| The use of organophosphorus pesticides has a very serious impact on human health and the environment,so the detection of organophosphorus pesticide residues is very important.In this study,a microbial sensor for the determination of organophosphorus pesticide residues using methamidophos organophosphorus pesticides as a typical model compound was designed and fabricated based on the physiological characteristics of polyphosphorus bacteria.Compared with other reported methods,the microbial sensor of this study could determine organophosphorus pesticide residues in a simple,economical,accurate,real-time and on-site manner.The research content is divided into the following three aspects:1)Phosphorus accumulating bacteria are reported to remove inorganic phosphorus from the environment through the process of aerobic phosphorus uptake and anaerobic phosphorus release.In this study,it was also found that the exo-enzymes of P accumulating bacteria in the environment had a high degradation effect on organic phosphorus into inorganic phosphate ions.Firstly,the study of bacterial growth curve found that the phosphorus accumulating bacteria were in a stable phase after being cultured for 28 h at 22? and 160 r/min stirring cultivation conditions.The optimal medium conditions for the aerobic phosphorus uptake process are pH 7.2 containing 0.2%acetic acid solution at 18?;and the medium dissolved oxygen content in the anaerobic phosphorus release process is 3.0 mg/L(highest S/N)and acetic acid has little effect on phosphorus release;a 99.4%of methamidophos(0.2 mg/L)is degraded under 60 min of aerobic phosphorus uptake and 30 min of anaerobic phosphorus release.It is equivalent to every single polyphosphate bacteria degrade 1.6×10-9 mg methamidophos pesticide.The linear detection range of the the PAOs sensor is 0.001?0.2 mg/L(1×105 polyphosphate bacteria/mL)for the methamidophos,the minimum detection limit is 0.4 ?g/L,the linear correlation coefficient R2 is 0.990.The relative standard deviation is 0.740%for three consecutive measurements.When the detection cell capacity is reduced to 300 ?L from 10 mL,the detection sensitivity is increased by about 100 times.2)This study also studied on the exo-enzymes of polyphosphate bacteria.Two kinds of exoenzymes were isolated by gel electrophoresis,and their sizes are 15 K(enzyme ?)and 10 K(enzyme ?),respectively,and the mass fraction of enzyme ? was more than that of enzyme ?.Quantitative results by UV-visible spectrophotometry showed that the enzyme concentrations are 90?g/mL and 73 ?g/mL,respectively(1×105 polyphosphate bacteria/mL)with and without methamidophos(0.2 mg/L)in the medium.The two enzymes were separated and apply to degrade methamidophos,and the degradation efficiency of enzyme ? is higher than enzyme ?.The Michaelis-Menten equation is V=6.754×10-5(S)/(0.035+(S)),the maximum reaction.The rate is Vmax=6.754×10-5 ?mol/mL/min.3)In order to assort the orthophosphate detection of the microbial sensor of the polyphosphate bacteria,a phosphate ion selective electrode consisting of 1-butyl-3-methylimidazolium hexafluorophosphate([Bmim]PF6)ionic liquid membrane as sensitive electrode and Ag|AgCl|[Bmim]Cl as reference electrode was studied.The linear response of the phosphate ion selective electrode of[Bmim]PF6 ionic liquid sensitive membrane is 10-5?10-mol/L,the slope is-47.3 mV/decade and the detection limit is 1.0 × 10-6 mol/L.The response time is 2 min at 43?.The phosphate ion selective electrode with[Bmim]PF6 ionic liquid was successfully applied to determine the content of phosphate in environmental water and soil.The phosphate ion selective electrode has strong reproducibility and stability,and strong anti-interference,and has certain significance for the study of water and soil phosphate. |
PDF Full Text Request