Chemical Research Laboratory Research Articles

Urinary Thioproline and Thioprolinyl Glycine as Specific Biomarkers of Formaldehyde Exposure in Humans.

Assessment of personal formaldehyde (FA) exposure is most commonly carried out using formate as a biomarker, as it is the major product from FA metabolism. However, formate could also have originated from the metabolism of other endogenous and exogenous substances or from dietary intake, which may give rise to overestimated results with regard to FA exposure. We have developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with an isotope-dilution method for rigorous quantitation of two major urinary FA conjugation products: thioproline (SPro) and thioprolinyl glycine (SPro-Gly), formed in the reaction between FA and endogenous cysteine or cysteinyl glycine, respectively, as marker molecules to assess personal FA exposure. Using this newly developed method, we measured the FA exposure levels in cigarette smokers, occupants of a chemistry research laboratory and typical domestic household, and visitors to a Chinese temple with a Pearson correlation coefficient greater than 0.94, showing a strong linear correlation between urinary adduct levels and the airborne FA level. It is believed that quantitation of urinary SPro and SPro-Gly may represent a noninvasive, interference-free method for assessing personal FA exposure.

Organotoxic Effect of Aqueous Extract of Justicia secunda Vahl. Leaf in Wistar Rats

Aims: Justicia secunda is a widely distributed plant that is used in the traditional improvement of well-being and treatment of several illnesses and diseases, including anemia. There is limited research on the effect of extracts of the plant on body and organ weights and their effects on organ architecture.
 Study Design: This was a laboratory-based study.
 Place and Duration of Study: The study was conducted at the Chemistry and Biochemistry Resources Research Laboratory of the Department of Chemistry and Biochemistry of Hallmark University, Ijebu-IItele, Ogun State, Nigeria, from July 2021 to September 2022.
 Methodology: This research therefore investigated the toxicity of an aqueous extract of J. secunda leaf on selected organs in male Wistar rats. Mature male rats (15) were divided into three groups (n = 5): Group I (the negative control) received distilled water; Group II and Group III received 200 and 300 mg/Kg doses of the extract, respectively, via oral route, once daily for 14 days. The rats were weighed before being sacrificed; the weights of the kidneys, liver, heart, and spleen were also determined, and histological analysis was carried out on the heart, kidneys, and liver.
 Results: There was significant (p<0.001) concentration-dependent reduction in body weights with hepatomegaly in the extract-administered rats. The kidneys of Group III rats were significantly (p<0.05) larger than those of the negative control group. Histology revealed severe vascular congestion and edema in the liver of Group III rats and inflammation in the hearts of Group II rats.
 Conclusion: This study shows that repeated usage of the aqueous extract of Justicia secunda leaf should be done with caution due to its negative effects on the liver and the heart in rats.
 Keywords: Justicia secunda, Hepatomegaly, vascular congestion, weight-reduction, extract inflammatory, toxicity.

Integrating Ultrafiltration Membranes with Flocculation and Activated Carbon Pretreatment Processes for Membrane Fouling Mitigation and Metal Ion Removal from Wastewater.

The presence of metal ions in an aqueous medium is an ongoing challenge throughout the world. Processes employed for metal ion removal are developed continuously with the integration of these processes taking center stage. Herein, an integrated system consisting of flocculation, activated carbon (AC), and an ultrafiltration (UF) membrane was assessed for the removal of multiple metal ions contained in wastewater generated from a university chemistry research laboratory. The quality of the wastewater was established before and further determined after treatment with inductively coupled plasma optical emission spectrometry (ICP-OES) for metal content, total dissolved solids (TDS), turbidity, electrical conductivity (EC), and pH. Assessing the spent AC indicated minimal structural changes, indicating a potential for further reuse; for instance, the BET for both the pristine and spent AC exhibited type I isotherms with a mesoporous structure, indicating no major structural changes due to metal complexation. The relative performance of the integrated system indicated that the use of flocculation improved the water quality of metal-laden wastewater for safe disposal. The integrated treatment systems exhibited high removal efficiencies between 80 and 99.99% for all the metal ions except for Mn (<0.008 mg L-1) and Cr (<0.016 mg L-1) both at ca. 70%, indicative of the positive influence of the polyelectrolyte in the treatment process. The fabricated UiO-66-NH2@GO membranes (Z4 and Z5) exhibited high fouling resistance and reusability potential as well as relatively high pure water flux. Consequently, the integrated process employed for the treatment of laboratory metal-containing wastewater is promising as a generic approach to improving the quality of metal-containing wastewater to meet the standards of discharging limits in South Africa.

Skill generalization of tubular object manipulation with tactile sensing and Sim2Real learning

Tubular objects such as test tubes are common in chemistry and life sciences research laboratories, and robots that can handle them have the potential to accelerate experiments. Moreover, it is expected to train a robot to manipulate tubular objects in a simulator and then deploy it in a real-world environment. However, it is still challenging for a robot to learn to handle tubular objects through single sensing and bridge the gap between simulation and reality. In this paper, we propose a novel tactile–motor policy learning method to generalize tubular object manipulation skills from simulation to reality. In particular, we propose a Sim-to-Real transferable in-hand pose estimation network that generalizes to unseen tubular objects. The network utilizes a novel adversarial domain adaptation network to narrow the pixel-level domain gap for tactile tasks by introducing the attention mechanism and a task-related constraint. The in-hand pose estimation network is further implemented in a Reinforcement Learning-based policy learning framework for robotic insert-and-pullout manipulation tasks. The proposed method is applied to a human–robot collaborative tube placing scenario and a robotic pipetting scenario. The experimental results demonstrate the generalization capability of the learned tactile–motor policy toward tubular object manipulation in research laboratories.

Front Cover: Evolution of Chemical Research in Nice, Côte d′Azur: From Early Laboratories to the ‘Institut de Chimie de Nice’(ChemPlusChem 6/2022)

The cover picture shows the Institut de Chimie de Nice (ICN), the chemistry research laboratory of the Université Côte d'Azur and the CNRS, which is located in the Parc Valrose in Nice, France. One-hundred chemists work at the ICN, and are organized in four research teams: aroma, biomedical, radio-, and material chemistry. This Editorial summarizes the history and current research interests of the ICN. The ICN celebrates its tenth anniversary in 2022, and more details found in the ICN Special Collection organized for this occasion. The image shows the architect's impression of the ICN building after renovation in 2023. Image credit: Cabinet d'architecture Kardham and Fabien Fontaine-Vive.

Novel MgFe2O4-CuO/GO heterojunction magnetic nanocomposite: Synthesis, characterization, and batch photocatalytic degradation of methylene blue dye

Methylene blue (MB) utilized in chemical industries and research laboratories, produces a considerable amount of wastewater and causes water pollution even at low concentration. In the present work, novel low bandgap MgFe2O4-CuO/graphene oxide nanocomposite was used as a heterojunction magnetic nanophotocatalyst to photodegrade MB in simulated wastewater. The photocatalyst was synthesized via a microwave-ultrasonic route and characterized by a group of spectroscopic techniques. The synthesized photocatalyst had a specific surface area of 96.12 m2 g−1, pore volume of 0.0521 cm3 g−1, and pore diameter of 2.90 nm. Batch photocatalytic degradation of MB dye was performed at 25 °C under ambient sunlight, and carefully optimized to obtain maximum photodegradation efficiency. Under optimal conditions, the synthesized photocatalyst demonstrated superior degradation efficiency reaching 98.8% within 27 min. Recyclability studies showed that the synthesized photocatalyst had a very good stability and reusability up to four cycles.

A new approach for explosion accident prevention in chemical research laboratories at universities

Over the years, many accidents have occurred during chemical experiments in laboratories around the world. However, the methods of investigating and analysing accidents that have occurred at universities have not been consolidated, and the lessons learned from these accidents have not been shared. In this study, accident investigation reports of explosions in chemistry laboratories at two universities were analysed with an analysis tool based on the software/hardware/environment/liveware (SHEL) model. As a result, university accidents were classified as epidemiological models, and it became clear that the contributing factors to the accidents, which were investigated and analysed using the SHEL model, can be used as learning experiences and therefore applied for the prevention of accidents at other universities. Universities around the world need to come together to formulate research and analysis methods, rules for creating accident reports, etc. and provide a place for sharing information that will enable them to make use of the lessons learned from all kinds of accidents.

What to Expect When Expecting in Lab: A Review of Unique Risks and Resources for Pregnant Researchers in the Chemical Laboratory.

Pregnancy presents a unique risk to chemical researchers due to their occupational exposures to chemical, equipment, and physical hazards in chemical research laboratories across science, engineering, and technology disciplines. Understanding “risk” as a function of hazard, exposure, and vulnerability, this review aims to critically examine the state of the science for the risks and associated recommendations (or lack thereof) for pregnant researchers in chemical laboratories (labs). Commonly encountered hazards for pregnant lab workers include chemical hazards (organic solvents, heavy metals, engineered nanomaterials, and endocrine disruptors), radiation hazards (ionizing radiation producing equipment and materials and nonionizing radiation producing equipment), and other hazards related to the lab environment (excessive noise, excessive heat, psychosocial stress, strenuous physical work, and/or abnormal working hours). Lab relevant doses and routes of exposure in the chemical lab environment along with literature and governmental recommendations or resources for exposure mitigation are critically assessed. The specific windows of vulnerability based on stage of pregnancy are described for each hazard, if available. Finally, policy gaps for further scientific research are detailed to enhance future guidance to protect pregnant lab workers.

Pengaruh Ukuran Partikel dan Rasio Bahan Terhadap Pelarut Air pada Distilasi Minyak Atsiri Temulawak

&lt;p&gt;Javanese turmeric (Curcuma xanthorrhiza) essential oil is one of the curcuminoids sources that are widely used in the food and health industries. Temulawak oil extraction usually uses ethanol as a solvent which is relatively less safe for health. This study aimed to evaluate the effect of particle size and the ratio of materials to water solvents in the distillation process of Javanese turmeric essential oil. The experiment was conducted at the Chemical Engineering Research Laboratory, Muhammadiyah University, Surakarta. The treatments tested were the powder size (20, 40, 60, dan 140 mesh), the ratio of material to water solvent (w/v) consisted of 100:800, 150:750, 200:700, and a distillation time of 3 hours at a constant temperature of 100oC with an interval of distillation duration of 0.5; 1; 1.5; 2; 2.5; and 3 hours. The parameters observed were the essential oil quality: organoleptic, refractive index, pH, mass or volume of the oil produced, and curcuminoid compounds using the GC-MS method. The maximum yield of Javanese turmeric essential oil (18.01g) was obtained at a particle size of 140 mesh with a distillation duration of 1.5–2 hours, and the ratio of raw material to solvent 100:800 (g.ml-1). Based on the GCMS analysis, the highest components in the Javanese turmeric essential oil were α-curcumin (42.17%) and α-cedrene (11.14%). The results indicated that the distillation process of Javanese turmeric oil using water as a solvent can be used as an alternative to substitute ethanol as a solvent.&lt;/p&gt;

Smoking, chromosomal aberrations, and cancer incidence in healthy subjects

Chromosomal aberrations (CAs) in peripheral blood lymphocytes can be used as biomarkers of cancer risk. Cytogenetic tests were conducted on 2396 healthy Hungarian individuals and cancer incidence was followed up from 1989 to 2018. Venous blood samples were obtained from the subjects and metaphases from lymphocyte cultures were prepared. We compared the CA frequencies of the various smoking (1−5; 6−10; 11−19; or 20−40 cigarettes/day) and exposure (irradiation; chemical industry; chemical research laboratory) groups. Chromatid break (p = 0.0002), total aberration (p = 0.002), and aberrant cell (p = 0.001) frequencies were higher in smokers than in non-smokers. For very heavy smokers, total CAs were significantly higher than for non-smokers (<0.001) or less intensive smokers (p = 0.003−0.0006). Intensity of smoking was a predictor of chromosomal aberrations, while duration was not. During follow-up, 177 (7.3 %) cancer cases were found. A Cox-regression model showed that subjects with cell values ≥2 CAs developed cancer more frequently (hazard ratio = 1.39; 95 % CI, 1.02–1.90). The relative risks of cancer were 1.06 (95 % CI 0.53−2.06) for light smokers and 1.74 (95 % CI 1.08−2.77) for very heavy smokers. The distributions of cancer sites showed differences between smoker and non-smoker groups: in male smokers, lung cancer, in non-smokers, prostate, and in females (both groups) breast cancer were most common. Cancer incidence correlated with chromosome aberrations; smoking was not a confounder in this relationship.

Augmented Titration Setup for Future Teaching Laboratories

Teaching laboratories are designed to educate students on basic theories and techniques through guided laboratory experiments. As advances in automation revolutionize research chemistry laboratories, teaching tools can advance to reflect these changes. In this study, we integrated several programmable instruments, including automated pumps for liquid transfer, into an augmented titration setup that can be operated remotely. Our setup empowers students to learn the conceptual, technical, and practical aspects of titration by leveraging laboratory automation tools. Our system uses Siri as a speech recognition tool and the Python programming language to develop action routines for titration uses. The application of Siri provides a smooth user-to-instrument experience, and the use of Python allows coders to effectively develop and maintain the workflow. Three chemistry professors were invited to participate in usability tests of the system using a mobile device. Their positive feedback highlights the promise of our system as a valuable addition to undergraduate chemistry teaching laboratories. This titration setup addresses accessibility challenges and distance learning requirements for chemical education. Further, our tool introduces students to the type of automated experimentation that is emerging as the modern standard in chemistry research laboratories.

GC-MS Analysis and Antimicrobial Spectrum of Stem Bark Extracts of Ficus sycomorus

Aim: This work investigated the gas chromatography-mass spectroscopy of methanolic extract and antimicrobial spectrum of acetone and aqueous crude extracts of Ficus sycomorus stem bark.&#x0D; Place and Duration of the Study: Department chemistry research laboratory and microbiology laboratory, Yobe State University, Damaturu between April 2019 and August, 2019.&#x0D; Methodology: Pure isolates of Staphylococcus aureus, Salmonella typhi, Shigella dysentariae, proteus spp, Pseudomonas auruginosa, Escherichia coli, Bacillus subtilis, Klebsiella pneumonia and a fungi, Candida albicans were collected from National Veterinary Research Institute (NVRI), Vom, Plateau State. The plant was collected and the extract was used in preliminary phytochemical screening, GC-MS analysis and reconstituted for antimicrobial activities testing.&#x0D; Results: The preliminary phytochemical screening revealed presence of saponin, flavonoids, alkaloids, carbohydrates, cardiac glycoside and tannin. GC-MS analysis revealed the presence of heterocyclic members of pyrazole, imidazole, triazole, thiazole and 1, 3-Benzenedicarboxylic acid, bis (2-hethylhexyl) ester. Acetone extract showed the greatest antimicrobial activity against Bacillus subtilis, Pseudomonas aeruginosa, Proteus mirabilis and Shigella spp while the aqueous extract produced antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia and Candida albicans. Both acetone and aqueous extracts of both stem bark extracts did not exhibit any activity against Escherichia coli. All the extracts were tested at 100mg/ml concentration. The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) (125 – 250 mg/ml) of both extracts were higher than those of ciprofloxacin (5.0 mg/ml).&#x0D; Conclusion: There is scientific basis for the uses of F. sycomorus in traditional medicine for the treatment of various diseases as prescribed earlier on and stronger basis for recommendation for its cautious use for the presence of 2-ethylhexyl which could be Carcinogenic. This is first study to identify 2-ethylhexyl from F. sycomorus stem bark extract and recommend cautious use.

Evaluation of Peptide/Protein Self-Assembly and Aggregation by Spectroscopic Methods.

The self-assembly of proteins is an essential process for a variety of cellular functions including cell respiration, mobility and division. On the other hand, protein or peptide misfolding and aggregation is related to the development of Parkinson’s disease and Alzheimer’s disease, among other aggregopathies. As a consequence, significant research efforts are directed towards the understanding of this process. In this review, we are focused on the use of UV-Visible Absorption Spectroscopy, Fluorescence Spectroscopy and Circular Dichroism to evaluate the self-organization of proteins and peptides in solution. These spectroscopic techniques are commonly available in most chemistry and biochemistry research laboratories, and together they are a powerful approach for initial as well as routine evaluation of protein and peptide self-assembly and aggregation under different environmental stimulus. Furthermore, these spectroscopic techniques are even suitable for studying complex systems like those in the food industry or pharmaceutical formulations, providing an overall idea of the folding, self-assembly, and aggregation processes, which is challenging to obtain with high-resolution methods. Here, we compiled and discussed selected examples, together with our results and those that helped us better to understand the process of protein and peptide aggregation. We put particular emphasis on the basic description of the methods as well as on the experimental considerations needed to obtain meaningful information, to help those who are just getting into this exciting area of research. Moreover, this review is particularly useful to those out of the field who would like to improve reproducibility in their cellular and biomedical experiments, especially while working with peptide and protein systems as an external stimulus. Our final aim is to show the power of these low-resolution techniques to improve our understanding of the self-assembly of peptides and proteins and translate this fundamental knowledge in biomedical research or food applications.

Antioxidant assessment of characterised essential oils from Calophyllum inophyllum Linn using 2,2-diphenyl-1-picrylhydrazyl and hydrogen peroxide methods

Background: Oxidative stress is a multifactorial global health disorder that disrupts all levels of cell function. Therefore, therapeutic intervention using reliable, affordable and non-toxic natural sources is crucial. Aim: The aim of this article was to determine the chemical constituents and antioxidant activity of 10 essential oils (EOs) from Calophyllum inophyllum Linn using 2,2-diphenyl-1- picrylhydrazyl (DPPH) and hydrogen peroxide (H 2 O 2 ) methods. Setting: Plant sample was collected at the Botanical Garden, University of Ibadan, Nigeria. Extractions and antioxidant assay were performed at the Organic Chemistry Research Laboratory, University of Ibadan, Nigeria. Gas chromatography-mass spectrophotometry (GC-MS) analysis was carried out at the School of Pharmacy, University of Camerino, Italy. Methods: The chemical constituents were determined using GC-MS. The oils were extracted using an all-glass Clevenger-type apparatus and the antioxidant activity was determined using DPPH and hydrogen peroxide assays. Results: A total of 102 compounds were identified in EOs from C. inophyllum Linn, which are mostly monoterpenes, sesquiterpenes and their oxygenated derivatives. The oils exhibited concentration-dependent activity with reference to standard synthetic antioxidants. Root wood had the highest antioxidant activity with the half maximal inhibitory concentration (IC 50 ) of 3.19 mg/mL compared to ascorbic acid (2.84 mg/mL) and butylated hydroxyl anisole (BHA) (2.97 mg/mL). In the H 2 O 2 antioxidant assay, root wood had the highest antioxidant activity with IC 50 of 2.78 mg/mL compared to ascorbic acid (2.20 mg/mL) and BHA (2.92 mg/mL). Conclusion: The in vitro chemical compositional analysis of EOs from C. inophyllum Linn confirms the presence of compounds responsible for the antioxidant properties of the plant.

The Effect of Addition of Nilem Fish Protein Concentrate Flour on the Proximate Characteristics of Mochi Cake

Nilem fish (Osteochilus hasselti) is a type of freshwater fish that is widely farmed in West Java. Another application of nilem fish is made into fish protein concentrate (FPC) flour. The addition of fish protein concentrate flour to the mochi cake can affect the proximate characteristics. This study aims to determine the proximate characteristics of mochi cake added by nilem fish protein concentrate flour. This research was conducted from August 2019 - January 2020 at the Laboratory of Fisheries Product Processing, Faculty of Fisheries and Marine Sciences, and the Chemical Research and Services Laboratory, Basic Science Service Center (PPBS), Padjadjaran University. The method used in this research was experimental with two treatments, that were the addition of 0% and 4.5% nilem fish protein concentrates from white glutinous rice flour was used. The parameters observed were proximate characteristics including carbohydrate, water, protein, fat, and ash content. The results showed that mochi cake with the addition of 4.5% of nilem fish protein concentrate had proximate characteristics namely carbohydrate content 59.57%, water content 29.93%, protein content 8.71%, fat content 1.41%, and ash content 0.38%.

Kinetic study of removal heavy metal from aqueous solution using the synthetic aluminum silicate

One of the problems that most affect humanity today is the wastewater discharge into different water bodies. It was estimated that more than 7 million tons of wastewater are generated worldwide and are discharged into rivers, lakes, and reservoirs. Among the most dangerous wastewaters are those from inorganic chemistry research laboratories, mainly due to heavy metals. These problems have become a highly relevant topic, and numerous researchers have tried to design wastewater treatment systems that will deal more efficiently with heavy metals elimination. In this work, the synthesis, characterization, and evaluation of hydrated aluminium silicate were performed as alternative wastewater treatment from chemistry research and teaching laboratories. The compound obtained was Al_2O_33SiO_2H_2O, which was characterized by the determination of its physicochemical properties. These revealed a low density, very porous material, with low crystallinity, strong chemical resistance, a large surface area, and a high apparent ionic exchange capacity. Absorption kinetics studies of heavy metals in aqueous solutions, through more widespread models, have demonstrated that Al_2O_33SiO_2H_2O has excellent properties as absorbents of this material. The amorphous hydrated aluminium silicate achieves a decrease in the concentration of all the metal ions studied, reducing them to discharge levels permissible.

Synthesis and Use of a Nickel Oxidation Catalyst Using Glove Box Methods

The ability to perform air-free chemistry and catalytic reactions on an NMR tube scale are valuable skills in chemistry and not often included in undergraduate chemistry curriculum. This laboratory experiment provides students experience in synthesizing the metal complex, Ni(dcpe)(CH3CN)2(BF4)2 (dcpe = 1,2-bis(dicyclohexylphosphino)ethane), inside an inert atmosphere glovebox, performing a catalytic alcohol oxidation reaction on a microscale, and monitoring the reaction progress by 1H NMR spectroscopy. This activity has been employed in the Advanced Inorganic Chemistry course at Wabash College for three years. The reactions have proven to be reliable, and the students have gained valuable experience using advanced techniques common in inorganic chemistry research laboratories.

Comparative Statistical Analysis of Two Different Methods for Risk Assessment in Chemical Research Laboratory

Bu calismada onemli bir universitemizin kimyasal maddelerle calisma yapilan arastirma laboratuvari icin Fine-Kinney ve L Tipi (5x5)Matris risk analiz metotlari kullanilarak risk degerlendirmesi yapilmistir. Risk degerlendirmesi yapilan ortamin laboratuvar olmasi nedeniyle surekli farkli materyallerle calisma yapilmaktadir. Calisma yontem ve teknikleri, kullanilan kimyasal maddelerin turu, duzeyi, dozu, maruziyet sureleri degisiklik gosterebilmektedir. Bu durum her yeni deneysel calisma icin tehlike ve risklerin yeniden belirlenmesini gerektirmektedir. Risk degerlendirme ile tehlikeli durum ve tehlikeli hareketlerin belirlenmesi, onem siralamasinin olusturulmasi, karar verilecek duzeltici onleyici faaliyetlerin belirlenmesi buyuk oneme sahiptir. Calismamizda bu sureclerin tamami goz onunde bulundurulmus ve risk analizi sonuclari Cohen Kappa istatistiksel metodu uygulanarak karsilastirilmistir. Istatistiksel analiz sonucunda ozellikle tehlikeli ve cok tehlikeli sektorlerde tercih edilmesi bakimindan etkin olan Fine-Kinney metodu pozitif yonleriyle on plana cikmistir.

Utilization of Natural Coagulant Substance (Tamarind and Winged Bean Seed) on the Quality of Tofu Wastewater in Muntilan, Magelang

The aim of this study is to determine the effect of various mass in tamarind and winged bean seeds on pH, TDS, and COD in tofu factory wastewater. The research was conducted at the Chemistry Research Laboratory of FMIPA UNY in December 2018. The results showed that the addition of various mass in tamarind and winged bean seeds as much as 7, 9, and 11 grams of tofu factory wastewater had an effect on pH which increased from the initial condition of 2.5 to 2.6; 2.7; 2.8 in tamarind seeds, and 2.8; 2.9; 3.0 on winged beans. The COD test increased from the initial condition of 6619.20 mg / L to 7312, 64; 7880, 00; 8195.20 mg / L in tamarind seeds, and 9140.80; 10464.64; 9329.92 mg / L in winged bean seeds which have decreased again in the addition of 11-gram coagulant substance mass. TDS test has increased from the initial conditions of 1512 mg / L to 1715; 1736; 1848 mg / L in tamarind seeds, and 1890; 1988; 1855 mg / L in winged bean seeds.

Microwave-assisted Multi-component Domino Reaction for the Green Synthesis of Novel Benzo[a]pyrano[3',4':5,6]pyrano[2,3-c]phenazines Using H3PW12O40 as Efficient, Cost-effective and Recyclable Catalyst

In recent years, green chemistry techniques have attracted considerable attention in the chemical industry and academic research laboratories due to environmental, health, and economic benefits.1–5...