Alkaline Reagents Research Articles

Sunflower straw ash as an alternative activator in alkali-activated grouts: A new 100% waste-based material

Alkali-activated grouts (AAGs) are increasingly used to replace ordinary portland cement owing to their several advantages. The mechanical properties and environmental aspects of AAGs are affected by the type of activator. In this study, the effects of sunflower stalk ash (SSA) and commercial alkaline reagents on the mechanical properties, microstructures, and CO2 emissions of geopolymer grouts were investigated for the first time using blast furnace slag and black rice husk ash as precursors. The results indicated that the potassium and calcium salts in the SSA promoted the formation of C(K)-A-S-H and C–S–H. The compressive strength of the SSA-activated grouts was higher than that of the slurry prepared using commercial products (24.88 vs. 11.59 MPa). Using SSA instead of commercial reagents can reduce kg CO2-eq/t powder by 84.4 %.

Hexagon flower-shaped architectures constructed of Fe-composited lanthanum hydroxide nanosheets for superior phosphate removal: Synthesis and mechanism study

In response to phosphorus pollution, developing functional materials for phosphate adsorption is an ideal method to reach an ultralow phosphate concentration in effluent. Herein, a hexagon flower-shaped architecture constructed of Fe-composited lanthanum (La)-based hydroxide nanosheets was fabricated from LaFe cyano-bridged metal frameworks (CMs) via a self-templating strategy using NH3‧H2O as the conversion reagent. The ion exchange process using weak alkaline reagent enables the formation of secondary nanosheets on the architecture, thus leading to a high surface area and a large number of mesopores that provide abundant active sites and mass transfer channels for phosphate adsorption. A superior adsorption capacity of 127.5 mg P/g can be obtained on the La/Fe-based architecture, which also shows satisfactory applicability over a wide pH range. A ligand exchange between -OH and phosphate ions is verified as the main adsorption mechanism, which properly accounts for its excellent selectivity for phosphate adsorption when coexisting with other anions/cations and natural organic matters. Overall, the present study provides a new method for constructing porous La-based hydroxide materials for phosphorus control in water.

Behavior of heavy metals and natural radionuclides along the Moroccan phosphogypsum carbonation process with several alkaline reagents

Phosphogypsum (PG) is the main by-product from the phosphoric acid (PA) production industry being the PA production the basic raw material for producing the modern fertilizers. Because of its high calcium and sulfate content, it is important to emphasize that ecological benefits come from recycling and eventually converting PG into value-added compounds are obtained. This work aims to remedy the environmental problems associated to the large quantities of PG generated in Morocco. Furthermore, three procedures for PG conversion into Ca(OH)2, CaCO3, Na2SO4, K2SO4 and (NH4)2SO4 using hydroxide aqueous mediums were studied. The impurity traces contained in the PG were generally found to be completely transferred into the final calcite. The sulfates produced here are recommended for the use as a fertilizer (K2SO4 and (NH4)2SO4) and in the manufacture of detergents (Na2SO4), and the obtained calcite could be used in cement production, concretes, permeable reactive barriers for pollutants removing, etc.

Geopolymer mortar with flash-calcined sediments cured under ambient conditions

This paper focuses on the development of a geopolymer (GP) mortar that can be cured under ambient conditions using a combination of flash-calcined dredged sediment (FCS), Metakaolin (MK), granulated blast furnace slag (GBFS), and potassium silicate (K2SiO2) as an alkaline reagent (AR). The goal of this research is to reduce carbon emissions from traditional clinker-based materials by using valorized materials in the formulation of the geopolymer binder. The study investigates the effect of the alkaline reagent-to-binder ratio (AR/Bmm) and precursor composition on the mechanical and durability properties of the GP mortar. The results indicate that the lowest AR/B ratio and formulations with higher GBFS percentages have better performance. Porosity test and microstructural analysis tests such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) was conducted to ensure the stability of the GP formulations exposed to a sulfuric acid attack test, while nuclear magnetic resonance (NMR) tests validate the Q4(1Si, 3Al) network and their assigned Si/Al ratio. The leaching examination concludes that the GP design is not classified as hazardous materials.

Base Course Stabilization Performance Using Fly Ash-Based Geopolymers and Their Effect on Water Quality Standards

The road is the main gateway to human life and links essential access points. Some structure pavement failures happened due to the base layer's instability. Fly ash has been used in several parts of pavement structures to increase stability. One significant concern with using fly ash in base course stabilization is its proportion and potential impact on water quality standards. This research aimed to evaluate base course stabilization performance using fly ash-based geopolymers, as well as assess their impact on water quality standards. Materials in this study consisted of aggregate, fly ash, water, and alkaline reagent solutions. The variation of mix considered with a variety of alkaline reagents, namely without alkaline reagents, 3 mol, 6 mol, 9 mol, and 12 mol of NaOH. The ratio between NaOH and Na2SiO3 is 1:2. The use of fly ash in the class A aggregate base course layer has not been able to meet specifications. However, by providing 9 mol of alkaline reagent, the strength of the mixture increases so that the CBR value meets the specifications due to geopolymer bonding. When the alkaline reagent solution becomes more concentrated, the optimum water content decreases, and the bond between aggregates strengthens. The effect of alkaline reagents on water quality standards increases the acidity (pH) value, while other parameters such as BOD, COD, and TSS still meet the standards. This research point to another practical approach that is effective in the field to increase the stability of the base course layer and is environmentally friendly.

Bacterial communities shift and influence in an acid mine drainage treatment using barium carbonate disperse alkaline substrate system

Chemical passive treatment systems used to remediate acid mine drainage has been evaluated based mainly on the reactivity of the chemical alkaline reagents, overlooking the activity of the microorganisms that proliferate in these artificial ecosystems. In this study, the bacterial communities of a unique passive treatment system known as BDAS (Barium carbonate Dispersed Alkaline Substrate) were investigated using 16S rRNA gene metagenomic sequencing combined with hydrochemical characterization of the AMD and phenotypic characterization of biogenic precipitates. According to the hydrochemical characterization, the water quality improved as the water progressed through the system, with a drastic increase in the pH (up to alkaline conditions) and total organic carbon, as well as the removal of main contaminants such as Ca2+, SO42−, Fe3+, Al3+, and Mn2+. These environmental changes resulted in an increase in bacterial diversity (richness) after the inlet and in the shift of the bacterial communities from chemoautotrophs (e.g., Ferrovum and Acidiphilum) to chemoheterotrophs (e.g., Brevundimonas and Geobacter). Some of these taxa harbour potential to immobilize metals, aiding in the treatment of the water. One of the mechanisms involved in the immobilization of metals is microbially induced calcium carbonate precipitation, which seems to occur spontaneously in BDAS. The production of biofilm was also observed in most parts of the system, except in the inlet, helping with the removal of metals. However, in the long run, the build-up of biofilm and precipitation of metals could clog (i.e., biofouling) the pores of the matrix, reducing the treatment efficiency. Potential human pathogens (e.g. Legionella) were also detected in BDAS indicating the need for a treatment step at the end of the system to remove pathogenic microorganisms. These findings present a new perspective of the bacterial communities and their effects (both positively and negatively) in a chemical passive treatment system.

Analiza kawern i zwężeń w otworach wiertniczych na złożach węglowodorów w Azerbejdżanie

An analysis of numerous well data from the Karabagly and Kursangi monocline regions in Azerbaijan showed that the main reasons of natural curvature are structural and geological conditions of wells. In contrast to a number of fields where wells are naturally bent in only one direction under the combination of geological, technical and technological factors, there are three other directions in the areas of the Karabagly and Kursangi monocline. It is suggested that according to the proposed technology, drilling intervals are minimized by an assembly with a crooked sub, and the technical and economic parameters of drilling are improved. With an increase in the content of alkaline reagents in the drilling fluid, despite a significant decrease in the absolute value of fluid loss, the likelihood of complications increases. One of the main requirements for maintaining the integrity and stability of the wellbore is the prevention of filtration. This condition imposes a certain limitation on the amount of fluid loss in drilling fluids. In drilling practice, it is necessary to strive not only to minimize the fluid loss of flushing fluids, but also to the qualitative and quantitative evaluate various additives that slow down their physical and chemical impact on the rocks forming the walls of the well.

Performance evaluation of NOx absorption by different denitration absorbents in wet flue gas denitration

BackgroundDeveloping efficient denitration absorbents transforming the NOx of flue gas into nontoxic species are critical for wet flue gas denitration (WFGD). MethodPerformance of various denitration absorbents and their unique mechanisms were investigated by a laboratory-scale apparatus, and the denitration efficiency was quantified via response surface method. ResultsThe denitration efficiency were Na2SO3>Na2S>(NH4)2SO3>TEA>KI>Na2S2O3>NaOH>CO(NH2)2>NH3∙H2O>H2O. Na2SO3, Na2S, (NH4)2SO3, TEA, KI and Na2S2O3 removed NO2 by reducing it into NO2− ion, where the denitration efficiency showed positive correlation with reducing ability. The CO(NH2)2 eliminated NO2 by reducing it into nontoxic N2, but the efficiency was limited due to its low reactivity at low temperatures. The alkaline reagents including NaOH and NH3∙H2O promote NOx absorption via acid-base neutralization mechanism leading to both NO2− and NO3− ions formation. For Na2SO3 with highest denitration efficiency, pH significantly affects its efficiency by changing the proportions of its hydrolysate, oxygen weakens the NOx absorption capacity of absorbent by oxidizing SO32− into inert SO42−, and the accumulation of NO2− ions greatly suppresses the denitration efficiency, whereas NO3− ions had negligible effect. The quadratic regression model could accurately quantify and predict the effects of various factors on denitration efficiency.

A Comprehensive Study on Asparagus officinalis: Its Antimicrobial, Antioxidant and Phytochemical Characteristics

The Asparagus plant is considered to be a palatable chemical source against treating infectious diseases and flavorings. Its prevalent distribution is well-known in Asian and sub-Asian regions. Objective: To understand different activities that have been functional in the stem and leaf extracts of Asparagus officinalis including antioxidant and antibacterial activities. Further, phytochemical constituents of asparagus are also discussed. Methods: The antibacterial assay of extracts for the variety of bacteria, indicated a maximum inhibition zone against Enterococcus faecalis (ATCC 29212) (24 mm) followed by Staphylococcus aureus (ATCC 25923) (34 mm), whereas Bacillus subtilis (ATCC 6633) (14 mm) at their respective temperature a minimum inhibition zone after 24 hours and 48 hours of incubation (37 °C for bacteria). Results: As a robust antioxidant reference standard, these antioxidant activities resulted in the stable radical 1-diphenyl-2-picrylhydrazyl (DPPH). It can be reduced to yellow-coloured DPPH-H, reaching 75.81% of the DPPH scavenging impact at its 100% concentration in contrast to ascorbic acid. Various experiments have been carried out, including the Molisch test, Ninhydrin test, Wagner’s test, Alkaline reagent test, Froth test, Ferric reagent test, and Salkowski test for the phytochemical analysis. Conclusion: To sum that up, carbohydrates, saponins, and flavonoids are present in these extracts. These extracts were found to perform satisfactory activities in all tests.

Multi-stage precipitation for the eco-friendly treatment of phosphogypsum leachates using hybrid alkaline reagents

The leachate of waste phosphogypsum (PG) contains substantial amounts of phosphate, sulfate, and fluoride, which poses an immense threat to the safety of the aquatic ecosystem. In this study, a multi-stage precipitation approach is proposed to treat PG leachates using hybrid alkaline reagents including barium hydroxide (Ba(OH)2) and quicklime (CaO). To avoid potential environmental impacts, hazardous environmental contaminants are removed from the PG leachates by adding alkaline reagents in a specific order. The multi-stage precipitation approach achieves nearly 100% removal efficiencies for phosphate, fluoride, and metal ions as well as satisfactory removal efficiencies for sulfate and ammonia nitrogen (93.6% and 94.8% respectively). The compositions of generated mineral precipitates are comprehensively investigated by analytical techniques including X-ray diffraction (XRD), transmission electron microscope (TEM), etc. The main precipitated mineral phases are barite (BaSO4), brushite (CaHPO4·2H2O), and hydroxyapatite (Ca5(PO4)3OH). This is further proven by the geochemical modeling using Visual MINTEQ, in which the precipitation of mineral phases is calculated. Furthermore, a straightforward economic analysis indicates the proposed method has a lower cost of the use of alkaline reagents. Overall, this study establishes an effective and eco-friendly approach for the treatment of waste PG leachates to remove hazardous environmental contaminants and recover valuable precipitates.

A green repair pathway for spent spinel cathode material: Coupled mechanochemistry and solid-phase reactions

A way of directly repairing spent lithium-ion battery cathode materials is needed in response to environmental pollution and resource depletion. In this work, we report a green repair method involving coupled mechanochemistry and solid-state reactions for spent lithium-ion batteries. During the ball-milling repair process, an added manganese source enters into the degraded LiMn2O4 (LMO) crystal structure in order to fill the Mn vacancies formed by Mn deficiency due to the Jahn–Teller effect, thereby repairing the LMO's chemical composition. An added carbon source acts not only as a lubricant but also as a conductor to improve the material's electrical conductivity. Meanwhile, mechanical force reduces the crystal size of the LMO particles, increasing the amount of active sites for electrochemical reactions. Jahn–Teller distortion is successfully suppressed by cation disorder in the LMO material. The cycling stability and rate performance of the repaired cathode material are thereby greatly improved, with the discharge specific capacity being more than twice that of commercial LMO. The proposed solid-state mechanochemical in situ repair process, which is safe for the environment and simple to use, may be extended to the repair of other waste materials without consuming highly acidic or alkaline chemical reagents.

Ammonia Recovery from Livestock Manure Digestate through an Air-Bubble Stripping Reactor: Evaluation of Performance and Energy Balance

The recovery of livestock manure, rich in nutrients, as fertilizer in agriculture, could pose the risk of an excessive load of nitrogen on the soil. Ammonia stripping is one of the available technologies for reducing the amount of nitrogen in the digestate obtained by the anaerobic digestion of manure. The study investigated the performance and energy consumption of a full-scale ammonia-stripping plant, equipped with a bubble reactor and working without the use of any alkaline reagent under semi-batch conditions. Stripping tests were conducted on the liquid fraction of the digestate, studying the current and optimized operative conditions of the plant. The main variables influencing the process were pH, temperature, airflow, and feed characteristics. In the experimental tests, the pH spontaneously increased to 10, without dosing basifying agents. Higher temperatures favoured the stripping process, the higher tested value being 68 °C. The airflow was kept equal to 15 Nm3 h−1 m−3digestate in the pre-stripping and to 60 Nm3 h−1 m−3digestate in the stripping reactors, during all tests. The energy requirement was completely satisfied by the CHP (combined heat and power) unit fed with the biogas produced by manure digestion. Results showed anaerobic digestion coupled with stripping to be a suitable solution for removing up to 81% of the ammonium with neither external energy input nor reagent dosage.

Evaluation of flavonoid compound in coconut waste and its antioxidant activity

The coconut tree, Cocos nucifera L., is planted for a variety of purposes. According to the Malaysian Agricultural Research and Development Institute (MARDI), rising coconut production has resulted in an increase in agricultural waste (coconut husk) in Malaysia (536,606 million coconuts in 2018 compared to 22,167 million coconuts in 2016). More than 60% of solid waste degradation in the environment is caused by the manufacture of coconut husks each year. Recycling coconut waste, particularly coconut husk, as a source of natural compounds offers environmental and economic benefits. The objectives of this study are to extract the flavonoid compounds from coconut husk from three different types of coconut fruit (Pandan Coconut, MAWA Coconut and Yellow Coconut) by using ethanolic solvent and compare them. Secondly, the antioxidant activity of coconut husk was determined by using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Thirdly, the alkaline reagent test was used to determine the presence of flavonoid compounds. The flavonoid compounds are existed in the coconut husk ethanolic extract and it have the antioxidant activity. IC50 of the standard compounds, ascorbic acid was 9.2 μg/ml. The most powerful radical scavenging effect was seen in Yellow Coconut husk extract, which had an IC50 value of 8.4 μg/ml. Flavonoids found in the husk of coconuts are known to have antioxidant properties. This shows that coconut husk extract has enormous potential as a natural preservative and a good bioresource of antioxidants.

Extraction and determination of flavonoid compounds in citrus fruit waste

Citrus is a globally cultivated fruit crop that has been heavily industrialised to manufacture food products. It is commonly sought out for its nutritional benefits. However, parallel to rapid industrialisation, parts of the crop’s physical composition (inner and outer peel, seeds etc.) are often discarded to the environment as waste. Recent advancement in technology has led researchers to look for alternatives to recover potential therapeutic compounds from citrus fruit waste, directly extending the life of the waste and indirectly solving waste management concerns. Citrus fruit peels are especially rich in flavonoid compounds, a subclass of the many phytochemicals largely present in the body of the fruit. Flavonoid compounds have the capacity to be act as antioxidants, leaving room for the potential of the flavonoids present in fruit waste to be commercialized as a natural bioresource. This study aims to extract and recover the flavonoid compounds present in the peels of citrus fruits calamansi (Citrus microcarpa), kaffir lime (Citrus hystrix), and key lime (Citrus aurantiifolia) via ethanolic extraction and test the presence of recovered flavonoid compounds via alkaline reagent test. In addition, this study also aims to measure the antioxidant activities of all three citrus fruit peel samples via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. This study hopes to shed light on the therapeutic potential of citrus fruit peel waste as a bioresource which could benefit communities in the future.

Geopolymers-based application for the up-cycling utilization of construction and demolition waste from the 2016 central Italy earthquakes

The 2016 seismic sequence in central Italy produced huge amounts of rubble. The need to recycle construction and demolition waste (CDW) to facilitate reconstruction process is therefore a problem of highest concern for quantities involved. In addition, CDW from rubble is very difficult to recycle being an extremely heterogeneous material.In this study, in order to produce mortars, the complete replacement of natural aggregate was investigated using the finest as-received CDW (0–8 mm) produced by local plants that managed the 2016 earthquake rubble.Results revealed that samples containing 60 wt.% CDW, metakaolin as precursor and K-silicate as alkaline reagent, have mechanical properties up to 28.7 MPa and mostly in the range of structural ordinary cementitious materials, suggesting that even the CDW fine fractions could be used in the production of upcycling mortars.

Методика сохранения биологически активных веществ при обработке многокомпонентного побочного рыбного сырья

The conditions of chemical hydrolysis of by-product fish raw materials (skin) of Atlantic herring were determined to obtain a food additive with a maximum yield of biologically active substances. The objects of the study were hydrolysates with a chemical reagent concentration of 0.2% (sample 1), 0.3% (sample 2), 0.4% (sample 3), in which the content of essential amino acids (methionine, lysine and threonine) and fat-soluble vitamins (A, D3, E) were determined by high-performance liquid chromatography. Pretreatment of herring skin with scales was treated with an alkaline reagent with a concentration of 0.05% and a liquid coefficient (LC = 4) for 60 minutes at a temperature of 55 ± 0.5°C, after which the samples were hydrolyzed at the above concentrations for 120 minutes at a temperature of 90 ± 0.5°C. The principal thing in the study was the selection of two parallel samples, excluding the influence of the human factor, which were mathematically processed into two calculations (two chromatograms), and the arithmetic mean of the indicator was derived from the results of two measurements using the LabSolution software. It was found that after pretreatment for 60 minutes, the concentration of 0.3% alkaline reagent is the best for hydrolysis of marine fish by-products (skin) of Atlantic herring at a temperature of 90 ± 0.5°C. Hydrolysis in the presence of such a concentration allowed to obtain the maximum yield of amino acids (2.76; 2.00 and 1.15%) and fat-soluble vitamins (0.16; 0.0039 and 0.29).

ANTIMICROBIAL, ANTIOXIDANT, CYTOTOXIC ACTIVITY AND PHYTOCHEMICAL ANALYSIS OF ETHANOLIC EXTRACT OF CITRUS LIMETTA (PEEL, STEM AND LEAVES)

Citrus limetta plant has potent activities against different infectious diseases and globally consumed citrus fruit. Studies revealed this plant has several chemical constituents that are known to have anti-microbial, anti-inflammatory, antioxidant properties. This plant is a best source to boost immunity and fight against infections and common flu and cold. The plant Citrus limetta (leaves, peel, stem) used in this research were collected from various areas of Pakpattan (Green Town) and ethanolic extract was prepared as per standard protocols. Gram-positive bacteria i.e., Staphylococcus aureus (ATCC 25923), Bacillus subtilis (ATCC 6633), Enterococcus faecalis (ATCC 29212) and Gram-negative bacteria i.e., Pseudomonas aeruginosae (ATCC 27853) and Klebsiella pneumonia (ATCC 33152) were used to check the anti bacterial activities. Both Disc diffusion and well diffusion methods were used for the anti-bacterial pursuits. The cytotoxic pursuit of plant abstraction was set on using an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-dipenyltetrazolium bromide] analysis. Antioxidant activities were analyzed by performing a DPHH test. Different tests have been performed including the Molisch experiment, Ninhydrin experiment, alkaline reagent experiment, Wagner’s experiment, Froth experiment, Ferric reagent experiment and Salkowski experiment for the detection of phytochemical constituents. The antimicrobial activity of ethanolic abstrac of Citrus limetta (leaves, peel and stem) tested by agar diffusion opposed to various bacterial ATCC cultureswhich reveal topmost zone of hindrance against Enterococcus Faecalis (24 mm) followed by Staphylococcus aureus (34 mm), whereas the minimal sector of hindrance was shown by Bacillus subtilis (14 mm) after 24 and 48t hours of incubation at 37°C. The antioxidant activity results showed that it reduced the firm radical 1-diphenyl-2-picrylhydrazyl (DPPH) to yellow-tint DPPH-H outstretched 75.81% of DPPH rummage effect at its 100% attentiveness compared to vitamin c as testimonial standard being a secure antioxidant indicator. Cytotoxic activities of this plant revealed extraordinary viability of cells which is a novel property examined of this plant. Ethanolic extracts showed positive results against different test performed to check the phytochemical constituents. It was concluded that Citrus limetta ethanolic extract of (leaves peel and stem) possessed a potent antimicrobial, antioxidant and cytotoxic activity and the presence of phytochemical constituents of the plant make it an essential parameter in treatment of different pathological conditions.

Development of a resource-saving technology for the treatment of ferrum-containing wastewater from etching operations

The object of this study is wastewater from chloride and sulfate etching operations. This paper reports results of research on ways to reduce the consumption of chemical reagents in wastewater treatment systems from etching operations. Spent etching solutions are subject to regeneration with return to the production process and partial dosing to the main stream of wastewater. It was found that at a ferrum concentration of 30 g/l in etching solutions, the solution must be treated with an alkaline reagent (10–20 % NaOH) to pH=3.5–4.0 in order to return to the technological process. In this case, the final concentration of ferrum is 11 g/l. The use of hydrogen peroxide (20–40 % H2O2) together with the alkaline reagent makes it possible to increase the degree of extraction by 30 %, that is, the final concentration of ferrum is 8 g/l. When discharging 1 m3 of etching solutions, 0.5 m3 is subject to regeneration and, after mixing with 0.5 m3 of the commercial reagent (HCl) it returns to the technological process. Commercial acid consumption is reduced by 50 %. It was shown that the use of individual flows of waste solutions as a chemical reagent reduces the cost of reagents for their neutralization (saving alkaline reagent is 80 %). Thus, 1.2 kg/m3 of a commercially available reagent (NaOH) is consumed per 1 m3 of solutions (etching and degreasing) after mixing them, and, without mutual neutralization, this consumption is 6 kg/m3. To neutralize etching solutions, it is recommended to carry out the process in the range of pH=6.5–7.5. For a solution in which Fe3+ ions predominate with an initial concentration of 0.53 mol/L, a degree of extraction of 0.9 is achieved, and the total consumption of the reagent (7.1 mol/l) exceeds the stoichiometric one by only 10 %. Deep purification from ferrum-containing impurities using a magnetic device expands the possibilities of practical implementation of further desalting with inverse osmosis.

Физико-химическое моделирование системы ZnSO4-CaO(MgO)-SiO2-H2O

The paper presents the results of zinc precipitation from sulfate solutions with alkaline reagents (serpentinite magnesite and calcium oxide). X-ray diffraction, micromorphological analysis, and thermodynamic modeling revealed the formation of stable metastable silicate zinc-containing phase in the experiment with the use metaserpentine as a reagent. When calcium oxide is used as a reactant, zincite precipitated.

Development of Analytical Methods for the Determination of N-Bromosuccinimide in Different Active Pharmaceutical Ingredients by High-Performance Ion Chromatography with Suppressed Conductivity Detection

Product safety is important for medicines. For drugs on the market, it must be demonstrated that the levels of toxic contaminants are below the permitted limits. These impurities are used as reagents or are generated during synthesis. N-bromosuccinimide is used as a brominating agent in the synthesis of some active pharmaceutical ingredients. The determination of N-bromosuccinimide is difficult due to its high reactivity. In this work, a high-performance ion chromatographic method was developed for the determination of N-bromosuccinimide. The ion chromatographic measurement can be performed in two ways, one involves the assay of the resulting bromide ion and the other is via the assay of the 3-carbamoyl propanoic acid ion produced from the succinimide. Both acid ions were analyzed on an anion exchange column by gradient elution with potassium hydroxide eluent and detection was performed by a suppressed conductivity detector. During the method development, the results showed that the measurement of bromide ion was more selective than the measurement of 3-carbamoyl propanoic acid ion. Two different types of active pharmaceutical ingredients (API), i.e., prasugrel and favipiravir, were chosen to test the developed method and sample preparation. For both APIs, sample preparation was performed in a vial and consists of liquid–liquid extraction with an alkaline reagent. Finally, the anion exchange ion chromatography method was validated at the limit value level, and harmonized with the guidelines. For prasugrel, the quantification limits and the accuracy at the limit level are 7.2 ppm and 96.4%, while for favipiravir these are 7.5 ppm and 114.7%, respectively.