Cucurbit[8]uril-mediated SERS plasmonic nanostructures with sub-nanometer gap for the identification and determination of estrogens.

The SERS intensity of analytes is primarily influenced by the density and distribution of hotspots, which are often difficult to manipulate or regulate. In this study, cucurbit[8]uril (CB[8]), a kind of rigid macrocyclic molecule, was introduced to achieve ~ 1-nm nanogap between gold nanoparticles to increase the density of SERS hotspots. Three kinds of estrogens (estrone (E1), bisphenol A (BPA), and hexestrol (DES)) which are molecules with weak SERS signals were targeted in the hotspots by CB[8] to further improve the sensitivity and selectivity of SERS. It was demonstrated that CB[8] can link gold nanoparticles together through carbonyl groups. In addition, the host-guest interaction of CB[8] and estrogens was proved from the nuclear magnetic resonance hydrogen and infrared spectra. In the presence of CB[8], the SERS intensities of E1, BPA, and DES were increased to 19-fold, 74-fold, and 4-fold, respectively, and the LOD is 3.75 µM, 1.19 µM, and 8.26 µM, respectively. Furthermore, the proposed SERS method was applied to actual milk sample analysis with recoveries of E1 (85.0 ~ 112.8%), BPA (83.0 ~ 103.7%), and DES (62.6 ~ 132.0%). It is expected that the proposed signal enlarging strategy can be applied to  other analytes after further development.

Controlling persistent luminescence in nanocrystalline phosphors.

Persistent luminescent phosphors can store light energy in advance and release it with a long-lasting afterglow emission. With their ability to eliminate in situ excitation and store energy for long periods of time, they are promising for broad applications, including background-free bioimaging, high-resolution radiography, conformal electronics imaging and multilevel encryption. This Review provides an overview of various strategies for trap manipulation in persistent luminescent nanomaterials. We highlight key examples in the design and preparation of nanomaterials with tunable persistent luminescence, particularly in the near-infrared range. In subsequent sections, we cover the most current developments and trends concerning the use of these nanomaterials in biological applications. Moreover, we assess their advantages and disadvantages compared with conventional luminescent materials for biological applications. We also discuss future research directions and challenges, such as insufficient brightness at the single-particle level, and possible solutions to these challenges.

Dumbbell-like upconversion nanoparticles synthesized by controlled epitaxial growth for light-heat-color tri-modal sensing of carcinoembryonic antigen.

Accurate quantitative analysis of tumor markers in a wide linear range has important practical significance towards complex clinical samples in cancer identification and monitoring of tumor development stages, but remains challenging. Herein, three-layer dumbbell-like upconversion nanoparticles NaErF4:Tm@NaYF4@NaNdF4 (labeled as UCNPs) combined with G-quadruplex (G4) DNAzyme are reported for tri-modal sensing of carcinoembryonic antigen (CEA) in a wide range using upconversion luminescence (UCL), photothermal and catalysis signal readouts. Initially, dumbbell-like UCNPs were controlled synthesized by a three-dimensional epitaxial growth strategy through tuning the concentration of Nd precursors. After surface functionalization, G4zyme-UCNPs-cDNA/Apt-MB was subsequently fabricated by biotin-streptavidin interaction and DNA hybridization. Quantitative detection of CEA was achieved by competitive interaction and magnetic separation, and the intensities of tri-modal signals (light, heat and catalysis-based chrominance) of dissociative probes are linearly related to the concentration of CEA. The results showed that the tri-modal sensing method exhibited a wide linear range (0.005-2000 ng/mL) and low limit of detection (LOD) across three models: the luminescence model (0.005-50 ng/mL, LOD = 0.910 pg/mL), the catalysis model (10-1000 ng/mL, LOD = 0.387 ng/mL), and the temperature model (50-2000 ng/mL, LOD = 1.114 ng/mL). These findings suggest that the tri-modal sensing platform is suitable for use in the analysis of a wide range of complex and diverse clinical samples.

Electrochemically assisted wide area Raman with standard curved surface quantification method.

Reproducibility is still a great challenge for surface-enhanced Raman scattering (SERS), because the uncontrollable fabrication of SERS substrates or the uneven distribution of samples on the substrate result in the signal fluctuation with or between the substrates. Herein, a novel SERS quantitative method with good reproducibility was proposed. It is based on the basic principle that the SERS signal intensity is not only related to electromagnetic enhancement and the concentration of sample, but also related to the specific surface area of the substrate. The surface area information of the substrate is obtained through electrochemical technology, and then introduced into the standard curve with the linear relationship of concentration of sample and SERS intensity as a new variable to obtain a 3D standard curved surface, which effectively corrects the signal difference between the substrates, and combines the wide area Raman method to reduce the difference within the substrate, thereby improving the reproducibility of SERS quantitative detection. Using malachite green (MG) as the probe molecule and using cyclic voltammetry to calculate the substrate area fitted plane model (CV-standard curved surface), the root mean square error (RMSE) of the predicted result is 0.26 and the relative error (RE) is 0.25. It shows that the detection error significantly reduces comparing with the traditional standard curve method. Also, the proposed method can be used in other SERS quantitative detection and has potential application prospects.

Autofluorescence free detection of carcinoembryonic antigen in pleural effusion by persistent luminescence nanoparticle-based aptasensors.

Carcinoembryonic antigen (CEA) is an important biomarker in the diagnosis of cancer. The increase of CEA in malignant pleural effusion appears earlier and possesses higher clinical diagnostic value than that in the serum. Conventional fluorescent probes suffer from the interference of strong biotissue auto-fluorescence, which limits severely their applications in biology detection. Herein, a novel fluorescence aptasensor was designed with near-infrared persistent luminescence nanoparticles (PLNPs) for accurate detection of carcinoembryonic antigen in pleural effusion by FRET quenching and recovery mechanism. The strong background interference from the autofluorescence of pleural effusion samples can be effectively eliminated and extra increments of measured values originated from the background of different samples were ruled out, benefit from the long decay time of PLNPs and time-resolved fluorescence technology. The detection results show high accuracy of the measured values of carcinoembryonic antigen both in cancer and benign disease group with low detection limit up to 0.0851 pg mL-1. Furthermore, excellent selectivity from coexisting biomarker was achieved by the hybridization between the aptamer and the complementary DNA on PLNPs surface. Hence, the established near-infrared PLNPs-based aptasensors offer excellent performance with high selective, accuracy and signal-to-noise ratio for detection of carcinoembryonic antigen in pleural effusion.

Determination of prostate cancer marker Zn2+ with a highly selective surface-enhanced Raman scattering probe on liquid-liquid self-assembled Au nanoarrays.

As the concentration of Zn2+ in patients with prostate cancer is much less than that in healthy persons, Zn2+ concentration can be used as a marker to expediently screen prostate cancer. In this study, a sensitive and highly selective surface-enhanced Raman scattering (SERS) method to detect Zn2+ concentration in human prostatic fluids by utilizing water-insoluble 2-carboxyl-2'-hydroxyl-5'-sulfoformazylbenze (Zincon) as a SERS probe based on self-assembled Au nanoarrays at a liquid-liquid interface between n-hexane and Au colloids was proposed. Zincon showed remarkably different SERS bands before and after coordinating Zn2+ in the controlled conditions (70 µL of ethanol, 500 µL of n-hexane, pH value of 7.1 and 10 s of vortex mixing time), which can be used in quantifying Zn2+ with characteristic peaks. The proposed SERS method presented a good linear relationship ranging from 0.5 to 10 µmol/L and a satisfactory detection limit of 0.1 µmol/L as well as low interference with other metal ions. Moreover, the detection results are close to those of the conventional standard atomic absorption spectroscopy (AAS) method.

Gold nanoclusters-poly(9,9-dioctylfluorenyl-2,7-diyl) dots@zeolitic imidazolate framework-8 (ZIF-8) nanohybrid based probe for ratiometric analysis of dopamine.

Ratiometric analysis of dopamine (DA) in complex biological system is urgently desired. In this work, a novel dual-emission fluorescence probe was fabricated by embedding both gold nanoclusters (AuNCs) and poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) dots into zeolitic imidazolate framework-8 (ZIF-8) (abbreviated as ZIF-8@AuNCs-PFO) and applied to ratiometric analysis of DA. Remarkably, encapsulating AuNCs and PFO dots into ZIF-8 not only achieved an excellent aggregation induced emission (AIE) enhancement effect on AuNCs (5 times increase), but also brought about an unique DA-triggered asynchronous fluorescence changes of AuNCs and PFO dots. The as-prepared probe exhibited excellent performance toward DA in the concentrations range from 0.01 to 10000 µmol L-1 and good selectivity over interfering substances. The detection limit of DA was as low as 4.8 nmol L-1. Furthermore, good stability and practicability of the probe in human serum samples suggesting its great potential for diagnostic purposes. Moreover, the quenching mechanism of AuNCs was intensively studied and summarized as three synergistic processes: (i) electron transfer between AuNCs and DA; (ii) DA-triggered architecture change of ZIF-8; (iii) fluorescence resonance energy transfer (FRET) between AuNCs and polydopamine (PDA), which offered an important theory for ZIF-based fluorescent probes.

Dual-colored carbon dots-based ratiometric fluorescent sensor for high-precision detection of alkaline phosphatase activity.

Probing the level and activity of alkaline phosphatases (ALP) is of great significance for biomedical research on cellular functions and clinical diagnosis of cancers. Herein, a novel dual-colored carbon dots (CDs)-based ratiometric fluorescent sensor was constructed to accomplish high sensitive and accurate determination of ALP relyed on the difference of fluorescence resonance energy transfer (FRET) between blue light emitted CDs (B-CDs)-MnO2 nanohybrid and yellow light emitted CDs (Y-CDs)-MnO2 nanohybrid. The ratiometric fluorescent sensor enabled sensitive discrimination of ALP against other enzymes in a linear range of 0.1-500 U/L with a limit of detection of 0.02 U/L. The lower error and signal fluctuation, more satisfactory LODs and higher R value (R2 = 0.99552) of the ratiometric sensing platform than single signal detection mode (R2 = 0.85231; R2 = 0.64260) indicated the superiority of the ratiometric fluorescence detection mode.Besides, the excellent analytical performance towards ALP in biological system demonstrated the potential application in clinical diagnosis.

Near-infrared carbon dots-based fluorescence turn on aptasensor for determination of carcinoembryonic antigen in pleural effusion.

Early detection of carcinoembryonic antigen (CEA) is of great significance for the screening, diagnosis, monitoring and prognosis analysis of lung cancer. Herein, a novel fluorescence aptasensor with high signal-noise ratio (SNR) was constructed to achieve highly-sensitive detection of CEA relied upon the fluorescence resonance energy transfer (FRET) between near-infrared carbon dots (NIR-CDs) and gold nanorods (AuNRs). Initially, AuNRs@SiO2-Aptamer and NIR-CDs-DNA probe were prepared via the covalent bonding reaction between their corresponding carboxyl and amino groups, respectively. After DNA hybridization, the aptasensor was formed, meanwhile, the fluorescence of NIR-CDs was quenched by AuNRs@SiO2. Once CEA encountered the aptasensor, it would selectively combine with CEA aptamer to unwind the preformed DNA double-strand architecture thereby resulting in the NIR-CDs-DNA detach from the surface of AuNRs@SiO2. The attendant fluorescence recovery of NIR-CDs was linearly correlated with the concentration of CEA. According to this relationship, the NIR-CDs based "turn on" sensing system was constructed and exhibited prominent responses toward CEA in the concentration range of 0.1-5000 pg/mL and a relatively low detection limit (0.02 pg/mL). Moreover, it displayed high specificity against other biomarkers or proteins, good reproducibility and acceptable accuracy regarding human pleural effusion samples.

Visual Assay of Glutathione in Vegetables and Fruits Using Quantum Dot Ratiometric Hybrid Probes.

Future food safety monitoring with simple, fast, and visual methods has become increasingly important. Accordingly, this work was designed to construct a new-style dual-emission ratiometric fluorescent probe (CdSe@SiO2@CdTe) for visual assay of glutathione (GSH) with a "turn on" strategy. After adding Hg2+, the red fluorescence of the outer CdTe quantum dots (QDs) was quenched through both electron transfer and ion-binding processes. Upon the addition of GSH, the red fluorescence occurred again owing to the strong affinity between GSH and Hg2+, whereas the inner green fluorescence of CdSe QDs was unchanged, leading to a clearly recognizable fluorescence color change (from green to orange-red). In the concentration range from 0.1 to 10 µM, the relative fluorescence intensity ratios ( I619/ I535) showed an excellent linear correlation with the concentration of GSH, and the detection limit was as low as 42 nM under optimal conditions. Meanwhile, the ratiometric hybrid probes were successfully applied for direct visual sensing GSH in real vegetable and fruit samples.

Ratiometric ultrasensitive fluorometric detection of ascorbic acid using a dually emitting CdSe@SiO2@CdTe quantum dot hybrid.

A dually emitting quantum dot nanohybrid was designed for the fluorometric 2-wavelength determination of ascorbic acid (AA). The nanohybrid consists of red-emitting CdTe quantum dots (QDs) covalently linked to the surface of silica nanoparticles containing green-emitting CdSe QDs. The fluorescence of the red-emitting CdTe QDs (peaking at 616 nm) is first quenched by addition of KMnO4 due to oxidation under formation of CdTeO3 and TeO2. On addition of AA, the red fluorescence is restored due to the reduction of surface CdTeO3/TeO2 to form CdTe. The green fluorescence of the green-emitting CdSe QDs (peaking at 522 nm), in contrast, remains constant and its intensity serves as a reference signal. Both kinds of QDs can be photoexcited at 380 nm. An easily distinguishable transition in fluorescence (from green to orange-red) can be observed on increasing the amount of added AA. Under optimal conditions, the ratio of the intensities of the red and the green fluorescence increases linearly in the 0.1 to 5.0 µM AA concentration range, and the detection limit is as low as 35 nM. The assay was successfully applied to the quantitation of AA in (spiked) fruit juice samples. Graphical abstract A new dually emitting CdSe@SiO2@CdTe nanohybrid was designed for ratiometric ultrasensitive fluorometric detection of ascorbic acid in fruit juice samples.

Dual-Metal Centered Zirconium-Organic Framework: A Metal-Affinity Probe for Highly Specific Interaction with Phosphopeptides.

The highly specific affinity between probes and phosphopeptides is the fundamental interaction for selective identification of phosphoproteomes that uncover the mechanisms of signal transduction, cell cycle, enzymatic regulation, and gene expression in biological systems. In this study, a metal-affinity probe possessing both interactions of metal oxide affinity chromatography (MOAC) and immobilized metal ion affinity chromatography (IMAC) was facilely prepared by immobilizing zirconium(IV) on a zirconium-organic framework of UiO-66-NH2, which holds dual-metal centers of not only the inherent Zr-O cluster but also the immobilized Zr(IV) center. This dual-metal centered zirconium-organic framework (DZMOF) demonstrates as a highly specific metal-affinity probe toward the extraction of phosphopeptides due to the metal-affinity interactions of MOAC and IMAC toward either mono-phosphorylated or multi-phosphorylated peptides. The binding energies of zirconium 3d5/2 and 3d3/2 in this DZMOF are 183.07 and 185.47 eV, respectively, which are higher than those of the intact UiO-66-NH2 (182.84 and 185.17 eV, respectively), confirming the higher metal-affinity interaction between the DZMOF and phosphopeptides. This high metal-affinity probe presents an unprecedented strong performance in anti-nonspecific interference during the capturing of phosphopeptides of ß-casein with the molar ratio of ß-casein vs bovine serum albumin up to ca. 1:5000. The enrichment of phosphopeptides from a human saliva sample by DZMOF further confirms the great potential of DZMOF in the extraction of low-abundance phosphopeptides for real complex biological samples.

Analysis of volatile organic compounds in compost samples: A potential tool to determine appropriate composting time.

Changes in volatile organic compound contents in compost samples during pig manure composting were studied using a headspace, solid-phase micro-extraction method (HS-SPME) followed by gas chromatography with mass spectrometric detection (GC/MS). Parameters affecting the SPME procedure were optimized as follows: the coating was carbon molecular sieve/polydimethylsiloxane (CAR/PDMS) fiber, the temperature was 60°C and the time was 30min. Under these conditions, 87 compounds were identified from 17 composting samples. Most of the volatile components could only be detected before day 22. However, benzenes, alkanes and alkenes increased and eventually stabilized after day 22. Phenol and acid substances, which are important factors for compost quality, were almost undetectable on day 39 in natural compost (NC) samples and on day 13 in maggot-treated compost (MC) samples. Our results indicate that the approach can be effectively used to determine the composting times by analysis of volatile substances in compost samples. An appropriate composting time not only ensures the quality of compost and reduces the loss of composting material but also reduces the generation of hazardous substances. The appropriate composting times for MC and NC were approximately 22days and 40days, respectively, during the summer in Zhejiang.

[Study on Hydrothermal Preparation and Luminescence Properties of Luminescent Material BaSrMg(PO4)2:Eu³âº].

Eu³âº doped BaSrMg (PO4)2 were prepared by a hydrothermal method. The crystal structure and morphology of BaSrMg(PO4)2:Eu³âº phosphor were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). The effects of different pH values (5, 6, 7 and 8) and different reaction temperatures (120, 140, 160, 180 and 200 °C) on the crystal structure and morphology of BaSrMg(PO4)2:Eu³âº phosphor were studied in this paper. The results of XRD indicate that diffraction peaks are sharp and strong only when pH value is 6, meanwhile the FESEM shows the morphology is regular-shaped. The XRD patterns show amorphous halos superimposed with several weak sharp peaks for the samples preparing under the pH values of 5, 7 and 8. It indicates that these three samples are solid solution or mixed phases, which are in accord with the results of FESEM. From the fluorescence spectra, the peaks in the excitation spectra were assigned to the transition from 7F0 to 5D4, 5L8, 5L6 and 5D2, while the peaks of emission spectra corresponding to the transition of 5D1 --> 7F1 and 5D0-->7Fj (J = 0, 1, 2, 3 and 4). The strongest emission peak of the optimized phosphor located at 613 nm (5D0--> 7F2), excited by the main excitation peak with wavelength of 394 nm. The splitting of the emission peaks changes depends on pH values and temperatures, which indicating that luminescence properties is closely related to the crystal structure and morphology of particles.

Analysis of volatile organic compounds in pleural effusions by headspace solid-phase microextraction coupled with cryotrap gas chromatography and mass spectrometry.

Headspace solid-phase microextraction coupled with cryotrap gas chromatography and mass spectrometry was applied to the analysis of volatile organic compounds in pleural effusions. The highly volatile organic compounds were separated successfully with high sensitivity by the employment of a cryotrap device, with the construction of a cold column head by freezing a segment of metal capillary with liquid nitrogen. A total of 76 volatile organic compounds were identified in 50 pleural effusion samples (20 malignant effusions and 30 benign effusions). Among them, 34 more volatile organic compounds were detected with the retention time less than 8 min, by comparing with the normal headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry method. Furthermore, 24 volatile organic compounds with high occurrence frequency in pleural effusion samples, 18 of which with the retention time less than 8 min, were selected for the comparative analysis. The results of average peak area comparison and box-plot analysis showed that except for cyclohexanone, 2-ethyl-1-hexanol, and tetramethylbenzene, which have been reported as potential cancer biomarkers, cyclohexanol, dichloromethane, ethyl acetate, n-heptane, ethylbenzene, and xylene also had differential expression between malignant and benign effusions. Therefore, the proposed approach was valuable for the comprehensive characterization of volatile organic compounds in pleural effusions.

Plasma Lipidomics Investigation of Hemodialysis Effects by Using Liquid Chromatography-Mass Spectrometry.

Chronic kidney disease (CKD) has been a global health problem that has a great possibility of being developed into uremia in the end. Hemodialysis (HD) is the most commonly used strategy for treating uremic patients; however, the patients still have a high risk of suffering various complications. It is well recognized that lipid disorder usually occurs in maintenance HD patients. To systemically study the effects of HD on lipid metabolism associated with uremia, we employed an ultraperformance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS)-based lipidomics method. A total of 87 human plasma samples from patients with prehemodialysis (pre-HD)/posthemodialysis (post-HD) treatment and the healthy controls were enrolled in the study. As compared with pre-HD patients, many plasma lipids showed significant changes (p < 0.05) in patients receiving HD therapy. Specifically, sum of free fatty acids (FFA) as well as saturated FFA and eicosanoids and sums of lyso-phosphatidylinositols and lyso-phosphatidylethanolamines, FFA 16:1/FFA 16:0, and FFA 18:1/FFA 18:0 were obviously higher in the pre-HD group than in the controls while they were significantly lower in patients after HD. These results indicated that UPLC-Q-TOF/MS-based lipidomics is a promising approach to investigate lipid alterations in relation to uremia and it is helpful to understand complex complications involved in HD patients.

[Simultaneous determination of five active components of compound α-ketoacid tablet in human urine by ion-pair reversed-phase high performance liquid chromatography].

A simple and sensitive method for the simultaneous determination of five active components, D, L-α-hydroxymethionine calcium (HMACa), α-ketovaline calcium (KVCa), D, L-α-ketoisoleucine calcium (KILCa), α-ketoleucine calcium (KLCa) and α-ketophenylalanine calcium (KPACa) of compound α-ketoacid tablet in human urine by ion-pair reversed-phase high performance liquid chromatography (RP-HPLC) was developed and validated. The separation conditions, such as the concentration of ion-pair reagent, the pH value of the mobile phase and the concentration of the buffer were optimized. All the five analytes were separated well on a C18 column (250 mm x 4.6 mm, 5 µm) with diode array detection at 210 nm and the column temperature of 35 °C. The mobile phases were acetonitrile and 20 mmol/L phosphate buffer (containing 15 mmol/L tetrabutylammonium hydroxide; pH 7) at the flow rate of 1. 0 mL/min with gradient elution. The calibration curves for the five components were linear in the range from 20 to 200 mg/L (r≥ 0. 9990). The limits of detection (LODs, S/N= 3) were 3.0, 5. 0, 3. 6, 5.7 and 2. 5 mg/L, and the limits of quantification (LOQs, S/N= 10) were 9. 6, 16.7, 12.0, 19.0 and 8.3 mg/L for HMACa, KVCa, KILCa, KLCa and KPACa, respectively. The intra-day and inter-day precisions were less than 7%, and the average recoveries were between 86.79% and 112. 00% in the human urine with RSDs lower than 9% (n= 5). The method proved precise, specific and reproducible, and can be used for the determination of the five components in urine.

Analysis of trace inorganic anions in weak acid salts by single pump cycling-column-switching ion chromatography.

The application of ion chromatography with the single pump cycling-column-switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion-exclusion column were adopted to achieve on-line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 µg/L, based on the signal-to-noise ratio of 3 and a 25 µL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts.

Three-phase hollow-fiber microextraction combined with ion-pair high-performance liquid chromatography for the simultaneous determination of five components of compound α-ketoacid tablets in human urine.

The determination of α-ketoacid concentration is demanded to evaluate the absorption and metabolic behavior of compound α-ketoacid tablets taken by chronic kidney disease patients. To eliminate the interference of endogenous substance of urine and enrich the analytes, a three-phase hollow-fiber liquid-phase microextraction combined with ion-pair high-performance liquid chromatography method was established for the determination of d,l-α-hydroxymethionine calcium, d,l-α-ketoisoleucine calcium, α-ketovaline calcium, α-ketoleucine calcium, and α-ketophenylalanine calcium of compound α-ketoacid tablets in human urine samples. The extraction parameters, such as organic solvent, pH of donor phase and acceptor phase, stirring rate, and extraction time were optimized. Under the optimal conditions, the obtained enrichment factors were up to 11-, 110-, 198-, 202-, and 50-fold, respectively. The calibration curves for these analytes were linear over the range of 0.1-10 mg/L for α-ketovaline calcium, d,l-α-ketoisoleucine calcium, and α-ketoleucine calcium, 0.5-10 mg/L for d,l-α-hydroxymethionine calcium, and α-ketophenylalanine calcium with r > 0.99. The relative standard deviations (n = 5) were less than 6.27% and the LODs were 100.7, 10.0, 5.8, 7.8, and 8.6 µg/L (based on S/N = 3), respectively. Good recoveries from spiked urine samples (92-118%) were obtained. The proposed method demonstrated excellent sample clean-up and analytes enrichment to determine the five components in human urine.

Investigation of volatile organic metabolites in lung cancer pleural effusions by solid-phase microextraction and gas chromatography/mass spectrometry.

Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography/mass spectrometry (GC/MS) method was applied for the investigation of low molecular weight volatile organic metabolites (VOMs) in pleural effusion samples. Three important HS-SPME experimental parameters that influence extraction efficiency (fiber coating, extraction time and temperature of sampling) were optimized by a univariate optimization design. The highest extraction efficiency was obtained when sampling was performed at 50°C for 10min under agitation using a carboxen/polydimethylsiloxane (CAR/PDMS) fiber. A total of 36 volatile metabolites belonging to nine distinct chemical classes were identified in 40 pleural effusion samples (20 malignant effusions from lung cancer patients and 20 benign effusions from inflammatory patients). Ketones, alcohols, and benzene derivatives were the main chemical classes for the metabolomic profile of malignant effusions. The average peak areas of ketones and alcohols were much higher in malignant group compared to benign group. Together with phenols, they exhibit significant differences (P<0.05) between the two groups. Particularly, the average peak areas of cyclohexanone and 2-ethyl-1-hexanol in malignant effusions were significantly higher than those in benign ones. Furthermore, of the 36 identified metabolites, 5 compounds including cyclohexanone and 2-ethyl-1-hexanol were found to be statistically different (Student's t-test, P<0.05) between the two groups by statistical analysis based on the peak areas of all identified metabolites. Among them, cyclohexanone and 2-ethyl-1-hexanol might be considered as candidate biomarkers of lung cancer to differentiate malignant from benign effusions. The results show that HS-SPME-GC/MS is a simple, rapid, sensitive and solvent-free method for the determination of VOMs in pleural effusion samples. Pleural effusion is a valuable sample source for observation of changes in VOMs for differentiation between lung cancer patients and inflammatory individuals.