Daniel Mmereki

Vortex-assisted liquid–liquid microextraction using a low-toxicity solvent for the determination of five organophosphorus pesticides in water samples by high-performance liquid chromatography

Vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with UV detection was applied to determine Isocarbophos, Parathion-methyl, Triazophos, Phoxim and Chlorpyrifos-methyl in water samples. 1-Bromobutane was used as the extraction solvent, which has a higher density than water and low toxicity. Centrifugation and disperser solvent were not required in this microextraction procedure. The optimum extraction conditions for 15 mL water sample were: pH of the sample solution, 5; volume of the extraction solvent, 80 μL; vortex time, 2 min; salt addition, 0.5 g. Under the optimum conditions, enrichment factors ranging from 196 to 237 and limits of detection below 0.38 μg/L were obtained for the determination of target pesticides in water. Good linearities (r > 0.9992) were obtained within the range of 1-500 μg/L for all the compounds. The relative standard deviations were in the range of 1.62-2.86% and the recoveries of spiked samples ranged from 89.80 to 104.20%. The whole proposed methodology is simple, rapid, sensitive and environmentally friendly for determining traces of organophosphorus pesticides in the water samples.

Dispersive solid-phase extraction followed by vortex-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge.

A novel dispersive solid-phase extraction combined with vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high-performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean-up of the extract was conducted by dispersive solid-phase extraction using activated carbon as the sorbent. The vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1-undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2-500 ng/g with correlation coefficients (r) of 0.9993-0.9999. The limits of detection were in the range of 0.08-0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.

Hazardous and toxic waste management in Botswana: Practices and challenges:

Hazardous and toxic waste is a complex waste category because of its inherent chemical and physical characteristics. It demands for environmentally sound technologies and know-how as well as clean technologies that simultaneously manage and dispose it in an environmentally friendly way. Nevertheless, Botswana lacks a system covering all the critical steps from importation to final disposal or processing of hazardous and toxic waste owing to limited follow-up of the sources and types of hazardous and toxic waste, lack of modern and specialised treatment/disposal facilities, technical know-how, technically skilled manpower, funds and capabilities of local institutions to take lead in waste management. Therefore, because of a lack of an integrated system, there are challenges such as lack of cooperation among all the stakeholders about the safe management of hazardous and toxic waste. Furthermore, Botswana does not have a systematic regulatory framework regarding monitoring and hazardous and toxic waste management. In addition to the absence of a systematic regulatory framework, inadequate public awareness and dissemination of information about hazardous and toxic waste management, slower progress to phase-out persistent and bio-accumulative waste, and lack of reliable and accurate information on hazardous and toxic waste generation, sources and composition have caused critical challenges to effective hazardous and toxic waste management. It is, therefore, important to examine the status of hazardous and toxic waste as a waste stream in Botswana. By default; this mini-review article presents an overview of the current status of hazardous and toxic waste management and introduces the main challenges in hazardous and toxic waste management. Moreover, the article proposes the best applicable strategies to achieve effective hazardous and toxic waste management in the future.

Waste electrical and electronic equipment management in Botswana: Prospects and challenges.

The management of waste electronic and electrical equipment (WEEE) is a major challenge in developing and transition countries. The paper investigates recent strategies to manage this waste stream in an environmentally sound way. Obsolete electrical and electronic equipment (EEE) are a complex waste category containing both hazardous and valuable substances. Many countries and regions in the world are undertaking extensive scientific research to plan and develop effective collection and treatment systems for end-of-life EEE. In developing countries such as Botswana, effective strategies that cover all stages throughout the lifecycle of products, particularly at the end-of-life, still lag behind. Infrastructure, pre-processing, and end-processing facilities and innovative technologies for end-of-life management of e-waste are noticeably absent due to lack of investment and high costs of its management. The objective of the paper is to present the e-waste situation in Botswana, highlighting (a) measures taken in the form of legislative and policy regulations; (b) existing practices to manage e-waste; and (c) effective solutions for e-waste management in emerging economies. Studies from other countries on e-waste management issues provided insights on the “best” technical and logistical pre-processing and end-processing strategies to treat hazardous waste. The paper also highlights key societal factors that affect successful implementation of cost-effective collection and value recovery of end-of-life EEE. These include unavailability of national “e-waste policy,” absence of formal take-back system, absence of financing and subsidies, inadequate source separation programmes, absence of technical and logistical integration of pre-processing and end-processing facilities, and limited infrastructure and access to technologies and investment. Effective strategies such as an “integrated approach” (mixed options), access to technologies, establishment of pre-processing and end-processing facilities and optimization of logistics, optimizing diversion of e-waste from disposal sites, and investment in e-waste are suggested to manage this complex waste stream in an environmentally sound way. Implications: E-waste management has become a major challenge due to limited infrastructure, innovative technologies, and investment, no comprehensive system of monitoring either its generation or its movement and no coordinated strategic framework of actions to deal with e-waste economically and in a sustainable manner. For better management of EEE at their end-of-life, sustainable and specific practical policies, rules and regulation should be established and applied to all levels of e-waste management, particularly at the post-consumption stage. This paper reviews the current situation of e-waste management in Botswana, with a view towards formulating an effective regulatory and sound waste management strategy as well as the promotion of incentives and environmental sustainability.

Determination of 3,5,6‐Trichloro‐2‐pyridinol, Phoxim and Chlorpyrifos‐methyl in water samples using a new pretreatment method coupled with high‐performance liquid chromatography

A novel low-density solvent-based vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with the solidification of floating organic droplet method coupled with high-performance liquid chromatography was developed for the determination of 3,5,6-trichloro-2-pyridinol, phoxim and chlorpyrifos-methyl in water samples. In this method, the addition of a surfactant could enhance the speed of the mass transfer from the sample solution into the extraction solvent. The extraction solvent could be dispersed into the aqueous by the vortex process. The main parameters affecting the extraction efficiency were investigated and the optimum conditions were established as follows: 80 μL 1-undecanol as extraction solvent, 0.2 mmol/L of Triton X-114 selected as the surfactant, the vortex time was fixed at 60 s with the vortex agitator set at 3000 rpm, the concentration of acetic acid in sample solution was 0.4% v/v and 1.0 g addition of NaCl. Under the optimum conditions, the enrichment factors were from 172 to 186 for the three analytes. The linear ranges were from 0.5 to 500 μg/L with a coefficient of determination (r(2) ) of between 0.9991 and 0.9995. Limits of detections were varied between 0.05 and 0.12 μg/L. The relative standard deviations (n = 6) ranged from 0.26 to 2.62%.

Vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet combined with flame atomic absorption spectrometry for the fast determination of cadmium in water samples.

A novel vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet (VSLLME-SFO) was developed for the fast, simple and efficient determination of cadmium (Cd) in water samples followed by flame atomic absorption spectrometry (FAAS). In the VSLLME-SFO process, the addition of surfactant (as an emulsifier), could enhance the mass transfer from the aqueous solution into the extraction solvent. The extraction solvent could be dispersed into the aqueous phase under vigorous shaking with the vortex. In this paper, we investigated the influences of analytical parameters, including pH, extraction solvent type and its volume, surfactant type and its volume, concentration of chelating agent, salt effect and vortex time, on the extraction efficiency of Cd. Under the optimized conditions, the limit of detection was 0.16 μg/L. The analyte enrichment factor was 37.68. The relative standard deviation was 3.2% (10 μg/L, n = 10) and the calibration graph was linear, ranging from 0.5 to 30 μg/L. The proposed method was successfully applied for the analysis of ultra-trace Cd in river water and wastewater samples.

Dispersive Liquid-Liquid Microextraction Using Low-Toxic Solvent for the Determination of Heavy Metals in Water Samples by Inductively Coupled Plasma-Mass Spectrometry.

A low-toxic dispersive liquid-liquid microextraction (DLLME) combined with inductively coupled plasma-MS was used for preconcentration and determination of Cu, Cr, Cd, Ni, Mn, and Pb in real-water samples. In traditional DLLME analysis, chlorinated solvents have been widely used as extraction solvents. However, these solvents are not environmentally friendly. To overcome this problem, we used a low-toxic bromosolvent (1-bromo-3-methylbutane; lethal concentration, 50%, 6150 mg/kg) as the extraction solvent. To study the effects of different parameters on the extraction efficiency, an orthogonal array experimental design with an L16(4(5)) matrix was used. Under the best experimental conditions (i.e., concentration of complexing reagent 1-(2-pyridylazo)-2-naphthol, 1.5 × 10(-3) mol/L; pH, 7.0; volume of acetone, 0.5 mL; volume of 1-bromo-3 methylbutane, 30 μL; and without salt addition), the enhancement factor ranged from 34 to 40. The linear dynamic range was 1-1000 μg/L with r(2) values of 0.9984-0.9999, and the LODs were between 0.042 and 0.53 μg/L. RSDs (at metal ion concentrations of 20 μg/L, n = 6) were 2.12 to 3.42%. The developed method was successfully applied to the extraction and determination of the mentioned metal ions in real-water samples, and satisfactory results were obtained.

Dispersive solid phase extraction followed by low-toxicity vortex-assisted liquid–liquid microextraction for the determination of organophosphorus pesticides by high-performance liquid chromatography

A simple, rapid and environmentally friendly method for the determination of organophosphorus pesticides (OPPs) in soil and cucumber samples was developed by using dispersive solid phase extraction and low-toxicity vortex-assisted liquid–liquid microextraction (DSPE-LT-VALLME) and high performance liquid chromatography with ultraviolet detection (HPLC-UV). Clean-up of the extract from soil and cucumber was conducted by DSPE using multi-walled carbon nanotubes (MWCNTs) as the sorbent. Parameters that could influence the extraction efficiencies, including the type and volume of extraction solvent, time of the vortex, pH of the sample solution and salt addition, were investigated. The linearity of the method was in the range from 1.0 to 600 ng g−1 with correlation coefficients (r) ranging from 0.9992 to 0.9999. The limits of detection (LODs) were 0.018 to 0.12 ng g−1. The relative standard deviations (RSDs) varied from 1.66% to 3.62% (n = 6), and the enrichment factors (EFs) for the target analytes were in the range of 128–136. Finally, the proposed method has been successfully applied to the determination of target analytes in real samples. The recoveries of the target analytes in soil and cucumber samples were between 83.10% and 101.20%.

The Generation, Composition, Collection, Treatment and Disposal System, and Impact of E-Waste

The problem of e-waste has forced governments of many countries to develop and implement environmentally sound management practices and collection schemes for E-waste management, with a view to minimize environmental impacts and maximize re-use, recovery and recycling of valuable materials. In developed countries, e-waste management is given high priority countries, while in developing countries, it is exa‐ cerbated by completely adopting or replicating the e-waste management of developed countries and several problems including, lack of investment, technological, financial, technically skilled human resources, lack of infrastructure, little available information on the e-waste situation, recovery of valuable materials in small workshops using ru‐ dimentary recycling methods, lack of awareness on the impacts of e-waste, absence of appropriate legislations specifically dealing with e-waste, approach and inadequate description of the roles and responsibilities of stakeholders and institutions involved in e-waste management, etc. This chapter provides the definition of e-waste, and presents information on generation of –andcomposition of e-waste, collection, treat‐ ment, and disposal systems. It also discusses the overview of e-waste collection schemes in different parts of the world with regional focus, and the best current prac‐ tices in WEEE management applied indeveloped and developing countries. It outlines the illegal e-waste trade and illegal waste disposal practices associated with e-waste fraction. In this chapter, the terms “WEEE” and “E-waste” are used synonymously and in accordance to the EU, WEEE Directive.

Healthcare Waste Management Practices in Liberia: An Investigative CaseStudy

Healthcare waste management continues to present an array of challenges for developing countries, and Liberia is of no exception. There is insufficient information available regarding the generation, handling and disposal of health care waste. This face serves as an impediment to healthcare management schemes. The specific objective of this study is to present an evaluation of the current health care management practices in Liberia. It also presented procedures, techniques used, methods of handling, transportation, and disposal methods of wastes as well as the quantity and composition of health care waste. This study was conducted as an investigative case study, covering three different health care facilities; A Hospital, A Health Center and A clinic in Monrovia, Montserrado County. The average waste generation was found to be 0-7 kg per day at the clinic and health center and 8-15 kg per/day at the hospital. The composition of the waste includes hazardous and non-hazardous waste i.e. plastic, papers, sharps and pathological elements etc. Nevertheless, the investigation showed that the healthcare waste generated by the surveyed healthcare facilities were not properly handled because of insufficient guidelines for separate collection, and classification, and adequate methods for storage and proper disposal of generated wastes. This therefore indicates that there is a need for improvement within the healthcare waste management system to improve the existing situation.