Non-aqueous Potentiometric Titration Research Articles

A Quick Method for the Determination of the Fraction of Freebase Nicotine in Electronic Cigarettes.

Recently, many electronic cigarettes (ECIGs) manufacturers have begun offering e-liquids, known as "nicotine salts". These salts that have started gaining big popularity among users can be formed by adding weak acid to e-liquid mixtures consisting of propylene glycol (PG), vegetable glycerin (VG), flavors, and nicotine. The latter can exist in two forms: monoprotonated (mp) and freebase (fb) based on the pH of the matrix. Over the years, the determination of the fraction of fb was found important to policymakers as the prevalence of this form in ECIGs has been associated with the harshness sensory of inhalable aerosols. Liquid-liquid extraction (LLE), 1H NMR, and Henderson-Hasselback have been developed to deduce the fraction of fb; however, these methods were found to be time-consuming and have shown some challenges mainly due to the presence of a non-aqueous matrix consisting of PG and VG. This paper presents a quick non-aqueous pH measurement-based method that allows a quick determination of the fraction fb by just measuring the pH and the dielectric constant of the e-liquid. Then, by inputting these values into an established mathematical relationship, the fraction fb can be deduced. The relationship between pH, dielectric constant, and fb relies on knowing the values of the acidity dissociation constants of nicotine, which were determined for the first time in various PG/VG mixtures using a non-aqueous potentiometric titration. To validate the proposed method, the fraction fb was determined for commercials and lab-made nicotine salts utilizing the pH and LLE methods. The variation between the two methods was (<8.0%) for commercial e-liquids and lab-made nicotine salts containing lactic acid and salicylic acid. A larger discrepancy of up to 22% was observed for lab-made nicotine salts containing benzoic acid, which can be attributed to the stronger affinity of benzoic acid to toluene in the LLE method.

The Effect of Sample Preparation Techniques on Lignin Fourier Transform Infrared Spectroscopy.

The characterization and quantification of functional groups in technical lignins are among the chief obstacles of the utilization of this highly abundant biopolymer. Although several techniques were developed for this purpose, there is still a need for quick, cost-efficient, and reliable quantification methods for lignin. In this paper, three sampling techniques for fourier transform infrared (FTIR) spectroscopy were assessed both qualitatively and quantitatively, delineating how these affected the resultant spectra. The attenuated total reflectance (ATR) of neat powders and DMSO-d6 solutions, as well as transmission FTIR using the KBr pelleting method (0.5 wt%), were investigated and compared for eight lignin samples. The ATR of neat lignins provided a quick and easy method, but the signal-to-noise ratios in the afforded spectra were limited. The ATR of the DMSO-d6 solutions was highly concentration dependent, but at a 30 wt%, acceptable signal-to-noise ratios were obtained, allowing for the lignins to be studied in the dissolved state. The KBr pelleting method gave a significant improvement in the smoothness and resolution of the resultant spectra compared to the ATR techniques. Subsequently, the content of phenolic OH groups was calculated from each FTIR mode, and the best correlation was seen between the transmission mode using KBr pellets and the ATR of the neat samples (R2 = 0.9995). Using the titration measurements, the total OH and the phenolic OH group content of the lignin samples were determined as well. These results were then compared to the FTIR results, which revealed an under-estimation of the phenolic OH groups from the non-aqueous potentiometric titration, which was likely due to the differences in the pKa between the lignin and the calibration standard 4-hydroxybenzoic acid. Further, a clear correlation was found between the lower Mn and the increased phenolic OH group content via SEC analyses. The work outlined in this paper give complementary views on the characterization and quantification of technical lignin samples via FTIR.

A Validated Potentiometric Titration Method for Quantitative Determination of Molnupiravir from Pharmaceutical Preparation

A simple precise, rapid accurate and sensitive non-aqueous potentiometric titration method was developed for quantitative determination of molnupiravir from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD &lt;1 (n = 6). The method showed strict linearity (r2 &gt; 0.9999) between 10 % to 50 % w/v of 100 mg of drug substance weight. The percentage recovery of molnupiravir in the optimized method was between 99.05 to 99.81 %. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.

The role of phosphotungstic acid in enhancing the catalytic performance of UiO-66 (Zr) and its applications as an efficient solid acid catalyst for coumarins and dihydropyrimidinones synthesis

In recent study, we report a facile and easy technique for the synthesis phosphotungstic acid (PTA) with different weight contents (10, 25, 50 and 75 wt%) loaded on UiO-66 (Zr) as efficient and reusable catalysts for the preparation of coumarin and dihydropyrimidinones derivatives. The structural and textural properties of the prepared catalysts were characterized through XRD, FT-IR, TGA, BET, TEM, SEM, non-aqueous potentiometric titration and FT-IR of chemisorbed pyridine. 50.0 wt% of PTA/UiO-66 (Zr) catalyst showed the highest surface acidity (Ei = 578.5mV) and highest catalytic performance toward the preparation of 7-hydroxy-4-methyl coumarin (97.8%) and 3, 4-dihydropyrimidinones (94.7%).

A Validated Potentiometric Titration Method for Quantitative Determination of Favipiravir from Pharmaceutical Preparation

A simple precise, rapid accurate and sensitive non-aqueous potentiometric titration method was developed for quantitative determination of favipiravir from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD &lt;1 (n = 6). The method showed strict linearity (r2 &gt; 0.9999) between 10 % to 50 % w/v of 0.200 mg of drug substance weight. The percentage recovery of favipiravir in the optimized method was between 99.65 to 100.08 %. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.

Sulfamic acid supported on mesoporous MCM-41 as a novel, efficient and reusable heterogenous solid acid catalyst for synthesis of xanthene, dihydropyrimidinone and coumarin derivatives

Herein, the incorporation sulfamic acid (SA) into mesoporous silica (MCM-41) introduced an effective approach in numerous multicomponent reactions. SA/MCM-41 composites with different weight content of SA were successfully synthesized through easy impregnation method. The as-synthesized composites were characterized by different techniques like SEM, EDX, TEM, XRD, BET and FT-IR spectroscopy. The acidic characters of the composites have been studied using FTIR of chemisorbed pyridine and non-aqueous potentiometric titration. TEM and XRD measurements approve that MCM-41 shows an ordered mesoporous structure with hexagonal and honeycomb lattice and its mesoporous structure did not change even after modification with SA. MCM-41 shows high surface area (1287 m 2 /g), which reduced after addition of sulfamic acid until reached to 611 m 2 /g at 90 wt% SA-MCM-41. The acidic strength of the prepared composites progressively improved by raising SA contents up to 75 wt% SA/MCM-41. The as-synthesized composites were tested for multicomponent reactions such as preparation of 3,4-dihydro-pirimidin-2(1H)-ones (DHPs), 7-hydroxy-4-methylcoumarin and 14-Phenyl-14H-dibenzo [a, j] xanthene. SA/MCM-41 catalysts displayed excellent performance in 14-phenyl-14H-dibenzo [a, j] xanthene (95.8%), 3, 4-dihydropyrimidinones (94.4%) and 7-hydroxy-4-methylcoumarin (96.7%). The prepared catalysts displayed excellent reusability without significant loss in catalytic performance from the fresh run. • A highly active and stable MCM-41 supported with sulfamic acid catalysts have been successfully synthesized. • All loaded catalysts exhibited distinct catalytic activity in synthesis of xanthene, dihydropyrimidinone and coumarin. • The catalysts showed an excellent yield % up to 95% in all reactions and also show excellent recycling efficiency.

Silver nanoparticles supported on UiO-66 (Zr): As an efficient and recyclable heterogeneous catalyst and efficient adsorbent for removal of indigo carmine

As incorporating silver nanoparticles (Ag NPs) into zirconium metal-organic frameworks (UiO-66) offer an extensive potential in numerous applications such as wastewater treatment and catalysis, we herein synthesized UiO-66, followed by incorporating different contents of Ag NPs into UiO-66. The prepared UiO-66 composites were identified by means of various techniques like X-ray-diffraction patterns (XRD), nitrogen adsorption desorption (BET), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) analysis. Besides, acidic properties of composites were examined using FTIR of chemisorbed pyridine and non-aqueous potentiometric titration. The results displayed that UiO-66 crystals exhibited sizes of 180 and 240 nm. Their surface area and total pore volume respectively reached 1593 m 2 g −1 and 0.834 m 3 g −1 , and decreased by incorporating Ag NPs to 863 m 2 g −1 and 0.432 m 3 g −1 at 5.0 wt% Ag/UiO-66. TGA data manifested that adding Ag NPs could improve the thermal stability of the primitive UiO-66. The as-synthesized composites were tested towards indigo carmine (IC) adsorption from aqueous media and in synthesis of 3,4-dihydro-pirimidin-2(1H)-ones (3,4-DHPs). The adsorption data showed that silver nanoparticles incorporation enhanced IC removal performance of UiO-66 and adsorption capacity was augmented from 87.2 mg g −1 (UiO-66) to 312.8 mg g −1 at 2.0 wt% Ag/UiO-66. This performance was efficient relying on adsorption isotherm measurements, indicating that incorporating Ag NPs augmented the number of adsorption sites and π–π interactions between adsorbate and adsorbent were enhanced, resulting in improved adsorption capacity towards anionic dyes. Also, incorporated Ag NPs show better catalytic activity in the preparation of DHPs and the yield reached 88% using 2.0 wt% Ag/UiO-66, imparting excellent recyclability for four cycles.

Greener route for the removal of toxic heavy metals and synthesis of 14-aryl-14H dibenzo[a,j] xanthene using a novel and efficient Ag-Mg bimetallic MOF as a recyclable heterogeneous nanocatalyst

Removing of heavy metal ions from aqueous solutions has become a serious challenge from both biological and environmental viewpoints. Recently, metal-organic frameworks (MOF) including two metal ions in its framework have been enhanced as promising structure in the capture of various hazardous and toxic substances. Herein, Ag-Mg-MOF were synthesized through a one-step approach using solvothermal technique. Then, the as-synthesized Bimetallic MOFs were characterized by TEM, SEM, EDS, XRD, FTIR and N2 adsorption. The as-synthesized Ag-Mg-MOF samples were used for heavy metal removal. The results showed that the adsorption of cadmium, lead and Cupper ions on MOF was improved by the pH increasing. The experimental data were examined through Freundlich and Langmuir models. The fabricated Ag-Mg MOFs exhibit enhanced decontaminant performance toward Cu2+, Cd2+and Pb2 ions in terms of high adsorption capacities, Pb2+ (350 mg/g)> Cd2+ (270 mg/g)> Cu2+ (202 mg/g), and ultrafast kinetics compared to the monometallic Mg-MOF. FT-IR spectra of adsorbed pyridine methods and non-aqueous potentiometric titration were used for measuring surface acidity of the prepared MOF. It was observed that the surface acidity and the catalytic activity were increased in bimetallic MOF compared to monometallic MOF. The catalytic results of the formation of free solvent 14-aryl-14-Hdibenzo[a,j]xanthene compound by Ag-Mg MOF showed a high yield at a lower time. Also, the prepared MOF catalysts still preserved their initial catalytic activity even after the 4th run. The results of this work demonstrate that the novel Ag-Mg MOFs nanocatalysts have great potential for applications in environmental protection, especially in heavy metal ions removal present in wastewaters and in the synthesis of pharmacologically and biologically active compound.

Quantitative determination of the new substance 7-(4-fluorobenzyl)-3-thioxo-2,3-dihydro[1,2,4]triazolo[4,3-a]pyrazin-8(7H)-one as a potential pharmaceutical agent

The article presents results of studies on the development of a quantification method for a substance 7-(4-fluorobenzyl)-3-thioxo-2,3-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-8(7H)-one using the method of nonaqueous potentiometric titration. Validation of the developed method has been carried out confirming the following characteristics: linearity, accuracy and precision that match the acceptance criteria for these measures.

Synthesis of sulfated zirconium supported MCM-41 composite with high-rate adsorption of methylene blue and excellent heterogeneous catalyst

Zirconia-based mesoporous MCM-41 was successfully prepared then loaded with different content of sulfate (5, 10, 15, 25, 40 and 50 wt.%) through the wet impregnation method. The prepared samples were characterized by numerous methods like N2 adsorption (T= - 196 °C), FT-IR, XRD and TEM images. FTIR spectra of chemically adsorbed pyridine and non-aqueous potentiometric titration were applied to measure the acidity of SO42−/ZrO2@MCM-41 (SZ/MCM-41) catalysts. XRD results showed that the lattice cell parameter (a0) is increased from 37.8 to 39.5 Ǻ with increasing the sulfate content. TEM images of SZ/MCM-41 samples exhibit ordered arrays of mesoporous structure with light and dark contrast and also the formation of nanorods with a diameter of 50 nm. The resulting materials showed a large surface area with a uniform pore diameter distribution. All samples displayed both Lewis and Brønsted acid sites. The catalytic activity of SZ/MCM-41 samples was examined for the preparation of 7-hydroxy-4-methyl coumarin which dramatically enhanced when compared with MCM-41 and Z/MCM-41 and the reaction continued efficiently with a yield of 99.3–89.8 % after reused four times. Furthermore, the adsorption behavior of as-synthesized samples was examined over methylene blue (MB) in the aqueous solution with varying parameters such as dye concentration, pH of the solution and contact time. The prepared samples have a good ability to eliminate the methylene blue from aqueous solution with adsorption capacity equal to 186 mg/g and the equilibrium time of 60 min.

Unprecedented green chemistry approach: tungstophosphoric acid encapsulated in MOF 199 as competent acid catalyst for some significant organic transformations

In the work, a series of new 12-tungstophosphoric acid (HPW) encapsulated MOF 199 catalysts were synthesized by simple and convenient one step method. The structural and textural properties of the synthesized catalysts were fully characterized by using different techniques such as FTIR, XRD, N2 adsorption–desorption, TEM and SEM. The acidic properties were also studied by using nonaqueous potentiometric titration and FTIR spectra of chemisorbed pyridine techniques. The efficacy of the newly synthesized acid catalysts was tested in the production of 3,4-dihydropyrimidin-2(1H)-one through three-component coupling based Biginelli reaction and biodiesel production through stearic acid esterification reaction. The obtained results indicate that the MOF 199 preserves its structure without any noteworthy changes after the fruitful incorporation of HPW crystals within its cavities. Furthermore, an extraordinary improvement in both Lewis and Bronsted acid sites is observed as a result of the HPW encapsulation process. The catalytic activity results showed that the catalyst displayed excellent performance, where 98.3% of 3,4-dihydropyrimidin-2(1H)-one was obtained over 0.02 g of 50HPWMOF 199 after 2 h at 80 °C using benzaldehyde: ethyl acetoacetate: urea molar ratios of 1:1:1.5. Additionally, 94.1% conversion of stearic acid was observed after 3 h over 0.05 g of 50HPWMOF 199 at ~ 80 °C using stearic acid: ethanol molar ratio of 1:8. Moreover, the catalysts also demonstrated excellent reusability in the investigated organic reactions which can be used many consecutive eras without meaningful loss of their catalytic performance. The achieved high catalytic performance of the synthesized catalysts in the Biginelli and esterification reactions are attributed to uniform HPW distribution inside MOF 199 cavities as well as the Lewis acidity property of MOF 199. The results also demonstrated that the incorporation of HPW crystals within MOF 199 cavities through the encapsulation process is more efficient than the impregnation method.

Novel bimetallic Ag-Fe MOF for exceptional Cd and Cu removal and 3,4-dihydropyrimidinone synthesis

Removing heavy metals from aqueous solutions has drawn the attention of scientists due to their serious global health challenges to human society. Thus, it is very important to use an adsorbent with a high removal efficiency of heavy metals and has the advantage of low-cost. In the present work, metal-organic framework with tailored components is very important in attaining the required purpose and expanding the developing applications. Herein, bimetallic Ag-Fe metal-organic framework has been successfully synthesized through a solvothermal method and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy and surface area measurements. Due to the synergistic contribution between Ag and Fe, bimetallic Ag-Fe metal-organic frameworks nanocrystals exhibit enhanced decontamination performance toward the removal of heavy metal ions with ultra-fast adsorption kinetics and high adsorption values. Impressively, an extraordinary Cadmium (II) and Copper (II) adsorption values up to 265 and 213 mg/g, respectively are obtained in bimetallic (0.6:1) Ag-Fe metal-organic framework, which considers the superior adsorbent between the prepared metal-organic frameworks. The surface acidity, examined through the nonaqueous potentiometric titration of n-butylamine, was found to be increased by the formation of a bimetallic metal-organic framework as well as the catalytic activity. Among various Ag: Fe, the ratio (0.6:1) showed the highest acidity and catalytic activity towards the synthesis of 3,4-dihydropyrimidinone. The metal-organic frameworks catalysts were found to maintain their adsorption capacity and catalytic activity even after four-time reusing.

A validated non-aqueous potentiometric titration method for quantitative determination of bromhexine hydrochloride from pharmaceutical preparation

A simple precise, rapid accurate and sensitive non-aqueous potentiometric titration method was developed for quantitative determination of bromhexine hydrochloride from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD 0.9999) between 50% to 250% of 0.100 mg of drug substance weight. The percentage recovery of bromhexine hydrochloride in the optimized method was between 99.38 to 99.76%. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.

A Non-aqueous Potentiometric Titration Method for Validation of Imatinib mesylate from Pharmaceutical Dosages

A simple precise, rapid accurate and sensitive non-aqueous potentiometric titration method was developed for quantitative determination of imatinib mesylate from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD 0.999) between 20% to 100% of 500 mg of drug substance weight. The percentage recovery of imatinib mesylate in the optimized method was between 100.087 to 100.692%. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.

A non-Aqueous Potentiometric Titration Method for Validation of Secnidazole from Pharmaceutical Dosages

A sensitive non-aqueous potentiometric titration method was developed for quantitative determination of secnidazole from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD 0.999) between 20% to 100% of 500 mg of drug substance weight. The percentage recovery of secnidazole in the optimized method was between 99.643 to 100.505%. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.

Analysis of drug ofloxacin in bulk and single component pharmaceutical tablets by non-aqueous potentiometric titration method

Analysis of drug ofloxacin in bulk and single component pharmaceutical tablets by non-aqueous potentiometric titration method

Preparation, characterization of highly active recyclable zirconium and tin tungstate catalysts and their application in Pechmann condensation reaction

In this contribution, a facile and efficient one-step method for the preparation of mesoporous zirconium and tin tungstate with different Zr or Sn:W molar ratios. The prepared catalysts were characterized by different textural and spectroscopic techniques such as XRD, Raman spectra, SEM, EDX, TEM and N2 adsorption–desorption at − 196 °C. The surface acidity was measured by nonaqueous potentiometric titration of n-butylamine and FTIR spectra of chemisorbed pyridine. XRD results showed that all the prepared samples calcined at 400 °C are amorphous, no evidence for formation of big aggregates of WOx species on the catalyst surfaces, but all WOx species are homogeneously dispersed as small particles on the surfaces. At higher ratio of W (ZrW3 and SnW3) the excess WOx species are distributed inside the pores or block the pores by covering the necks of the pores, which leads to decrease in the specific area as evident from N2 adsorption- desorption study. Raman spectra showed that the tungstate species has WO4 distorted tetrahedral structure. The surface acidity measurement showed that the catalysts contain mixture of Lewis and Bronsted acid sites with different ratios, the maximum B/L ratio reach maximum value at molar ratio 1:2 (ZrW2 and SnW2). The results showed that zirconium tungstate samples have higher surface acidities than tin tungstate samples. The prepared catalysts showed high catalytic activities for the synthesis of 7-hydroxy-4-methyl coumarin via the Pechmann condensation reaction of resorcinol with ethyl acetoacetate. High yield (~ 94%) with 100% selectivity of 7-hydroxy-4-methyl coumarin was obtained under solvent free conditions.

Catalytic pyrolysis of larch sawdust for phenol-rich bio-oil using different catalysts

Abstract Different kinds of catalysts have a great influence on the characteristics and products of the biomass catalytic pyrolysis. Catalysts of Cu/C, Pd/C, Pd Ag and H-Zeolites socony mobil #5 (HZSM-5) were selected and characterized by the X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM). Decomposition behaviors of the larch catalytic pyrolysis were studied by the thermogravimetric analyzer (TG). The total carboxylic acids (TCAs) and total phenolic compounds (TPCs) in bio-oil were determined using the non-aqueous potentiometric titration method. The chemical distribution of bio-oil was investigated by the gas chromatography/mass spectrometry (GC/MS). Results showed that the temperature of the maximum weight loss rate of larch was decreased by adding these four catalysts. The carbon residue rate was increased by using HZSM-5. The content of GC-detected phenols increased from 25.28% to 35.11% (area) by adding Pd/C. However, TCAs in bio-oil were decreased sharply with Pd Ag and Pd/C. HZSM-5 promoted the formation of phenols and enhanced TPCs in bio-oils (26.56 wt%), which increased by approximately 35% compared to that from the non-catalytic pyrolysis process. This phenol-rich bio-oil can be used to replace the traditional phenol for the manufacturing of high-value biomaterials.

A validated non-aqueous potentiometric titration method for quantitative determination of clopidogrel bisulphate from pharmaceutical preparation

A simple precise, rapid accurate and sensitive non-aqueous potentiometric titration method was developed for quantitative determination of terbutaline sulphate from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD 0.9999) between 50% to 150% of 0.400 mg of drug substance weight. The percentage recovery of terbutaline sulphate in the optimized method was between 99.39 to 99.64%. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.

A validated non-aqueous potentiometric titration method for quantitative determination of alprazolam from pharmaceutical preparation

A simple precise, rapid accurate and sensitive non-aqueous potentiometric titration method was developed for quantitative determination of lafutadine from pharmaceutical dosage form. The titration was carried out using standardized 0.1 N perchloric acid. The proposed method was found to be precise with % RSD 0.99) between 20% to 100% of 100 mg of drug substance weight. The percentage recovery of lafutadine in the optimized method was between 99.878 to 101.315%. The method is also found to be rugged when checked by different analysts and using different lots of reagents and different makes of titrators.