Establishment And Application Of A Comprehensive Identification Strategy For OPTEs In Soil Samples From Typical Regions

In recent years,organophosphate triesters（OPTEs）have been commonly utilized as both flame retardants and plasticizers in consumer and industrial products due to their excellent flame retardant or plasticity performance,and have been detected in different environmental matrices or organisms.However,current environmental monitoring studies are generally confined to several target OPTEs,and there is a lack of strategies for comprehensively screening all potential OPTEs in environmental samples.Here,a comprehensive identification strategy was developed for the target,suspect,and functional group-dependent screening of OPTEs in environmental samples by the use of ultrahigh-performance liquid chromatography-Q Exactive hybrid quadrupole-Obritrap high-resolution mass spectrometry（UHPLC-Q-Orbitrap HRMS）.This strategy acquired data through selected ion monitoring（SIM）and Full mass-AIF（all ion fragmentation）mode under positive atmospheric pressure chemical ionization（APCI⁺）source,and subsequently used software such as Trace Finder and Xcalibur to assist in（semi-）quantification,screening,and structural derivation to achieve comprehensive identification of OPTEs in environmental samples.Meanwhile,this strategy was applied for the analysis of 95 surface soil samples collected from different functional areas in Dongguan city.In these analyzed samples,31 OPTEs were fully or tentatively identified,and 15 of them were reported in surface soil for the first time.For target identification,eight of nine target OPTEs in surface soil were measurable above the method limits of quantifications,of which bis-（2-ethylhexyl）-phenyl phosphate（BEHPP）was first detected in surface soil samples.Simultaneously,samples from commercial,industrial,and residential areas contained significantly greater ∑₈OPTEs and BEHPP concentrations than those from agricultural and scenic areas.Furthermore,strong and statistically significant correlations were observed between BEHPP and five OPTE congeners,particularly for TEHP（r = 0.764,p < 0.001）,TBOEP（r = 0.687,p < 0.001）,and TPHP（r = 0.709,p < 0.001）,indicating that BEHPP may have similar commercial applications and sources to these OPTEs in surface soil.For suspect identification,a suspect identification database containing 96 OPTEs was constructed,and a total of 22 suspect OPTEs were screened and detected in surface soil of Dongguan city using this database,among which bisphenol A bis（diphenylphosphate）（BPABDP）exhibited the highest average concentration（13.4 ng/g dw）and detection frequency（83.2%）.Meanwhile,we also observed that BPABDP was significantly correlated with all other OPTEs（p < 0.001）,suggesting that BPABDP may be widely used as plasticizers and flame retardants in a variety of commercial products.For functional group-dependent identification,a novel OPTE was first discovered in surface soil samples and named of（tert-butyl）phenyl bis（2,4-di-tert-butylphenyl）phosphate（TBPBDTBPP）,that shared a very similar backbone structure with the well-known OPTE,tris（2,4-di-tert-butylphenyl）phosphate（TDTBPP）.However,the exact structure of TBPBDTBPP still requires further confirmation.Simultaneously,TBPBDTBPP exhibited relatively high detection frequency（69.5%）with the concentration ranging from ND to 15.3ng/g dw（median concentration: 0.388 ng/g dw）,and it was widely distributed in various functional areas.Furthermore,the statistically significant correlation was also observed between the concentrations of TBPBDTBPP and IDDP,BPABDP,DP4 IPPP and TCrP（p <0.05）.In summary,this study provided a comprehensive identification strategy for screening OPTEs in surface soil and verified the feasibility of this nontarget screening strategy,which could significantly expand and enrich our knowledge and understanding of OPTEs present in surface soil.