CN102252869A - Passive sampler for organic pollutants in sediments based on ionic liquid - Google Patents

Abstract

The invention discloses a new passive sampling device which uses an ionic liquid as a receiving phase and can be used for monitoring the concentration of organic pollutants in sediments. The ionic liquid is filled in a low-density polyethylene film pipe; the film pipe is fixed by an organic glass frame with a wedge-shaped sharp point; the device can be vertically inserted into the sediments of a water body; and the pollutants in the interstitial water of the sediments are passively collected. The ionic liquid has designability, and different types of ionic liquids can be selected according to the difference of monitored target organic pollutants, thereby improving the bearing capability of a receiving phase on target pollutants. After passive sampling is completed, the ionic liquid of the receiving phase can be directly dissolved in an organic solvent with low dosage; and then, instrument analysis is carried out, thereby reducing the consumption of volatile organic solvents in the elution loop of the receiving phase. An analog experiment result indicates that a logarithm value of the enriched concentration of target pollutants in the sampling device and a logarithm value of the concentration of the pollutants in the sediments have better relativity when the sampling is completed.

Description

An Ionic Liquid-Based Passive Sampler of Organic Pollutants in Sediments

technical field

The invention relates to a new passive sampling device which uses ionic liquid as a receiving phase to collect and monitor the existing level of organic pollutants in sediments.

Background technique

Sediment is the "sink" of organic pollutants in the aquatic environment, and most of the organic pollutants in natural water bodies will eventually enter the sediment. When the environment changes, some pollutants may re-enter the water phase to form secondary pollution. Therefore, the environmental monitoring of organic pollutants in sediments is of great significance to the protection of human health and the maintenance of environmental ecology.

There are many limiting factors in the active sampling monitoring method, for example, the limited volume of water samples collected, the concentration factor is not high, the removal steps of interfering substances are cumbersome and expensive, and the analysis results often only represent the instantaneous situation of organic pollutants in the water environment. Therefore, the passive sampling technology, which can continuously collect the integral concentration of pollutants in the environmental medium within the sampling period, is widely used in the monitoring of trace organic pollutants in the environment and in the research of environmental processes. However, the accepting phases widely used in passive sampling techniques for organic pollutants are mostly neutral lipids (for non-polar organics) or exchange resins (for polar organics), which often need to be used in the pretreatment process after sampling There are a large number of volatile organic solvents that are harmful to the environment; moreover, passive sampling techniques for passive sampling and monitoring of organic pollutants in sediments have yet to be developed.

Ionic liquids refer to salts that are liquid at or near room temperature (below 100°C), and are usually composed of organic cations containing nitrogen and phosphorus and inorganic or organic anions. It has some unique physical and chemical properties, such as: extremely small vapor pressure, can dissolve many organic, inorganic and polymer materials; has good thermal stability, non-flammable; can be adjusted by adjusting the composition of anions and cations Its melting point, viscosity, density and solubility in water and other organic solvents, etc. These unique properties make it possible to replace traditional organic solvents in many fields and become safe and environmentally friendly new solvents. Due to the above-mentioned environment-friendly characteristics and the "designable" nature of the structure, ionic liquids have the possibility of being applied to the enrichment monitoring of polar organic pollutants in sediments. At present, ionic liquids have been successfully applied in the research of liquid-liquid extraction of polar/non-polar organic substances, metal ions and other substances; there are also a small number of research works published on the use of ionic liquids to extract various pollutants in soil/sediment.

Contents of the invention

The invention aims to provide a passive sampler with ionic liquid as the accepting phase, which can continuously collect the organic pollutants in the interstitial water of sediments, so as to reflect the pollution level of the pollutants in the sediments. This technique is simple, economical, efficient, and consumes less organic solvents.

The structure of the passive sampling device provided by the present invention is as follows: the passive sampler is a flat vertical insertion type as a whole, and is composed of a low-density polyethylene film tube filled with ionic liquid and a plexiglass fixed frame with a wedge-shaped tip. The main body of the plexiglass fixed frame is two plexiglass plates with a length of 120mm, a width of 40mm, and a thickness of 3mm. The hollow part inside the plate is a sampling ^window . The bottom surface of the wedge-shaped tip at the front end is a rectangle with a length of 40mm and a width of 9mm, and the tip is 16mm high. The material of the wedge-shaped tip is plexiglass, and it is glued to the main body of the fixed frame with glue (as shown in Figure 1). Weigh 100mg of ionic liquid and fill it into a low-density polyethylene film tube with a length of 80mm and a width of 25mm, and use a heat sealer to seal the 5mm parts at both ends of the film tube with heat and pressure, and use this as the receiving phase of the passive sampler ( as shown in picture 2). Place the receiving phase membrane tube between two plexiglass fixing frames, and fix the membrane tube with stainless steel washers, screws and nuts.

The passive sampler can be directly inserted into the water body sediment for passive sampling and monitoring, and can be filled with ionic liquids of different properties as the receiving phase according to the different target compounds as the monitoring objects. The period of monitoring depends on the actual needs, the nature of the target compound and the pollution level.

The pretreatment method of the sample obtained by passive sampling is as follows: after the sampler is recovered, dry the outer surface of the membrane tube with clean absorbent cotton. Cut the membrane tube, transfer the ionic liquid to the test tube, and rinse the inner surface of the membrane tube with 5ml of acetonitrile, and transfer the rinse solution to the test tube, blow the acetonitrile nitrogen in the test tube to 1ml, and then use the instrument to detect the pollutants in the sample. Perform analytical testing.

Laboratory research has proved that the passive sampling device established by using ionic liquid 1-hexadecyl-3-methylimidazolium hexafluorophosphate can detect two kinds of endocrine disruptor organic pollutants ( 17β-estradiol and bisphenol A) can achieve effective collection (Figure 3); the samplers were placed in four sewage river sediments collected from different locations and with different pollution levels, and the target pollution in the sampler after 7 days The logarithmic values of the concentrations of bisphenol A and 17β-estradiol had a good correlation with the logarithmic values of the pollutant concentrations in the sediments extracted by the Soxhlet extraction method (Fig. 4 and Fig. 5).

Description of drawings

Figure 1 Schematic diagram of a plexiglass fixed frame with a wedge-shaped tip

Fig.2 Schematic diagram of receiving phase of LDPE membrane tube filled with ionic liquid

Figure 3 The passive sampling static enrichment curves of two endocrine disruptors—bisphenol A and 17β-estradiol—by the passive sampling device based on ionic liquids

Figure 4 is based on the passive sampling device of ionic liquid 1-hexadecyl-3-methylimidazolium hexafluorophosphate to the 7-day enrichment concentration logarithm of bisphenol A in the sediments of 4 different locations of a sewage river in Tianjin ( The linear relationship between log C _{P_bisphenol A} ) and the logarithm value of bisphenol A concentration in the sediment (log C _{S_bisphenol A} )

Fig. 5 The 7-day enrichment concentration of 17β-estradiol in the sediments of four different locations in a sewage river in Tianjin by passive sampling device based on ionic liquid 1-hexadecyl-3-methylimidazolium hexafluorophosphate The linear relationship between the value (log C _{P_estradiol} ) and the logarithm of the concentration of 17β-estradiol in the sediment (log C _{S_estradiol} )

Claims (5)

1. The present invention is a passive sampling device using ionic liquid as the receiving phase, which is used to enrich and monitor organic pollutants in sediments. 2. The passive sampler in claim 1 is a flat vertical insertion type as a whole, consisting of two parts: a semi-permeable membrane tube filled with ionic liquid and a plexiglass fixed frame with a wedge-shaped tip. After the semi-permeable membrane tube is filled with ionic liquid, both ends are sealed by hot pressing, placed between two plexiglass fixing frames, and the membrane tube is fixed by screws and nuts. 3. The main body of the two pieces of plexiglass fixing frame in right 2 is 120mm long, 40mm wide, and 3mm thick, the hollow part is 70mm long, 20mm wide, the effective sampling area is 14cm ² , and the bottom surface of the wedge-shaped pointed head is 40mm long and 9mm wide. Rectangular, with a tip height of 16mm. 4. The semi-permeable membrane tube in right 2 adopts a low-density polyethylene membrane tube with a width of 25mm. The length of the membrane tube used in each sampling device is 80mm. The mass ratio was 140 cm ² /g. 5. The ionic liquid in claim 2 is an imidazole-type ionic liquid whose cation is imidazole or substituted imidazole.

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