Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The following will describe embodiments of the present invention in further detail with reference to the accompanying drawings, and as shown in fig. 1, a schematic flow chart of a target molecule detection method based on a molecularly imprinted polymer provided by the embodiments of the present invention is shown, where the method includes:
step 1, filling a solid phase extraction column with a specific molecularly imprinted polymer serving as an identification unit;
in the step, 50mg of the specific molecularly imprinted polymer can be weighed and filled in a polypropylene solid phase extraction column, wherein the column volume of the solid phase extraction column is 1.0 mL;
after filling, placing a polytetrafluoroethylene sieve plate on the upper part of the solid phase extraction column, and inserting a tool to compress tightly to prevent leakage.
In specific implementation, detection of different target molecules can be realized by setting the types of the molecularly imprinted polymers. For example, the molecularly imprinted polymer is set as the hydroxyl polychlorinated biphenyl molecularly imprinted polymer, so that the trace quantity of hydroxyl polychlorinated biphenyl in the water sample can be rapidly detected.
Step 2, connecting the upper part of the solid phase extraction column with a container for containing water, and loading the lower part of the solid phase extraction column on a solid phase extraction instrument;
step 3, connecting the solid phase extraction column with a vacuum pump for vacuum pumping to enable water on the upper part to flow rapidly;
and 4, recording the time when the water completely passes through the solid phase extraction column by using a timer, and converting the molecular detection into time detection to realize the detection of the specific target molecules.
The detection principle of the method is as follows: the molecularly imprinted polymer can specifically identify and adsorb target molecules, so that the effective pipe diameter of the hourglass neck pipe of the solid-phase extraction column is reduced, and the time for quantitative water to flow out of the neck pipe is changed; and recording the time change by a timer, and converting the molecular detection into time detection to realize the detection of the specific target molecules.
In a specific implementation, the relationship between the concentration of a specific target molecule and the efflux time is specifically as follows:
ΔT=2.02C+0.36(R2=0.9979)
wherein, the delta T is the difference of the time required for 15ml of water to completely flow out when the target molecule exists or not; c is the concentration of a specific target molecule, which may be 4' -OH-PCB 30; and R is a fitting degree correlation coefficient, and the larger the value is, the more accurate the fitting degree of the formula is represented.
Based on the method, the rapid detection process of the trace amount of the hydroxyl polychlorinated biphenyl in the water sample specifically comprises the following steps:
firstly, activating a molecularly imprinted polymer solid phase extraction column by acetonitrile to enable the surface of the molecularly imprinted polymer and a target molecule to be easily adsorbed; wherein the molecularly imprinted polymer is a hydroxyl polychlorinated biphenyl molecularly imprinted polymer;
then 2ml deionized water is used for leaching the chromatographic column, and 50ml water sample liquid is added for sample loading;
leaching the solid phase extraction column with 2ml of deionized water to remove endogenous impurities and other impurities in the water sample;
and then taking 15mL of deionized water to flow through the solid phase extraction column, and recording the time when the water completely passes through the solid phase extraction column by using a timer, so as to realize the detection of the trace amount of the hydroxyl polychlorinated biphenyl in the water sample.
In a specific implementation, a diaphragm vacuum pump (0.088MPa) can be used to rapidly flow deionized water from the upper glass spheres through the neck of the solid phase extraction column.
In addition, the optimal amount of acetonitrile for activating the molecularly imprinted polymer solid phase extraction column is 2mL, and the reason for selecting the amount is specifically as follows:
respectively activating the molecularly imprinted polymer solid phase extraction column by acetonitrile with different volumes (0ml, 0.5ml, 1ml, 2ml, 3ml, 4ml, 5ml and 6ml) to enable the surface of the molecularly imprinted polymer and the target molecule to be easily adsorbed; eluting the chromatographic column with 2ml of deionized water, and adding 50ml of sample solution for sample loading; leaching the solid phase extraction column by using 2ml of deionized water to remove endogenous impurities and other impurities in the sample; finally, 15mL of deionized water was passed through the solid phase extraction column and the time for water to completely pass through the solid phase extraction column was recorded using a timer.
FIG. 2 is a graph showing the relationship between the amount of acetonitrile and Δ T, where Δ T gradually increases as the amount of acetonitrile increases from 0 to 2 mL; when the using amount of the acetonitrile is 2, the delta T is maximum; when the amount of acetonitrile used was increased from 3 to 6, Δ T gradually decreased. When the using amount of acetonitrile is less than 2mL, the wettability is insufficient, target molecules cannot be completely adsorbed, and the delta T is small; when the amount of acetonitrile is more than 2mL, the excess acetonitrile affects the adsorption of the target molecule, resulting in a decrease in Δ T. Therefore, when hydroxyl polychlorinated biphenyl is detected, the optimal using amount of acetonitrile for activating the molecularly imprinted polymer solid phase extraction column is 2 mL.
In addition, when hydroxyl polychlorinated biphenyl is detected, the optimal pH value of the water sample is 11, and the reason for selecting the dosage is specifically as follows:
the time signal is influenced because the pH value of the water sample can influence special bonds (including hydrogen bonds and ionic bonds) in molecules and hydrophobic interaction between target molecules and the molecularly imprinted polymer. Therefore, the pH value of the water sample is optimized, the pH value of the water sample is adjusted to 3.0-11.0 by using the sodium hydroxide solution, the influence of the pH value on the time signal is studied, as shown in fig. 3, a schematic diagram of the relationship between the pH value and the Δ T of the water sample is shown in the embodiment of the present invention, and when the pH is 3, the Δ T is large; at pH 11, Δ T is maximal and gradually decreases with increasing pH. The reasons for this phenomenon are: -NH of molecularly imprinted polymer under acidic conditions at pH 32Protonation is carried out, positive charge is carried, and cation-pi interaction (non-bond effect) is formed with the benzene ring of the hydroxyl polychlorinated biphenyl; and-NH at pH 5.0, 7.0 and 9.02The protonation gradually disappears, the non-bond effect is weakened, and the delta T is reduced; when the pH value is 11.0, the maximum delta T is formed by the fact that-OH on the hydroxyl polychlorinated biphenyl is ionized and carries negative charges, and charge-assisted N-H … O is formed between the hydroxyl polychlorinated biphenyl and the molecularly imprinted polymer(-)Hydrogen is stronger than ordinary hydrogen bonds. Therefore, when hydroxyl polychlorinated biphenyl is detected, the optimal pH value of the water sample is 11.
In addition, after detection of a specific target molecule, a 10ml volume ratio of 1: the n-hexane and acetonitrile solution of 1 is used for eluting the molecularly imprinted polymer adsorbing the specific target molecules, and the molecularly imprinted polymer can be repeatedly used after the elution is finished. FIG. 4 is a graph showing the change of Δ T with the number of elution times according to the example of the present invention, C(Hydroxypolychlorobiphenyl)80ppb, after 5 adsorbings and elutions, the Δ T has no significant change, indicating good reusability of the process of the invention.
Taking the detection of 4 '-OH-PCB 30 as an example, the detection was performed as described above for different concentrations (0, 20ppb, 40ppb, 60ppb, 80ppb) of 4' -OH-PCB30, and then the Δ T was recorded. As shown in fig. 5, which is a schematic diagram of the linear relationship between Δ T and the concentration of hydroxypolychlorobiphenyl according to the embodiment of the present invention, Δ T increases with the increase of the concentration of 4 '-OH-PCB 30 (15ml of water), and Δ T and the concentration of 4' -OH-PCB30 are in good linear relationship within the range of 1-100 ppb, the linear equation can be expressed as:
ΔT=2.02C+0.36(R2=0.9979)
wherein, the delta T is the difference of the time required for 15ml of water to completely flow out when the target molecule exists or not; c is the concentration of 4' -OH-PCB 30; r is a correlation coefficient;
the lowest detection concentration LOD is 0.3ppb (S/N is 3); LOD is the lowest concentration above which the target molecule is detected, or above which it is detected.
In addition, several different analytes such as 4-OH-4 '-iodobiphenyl, bisphenol A, PCB156, PCB101 and the like can be selected as the interferent, the concentration of the target molecule 4' -OH-PCB30 is 10ppb, and the concentrations of other interferent are all 1ppm, as shown in fig. 6, the method is a schematic diagram of the selective detection of hydroxypolychlorobiphenyl according to the embodiment of the present invention, when the interferent exists, Δ T is smaller, and the Δ T is significantly increased along with the increase of the concentration of the target molecule, which indicates that the method has high selectivity.
The following describes the process of the above detection method in detail by using a specific example, in this example, trace amounts of hydroxypolychlorobiphenyl in a water sample are detected, and the specific process is as follows:
collecting a certain amount of water sample from the pond, filtering impurities such as silt and the like by using a 0.45-micrometer filter membrane after filtering the impurities by using quantitative filter paper, and finally placing the water sample into a brown glass bottle for storage at 4 ℃; the pH of the water sample was adjusted to 11.0 with sodium hydroxide solution before testing.
Activating a molecularly imprinted polymer solid-phase extraction column by using 2ml of acetonitrile to enable the surface of the molecularly imprinted polymer and a target molecule to be easily adsorbed; eluting the chromatographic column with 2ml of deionized water, and adding 50ml of water sample liquid for sample loading; leaching the solid phase extraction column with 2ml of deionized water to remove endogenous impurities and other impurities in the water sample; and finally, taking 15mL of deionized water to flow through the solid phase extraction column, and recording the time for the water to completely pass through the molecularly imprinted polymer solid phase extraction column by adopting a handheld timer.
The method can be used for detecting the 4 '-OH-PCB 30 in the pond water sample, and the concentration of the 4' -OH-PCB30 in the pond water sample is 2.45 ppb. And 4' -OH-PCB30 with different concentrations (5ppb, 10ppb, 25ppb and 50ppb) is used for sample addition, the recovery rate is between 88.0% and 93.4%, and the RSD is less than 6.7%. The results show that: the method provided by the embodiment of the invention has a good application prospect in the detection of actual samples.
It is noted that those skilled in the art will recognize that embodiments of the present invention are not described in detail herein.
In conclusion, compared with the defect that a biological recognition system is greatly influenced by the environment, the detection method provided by the embodiment of the invention has the advantages that the molecularly imprinted polymer shows stronger stability in different environments, and has the characteristics of simple principle, convenience in operation, good selectivity, high accuracy and the like; if the variety of the molecularly imprinted polymer is changed, different target molecules can be detected, and the application range of the technology is greatly expanded.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.