Then, it showed a slightly higher value of Et for -2.0+0.5 mm feed. This indicated that fines over-grinding in HPGR full-size products were more serious under the condition of coarse grinding, whereas the efficiency was higher, and over-grinding weakened significantly in HPGR coarse products because of screening-out fines.

4

Identification and differentiation of major flavonoids in two kinds of Epimedium extracts and rat plasma by rapid-resolution liquid chromatography combined with time-of-flight mass spectrometry

61%

Lv L. , Zhao L. , Wang X. , Zhang H. , Zhu Z. , Chai Y. , Zhang G.

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tom Vol. 27, no. 2

331--353

EN

Epimedium pubescens Maxim. and Epimedium koreanum Nakai. are two common and confused species of Herba Epimedii in Chinese Pharmacopoeia 2010 edition. Different species and growing conditions lead to chemical differences between the two species which may result in the improper clinical usage. In this work, a new method based on rapid-resolution liquid chromatography combined with time-of-flight mass spectrometry (RRLC/TOFMS) has been developed for identification and differentiation of major flavonoids in two kinds of Epimedium extract and rat plasma. The compounds were identified effectively based on the accurate extract masses and formulae acquired by RRLC/TOFMS. The fragmentation rules deduced by collision-induced dissociation (CID) were successfully implemented in distinguishing some of the isomers, further validating the results. By using the combined analytical techniques, a total of 40 major flavonoids in extracts of two kinds of Epimedium were identified within 30 min, including 31 common components and 9 characteristic components. After oral administration, three prototype compounds in rat plasma were detected by comparing the constituents measured in vitro with those in vivo, and five metabolites were identified by contrasting the fragmentation rules. The identification and structural elucidation of the chemical constituents provided essential data for further pharmacological and clinical studies on different species of Epimedium.