Ren-Jye Lee

Purge-assisted headspace solid-phase microextraction combined with gas chromatography-mass spectrometry for determination of chlorophenols in aqueous samples.

A simple, economical and very effective method is demonstrated for simultaneous determination of 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol, in aqueous samples, by using purge-assisted headspace solid-phase microextraction (PA/HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). In the new method, purging the sample enhances the removal of the trace chlorophenols without derivatization from the matrices to the headspace. Extraction parameters including extraction temperature, purge gas flow rate and extraction time were systematically investigated. Under optimal conditions, the relative standard deviations (RSDs) were 4-11% at 50 pg/mL and 5-14% at 5 pg/mL, respectively. The recoveries were in the range of 83-114%. Detection limits were determined at the fg level. These results indicate that PA/HS-SPME provides a significant contribution to highly efficient extraction of semi-volatile CPs, especially for pentachlorophenol, which has the smallest Henrys constant and large octanol-water partitioning coefficient. In addition, the proposed method was successfully applied to the analysis of chlorophenols in landfill leachate. New perspectives are opened for headspace extraction of relatively low vapor pressure compounds in complex matrices.

Determination of cyromazine and melamine in chicken eggs using quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction coupled with liquid chromatography–tandem mass spectrometry

A rapid and sensitive method has been developed for the simultaneous detection of cyromazine and melamine in chicken eggs using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The optimal extraction solvent for the liquid-liquid extraction was 5 mL of acetonitrile with a 0.1 M hydrochloric acid aqueous solution (99.5:0.5, v/v). The extract was cleaned with 0.5 g of anhydrous magnesium sulfate and 10 mg of graphitized carbon black. The analysis of cyromazine and melamine was accomplished by combining the use of an anion exchange LC column with tandem mass spectrometry in the positive electrospray ionization mode with selected reaction monitoring mode (SRM). The detection limits were 1.6 ng g(-1) for cyromazine and 8 ng g(-1) for melamine, and the quantitation limits were 5.5 ng g(-1) for cyromazine and 25 ng g(-1) for melamine. The recoveries of cyromazine and melamine in the spiked egg samples were 83.2% and 104.6%, respectively, with an relative standard deviation (RSD) of less than 18.1%. The intra-day and inter-day precisions, represented by the RSD, ranged from 1.5% to 8.8% and 6.8% to 14.3%, respectively. The proposed method was tested by analyzing chicken eggs from the markets and from the veterinary medicine laboratory. The concentrations of cyromazine and melamine detected in these samples were in the range of 20-94 ng g(-1). The results demonstrated that the QuEChERS method combined with LC-MS/MS is a simple, rapid and inexpensive method for the analysis of cyromazine and melamine in eggs.

Sphingomicrobium astaxanthinifaciens sp. nov., an astaxanthin-producing glycolipid-rich bacterium isolated from surface seawater and emended description of the genus Sphingomicrobium.

A Gram-stain-negative, rod-shaped, strictly aerobic, flagellated and non-spore-forming marine bacterium designated strain CC-AMO-30B(T) was isolated from coastal surface seawater, Taiwan. Strain CC-AMO-30B(T) synthesized astaxanthin [40 µg (g dry weight)(-1)] and formed reddish-orange-coloured colonies on marine agar (Difco 2216). The strain showed highest pairwise 16S rRNA gene sequence similarity to Sphingomicrobium lutaoense CC-TBT-3(T) (96.4%) followed by other members of the family Sphingomonadaceae (<94%) and established a discrete phyletic lineage associated with the former. The polar lipid profile constituted a remarkable number of unidentified glycolipids (GL1-8), in addition to diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid and two unidentified lipids (L1-2). The major fatty acids (>5% of total fatty acids) were C(18:1)ω7c/C(18:1)ω6c (summed feature 8), C(16:1)ω7c/C(16:1)ω6c (summed feature 3), C(18:1) 2-OH, methyl C(18:1)ω7c, C(17:1)ω6c and C(16 : 0). DNA G+C content was 70.6%; major respiratory quinone was ubiquinone Q-10; predominant polyamine was the triamine sym-homospermidine. Chemotaxonomic evidence including characteristic glycolipid profile, presence of significant amounts of C(18:1) 2-OH and absence of typical hydroxylated fatty acids such as C(14:0) 2-OH, C(15:0) 2-OH and C(16:0) 2-OH in considerable amounts, accompanied by phylogenetic distinctiveness and several other phenotypic features support the classification of strain CC-AMO-30B(T) as a representative of a novel species within the genus Sphingomicrobium for which the name Sphingomicrobium astaxanthinifaciens sp. nov. is proposed; the type strain is CC-AMO-30B(T) ( =JCM 18551(T) =BCRC 80465(T)).

Liquid chromatography incorporating ultraviolet and electrochemical analyses for dual detection of zeranol and zearalenone metabolites in mouldy grains.

BACKGROUND Zeranol (Z) is a semi-synthetic mycotoxin that is used in some countries as a growth-promoting agent in livestock. In view of the known oestrogenic actions by Z and certain Z analogues, significant concerns exist with regard to the presence of Z residues in human foods and the potential for untoward effects, including carcinogenicity within the reproductive system. In order to confirm that foods are free from harmful Z residues, regulators need a quick and reliable analytical method that can be used for routine confirmation of Z-positive samples identified by enzyme-linked immunosorbent assay (ELISA) screening. In this study the authors have developed and validated a simple and rapid high-performance liquid chromatography method incorporating ultraviolet (UV) absorbance (wavelength 274 nm) and electrochemical (EC) dual-mode detection for simultaneous determination of Z-related mycotoxins produced from mouldy grain matrices, including rice, soybean and corn flakes. RESULTS Recoveries for all analytes were around 80% and the limits of detection ranged from 10 to 25 ng mL(-1) for UV and from 50 to 90 ng mL(-1) for EC detection with good accuracy and reproducibility. Differential profiles and occurrence rates of Z, β-zearalenol, β-zearalanol and α-zearalenol in naturally moulded grain matrices were observed, indicating different metabolite patterns and possibly grain-specific effects of mycotoxin exposure for humans and animals. The strength of this dual detection method lies in its selectivity characterised by a carbon screen-printed electrode such that aflatoxin interference is precluded. CONCLUSION The combined dual detection technique affords quick and reliable semi-confirmative and quantitative information on multiple types of Z analogues in mouldy grains without the necessity of using expensive mass spectrometry. The method is considered a superior supplement to ELISA, which only screens total Z immunoreactivity.

Identification of new minor metabolites of penicillin G in human serum by multiple-stage tandem mass spectrometry.

Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) were applied to characterize drug metabolites. Although these two methods have overcome the identification and structural characterization of metabolites analysis, they remain time-consuming processes. In this study, a novel multiple-stage tandem mass spectrometric method (MS(n) ) was evaluated for identification and characterization of new minor metabolism profiling of penicillin G, one of the β-lactam antibiotics, in human serum. Seven minor metabolites including five phase I metabolites and two phase II metabolites of penicillin G were identified by using data-dependent LC/MS(n) screening in one chromatographic run. The accuracy masses of seven identified metabolites of penicillin G were also confirmed by mass spectral calibration software (MassWorks™). The proposed data-dependent LC/MS(n) method is a powerful tool to provide large amounts of the necessary structural information to characterize minor metabolite in metabolism profiling.

The determination of flavonoids in Wikstroemia indica C. A. Mey. by liquid chromatography with photo-diode array detection and negative electrospray ionization tandem mass spectrometry

RATIONALE Flavonoids in the medicinal plant Wikstroemia indica C. A. Mey. are present in trace amounts and found in complex matrices. An efficient and sensitive method is necessary for the rapid identification of such biomolecules. METHODS Flavonoids were extracted with methanol via ultrasonic-assisted extraction and analyzed by liquid chromatography with photo-diode array detection and tandem mass spectrometry. The extract was analyzed and compounds were identified using negative electrospray ionization data-dependent tandem mass spectrometry. RESULTS The results confirmed the presence of three flavonoid compounds, seven biflavonoid compounds, and one coumarin-like compound, daphnoretin, in the extracts of different plant parts of W. indica. The method detection limit was evaluated down to 5 µg/g using kaempfol as a reference standard. CONCLUSIONS The proposed method offers a rapid and reliable analysis for the determination of flavonoids in medicinal plants.