Formation Of MX Research Articles

2D MXene/graphene nanocomposite preparation and its electrochemical performance towards the identification of nicotine level in human saliva

The quantitative analysis of neurological drugs is critical since the kinetics of body fluids is strongly dependent on the dosage of the drug levels. Thus, the study of neurological medicines is significant because of the major diseases connected to it, for instance, Alzheimer's and Parkinson's diseases. Herein, a 2D hybrid MXene/graphene (MX/Gr) film was synthesized through a top-down approach and utilized to prepare an electrochemical transducer for the electrochemical sensing of nicotine. The X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) confirmed the successful incorporation of MX with Gr sheets. The high-resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (TEM) have been used to confirm the formation of MX, graphene sheets and the MX/Gr hybrid film. Furthermore, the MX/Gr hybrid film composite modified glassy carbon electrode (GCE) was prepared to selectively detect the nicotine in phosphate buffer medium (0.1 M PBS, pH~7.4). Under the optimized condition, the MX/Gr/GCE based sensor provided a linear response against nicotine from 1 to 55 µM and 30 nM – 600 nM with the lowest limit of detections (LOD) of 290 nM and 0.28 nM by differential pulse voltammetry (DPV) and amperometry, respectively. This newly developed MX/Gr hybrid film modified electrode displayed a remarkable selectivity, sensitivity, and reproducibility for accurate detection of nicotine. Finally, this new sensor was applied to detect nicotine in human/artificial saliva samples with high accuracy.

Effect of Ta and Ti on Modified Reduced Activation Ferritic/Martensitic Steels with a Thermo‐mechanical Control Process

Modified reduced activation ferritic/martensitic steels with different amounts of Ta and Ti are fabricated with a thermo‐mechanical control process (TMCP). TMCP greatly enhances the refinement of both the precipitates and the martensite matrix. In addition, an increase in the dislocation density is achieved. The modified steels show excellent comprehensive mechanical properties compared with traditional reduced activation ferritic/martensitic steels. In addition, under the conditions of the TMCP, the effects of Ta and Ti on the microstructure and properties are analyzed. Simply increasing the amounts of Ta and Ti does not increase the phase fraction of MX, which is quite different from that derived from equilibrium thermodynamics theory or the typical hot rolling process for traditional reduced activation ferritic/martensitic steels. Without a high enough nucleation rate for MX, the excess Ta and Ti, which are not consumed by the formation of MX, promotes the formation of proeutectoid ferrite. This decreases the impact on toughness significantly. Herein, preliminary guidance is offered for a comprehensive design with a combination of both composition and rolling processing modification for the production of reduced activation ferritic/martensitic steels.

Atomic scale identification of nano-sized precipitates of Ta/Ti-added RAFM steel and its superior creep strength

The influence of 0.015 wt% Ti addition on the formation of MX precipitates and the creep resistances of a reduced activation ferritic/martensitic (RAFM) steel has been studied. 0.1 wt% Ta was also added as same as conventional RAFM steels. Transmission electron micrographs taken from extraction replicas indicated that the area fraction of MX particles in Ta/Ti-added RAFM steel was 2.3 times higher than that in the reference steel. Atom probe tomography was employed to identify the types of MX precipitates and their interactive distribution. By using isoconcentration surfaces with different elemental concentration values, it was newly found that there are three types of MX precipitates, i.e. (Ta,V)-rich MX, Ti-rich MX and W-rich MX in the Ta/Ti-added RAFM steel. They appeared to be distributed independently in the matrix. However, in some cases, smaller sized (Ti or W)-rich MX particles were in contact with large (Ta,V)-rich MX particle. The creep rupture life of the Ta/Ti-added RAFM steel was significantly improved, as compared with the reference steel. The enhanced creep resistance can be rationalized in terms of a high density of dislocations, which were produced by a strong interaction with a higher fraction of the nano-sized MX particles within laths.

Study of radiation-induced amorphization of M23C6 in RAFM steels under iron irradiations

The mechanical properties of reduced activation ferritic/martensitic steels (RAFMs) such as creep, thermal aging, and irradiation resistance are improved by the formation of MX and M23C6 particles. However, it is well known that these particles are unstable under irradiation. The purpose of the present study is to clarify the details of the radiation-induced amorphization (RIA) of M23C6 in F82H steels. The instability behavior of M23C6 under a wide range of irradiation temperatures from R.T. to 773 K and various ion beam energies (2.8, 3.7, 6.4 and 10.5 MeV) was systematically investigated. Two types of materials, F82H and its model alloy (F8), were utilized in this study. TEM observation and selected area electron diffraction analysis before and after irradiation were conducted to evaluate the occurrence of RIA, and the chemical composition was analyzed to reveal the possible relation between atom displacement/diffusion and RIA. In the case of the iron irradiation at the temperature below 598 K, a bilayer contrast of the particle, consisting of an amorphous-rim phase and inner crystalline core, was observed. Similar particle survived in the irradiated F82H at the temperature of 623 K, the RIA was not observed in the F8 specimen. Consequently, the critical temperature of RIA was estimated as 623–673 K. Since the melting temperature (Tm) of M23C6 is approximately 2173 K, the critical temperature corresponds to ∼0.29 Tm. From the STEM-EDS analysis, the Fe/Cr ratio of the particle decreased with increasing irradiation temperature in the range of 573–623 K. This behavior was qualitatively explained by the formation of the amorphous phase. It is clarified that the occurrence of the RIA of M23C6 particle can be evaluated by the variation of Fe/Cr ratio.

Investigation of the effective factors on the mutagen X formation in drinking water by response surface methodology

Mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is known as a potent factor in inducing DNA damage and increasing cancer risk. MX is a chlorination disinfection byproduct that comes from the reaction of humic acids and chlorine in drinking water. The purpose of this study was to evaluate the effects of significant factors (including pH, reaction time, chlorine and the concentration of organic materials (TOC)) and their interactions on the MX formation rate in chlorinated drinking water using Box-Behnken Design (BBD) and response surface method (RSM). For this purpose, the simulation of water chlorination disinfection process was carried out in a laboratory scale. A quadratic model was chosen to determine the mathematical relations between the response and the effective factors. All linear parameters, as well as second-degree components except chlorine, were statistically significant. Also, the interactions of contact time with TOC, free chlorine residual with TOC, and chlorine with pH were also statistically significant. Statistical results showed that the pH had a great effect on the potential of MX formation, and then the factors of TOC, chlorine and contact time were effective, respectively. The percentage of contribution (PC) of each component in the formation of MX. The highest significant percentage of contribution (48.36%) was allocated to the pH. Under the optimum conditions (contact time of 48.38 min, chlorine concentration of 0.79 mg/L, TOC concentration of 0.53 mg/L, and pH of 7.98), minimum value of MX was equal to 28.6.

An investigation into some important properties of transition metals (densities, resistivities, coefficients of expansion and enthalpies of formation of Mx+ ions)

This paper briefly reviews the current “ions in a sea of electrons” model of metallic structure. Limitations of the model are stated. Properties not explained by the model are accounted for by an alternative model. Simple equations derived from this model can calculate the densities, resistivities, enthalpies of the Mx+ ions and coefficients of expansion of transition metals showing good agreement with experimental values. The alternative model is used to account for the ferro-magnetic properties of iron, cobalt and nickel and demonstrate why other transition metals are not magnetic but some lanthanides are magnetic.

Elucidating the Mechanism of Tofacitinib Oxidative Decyanation.

Tofacitinib is known to generate two metabolites M2 (alcohol) and M4 (acid), which are formed as the result of oxidation and loss of the nitrile [1]. Systematic in vitro investigation into generation of M2 and M4 from tofacitinib. In vitro using human liver microsomes, we found a new geminal diol metabolite of tofacitinib (MX) that lost the nitrile. MX was further reduced or oxidized to M2 (alcohol) and M4 (acid), respectively by enzymes such as aldo-keto reductase 1C1, aldehyde oxidase and possibly CYP3A4. Stable label studies using H2 18O and D2O suggested the source of oxygen was from water in the media. This was due to rapid water exchange with MX in the media prior to reduction to M2. In case of deuterium, one was incorporated in M2 and this was mainly as a result of tofacitinib rapid exchange of two deuterium atoms from D2O onto methylene position. After formation of MX, there was one deuterium that no longer exchanged with water and therefore retained in M2 for further reduction. The proposed mechanism involved the initial oxidation by P450 at the α-carbon to the nitrile group generating an unstable cyanohydrin intermediate; followed by the loss of the nitrile group to form a new geminal diol metabolite (MX).

Bromide affecting drinking water mutagenicity

The effect of bromide on the mutagenicity of artificially recharged groundwater and purified artificially recharged groundwater after chlorine, ozone, hydrogen peroxide, permanganate, and UV treatments alone and in various combinations was studied. The highest mutagenicity was observed after chlorination, while hydrogen peroxide–ozone–chlorine treatment produced the lowest value for both waters. Chlorinated waters, which were spiked with bromide, had up to 3.7 times more mutagenic activity than waters without bromide after every preoxidation method. 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5 H)-furanone (MX) was found to correspond as much as 76% of the overall mutagenicity in the waters not spiked with bromide. MX formation was found to be lower when the treated water contained bromide, implicating the formation of brominated MX analogues. Trihalomethane formation increased when the treated water contained bromide.

A possible new disinfection by-product—2-chloro-5-oxo-3-hexene diacyl chloride (COHC)—in formation of MX by chlorinating model compounds

MX was widely considered as one of the most important disinfection by-products (DPBs) and as the strong carcinogen in the chlorinated drinking water. Some model compounds which have been classified into four families were chlorinated at laboratory conditions. MX was produced only in the chlorinated substituted aromatic aldehydes and amino acids, while a possible new compound (COHC) was found in some substituted aromatic aldehydes, chlorinated substituted aromatic acids and phenols. Through the analysis of the peaks presented in mass spectrum, the composition and structure of the new compound are proposed as 2-chloro-5-oxo-3-hexene diacyl chloride (COHC) which could cause interference in the detection of MX. COHC has also been found in drinking water and extracted chlorinated fulvic acid solution from the sediment and water of Tai Lake, so it should bring about more attention.

Reply to the paper “Comment on paper ‘A possible new disinfection by-product—(COHC)—in formation of MX by chlorinating model compounds’”

Reply to the paper “Comment on paper ‘A possible new disinfection by-product—(COHC)—in formation of MX by chlorinating model compounds’”

A possible new disinfection by-product—2-chloro-5-oxo-3-hexene diacyl chloride (COHC)—in formation of MX by chlorinating model compounds

MX was widely considered as one of the most important disinfection by-products (DPBs) and as the strong carcinogen in the chlorinated drinking water. Some model compounds which have been classified into four families were chlorinated at laboratory conditions. MX was produced only in the chlorinated substituted aromatic aldehydes and amino acids, while a possible new compound (COHC) was found in some substituted aromatic aldehydes, chlorinated substituted aromatic acids and phenols. Through the analysis of the peaks presented in mass spectrum, the composition and structure of the new compound are proposed as 2-chloro-5-oxo-3-hexene diacyl chloride (COHC) which could cause interference in the detection of MX. COHC has also been found in drinking water and extracted chlorinated fulvic acid solution from the sediment and water of Tai Lake, so it should bring about more attention.

The interference of 2-chloro-5-oxo-3-hexene diacyl chloride (COHC) in the detection of strong mutagen MX

The MX formation potential of some compounds belong to benzoic acids, benzoic aldehydes and phenols families was investigated. Only some structures with aldehyde group can form MX, which is inconsistent with other research. A new compound 2-chloro-5-oxo-3-hexene diacyl chloride (COHC) was found. It will seriously interfere with the detection of MX when the GC/MS instrument is operated in select ion monitoring mode because its retention time is very close to that of methylated MX and it has a set of characteristic ions m/ z 199, 201, 203, which is widely used in the detection of MX. The detection of COHC has not been reported previously. However, according to its formation mechanism it will widely occur in chlorinated drinking and humic water. Due to the presence of COHC, some of the former research results on MX should be revised.

Factors on the formation of disinfection by-products MX, DCA and TCA by chlorination of fulvic acid from lake sediments

[3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] (MX) and chlorinated acetic acids such as dichlorinated acetic acid (DCA) and trichlorinated acetic acid (TCA) have always been the focus of disinfection by-products (DBPs) studies. In order to find out the influences of reaction time, TOC, chlorine dose, pH and temperature on the formation of MX, DCA and TCA, we extracted fulvic acid (FA) from the sediment of Tai Lake, and conducted simulated chlorination of samples rich in FA. Results showed positive relationship between TOC and the yields of MX, DCA and TCA. But the influences of pH, chlorine dose, reaction time, and temperature are quite complex. The optimal chlorination condition for the formation of MX is pH=2, T=45°C, C/ Cl 2=1/4,t = 12 h. Lower pH, longer time, greater chlorine dose can result in greater yield of both DCA and TCA, and there is a strong linear relationship between the formation of DCA and TCA.

Factors on the formation of strong mutagen [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] MX by chlorination of syringaldehyde

Syringaldehyde (4-hydroxy-3,5-dimethoxybenzaldehyde) was chlorinated in the laboratory at different reaction time, temperature, pH and chlorine dose, and MX was determined and quantified by GC/MS. The finding suggests that the optimal chlorination conditions are as follows: temperature=298 K, pH=5, Cl:syrin. (mol:mol)=9:1. We also found that the formation of MX increased with the syringaldehyde concentration in a linear relationship. In addition, when syringaldehyde was chlorinated with a different chlorine dose in an alkaline condition, no MX was detected. This study will conduce to elucidating the kinetic process for the formation of MX from syringaldehyde and will be of great help for better control of MX in drinking water.

Screening the precursors of strong mutagen [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5 H)-furanone] MX from chlorinated water

In this study, 21 suspected precursors of MX were chlorinated in laboratory condition. Only 8 of selected compounds syringaldehyde, acetosyringone, ferulic acid, 3-ethoxy-4-hydroxy-benzaldehyde, 3,4,5-trimethoxy-benzaldehyde, vanillin, tryptophan, and tyrosine were screened as precursors of MX. The yields of MX by chlorination of syringaldehyde are the highest and decreased with chlorine dose, but the yields of MX by the other 7 compounds increased with chlorine dose. It may be possible to elucidate the reaction mechanism for the formation of MX in light of the reaction of these screened precursors with chlorine.

Studies on the precursors of strong mutagen [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone]MX by chlorination of fractions from different waters

The strong mutagen, [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] MX, was found to be one of the most potent mutagens in drinking water. In this study, dissolved organic matters from river water and lake water were separated into several compound classes by sorbtion on a series of resin absorbents. After chlorine treatment of the fractions, MX was determined with GC MS in the selected ion monitoring mode. Humic substances produced more MX on a TOC-basis than other fractions and contributed more to MX formation in the chlorinated natural waters. Some phenols were detected in the oxidation products of humic substances and therefore formation of MX may occur when some phenolic precursor structures in humic substances are treated with chlorine.

Formation of strong mutagen [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] MX by chlorination of fractions of lake water

Dissolved organic matter from lake water was separated into seven compound classes by sorbtion on a series of resin absorbents. About 81.3% of the dissolved organic carbons were recovered from the lake water sample. After chlorine treatment of the fractions [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone], MX was determined with GC MS in the selected ion monitoring mode. The fulvic acids, humic acids and hydrophobic neutrals produced more MX on a TOC-basis than the other fractions. There are much more fulvic acids in the water and therefore fulvic acids might contribute more to MX formation in the chlorinated natural water. After GC MS analysis some phenols that possibly produce MX by chlorination were detected in the oxidation products of humic substances.

Possible reaction pathways for the formation of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX)

Three compounds, 3,4,5-trimethoxybenzaldehyde ( i), 1-dichloromethyl-3,4,5-trimethoxy-benzene ( ii) and 3,4,5-trimethoxyphenylacetic acid ( iii) were treated with aqueous chlorine at pH 2. Aqueous chlorination of the three compounds increased the formation of MX (3-chloro-4-dichloromethyl-5(2H)-hydroxy-furanone) and e- MX ( e 2-chloro-3-dichloromethyl-4-oxo-butenoic acid) in the order i > ii > iii . By 1H-NMR spectroscopy and gas chromatography it was shown that ii hydrolizes readily to i in water. It is known that iii is converted to ii in chlorination reactions. We suggest that the (formed) aldehyde group remains intact during the formation of MX and e- MX from these three compounds. They could thus form MX and e- MX , via similar mechanisms. This suggested mechanism may also occur when phenolic precursor structures present in humic material are treated with chlorine in the process of drinking water production.

Formation of mutagenic organic by-products and AOX by chlorination of fractions of humic water

Dissolved organic matter from a lake was isolated and fractionated by sorbtion on an XAD-8 column and then separated into humic and fulvic acids. After chlorine treatment of the fractions 2-chloro-3-dichloromethyl-4-oxo-butenoic acid, MX, and three related compounds were determined by means of GC/MS in the selected ion monitoring mode. Mutagenicity was determined in the Ames test and adsorbable organic halogen (AOX) was determined by adsorption to activated carbon followed by neutron activation analysis. AOX formation per unit organic carbon was similar in the hydrophilic and hydrophobic fractions, but the hydrophobic fraction produced more mutagenic activity and MX than the hydrophilic one. The humic acid fraction produced slightly more mutagenicity and MX than the fulvic acid fraction per unit organic carbon. However, there are more fulvic acids than humic acids in natural waters and therefore fulvic acids contribute more to the mutagenicity and MX formation in chlorinated natural waters.

Occurrence of the mutagenic compound ‘MX’ in drinking water and its removal by activated carbon

Abstract Recent studies have shown that the compound MX [3‐chloro‐4‐(dichloromethyl)‐5‐hydroxy‐2(5H)‐furanone] can account for up to 57% of the observed acid fraction mutagenicity of chlorinated drinking water. In the present study laboratory investigations showed MX to be very well removed by activated carbon over a wide concentration range. Samples obtained from two water treatment plants following pre‐chlorination showed MX to be present in the range of 38 to 60 ng L−1. MX concentrations were not always correlated with TOC levels, suggesting that the type of organic matter present may play a role in MX formation. GAC appeared to be capable of removing MX precursors.