Current Analytical Chemistry - Volume 19, Issue 6, 2023

Building mathematical models based on the analysis of physiochemical systems is known as computational modeling. It may be used to combine different types of data and gain a thorough grasp of how they are correlated. Computational modeling techniques cannot replace true experimental techniques or function as a real mechanism. Despite this, they showed to be highly effective at displaying the outcomes for a suggested technique. Nanotechnology is a developing field of producing cost-effective nanomaterials. The toxicity of nano-based products may be significantly affected by the presence of metal impurities and latent waste. The contaminants introduced into the nano-products during manufacturing toxicate the cells. A limited number of techniques for the precise detection of nanotoxicity in nanomaterials has created interest in scientists for the development of newer computational techniques like QSAR. QSAR gives precise results based on ligand descriptors and mathematical algorithms to create functionalized bandwidth that detects toxicity at nano-levels. Now, widespread literature revealed QSAR workflow for the precise detection of various toxicants in nano-materials. The current study focused on the basic principles of QSAR in nanotoxicity predictions along with the applications and future prospects.

The usage of abused illicit drugs remains an increasing challenge for drug regulatory authorities and therefore, it is important to develop advanced sensor technology that able to identify and determine drugs concentration in seized samples, biological fluids and food samples. The World Health Organization (WHO) recommends the usage of narcotic drugs legally for the medical treatments. Thus, many reports indicated that the higher dosage level led to drug addiction and mental disorders in humans. The United States record showed about 0.46 million cases of deaths due to the overdose of opioids-related drugs every year. This review discusses the electrochemical analysis (DPV, CV, EIS spectra, etc.) of various narcotic drugs using electrochemical transducers made of nanomaterials such as gold nanoparticles, single-walled carbon nanotubes, Zn2SnO4/graphene nanocomposite, cysteamine functionalized gold nanoparticle conjugated with an aptamer, etc. There were many challenges reported during the electroanalysis of narcotic drugs. Some of the wearable devices were also made for the sensing of narcotic drugs. Specifically, electro-analysis of nicotine, morphine, codeine and cathonine using 2D nanomaterials and their nanocomposites-based electrochemical sensors fabricated on flexible substrates were discussed. In particular, the linear range of detection, limit of detection (LOD), interference and real-world sample analysis were highlighted. It was concluded that wearable sensors could be used for the monitoring of illicit drugs and their derivatives in day-to-day life.

It is very important to determine the concentration of target substances in food safety, environmental detection, and drug supervision. Caffeine, a natural alkaloid, is widely found in various drinks and drugs. In addition to its beneficial functions, caffeine also has certain negative effects. Therefore, it is very important to determine the concentration of caffeine in drugs, beverages, wastewater, and other media. Among various analytical techniques, electrochemical sensors occupy a special position because of their high efficiency, rapidity, and relative ease to obtain the required preparation and measurement conditions. In the past decades, great progress has been made in the determination of caffeine using graphene oxide (GO) and reduced graphene oxide (RGO) as electrochemical sensor materials. GO and RGO have the advantages of low preparation cost, significant dissolution in polar solvents, such as water, wide working potential range, and relatively high electrochemical inertia in various redox reactions. Moreover, due to π -π interaction and other reasons, their reactivity to caffeine is higher; therefore, GO and RGO applications in caffeine sensors are more popular, and good results have been obtained in selectivity and sensitivity. In this study, the related literature on caffeine in electrochemical sensors preparation with GO and RGO in recent years is reviewed, with the aim of helping researchers working in this research field.

Background: Seventy percent of the Earth is covered by water, out of which only 1% is fresh water. This fresh water can be used for drinking and other domestic uses. However, a drastic increase in the industrial revolution resulted in depletion of the reservoirs and contamination of the potable fresh water. Around 3.4 M deaths per annum occur as a result of waterborne diseases. Objectives: Therefore, the aim of this study is to establish physical, chemical, and biological parameters for evaluating contamination in the drinking water of hospitals in the Bannu and Kohat divisions, Khyber Pakhtunkhwa, Pakistan. Method: Eleven different hospitals were selected for the collection of water samples. Total solids, total dissolved solids, electrical conductivity, and pH were considered significant physical metrics for this study. The essential and heavy metals were also quantified. Furthermore, biological parameters such as Escherichia coli (E. coli) content of drinking water were also studied by using membrane filtration. Results: The results show that E. coli were detected in nine out of the eleven water samples. Moreover, some of the physicochemical parameters were not within guideline limits specified by the World Health and other international organizations. Conclusion: E coli in most of the hospital drinking water was more than the WHO permissible level of the physiochemical parameters. This will have adverse effects on the health of patients which is a serious threat for the population. Therefore, this investigation provides useful information to the government to take special precautions for maintaining the quality of the potable water in government and private hospitals.

Introduction: Cyanide is one of the most commonly present anions in industrial effluents, highly toxic to human and animal life. Therefore, its determination in aqueous media by simple, portable, and quick methods is required. Objective: This study aims to develop a simple and quick method to determine this anion at the micro level in aqueous media without using any expensive instrument. Method: The method is based on treating the microliter sample of aqueous cyanide with the classical Lassaigne’s reagents on a TLC plate. After heating in an oven for a few minutes, a deep blue spot of ferric ferrocyanide complex appeared on the plate. The color depth of the spots was measured by scanning the TLC plate and analyzing the image with an indigenous software package. Result: As a result of fusion with metallic sodium, carbon and nitrogen of the organic compound combine to form cyanide, which first reacts with Fe(II) to form hexacyanoferrate ion [Fe(CN)6]^4- that further combines with Fe(III) to create a neutral deep blue colored coordination complex, ferric ferrocyanide Fe4[Fe(CN)6]3. Discussion: This process converts real-world colors into numeric computer data consisting of rows and columns of pixels. Each pixel will consist of three numeric components, i.e., red, green, and blue. The pixel's color will be one of 16.8 million possible color combinations (256 shades of red, green, and blue each). Conclusion: From the comparison of results obtained by the proposed method and standard ion-selective electrode method, it can be concluded that the former method for determining micro quantities of cyanide in aqueous samples using computational densitometry is a simple, accurate, and adequately precise method without the involvement of sophisticated instrumentation.

Background: A new enrichment and sensitive determination method, which includes HPLCDAD analysis after Magnetic Solid Phase Extraction (MSPE), has been developed for trace analysis of Sibutramine molecules in herbal slimming products. Sibutramine is one of the most adulterated drug molecules in herbal products. Method: In the proposed method, Sibutramine molecules were pre-concentrated by using Fe3O4@MPTMS-Dithizone magnetic sorbent synthesized in our laboratory. Desorption of Sibutramine molecules from the sorbent phase was carried out by using acetonitrile: methanol (1:1) solvent in the presence of pH 8.0 buffer before chromatographic determinations. Results: Analytical parameters of the method, such as linear range, enrichment factor, and determination limit, were determined after optimizing experimental variables such as interaction time, desorption solvent, pH, etc. The sibutramine molecule was analyzed by isocratic elution of acetonitrile and KH2PO4 (pH 3.0, 0.05 M) (40:60) with a DAD detector at 223 nm wavelength. Limit of detection (LOD) value was calculated as 1.43 ng mL^-1. Conclusion: Relative standard deviations (RSD) were below 3.20% for determinations of model solutions, including 100 ng mL^-1 of Sibutramine. Finally, the developed method has been applied to herbal slimming tea samples with quantitative recovery experiments.

Introduction: Mannich base is the result of the three-part chemical reaction known as the Mannich reaction, which includes the amino alkylation of an acidic proton adjacent to a carbonyl group by formaldehyde and either a primary or secondary amine. Method: In a 1L flask, dissolve 28.2 g (0.3 mol) of 2-aminopyridine, and 400 mL of ethanol, then add 32.6 g (0.3 mol) of chloroacetone and put 30 drops of acetic acid. The organic phases are combined and dried with Magnesium sulfate. After solvent evaporation, we have recovered our product which is a 2- methylimidazo [1, 2-a] pyridine product. Result: A C-18 bonded stationary phase provided one significant peak for all of the compounds under examination providing solid proof of the compound purity. This was used to demonstrate the purity of the compounds. Then, the potential enantiomers of these chiral compounds were obtained using the four CSPs. Conclusion: In this study, several novel Mannich bases were prepared. These bases had rendement ranging from 76 to 94.73, and their chiral separation was discussed utilizing four polysaccharide-based CSPs: ChiralpakAS, Chiralcel OD, Chirapak®AS-3R, and Chiralcel OJ.

Background: Plastic pollution has taken over the world. Toxicity of the plastics and other pollutants is enhanced due to the formation of microplastics and nano-plastics that attract Persistent Organic Pollutants (POPs). The need for the treatment of plastic waste in the current scenario led to the rise of various treatment processes. Biodegradation, an eco-friendly approach to eliminate plastics urged to discover plastic-utilizing bacteria and plastic-eating worms. Bacterial degradation of plastics has been extensively studied utilizing the entire microbial community. Hence, the current research focuses on the biodegradation of Low-Density polyethylene (LDPE) using Winogradsky Column constructed using dump yard soil. LDPE degradation was determined using FTIR and GC-MS analysis, which is used to analyze the degradation mechanism of LDPE. Methods: Sample Collection and Column Construction: The soil samples collected from the Chennai dump yard were used to construct Winogradsky columns. The column with LDPE and enrichment sources is used to study LDPE degradation. Analysis of LDPE Degradation: The LDPE sheet after incubation was washed with surfactant and ethanol. The dried sheet was analyzed for weight loss and the metabolites were identified using GC-MS analysis. The GC-MS chromatogram was used to determine the pattern of degradation by the microbial community in the dump yard soil. Results: The mass spectral analysis of GC peaks has been carried out using the electron ionization method, and ions were detected using positive ions scanning mode. The GC peaks appeared at 22.532 and 23.117 min in the control LDPE sheet, which was found to be nonadecane and octacosane, whereas, in the treated LDPE sheet, the GC peaks appeared at 22.467 and 23.062 min. The fragmentation pattern indicates the loss of m/z 14, which confirms the loss of methylene (-CH2-) fragments in alkyl chains. The difference in retention time could be correlated with the increase of CH2 in the alkyl chain length and molecular weight. Higher molecular weight alkanes, such as C16, C18, and C20 above appeared at higher retention times. The presence of longer alkyl chains indicates the LDPE polymer chains. The treated LDPE sample has been analyzed, and the fragmentation pattern indicates the presence of aliphatic chains of C16 or C18. Conclusion: The current study provides an efficient method to utilize the microbial community as a whole to degrade LDPE. The degradation mechanism of LDPE was determined using GC-MS analysis. The high molecular weight polymeric chain was degraded to small chains, and the formation of alcohol indicates the occurrence of terminal oxidation. Hence, this confirms the degradation of LDPE by the microbiome present in the dump yard soil.

Aim: The current research aims to establish a stability-indicating analytical method (SIAM) for the quantification of evodiamine (EVO), characterization of its degradation impurity, and establishment of possible degradation pathways. Background: None of the degradation impurities of EVO is known and the mechanism of their formation has not been reported in any literature to date. Moreover, a SIAM for EVO is not available in any public domain. Objective: The objective of this study is to characterize the degradation impurity of EVO by LC-MS/MS, proposing its molecular structure, identifying possible degradation pathways of generation of its impurity, and establishing a SIAM. Method: To assist future product development, a degradation study of EVO was performed and an RPHPLC- based SIAM was developed. The major degradation product was characterized by LC-Q-TOFMS/ MS. In addition, in silico toxicity prediction was performed using the ProTox-Ц#134;I toxicity predictor. Result: The method was found to be linear, accurate, precise, and robust over the range of 12.5 to 100 μg /mL of EVO. The method met all the acceptance criteria as specified in the ICH guideline. Only one degradation product (9% of the drug area) of EVO was generated in acidic hydrolytic conditions. The degradation product was found to be potentially inactive for hepatotoxicity and immunotoxicity, with a confidence score of more than 0.7 (70%). Moreover, the confidence score for carcinogenicity, mutagenicity, and cytotoxicity was less than 0.7, indicating it was moderately inactive for these toxicities. Conclusion: The molecule was found to be stable in the majority of the tested stress conditions. However, the degradation product generated in acidic hydrolytic stress was characterized using LC-Q-TOF-MS/MS, which was unknown to date. The novelty of this research can be justified by the unavailability of any SIAM of EVO and the absence of any report on its susceptibility to degradation in the presence of different potential stressors. Moreover, the potential toxicity of the molecule and its impurity was not known previously. The reported degradation impurity may be useful to set the quality control acceptance criteria for EVO. Additionally, pharmaceutical industries and research laboratories may use the developed method for the analysis of quality control and stability samples of EVO.