Yuanming Guo

Ultrasound‐assisted extraction and solid‐phase extraction as a cleanup procedure for organochlorinated pesticides and polychlorinated biphenyls determination in aquatic samples by gas chromatography with electron capture detection

The feasibility of developing a quick, easy, efficient procedure for the simultaneous determination of organochlorinated pesticides and polychlorinated biphenyls in aquatic samples using gas chromatography with electron capture detection based on solid-phase extraction was investigated. The extraction solvent (n-hexane/acetone, cyclohexane/ethyl acetate, n-hexane/dichloromethane, n-hexane) for ultrasound-assisted solid-liquid extraction and solid-phase extraction columns (florisil, neutral alumina, acidic alumina, aminopropyl trimethoxy silane, propyl ethylenediamine, aminopropyl trimethoxy silane/propyl ethylenediamine, graphitized carbon black and silica) for cleanup procedure were optimized. The gas chromatography with electron capture detection method was validated in terms of linearity, sensitivity, reproducibility, and recovery. Mean recoveries ranged from 75 to 115% with relative standard deviations <13%. Quantification limits were 0.20-0.40 ng/g for organochlorinated pesticides and polychlorinated biphenyls. The satisfactory data demonstrated the good reproducibility of the method with relative standard deviations lower than 13%. In comparison to other related methods, this method requires less time and solvent and allows for rapid isolation of the target analytes with high selectivity. This method therefore allows for the screening of numerous samples and can also be used for routine analyses.

Rapid Determination of Catecholamines in Urine Samples by Nonaqueous Microchip Electrophoresis with LIF Detection

A method was developed for the rapid separation of catecholamines by nonaqueous microchip electrophoresis with LIF detection, A homemade pump-free negative pressure sampling device was used for rapid bias-free sampling in nonaqueous microchip electrophoresis, the injection time was 0.5 s and the electrophoresis separation conditions were optimized. Under the optimized conditions, the samples were separated completely in less than 1 min. The average migration times of the epinephrine, dopamine, and norepinephrine were 34.26, 43.81, and 50.07 s, with a relative standard deviation of 1.05, 1.26 and 0.89% (n = 7), respectively. The linearity of the method ranged from 0.0125 to 2.0 mg/L for epinephrine and 0.025∼4.0 mg/L for dopamine, and norepinephrine, with correlation coefficients ranging between 0.9978 and 0.9986. The detection limits of epinephrine, dopamine, and norepinephrine were 2.5, 5.0 and 5.0 μg/L, respectively. The recoveries of epinephrine, dopamine, and norepinephrine in spiked urine samples were between 86 and 103%, with relative standard deviations of 4.5∼6.8% (n = 5). The proposed nonaqueous microchip electrophoresis with laser induced fluorescence detection system combined with a pump-free negative pressure sampling device was a simple, inexpensive, energy efficient, miniaturized system that can be successfully applied for the determination of catecholamines in urine samples. This article is protected by copyright. All rights reserved.

Determination of benzene series compounds and chlorobenzenes in water sample by static headspace gas chromatography with flame ionization detection

A simple, efficient, solvent-free, and readily commercially available approach for the determination of eight benzene series compounds and 12 chlorobenzenes in water samples using the static headspace sampling and gas chromatography with flame ionization detection has been described in this paper. The proposed static headspace sampling method was initially optimized, and the optimum experimental conditions explored were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 70°C for 43 min. The linearity of the method ranged from 1 to 200 μg/L for 20 analytes, with correlation coefficients ranging between 0.9962 and 0.9994. The limits of detection were in the μg/L level, ranging between 0.15 and 0.4 μg/L. The relative recoveries of spiked benzene series and chlorobenzenes with external calibration method at different concentration levels in pure, tap, and sea water samples were 84-113, 78-115 and 85-119%, respectively, with relative standard deviations of 3.8-6.8, 4.1-5.8, and 4.8-5.4% (n = 5), respectively. That this method can be successfully applied to the determination of benzene series compounds and chlorobenzenes in pure, tap, and sea water samples, simultaneously.

Determination of chlorobenzenes in pure, tap, and sea water by static headspace gas chromatography-electron capture detection

A simple, efficient, solvent-free, and commercial readily available approach for determination of 11 chlorobenzenes (CBs) in water samples using the static headspace (HS) sampling and gas chromatography-electron capture detector has been described. The proposed static HS sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% (w/v) sodium chloride placed in a 20 mL vial and stirred at 70°C for 30 min. The linearity of the method ranged from 0.16 to 8.0 μg/L for dichlorobenzene isomers, 0.0176~0.88 μg/L for trichlorobenzene isomers, 0.004~0.2 μg/L for tetrachlorobenzene isomers, and from 0.001 to 0.05 μg/L for pentachlorobenzene and hexachlorobenzene, with correlation coefficients ranging between 0.9992 and 0.9999. The limits of detection were in the low μg/L level, ranging between 0.0002 and 0.04 μg/L. The relative recoveries of spiked CBs with external calibration or standard addition method at different concentration levels in pure, tap, and sea water samples were 83~116%, 89~108%, and 93~112%, respectively, and with relative standard deviations of 1.9~6.3%, 1.6~5.4%, and 2.5~5.7% (n = 5), respectively. It is concluded that this method can be successfully applied for the determination of CBs in pure, tap, and sea water samples.

The complete chloroplast genome of Gracilariopsis lemaneiformis, an important economic red alga of the family Gracilariaceae

Abstract The complete chloroplast DNA (cpDNA) of a famous red alga of the family Gracilariaceae, Gracilariopsis lemaneiformis, was deduced by using next-generation sequencing and de novo assembly technology. The complete cpDNA of G. lemaneiformis consists of 182 505 bp and encodes 230 unique genes consisting 204 protein-coding genes (PCGs), 21 transfer RNA genes, 3 ribosomal RNA genes, 1 transfer-messenger RNA genes and 1 non-coding RNA genes. Among 204 PCGs, ccsA gene is interrupted by a intron. Unlike the typical quadripartite structure (a pair of inverted repeats separated by the small single-copy and large single-copy units) of cpDNA in higher plants, the complete cpDNA of G. lemaneiformis is very compact, containing no inverted repeat and just one copy of rRNA gene cluster consisting of 16S, 23S and 5S rRNA genes. The genic regions account for 83.7% of whole cpDNA genome, and the G + C content of the cpDNA was 27.4%. The low G + C content of G. lemaneiformis cpDNA is largely contributed by high A + T content in the PCGs and non-coding regions. A phylogenetic analysis of the 15 complete cpDNA from rhodophyta shows that G. lemaneiformis is closely related to macroalga Gracilaria salicornia. The complete cpDNA of G. lemaneiformis provides essential and important DNA molecular data for further phylogenetic and evolutionary analysis for rhodophyta.

Determination of Chlorobenzenes in Water Samples by Solid-Phase Disk Extraction and Gas Chromatography–Electron Capture Detection

A simple, rapid, sensitive and high throughput method is described, based on solid-phase disk extraction (SPDE) and gas chromatography-electron capture detection, for the determination of chlorobenzens (CBs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions were found to be as follows: 500 mL water sample (pH 2.5) extracted and enriched by an Empore 3-stn C18 (octadecyl) SPE disk at flow rate of 5 to 50 mL/min, eluted by 5 mL of acetone and 3 × 5 mL of methylene dichloride. The linearity of the method ranged from 0.02 to 0.4 µg/L for dichlorobenzene isomers, 0.0022-0.044 µg/L for trichlorobenzene isomers, 0.005-0.01 µg/L for tetrachlorobenzene isomers and 0.00025 to 0.005 µg/L for pentachlorobenzenes and hexachlorobenzenes, with correlation coefficients ranging between 0.9991 and 0.9999. The limits of detection were in the low ng/L level, ranging between 0.05 and 4 ng/L. The recoveries of spiked CBs with the external calibration method at different concentration levels in deionized/distilled water, tap water and sea water samples were 99-115, 91-106% and 96-110%, respectively, and with relative standard deviations of 4.5-7.6, 4.2-6.8 and 3.6-6.6% (n = 5), respectively. It is concluded that this method can successfully be applied for the determination of CBs in deionized/distilled water, tap water and sea water samples.

Determination of volatile chlorinated hydrocarbons in water samples by static headspace gas chromatography with electron capture detection

A simple, efficient, solvent-free, and commercial readily available approach for determination of five volatile chlorinated hydrocarbons in water samples using the static headspace sampling and gas chromatography with electron capture detection has been described. The proposed static headspace sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 50ºC for 20 min. The linearity of the method was in the range of 1.2-240 μg/L for dichloromethane, 0.2-40 μg/L for trichloromethane, 0.005-1 μg/L for perchloromethane, 0.025-5 μg/L for trichloroethylene, and 0.01-2 μg/L for perchloroethylene, with coefficients of determination ranging between 0.9979 and 0.9990. The limits of detection were in the low μg/L level, ranging between 0.001 and 0.3 μg/L. The relative recoveries of spiked five volatile chlorinated hydrocarbons with external calibration method at different concentration levels in pure, tap, sea water of Jiaojiang Estuary, and sea water of waters of Xiaomendao were in the range of 91-116, 96-105, 86-112, and 80-111%, respectively, and with relative standard deviations of 1.9-3.6, 2.3-3.5, 1.5-2.7, and 2.3-3.7% (n = 5), respectively. The performance of the proposed method was compared with traditional liquid-liquid extraction on the real water samples (i.e., pure, tap, and sea water, etc.) and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of volatile chlorinated hydrocarbons in different water samples.

Determination of Trace Organophosphorus Pesticides in Water Samples by Solid Phase Disk Extraction and Gas Chromatography-Thermionic Specific Detector

A simple, rapid, sensitive, and high-throughput method based on solid-phase disk extraction (SPDE) and a gas chromatography–thermionic specific detector (GC-TSD) is described for the determination of organophosphorus pesticides (OPPs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions found were 500 mL water sample (pH 2.5–7.0) extracted and enriched by a C18 (octadecyl) solid phase extraction disk at flow rate of 5 to 50 mL/min and eluted by 5 mL of acetone and 3 × 5 mL methylene chloride. The linearity of the method ranged from 0.020 to 1.00 µg/L for dimethoate, methyl parathion, and malathion, with correlation coefficients ranging between 0.9976 and 0.9992. The concentration factors for OPPs were between 498 and 554. The limits of detection were in the ng/L level, ranging between 2.5 and 4 ng/L. The relative recoveries of spiked 3 OPPs (dimethoate, methyl parathion, and malathion) with external calibration method at different concentration levels in pure, fresh water, and sea water samples were 102–112%, 94–109%, and 99–104%, respectively, and with relative standard deviations of 4.1–6.2%, 3.4–4.6%, and 3.5–5.2% (n = 3), respectively. It is concluded that this method can be successfully applied for the determination of OPPs in pure water, fresh water, and sea water samples.

Sample Pretreatment Method for Determination of Indicator Polychlorinated Biphenyls in Seafood using Ultrasonic Extraction Followed by Dispersive Solid-Phase Extraction and Gas Chromatography – Electron Capture Detection

A simple, rapid and novel method has been developed and validated for the determination of seven indicator polychlorinated biphenyls (PCBs) in seafood samples by gas chromatography coupled to electron capture detector. Freeze-dried samples were done first ultrasonic extraction by n-hexane:methylene chloride:acetone (3:1:1, v/v), and then one-step clean-up (dispersive solid-phase extraction clean-up) or two-step clean-up (concentrated sulfuric acid purification and dispersive solid-phase extraction clean-up) was selected according to the lipid contents of the samples, if the lipid content was no more than 1%, one-step clean-up was used, otherwise, two-step clean-up was chose. The linearity of this method ranged from 1.25 to 100 μg/L, with regression coefficients ranging between 0.9991 and 0.9998. The limits of detection were in low ng/g level, ranging between 0.005 and 0.0076 ng/g (wet weight). The recoveries of spiked seven PCBs with external calibration method at different concentration levels in Pseudosciaena polyactis, Penaeus vannamei and Sinonovacula constricta were in the range of 78-105%, 73-110% and 75-107%, respectively, and with relative standard deviations of 3.3-5.1%, 3.5-6.3% and 3.4-5.1% (n = 5), respectively. The performance of the proposed method was also compared with traditional soxhlet extraction and column chromatography clean-up on the same real seafood samples and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of PCBs in different seafood samples.

The complete chloroplast genome of Wakame (Undaria pinnatifida), an important economic macroalga of the family Alariaceae

Abstract We decoded the complete chloroplast DNA (cpDNA) sequence of the Wakame (Undaria pinnatifida), an important economic macroalga of the family Alariaceae, by using next-generation sequencing technology. The genome consists of 130 336 bp containing a pair of inverted repeats (IRs) of 4790 bp, which was separated by a large single-copy region and a small single-copy region of 77 821 and 42 934 bp, respectively. The genic regions account for 77.7% of whole cpDNA, and the GC content of the cpDNA was 30.6%. The U. pinnatifida cpDNA encodes 153 unigenes (129 protein-coding genes, 3 rRNA genes and 21 tRNA genes). There are 1 PCG (rpl33) and 1 tRNA genes (trnL) containing an intron. A phylogenetic analysis of the four complete cpDNA from Phaeophyceae showed that U. pinnatifida is closely related to Saccharina japonica with high bootstrap value supported. The complete cpDNA of U. pinnatifida provides essential and important DNA molecular data for further phylogenetic and evolutionary analysis for brown algae.