Metalloporphyrin Complex Analysis Method And Its Distribution In Oil Contaminated Soil

With the rapid increasing of the oil production and oil pollution worsening, the compound pollution of oil and heavy metals in soil has caused wide public concern. Metalloporphyrin complex was a kind of organic metal complex which was formed by porphyrin and heavy metals in the oil. It has the characteristics of chemical stability, cumulative, persistence and toxicity. As the "DNA" of oil, it retained enough chemical structure information in the process of oil formation. Its physical and chemical behaviors in oil medium had comprehensively studied by people. However, so far there haven’t any related research for its existence, migration and transformation behavior in the environmental medium. Understanding these theories would help us to establish effective pollution repair methods quickly, and then implement repair soil pollution.Metalloporphyrin complex were selected as the studied object in this paper. On the basis of the comprehensive research of literature review, Suitable methods for the analysis of oil metalloporphyrin in crude oil and soil were established separately by optimizing the extraction, purification and analysis conditions. And they were applied to the actual oil and soil samples successfully. The main contents and results were as follows:(1) A method using accelerated solvent extraction combined with liquid chromatography-mass spectrometry to separate and identify Metalloporphyrin complex in crude oil was established. The effect on extraction efficiency of the type of extraction solvents, extraction temperature, static extraction time and the repeat times of static extraction were studied. Optimal conditions for accelerated solvent extraction were as follows:kieselguhr as absorbent, methanol as solvent extraction,80℃of extraction temperature,15min of static extraction time and3times of repeat static extraction. The best analysis conditions of LC-MS were:methanol/water=98/2 (v/v) as mobile phase, C18bonded silica gel chromatography column (4.6x250mm) as the stationary phase, atmospheric pressure chemical ionization (APCI) as ionization source,350℃of ion source temperature,4L· min-1of the carrier gas flow rate,240v of fragmentor voltage,4500v of capillary voltage,350-350amu of scanning range. Quality control and quality assurance results showed that the recovery range was85.3%～85.3%, the relative standard deviation was3.68%, the limits of detection was0.1μg·g-1.(2) Metalloporphyrin complex in Gudao crude oil were analyzed and identified by the build method. The results were shown as follows:Vanadium porphyrin and nickel porphyrin in Gudao crude oil both exist ETIO and DPEP types, and ETIO were the main type. The content of vanadium porphyrin and nickel porphyrin in Gudao crude oil were35.95μg·g-1and84.48μg· g-1, in which the ETIO type accounted for71.4%and80.0%respectively. Carbon number of ETIO and DPEP vanadium porphyrin were C22-C33and C25-C33, in which the most abundant content were C34-ETIO (m/z=571) and C32-DPEP (m/z=541) respectively. Carbon number of ETIO and DPEP nickel porphyrin were C22-C39and C28-C36, in which the most abundant content were C33-ETIO (m/z=549) and C32-DPEP (m/z=533) respectively.(3) The best pretreatment technology to separate vanadium porphyrin from soil was obtained by optimizing extraction conditions of ultrasonic assisted extraction, accelerated solvent extraction and soxhlet extraction technology. Soxhlet extraction-silica alumina column purification-HPLC analysis method for determination of vanadium porphyrin in soil was established. The optimum analysis conditions were as follows:methanol as solvent extraction,24h of extracting time,80℃of extraction temperature,30mL cyclohexane/dichloromethane (1:4, V/V) as eluant. Quality assurance and quality control showed that the method of relative standard deviation was3.68%, the recovery range was85.3%～85.3%and the method detection limit was0.5μg·g-1.(4) Vanadium porphyrin in soil samples collected around Gudao oildom were determined according to soxhlet extraction-silica alumina column purification-HPLC analysis method. The results were shown as follows:the vanadium porphyrin in the soil around oil wells which were exploit at different times (1970s,1980s,1990s and2000s) were in the range of405.1-3521.2μg·g-1. The longer the oil wells exploited, the higher the contents in the soils, the relationship between vanadium porphyrin concentration and the distance for the oil wells was negative exponent, Vanadium porphyrin permeability was inversely proportional to the soil holding capacity and oil viscosity. With the increase of soil depth, the vanadium porphyrin contents increased at first and then decreased. After many years of accumulation, vanadium porphyrin contents reached a maximum at40-50cm.