A novel analytical approach for the simultaneous measurement of nitrate and dissolved organic carbon in soil water

In this paper, we present a novel approach, enabling the measurement of nitrate concentrations in natural soil porewater containing natural soil dissolved organic carbon (DOC). The method is based on UV absorbance spectroscopy, combined with fluorescence spectroscopy, for simultaneous analysis of DOC and nitrate concentrations. The analytical procedure involves deduction of the absorption caused by the DOC from the total absorbance in the UV range that is attributed to both DOC and nitrate in the water solution. The analytical concept has been successfully tested in soil water samples obtained from five agricultural sites, as well as in water samples obtained from a commercial humus soil mixture. We believe that the new analytical concept can provide a scientific foundation for developing a sensor for real-time nitrate concentration measurements in agricultural soils. As such, it can play a significant role in reducing nitrate pollution in water resources, optimizing input application in agriculture, and decreasing food production costs.

Sulpiride Serves, a Substrate for the Gut Microbiome

In the contemporary research world, the intestinal microbiome is now envisioned as a new body organ. Recently, the gut microbiome represents a new drug target in the gut, since various orthologues of intestinal drug transporters are also found present in the microbiome that lines the small intestine of the host. Owing to this, absorbance of sulpiride by the gut microbiome in an in vivo albino rats model was assessed after the oral administration with a single dose of 20mg/kg b.w. The rats were subsequently sacrificed at 2, 3, 4, 5 and 6 hours post oral administration to collect the gut microbial mass pellet. The drug absorbance by the gut microbiome was determined by pursuing the microbial lysate through RP-HPLC-UV. Total absorbance of sulpiride by the whole gut microbiome and drug absorbance per milligram of microbial pellet were found significantly higher at 4 hours post-administration as compared to all other groups. These results affirm the hypothesis that the structural homology between membrane transporters of the gut microbiome and intestinal epithelium of the host might play an important role in drug absorbance by gut microbes in an in vivo condition.

First-order Kinetics in the Study of Enzymes: Applications to the Reporter Substrate Method and to the Estimation of kcat/Km

: The study of the interactions between enzymes and inactivators can often be performed with the help of the reporter substrate method in which the time-dependent decrease of the rate of substrate disappearance (or product formation) is monitored. In the present contribution, we wish to describe examples of the utilization of this rapid and efficient method for reactions whose rates can be monitored by spectrophotometric or fluorimetric measurements. After the collection of the data in an Excel file, a very simple program can be applied to extract the values of pseudo-- first-order rate constants. The inactivation can be complete or result in a steady-state if the inactivated adduct is not totally stable or if the inactivation reaction is reversible. Similarly, the method can be used in the cases of so-called “slow binding” inhibitors. The same type of analysis allows the easy determination of kcat/Km values for substrates for which the Km value is rather low. We show that this very rapid method (less than 5 min) yields very good values of the desired kinetic parameter even if the total absorbance variations are very low (0.1 or less). : In conclusion, the described experimental approach is particularly useful when applied to the reporter substrate method but it also allows the estimation of the kcat/Km parameter even if the Km value is rather low. : The authors wish to dedicate this paper to the memory of the late Michel Rinné (1941-2009) whose contribution to making the data analysis program very user-friendly was invaluable.

A novel analytical approach for the simultaneous measurement of nitrate and DOC in soil water

In this paper, we present a novel approach, enabling the measurement of nitrate concentrations in natural soil porewater containing natural soil dissolved organic carbon (DOC). The method is based on UV absorbance spectroscopy, combined with fluorescence spectroscopy, for simultaneous analysis of DOC and nitrate concentrations. The analytical procedure involves deduction of the absorption caused by the DOC from the total absorbance in the UV range that is attributed to both DOC and nitrate in the water solution. The analytical concept has been successfully tested in soil water samples obtained from five agricultural sites, as well as in water samples obtained from a commercial hummus soil mixture. We believe that the new analytical concept can provide a scientific foundation for developing a sensor for real-time nitrate concentration measurements in agricultural soils. As such, it can play a significant role in reducing nitrate pollution in water resources, optimizing input application in agriculture, and decreasing food production costs.

Investigations of Feldspar-Quartz Raw Materials After Firing: Effect of Various Na2O/K2O Ratio and Synthetic Pigments Addition

Different techniques (chemical analysis, X-ray diffraction, Mössbauer spectroscopy, UV-Vis-NIR spectrophotometry and chromaticity measurements) were used to study the color variation of feldspathic raw materials after firing at 1200 °C. Two varieties of feldspar-quartz grits (with Na2O or K2O prevalence) doped with synthetic pigments (hematite and rutile) were heat-treated in an oxidizing atmosphere. The results obtained indicate that the color of the ceramic body after firing may not only depend on the presence and analytical content of coloring elements (such as iron and titanium), but on their valence state and the chemical characteristics of the melt itself. The prevalence of larger alkali K+ ions over Na+ ions may cause the reduction of the coordination number of iron. This has a significant effect on the length of the Fe–O bond, which in turn influences the capacity for light absorption of a specific wavelength. The results of spectrophotometric measurements showed pronounced disparity between the raw materials and samples doped with coloring oxides. The introduction of synthetic pigments caused clear changes in the spectral dependence of the total absorbance. The absorbance increased in the whole measuring range, in particular in the visible part of the spectrum. Furthermore, a red-shift of the absorption bands towards longer wavelengths attributed to oxygen-metal charge transfer (OMCT) interactions between Fe3+ and O2− ions as well as to d-d transitions within Fe3+ ions was observed.

Nucleation of Gold Nanoparticles in a Solution via Laser Hell: Simulation and Experiments

Theoretical and experimental results on the formation of gold nanoparticles under the influence of pulsed nanosecond laser irradiation of aqueous AuCl[Formula: see text] solution are presented. It is shown that high monodispersity of nanoparticles ensemble is related to the strong dependence of total absorbance of laser radiation on nanoparticles diameter and the conductive heat transfer to surrounding medium.

Effect of Infant Formula on Streptococcus Mutans Biofilm Formation

Objective: This study investigated the effect that infant formula had on biofilm growth of Streptococcus mutans. Specifically, it compared biofilm growth in media containing lactose-based and sucrose-based formulas. It also analyzed biofilm formation with formulas of varying iron content. Biofilm growth was tested with the specific infant formula components sucrose, lactose, and ferric chloride. The study was designed to determine if these types of infant formulas and components affected S. mutans biofilm formation differently. Study design: A 24-hour culture of S. mutans was treated with various concentrations of infant formula diluted in bacteriological media. To test for biofilm formation, S. mutans was cultured with and without the infant formula and formula components. The biofilms were washed, fixed, and stained with crystal violet. The absorbance was measured to evaluate biofilm growth and total absorbance. Results: Sucrose-based formulas provided significant increases in biofilm growth when compared to lactose-based formulas at two dilutions (1:5, 1:20). Similac Sensitive RS (sucrose-based) at most dilutions provided the most significant increase in biofilm growth when compared to the control. Sucrose tested as an individual component provided more of a significant increase on biofilm growth than lactose or iron when compared to the control. A low iron formula provided a significant increase in biofilm growth at one dilution (1:5) when compared to formula containing a normal iron content. There was no significant difference in biofilm growth when comparing high iron formula to normal iron formula or low iron formula. There was no significant difference when comparing Similac PM 60/40 (low iron formula) to Similac PM 60/40 with additional ferric chloride. Conclusion :The results of this study demonstrated that sucrose-based formula provided more of a significant increase in biofilm growth compared to lactose-based formula. Sucrose alone provided a significant increase of biofilm growth at more dilutions when compared to the control than lactose and iron. The amount of iron in formula had a significant effect on biofilm formation only when comparing low iron formula to normal iron formula at the highest concentration (1:5). There was no significant difference in biofilm growth when iron was added to the low iron formula. The information obtained expands current knowledge regarding the influence of infant formula on the primary dentition and reinforces the importance of oral hygiene habits once the first tooth erupts.

Optimization of Simultaneous Analysis of Cefixime and Dicloxacillin Sodium in Oral Tablets

The present manuscript describes simple, sensitive, rapid, accurate, precise and economical spectrophotometric method for the simultaneous determination of cefixime and dicloxacillin sodium in their combined tablet dosage form. The method was based on additive property of absorbance and correction of absorbance for the analysis of two drugs using methanol as solvent. The two wavelengths were selected from the UV spectra of both the drugs, which 218.4 nm and 289 nm. Cefixime was determined directly at 289 nm (λmax of cefixime) without any interference of dicloxacillin sodium in binary mixture. At 218.4 nm, both drugs have reasonable absorbance. So to remove interference of cefixime, its absorbance was calculated by using its standard absorptivity values at this wavelength. Finally, corrected absorbance of dicloxacillin sodium at 218.4 nm was found by subtracting the absorbance of cefixime from the total absorbance at 218.4 nm. The linearity was found in the concentration range of 3-16 μg/ml for both the drugs. The % recovery was found in the range of 100.22 ± 0.43 and 100.46 ± 0.32 for cefixime and dicloxacillin sodium respectively. The intermediate precision data obtained under different experimental setup, the calculated value of % coefficient of variation (% CV) was found to be less than critical value. The method was successfully applied for the simultaneous determination of these two drugs from their combined tablet dosage form without any interference.

Combined Determination of Phosphorus and Arsenic in Molybdenum Concentrate by Molybdenum Blue Spectrophotometric Method

This paper determined the total absorbance of phosphorus molybdenum blue and arsenic molybdenum blue by using the additive property of their absorbance values. By eliminating the interference of arsenic by reduction masking with composite reducing agent Na2SO3-Na2S2O3-KBr, the absorbance of phosphorus could be obtained. Thus, the content of phosphorus and arsenic could be calculated, respectively. The results show that the work curves of this method for phosphorus and arsenic are consistent with Beer’s law when the content of phosphorus and arsenic is 0-0.60ug/mL and 0-2.00ug/mL, respectively. The standard addition recovery rate of phosphorus and arsenic is 98.80%-101.04% and 99.00%-101.50%, respectively. The relative standard deviation of phosphorus and arsenic is less than 4.0% with good accuracy and precision. This method is simple and fast to determine phosphorus and arsenic in molybdenum concentrate, and the results are accurate and reliable.

Effects of Hydrothermal Dewatering on Kinetics and Mechanism of Brown Coals Pyrolysis

Two brown coals from China were dewatered under hydrothermal dewatering (HTD) conditions at 250–320 °C for 1 h in a 2 L autoclave. The HTD products and brown raw coals were pyrolyzed in a thermogravimetry analyzer at heat rate of 15°C/min from ambient temperature to 800°C. And the gas products were measured by Fourier Transform Infrared Spectrometer. Besides, The Coast-Redfern model was employed to analyze the effects of HTD on kinetics during coal pyrolysis process. The results showed that the initial temperatures of each pyrolysis stage of HTD products were higher than that of raw coals. The temperatures at which methane appears during pyrolysis process increased and the total absorbance intensity of CH4 was weakened as increasing HTD temperature. Moreover, the activity energy also increased as increasing HTD temperature. It meant that thermal stability of brown coals was improved during HTD process.