The fully automatic solid-phase extraction device is equipped with a C18 solid-phase extraction disc to enrich tetrachlorobiphenyl in concentrated water and then use acetic acid.
Ethyl ester and dichloromethane were eluted, separated by a CD 5ms capillary column, and determined in water by gas chromatography mass spectrometry.
Tetrachlorobiphenyl content. The eluent, extraction flow rate, pH value, and methanol addition of the water sample were optimized.
In the test, the mass concentration of PCB52, PCB77, PCB81 was 500～50.0 g l range.
The internal and chromatographic peak areas showed good linearity, and the detection limits were 0002，0.003，0.002μg／l；Spike.
* Rates are 909%，92.7%，95.4%；The relative standard deviations of the measured results were all less than.
3%(n=7)。This method is highly sensitive and suitable for the monitoring of trace levels of tetrachlorobiphenyl in water samples.
Polychlorinated biphenyls (PCBs) are weakly polar organic compounds in which the hydrogen on the carbon atom of the biphenyl ring is replaced by chlorine, and tetrachlorobiphenyl is more.
Chlorobiphenyl is a kind of insulating oil, heat exchanger and lubricating oil in industry, and can also be used as a variety of industrial products.
additives. Tetrachlorobiphenyl is a carcinogen that can cause continuous pollution to soil, water and air.
It is insoluble in water and easily soluble in fat and organic solvents, stable in nature and difficult to decompose, and will be rich in fat in living organisms.
Convergence can cause great damage to the body's nervous, reproductive and immune systems through the food chain1 . Tetrachloropoly.
Benzene is present in very low levels in water, and its detection requires enrichment pretreatment of water samples. There are currently polychlorinated polychlorinated (PCBs) in the water.
The determination method of benzene is mainly to pretreat the water sample and then determine it by gas chromatography, gas chromatography mass spectrometry, etc.
The pretreatment methods for PCBs in water include liquid-liquid extraction 2-3, solid-phase extraction and solid-phase microextraction 4-5
Wait. Liquid-liquid extraction to enrich organic matter in water is a commonly used pretreatment method in the laboratory, but the operation steps are cumbersome and analyzed.
The use of a large number of organic solvents in the process is easy to cause harm to experimenters and the environment; Solid-phase microextraction is simple to operate.
Convenient, the extraction efficiency is high, but its cost is high and the time is long; Solid-phase extraction has simple, organic reagents.
It has been widely used in the enrichment and concentration of trace organic matter in water 6-8. The author adopts the whole self.
Dynamic solid phase extraction device, enriched with C18 solid phase extraction disc in concentrated water tetrachlorobiphenyl, by gas chromatography mass spectrometry.
Perform qualitative and quantitative analysis. The method is simple to operate, low detection limit, low dosage of organic reagent, and accurate measurement results.
Reliable. Activation of solid-phase extraction discs.
The membrane was extracted with 10 mL of ethyl acetate activation solid phase extraction disc C18, followed by 10 mL of dichloromethane.
Membranes are taken to activate the extractant so that the long chain of C18 is stretched in favor of close contact with the analyte, and then:
Replace the dichloromethane with 10 ml of methanol and finally remove the methanol with 10 ml of deionized water through the extraction dish to preserve.
The hydrophobic extractant surface has good contact with the sample aqueous solution to improve the sample extraction efficiency 9-11.
1.5. Sampling and water sample processing.
Surface water samples were collected with glass instruments, and suspended organisms and sediment in the water were filtered and removed by qualitative filter paper before being used.
0.45 m microporous membrane filtration 12. Fill a 1 l glass vial with 500 ml of water and add 10
ml methanol was used to modify the sample, and the water sample was adjusted to a pH value of about 5 with hydrochloric acid solution (1 1), which was true.
Empty action with 40 mL min flow rate through the C18 solid-phase extraction disc, followed by 15 mL ethyl acetate, then 10
ML of methylene chloride was used as the eluent to elute the C18 extraction membrane. Since the eluate after collection contains one.
Therefore, after dehydration of anhydrous sodium sulfate, it was placed on a fully automatic nitrogen blowing concentrator for nitrogen blowing concentration near drying, and the volume was fixed to 1 ml with n-hexane for instrument analysis.
2.1 Effect of pH value of water samples.
The pH of aqueous samples can change the presence state of some compounds, the selectivity and extraction efficiency of aqueous solid-phase extraction.
The impact is larger. In this experiment, hydrochloric acid and sodium hydroxide were used to adjust the pH value of the water sample to 3, 5, 7, 9, respectively, and were added.
10 g l of tetrachlorobiphenyl in 12 and 13. Analytical determination under the conditions to investigate the pH value of the sample solution in four.
Effect of chlorobiphenyl on extraction efficiency on C18 solid-phase extraction discs. The test results showed the extraction efficiency of tetrachlorobiphenyl.
The rate decreases with the increase of pH value, and when the pH value is in the range of 3 5, the ** rate of tetrachlorobiphenyl is good.
Considering the applicability of the C18 extraction membrane, the pH of the water sample was adjusted to 5 with hydrochloric acid before loading.
2.2 Effect of the amount of methanol added.
PCBs are less soluble in water because they are highly soluble in non-polar organic solvents and bio-oils. At.
The addition of methanol to the water sample can reduce the surface tension of the water, reduce the adsorption of trace analytes on the wall or pipeline of the sample bottle, and protect the activity of the extraction membrane and increase the rate. The experiment was conducted in a 500 ml water sample in four.
Chlorobiphenyl is added at a volume of 20 g l, and methanol is added at a dose of 0, 3, 5, 10, 15, 20 ml of tetrachlorobiphenyl.
The sample solution of chlorobiphenyl was measured continuously for 7 times according to the whole process, and the relative standard deviation of the determination results was calculated. Press.
mdl=st（n-1，0.99) Calculate the detection limit, when n=7, the t value is taken as 3143 13, Detection Limit Junction.
The results are listed in Table 1.
2.6. Spike** and precision test.
Add a certain amount of tetrachlorobiphenyl standard solution to 500 ml of ultrapure water to prepare a standard solution containing tetrachlorobiphenyl 100
g l of water samples, 7 parts in parallel, extracted, concentrated, and measured on the machine under optimized experimental conditions.
The average spike rate and the relative standard deviation of the measured results are calculated and the results are shown in Table 2, chromatograms of the spiked samples.
See Figure 1. As can be seen from Table 2, the spike rate of tetrachlorobiphenyl is 909%～95.The relative standard deviation of the 7 groups of water samples was less than 3%, which met the quality control requirements of analytical testing.
A solid-phase extraction-gas chromatography-mass spectrometry method for the detection of tetrachlorobiphenyl in water was established. Use sepaths
UP automatic solid-phase extractor device, C18 solid-phase extraction disc (47 mm) extracts water samples, and washes water samples.
The effects of decoupling, pH, extraction flow rate and methanol addition on the separation and enrichment effect were studied and optimized.
The method has the advantages of high efficiency, sensitivity, accuracy and reliability, low pollution, etc., and the spike rate and precision of the method are equal.
It meets the requirements of analytical quality control, and the detection limit is lower than the limit value of PCBs in centralized drinking water, which meets the requirements of water.
Monitoring requirements for trace levels of tetrachlorobiphenyl.