Ion Chromatography Sample Pretreatment Technology !
With the increasing use of ion chromatography, many samples have been unable to perform ion chromatography analysis using conventional methods of sampling, dilution, and direct injection after filtration. For samples with a large number of complex matrices, ion chromatography can be performed by a suitable method, followed by ion chromatography, which can solve the contamination of the ion column by the complex matrix of the sample. The results and accuracy of the complex matrix samples are measured and the sensitivity of the analytical method is improved.
Regarding the sample pretreatment method, with the improvement of the user level of domestic ion chromatography, a large number of pretreatment methods for ion chromatography have appeared. These methods have the following characteristics: (1) Most of the sample preparations are made of domestic materials. The cost of pretreatment is very low, it is more suitable for China's national conditions, and can be widely used in China; (2) Most sample pretreatment methods use off-line methods, which do not require expensive online equipment; but relatively, sample processing The time is longer, and the amount of samples required is also more. In the current automatic injectors, there are no domestic applications, these methods are more practical; (3) and some sample pretreatment methods appearing internationally, domestic Most of the sample pretreatments appearing from the grassroots units are highly practical; however, there are few related theoretical discussions. Therefore, many domestic sample pretreatment methods can be further discussed from a theoretical perspective. On the other hand, it can also be used for pretreatment of online samples by appropriate improvement, including domestic and foreign instruments.
Comparison of the most commonly used sample preparation techniques
Microfiltration Filtration Solid Phase Extraction Technology Adsorption and Osmosis Technology <br> Manufacturers and Manufacturers of All HPLC and Ion Chromatography Manufacturers of all HPLC, GC and ion chromatography manufacturers are still in use.
Material used 0.22 um polysulfone or nylon membrane C18/RP reverse phase / ion exchange / chelating resin filler 0.2 um acetate membrane organic solvent compatibility compatible with incompatible analysis results with good accuracy. The components that rely on the pressure to ensure analysis can all pass without loss. well. The components that rely on the pressure to ensure analysis can all pass without loss. Different samples and different components have different diffusion coefficients and equilibrium rates on the membrane, so it is difficult to ensure the accuracy, repeatability and recovery of the analytical results.
The field of use is widely used in chromatographic analysis such as IC/HPLC. It is widely used in chromatographic analysis such as IC/HPLC/GC. It is widely used in the life science field for desalination of proteins or peptides and removal of small substance impurities. Rarely used in chromatographic analysis.
The scope of application is only for the removal of particulate matter contamination. Easy to use and cheap. Suitable for more than 90% ion chromatography samples. Manual or automatic online use is possible without adding dedicated equipment. Suitable for a wide range of samples and contaminants, it is currently the best ion chromatography sample preparation technology. Simple to use. Manual or automatic online use is possible without adding dedicated equipment. Different samples can be prepared using different extraction columns. Only suitable for removing bio-organic contaminants with molecular weights greater than 3 million Daltons. Most small molecular organics (such as oils, sugars, pigments, humic acids, etc.) cannot be trapped, and the practical use is of little significance. Special equipment (such as peristaltic pump, switching valve, etc.) needs to be configured to achieve automatic online use. The cost of use is very low. It has been localized, with an average of 1 yuan/sample, which has been domestically produced and the price is very cheap. Very expensive, the price of the device is about 14,000 USD. Consumables must use imported special membranes.
The processing time of the sample is fast, generally fast in a few seconds, generally slow in a few seconds, and takes ten to several tens of minutes. The applicability of organic matter (organic acid, organic amine, sugar, amino acid, etc.) can be applied differently. The analysis object can choose the appropriate extraction column for too long, basically can not be used for ion chromatography, and no relevant reports have been reported.
Product versatility Each manufacturer's products can be used interchangeably. Each manufacturer's products can be used interchangeably. <br> Due to the particularity of ion chromatography, the classic methods for ion chromatography are alkali fusion, dry ashing, oxygen cylinders/oxygen bombs. Combustion method, steam distillation method, high temperature pyrolysis, etc., Ding Xiaojing and Qi Shifen et al. reviewed the new technology of sample pretreatment of ion chromatography, and introduced the latest research progress in this field at home and abroad. In this paper, several different types, such as membrane treatment, solid phase extraction treatment and decomposition treatment, are discussed separately.
Membrane treatment
1.1. Membrane or sand core treatment method <br> Filter membrane filtration sample is the most common aqueous sample pretreatment method for ion chromatography. Generally, if the sample contains granular sample, it can be filtered through 0.45 or 0.22μm microporous membrane. After direct injection. Since the general filter membrane cannot withstand high pressure, membrane filtration can only be used for off-line sample processing. Sometimes online sample processing is required, or the method is used in instrument piping, and a sand core filter must be used. However, the membrane filtration method can only remove particulate insoluble substances. For very small particles or organic macromolecular soluble compounds and metal water-soluble ions, it can still enter the column to interfere with the determination of the sample and stain the column.
In addition, unless the filter or sand core is specially designed for ion chromatography, the filter or sand core will contain a certain amount of inorganic anions and cations. The presence of such ions will affect the trace anions and cations in the aqueous solution. It can cause interference and affect the accuracy of the measurement. Therefore, for trace ion analysis, it is recommended to wash the filter several times with secondary deionized water before the sample is measured, and inject a blank sample, and perform blank background subtraction. Xuantongliang compared the residual anions after washing with four different aqueous membranes [4]. It was found that when the first injection was carried out, the membranes produced by Guangjia were found to contain mg/L of anions. After washing the lotion for more than 5 times, most of the anions on the filter are eluted, and the anion content is basically stabilized. Therefore, the sample can be measured by a blank test.
Due to the limitations of the membrane treatment method, some people have tried dialysis and ultrafiltration in foreign countries. Because the dialysis method requires a relatively long equilibrium time, the cost of ultrafiltration is relatively high, and the removal rate of pollutants is Not completely. Recently, the company's "British Blue" technology is based on the principle of using permeable membrane or ultrafiltration membrane technology to process samples. The osmotic or ultrafiltration membranes used in ICs can only be made with acetate fibers because of their low adsorption to proteins. Other organic solvent-resistant materials such as nitrocellulose membranes and nylon membranes have high protein adsorption properties. Will affect the repeatability of the analysis and the service life of the membrane. However, the disadvantages of the cellulose acetate membrane are: 1. Can only use water and ethanol, can not be compatible with strong organic solvents (will dissolve), so it is not resistant to normal phase and reversed phase solvent; The membrane used by Wantong is 0.2u (about 3 million molecular weight), which can not retain most of the small molecule organic matter, and can only retain substances with a molecular weight of 3 million Daltons, such as suspended particles, macromolecular proteins, etc. Actual IC A large number of small organic substances such as humic acid, fat, oil, etc. are present in the sample. These substances cannot be removed by osmotic or ultrafiltration membranes. For example, milk samples can only be removed by so-called "British Blue" technology. The lack of fat and other small molecules of organic matter can not be solved. Therefore, the use of this technology is not good and limited, but it plays a general role in filtering. If users do not understand this information, they only believe in commercial propaganda, actually make After use, it will be found that the use of "British Blue" technology to process the sample will shorten the service life of the analytical column, because a large number of small molecules of organic matter that cannot be removed by "British Blue" technology will enter the analytical column. Another use of osmosis or ultrafiltration membrane technology The problem is that the peristaltic pump needs to be pressurized and pressurized, which makes the instrument mechanism complicated, high failure rate, troublesome use and high cost (such as membrane replacement, replacement of peristaltic pump silicone tube, pump maintenance, etc.)
1.2. Electrodialysis treatment method <br> The characteristic work in domestic comparison is to use electrodialysis. Compared with other membrane treatment methods, electrodialysis treatment has certain selectivity, so it can not only effectively remove particulate matter and organic matter. Contaminants, but also remove heavy metal ion contaminants. It is one of the most effective methods for processing complex matrix samples.
1.3. Electrolytic Neutralization Method <br> Compared with electrodialysis, the electrochemical electrolysis neutralizer neutralizes high-concentration acids and bases by neutralizing the generated hydrogen ions or hydroxide ions by water electrolysis. The laboratory uses a domestic electrochemical self-regeneration suppressor to allow a high concentration of alkali to pass through the neutralizer, and an ion chromatograph of the ion chromatograph that is inhibited by water electrolysis as a neutralizer plus water electrolysis as a regenerant. As long as the concentration is low enough, the analysis of trace anions in high-concentration alkalis can be achieved, and similar methods can also be used to analyze the trace cations in high-concentration acids. Compared to foreign commercialized neutralizers, our own built-in neutralizers can be used on any type of ion chromatograph, and the entire unit is only 1/40 of the price of imported equipment.
2. Solid phase extraction <br> Solid phase extraction is the most widely used method for pretreatment of ion chromatographic samples in China. For different pollutants in the solution, reverse phase, ion exchange, chelating resin, etc. can be used respectively. The method is carried out, so that the conventional solid phase extraction method and the solid phase micro-extraction method can also be used for the extraction means, but the solid phase micro-extraction method generally utilizes the reverse process of sample concentration and removal of matrix interference on the liquid chromatography, thus Solid phase microextraction is more convenient for use in ion chromatography, and a solid phase microextraction column can be used multiple times.
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With the increasing use of ion chromatography, many samples have been unable to perform ion chromatography analysis using conventional methods of sampling, dilution, and direct injection after filtration. For samples with a large number of complex matrices, ion chromatography can be performed by a suitable method, followed by ion chromatography, which can solve the contamination of the ion column by the complex matrix of the sample. The results and accuracy of the complex matrix samples are measured and the sensitivity of the analytical method is improved.
Regarding the sample pretreatment method, with the improvement of the user level of domestic ion chromatography, a large number of pretreatment methods for ion chromatography have appeared. These methods have the following characteristics: (1) Most of the sample preparations are made of domestic materials. The cost of pretreatment is very low, it is more suitable for China's national conditions, and can be widely used in China; (2) Most sample pretreatment methods use off-line methods, which do not require expensive online equipment; but relatively, sample processing The time is longer, and the amount of samples required is also more. In the current automatic injectors, there are no domestic applications, these methods are more practical; (3) and some sample pretreatment methods appearing internationally, domestic Most of the sample pretreatments appearing from the grassroots units are highly practical; however, there are few related theoretical discussions. Therefore, many domestic sample pretreatment methods can be further discussed from a theoretical perspective. On the other hand, it can also be used for pretreatment of online samples by appropriate improvement, including domestic and foreign instruments.
Comparison of the most commonly used sample preparation techniques
Microfiltration Filtration Solid Phase Extraction Technology Adsorption and Osmosis Technology <br> Manufacturers and Manufacturers of All HPLC and Ion Chromatography Manufacturers of all HPLC, GC and ion chromatography manufacturers are still in use.
Material used 0.22 um polysulfone or nylon membrane C18/RP reverse phase / ion exchange / chelating resin filler 0.2 um acetate membrane organic solvent compatibility compatible with incompatible analysis results with good accuracy. The components that rely on the pressure to ensure analysis can all pass without loss. well. The components that rely on the pressure to ensure analysis can all pass without loss. Different samples and different components have different diffusion coefficients and equilibrium rates on the membrane, so it is difficult to ensure the accuracy, repeatability and recovery of the analytical results.
The field of use is widely used in chromatographic analysis such as IC/HPLC. It is widely used in chromatographic analysis such as IC/HPLC/GC. It is widely used in the life science field for desalination of proteins or peptides and removal of small substance impurities. Rarely used in chromatographic analysis.
The scope of application is only for the removal of particulate matter contamination. Easy to use and cheap. Suitable for more than 90% ion chromatography samples. Manual or automatic online use is possible without adding dedicated equipment. Suitable for a wide range of samples and contaminants, it is currently the best ion chromatography sample preparation technology. Simple to use. Manual or automatic online use is possible without adding dedicated equipment. Different samples can be prepared using different extraction columns. Only suitable for removing bio-organic contaminants with molecular weights greater than 3 million Daltons. Most small molecular organics (such as oils, sugars, pigments, humic acids, etc.) cannot be trapped, and the practical use is of little significance. Special equipment (such as peristaltic pump, switching valve, etc.) needs to be configured to achieve automatic online use. The cost of use is very low. It has been localized, with an average of 1 yuan/sample, which has been domestically produced and the price is very cheap. Very expensive, the price of the device is about 14,000 USD. Consumables must use imported special membranes.
The processing time of the sample is fast, generally fast in a few seconds, generally slow in a few seconds, and takes ten to several tens of minutes. The applicability of organic matter (organic acid, organic amine, sugar, amino acid, etc.) can be applied differently. The analysis object can choose the appropriate extraction column for too long, basically can not be used for ion chromatography, and no relevant reports have been reported.
Product versatility Each manufacturer's products can be used interchangeably. Each manufacturer's products can be used interchangeably. <br> Due to the particularity of ion chromatography, the classic methods for ion chromatography are alkali fusion, dry ashing, oxygen cylinders/oxygen bombs. Combustion method, steam distillation method, high temperature pyrolysis, etc., Ding Xiaojing and Qi Shifen et al. reviewed the new technology of sample pretreatment of ion chromatography, and introduced the latest research progress in this field at home and abroad. In this paper, several different types, such as membrane treatment, solid phase extraction treatment and decomposition treatment, are discussed separately.
Membrane treatment
1.1. Membrane or sand core treatment method <br> Filter membrane filtration sample is the most common aqueous sample pretreatment method for ion chromatography. Generally, if the sample contains granular sample, it can be filtered through 0.45 or 0.22μm microporous membrane. After direct injection. Since the general filter membrane cannot withstand high pressure, membrane filtration can only be used for off-line sample processing. Sometimes online sample processing is required, or the method is used in instrument piping, and a sand core filter must be used. However, the membrane filtration method can only remove particulate insoluble substances. For very small particles or organic macromolecular soluble compounds and metal water-soluble ions, it can still enter the column to interfere with the determination of the sample and stain the column.
In addition, unless the filter or sand core is specially designed for ion chromatography, the filter or sand core will contain a certain amount of inorganic anions and cations. The presence of such ions will affect the trace anions and cations in the aqueous solution. It can cause interference and affect the accuracy of the measurement. Therefore, for trace ion analysis, it is recommended to wash the filter several times with secondary deionized water before the sample is measured, and inject a blank sample, and perform blank background subtraction. Xuantongliang compared the residual anions after washing with four different aqueous membranes [4]. It was found that when the first injection was carried out, the membranes produced by Guangjia were found to contain mg/L of anions. After washing the lotion for more than 5 times, most of the anions on the filter are eluted, and the anion content is basically stabilized. Therefore, the sample can be measured by a blank test.
Due to the limitations of the membrane treatment method, some people have tried dialysis and ultrafiltration in foreign countries. Because the dialysis method requires a relatively long equilibrium time, the cost of ultrafiltration is relatively high, and the removal rate of pollutants is Not completely. Recently, the company's "British Blue" technology is based on the principle of using permeable membrane or ultrafiltration membrane technology to process samples. The osmotic or ultrafiltration membranes used in ICs can only be made with acetate fibers because of their low adsorption to proteins. Other organic solvent-resistant materials such as nitrocellulose membranes and nylon membranes have high protein adsorption properties. Will affect the repeatability of the analysis and the service life of the membrane. However, the disadvantages of the cellulose acetate membrane are: 1. Can only use water and ethanol, can not be compatible with strong organic solvents (will dissolve), so it is not resistant to normal phase and reversed phase solvent; The membrane used by Wantong is 0.2u (about 3 million molecular weight), which can not retain most of the small molecule organic matter, and can only retain substances with a molecular weight of 3 million Daltons, such as suspended particles, macromolecular proteins, etc. Actual IC A large number of small organic substances such as humic acid, fat, oil, etc. are present in the sample. These substances cannot be removed by osmotic or ultrafiltration membranes. For example, milk samples can only be removed by so-called "British Blue" technology. The lack of fat and other small molecules of organic matter can not be solved. Therefore, the use of this technology is not good and limited, but it plays a general role in filtering. If users do not understand this information, they only believe in commercial propaganda, actually make After use, it will be found that the use of "British Blue" technology to process the sample will shorten the service life of the analytical column, because a large number of small molecules of organic matter that cannot be removed by "British Blue" technology will enter the analytical column. Another use of osmosis or ultrafiltration membrane technology The problem is that the peristaltic pump needs to be pressurized and pressurized, which makes the instrument mechanism complicated, high failure rate, troublesome use and high cost (such as membrane replacement, replacement of peristaltic pump silicone tube, pump maintenance, etc.)
1.2. Electrodialysis treatment method <br> The characteristic work in domestic comparison is to use electrodialysis. Compared with other membrane treatment methods, electrodialysis treatment has certain selectivity, so it can not only effectively remove particulate matter and organic matter. Contaminants, but also remove heavy metal ion contaminants. It is one of the most effective methods for processing complex matrix samples.
1.3. Electrolytic Neutralization Method <br> Compared with electrodialysis, the electrochemical electrolysis neutralizer neutralizes high-concentration acids and bases by neutralizing the generated hydrogen ions or hydroxide ions by water electrolysis. The laboratory uses a domestic electrochemical self-regeneration suppressor to allow a high concentration of alkali to pass through the neutralizer, and an ion chromatograph of the ion chromatograph that is inhibited by water electrolysis as a neutralizer plus water electrolysis as a regenerant. As long as the concentration is low enough, the analysis of trace anions in high-concentration alkalis can be achieved, and similar methods can also be used to analyze the trace cations in high-concentration acids. Compared to foreign commercialized neutralizers, our own built-in neutralizers can be used on any type of ion chromatograph, and the entire unit is only 1/40 of the price of imported equipment.
2. Solid phase extraction <br> Solid phase extraction is the most widely used method for pretreatment of ion chromatographic samples in China. For different pollutants in the solution, reverse phase, ion exchange, chelating resin, etc. can be used respectively. The method is carried out, so that the conventional solid phase extraction method and the solid phase micro-extraction method can also be used for the extraction means, but the solid phase micro-extraction method generally utilizes the reverse process of sample concentration and removal of matrix interference on the liquid chromatography, thus Solid phase microextraction is more convenient for use in ion chromatography, and a solid phase microextraction column can be used multiple times.
Welcome to Beijing hundred O'Brien Wei Biotechnology Co., Ltd, the site belongs to Beijing hundred O'Brien Wei Biotechnology Co., Ltd., the unit now provides microbial strains and cell and other related products inquiries, advice, ordering, after-sales service! With a number of domestic and foreign research and development units, biomedicine, third-party testing institutions, research institutes have a good and stable long-term cooperative relationship! Welcome customers to inquire!
Http://
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