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1.
J Sep Sci ; 47(18): e202400536, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39302689

RESUMO

Relative to suppressed conductometric anion exchange chromatography, conductometric ion exclusion chromatography (IEC) is much less popular. Poor limit of detection and manual preparation of eluent are primarily responsible for this. We describe an electrodialytic phosphoric eluent generator for the online production of phosphoric acid eluent at a concentration exceeding 35 mM. It is a sandwiched configuration consisting of three channels isolated by stacked anion exchange membranes and a bipolar membrane plus stacked anion exchange membrane. Such a unique configuration ensures the production of gas-free eluent, obviating the need for a gas removal device. The resulting eluent concentration is controlled by varying the current. Coupled with an ultraviolet absorbance detector, a 0.04-16.67 mg/L limit of detection for model organic acids was achieved by IEC equipped with an electrodialytic phosphoric eluent generator.

2.
Talanta ; 280: 126697, 2024 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-39142132

RESUMO

We describe a nitrogen-specific detector (NSD) for aqueous mobile phase-based high performance liquid chromatography (HPLC). It is based by means of total hydrophilic organic nitrogen detection. Separated analytes are photooxidized online and converted to nitrate, followed by an ultravilet absorbance detector. It features response dependant on the product of nitrogen number in the molecule and its molar concentration, no matter what is ultravilet-absorbing or not. The HPLC equipped with NSD can quantify nitrogen-containing analytes via a sole standard of potassium nitrate for calibration. This results in identical calibration curve for all nitrogen-containing analytes, obviating individual calibration. The limit of detection of NSD is 4.3 µM N/L, and its linear range is up to 4 mM N/L.

3.
Front Psychol ; 15: 1423540, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39045443

RESUMO

In today's volatile, uncertain, complex, and ambiguous (VUCA) work environments, mitigating employee burnout and turnover has become a critical concern. The enhancement of employee engagement stands out as a pivotal focus in corporate human resource management. Coaching leadership focuses on the encouragement and inspiration of employees, which can effectively stimulate the internal potential of employees, enhance work ability and enhance engagement. However, previous research on the relationship between coaching leadership style and employee engagement are limited, thus obscures the essential function in enterprise development and core competitiveness. The research collected 402 valid responses from MBA and EMBA students at the School of Business, and examines the effect of coaching leadership on employee engagement. Results indicate that coaching leadership significantly enhances multiple facets of employee engagement, including vigor, devotion, and absorption. Crucially, organizational self-esteem emerges as a mediating factor, while learning goal orientation strengthens the positive effects of coaching leadership. This research sheds light on the nuanced dynamics of effective leadership in contemporary workplaces, also it underscores the need for more nuanced, industry-specific analyses and broader exploration of moderating variables. Ultimately, the insights garnered hold profound implications for leadership training, human resource strategies, and performance metrics, emphasizing a more integrative and holistic approach to leadership and employee development in vocational contexts.

4.
J Chromatogr A ; 1722: 464904, 2024 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-38626539

RESUMO

A continuously regenerated cationic impurity removal device (CR-CRD) has been fabricated and applied for ion chromatography (IC). The removal of cationic impurities is realized by electrodialytically replacing the cationic impurities with hydronium ions. The device is configured in a sandwich structure and the central eluent channel is respectively isolated from both electrodes by stacked cation exchange membranes and a bipolar membrane (BPM) plus stacked anion exchange membranes. The eluent channel is packed with cation exchange resins in hydronium form and their continuous regeneration can be achieved by electrodialysis. A desirable feature of the device is gas-free, and no degasser is required. It showed sufficient ability to remove cationic impurities, as indicated by > 99.9 % removal of 10 mL of 1 mM LiOH solution injected (∼10 µmol) or continuous removal of 1 mM LiOH solution at the flow rate of 1 mL/min (1 µmol/min). A useful application was for sample pretreatment in nuclear power industry, by eliminating strong matrix interference of the sample containing LiOH (1 mM) and boric acid (2000 mg/L) with trace anion analysis.


Assuntos
Cátions , Cromatografia por Troca Iônica/métodos , Cromatografia por Troca Iônica/instrumentação , Cátions/química , Membranas Artificiais , Resinas de Troca de Cátion/química , Desenho de Equipamento
5.
J Sep Sci ; 47(1): e2300905, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38143272

RESUMO

Simultaneous chromatographic separation of the anomers of saccharides was achieved by using a polymer zwitterionic stationary phase functionalized by acrylamide-type sulfobetaine. By optimization of separation parameters including column temperature, pH, and flow rate, the column operated in hydrophilic interaction chromatography mode exhibited excellent separation selectivity toward five monosaccharides and their anomers (including ribose, xylose, galactose, glucose, and arabinose) and two disaccharides (lactose and maltose). Baseline separation could be achieved at mild operation conditions such as 20-30°C of column temperature or typical mobile phase composition (85% acetrontrile-15% 20 mM ammonium formate [NH4 FA]) with wide pH tolerance range of 2-8. This offers a rapid way to determine the configuration of α or ß anomer of the saccharides.


Assuntos
Carboidratos , Polímeros , Cromatografia , Betaína/química , Interações Hidrofóbicas e Hidrofílicas
6.
Opt Lett ; 48(23): 6279-6282, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-38039246

RESUMO

A 4H-silicon carbide-on-insulator (4H-SiCOI) has emerged as a prominent material contender for integrated photonics owing to its outstanding material properties such as CMOS compatibility, high refractive index, and high second- and third-order nonlinearities. Although various micro-resonators have been realized on the 4H-SiCOI platform, enabling numerous applications including frequency conversion and electro-optical modulators, they may suffer from a challenge associated with spatial mode interactions, primarily due to the widespread use of multimode waveguides. We study the suppression of spatial mode interaction with Euler bends, and demonstrate micro-resonators with improved Q values above 1 × 105 on ion-sliced 4H-SiCOI platform with a SiC thickness nonuniformity less than 1%. The spatial-mode-interaction-free micro-resonators reported on the CMOS-compatible wafer-scale 4H-SiCOI platform would constitute an important ingredient for the envisaged large-scale integrated nonlinear photonic circuits.

7.
J Chromatogr A ; 1708: 464328, 2023 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-37666063

RESUMO

A novel polymer-based polar stationary phase for hydrophilic interaction chromatography (HILIC) is described. It was obtained by grafting lysine and acrylamide onto poly (glycidyl methacrylate-divinylbenzene) (GMA-DVB) microspheres via ring-opening reaction of epoxy groups and free radical polymerization with pendant double bonds of the microspheres. Multiple types of polar groups including zwitterionic (carboxylate and amine), amide and diol onto the microspheres make them highly hydrophilic. It showed typical HILIC character and good separation performance towards model polar analytes. Negligible bleed level under gradient elution mode (up to 50% fraction of water) was observed. It also exhibited specific separation selectivity to ionic analytes and simultaneous separation of anions and cations could be achieved in ideal electrostatic selectivity elution order, e.g. I-< NO3-

Assuntos
Amidas , Lisina , Acrilamida , Aminas , Cromatografia
8.
J Chromatogr A ; 1689: 463711, 2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36586280

RESUMO

A polyethyleneimine (PEI)-functionalized polymer substrate polar stationary phase was prepared for hydrophilic interaction chromatography (HILIC) by grafting PEI onto poly(styrene-divinylbenzene) (PS-DVB) microspheres. The phase shows a U-shape retention profile and it exhibits typical hydrophilic characteristic when the organic solvent fraction in the mobile phase is > 60%. Hydrogen bonding, anion exchange, and hydrophobic interaction are involved in the retention mechanism. Good separation and unique selectivity for acidic, basic and neutral polar analytes were achieved. It showed extremely low column bleed (comparable to that of blank) under gradient elution mode (even to 50% fraction of water) and wide pH tollerance range (at least 1-13).


Assuntos
Polietilenoimina , Polímeros , Polietilenoimina/química , Cromatografia Líquida/métodos , Cromatografia de Fase Reversa/métodos , Solventes , Interações Hidrofóbicas e Hidrofílicas
9.
J Sep Sci ; 45(21): 3995-4000, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36050904

RESUMO

A strong anion exchanger applied for ion chromatography is described by grafting methacrylamido propyl trimethyl ammonium chloride onto hydrolyzed poly(glycidyl methacrylate-divinylbenzene) substrate. The anion exchanger has been in detail characterized and the final capacity of the anion exchanger can be readily manipulated by different monomer amounts. It exhibited obvious temperature-sensitive properties and large tolerance to the samples with high ionic strength. The obtained anion exchanger demonstrated effective separation ability towards the common seven inorganic anions within 12 min and high separation efficiency, for example, 58 000/m of theoretical plate count for chloride.


Assuntos
Compostos de Amônio , Cromatografia por Troca Iônica/métodos , Ânions , Cátions
10.
Se Pu ; 40(8): 730-735, 2022 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-35903840

RESUMO

A polymer-based strong anion stationary phase modified by quaternary ammoniated allyl glycidyl ether (AGE) for ion chromatography (IC) was developed. It was prepared by surface copolymerization between AGE and the pedant double bonds associated with hydrolyzed poly(glycidylmethacrylate-divinylbenzene) (GMA-DVB) substrate, followed by quaternization with N,N-methyldiethanolamine (a tertiary amine, MDEA). The synthesis conditions were optimized, including the type of organic tertiary amines (MDEA, N,N-dimethylethanolamine, trimethylamine), substrate hydrolysis, the amount of monomer and initiator, reaction temperature and reaction time. The obtained anion stationary phase was characterized by scanning electron microscope and elemental analysis. MDEA was observed to be the best quaternization reagent since the anion exchanger obtained by such reagent showed good separation and suitable retention time towards model inorganic anions. The resulting reason probably lies in higher hydrophilicity of MDEA relative the other two ones. The use of rich epoxy groups of GMA-DVB to introduce the functional groups was commonly used in many previous reports. Here the epoxy groups were firstly hydrolyzed to be diol groups and the pendant double bonds onto the surface of GMA-DVB particles were used to graft AGE. The data achieved indicated that the use of hydrolyzed GMA-DVB substrate would be helpful to reduce anion exchange capacity and unwanted non-ion exchange interaction, in which the rich epoxy groups were converted to hydroxy groups. More important, the obtained anion exchanger after hydrolytic treatment could offer a significantly reduction of retention time (~68%) and a ~1.67-fold higher plate count (take Br- as an example). The apparent capacity of the phase was computed to be 264 µmol/g by content of N data and its effective capacity was measured to be 98.5 µmol/column by the breakthrough curve method. Under the optimal chromatographic conditions, the obtained stationary phase showed baseline separation of seven common inorganic anions in less than 13 min using carbonate-bicarbonate mixed eluent, exhibiting high separation efficiency and peak shape, e. g. 49000 plate/m and 38000 plate/m of the theoretical plate counts respectively for chloride and nitrate, and their asymmetric factor were 1.3 and 1.4. These can be comparable or slightly higher than those of commercial columns. The fitted equation of the eluent concentration and the retention factors of model anions was proved that ion exchange model dominates the retention mechanism of the anion stationary phase. This offers a simple way to prepare anion exchanger and to manipulate anion exchange capacity. The utility of the obtained anion exchanger has been demonstrated to the analysis of tap water.


Assuntos
Compostos de Epóxi , Ânions , Cromatografia por Troca Iônica/métodos , Compostos de Epóxi/química , Interações Hidrofóbicas e Hidrofílicas
11.
Anal Chem ; 94(19): 6924-6929, 2022 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-35503857

RESUMO

A gas-free continuously regenerated-anion impurity removal device (CR-ARD) is described for ion chromatography (IC). It is a sandwiched configuration consisting of three channels. The central eluent channel is isolated from two outer regenerant channels by stacked anion exchange membranes (sAEM) and a bipolar membrane (BPM) plus stacked cation exchange membranes (BPM-sCEM), in which the anion exchange side of BPM is facing the central channel. The sAEM side is an anode with respect to the cathode of the BPM-sCEM side. The central channel is packed with strongly basic anion exchange resins in hydroxide form. The application of an electrical voltage to the device causes enhanced water splitting at the interface of BPM to occur and the potential drives the hydroxide ions through the resin phase toward the anode, thereby enabling continuous regeneration of the resin and avoiding any off-line regeneration. Meanwhile, nonhydroxide anionic impurities (basically carbonate) are transported toward the anode through the sAEM. It does not produce gas in the eluent channel, and no degasser is required afterward. It shows a strong ability to remove anionic impurities, as indicated by effective removal of 5 mM CO32- injected sample plug (25 µL, 125 pmol) or continuous removal of 600 µM KNO3 solution at 1 mL/min (10 nmol/s) over 300 min. Much improved peak integration at the gradient mode and a higher signal-to-noise ratio at the isocratic mode can be achieved by CR-ARD. To our knowledge, this is the first account of gas-free CR-ARD.


Assuntos
Resinas de Troca Aniônica , Hidróxidos , Cátions , Cromatografia por Troca Iônica/métodos , Regeneração
12.
J Chromatogr A ; 1670: 462946, 2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35325650

RESUMO

A polymer polar stationary phase functionalized with hyperbranched polyglycerol for hydrophilic interaction chromatography (HILIC) is described. It is prepared via surface-initiated ring-opening polymerization of hyperbranched polyglycerol onto hydrolzed poly(glycidyl methacrylate-divinylbenzene) microspheres. The capacity of the functional groups can be maniputed by repeating hyperbranch layers. The phase showed typical HILIC character with good separation performance towards tested polar analytes. It also exhibited wider pH tolerance range (e.g. at least 2 to 12) and as well negligible bleed level under gradient elution mode (even to 50% fraction of water).


Assuntos
Glicerol , Polímeros , Interações Hidrofóbicas e Hidrofílicas , Polimerização , Polímeros/química
13.
J Chromatogr A ; 1666: 462857, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-35123167

RESUMO

An integrated dual-functional electrodialytic membrane suppressor (D-EMS) is proposed that can simultaneously conduct suppression of acid and base eluent. It consists of four chambers, equivalent to half an anion electrolytic membrane suppressor (EMS) plus half a cation EMS with typical sandwiched configuration via a bipolar membrane (BPM). Anion exchange membrane, BPM and cation exchange membrane are respectively used to isolate two central eluent channels from two outer regenerant chambers. A constant current source is used to power d-EMS. The device shows similar performance to a separate EMS in terms of suppression capacity (≥80 µeq/min, corresponding to 80 mM eluent at the flow rate of 1 mL/min) and the resultant suppressed background (∼0.75 µS/cm and ∼0.17 µS/cm for anion and cation section of d-EMS, respectively).


Assuntos
Eletricidade , Eletrólise , Ânions/química , Cátions , Cromatografia por Troca Iônica/métodos
14.
Talanta ; 237: 122964, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34736689

RESUMO

We describe a reagent-free acid-base titration method, in which only water is added and the titrant is online electrodialytically produced. Electrodialytic eluent generator, a well-established technique in ion chromatography to produce high purity base or acid eluent through precise control of an electric current, has been for the first time used for titration, termed as electrodialytic titrant generator (ETG). Three kinds of titrants produced by ETG have been demonstrated, including potassium hydroxide, methanesulfuric acid and sulfuric acid. A series of titrants with different concentration up to at least 140 mM (e.g. KOH) could be accurately and reproducibly obtained by manipulating current and the KOH titrant showed extremely high purity. The titration results achieved by ETG were in a good agreement with those obtained by the regular way and their ratio was in the range of 0.9918 and 1.0034. Good accuracy and precision were achieved for ETG titration, as indicated by 2.2% of relative error and 0.17% of relative standard error. Its utility was demonstrated to measure pKa-differentiated capacity of anion exchange resins.


Assuntos
Água , Cromatografia por Troca Iônica , Indicadores e Reagentes
15.
Analyst ; 147(2): 208-212, 2022 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-34928282

RESUMO

A simple dissolved inorganic carbon (DIC) measurement method featuring self-calibration function via an electrodialytic bicarbonate eluent generator (cEDG) is described. It is based on gas diffusion flow analysis system that uses conductometric detection for sensing the resultant conductivity changes of the effluent caused by CO2 penetration. The standard carbon sources with concentration ranging from 0.1 to 6 mM produced online by cEDG are for DIC calibration, eliminating manual preparation.

16.
Chemosphere ; 292: 133378, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34952027

RESUMO

Chlorinated cyanurates (CCAs) are a type of disinfectants currently used worldwide for fight of Coronavirus. However, CCAs upon dosed into water can release not only free chlorine (FC), a strong disinfectant, but also cyanurate (CYA), a persistent compound potentially harmful to human and environment. Therefore, detecting CYA and FC in water are very important not only for ensuring sufficient disinfection but also for monitoring the impacts of FC and CYA on receiving watershed. However, conventional analytical methods for them are mostly based on colorimetric methods, which have high method detection limits (MDLs) and rely on chemical reactions that are likely sensitive to coexisting chemicals. To overcome these issues, we herein proposed a facile and reaction-free method to detect CYA and FC together in just one run by ion chromatography (IC) equipped with both conductivity and ultraviolet absorbance detectors. The method features obvious advantages over colorimetric methods in being lower MDLs (3.6 µg/L for CYA and 9.0 µg/L for FC), environmental-friendly (i.e., no organic solvent involved), and more resistant to alkaline solution. With this method, trace levels of CYA (i.e., 34-44 µg/L), which were nondetectable by conventional method, were found in two river water samples, implying that the local environment was already polluted by CCAs during the pandemic period. Overall, this study demonstrates a robust tool that may assist better understanding and monitoring the fate and transport of trace CCA derivatives in water.


Assuntos
Cloro , Desinfetantes , Cromatografia , Desinfecção , Humanos , Triazinas
17.
J Agric Food Chem ; 69(50): 15425-15433, 2021 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-34898196

RESUMO

We have described a sulfonamide-selective ambient ion source coupled with electrospray ionization mass spectrometry (ESI-MS) for selective extraction and determination of trace sulfonamide antibiotics. It is obtained by modifying an iron sheet with a sulfadiazine-templated hydrophilic molecularly imprinted polymer (SF-HMIP). It behaves as both an online extractor and a MS ion source. Five sulfonamide antibiotics, including sulfamethoxazole (SMZ), sulfamerazine (SMR), sulfisoxazole (SIZ), sulfathiazole (ST), and sulfameter (SMD), were chosen to evaluate SF-HMIP coupled with ESI-MS, which showed good linearity in the range of 0.2-1000 ng/mL with correlation coefficient values (R2) over 0.9946. The limits of detection (LODs) for analysis of pure water and honey were in the range of 0.1-0.2 and 0.2-1.5 ng/mL, respectively. Limits of quantitation (LOQs) for analysis of pure water and honey were in the range of 0.3-0.5 and 1.0-5.0 ng/mL, respectively. The results demonstrated that SF-HMIP combined with ESI-MS could be applied for the direct analysis of five trace sulfonamide compounds in honey and pure water with recoveries ranging from 76 to 129%.


Assuntos
Mel , Polímeros Molecularmente Impressos , Mel/análise , Ferro , Extração em Fase Sólida , Espectrometria de Massas por Ionização por Electrospray , Sulfonamidas
18.
Front Psychol ; 12: 581183, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34434132

RESUMO

Over the past few decades, researchers have explored the effects of experiential purchases and material purchases on happiness and provided a range of evidence that consumers yield greater happiness from experiential purchases compared with material purchases. However, limited research is known about the relationship between these two types of purchases within the broader context of negative emotion. Specifically, the current research focuses on the effect of experiential purchases on loneliness alleviation to replenish this research stream. Three experiments were conducted to explore the effect of experiential purchases (vs. material purchases) on alleviating loneliness. The results showed that experiential purchases have a stronger effect on loneliness alleviation than material purchases, which is mediated by relationship enhancement. In addition, purchases of social nature moderate the effect of experiential purchases on loneliness. Social experiential purchases lead to a higher degree of relief of loneliness. On the contrary, for the solitary experiential purchases, the effect of experiential purchases on loneliness is less tight. The current research supplements the research on negative emotions of experiential purchases and expands the research area of experiential purchases, which also provides new insights into coping strategies of loneliness.

19.
Light Sci Appl ; 10(1): 139, 2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34226498

RESUMO

The realization of high-quality (Q) resonators regardless of the underpinning material platforms has been a ceaseless pursuit, because the high-Q resonators provide an extreme environment for confining light to enable observations of many nonlinear optical phenomenon with high efficiencies. Here, photonic microresonators with a mean Q factor of 6.75 × 106 were demonstrated on a 4H-silicon-carbide-on-insulator (4H-SiCOI) platform, as determined by a statistical analysis of tens of resonances. Using these devices, broadband frequency conversions, including second-, third-, and fourth-harmonic generations have been observed. Cascaded Raman lasing has also been demonstrated in our SiC microresonator for the first time, to the best of our knowledge. Meanwhile, by engineering the dispersion properties of the SiC microresonator, we have achieved broadband Kerr frequency combs covering from 1300 to 1700 nm. Our demonstration represents a significant milestone in the development of SiC photonic integrated devices.

20.
Se Pu ; 39(2): 130-133, 2021 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-34227345

RESUMO

An electrodialysis device is used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric potential. They can produce hydronium or hydroxide ions via electrodialysis water, which can be used for online preparation of eluents or suppression or detection in ion chromatography (IC). As opposed to the manual preparation of eluents or regenerant solutions, electrodialysis devices have the advantages such as green, efficient and high purity. Thus, IC systems equipped with electrodialysis devices dominate the majority uses of IC system, and more importantly, find widespread application. The present thesis briefly summarizes the latest developments in this area.

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