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1.
Nature ; 560(7720): 582-588, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30158607

RESUMO

The Newtonian gravitational constant, G, is one of the most fundamental constants of nature, but we still do not have an accurate value for it. Despite two centuries of experimental effort, the value of G remains the least precisely known of the fundamental constants. A discrepancy of up to 0.05 per cent in recent determinations of G suggests that there may be undiscovered systematic errors in the various existing methods. One way to resolve this issue is to measure G using a number of methods that are unlikely to involve the same systematic effects. Here we report two independent determinations of G using torsion pendulum experiments with the time-of-swing method and the angular-acceleration-feedback method. We obtain G values of 6.674184 × 10-11 and 6.674484 × 10-11 cubic metres per kilogram per second squared, with relative standard uncertainties of 11.64 and 11.61 parts per million, respectively. These values have the smallest uncertainties reported until now, and both agree with the latest recommended value within two standard deviations.

2.
Sensors (Basel) ; 22(21)2022 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-36365801

RESUMO

The bias stability performance of accelerometers is essential for an inertial navigation system. The traditional pendulous accelerometer usually has a flexible connection structure, which could limit the long-term bias stability. Here, based on the main technologies employed in previous space missions of our group, we developed a terrestrial triaxial navigation-compatible accelerometer. Because there is no mechanical connection between the inertial test mass and the frame, the bias performance relies on the stability of the equivalent electrostatic spring, where further sources are analyzed to get the optimal electrostatic force scheme. To investigate the bias stability under different ranges, the vertical and horizontal measurement ranges are designed at 5 g and ±10 mg, respectively. A low-noise high-voltage levitation scheme is adopted to extend the vertical measurement range from sub-mg to more than earth's 1-g gravity. Finally, the experimental validation results show that the 24-h bias stability of vertical and two horizontal directions come to 13.8 µg, 0.84 µg, and 0.77 µg, respectively.

3.
Sensors (Basel) ; 20(11)2020 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-32517190

RESUMO

Ultra-sensitive inertial sensors are one of the key components in satellite Earth's gravity field recovery missions and space gravitational wave detection missions. Low-noise capacitive position transducers are crucial to these missions to achieve the scientific goal. However, in actual engineering applications, the sensor head and electronics unit usually place separately in the satellite platform where a connecting cable is needed. In this paper, we focus on the stray-capacitance influences of coaxial cables which are used to connect the mechanical core and the electronics. Specially, for the capacitive transducer with a differential transformer bridge structure usually used in high-precision space inertial sensors, a connecting method of a coaxial cable between the transformer's secondary winding and front-end circuit's preamplifier is proposed to transmit the AC modulated analog voltage signal. The measurement and noise models including the stray-capacitance of the coaxial cable under this configuration is analyzed. A prototype system is set up to investigate the influences of the cables experimentally. Three different types and lengths of coaxial cables are chosen in our experiments to compare their performances. The analysis shows that the stray-capacitance will alter the circuit's resonant frequency which could be adjusted by additional tuning capacitance, then under the optimal resonant condition, the output voltage noises of the preamplifier are measured and the sensitivity coefficients are also calibrated. Meanwhile, the stray-capacitance of the cables is estimated. Finally, the experimental results show that the noise level of this circuit with the selected cables could all achieve 1-2 × 10-7 pF/Hz1/2 at 0.1 Hz.

4.
Sensors (Basel) ; 17(9)2017 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-28832538

RESUMO

High-precision electrostatic accelerometers have achieved remarkable success in satellite Earth gravity field recovery missions. Ultralow-noise inertial sensors play important roles in space gravitational wave detection missions such as the Laser Interferometer Space Antenna (LISA) mission, and key technologies have been verified in the LISA Pathfinder mission. Meanwhile, at Huazhong University of Science and Technology (HUST, China), a space accelerometer and inertial sensor based on capacitive sensors and the electrostatic control technique have also been studied and developed independently for more than 16 years. In this paper, we review the operational principle, application, and requirements of the electrostatic accelerometer and inertial sensor in different space missions. The development and progress of a space electrostatic accelerometer at HUST, including ground investigation and space verification are presented.

5.
J Sep Sci ; 39(15): 2970-7, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27288092

RESUMO

In this work, poly(glycidylmethacrylate-divinylbenzene) microspheres were prepared and applied for the preparation of weak acid cation exchange stationary phases. Succinic anhydride, phthalic anhydride, and maleic anhydride were selected as carboxylation reagents to prepare three weak acid cation exchangers by direct chemical derivatization reaction without solvent or catalyst. The diameters and dispersity of the microspheres were characterized by scanning electron microscopy; the amount of accessible epoxy groups and mechanical stability were also measured. The weak acid cation exchangers were characterized by Fourier transform infrared spectroscopy; the content of carboxyl groups was measured by traditional acid base titration method. The chromatographic properties were characterized and compared by separating alkali, alkaline earth metal ions and ammonium and polar amines. The separation properties enhanced in the order of succinic anhydride, phthalic anhydride, and maleic anhydride modified poly(glycidylmethacrylate-divinylbenzene) cation exchangers.

6.
Zhonghua Wai Ke Za Zhi ; 52(4): 271-5, 2014 Apr.
Artigo em Zh | MEDLINE | ID: mdl-24924572

RESUMO

OBJECTIVE: To investigate the microsurgical tchniques and effects for the resection of anterior clinoid meningioma (ACM). METHODS: Between January 2003 and March 2013, a total of 46 ACM patients were operated on via the pterion approach or lateral subfrontal approach. There were 16 male patients and 30 female patients, their mean age was 48.5 (16-69) years. Symptoms lasted from 1 month to 9 years(average 24.7 months). Preoperative CT and MRI examination showed that the tumors were located in the anterior clinoid process (25 cases on the right side, 21 cases on the left side). The average maximal tumor diameter was 4.4 cm (1.9-7.4 cm). The patients were peroidly followed-up on outpatient on 3 months to 6 months, then every year postoperativelly. The clinical data, radiological findings, surgical records and outcome of patients were retrospectively analyzed, and the prognostic factors were ananlyzed by using of the unpaired data χ(2) test with continuity correction. RESULTS: Of fourty-six patients operated on, apparently complete removal was achieved in 36 patients (78.3%), 10 patients (21.7%) had minimal residual tumors, 5 of which had gamma knife radiosurgery. Preexisting visual deficit improved in 21 of 41 patients (51.2%), unchanged in 16(35.6%), and worsened in 9(20.0%). At 3-6 months after discharge, 37(80.4%) patients had a good recovery, 7(15.6%) patients were moderately disabled, 1(2.2%) presented with severe disability, and 1 (2.2%) patient died of surgery-related causes. The tumor wrapping blood vessels (χ(2) = 4.676, P = 0.031) and violating cavernous sinus(χ(2) = 4.973, P = 0.026) were causes of unfavorable prognosis. During the mean follow-up of 35.1 months (range, 4-107 months) for 40 patients, the average Karnofsky score was 83.2. Tumor recurred in 4 cases: 2 of which required reoperation, and 2 had gamma knife radiosurgery. CONCLUSIONS: Tumor wrapped vessels and invasion of the cavernous sinus are important unfavorable prognostic factors for ACM resection. By using appropriate surgical strategies and techniques, ACM can be removed safely via the pterion approach or lateral subfrontal approach with relatively low morbidity and mortality.


Assuntos
Neoplasias Meníngeas/cirurgia , Meningioma/cirurgia , Microcirurgia , Procedimentos Neurocirúrgicos/métodos , Adolescente , Adulto , Idoso , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento , Adulto Jovem
7.
Food Chem ; 426: 136534, 2023 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-37302307

RESUMO

A highly sensitive and selective HPLC method for the determination of vitamin K vitamers including phylloquinone (PK) and menaquinones (MK-4) in infant formulas is described. The K vitamers were quantified with a fluorescence detector after online post-column electrochemical reduction occurring in a laboratory-made electrochemical reactor (ECR) equipped with platinum plated porous titanium (Pt/Ti) electrodes. The morphology of the electrode showed that the grain size of Pt was homogeneous and well plated on the porous Ti substrate, resulting in largely improved electrochemical reduction efficiency due to the large specific surface area. In addition, the operation parameters such as mobile phase/supporting electrolyte and working potential were optimized. The detection limits of PK and MK-4 were 0.81 and 0.78 ng g-1. Infant formula varying in stages were detected, showing PK ranged from 26.4 to 71.2 µg/100 g, while MK-4 was not detected.


Assuntos
Fórmulas Infantis , Vitamina K , Humanos , Lactente , Titânio , Porosidade , Vitamina K 1/análise , Cromatografia Líquida , Cromatografia Líquida de Alta Pressão/métodos , Eletrodos
8.
BMJ ; 383: e076065, 2023 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-37907210

RESUMO

OBJECTIVE: To assess the efficacy and safety of pyrotinib (an irreversible pan-HER (human epidermal growth factor receptor) inhibitor), trastuzumab, and docetaxel compared with placebo, trastuzumab, and docetaxel for untreated HER2 positive metastatic breast cancer. DESIGN: Randomised, double blind, placebo controlled, multicentre, phase 3 trial. SETTING: 40 centres in China between 6 May 2019 and 17 January 2022. PARTICIPANTS: 590 female patients (median age 52 (interquartile range 46-58) years) with untreated HER2 positive metastatic breast cancer. INTERVENTIONS: Eligible patients were randomised 1:1 to receive either oral pyrotinib (400 mg once daily) or placebo, both combined with intravenous trastuzumab (8 mg/kg in cycle 1 and 6 mg/kg in subsequent cycles) and docetaxel (75 mg/m2) on day 1 of each 21 day cycle. Randomisation was stratified by treatment history of trastuzumab in the (neo)adjuvant setting and hormone receptor status. Patients, investigators, and the sponsor's study team were masked to treatment assignment. MAIN OUTCOME MEASURES: The primary endpoint was progression-free survival as assessed by the investigator. RESULTS: Of the 590 randomised patients, 297 received pyrotinib, trastuzumab, and docetaxel treatment (pyrotinib group), and 293 received placebo, trastuzumab, and docetaxel treatment (placebo group). At data cut-off on 25 May 2022, the median follow-up was 15.5 months. The median progression-free survival according to the investigator was significantly longer in the pyrotinib group than in the placebo group (24.3 (95% confidence interval 19.1 to 33.0) months versus 10.4 (9.3 to 12.3) months; hazard ratio 0.41 (95% confidence interval 0.32 to 0.53); one sided P<0.001). Treatment related adverse events of grade 3 or higher were reported in 267 (90%) of the 297 patients in the pyrotinib group and 224 (76%) of the 293 patients in the placebo group. No treatment related deaths occurred in the pyrotinib group, and one (<1%; diabetic hyperosmolar coma) treatment related death occurred in the placebo group. Survival and toxicities are still under assessment with longer follow-up. CONCLUSIONS: Pyrotinib, trastuzumab, and docetaxel showed superiority by significantly improving progression-free survival compared with placebo, trastuzumab, and docetaxel in patients with untreated HER2 positive metastatic breast cancer. The toxicity was manageable. The findings support this dual anti-HER2 regimen as an alternative first line treatment option in this patient population. TRIAL REGISTRATION: ClinicalTrials.gov NCT03863223.


Assuntos
Neoplasias da Mama , Feminino , Humanos , Pessoa de Meia-Idade , Anticorpos Monoclonais Humanizados/efeitos adversos , Anticorpos Monoclonais Humanizados/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Docetaxel/efeitos adversos , Docetaxel/uso terapêutico , Método Duplo-Cego , Receptor ErbB-2/metabolismo , Trastuzumab/efeitos adversos , Trastuzumab/uso terapêutico , Resultado do Tratamento
9.
J Chromatogr A ; 1638: 461898, 2021 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-33486221

RESUMO

A 4-layer sandwiched device (4LSD) well suited for coupling to online ion chromatography (IC) systems was described and simultaneously performed target anion enrichment, matrix removal and sample injection within seconds. The basic assembly consisted of an extraction solution channel, a sample solution channel and two electrolyte channels. Cation-exchange resin (CER) was utilized to support the solution chamber, increase electrical conductivity and improve pressure resistance to achieve compatibility with a peristaltic pump. Filter placement ensured loop circulation of the 4LSD and prevented resin leakage. The 4LSD showed comparable performance to that of conventional solid-phase extraction (SPE) pretreatment in terms of matrix interference removal while enabling automation. The applied current, sample/extraction solution flow rate ratio, and initial concentration were discussed and optimized. Controllable 1-40-fold enrichment can be ensured. The migration phenomenon of different anions was discussed. F-, Cl-, NO2-, Br-, NO3-, SO42- and ClO4- exhibited satisfactory linear detection ranges within 2.5-1000 µg·L-1, and the calculated limits of detection (LODs) in milk formula were within the 0.097-0.79 mg·kg-1 range. The 4LSD was successfully applied to the determination of anions in milk formula with good spiked recoveries ranging between 92.54% and 107.2%, except for the NO2- recovery. The relative standard deviations (RSDs) ranged from 0.69% to 8.29%.


Assuntos
Cromatografia/métodos , Condutividade Elétrica , Eletroquímica/instrumentação , Eletroquímica/métodos , Animais , Ânions/análise , Automação , Resinas de Troca de Cátion , Limite de Detecção , Leite/química , Reprodutibilidade dos Testes , Extração em Fase Sólida
10.
Rev Sci Instrum ; 92(6): 064502, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34243500

RESUMO

A high precision electrostatic accelerometer has widely been employed to measure gravity gradients and detect gravitational waves in space. The high-voltage levitation method is one of the solutions for testing electrostatic accelerometers on the ground, which aims at simultaneously detecting all six-degree-of-freedom movements of the electrostatic accelerometers engineering and flight prototypes. However, the noise performance in the high-voltage levitation test is mainly limited by seismic noise. The combined test of the accelerometer and vibration isolation platform is adopted to improve the detection precision of the high-voltage levitation method. In this paper, a high precision electrostatic accelerometer prototype is developed after designed appropriate mechanical parameters with a test mass weighing 300 g and with an estimated resolution of 2 × 10-12 m/s2/Hz1/2 from 0.01 to 0.4 Hz. Such a prototype is tested by the high-voltage levitation method, its measurement noise on the ground is mainly limited by the seismic noise, which is about 5 × 10-7 m/s2/Hz1/2 around 0.2 Hz and about 4 × 10-8 m/s2/Hz1/2 around 0.1 Hz. A vibration isolation pendulum bench based on the translation-tilt compensation principle is adopted for accelerometer prototype combined tests to suppress the seismic noise, which has a large bench area and the ability to adjust the tilt angle precisely. The measured accelerometer noise of the combined test with the translation-tilt compensation pendulum has reached 3 × 10-9 m/s2/Hz1/2 around 0.2 Hz, and it is about two orders of magnitude lower than the measurement noise on the ground. The combined test method provides technical guidance for further improving the noise level of ground test in the future.

11.
R Soc Open Sci ; 5(8): 171948, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30224984

RESUMO

A novel method combining high-performance liquid chromatography with online post-column electrochemical derivatization and fluorescence detection was established for the detection of reserpine in mouse serum. Reserpine separation was conducted using a C18 column with 5 mM H3PO4 and acetonitrile (55/45, v/v) as eluent. Reserpine was then electro-oxidized into a strongly fluorescent compound using an electrolytic cell device. Detection parameters, such as potential and fluorescence wavelength, were optimized. The linearity of the proposed method ranged from 0.01 to 5.0 mg l-1 with a correlation coefficient of 0.9997. The limit of qualification (S/N = 10) and limit of detection (S/N = 3) were 9.7 and 2.9 µg l-1, respectively. Resperine recoveries from spiked blank and drug-treated mouse serum samples ranged from 92.0 to 115%.

12.
Food Chem ; 239: 62-67, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-28873613

RESUMO

Folic acid plays a significant role during periods of rapid cells division and growth. Pregnant women require folic acid daily, either from dietary supplements or folic acid tablets in order to prevent fetal neural tube defects. In this work, a simple coupled ultrahigh performance liquid chromatography and ion chromatography technique was developed for simultaneous determination of folic acid and inorganic anions in folic acid tablets. A reversed-phase C18 column was used as the pretreatment column for on-line separating inorganic anions from organics. Inorganic anions were concentrated in the concentration column. Under the optimal chromatographic conditions, good sensitivity and linear calibration-curves (r≥0.9992) were obtained. Low detection limits were obtained in the range of 0.0032-0.40mgL-1 for all analytes. Repeatability results were satisfactory with relative standard deviations less than 1.50% (n=5). The developed method was utilized to analyze spiked folic acid tablet samples with good measured recoveries (92.4-107.4%).


Assuntos
Ácido Fólico/química , Ânions , Cromatografia Líquida , Suplementos Nutricionais , Humanos , Reprodutibilidade dos Testes , Comprimidos
13.
Talanta ; 163: 24-30, 2017 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-27886766

RESUMO

Monodisperse carbonaceous spheres produced by the hydrothermal carbonization of sucrose were first applied as green stationary phase for ion chromatography after quaternization. Depending on the polycondensation of methylamine and 1,4-butanediol diglycidyl ether, polymer containing quaternary ammonium groups were facilely grafted onto the surfaces of hydrothermal carbonaceous spheres (HCSs). The quaternized HCSs with different number of polyelectrolyte layers were characterized by scanning electron microscopy, brunauer-emmett-teller, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and elemental analysis. The measurements of breakthrough curves demonstrated that more layers of grafted polyelectrolyte resulted in higher anion exchange capacity of stationary phase. With good stability, common inorganic anions, monocarboxylic acids, polarizable anions and carbohydrates were effectively separated on the stationary phases, respectively. The high hydrophilicity of HCS surface afforded excellent peak symmetry for all analytes. Furthermore, high-capacity HCSs stationary phase was successfully applied to detect fluoride in tea samples.


Assuntos
Carbono/química , Cromatografia por Troca Iônica/métodos , Temperatura , Butileno Glicóis/química , Metilaminas/química
14.
J Chromatogr A ; 1500: 145-152, 2017 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-28434713

RESUMO

An online membrane-based distillation (MBD) coupled with ion chromatography (IC) method was proposed for automatic detection of trace fluoride (F-) in serum and urine samples. The system consisted of a sample vessel, a lab-made membrane module and an ion chromatograph. Hydrophobic polytetrafluoroethylene (PTFE) hollow fiber membrane was used in MBD which was directly performed in serum and urine samples to eliminate the matrix interferences and enrich fluoride, while enabling automation. The determination of fluoride in biological samples was carried out by IC with suppressed conductometric detection. The proposed method feasibly determined trace fluoride in serum and urine matrices with the optimized parameters, such as acid concentration, distillation temperature, and distillation time, etc. Fluoride exhibited satisfactory linearity in the range of 0.01-5.0mg/L with a correlation coefficient of 0.9992. The limit of detection (LOD, S/N=3) and limit of quantification (LOQ, S/N=10) were 0.78µg/L and 2.61µg/L, respectively. The relative standard deviations of peak area and peak height were all less than 5.15%. The developed method was validated for the determination of fluoride in serum and urine with good spiked recoveries ranging between 97.1-101.9%. This method also can be proposed as a suitable alternative for the analysis of fluoride in other complex biological samples.


Assuntos
Cromatografia/métodos , Destilação/métodos , Fluoretos/sangue , Fluoretos/urina , Cromatografia/instrumentação , Humanos , Interações Hidrofóbicas e Hidrofílicas
15.
Anal Chim Acta ; 970: 73-81, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28433061

RESUMO

Carbonaceous stationary phases have gained much attention for their peculiar selectivity and robustness. Herein we report the fabrication and application of a graphene-coated polymeric stationary phase for anion exchange chromatography. The graphene-coated particles were fabricated by a facile evaporation-reduction method. These hydrophilic particles were proven appropriate substrates for grafting of hyperbranched condensation polymers (HBCPs) to make pellicular anion exchangers. The new phase was characterized by zeta potentials, Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscope. Frontal displacement chromatography showed that the capacities of the anion exchangers were tuned by both graphene amount and HBCPs layer count. The chromatographic performance of graphene-coated anion exchangers was demonstrated with separation of inorganic anions, organic acids, carbohydrates and amino acids. Good reproducibility was obtained by consecutive injections, indicating high chemical stability of the coating.

16.
J Chromatogr A ; 1515: 69-80, 2017 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-28807548

RESUMO

This work illustrates the introduction of a simple, rugged and flexible column-switching ion chromatography (IC) technique for an automated on-line QuEChERS extracted samples extracts washing followed by sensitive fluorescence (FLD) determination of five acidic pharmaceutical drugs namely; clofibric acid (CLO), ibuprofen (IBU), aspirin (ASP), naproxen (NAP) and flurobrofen (FLU) in three complex samples (spinach, apple and hospital sewage sludge). An old anion exchange column IonPac® AS11-HC was utilized as a pre-treatment column for on-line washing of inorganic and organic interferences followed by isocratic separation of five acidic drugs with another anion exchange IonPac® AS12A analytical column by exploiting the column-switching technique. This novel method exhibited good linearity with correlation coefficients (r2) for all drugs were in the range 0.976-0.996. The limit of detection and quantification of all five acidic drugs were in the range 0.024µg/kg to 8.70µg/kg and 0.082µg/kg to 0.029mg/kg, respectively, and better recoveries in the range 81.17-112.5% with percentage relative standard deviations (RSDs) less than 17.8% were obtained. This on-line sample pre-treatment method showed minimum matrix effect in the range of 0.87-1.25 except for aspirin. This simple rugged and flexible column-switching system required only 28min for maximum elimination of matrices and interferences in three complex samples extracts, isocratic separation of five acidic drugs and for the continuous regeneration of pre-treatment column prior to every subsequent analysis. Finally, this simple automated IC system was appeared so rugged and flexible, which can eliminate and wash out most of interference, impurities and matrices in complex samples, simply by adjusting the NaOH and acetonitrile concentration in washing mobile phase with maximum recoveries of acidic analytes of interest.


Assuntos
Ácidos/análise , Técnicas de Química Analítica/métodos , Cromatografia por Troca Iônica , Preparações Farmacêuticas/análise , Misturas Complexas/química , Fluorescência , Limite de Detecção
17.
Talanta ; 168: 188-195, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28391841

RESUMO

A novel high performance liquid stationary phase was prepared by grafting poly amidoamine (PAMAM) dendrimers to poly (styrene-divinyl benzene-glycidylmethacrylate) matrix in this work. Different generations of PAMAM dendrimers grafted to polymer matrices containing different glycidylmethacrylate amounts by reacting with epoxy groups in glycidylmethacrylate molecules. The synthesized PAMAM dendrimers and stationary phase were characterized by fourier transform infrared spectroscopy, scanning electron microscope, N2 adsorption/desorption, elemental analysis and thermo gravimetric analyzer. The proposed stationary phase was suitable for rapid separation of phenylene diamine isomers and aminobenzene. The separation mechanism of benzene rings attraction and amino repulsion was verified by retention behaviors of methylamine, phenylamine, phenylene diamine, naphthylamine and toluene. The reliability of the stationary phase was demonstrated by separation and determination of phenylene diamine isomers including m-phenylene diamine, o-phenylene diamine and p-phenylene diamine in hair dye precursors within 10min. Satisfactory resolution and short analysis time make the columns promising for determination of aniline compounds in various fields.

18.
Food Chem ; 204: 358-364, 2016 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-26988513

RESUMO

Sucralose is widely used in food and beverages as sweetener. Current synthesis approaches typically provide sucralose products with varying levels of related chlorinated carbohydrates which can affect the taste and flavor-modifying properties of sucralose. Quantification of related compounds in sucralose is often hampered by the lack of commercially available standards. In this work, nine related compounds were purified (purity>97%) and identified by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR), then a rapid and simple HPLC coupled with evaporative light scattering detection (ELSD) method has been developed for the simultaneous determination of sucralose and related compounds. Under optimized conditions, the method showed good linearity in the range of 2-600µgmL(-1) with determination coefficients R(2)⩾0.9990. Moreover, low limits of detection in the range of 0.5-2.0µgmL(-1) and good repeatability (RSD<3%, n=6) were obtained. Recoveries were from 96.8% to 101.2%. Finally, the method has been successfully applied to sucralose quality control and purification process monitoring.


Assuntos
Cromatografia Líquida de Alta Pressão , Análise de Alimentos/métodos , Sacarose/análogos & derivados , Difusão Dinâmica da Luz , Limite de Detecção , Espectroscopia de Ressonância Magnética , Controle de Qualidade , Reprodutibilidade dos Testes , Sacarose/análise , Edulcorantes/análise
19.
J Chromatogr A ; 1449: 71-7, 2016 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-27139218

RESUMO

A standard-free and sensitive method was developed for analysis of sucrose acetates in a crude 6-O-acetyl sucrose (S-6-a) product by on-line hydrolysis-high-performance liquid chromatography with pulsed amperometric detection (PAD). Sucrose, three regio-isomers of acetyl sucrose and five regio-isomers of diacetyl sucrose were separated on a C18 column using 3% (v/v) acetonitrile in water as eluent within 25min. After purification with LC followed by semi-preparative HPLC, their chemical structures were identified by 1D, 2D NMR and LC-MS. Moreover, quantification of those regio-isomers was achieved by on-line alkaline hydrolysis to liberate sucrose using a post-column delivery system, and then detected by PAD for indirect estimation of the sucrose acetate content. Under optimal conditions, the linear ranges were from 0.03 to 150µmolL(-1) for sucrose corresponding to sucrose acetates with coefficient of determination as 0.9997 and detection limit as 0.01µmolL(-1) (S/N=3). Good repeatability was obtained (RSD<3%, n=6). Furthermore, this method has been successfully applied to the analysis of sucrose and sucrose acetates in a crude S-6-a product during synthesis, purification and structure elucidation studies. The recoveries were from 94.89% to 102.31% for sucrose and sucrose acetates.


Assuntos
Sacarose/análogos & derivados , Cromatografia Líquida de Alta Pressão/métodos , Hidrólise , Limite de Detecção , Estereoisomerismo , Sacarose/análise , Sacarose/química
20.
J Chromatogr A ; 1468: 73-78, 2016 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-27639890

RESUMO

This work reports the application of hydrothermal carbon nanospheres (HCNSs) as stationary phases in ion chromatography. HCNSs were facilely quaternized through polycondensation of methylamine and 1,4-butanediol diglycidyl ether. The quaternization was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Owing to the electrostatic interaction, quaternized HCNSs were equably attached onto the surface of sulfonated polystyrene-divinylbenzene (PS-DVB) beads to construct the anion exchangers. The aggregation was verified by scanning electron microscopy and elemental analysis. Common anions, aliphatic monocarboxylic acids, polarizable anions, and aromatic acids were well separated on the stationary phases with good stability and symmetry. The prepared column was further applied to detect phosphate content in Cola drink samples. The limit of detection (S/N=3) was 0.09mg/L, and the relative standard deviation (n=10) of retention time was 0.31%. The average recovery was 99.58%.


Assuntos
Carbono/química , Cromatografia por Troca Iônica , Análise de Alimentos/métodos , Nanosferas/química , Fosfatos/análise , Ânions/química , Bebidas Gaseificadas/análise , Microscopia Eletrônica de Varredura , Nanosferas/ultraestrutura , Espectroscopia Fotoeletrônica
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