Applications Of Comprehensive Screening Techniques For The Broad-spectrum Extraction Of Organic Pollutants In Water

Along with the advancement of science and technology,the production of chemicals has also increased at an exponential rate over the past few decades.The improper disposal of everyday products that contain all kinds of organic compounds led to the occurrence of pollution in our environment,especially the aquatic environment.Humans are highly exposed to these distinctive types of organic pollutants in the environment,particularly those persistent,bioaccumulative and toxic organic pollutants that may bioaccumulate and biomagnify along the food chain.Eventually,these wide varieties of organic contaminants will bring about detrimental human health impact such as cancer,immunity disorder and neurotoxicity.In order to constantly monitor the occurrence,distribution,concentration and transportation pathway of the massive amount of organic pollutants in the aquatic environment,broad-spectrum analysis is indispensable.Regardless of chromatographic and mass spectrometric technologies at present day,these cutting-edge instruments are fully equipped with the high throughput,excellent precision,rapid and comprehensive abilities for realising the qualitative and quantitative analysis of various compounds.The ultra-high resolution,outstanding resolution power,broad mass range,high peak capacity,wide dynamic range and speedy scan rate of the detection instruments meets the requirement of broad-spectrum analysis.Yet,sample pre-treatment methods are still a bottleneck issue of the analytical system due to its laborious and inefficient shortcomings,hence hindering the progression of achieving broad-spectrum extraction and separation.In order to effectively and efficiently screen multiple organic pollutants in the environment,it is mandatory to develop sample pre-treatment methods that are furnished with rapid,precise and broad-spectrum extraction features,which are also compatible with the state-of-the-art detection system.In the present study,three highly efficient sample pre-treatment techniques that aimed to realise broad-spectrum extraction were proposed and systematically evaluated.The analytical strategy for achieving broad-spectrum extraction of this research was greatly dependent on the simultaneous analysis of organic pollutants with different physicochemical properties and the requirement of large sample volume.Gas Liquid Microextraction(GLME)method was introduced to analyse volatile and semi-volatile organic compounds based on the difference in boiling points and volatility;carbon nanofibers/carbon fibers liquid phase microextraction technique(CNFs/CFs-LPME)was proposed for the rapid extraction of organic pollutants across wide polarity and volatility,and lastly the ultrasonication-assisted liquid-liquid spray extraction(UA-LLSE)was established for the broad-spectrum extraction of organic compounds in large volume of water samples(>50 L).The feasibility of broad-spectrum extraction by using these three methods were intensively assessed based on the distinctive extraction mechanisms,and the key elements of these techniques were explored by utilising scientific basis.The parameters for each of the proposed sample pre-treatment techniques were sequentially optimised,and these methods were methodically validated by using genuine water samples.1)It has been proven that a variety of volatile and semi-volatile organic pollutants can be simultaneously determined by using the GLME method.The two most determining parameters(extraction temperature and extraction time)that may affect the analytical performance of GLME were examined,and the theoretical explanations proved that this technique can realise exhaustive and broad-spectrum extraction.Based on the extraction mechanism,under a constant flow rate of inert gas being introduced into the extraction system plus the high temperature and needed time would break the partition coefficient between the sample matrix and headspace,hence the enhanced desorption rate facilitates the exhaustive extraction in the GLME method.Under optimised extraction conditions(extraction temperature of 300? and extraction time of 5 min),GLME can rapidly,effectively and exhaustively extract a wide array of volatile and semi-volatile organic compounds with excellent accuracy(recoveries of 65.53-95.12%),precision(RSD%of 1,5-11.3%)and sensitivity(LODs in between 0.01-1.05 ng mL-1).Therefore,GLME certainly meets the requirement of realising broad-spectrum analysis,in which it can be a promising tool as a screening approach to extract an enormous amount of organic pollutants in the aquatic environment,as well as in different environmental and biological matrices.2)With regards to CNFs/CFs-LPME technique,the ideology of achieving LPME on the surface of CNFs/CFs materials provides a broader perspective of microextraction approach in fulfilling the goal of broad-spectrum extraction.Different parameters of the CNFs/CFs-LPME method including extraction solvent,extraction mode,extraction time,desorption time and salinity were thoroughly investigated.The significance of immobilising organic solvent on the carbonaceous material surface,the influences of vortex agitation on rate of mass transfer and the impact of salting-out effect on extraction performance were orderly discussed in the parameter optimisation section.Eventually,the analytical performance was justified before applying it to analyse organic pollutants across wide polarity with Log Kow in between 0.13 to 8.1.Analytical results indicated the recoveries of all selected analytes ranged from 68.9%to 107.6%,RSD%values less than 17.9%and limit of detections(LODs)of 0.04-9.72 ng mL-1,justifying the noteworthy broad-spectrum extraction performance of the CNFs/CFs-LPME technique.Apart from its capability to achieve broad-spectrum extraction of organic compounds with extensive polarity,the strengths of the CNFs/CFs-LPME method is definitely its speediness which only requires a min of extraction time and another min of desorption time for analysing 1 mL of water sample.It exhibits the potential to be expanded to analyse a higher volume of water samples,thus broadening its applicability and practicality in the field of green analytical chemistry.3)In terms of UA-LLSE,it possesses similar application as the CNFs/CFs-LPME method to achieve broad-spectrum extraction of organic pollutants with wide polarity.The main difference is that the UA-LLSE is designed for extracting large volume of water due to the reason that numerous organic contaminants,especially emerging contaminants of concern,exist in ultra-trace level in the aquatic environment.Consequently,the analysis of small volume is unable to meet the detection limit,which highlighted the significance of analysing high-volume water samples to reflect the actual occurrence of organic pollutants in the real environment.The main interrelationships between atomisation effects,interfacial area,collision frequency,penetration length,size of water microdroplets and rate of mass transfer for the UA-LLSE technology were meticulously explored.The UA-LLSE method showed LODs in between 0.21-22.73 ng L-1,up to par recoveries(in the range of 66.89 to 110.42%)and significant precision(RSD%recorded in between 1.96 to 13.56%)for simultaneously analysing multi-class organic pollutants,which verified the analytical performance of the UA-LLSE.Therefore,the UA-LLSE method helps to avoid false negative analytical data by prevent from overlooking the true occurrence and ultra-trace concentration of organic pollutants in the water,hence this technique assists in providing robust scientific data that reflects the actual pollution status of the aquatic environment.In a nutshell,this study broadens the values and applicability of each of these three sample pre-treatment techniques based on their unique analytical strengths,which can avoid the possible errors that brought about by conventional labour-intensive methods.In contrast to the development of existing analytical techniques that centre around targeted adsorption or extraction which might be infeasible to simultaneously analyse large amount of multi-class organic pollutants with wide polarity,the methods proposed in this study aim to accomplish broad-spectrum and non-targeted analysis.Based on the exhaustive extraction property of GLME method to analyse volatile and semi-volatile organic pollutants plus the "like dissolve like" mechanism of the CNFs/CFs-LPME and UA-LLSE methods,the broad-spectrum extraction of organic pollutants across different physicochemical properties in large quantity of waters can be accomplished.In this case,the development of these sample pre-treatment techniques facilitates the implementation of target screening,suspect screening and non-target screening analyses.The unique merits of this study are the utilisation of micro-volume organic solvents for broad-spectrum extraction of micro-or macro-level samples,what is more,the analysis of large quantity is also achievable.The analytical approaches proposed in this study help to solve the bottleneck problems of laborious and inefficient sample pre-treatment methods,and another notable advantage of these technologies is their potential,feasibility and practicality for on-site sampling and extraction.Ultimately,these analytical methods provide essential technical framework for the precise environmental and toxicological assessment on the synergistic effects of multi-class organic pollutants in the realm of environmental chemistry;supply fundamental ideology for the on-site food quality inspection services in the field of food safety;as well as propose an on-ship sampling and extraction technique for meeting the needs of expeditions in remote areas in order to monitor or examine the pollution condition and transformation pathways of ultra-trace organic pollutants in the global circulation of ocean waters.