Maw-Rong Lee

Solid-phase microextraction and gas chromatography–mass spectrometry for determining chlorophenols from landfill leaches and soil

Abstract This work evaluates solid-phase microextraction coupled with GC–MS (electron impact ionization and negative chemical ionization) to determine chlorophenols in landfill leaches and soil. A polyacrylate coated fiber is used to investigate the optimal experimental procedures, which include adsorption time, pH, salt effect, desorption time, temperature and the depth of the fiber in the injector. Detection limits are determined to be in low ng/l range and better than those obtained by US Environmental Protection Agency methods using a conventional extraction technique for chlorophenols in water. According to the analytical validations, the linearity of the absorption ranges from 0.1–100 μg/l with R.S.D.s below 9%. In addition, the feasibility of applying the proposed method to determine chlorophenols in real samples is examined by analyzing landfill leachate samples and soil samples contaminated with pentachlorophenol. All the studied chlorophenols are determined in the soil contaminated samples. Moreover, the pentachlorophenol detected in the landfill leachate is estimated in the level of 21.6 μg/l with an internal standard method. The quantities of the other studied chlorophenols are at the level of 0.1 μg/l. The effects of humic acids and a surfactant on the extraction of chlorophenols in the landfill leachate have been studied.

Determination of amphetamine and methamphetamine in serum via headspace derivatization solid-phase microextraction–gas chromatography–mass spectrometry

This study evaluates solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to determine trace levels of amphetamine and methamphetamine in serum. Headspace post-derivatization in a laboratory-made design with heptafluorobutyric anhydride vapor following SPME was compared with that without derivatization SPME. The SPME experimental procedures to extract amphetamine and methamphetamine in serum were optimized with a relatively non-polar poly(dimethylsiloxane) coated fiber at pH 9.5, extraction time for 40 min and desorption at 260 degrees C for 2 min. Experimental results indicate that the concentration of the serum matrix diluted to a quarter of original (1:3) ratio by using one volume of buffer solution of boric acid mixed with sodium hydroxide and two volumes of water improves the extraction efficiency. Headspace derivatization following SPME was performed by using 6 microl 20% (v/v) heptafluorobutyric anhydride ethyl acetate solution at an oil bath temperature of 270 degrees C for 10 s. The precision was below 7% for analysis for without derivatization and below 17% for headspace derivatization. Detection limits were obtained at the ng/l level, one order better obtained in headspace derivatization than those achieved without derivatization. The feasibility of applying the methods to determine amphetamine and methamphetamine in real samples was examined by analyzing serum samples from methamphetamine abused suspects. Concentrations of the amphetamine and methamphetamine ranged from 6.0 microg/l (amphetamine) to 77 microg/l (methamphetamine) in serum.

Modulation of energy deficiency in Huntington's disease via activation of the peroxisome proliferator-activated receptor gamma

Huntingtons disease (HD) is a neurodegenerative disease caused by the expansion of a CAG trinucleotide repeat in exon 1 of the huntingtin (HTT) gene. Here, we report that the transcript of the peroxisome proliferator-activated receptor-γ (PPARγ), a transcription factor that is critical for energy homeostasis, was markedly downregulated in multiple tissues of a mouse model (R6/2) of HD and in lymphocytes of HD patients. Therefore, downregulation of PPARγ seems to be a pathomechanism of HD. Chronic treatment of R6/2 mice with an agonist of PPARγ (thiazolidinedione, TZD) rescued progressive weight loss, motor deterioration, formation of mutant Htt aggregates, jeopardized global ubiquitination profiles, reduced expression of two neuroprotective proteins (brain-derived neurotrophic factor and Bcl-2) and shortened life span exhibited by these mice. By reducing HTT aggregates and, thus, ameliorating the recruitment of PPARγ into HTT aggregates, chronic TZD treatment also elevated the availability of the PPARγ protein and subsequently normalized the expression of two of its downstream genes (the glucose transporter type 4 and PPARγ coactivator-1 alpha genes). The protective effects described above appear to have been exerted, at least partially, via direct activation of PPARγ in the brain, as TZD was detected in the brains of mice treated with TZD and because a PPARγ agonist (rosiglitazone) protected striatal cells from mHTT-evoked energy deficiency and toxicity. We demonstrated that the systematic downregulation of PPARγ seems to play a critical role in the dysregulation of energy homeostasis observed in HD, and that PPARγ is a potential therapeutic target for this disease.

Determination of additives in cosmetics by supercritical fluid extraction on-line headspace solid-phase microextraction combined with gas chromatography-mass spectrometry.

A new hyphenated technique couples supercritical fluid extraction in situ derivatization and on-line headspace solid-phase microextraction to gas chromatography-mass spectrometry (SFE in situ derivatization on-line HS-SPME-GC-MS) for the determination of paraben preservatives and polyphenolic antioxidants in cosmetics. The preservatives and antioxidants were extracted from the cosmetic matrices with supercritical carbon dioxide at a pressure of 13,840 kPa. The supercritical fluid extraction was performed at 55 degrees C for 10 min of static extraction then 15 min of dynamic extraction. The extractant subsequently was derivatized in situ with the silylation reagent N,O-bis(trimethylsilyl)trifluoroacetamide with 0.1% trimethylchlorosilane. The product was then adsorbed on a polyacrylate solid-phase microextraction (SPME) fiber in the headspace. Sea sand was used as a dispersive material in the SFE step. The analytical linear ranges for the preservatives and antioxidants were found to be from 10 to 1000 ng g(-1) with RSD values below 7.8%. The detection limits ranged from 0.5 to 8.3 ng g(-1). These results are better than those obtained by using only SPME or SFE for trace preservatives and antioxidants analysis in cosmetic matrices. The new method was successfully utilized to determine the amounts of preservatives and antioxidants in real cosmetics without the need for tedious pretreatments.

Trace determination of sulfonamides residues in meat with a combination of solid-phase microextraction and liquid chromatography-mass spectrometry.

An integrated method of combining solid-phase microextraction (SPME) with liquid chromatography-mass spectrometry (LC-MS) was evaluated for determination trace amount of sulfonamides in meat products. Eight commonly used sulfonamides, sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMT), sulfamonomethoxine (SMMX), sulfamethoxazole (SMXZ), sulfaquinoxaline (SQX) and sulfadimethoxine (SDMX), were investigated in this study. Chromatography was performed on a C(18) reversed-phase column using an isocratic acetonitrile in water as the mobile phase. Fiber coated with a 65mum thickness of polydimethylsiloxane/divinylbenzene (PDMS/DVB) was used to extract sulfonamides at optimum conditions. Analytes were desorbed with static desorption in an SPME-HPLC desorbed chamber for 15min and then determined by LC-MS. The detection limits of these sulfonamides in pork were from 16mugkg(-1) (SMT) to 39mugkg(-1) (SMMX). According to the analysis, the linear range was from 50 to 2000mugkg(-1) with relative standard deviation (R.S.D.s) value below 15% (intra-day) and 19% (inter-day). The proposed method was tested by analyzing meats from a local market for sulfonamides residues. Some sulfonamides in our study were detected in the meat samples. The concentration of these residual sulfonamides ranged from 66mugkg(-1) (SDZ) to 157mugkg(-1) (SQX) in a chicken sample. The results demonstrate that the SPME-LC-MS system is highly effective in analyzing trace sulfonamides in meat products.

LC-APCI-MS method for detection and analysis of tryptanthrin, indigo, and indirubin in Daqingye and Banlangen

Abstract A rapid, selective, and sensitive LC-APCI-MS method is developed in this study for detecting and analyzing tryptanthrin, indigo, and indirubin in Daqingye and Banlangen, which are, respectively, the leaves and roots of Isatis indigotica and Strobilanthes cusia in traditional Chinese medicine. The detection of the three active components is linear in concentrations ranging from 100 to 1500ng/mL, the squared correlation coefficient is higher than 0.996, the precision as measured by the relative standard deviation is no larger than 9.5%, and the recovery is greater than 86.6%. The analysis of the 21 Banlangen samples led to considerably different conclusions on the contents of tryptanthrin, indigo, and indirubin in fresh leaves versus those in dried leaves. These results should shed some light on future plant selection and breeding. Compared with the traditional TLC and HPLC-UV methods, the new LC-APCI-MS approach has proven to be an optimal tool for detecting and analyzing the three marker compounds in the Chinese herbal medicines of Daqingye and Banlangen.

Analysis of aristolochic acid in nine sources of Xixin, a traditional Chinese medicine, by liquid chromatography/atmospheric pressure chemical ionization/tandem mass spectrometry

Aristolochic acid I (AA-I), which is a known nephrotoxin, is found in a commonly used Chinese medicine, Xixin, that originates from nine Asarum species (Aristolochiaceae) found in China. A method has been developed using reversed-phase liquid chromatography coupled with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry under the positive ion detection mode [LC/(+)APCI/MS/MS] to determine the amount of AA-I in Xixin. The limit of detection of AA-I, estimated by monitoring with LC/MS/MS, was at the low microg/l level. By applying this method to methanol extracts of nine Asarum species, the concentrations of AA-I were found to range from 3.3 ng/mg (Asarum sieboldii) to 3376.9 ng/mg (Asarum crispulatum).

Application of solid-phase microextraction and gas chromatography mass spectrometry for the determination of chlorophenols in urine

This study investigated the feasibility of applying solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry to analyze chlorophenols in urine. The SPME experimental procedures to extract chlorophenols in urine were optimized with a polar polyacrylate coated fiber at pH 1, extraction time for 50 min and desorption in GC injector at 290 degrees C for 2 min. The linearity was obtained with a precision below 10% R.S.D. for the studied chlorophenols in a wide range from 0.1 to 100 microg/l. In addition, sample extraction by SPME was used to estimate the detection limits of chlorophenols in urine, with selected ion monitoring of GC-MS operated in the electron impact mode and negative chemical ionization mode. Detection limits were obtained at the low ng/l levels. The application of the methods to the determination of chlorophenols in real samples was tested by analyzing urine samples of sawmill workers. The chlorophenols were found in workers, the urinary concentration ranging from 0.02 microg/l (PCP) to 1.56 microg/l (2,4-DCP) depending on chlorophenols. The results show that trace chlorophenols have been detected with SPME-GC-MS in the workers of sawmill where chlorophenol-containing anti-stain agents had been previously used.

A novel method of ultrasound-assisted dispersive liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry for the determination of trace organoarsenic compounds in edible oil.

A novel approach, ultrasound-assisted dispersive liquid-liquid microextraction combined with liquid chromatography-mass spectrometry (UA-DLLME with LC-MS) is demonstrated to be quite useful for the determination of trace amounts of organoarsenic compounds in edible oil. The organoarsenic compounds studied include dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and 3-nitro-4-hydroxyphenyl arsenic acid (Roxarsone). Orthogonal array experimental design (OAD) was utilized to investigate the parameter space of conditions for UA-DLLME. The optimum conditions were found to be 4 min of ultrasonic extraction using 1.25 mL of mixed solvent with 50 μL of buffer solution. Under these optimal conditions, the linear range was from 10 ng g(-1) to 500 ng g(-1) for DMA and Roxarsone, from 25 ng g(-1) to 500 ng g(-1) for MMA. Limits of detection of DMA, MMA and Roxarsone were 1.0 ng g(-1), 3.0 ng g(-1) and 5.8 ng g(-1), respectively. The precisions and recoveries also were investigated by spiking 3-level concentrations in edible oil. The recoveries obtained were over 89.9% with relative standard deviation (RSD) of 9.6%. The new approach was utilized to successfully detect trace amounts of organoarsenic compounds in various edible oil samples.

Pu-erh Tea Attenuates Hyperlipogenesis and Induces Hepatoma Cells Growth Arrest through Activating AMP-Activated Protein Kinase (AMPK) in Human HepG2 Cells

In the present study, we successively extracted the pu-erh raw tea with methanol (PR-1), chloroform (PR-2), ethyl acetate (PR-3), n-butanol (PR-4), and water (PR-5). Among these extracts, PR-3 extract contained ingredients with the most effective hypolipidemic potential and was further purified by column chromatography. Moreover, chronic administration of PR-3 provoked a significant reduction in levels of serum triglyceride and low-density lipoprotein (LDL) in rats. Our study demonstrated that fraction 5 from the PR-3 extract (PR-3-5s) showed a hypolipidemic effect in human hepatoma HepG2 cells. PR-3-5s decreased the expression of fatty acid synthase (FASN) and inhibited the activity of acetyl-coenzyme A carboxylase (ACC) by stimulating AMP-activated protein kinase (AMPK) through the LKB1 pathway. Moreover, PR-3-5s blocked the progression of the cell cycle at the G1 phase by inducing p53 expression and in turn upregulating p21 expression.