Portable solid-phase sampling organic extraction agent and detection method

Abstract

The invention relates to the technical field of extraction materials, in particular to a portable organic extraction agent for solid-phase sampling and a detection method. According to the specific technical scheme, the preparation method of the portable solid-phase sampling organic extraction agent comprises the following steps: adding excessive complex into methanol, uniformly mixing, adding sodium citrate, adding 0.3% by volume of volatile acid, and refrigerating the mixed solution to obtain the solid-phase extraction agent. According to the invention, the problems of portability and safety during real-time sampling analysis of soil, wastewater and animal and plant tissues in the environment are solved.

Description

Technical Field

[0001] The invention relates to the technical field of extraction materials, and in particular to an organic extractant and a detection method for portable solid phase sampling. Background Art

[0002] The traditional sampling method is to first collect soil, wastewater, animal and plant tissues, grind the large particles, and then use an extractant to extract the substances in the sample. After extraction, the sample is centrifuged or placed for a long time. The entire analysis process is complicated. Sampling, grinding, and extraction require the use of tools such as sampling containers, grinders, pipettes, centrifuges, etc., which is not conducive to convenient and rapid sampling and analysis on site, and does not meet the time requirements of ready-made rapid analysis.

[0003] At present, the mainstream on-site sampling still adopts the solution of liquid extraction agent. Liquid extraction has the following shortcomings:

[0004] 1. The liquid extractant needs to be injected into the sampling container only after sampling is completed. Otherwise, if the extractant is injected first, splashing will occur when the sample is placed, affecting the accuracy of the measurement.

[0005] 2. Liquid extractants mostly use organic solvents such as methanol, which are easy to volatilize at room temperature. They will evaporate without special treatment or for a long time. Especially in a high temperature environment, large amounts of volatilization are very likely to occur, resulting in inaccurate test results.

[0006] 3. Most of the existing solid extractants contain agar as a complex. Agar is an organic substance and will be extracted by organic solvents during extraction. At this time, agar is introduced into the analysis system as an impurity. If mass spectrometry is used, agar will be cracked in the ion source, which will make the peak of the spectrum complex. In addition, agar has a large molecular weight and a large polarity. When passing through a liquid chromatograph (LC), an eluent with a large polarity is required to elute agar. However, an eluent with a large polarity will damage the chromatographic column, and the damage is irreversible.

[0007] 4. In the extraction step, a pipette or pipette is needed to absorb the extractant and transfer the absorbed extractant to the extraction container. Although the use of a pipette is simple, it still tests the operator's practical level. When conducting law enforcement inspections or rapid screening, on-site sampling personnel often need to quickly conduct sampling and screening. Adding a process of taking the extractant undoubtedly increases the time, and the requirements for operators are high. At least they must undergo strict chemical operation standard training. However, our front-line personnel often do not have chemical operator certificates and find it difficult to skillfully operate equipment such as pipettes.

[0008] 5. Rapid screening and analytical testing, use contamination is a problem that must be solved. If an external large bottle of extractant is used, although the packaging cost is low, if isolation measures are not taken when it is taken multiple times, it will inevitably cause contamination to the solvent, and the source of contamination is difficult to locate, which will lead to inaccurate test results. If isolation is done, an intermediate container needs to be added for use, and the steps are cumbersome. If the sampling container and the extraction solvent are packaged separately to form a test package, the packaging cost will increase significantly and the use cost will be high.

[0009] 6. It is unsafe to carry a large amount of liquid solvent when conducting on-site rapid screening. Once a leak occurs, it can easily turn into a flowing fire under the action of static electricity, posing a major safety hazard. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention provides an organic extractant and detection method for portable solid-phase sampling, which solves the portability and safety issues in real-time sampling and analysis of soil, wastewater, and animal and plant tissues in the environment.

[0011] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0012] The invention discloses a method for preparing a portable solid phase sampling organic extractant. Excessive complex is added into methanol, mixed evenly, sodium citrate is added, and a volatile acid with a volume fraction of 0.3% is added, and then the mixed solution is refrigerated to obtain a solid phase extractant.

[0013] Preferably, the complex is calcium acetate or phosphate, and the volatile acid is any one of formic acid, acetic acid, propionic acid and hydrochloric acid.

[0014] Preferably, the complex is added to the methanol until saturation, and the ratio of the methanol to sodium citrate is 1:1, v / m.

[0015] Correspondingly, a solid phase extraction agent prepared by the above preparation method.

[0016] Correspondingly, a detection method for the solid phase extractant prepared by the above-mentioned preparation method is provided, wherein the solid phase extractant is sealed in a PE tube, the collected sample is placed in the PE tube, and the supernatant is taken out after grinding for direct sampling detection.

[0017] Preferably, the supernatant is detected in LC or LCMS.

[0018] The present invention has the following beneficial effects:

[0019] 1. The present invention provides a solid phase extractant, and a steel ball is built into a PE tube, which solves the portability and efficiency problems of the extractant in the process of sampling soil, wastewater, animal and plant tissues.

[0020] 2. The detection method disclosed in the present invention is simple and easy to implement, and has a wide range of applications. It can be widely used in on-site rapid screening and sample testing.

[0021] 3. The PE tube used in the present invention integrates grinding steel balls and solid phase extractants, and no additional liquefied extractant subpackaging is required, which reduces packaging costs and usage costs. It improves usage safety, avoids potential safety hazards in liquefied transportation, and greatly improves the safety of users.

[0022] 4. In the present invention, each solid extractant is independently packaged in a PE tube, which is convenient to use and avoids the problem of inaccurate test results caused by solvent contamination. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the quantitative curve of Example 1. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0026] The invention discloses a method for preparing a portable organic extractant for solid phase sampling, and the specific process is: adding an excess of complex to methanol to form a saturated methanol solution of the complex, and after mixing evenly, adding an appropriate amount of sodium citrate to promote the complexing effect of the complex; and adding a volatile acid with a volume fraction of 0.3%, and then refrigerating the mixed solution in a refrigerator for a period of time to obtain a solid phase extractant. The complex is calcium acetate or phosphate, and the volatile acid is any one of formic acid, acetic acid, propionic acid, and hydrochloric acid. The complex is added to the methanol until saturated, and the ratio of methanol to sodium citrate is 1:1, v / m.

[0027] In the present invention, the use of methanol can be used as an extractant to extract organic substances in the solid phase. At the same time, as a diluent, it dilutes the high-concentration target substance and is also important for the ionization process of the ion source as a proton individual. The added volatile acid (such as formic acid) can promote the protonation of methanol so as to provide a proton donor in the APCI ion source. Similarly, an appropriate amount of acid is important for the ionization mode of ion formation by electrospray. Similarly, the volatile acid can also be acetic acid, propionic acid, hydrochloric acid, etc.

[0028] In the present invention, when sodium citrate is not added, the solidification of methanol takes a long time and evaporates quickly when exposed to air. After sodium citrate is added, the solidification can be completed in a short time under low temperature conditions.

[0029] The solid phase extractant prepared by the present invention is suitable for LC (liquid chromatograph) and LCMS (liquid chromatography mass spectrometry) for solid and liquid sample detection, but is not suitable for water sampling because the miscibility of methanol and water will increase the volume of the liquid sample, resulting in quantitative inaccuracy, but if it is a qualitative operation, there is no effect.

[0030] Furthermore, the present invention is particularly suitable for LCMS detection, and can be applied to both APCI ion source and ESI ion source, and has good compatibility.

[0031] When the solid phase extractant prepared by the present invention is tested, the solid phase extractant is sealed in a PE tube. When actually used, the PE tube is opened, and the collected sample (liquid or solid) is directly placed in the PE tube, and then placed in a grinder. After grinding and centrifugation, the supernatant is taken and directly sampled and tested.

[0032] Furthermore, in the PE tube, grinding steel beads are built into the solidified extractant. When the fixed extractant is loaded into the PE tube, the amount of solid phase extractant is predetermined, and the operator does not need to perform the transfer operation, thereby ensuring the accuracy of the extraction dilution result. The volume of the solid phase extractant and the solvent volume of the extracted sample have a linear relationship; when sampling, there is no need to separate the extraction and sampling grinding. It is only necessary to put the collected sample into the PE tube containing the solid phase extractant, and place the PE tube in the grinder for grinding, thereby overcoming the problem of the need to add additional liquid extractant during the analysis and sampling process. After grinding, under the action of the centrifuge, or after being placed for a long time, the complex used for complexation will be deposited to the bottom, and while completing the sample extraction, most of the complex is also removed, reducing the matrix effect during detection. Because of the presence of the complex, even if the extractant is exposed to the atmosphere, there will be no major volatilization problem, and there is sufficient time for the sampler to take safe samples after opening. Among them, the complex used is phosphate and calcium acetate, which can be eluted with an eluent with less polarity, has good adaptability to LC chromatographic columns, is suitable for LCMS coupling technology, rapid analysis and detection, and has good instrument applicability when used in conjunction with a portable mass spectrometer or other instruments.

[0033] Furthermore, the present invention utilizes the reversible property of solidification and liquefaction. During preparation, accurate quantification can be performed by injecting liquefied liquid at a higher temperature, and then promoting solidification at a lower temperature. After solidification, it will not melt unless the temperature rises significantly, and will not return to liquid at room temperature. The high temperature generated during grinding can convert the solid state back into liquid state. After centrifugation, the solid and the supernatant are separated, which is convenient for sampling the extracted liquid.

[0034] The present invention will be further described below in conjunction with specific embodiments.

[0035] Example 1

[0036] 1. Add excess calcium acetate and 1 g of sodium citrate to 1 mL of methanol, mix well, then add 0.3% by volume of formic acid, mix the solution and refrigerate to obtain a solid phase extractant.

[0037] 2. The present invention uses a mixture of benzene and toluene as a comparative sample to illustrate the feasibility of the solid phase extractant prepared by the present invention. The present invention uses LC liquid phase as a detection method, and uses methanol solutions of toluene with a volume fraction of 10%, 20%, 30%, 40%, and 50% in methanol to calibrate the quantitative curve of benzene. The composition and concentration of the unknown solution are determined by the column retention time and the integrated area. The size of the integrated area indicates the concentration, while the column retention time represents the specificity of the substance. Due to the influence of instrument aging, injection dead volume, etc., there will be a certain reasonable error in the column retention time. The results are shown in Figure 1 As shown in Table 1, the fitting curves of the integrated area and volume fraction show good linearity and R 2 The value is greater than 0.99.

[0038] Table 1 Column retention time and integrated area

[0039]

[0040]

[0041] The solid phase extractant prepared above contained 1 mL of methanol solution, and 1 mL of aqueous solution containing 60% benzene was added. After grinding and shaking, the supernatant was taken for liquid phase testing. The results were: integrated area 246513498 mv, column retention time 22.782 min.

[0042] After obtaining the integral area, substitute it into the equation and calculate 0.34. It can be known that the liquid after dilution and extraction contains about 30% benzene. After coefficient conversion, it can be known that the original solution contains about 60% benzene. This is when the sample is a solution and coefficient conversion is required. When the sample is solid, no coefficient conversion is required. The formula is the concentration of the solid sample dissolved in the methanol solution.

[0043] If the sample being tested is an unknown substance, LCMS can be used to analyze the sample. LC obtains the accurate concentration of the sample, while MS (mass spectrometry) analyzes the sample components, thereby quickly completing the analysis process.

[0044] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing an organic extractant for portable solid phase sampling, characterized in that: An excess amount of complex is added to methanol, mixed evenly, and then sodium citrate and 0.3% by volume of volatile acid are added. The mixed solution is then refrigerated to obtain a solid phase extractant.

2. The preparation method according to claim 1, characterized in that: The complex is calcium acetate or phosphate, and the volatile acid is any one of formic acid, acetic acid, propionic acid and hydrochloric acid.

3. The preparation method according to claim 1, characterized in that: The complex is added to the methanol until saturated, and the ratio of the methanol to sodium citrate is 1:1, v / m.

4. A solid phase extraction agent prepared by the preparation method according to any one of claims 1 to 3.

5. A method for detecting a solid phase extractant prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The solid phase extraction agent is sealed in a PE tube, the collected sample is placed in the PE tube, and after grinding, the supernatant is taken and directly sampled and tested.

6. The detection method according to claim 4, characterized in that: The supernatant was assayed in LC or LCMS.

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