[Progress in preparation of hollow nanomaterials and their application to sample pretreatment].

Sample pretreatment technology plays a vital role in the analysis of complex samples and is key to the entire analytical process. Its main purpose is to separate the substance to be measured from the sample matrix or interfering substances in the sample and to achieve a state in which the instrument can be analyzed and detected. Traditional sample pretreatment techniques include liquid-liquid extraction, liquid-solid extraction, precipitation separation, solvent volatilization-rotary evaporation, filtration, and centrifugation. However, the applications of these methods are limited by their low extraction efficiency, complicated operation, long time consumption, unstable recovery, use of large amounts of organic solvents, and large error rates. Several new sample pretreatment techniques, including solid-phase extraction, magnetic solid-phase extraction, solid-phase microextraction, and dispersive solid-phase extraction, have been developed and rapidly applied to various fields to overcome the shortcomings of traditional sample pretreatment methods. However, the development of adsorbent materials with high selectivity and enrichment capability remains a challenge in sample pretreatment technology, in which adsorbents with excellent adsorption performance are crucial. In recent years, various nanomaterials with remarkable properties have been introduced and applied to sample pretreatment, and numerous nano-extraction materials with diverse functions and high selectivity and enrichment capability have been developed. Hollow nanomaterials are nanoparticles with large voids in their solid shells. Owing to their advantageous properties, which include a large effective surface area, abundant internal space, low density, variety of preparation methods, structural and functional tailorability, short mass transmission path, and high carrying capacity, hollow nanomaterials show great application potential in sample pretreatment. The extraction mechanism of these materials is based on the synergistic effects of π-π stacking, electrostatic, hydrogen-bonding, and hydrophobic interactions to achieve the efficient separation and enrichment of the target analytes. Given their noteworthy physicochemical properties, hollow nanomaterials have gained wide attention in various research fields and are considered a research frontier in the field of materials science. Changing the structure or surface properties of the core and shell can lead to various hollow nanomaterials with unique properties. Such changes can create synergy between the physicochemical properties and structural function of the original core-shell material, leading to novel materials with superior performance compared with the starting materials and broad application prospects in sample pretreatment. Nevertheless, only a few hollow nanomaterials with diverse structures and functions are currently used for sample pretreatment, and their adsorption capacity for target analytes is often unsatisfactory. Consequently, enhancing the adsorption selectivity of these materials toward various analytes is the most important step in sample pretreatment. First, hollow nanomaterials with a large specific surface area and suitable pore size can be designed to achieve the specific adsorption of target analytes of varying sizes. The combination of hollow nanomaterials with other materials presenting desirable adsorption properties could also lead to synergistic effects and enhance the performance of composite hollow nanomaterials. In addition, more green methods to prepare hollow nanomaterials with outstanding selectivity can be explored to achieve the superior adsorption of a specific target analyte. Efforts to synthesize hollow nanomaterials have been met with great success, but the available synthesis methods still suffer from complicated steps, high costs, relatively harsh conditions, and the use of highly toxic substances. This paper summarizes the main types of hollow nanomaterials, their synthesis methods, and research progress on sample pretreatment technologies (solid-phase extraction, solid-phase microextraction, magnetic solid-phase extraction, and dispersive solid-phase extraction) and describes the challenges encountered in the synthesis of hollow nanomaterials. The applications and developments of hollow nanomaterials in sample pretreatment are also discussed.

Rapid and Selective 19F NMR-Based Sensors for Fingerprint Identification of Ribose.

Ribose plays an important role in the process of life. Excessive ribose in the human cerebrospinal fluid or urine can be used as an early diagnostic marker of leukoencephalopathy. Fluorinated phenylboronic acid combined with 19F NMR spectroscopy was a powerful method for molecular recognition. However, phenylboronic acid-based sensors for selective detection of ribose are rarely reported in the literature. In this study, the rapid and highly selective recognition of ribose was studied by 19F NMR and 2-fluorophenylboric acid. It was found that 2-fluoro-phenylboric acid was an appropriate 19F NMR-based sensor molecule for the determination of ribose under physiological conditions with high selectivity and robust anti-interference ability. When 2-fluorophenylboric acid was used for the detection of ribose in human urine without any sample pretreatment, a limit of detection of 78 µM was obtained at room temperature under given 19F NMR experimental conditions (400 MHz, 512 scans, ca. 12 min), which can well meet the needs of practical application.

A Bisboronic Acid Sensor for Ultra-High Selective Glucose Assay by 19F NMR Spectroscopy.

Glucose is a significant analyte both in biology and biomedical science, it is of great importance to selectively detect glucose both in body fluids and complex mixture. In this study, a simple 19F NMR based sensor was synthesized easily, which exhibited a high selectivity and robust anti-interference ability toward glucose detection both in a mixture containing up to 10 saccharides and human urine samples without any pretreatment. Combined with this sensor system, glucose could be well detected in human urine samples and the limit of detection was 0.41 mM by using a 400 MHz NMR spectrometer with 128 scans (ca. 4 min). This method had a potential for specific detection of glucose in complex mixture and diagnosis of diabetes mellitus related diseases in body fluid.

Determination of polycyclic aromatic hydrocarbons in water by a novel mesoporous-coated stainless steel wire microextraction combined with HPLC.

A novel mesoporous-coated stainless steel wire microextraction coupled with the HPLC procedure for quantification of four polycyclic aromatic hydrocarbons in water has been developed, based on the sorption of target analytes on a selectively adsorptive fiber and subsequent desorption of analytes directly into HPLC. Phenyl-functionalized mesoporous materials (Ph-SBA-15) were synthesized and coated on the surfaces of a stainless steel wire. Due to the high porosity and large surface area of the Ph-SBA-15, high extraction efficiency is expected. The influence of various parameters on polycyclic aromatic hydrocarbons extraction efficiency were thoroughly studied and optimized (such as the extraction temperature, the extraction time, the desorption time, the stirring rate and the ionic strength of samples). The results showed that each compound for the analysis of real water samples was tested under optimal conditions with the linearity ranging from 1.02×10(-3) to 200 µg/ L and the detection limits were found from 0.32 to 2.44 ng/ L, respectively. The RSD of the new method was smaller than 4.10%.

[Studies on chemical constituents in herb of Myricaria bracteata].

OBJECTIVE: To study the chemical constituents of Myricaria bracteata. METHOD: The chemical constituents were isolated by silica gel column chromatography and the structures were elucidated by spectroscopic methods. RESULT: Eleven compounds were obtained and identified as rhamnetin, 3,5,4'-trihydroxy-7,3'-dimethoxyflavone, 3,5,4'-trihydroxy-7-methoxyflavone, quercetin-3-O-alpha-L-rhamnopyranoside, kaempferol, quercetin, chrysoerio, gallic acid, gallic acid ethylester, beta-sitosterol, daucosterol. CONCLUSION: All compounds were obtained from M. bracteata for the first time.

Inorganic/organic mesoporous silica as a novel fiber coating of solid-phase microextraction.

Mesoporous materials were employed as fast, sensitive and efficient fiber coatings of solid-phase microextraction (SPME) for the first time. Three micrometer as-synthesized C(16)-MCM-41 particles were immobilized onto stainless steel wire with 100mum coating thickness. In combination with high performance liquid chromatography (HPLC), extraction efficiency and selectivity of C(16)-MCM-41 were investigated using aromatic hydrocarbons. Effect of extraction and desorption time, extraction temperature, stirring rate and ionic strength on extraction efficiency were examined. Aanalytical merits of SPME with C(16)-MCM-41 coating were evaluated. The chromatographic peak area is proportional to the concentration of anthracene in the range 0.5-150mugl(-1). The limit of detection was 0.05mugl(-1) (S/N=3) and the relative standard deviation (R.S.D.) was 0.033%.

[Comparative study of room-temperature phosphorescence of 1-bromonaphthalene induced by synergetic effect of nonionic surfactants and beta-cyclodextrin].

Room-temperature phosphorescence of 1-BrN induced by a combination of OPE-10 and Triton X-100 with beta-CD was comparatively studied. In terms of molecular size and dimensions of beta-CD, the octyl group and phenyl group of OPE-10 and Triton X-100 were incorporated into the cavity of beta-CD and the complexes with the stoichiometry of 1:1 were formed. The removal of water molecules inside the cavity results in a greater apolar interior. By enhanced hydrophobic interaction, the cavity occupied by OPE-10 and Triton X-100 is able to further capture another 1-BrN and form close packing 1:1:1 ternary inclusion complexes with apparent stability constant of 1.09 x 10(5) and 4.47 x 10(5) L2 x mol(-2), respectively. 1-BrN shows bright phosphorescence at room temperature due to the greater rigidity in the limited space and the favorable microenvironment shielding from external quenchers and quenching effect on the fluorescence of the phenyl group of OPE-10 and Triton X-100 within the same cavity. In the case of Triton X-100, the larger tert-octyl group better shields off external quenchers such as dissolved oxygen and iodide ion. Energy transfer from the excited phenyl group of Triton X-100 to adjacent 1-BrN acceptor was observed.

[Study of the acupuncture effect on monoamine transmitters in rabbit plasma and brain tissue by high performance liquid chromatography with electrochemical detection].

A rapid and simple method for the study of the acupuncture effect on monoamine transmitters and related compounds in rabbit plasma and brain tissue by high performance liquid chromatography with electrochemical detection was developed. An ODS column was selected as the separation column at 25 degrees C, and pH 4.50, 0.02 mol/L of trisodium citrate-0.05 mol/L sodium phosphate dibasic to methanol (95:5, volume ratio) without ion-pair at a flow rate of 1.0 mL/min. Four compounds, epinephrine (E), norepinephrine (NE), dopamine (DA) and 5-hydroxytryptamine (5-HT), were simultaneously separated and determined under the above conditions. Twenty rabbits were investigated after the acupuncture action upon the central neurotransmitters. The sufficient data showed that acupuncture could significantly affect the activities of the neurotransmitters including E, NE, DA and 5-HT, and the changed functions of the neurotransmitter systems induced by acupuncture not only lead to the neurotransmitter content increase both in brain and plasma but also cause the increase of rabbit breed ability. The results show that the method is very simple and fast. The method is valuable not only for clinical diagnosis but also for research work.