High throughput and very specific screening of anabolic-androgenic steroid adulterants in healthy foods based on stable isotope labelling and flow injection analysis-tandem mass spectrometry with simultaneous monitoring proton adduct ions and chloride adduct ions.

In this work, a stable isotope labelling-flow injection analysis-tandem mass spectrometry (SIL-FIA-MS/MS) with simultaneous monitoring [M+H]+ and [M+Cl]- method was developed for very specific and high throughput screening of anabolic-androgenic steroids (AAS) illegally added to healthy foods. Initially, a simple centrifugation step was carried out for liquid samples, and for solid samples, a solid-liquid extraction step was conducted. Afterwards, batch chemical derivatization was carried out. After adding a certain amount of 13C6-3-NPH labelled AAS standards as the internal standards, it can be directly transferred for FIA-MS/MS analysis based on the no MS response characteristics of 3-NPH. The 3-NPH labelled AAS showed dual-polarity property, observing chloride adduct ion ([M+Cl]-) in negative ion mode and proton adduct ion ([M+H]+) in positive ion mode. The average time cost for pretreatment of each sample was less than 1 min by carrying out batch processing. The subsequent FIA-MS/MS detection enabled rapid and high throughput detection. The addition of 13C6-3-NPH-labelled AAS as internal standards can correct the matrix effect to achieve accurate quantitative analysis. The detection sensitivity was also improved by 2-5 folds after 3-NPH labelling. The limits of detection (LODs) in positive MRM mode were in ranges of 0.1-0.3 ng/mL. The validated method with simultaneous monitoring [M+H]+ and [M+Cl]- was validated in the range of 6.0-1000 ng/mL with the linear coefficient (R2) greater than 0.997. Satisfactory recoveries were found to be in ranges of 93.0-108.7%. The intra-day and inter-day RSDs were in the range of 3.5-9.9% and 5.1-14.1%, respectively. No changes in detection sensitivity of the mass spectrometry and no carry-over effects were found after numerous consecutive injections of AAS derivates. Compared with previously reported methods, the proposed method proved accurate, very specific, high throughput with good sensitivity.

A simultaneous extraction/derivatization strategy coupled with liquid chromatography-tandem mass spectrometry for the determination of free catecholamines in biological fluids.

The current study presents a convenient, rapid and effective simultaneous extraction/derivatization (SEDP) strategy for effective pretreatment of catecholamines (CAs). Commercial zirconium oxide (ZrO2) nanoparticles were employed for the selective capturing of cis-diol containing CAs to remove the biological interferences and phenyl isothiocyanate (PITC) was used for derivatization to improve the ionization and to improve the chromatographic separation. The extraction and derivatization procedures were integrated into one step to simplify the sample pretreatment. Excessive derivatization reagents were removed as well, reducing the degree of contaminations in mass spectrometry. The factors affecting the SEDP process were optimized and the results showed that the detection sensitivity and chromatographic separation of CAs greatly improved compared with underivatized CAs, during LC-MS/MS analysis. Combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), quantifying the concentration of norepinephrine (NE), epinephrine (E) and dopamine (DA) in biological fluids was validated in ranges of 1-200.0 ng/mL with a satisfactory correlation coefficient (R2 > 0.997). The obtained recoveries were in the range of 91.0-109.5% with RSDs less than 9.4%. Finally, significant changes in CAs levels in urine samples of healthy people and pheochromocytoma patients were detected. The developed method offers comparative advantages in terms of sensitivity, specificity and selectivity.

Rapid Detection of mrp, epf, and sly Genes by Loop-Mediated Isothermal Amplification in Streptococcus suis.

Streptococcus suis remains a serious threat to the worldwide swine industry and human health. In this study, rapid assays for the detection of three common virulence-related factors (mrp, epf, and sly) were developed, evaluated, and applied. Loop-mediated isothermal amplification (LAMP) primers were designed using Primer Explorer V5 software. The sensitivity and specificity of the LAMP assays were determined based on sample turbidity. For all three genes, LAMP assays were performed at 62°C with a reaction time of 60 min. The detection limit of conventional polymerase chain reaction (PCR) was 1 ng/µL, 10 pg/µL, and 100 fg/µL for the epf, sly, and mrp genes, respectively. For the LAMP assays, the detection limits were 10 pg/µL, 10 fg/µL, and 100 fg/µL for epf, sly, and mrp, respectively, representing sensitivities 100-1000 times higher than those of the PCR assay. Furthermore, when the LAMP assays were applied to clinical strains, the results were consistent with those of the PCR assay, confirming the LAMP assays as rapid and reliable detection techniques. In conclusion, the LAMP assays described in this study have the potential to become standard methods to detect the virulence factors mrp, epf, and sly. To the best of our knowledge, this is the first study to report the application of LAMP to detect the mrp, epf, and sly genes.

Magnetic solid-phase extraction of tobacco-specific N-nitrosamines using magnetic graphene composite as sorbent.

Tobacco-specific N-nitrosamines are carcinogenic components in mainstream cigarette smoke. To explore tobacco-specific N-nitrosamine release levels in cigarettes, a magnetic solid-phase extraction procedure using magnetic graphene composite as sorbent for fast enrichment of tobacco-specific N-nitrosamine was developed. Under optimal conditions, a tobacco-specific N-nitrosamine determination method was successfully proposed by combining magnetic solid-phase extraction procedure and high-performance liquid chromatography coupled with tandem mass spectrometry. The method's limit of detection for tobacco-specific N-nitrosamines in mainstream cigarette smoke ranged from 0.018 to 0.057 ng/cigarette. Good linearities were obtained with correlation coefficients above 0.9992. The accuracies of tobacco-specific N-nitrosamines in a spiked mainstream cigarette smoke sample were from 89.3 to 109.4%, with a relative standard deviation of less than 11.2%. The proposed method has the merits of rapidity and high sensitivity. Finally, the method was successfully applied to tobacco-specific N-nitrosamine analysis in real samples.

Simultaneous determination of polycyclic aromatic hydrocarbons and tobacco-specific N-nitrosamines in mainstream cigarette smoke using in-pipette-tip solid-phase extraction and on-line gel permeation chromatography-gas chromatography-tandem mass spectrometry.

In this study, a silica/primary secondary amine (SiO2/PSA) was used as an in-pipette-tip solid phase extraction (SPE) sorbent for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and tobacco-specific N-nitrosamines (TSNAs) in mainstream cigarette smoke (MSS). We investigated several parameters including an extraction procedure of total particulate matter, type and amount of sorbent and on-line gel permeation chromatography parameters to obtain optimum conditions for a new strategy to target analytes. Under the optimized conditions, we developed a method for the simultaneous determination of PAHs and TSNAs in MSS by coupling in-pipette-tip SPE procedures to an on-line gel permeation chromatography-gas chromatography-tandem mass spectrometry (on-line GPC-GC-MS(2)). Our method had limits of detection for target analytes ranging from 0.01 to 0.23ng/cig. Good linearities were obtained with coefficients of determination (R(2)) greater than 0.9984 for all target analytes. Good reproducibility was obtained as intra- and inter-day precisions, and the relative standard deviations were less than 11.4 and 13.3%, respectively. The recoveries were in the range of 77.1-108.6% at different concentrations for real samples. Compared to previous standard methods for the determination of PAHs and TSNAs in MSS, our method was highly effective, fast, and had low consumption of organic solvent and a high degree of automation. Finally, our method successfully analyzed PAHs and TSNAs in real samples, and no significant deviations were observed when compared to similar analysis using standard methods.

Magnetic graphene as modified quick, easy, cheap, effective, rugged and safe adsorbent for the determination of organochlorine pesticide residues in tobacco.

In this study, magnetic graphene was used as modified quick, easy, cheap, effective, rugged and safe (QuEChERS) adsorbent for the determination of organochlorine pesticide (OCPs) residues in tobacco. To achieve the optimum conditions of modified QuEChERS procedure toward target analytes, several parameters affecting the clean-up efficiency including the amount of the adsorbent and clean-up time were investigated. Under the optimized conditions, a method for the determination of 26 OCPs residues in tobacco was established by coupling the modified QuEChERS procedure to on-line gel permeation chromatography-gas chromatography-tandem mass spectrometry (on-line GPC-GC-MS(2)). The limits of detection of proposed method for 26 OCPs residues ranged from 0.01275 to 3.150ng/g. And good linearities of the proposed method were obtained with coefficients of determination (R(2)) greater than 0.9985 for all target analytes. Good reproducibility of method was obtained as intra- and inter-day precisions, the relative standard deviations were less than 11.1 and 15.0%, respectively. The apparent recoveries were in the range of 64-126% at different concentrations for real samples. Compared with the reported methods for the determination of OCPs residues in tobacco, the proposed method has the advantages of simple to operate, low cost and high clean-up ability. Finally, the method was successfully applied to the analysis of OCPs residues in real samples.

Preparation of mesoporous silica embedded pipette tips for rapid enrichment of endogenous peptides.

Mesoporous silica embedded pipette tips (mSiO2-Tips) were successfully prepared by a simple method and applied to rapid enrichment of endogenous peptides for the first time. The prepared mSiO2-Tips showed low back pressure when solvent was pipetted up and down. As a result, mSiO2-Tip could selectively trap peptides and exclude high-MW proteins simultaneously based on size-exclusion mechanism due to the uniform mesopore structure of the sorbent bed. The in-pipette-tip SPE approach was proved to be easy-operation, sensitive and fast (less than 2 min) for the analysis of peptides, which was further successfully applied in the efficient enrichment of peptides from human plasma.

Facile fabrication of reduced graphene oxide-encapsulated silica: a sorbent for solid-phase extraction.

In this study, a facile hydrothermal reduction strategy was developed for the preparation of reduced graphene oxide-encapsulated silica (SiO2@rGO). Compared with other conventional methods for the synthesis of SiO2@rGO, the proposed strategy endowed the obtained SiO2@rGO with larger amount of immobilized rGO. The prepared functionalized silica shows remarkable adsorption capacity toward chlorophenols (CPs) and peptides. When it was used as solid-phase extraction (SPE) sorbent, a superior recovery could be obtained compared to commercial sorbents, such as C18 silica, graphitized carbon black and carbon nanotubes. Based on these, the prepared material was used as SPE sorbent for the enrichment of CPs, and a method for the analysis of CPs in water samples was established by coupling SPE with high performance liquid chromatography-ultra violet detection (SPE-HPLC/UV). In addition, the obtained SiO2@rGO was further successfully extended to the enrichment of peptides in bovine serum albumin (BSA) digests.

Quick, easy, cheap, effective, rugged and safe method with magnetic graphitized carbon black and primary secondary amine as adsorbent and its application in pesticide residue analysis.

By using magnetic graphitized carbon black and primary secondary amine (GCB/PSA/MNPs) as adsorbent, a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was proposed for pesticide residue analysis in vegetables. The magnetic adsorbent was fabricated via simple co-mixing method based on an "aggregate warp" mechanism. To achieve the optimum conditions of modified QuEChERS toward target analytes, several parameters, including the composition of analyte protectants and the amount of the adsorbents were investigated. Under the optimized conditions, a simple, rapid and effective method for the determination of 10 pesticide residues in vegetables was established by coupling modified QuEChERS to gas chromatography/mass spectrometry analysis. The detection limits of the proposed method for 10 pesticides ranged from 0.39 to 8.6ng/g. Good linearity (R value≥0.990) was achieved at concentration levels of 10-200ng/g, and acceptable method reproducibility was found as intra- and inter-day precisions, yielding the relative standard deviations less than 10.7% and 13.4%, respectively. The recoveries were in the range of 69.9-125.0% at different concentrations for real samples. Compared with the reported methods for the determination of a large number of samples, the proposed method has the advantage of less time-consuming in clean-up procedure.

Substrateless graphene fiber: a sorbent for solid-phase microextraction.

In current study, a substrateless graphene fiber was successfully prepared by a simple hydrothermal strategy and used as solid-phase microextraction (SPME) sorbent. Five organochlorine pesticides (OCPs) were employed as model analytes to evaluate the performance of as-prepared graphene fiber. The results showed that the graphene fiber exhibited higher extraction efficiencies, higher thermal stability (up to 310°C), better reproducibility, and longer service life (more than 180 times reuse) than commercial fibers. In addition, the method for the determination of OCPs was proposed by coupling headspace (HS)-SPME technique with gas chromatography/electron capture detector (HS-SPME-GC/ECD). The proposed HS-SPME-GC/ECD method showed low limits of detection (0.83-11.5 ng/L), wide linear dynamic ranges (more than 2 orders of magnitude), and acceptable reproducibility (RSD<10.9%). Finally, the proposed method was successfully applied to the analysis of OCPs in environmental water samples with good recoveries (81-121%) and satisfactory precisions (RSD<9%).

Fast microextraction of phthalate acid esters from beverage, environmental water and perfume samples by magnetic multi-walled carbon nanotubes.

In this work, magnetic carbon nanotubes (CNTs) were prepared by mixing the magnetic particles and multi-walled carbon nanotubes dispersed solutions. Due to their excellent adsorption capability towards hydrophobic compounds, the magnetic CNTs were used as adsorbent of magnetic solid-phase extraction (MSPE) to extract phthalate acid esters (PAEs), which are widely used in many consumable products with potential carcinogenic properties. By coupling MSPE with gas chromatography/mass spectrometry (GC/MS), a rapid, sensitive and cost-effective method for the analysis of PAEs was established. Our results showed that the limits of detection (LODs) of 16 PAEs ranged from 4.9 to 38 ng L(-1), which are much lower compared to the previously reported methods. And good linearities of the detection method were obtained with correlation coefficients (R(2)) between 0.9821 and 0.9993. In addition, a satisfying reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 11.7% and 14.6%, respectively. Finally, the established MSPE-GC/MS method was successfully applied to the determination of PAEs from bottled beverages, tap water and perfume samples. The recoveries of the 16 PAEs from the real samples ranged from 64.6% to 125.6% with the RSDs less than 16.5%. Taken together, the MSPE-GC/MS method developed in current study provides a new option for the detection of PAEs from real samples with complex matrices.

Rapid magnetic solid-phase extraction based on magnetic multiwalled carbon nanotubes for the determination of polycyclic aromatic hydrocarbons in edible oils.

In this study, magnetic multiwalled carbon nanotubes were fabricated by a simple method and applied to magnetic solid-phase extraction (MSPE) of eight heavy molecular weight polycyclic aromatic hydrocarbons (PAHs) including chrysene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene from edible oil samples. Several parameters affecting the extraction efficiency were investigated, including the type and volume of desorption solvent, extraction and desorption time, washing solution and the amount of sorbent. Under the optimized conditions, a simple and effective method for the determination of PAHs in edible oils was developed by coupling with gas chromatography-mass spectrometry (GC-MS). The whole pretreatment process was rapid, and it can be accomplished within 10 min. The limits of quantitation for the target PAHs were found to be 0.34-2.9 ng/g. The recoveries in oil sample were in the range 87.8-122.3% with the RSDs less than 6.8% (intraday) and 9.6% (interday). This method was successfully applied to the analysis of PAHs in seven kinds of edible oils from local markets.

An anionic exchange stir rod sorptive extraction based on monolithic material for the extraction of non-steroidal anti-inflammatory drugs in environmental aqueous samples.

In this study, a stir rod sorptive extraction (SRSE) adsorbent material was prepared by coating poly(4-vinylpyridine-co-ethylene glycol dimethacrylate) [poly(VP-co-EDMA)] monolithic polymer on stir rod, and then applied to the extraction of three non-steroidal anti-inflammatory drugs (NSAIDs) in environmental aqueous samples. The preparation conditions of monolithic material such as the amount of porogen and the ratio of functional monomer to cross-linker were investigated. To achieve the best extraction efficiency, several parameters, including pH value of sample solution, salt concentration in sample matrix, desorption solvent, extraction time, and desorption time, were optimized. By combining SRSE and high performance liquid chromatography with ultraviolet detector, a SRSE-HPLC/UV method for the determination of NSAIDs in environmental aqueous samples was proposed successfully. The limits of detection (LODs) of the developed method for three NSAIDs ranged between 0.09 and 0.25 ng/mL. Good method reproducibility presented as intra- and inter-day precisions were also obtained with the relative standard deviations (RSDs) less than 8.7% and 9.8%, respectively.

A magnetite/oxidized carbon nanotube composite used as an adsorbent and a matrix of MALDI-TOF-MS for the determination of benzo[a]pyrene.

A magnetite/oxidized carbon nanotube composite, Fe(3)O(4)@SiO(2)/OCNT, was fabricated in a simple way, and it was successfully used as a magnetic solid-phase extraction sorbent and a significant matrix of the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the detection of benzo[a]pyrene (BaP).

Magnetic retrieval of graphene: extraction of sulfonamide antibiotics from environmental water samples.

A new technique of retrieving graphene from aqueous dispersion was proposed in the present study. Two-dimensional planar graphene sheets were immobilized onto silica-coated magnetic microspheres by simple adsorption. The graphene sheets were used as adsorbent material to extract six sulfonamide antibiotics (SAs) from water samples. After extraction, they were conveniently separated from the aqueous dispersion by an external magnetic field. Under the optimal conditions, a rapid and effective determination of SAs in environmental water samples was achieved. The limits of detection for six SAs ranged from 0.09 to 0.16 ng/mL. Good reproducibility was obtained. The relative standard deviations of intra- and inter-day analysis were less than 10.7% and 9.8%, respectively.

Graphene-polymer composite: extraction of polycyclic aromatic hydrocarbons from samples by stir rod sorptive extraction.

Due to the excellent mechanical, thermal and electrical properties, graphene/polymer composite is expected to have a variety of applications in analytical chemistry. In this study, a new poly(ethylene glycol dimethacrylate)/graphene composite was prepared by in situ polymerization. The new composite was used for the first time as the extraction coating of stir rod sorptive extraction for the preconcentration of polycyclic aromatic hydrocarbons (PAHs) from water samples. Because of the high specific surface area and π-π electrostatic stacking properties of graphene, the graphene-polymer composite showed higher extraction efficiencies towards most target PAHs from water samples than the neat polymer. Under the optimal conditions, a method for the determination of PAHs in water samples was proposed based on the combination of stir rod sorptive extraction (SRSE) and gas chromatography-mass spectrometry (GC-MS). The limit of detection (LODs) of the developed method for 16 PAHs ranged from 0.005 to 0.429 ng mL-1, depending on the compound. Good reproducibility of method was obtained as intra- and inter-day precisions, the relative standard deviations (RSDs) were less than 12.5% and 12.6%, respectively.

Stir rod sorptive extraction with monolithic polymer as coating and its application to the analysis of fluoroquinolones in honey sample.

A stir rod sorptive extraction (SRSE) with monolithic polymer as coating was proposed to avoid the friction loss of coating during the stirring process. In our study, poly(2-acrylamide-2-methylpropanesulfonic acid-co-octadecyl methacrylate-co-ethylene glycol dimethacrylate) [poly(AMPS-co-OCMA-co-EDMA)] monolithic polymer was used as a coating of SRSE. The effect of concentration of porogen on SRSE performance was studied. Four fluoroquinolones (FQs) were selected as testing analytes to evaluate the extraction efficiency of SRSE. To achieve the optimum extraction conditions of SRSE towards FQs, several parameters, including extraction time, extraction temperature, stirring rate, sample solution pH and contents of inorganic salt in the sample solution were investigated. Under the optimized conditions of SRSE, a method for the determination of FQs in honey sample was proposed based on the combination of SRSE with liquid chromatography and electrospray ionization mass spectrometry (SRSE/LC/ESI-MS). The detection limits (LODs) of the proposed method for four FQs ranged from 0.06 to 0.14ng/g and the recoveries were in the range of 70.3-122.6% at different concentrations for honey samples. Good method reproducibility was found as intra- and inter-day precisions, yielding the relative standard deviations less than 11.9% and 12.4%, respectively. The results show that SRSE with poly(AMPS-co-OCMA-co-EDMA) monolithic polymer as coating possessed good extraction capacity towards FQs in honey samples. Finally, the monolithic polymer coated stir rod was demonstrated to be reused at least 60 times.