Yongde Yue

The occurrence and distribution of antibiotics in Lake Chaohu, China: Seasonal variation, potential source and risk assessment

The distribution and seasonal variation of fifteen antibiotics belonging to three classes (sulfonamides, fluoroquinolones and tetracyclines) were investigated in Lake Chaohu, China. The concentrations of the selected antibiotics in the surface water, eight major inflowing rivers and sewage treatment plant (STP) samples were analyzed by UPLC-MS/MS. The results indicated that sulfamethoxazole and ofloxacin were the predominant antibiotics, with maximum concentrations of 95.6 and 383.4ngL(-1), respectively, in the river samples. In Lake Chaohu, the western inflowing rivers (the Nanfei and Shiwuli Rivers) were the primary import routes for the antibiotics, and the domestic effluent from four STPs were considered the primary source of the antibiotics. The level of antibiotics in Lake Chaohu clearly varied with seasonal changes, and the highest detectable frequencies and mean concentrations were found during the winter. The quality of water downstream of Lake Chaohu was influenced by the lake, and the results of risk assessment of the antibiotics on aquatic organisms suggested that sulfamethoxazole, ofloxacin, ciprofloxacin and enrofloxacin in the surface water of Lake Chaohu and inflowing rivers might pose a high risk to algae and plants.

EVALUATION OF EXTRACTS FROM BAMBOO FOR BIOLOGICAL ACTIVITY AGAINST CULEX PIPIENS PALLENS

Abstract The extracts from 7 species of bamboo were tested for larvicidal activity against Culex pipiens pallens. At the tested concentration, the extracts of selected bamboo had different degree of toxic effects on the fourth instar larvae of Culex pipiens pallens. Among them, the extracts of Pleioblastus juxianensis, Brachystachyum albostriatum, Phyllostachys platyglossa and Pleioblastus amarus were found to be effective with LC50values at 24 h of 30.65 mg/L, 53.94 mg/L, 41.21 mg/L and 54.49 mg/L respectively, against Culex pipiens pallens larvae. The extract of Pleioblastus juxianensis by Soxhlet method showed stronger activity than the extract obtained by interval‐shaking, the LC50 of which were 30.65 mg/L and 48.34 mg/L, respectively. The diethyl ether extract of Pleioblastus juxianensis exhibited better larvicidal activity than the methanol extract and the petroleum ether extract. The results would help to provide the basis for the study of environment acceptable pesticide for mosquito control, and also help to comprehensively utilize the source of bamboo.

HPTLC determination of imidacloprid, fenitrothion and parathion in Chinese cabbage

A simple, rapid, and sensitive high-performance thin-layer chromatographic method has been developed and validated for analysis of residues of imidacloprid, fenitrothion, and parathion in Chinese cabbage. The sample was extracted by sonication in an ultrasonic water bath with acetone—petroleum ether, 5:3 (v/v), and the extract was directly applied, as bands, to glass-backed silica gel 60F254 HPTLC plates. The plates were developed with hexane—acetone, 7 + 3 (v/v), in an unsaturated glass twin-trough Camag chamber. Evaluation of the developed HPTLC plates was performed densito-metrically with a Camag TLC Scanner 3 controlled by an external PC running Wincats software (Version 1.1.2). The results indicated that the detection limits of imidacloprid (RF = 0.10), fenitrothion (RF = 0.59), and parathion (RF = 0.70) were 5.0 × 10−9 g, 2.0 × 10−8 g, 1.0 × 10−8 g, respectively. Recoveries of the pesticides from Chinese cabbage by use of this analytical method were 80.04–85.22%, and RSD were 4.18–13.15%. The precision and accuracy of the method were generally fit for analysis of pesticide residues in Chinese cabbage.

High-performance thin-layer chromatographic determination of carbamate residues in vegetables

A high-performance thin-layer chromatographic method has been developed for determination of four carbamate residues in vegetables. The method uses two mobile phases on silica gel 60 F254 GLP HPTLC layers, and detection at λ = 243 nm and 207 nm, the average wavelengths of maximum adsorption of pirimicarb and methomyl, and carbaryl and carbofuran, respectively. Recovery of 1.0–5.0 mg kg−1 of the four mixed carbamates from wax gourd and potatoes was 70.05–103.7%. The accuracy and precision of the method were confirmed by means of fortification experiments.

Use of HPTLC for Simultaneous Determination of Three Fungicides in Tomatoes

A. simple, rapid, and sensitive high-performance thin layer chromatographic method for analysis of the residues of tricyclazole, thiram, and folpet in tomatoes has been established and validated. The sample was extracted by mechanical vibration at room temperature with acetone-dichloromethane 1:1 (v/v) and the extract was directly applied as bands to glass-backed silica gel 60F254 HPTLC plates. The plates were developed with hexane-acetone 6+4 (v/v) in an unsaturated glass twin-trough chamber. Evaluation of the developed HPTLC plates was performed densitometrically. The results indicated that the detection limits of tricyclazole (RF- 0.26), thiram (RF = 0.65), and folpet (RF = 0.77) were 1.2 x 10-8, 3.0 x 10-8, 4.0 x 10-8 g, respectively. Recoveries of the pesticides from tomatoes with this analytical method were 67.66-98.02%, and RSD were 0.13-22.06%. The precision and accuracy of this method were generally fit for analysis of pesticide residues in tomatoes.

HPTLC determination of pyrethroid residues in vegetables

Residues of three pyrethroids in spiked vegetables have been analyzed by HPTLC with two mobile phases in a twin-trough chamber and in horizontal chambers. The spots were detected at λ = 203 nm and the greatest detection sensitivity for the three pyrethroids was 10 ng. Recovery after fortification at 0.5-5.0 mg kg-1 was from 70.20 to 108.5%. The relative standard deviation was 1.59-27.94%.

Separation of sulfonylurea herbicides and determination of bensulfuron-methyl residues in tapwater by HPTLC

In this work we have studied the separation of a mixture of the sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl, tribenuron, chlorimuron-ethyl) by HPTLC on silica gel F254 plates, with two different mobile phases. We also studied the effect of humidity on the separation. Bensulfuron-methyl added to tapwater at levels of 5, 10, and 20 μg kg−1 were determined after extraction by LC18 SPE. Detection limits of the method are given.

Photodegradation kinetics of octachlorodipropyl ether in organic solvents using an HPTLC method

Octachlorodipropyl ether (OCDPE) is a chloroalkyl ether widely used as an insecticide synergist, which was considered as a widespread persistent pollutant. Photodegradation kinetics of OCDPE in selected organic solvents was studied using the high-performance thin-layer chromatography (HPTLC) method in this paper. The results showed that photochemical reaction of OCDPE in organic solvents such as n-hexane, methanol, acetonitrile, and acetone under the irradiation of ultraviolet light could well be described by the first-order kinetic equation. The photodegradation rate constants of OCDPE in methanol, acetone, acetonitrile, and n-hexane were 0.3310, 0.2382, 0.0287, and 0.0276 h−1, and the corresponding half-lives were 2.09, 2.91, 24.1, and 25.1 h, respectively. Photodegradation kinetics of OCDPE under sunlight was slower than UV light, the half-lives of which were 8.87 and 2.09 h, respectively. The main photodegradation products of OCDPE in acetone and methanol under UV light were detected by HPTLC, which included product 01 (RF = 0.19) and product 02 (RF = 0.82). Identification of the main photodegradation products of OCDPE requires further studies.

Photodegradation Rate and Products of Acetochlor in Aqueous Solution

Photodegradation of acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphe myl) acetamide] was carried out in water and water-H2O2 solution under high pressure mercery lamp(HPML) or sunlight illuminating. The result shown that the photodegradation of acetochlor followed the first-order kinetics. The photolysis rate constants were 1.04 times 10-1 min-1 by HPML illuminating and 1.93 times 10-2 h-1 under sunlight illuminating, respectively. H2O2 increased the photodegradation rate of acetochlor in water solution. At least 12 photodegradation products of acetochlor were found by GC-MS analyses. Among them, three components, namely 8-methyl-1 -methoxymethyl-4-methyl-2-oxo-1,2,3,4-tet rahydroquinone( I ), 2 - methyl - 6 - N - methoxyethyl - N - oxacycloethylene - aniline( II), N- chloroacetyl - 7 - ethyl - 2, 3 - dihydroindole(III), were identified by TLC and GC-MS.

Factors affecting the separation of phthalate esters, and their analysis, by HPTLC

The phthalate esters (PAE) are ubiquitous in the environment because of the widespread use of plastic products. Reports of their harm to the environment and to human beings are increasing. This paper reports, for the first time as far as we are aware, use of HPTLC to separate and quantify PAE. The HPTLC assay enables separation of four PAE - dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), and bis-(2-ethylhexyl) phthalate (DEHP), priority pollutants listed by EPA - and qualitative and quantitative analysis of the compounds in water. The factors affecting the separation were investigated, including use of different stationary and mobile phases, different methods of development, humidity, and presaturation, or not, of the plate. The method was evaluated with water fortified at 5,1, and 0.5 μg L-1. It was then applied to detection of the compounds in water from Lake Chaohu. The assay was fully validated and shown to be sensitive (LOD ≤7 ng, LOQ 0.1 μg L-1 on HPTLC plates), accurate (recovery ≥80%), and precise (intra-day variation ≤8.7%, interday variation ≤6.7%). The results obtained by extraction using different solvents were compared. It was shown that dichloromethane was suitable for extraction of the four target substances from water.