高效液相色谱-电感耦合等离子体质谱法测定人尿中硒形态

采用高效液相色谱-电感耦合等离子体质谱法(HPLC-ICP/MS)测定人尿中硒代胱氨酸(SeCys₂)、甲基硒代半胱氨酸(MeSeCys)、亚硒酸盐[Se(Ⅳ)]、硒代蛋氨酸(SeMet)、硒酸盐[Se(Ⅵ)]5种硒形态。样品经超纯水稀释后,采用Hamilton PRP-X100色谱柱(250 mm×4 mm,10μm)分离,以40 mmol/L磷酸氢二铵(含1%甲醇,pH 5)为流动相进行等度洗脱,13 min内可将5种硒形态分离。5种硒形态的线性范围为0～300.0μg/L,相关系数(r)均大于0.999,检出限为0.2～0.5μg/L。除SeCys₂的加标回收率为37.7%～70.4%外,MeSeCys、Se(Ⅳ)、SeMet、Se(Ⅵ)的加标回收率为80.0%～123%;5种硒形态的相对标准偏差(RSD)均不大于7.8%。应用该方法测定实际样品,结果显示人尿中硒形态主要以SeCys₂为主,同时含有少量MeSeCys、SeMet、无机硒及未知含硒化合物。     

高效液相色谱-电感耦合等离子体质谱法同时测定食品中7种硒形态

采用高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)联用技术同时测定食品中7种硒形态。样品均质后先用水超声萃取2 h,离心分离后,采用ZORBAX SB-Aq C_(18)色谱柱(250 mm×4.6 mm,5μm),以20 mmol/L柠檬酸+5 mmol/L已烷磺酸钠(pH=4.4)为流动相等度洗脱,Se(Ⅳ)、Se(Ⅵ)、硒代胱氨酸(SeCys2)、甲基硒代半胱氨酸(SeMeCys)、硒脲(SeUr)、硒代蛋氨酸(SeMet)、硒代乙硫氨酸(SeEt)7种硒形态在10 min内达到完全分离。7种硒形态化合物的质量浓度在2.5～100.0μg/L范围内与峰面积呈线性关系,检测限(S/N=3)为0.005 mg/kg。加标回收率在71.9%～116.7%之间,相对标准偏差(n=6)在1.62%～18.48%之间。该方法精密度及准确度高,重现性好,适用于食品中上述7种硒形态化合物的同时快速测定。     

离子交换色谱-氢化物发生原子荧光法测定水产品中硒的形态

建立了利用离子交换色谱-原子荧光联用技术同时测定水产品中3种硒形态的方法,研究了仪器的工作条件、载流、KBH4浓度对硒荧光信号值的影响。采用Hamilton PRP X-100色谱柱(250×4.1 mm,10μm),以30 mmol/L NH4H2PO4为流动相,可以在10 min内同时分离、检测了硒代胱氨酸SeCys、硒代蛋氨酸SeMet和Se(Ⅳ)。当3种形态的质量浓度范围为0~80μg/L时,各形态均得到良好的线性关系,线性相关系数均大于0.9990,各形态的检出限分别为SeCys 1.66μg/L,SeMet 0.91μg/L,Se(Ⅳ)1.10μg/L,相对标准偏差RSD均小于5%(n=11)。在最佳条件下,应用该方法测定了水产品中的硒形态,3种硒形态化合物加标回收率在87.3%~102.6%之间。方法可满足水产品中硒形态的定量分析。     

高效液相色谱-电感耦合等离子体质谱联用检测食品中的五种硒形态

建立了高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)联用检测硒酸盐(SeVI)、亚硒酸盐(SeIV)、硒代蛋氨酸(SeMet)、硒代胱氨酸(SeCys2)和硒代乙硫氨酸(SeEt)的方法。采用Hamilton PRP X-100色谱柱（250 mm×4.6 mm, 5 μm）,使用5 mmol/L的柠檬酸溶液(pH 4.5)作为流动相,电感耦合等离子体质谱(ICP-MS)检测,在21 min内可以完全分离5种硒形态。各形态硒的线性相关系数均大于0.9995, SeVI、SeIV、SeMet、SeCys2、SeEt的检出限分别为0.4、0.4、5.6、0.9、1.2 μg/L。探讨了不同提取方法的提取效果,鲜蘑菇和猪肉样品加标回收实验表明,对水溶性良好的无机硒和硒代蛋氨酸而言,采用柠檬酸溶液提取的效果非常好,SeIV和SeVI的回收率均在100%左右,SeMet的回收率为85.0%～95.3%;用蛋白酶水解提取,SeCys2和SeEt的回收率为79.9%～91.5%。该方法可完全满足食品中这5种硒形态的准确定量分析。     

液相色谱-双通道原子荧光检测联用法同时测定砷和硒的形态

建立了一种利用高效液相色谱-双通道原子荧光检测联用同时进行砷和硒形态分析的方法。以10 mmol/L NH4H2PO4溶液(pH 5.6)(添加2.5%(体积分数)的甲醇)为流动相,在12 min内同时分离了三价砷(As(III))、一甲基砷(MMA)、二甲基砷(DMA)、五价砷(As(V))、硒代胱氨酸(SeCys)、硒代蛋氨酸(SeMet)和四价硒［Se(IV)］等化合物。As(III)、DMA、MMA、As(V)、SeCys、SeMet和Se(IV)的检出限分别为1,3,2,3,4,18和3 μg/L (进样量为200 μL),5次测定的相对标准偏差为1.9%～6.1%(As 100 μg/L, Se 300 μg/L)。应用该方法对人体尿样及硒酵母片中砷和硒的形态进行了分析,目标物在尿样中的加标回收率为83%～108%,在硒酵母片中的加标回收率为88%～105%。实验结果表明,该方法可用于尿样及药品中砷和硒形态的日常分析。该方法减少了样品的分析时间和试剂用量,降低了工作强度,提高了工作效率。     

高效液相色谱-电感耦合等离子体质谱（HPLC-ICP-MS）联用测定富硒小麦中硒代氨基酸

为科学补硒和促进富硒小麦的种植推广,建立了高效液相色谱-电感耦合等离子体质谱联用技术(HPLC-ICP-MS)检测富硒小麦中硒代氨基酸的方法。用蛋白酶XIV辅助微波振荡提取富硒小麦中硒代氨基酸,采用C18 分离柱分离,以30.0mmol/L磷酸氢二铵+1.0%甲醇+2.0mmol/L四丁基溴化铵溶液(pH=6.5)为流动相,能在10min内实现5种硒代氨基酸的分离。在高能氦气模式（HEHe）下,用78Se的色谱峰积分面积作为定量依据,5种硒代氨基酸在1.0～200.0μg/L范围内线性相关性良好,检出限在 0.11~0.29μg/L之间。以富硒小麦为基体进行加标回收试验,除硒代胱氨酸（SeCys2）可能不稳定,易分解造成回收率偏低外,其他4种硒代氨基酸的加标回收率在92.34～102.46%之间,相对标准偏差为 1.6 %~4.2 %（n=7）。用该方法测定了农业科技工作者种植推广的富硒小麦,结果发现小麦中的硒赋存形态多为硒代蛋氨酸（SeMet）,此外,小麦中还含有少量硒代胱氨酸（SeCys2）、硒代半胱氨酸（SeCys）、甲基硒代半胱氨酸（MeSeCys）和硒代乙硫氨酸（SeEt)。该方法具有良好的精密度和准确度,适用于富硒小麦中硒代氨基酸的形态分析。     

Role of transition metal oxides in g-C3N4-based heterojunctions for photocatalysis and supercapacitors

g-C₃ N₄ emerges as a star 2 D photocatalyst due to its unique layered structure,suitable band structure and low cost.However,its photocatalytic application is limited by the fast charge recombination and low photoabsorption.Rationally designing g-C₃ N_4-based heterojunction is promising for improving photocatalytic activity.Besides,g-C₃ N₄ exhibits great potentials in electrochemical energy storage,In view of the excellent performa...     

微波辅助萃取-液质联用技术测底泥砷、硒的化学形态

建立了用反相离子对色谱和电感耦合等离子体质谱的联用技术同时测定As（Ⅲ）、 As（Ⅴ）、 MMA、 DMA、 Se（Ⅳ）、 Se（Ⅵ）、 SeMet和SeCys的砷、硒化学形态分析方法. 分别从流动相pH值、离子对试剂的浓度、甲醇量和流速4个方面进行了分离测定条件的优化. 利用碰撞池技术（CCT）较好地解决了^40Ar^35Cl^＋复合离子对^75As的干扰, 并使^80Se的测定成为可能, 有效地提高了灵敏度. 将该方法应用于上海市苏州河底泥样品的微波辅助萃取液的形态分析中, 砷和硒的检出限分别达到0.4～1.3 和0.5～1.9 μg/L.     

氮缺陷石墨相氮化碳的制备及其光催化降解环境有机污染物性能

通过在三聚氰胺热分解过程中加入NaHCO₃制备出具有氮缺陷的石墨相氮化碳（g-C₃N₄）,利用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、N₂吸附-脱附、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征,并在可见光（λ> 420nm）照射下,以水相中罗丹明B（RhB）的降解为模型反应,研究了该氮缺陷g-C₃N₄对有机污染物降解的光催化活性。结果表明,引入氮缺陷可以提高g-C₃N₄对可见光的吸收以及电子-空穴对的分离效率,进而提高g-C₃N₄的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30min内对RhB的降解率分别为79.8%、100.0%和87.6%;而在相同条件下,没有氮缺陷的g-C₃N₄对RhB的降解率仅为59.8%。     

离子交换色谱-氢化物发生双道原子荧光法同时测定砷和硒形态

建立了离子交换色谱-氢化物发生双道原子荧光联用同时测定4种As形态和3种Se形态的方法,并优化了各种实验参数。采用PRP-X100阴离子交换分析柱可以在10min内同时分离、检测As和Se形态。在8%HCl和1.5%(m/V)KBH4的氢化物反应条件下,进样量100μL,各形态的检出限为:As(Ⅲ)0.2μg/L、DMA0.3μg/L、MMA0.2μg/L、As(Ⅴ)0.3μg/L、SeCys0.6μg/L、Se(Ⅳ)0.5μg/L、SeMet3μg/L。当各As形态浓度为100μg/L、各Se形态浓度为200μg/L,各形态的精密度RSD(n=7)均小于5%。当各As形态浓度范围为5～100μg/L、SeCys和Se(Ⅳ)浓度范围为10～200μg/L、SeMet浓度范围为50～200μg/L时,各形态均可得到良好的线性关系,线性相关系数均大于0.9992。用建立的方法测定了富硒营养品中的As和Se形态,加标回收率在91%～115%之间。     

Study of the stability of selenium compounds in human urine and determination by mixed ion-pair reversed-phase chromatography with ICP-MS detection

The stability of five selenium compounds, selenate, Se(VI), selenourea, SeUr, trimethylselenonium ion, TMSe(+), selenomethionine, SeMet, and selenoethionine, SeEt, at concentrations from 30-60 micro g L(-1) in a pooled human urine, stored in dark at -20 degrees C, 4 degrees C, or ambient temperature (ca. 25 degrees C), without addition of any stabilizing reagent was evaluated. The investigated Se species were determined independently by mixed ion-pair reversed-phase liquid chromatography with inductively coupled plasma mass spectrometric (ICP-MS) detection. The general trend is the lower the temperature used for storage, the higher the stability of Se species, when other conditions such as light, acidity, and container material are kept constant. On the basis of these results it is considered that the storage of urine samples at -20 degrees C for a short-term (within one month) is safe for Se speciation analysis. Long-term storage of urine samples for speciation analysis should, however, be undertaken with caution.     

类石墨烯C3N4纳米片光催化分解水制氢中的量子限域效应

从层状化合物获得的纳米片是一类新型纳米结构材料,这种二维各向异性的纳米甚至亚纳米级的材料具有独特的物理化学性能,其中最好的一个例证就是从石墨烯C₃N₄到石墨烯C₃N₄纳米片的转变。通过高温氧化热刻蚀方法将体相g-C₃N₄剥离成g-C₃N₄纳米片,应用于染料敏化可见光分解水产氢,表现出了较体相g-C₃N₄高于2.6倍的产氢速率。通过X射线衍射（XRD）、傅里叶变换红外（FTIR）光谱、扫描电子显微镜（SEM）、Brunauer-Emmett-Teller（BET）、荧光光谱和光电化学等表征研究了g-C₃N₄纳米片的结构及曙红（EY）和g-C₃N₄纳米片之间的电子迁移过程。热剥离后的g-C₃N₄纳米片具有较高的比表面积,不仅可以更为有效地吸附染料分子,还因其量子限域效应大大增强了光生电荷的分离效率和电子转移效率,改善了电子沿平面方向的传输能力以及光生载流子的寿命,从而显著提高g-C₃N₄纳米片的光催化产氢活性。     

高活性氮化碳纳米片的制备策略

Layered graphitic carbon nitride (g-C₃N₄) is a typical polymeric semiconductor with an sp² π-conjugated system having great potential in energy conversion, environmental purification, materials science, etc., owing to its unique physicochemical and electrical properties. However, bulk g-C₃N₄ obtained by calcination suffers from a low specific surface area, rapid charge carrier recombination, and poor dispersion in aqueous solutions, which limit its practical applications. Controlling the size of g-C₃N₄ (e.g., preparing g-C₃N₄ nanosheets) can effectively solve the above problems. Compared with the bulk material, g-C₃N₄ nanosheets have a larger specific surface area, richer active sites, and a larger band gap due to the quantum confinement effect. As g-C₃N₄ has a layered structure with strong in-plane C-N covalent bonds and weak van der Waals forces between the layers, g-C₃N₄ nanosheets can be prepared by exfoliating bulk g-C₃N₄. Alternatively, g-C₃N₄ nanosheets can otherwise be obtained through the anisotropic assembly of organic precursors. Nevertheless, some of these methods have various limitations, such as high energy consumption, are time consuming, and have low yield. Accordingly, developing green and cost-effective exfoliation and preparation strategies for g-C₃N₄ nanosheets is necessary. Herein, the research progress of the exfoliation and preparation strategies (including the thermal oxidation etching process, the ultrasound-assisted route, the chemical exfoliation, the mechanical method, and the template method) for two-dimensional C₃N₄ nanosheets are introduced. Their features are systematically analyzed and the perspectives and challenges in the preparation of g-C₃N₄ nanosheets are discussed. This study emphasizes the following: (1) The preparation method of g-C₃N₄ nanosheets should be properly selected according to the practical application needs. Additionally, various strategies (such as chemical method and ultrasonic method) can be combined to exfoliate nanosheets from bulk g-C₃N₄; (2) More reasonable nano- or even subnanostructured g-C₃N₄ nanosheets should be continuously explored; (3) Novel modification strategies, such as defective engineering, heterojunction construction, and surface functional group regulation, should be introduced to improve the reactivity and selectivity of the g-C₃N₄ nanosheets; (4) The application of in situ characterization techniques (such as in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), electron spin resonance (ESR) spectroscopy, and Raman spectroscopy) should also be strengthened to monitor the detailed catalytic process and investigate the g-C₃N₄ nanosheet structure-efficiency relationship. (5) To gain a deeper understanding of the relationship between the macroscopic properties and the microscopic structure, the combination of theoretical calculations and experimental results should be strengthened, which will be beneficial for exploiting high-quality g-C₃N₄ nanosheets.      

Ni,Co基硒化物修饰g-C3N4光催化产氢研究

Developing novel and efficient catalysts is a significant way to break the bottleneck of low separation and transfer efficiency of charge carriers in pristine photocatalysts. Here, two fresh photocatalysts, g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ hybrids, are first synthesized by anchoring Ni₃Se₄ and CoSe₂ nanoparticles on the surface of well-dispersed g-C₃N₄ nanosheets. The resulting materials show excellent performance for photocatalytic in situ hydrogen generation. Pristine g-C₃N₄ has poor photocatalytic hydrogen evolution activity (about 1.9 μmol·h^-1) because of the rapid recombination of electron-hole pairs. However, the hydrogen generation activity is well improved after growing Ni₃Se₄ and CoSe₂ on the surface of g-C₃N₄, owing to the unique effect of these selenides in accelerating the separation and migration of charge carriers. The hydrogen production activities of G-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ are about 16.4 μmol·h^-1 and 25.6 μmol·h^-1, which are 8-fold and 13-fold that of pristine g-C₃N₄, respectively. In detail, coupling Ni₃Se₄ and CoSe₂ with g-C₃N₄ greatly improves the light absorbance density and extends the light response region. The photoluminescence intensity of the photoexcited Eosin Y dye in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is weaker than that in the presence of pure g-C₃N₄. On the other hand, the upper limit of the electron-transfer rate constants in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is greater than that in the presence of pure g-C₃N₄. Among the g-C₃N₄@Ni₃Se₄@FTO, g-C₃N₄@CoSe₂@FTO, and g-C₃N₄@FTO electrodes, the g-C₃N₄@FTO electrode has the lowest photocurrent density and the highest electrochemical impedance, implying that the introduction of CoSe₂ and Ni₃Se₄ onto the surface of g-C₃N₄ enhances the separation and transfer efficiency of photogenerated charge carriers. In other words, the formation of two star metals selenide based on g-C₃N₄ can efficiently inhibit the recombination of photogenerated charge carriers and accelerate photocatalytic water splitting to generate H₂. Meanwhile, the right shift of the absorption band edge effectively reduces the transition threshold of the photoexcited electrons from the valence band to the conduction band. In addition, the more negative zeta potential for the g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ catalysts as compared with that for pure g-C₃N₄ leads to a notable enhancement in the adsorption of protons by the sample surface. Moreover, the results of density functional theory calculations indicate that the hydrogen adsorption energy of the N sites in g-C₃N₄ is -0.22 eV; further, the hydrogen atoms are preferentially adsorbed at the bridge site of two selenium atoms to form a Se―H―Se bond, and the adsorption energy is 1.53 eV. In-depth characterization has been carried out by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, transient photocurrent measurements, and Fourier transform infrared spectroscopy; the results of these experiments are in good agreement with one another.     

反蛋白石结构的g-C3N4可控合成及其优异的光催化产氢性能

The growing frustration from facing energy shortages and unbalanced environmental issues has obstructed the long-term development of human society. Semiconductor-based photocatalysis, such as water splitting, transfers solar energy to storable chemical energy and is widely considered an economic and clean solution. Although regarded as a promising photocatalyst, the low specific surface area of g-C₃N₄ crucially restrains its photocatalytic performance. The macro-mesoporous architecture provides effective channels for mass transfer and full-light utilization and improved the efficiency of the photocatalytic reaction. Herein, g-C₃N₄ with an inverse opal (IO) structure was rationally fabricated using a well-packed SiO₂ template, which displayed an ultrahigh surface area (450.2 m²·g^-1) and exhibited a higher photocatalytic H₂ evolution rate (21.22 μmol·h^-1), almost six times higher than that of bulk g-C₃N₄ (3.65 μmol·h^-1). The IO g-C₃N₄ demonstrates better light absorption capacity than bulk g-C₃N₄, primarily in the visible spectra range, owing to the multiple light scattering effect of the three-dimensional (3D) porous structure. Meanwhile, a lower PL intensity, longer emission lifetime, smaller Nyquist semicircle, and stronger photocurrent response (which synergistically give rise to the suppressed recombination of charge carriers) decrease the interfacial charge transfer resistance and boost the formation of photogenerated electron-hole pairs. Moreover, the existing N vacancies intensify the local electron density, helping increase the number of photoexcitons. The N₂ adsorption-desorption test revealed the existence of ample mesopores and macropores and high specific surface area in IO g-C₃N₄, which exposes more active edges and catalytic sites. Optical behavior, electron paramagnetic resonance, and electrochemical characterization results revealed positive factors, including enhanced light utilization, improved photogenerated charge separation, prolonged lifetime, and fortified IO g-C₃N₄ with excellent photocatalytic performance. This work provides an important contribution to the structural design and property modulation of photocatalysts.      

石墨相氮化碳负载磷钨酸杂化材料的制备及其氧化脱硫催化性能

以1-丁基-3-甲基咪唑溴离子液体([Bmim]Br)、磷钨酸(H_3PW_(12)O_(40))和g-C_3N_4为原料,采用原位沉淀法合成了负载型[Bmim]_3PW_(12)O_(40)/g-C_3N_4催化剂(BPWO/g-C_3N_4)。通过XRD、FT-IR、UV-vis、氮气吸附、TEM和XPS等手段对催化剂的形貌和结构进行了表征,并以二苯并噻吩(DBT)的正庚烷溶液为模拟油、过氧化氢为氧化剂,考察了各组分负载量、催化剂用量、氧/硫物质的量比(O/S)和反应温度变量等对其氧化脱硫效果的影响。结果表明,BPWO/g-C_3N_4具有Keggin型杂多阴离子结构特征,BPWO (20%)/g-C_3N_4催化剂具有最优的对DBT的氧化脱硫性能,在50℃、O/S物质的量比为6.0的条件下反应180 min,可以完全氧化浓度为800μg/g的含DBT模拟油。同时,该BPWO/g-C_3N_4催化剂具有良好的重复使用性能,循环使用八次后其对DBT的氧化活性没有明显降低。     

Speciation of selenium compounds with ion-pair reversed-phase liquid chromatography using inductively coupled plasma mass spectrometry as element-specific detection

For selenium speciation analysis, the hyphenation of chromatographic separation with element-specific detection has proved a useful technique. A powerful separation system, which is capable of resolving several biologically and environmentally important selenium compounds in a single column, is greatly needed. However, that has been difficult to achieve. In this paper eight selenium compounds, namely, selenite [Se(IV)], selenate [Se(VI)], selenocystine (SeCys), selenourea (SeUr), selenomethionine (SeMet), selenoethionine (SeEt), selenocystamine (SeCM) and trimethylselenonium ion (TMSe+), were separated by using mixed ion-pair reagents containing 2.5 mM sodium 1-butanesulfonate and 8 mM tetramethylammonium hydroxide as a mobile phase. The separation of these anionic, cationic and neutral organic selenium compounds on a LiChrosorb RP18 reversed-phase column took only 18 min at a flow-rate of 1.0 ml/min with isocratic elution, and baseline separation among the six organic Se compounds was achieved. Inductively coupled plasma mass spectrometry (ICP-MS) was employed as element-specific detection. A comparison of ICP-MS signal intensity obtained with a Barbington-type nebulizer and with an ultrasonic nebulizer (USN) was made. Different signal enhancement factors were observed for the various selenium compounds when a USN was used. The speciation technique was successfully applied to the study on chemical forms of selenium in a selenium nutritional supplement. Selenomethionine was found to be the predominant constituent of selenium in the supplement.     

Ni2P-NiS双助剂促进g-C3N4光催化产氢动力学

本文通过简单的一步水热法得到Ni₂P-NiS双助催化剂,之后采用溶剂蒸发法将Ni₂P-NiS与g-C₃N₄纳米片结合构建获得无贵金属的Ni₂P-NiS/g-C₃N₄异质结。研究结果表明,优化后的复合材料具有良好的光催化产氢活性,其产氢速率最高可到6892.7 μmol·g^-1·h^-1,分别为g-C₃N₄ (150 μmol·g^-1·h^-1)、15%NiS/g-C₃N₄ (914.5 μmol·g^-1·h^-1)和15%Ni₂P/g-C₃N₄ (1565.9 μmol·g^-1·h^-1)的46.1、7.5和4.4倍。这主要归因于Ni₂P-NiS相比Ni₂P和NiS单体具有更好的载流子转移能力,其与g-C₃N₄形成的肖特基势垒能有效促进光生载流子在二者界面上的分离,同时Ni₂P-NiS能进一步降低析氢过电势,进而显著增强了表面析氢反应动力学。本研究为开发稳定、高效的非贵金属产氢助剂提供了实验基础。