An analytical method was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) and 15 nitrated PAHs (NPAHs) in ambient air particulates by applying an in-house built integrated ultrasonic extraction device followed by gas chromatography coupled with mass spectrometry (GC–MS). After integrated ultrasonic extraction in the extraction cell, the extract solution was released through the opened valve into a purification tube containing adsorbents for purification, then concentrated and analyzed by GC–MS. Compared to previously reported methods, such as Soxhlet extraction and accelerated solvent extraction, this method has greatly shortened the pretreatment time, simplified the pretreatment process, and reduced experimental costs. A series of experimental conditions, including extraction solvent, adsorbents, and elution solvent, were systematically studied and optimized. Owing to its superior ability in purifying particulate matter samples, a combination of flower-like-texture Mg–Al layered double oxide (Mg–Al-LDO) and silica gel was selected as the optimized adsorbent. To our knowledge, few reports on this combination of materials exist. The limits of detection (LODs) of 16 PAHs and 15 NPAHs ranged from 0.018 to 1.7 and from 0.035 to 0.60 ng g−1, respectively. Limits of quantifications (LOQs) were from 0.061 to 5.7 and 0.12 to 2.0 ng g−1 for 16 PAHs and 15 NPAHs, respectively. Recoveries at three spiked concentration levels ranged from 81.6 to 116%. The relative standard deviations (RSDs) were less than 6.5% in all cases. The proposed analytical method was proved to be practical and suitable technique for PAH and NPAH analysis in real ambient air particulate samples.

•A novel fluorescent nanosensor has been developed.•The sensor exhibited highly sensitive and selective response to FA.•The fluorescence quenching was fitted to Stern–Volmer equation.•The linear response range was 1–200 μM with a limit of detection of 0.1 μM.A novel fluorescent nanosensor for detecting folic acid (FA) in aqueous media has been developed based on 8-aminonaphthalene-1,3,6-trisulfonate (ANTS) anchored to the surface of Zn-Al-CO3-layered double hydroxides (LDH) particles. The nanosensor showed high fluorescence intensity and good photostability due to a strong coordination interaction between surface Zn2+ ions of Zn-Al-CO3-LDH and N atoms of ANTS, which were verified by result of X-ray photoelectron spectroscopy (XPS). ANTS-anchored on the surface of Zn-Al-CO3-LDH restricted the intra-molecular rotation leading to ANTS-anchored J-type aggregation emission enhancement. ANTS-anchored Zn-Al-CO3-LDH particles exhibited highly sensitive and selective response to FA over other common metal ions and saccharides present in biological fluids. The proposed mechanism was that oxygen atoms of -SO3 groups in ANTS-anchored on the surface of Zn-Al-CO3-LDH were easily collided by FA molecules to form potential hydrogen bonds between ANTS-anchored and FA molecules, which could effectively quench the ANTS-anchored fluorescence. Under the simulated physiological conditions (pH of 7.4), the fluorescence quenching was fitted to Stern-Volmer equation with a linear response in the concentration range of 1 μM to 200 μM with a limit of detection of 0.1 μM. The results indicate that ANTS-anchored Zn-Al-CO3-LDH particles can afford a very sensitive system for the sensing FA in aqueous solution.

•Three dimensionally honeycomb Mg-Al layered double oxide (TDH-Mg-Al-LDO) was used as a novel solid phase extraction sorbent.•TDH-Mg-Al-LDO and graphitized carbon black (GCB) was packed in the same column.•15 pesticide residues in green tea were purified and determined simultaneously.Pesticide residues exceeding standard in green tea is a widespread problem of the world’s attention, containing organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), and pyrethroids. In this research, three dimensionally honeycomb Mg-Al layered double oxide (TDH-Mg-Al-LDO) combined with graphitized carbon black (GCB), packed as a column, was used as a novel solid phase extraction sorbent, applying in simultaneous determination of 15 pesticide residues in green tea coupled with GC–MS. Compared with different type of SPE column, it showed that TDH-Mg-Al-LDO exhibited great advantages in the extraction of 15 pesticide residues from green tea, which was seldom reported before. Different experiment conditions, such as combination order of Mg-Al-LDO and GCB, dosage of sorbents, type and volume of eluting solvent were thoroughly studied and optimized. The limits of detection (LODs) of 15 pesticides ranged from 0.9 to 24.2 ng/g and the limits of quantifications (LOQs) were ranging from 3.0 to 80.0 ng/g. The recoveries using this method at three spiked concentration levels (10, 100 and 500 ng/g for Fenthion, P,P′-DDE, O,P′-DDT, P,P′-DDD and Bifenthrin, 100, 500 and 2000 ng/g for the others) range from 71.1 to 119.0%. The relative standard deviation (RSD) was from 0.1 to 7.6% in all case. The result indicated that the proposed analytical method had been successfully applied for the simultaneous determination of 15 pesticide residues in commercial green tea.

•16 pesticides in tea were extracted and purified by matrix solid phase dispersion and further SPE process.•PVPP was served as a new sorbent in the SPE process to further purify 16 pesticides in tea.•The established method tested by 8 tea samples is reliable and accurate.•16 pesticides in 8 samples were below the MRL values by the Regulation (EC), except for methomyl in black tea.A novel method based on matrix solid phase dispersion (MSPD) coupled with liquid chromatography-tandem mass spectrometry was established for the determination and the quantification of 16 pesticides (5 carbamates, 4 organophosphorus, and 7 pyrethroids) in various tea. Matrix dispersive sorbent and further cleanup sorbent were applied to improve the efficiency of extraction and purification. PVPP, PSA and GCB were introduced as further cleanup sorbents packed at the bottom of the MSPD to remove co-eluting matrix components. Different experiment conditions, such as type of eluting solvent, its volume, matrix dispersive sorbent, sample to matrix dispersive sorbent mass ratio, and the dosage of cleanup sorbents were thoroughly studied and optimized. It was found that polyvinylpolypyrrolidone (PVPP), an inexpensive and excellent absorbent, could effectively remove polyphenols in tea, which was seldom reported before. The method showed satisfactory linearity over the range assayed 0.9986–0.9999 (1–500 ng g−1 for 5 carbamates and 4 organophosphorus, 2–800 ng g−1 for 7 pyrethroids), the limits of detections (LODs) ranged from 0.01 to 1.38 ng g−1, and the limits of quantifications (LOQs) were ranging from 0.03 to 4.74 ng g−1. The recoveries using this method at three spiked concentration levels (10, 100, and 500 ng g−1) range from 87.7 to 99.6%. The relative standard deviation (RSD) was from 0.2 to 9.6% in all case. The proposed analytical method has been successfully applied for the analysis of 16 pesticides in commercial tea.

•Photostability of the two dyes can be greatly improved by Mg–Al–CO3-LDH matrix.•Adsorbed compound has much higher photostability by a chemisorption interaction.•FL intensity and stability of adsorbed compounds were greatly increased under N2.Two azoic dyes 4-aminoazobenzene-4-sulfonic (AS) and ethyl orange (EO) were adsorbed on or intercalated into Mg–Al–CO3 layered double hydroxide (LDH) for photostability enhancement. Fluorescence analysis results showed that the photostability of two dyes could be greatly improved after being adsorbed on the surface of Mg–Al–CO3-LDH matrix. Furthermore, photostability of adsorbed dyes was superior to that of intercalated dyes. It was suggested that AS or EO was adsorbed on LDHs surface through a strong chemisorption interaction, resulting in the enhancement of photostability. After the UV irradiation under N2 atmosphere, the absorbed dyes not only show great increase of fluorescence intensity but also exhibited high stability against UV irradiation. This work provides a feasible approach to enhance the photostability of azoic dye confined in an inorganic two-dimensional (2D) matrix via changing the microenvironment, which may be considered to be a promising method of improving photostability of solid fluorescent materials.

In this paper, 4-benzoylbenzoic acid (4-BBA) and 2-naphthalenesulfonic acid (2-NSA) were intercalated or co-intercalated into the layered double hydroxide (LDH) [Co0.66Al0.34(OH)2](CO3)0.17·0.49H2O by the method of ion-exchange. Powder X-ray diffraction, Fourier transform infrared spectroscopy, TG-DTA, X-ray photoelectron spectroscopy and photoluminescence spectra were used to characterize the structural and photophysical properties of the obtained compounds. It was found that Co2+ ions in the layers were coordinated with the guest molecules 2-NSA in the interlayer region, resulting in the intercalation compound Co-Al-2-NSA-LDH enhancing the blue emission of 2-NSA at 460 nm. The geometries and electronic structures of the guest molecules and their singlet vertical excitation energies and oscillator strengths were investigated at the B3LYP/6-31G level by density functional theory (DFT) and time dependent DFT calculations using G03w. The fluorescence polarization method was applied to test the preferential orientation of the interlayer 4-BBA and 2-NSA molecules. It indicated that spatial distribution of the guest molecules in the layer was a rather ordered arrangement and indicated that 4-BBA and 2-NSA were intercalated or co-intercalated between sheets of Co-Al-LDH as a bilayer interdigitated form. There was a coordinate possibility between Co-Al-LDH and the organic chromophores containing a sulfonic group, and intermolecular energy transfer from 2-NSA to 4-BBA in the layers might happen for the co-intercalation compound. So, this work provides new opportunities to design functional material by the combination of Co-Al-LDH with various types of organic chromophores, which will be very valuable.

•7 synthetic musks in cream were separated and purified by SLE and LC-Alumina-N SPE.•Water was added in the mixed solution to extract 7 synthetic musks from cream.•The established method tested by 28 cream products is reliable and accurate.•7 synthetic musks in 28 samples were below the MRL values by the Regulation (EC).A new method for the simultaneous determination of 7 synthetic musks (musk amberette, musk tibetene, musk moskene, musk ketone, musk xylene, phantolide, and tonalide) in cream by means of supporting liquid extraction (SLE) coupled with LC-Alumina-N SPE, then followed by GC–MS/MS has been established. In this study, 7 synthetic musks are extracted and pre-purified by a mixture solution of water and isopropanol from cream, and separated and purified by tandem columns containing SLE column and LC-Alumina-N SPE column, which were seldom reported before. Ultrasonic and mechanical shaking were applied to improve the extraction efficiency. Different experiment conditions, such as the type of extraction solution, extraction time of ultrasonic and mechanical shaking, the type of SLE and SPE column, and matrix effects were optimized and the recoveries of 7 synthetic musks for each part were above 86.61%. In addition, the use of isotope internal standards was systemically discussed. The method showed satisfactory linearity over the range assayed (5–1000 ng g−1), and the limits of detections (LODs) ranged from 0.15 to 4.86 ng g−1, and the limits of quantifications (LOQs) were ranging from 0.49 to 16.21 ng g−1. The recoveries using this method at three spiked concentration levels (10, 100, and 1000 ng g−1) range from 85.6% to 109%. The relative standard deviation was lower than 9.8% in all case. The proposed analytical method has been successfully applied for the analysis of 7 synthetic musks in commercial cream.

This paper presents the development of a precise and accurate analytical method for the determination of 12 incurred pesticides in tea using gas chromatography-high resolution isotope dilution mass spectrometry. The extraction efficiency of accelerated solvent extraction (ASE) was evaluated in which four extraction parameters, solvent, temperature, number of static cycles and static time for spiked and incurred samples, have been investigated systematically. The optimized solvent and temperature were found to be an acetone–n-hexane mixture (2:1, v/v) and 120 °C for both spiked and incurred samples. However, it was found that the number of static cycles and static time for the spiked tea sample were different from that for the incurred sample. Two cycles of 5 min each were set for the extraction of pesticides from the spiked tea, while two cycles of 10 min each were set for extraction from the incurred sample. The overall average recoveries using this method at three spiked concentration levels (50, 200, 1000 ng g−1) ranged from 95.96% to 102.04%, and relative standard deviations (RSDs) were in the range 0.83–3.12% (n = 6) for all analytes. The limits of detection (LODs) ranged from 0.02 to 10.83 ng g−1, and the limits of quantification (LOQs) ranged from 0.09 to 38.74 ng g−1. The RSDs (n = 6) of two incurred tea samples were in the range 1.04–2.93%, and 1.01–2.96%, respectively, which are better than those obtained using a QuEChERS-GC/MS/MS method. This indicates that the developed method is more suitable for the precise determination and research of pesticides incurred in tea.

An accurate, rapid and reliable method for the simultaneous determination of 11 pesticide residues in tea by liquid chromatography–electrospray ionization tandem mass spectrometry has been established. Samples were purified by a modified QuEChERS method, followed by analysis by LC–ESI(+)-MS/MS and quantification using isotope internal standards. In this study, different extraction conditions, such as soaking time, extraction time of pesticides from the real tea samples and spiked samples, were optimized and compared. It was found that pesticides in real tea needed more time to be soaked and extracted than those in spiked tea for complete extraction. In order to eliminate the matrix effect and obtain satisfactory recoveries, the dosage of sorbents PSA (125, 250, 400, 600, 800, 1000, 1200 mg) and GCB (0, 25, 50, 250, 500 mg) was optimized in this study, and 800 mg PSA, 25 mg GCB, 750 mg MgSO4 were used in the purification process. In addition, the use of isotope internal standards and blank matrix matched standard calibration are discussed in depth. When the concentration range of 11 pesticides was 1–500 ng g−1, the linear correlation coefficients were 0.9981–0.9999. At the low, medium and high fortification levels of 2–100 ng g−1 (n = 6), recoveries were within 88–103%. The relative standard deviation was between 0.2% and 7.6%, and the limits of detection (LODs) ranged from 0.02 to 0.38 ng g−1 for 11 pesticides. It was found that the method was successfully applied to the qualitative and quantitative analysis of pesticides in actual commercial tea samples.

A rapid and reliable method for simultaneous determination of methamphetamine (MAM) and ketamine (KET) in human hair was developed. MAM and KET in hair samples were collected using ultrasonication with methanol/5 M hydrochloric acid (HCl) for 1 hour, and detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this experiment, drug-free human hairs were added into standard solution and kept for 16 hours in order to minimize the difference between blank spiked samples and authentic samples. D8-MAM as internal standard, the linear ranges of MAM and KET were 1–100 pg mg−1 and 2–200 pg mg−1 with correlation coefficients greater than 0.999, respectively. The limit of detection (S/N ≥ 3) was 0.03 pg mg−1 for MAM and 0.06 pg mg−1 for KET, the limit of quantification was (S/N ≥ 10) 0.09 pg mg−1 for MAM and 0.21 pg mg−1 for KET. Accuracy evaluated by recovery spiked at three different concentrations, was in the ranges of 91–114% for MAM and 88–119% for KET. The intra- and inter-day standard deviations of all analysis results were less than 3.50%. This method was applied to analyze residue levels of MAM and KET in human hair samples.

Ethyl Orange (EO) and 4-aminoazobenzene-4-sulfonic (AS) anions with Donor-∏-Acceptor structure have been intercalated into the layered double hydroxide (LDH), [Mg0.66 Al0.34 (OH)2] (CO3)0.17·0.67H2O or adsorbed on the external surface of the host by the method of ion-exchange procedures. The photoabsorption and fluorescence properties of the obtained compounds were different from the pure solid phase of EO and AS. It was suggested that the photophysical properties of guests were closely related to the geometry and electrical structure of the guest molecule, which can affect the distribution and orientation of the guests in the layers or on the surface of the host. The host–guest interactions modulate photophysical properties of guest. In addition, the guest having higher molecular dipole moments surface exchanged on MgAlCO3LDH are beneficial to the enhancement of the blue emission than that of intercalation into LDH.Graphical abstractEmission spectra of (a) EO (b) EO surface exchanged on MgAlCO3LDH (c) MgAlEOLDH. Emission spectra of (a) AS (b) MgAlASLDH (c) AS surface exchanged on MgAlCO3LDH. The guests having higher molecular dipole moments surface exchanged on MgAlCO3LDH are beneficial to the enhancement of the blue emission than that of intercalation into LDH.Highlights► EO and AS are intercalated into LDHs or adsorbed on the external surface of LDHs. ► The host–guest interactions modulate photophysical properties of the guest. ► The guests having higher molecular dipole moments can enhance the blue emission.

The aim of this study was to develop a headspace solid-phase microextraction/gas chromatography-isotope dilution mass spectrometry (HS-SPME/GC-IDMS) method for the simultaneous quantification of 8 pesticides in tea samples. The thermodynamic equilibrium between analytes and isotope labeled analogues was studied in this paper. In addition, different parameters affecting pesticide extraction by HS-SPME were considered and optimized, including type of fiber coating, extraction temperature/time, and desorption temperature/time. In the optimized method, the isotopic labels spiked in incurred samples were equilibrated for 15 min before HS-SPME, and analytes were absorbed for 70 min at 70 °C in the sample headspace with a 100 μm polydimethylsiloxane (PDMS) fiber. By using the isotopic dilution technique, the relative standard deviation (RSD) for 8 analytes was improved to 3.7–10.2%, compared with the values of 6.5–26.7% using the traditional external standard method. The recoveries were between 86.7 and 112.8%, and the limits of detection (LODs) ranged from 1.2 to 19.6 ng g−1 (except cypermethrin, 22.1 ng g−1). Compared with the conventional sample preparation methods, the proposed method has the advantage of being quick, easy to operate, highly sensitive and also solvent saving. The optimized HS-SPME/GC-IDMS method was not only suitable for qualitative analysis but also could be successfully applied to the quantitative analysis of pesticides in tea.

The aim of this study was to develop a headspace solid-phase microextraction/gas chromatography-isotope dilution mass spectrometry (HS-SPME/GC-IDMS) method for the simultaneous quantification of 8 pesticides in tea samples. The thermodynamic equilibrium between analytes and isotope labeled analogues was studied in this paper. In addition, different parameters affecting pesticide extraction by HS-SPME were considered and optimized, including type of fiber coating, extraction temperature/time, and desorption temperature/time. In the optimized method, the isotopic labels spiked in incurred samples were equilibrated for 15 min before HS-SPME, and analytes were absorbed for 70 min at 70 °C in the sample headspace with a 100 μm polydimethylsiloxane (PDMS) fiber. By using the isotopic dilution technique, the relative standard deviation (RSD) for 8 analytes was improved to 3.7–10.2%, compared with the values of 6.5–26.7% using the traditional external standard method. The recoveries were between 86.7 and 112.8%, and the limits of detection (LODs) ranged from 1.2 to 19.6 ng g−1 (except cypermethrin, 22.1 ng g−1). Compared with the conventional sample preparation methods, the proposed method has the advantage of being quick, easy to operate, highly sensitive and also solvent saving. The optimized HS-SPME/GC-IDMS method was not only suitable for qualitative analysis but also could be successfully applied to the quantitative analysis of pesticides in tea.

A rapid and reliable method for simultaneous determination of methamphetamine (MAM) and ketamine (KET) in human hair was developed. MAM and KET in hair samples were collected using ultrasonication with methanol/5 M hydrochloric acid (HCl) for 1 hour, and detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this experiment, drug-free human hairs were added into standard solution and kept for 16 hours in order to minimize the difference between blank spiked samples and authentic samples. D8-MAM as internal standard, the linear ranges of MAM and KET were 1–100 pg mg−1 and 2–200 pg mg−1 with correlation coefficients greater than 0.999, respectively. The limit of detection (S/N ≥ 3) was 0.03 pg mg−1 for MAM and 0.06 pg mg−1 for KET, the limit of quantification was (S/N ≥ 10) 0.09 pg mg−1 for MAM and 0.21 pg mg−1 for KET. Accuracy evaluated by recovery spiked at three different concentrations, was in the ranges of 91–114% for MAM and 88–119% for KET. The intra- and inter-day standard deviations of all analysis results were less than 3.50%. This method was applied to analyze residue levels of MAM and KET in human hair samples.

This paper presents the development of a precise and accurate analytical method for the determination of 12 incurred pesticides in tea using gas chromatography-high resolution isotope dilution mass spectrometry. The extraction efficiency of accelerated solvent extraction (ASE) was evaluated in which four extraction parameters, solvent, temperature, number of static cycles and static time for spiked and incurred samples, have been investigated systematically. The optimized solvent and temperature were found to be an acetone–n-hexane mixture (2:1, v/v) and 120 °C for both spiked and incurred samples. However, it was found that the number of static cycles and static time for the spiked tea sample were different from that for the incurred sample. Two cycles of 5 min each were set for the extraction of pesticides from the spiked tea, while two cycles of 10 min each were set for extraction from the incurred sample. The overall average recoveries using this method at three spiked concentration levels (50, 200, 1000 ng g−1) ranged from 95.96% to 102.04%, and relative standard deviations (RSDs) were in the range 0.83–3.12% (n = 6) for all analytes. The limits of detection (LODs) ranged from 0.02 to 10.83 ng g−1, and the limits of quantification (LOQs) ranged from 0.09 to 38.74 ng g−1. The RSDs (n = 6) of two incurred tea samples were in the range 1.04–2.93%, and 1.01–2.96%, respectively, which are better than those obtained using a QuEChERS-GC/MS/MS method. This indicates that the developed method is more suitable for the precise determination and research of pesticides incurred in tea.

An accurate, rapid and reliable method for the simultaneous determination of 11 pesticide residues in tea by liquid chromatography–electrospray ionization tandem mass spectrometry has been established. Samples were purified by a modified QuEChERS method, followed by analysis by LC–ESI(+)-MS/MS and quantification using isotope internal standards. In this study, different extraction conditions, such as soaking time, extraction time of pesticides from the real tea samples and spiked samples, were optimized and compared. It was found that pesticides in real tea needed more time to be soaked and extracted than those in spiked tea for complete extraction. In order to eliminate the matrix effect and obtain satisfactory recoveries, the dosage of sorbents PSA (125, 250, 400, 600, 800, 1000, 1200 mg) and GCB (0, 25, 50, 250, 500 mg) was optimized in this study, and 800 mg PSA, 25 mg GCB, 750 mg MgSO4 were used in the purification process. In addition, the use of isotope internal standards and blank matrix matched standard calibration are discussed in depth. When the concentration range of 11 pesticides was 1–500 ng g−1, the linear correlation coefficients were 0.9981–0.9999. At the low, medium and high fortification levels of 2–100 ng g−1 (n = 6), recoveries were within 88–103%. The relative standard deviation was between 0.2% and 7.6%, and the limits of detection (LODs) ranged from 0.02 to 0.38 ng g−1 for 11 pesticides. It was found that the method was successfully applied to the qualitative and quantitative analysis of pesticides in actual commercial tea samples.