JP3079255B2 - Online interference component removal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-ES), and liquid chromatography mass spectrometry (LC-MS).
When analyzing trace components in high salt concentration samples such as seawater and alkali-melted sample liquids by such methods as above, this device converts on-line high salt concentration components that cause interference and lowers sensitivity to non-interfering components. About.

[0002]

2. Description of the Related Art Conventionally, when analyzing a sample having a high salt concentration by ICP-MS or ICP-ES, the sample is introduced into plasma without pretreatment, or the sample is introduced after being diluted with water. Was.
In addition, alkali and alkaline earth metals such as sodium and magnesium, which are the main components with high salt concentration, are not adsorbed, and the column selectively adsorbs only heavy metals such as lead, cadmium, copper, and zinc to be analyzed. After flowing a sample to adsorb heavy metals, a method is adopted in which an acid is passed through a column to elute the heavy metals and introduce them into plasma. In LC-MS, even when an electrolyte with a high salt concentration is used as the eluent, the analyte and the high-concentration electrolyte are introduced into the mass spectrometer together.

[0003] Conventionally, as an online desalination apparatus,
There is an ion chromatograph suppressor, which removes interfering anions from the cations to be analyzed through an anion exchange membrane and, at the same time, exchanges the counterions of the cations to be analyzed to produce components with high electrical conductivity. Convert to increase sensitivity (or remove interfering cations from the anion to be analyzed through a cation exchange membrane, and at the same time, convert to a component with higher electrical conductivity by exchanging the counter ion of the anion to be analyzed) Function to increase the sensitivity). In other words, although it has a sensitizing effect functionally, it has only the function of removing interfering ions having the opposite charge to the ion to be analyzed. The membrane is a cation exchange membrane when the object to be analyzed is an anion. For this reason, it cannot be used when the charges of the ion to be analyzed and the interfering ion are the same.

[0004]

When a sample is introduced into a plasma without pretreatment by ICP-MS or ICP-ES, a change in ionization efficiency due to the introduction of a high salt concentration component (ionization interference and ) And interference of molecular ions derived from high salt concentration components, nebulizers and sampling cones,
Significant decrease in sensitivity due to clogging of skimmer cones and contamination of ion lens system. When the sample is diluted with water, the interference caused by the high salt concentration component is reduced, but the analysis target component is also diluted, so that the low concentration component is below the detection limit and cannot be analyzed. When a separation method using a column is used as a pretreatment method, the operation is complicated and time-consuming. When an electrolyte is used as the eluent in LC-MS, the sensitivity also decreases because the ionization efficiency of the mass spectrometer decreases. When a suppressor is used, only the interfering ions having the opposite charge can be removed, so that there is a problem that, for example, Na ⁺ that interferes with the analysis of Pb ²⁺ and Cd ²⁺ in seawater cannot be removed. An object of the present invention is to provide an apparatus that solves the above-mentioned problem by continuously removing a high-salt-concentration component that interferes when a high-salt concentration sample is introduced into an analyzer.

[0005]

In order to achieve the above object, according to the present invention, when the analyte is a cation and the high salt concentration interfering component is also a cation, only the cation to be analyzed is replaced with a chelating reagent or a cation. After conversion into an electrically neutral or anionic form by an ion-pairing reagent, the cation-interfering component in the sample solution and the cation-non-interfering component in the removing solution are exchanged through a cation exchange membrane. The main component composition of the analysis sample solution is converted so as not to interfere. When the analyte is an anion and the high salt concentration interfering component is also an anion, after only the anion to be analyzed is electrically converted to a neutral or cation form by a chelating reagent or an ion pairing reagent, By exchanging the anion interfering component in the sample solution and the anion non-interfering component in the removing solution through the anion exchange membrane,
The main component composition of the analysis sample solution is converted. Furthermore, when both high concentrations of cations and anions are interfering components,
After converting only the ions to be analyzed (either cations or anions) into an electrically neutral form using a chelating reagent or an ion pairing reagent, the cation interfering component in the sample solution is passed through a cation exchange membrane. By exchanging the cation non-interfering components in the removing solution with the anion exchange component, and exchanging the anion interfering components in the sample solution and the anion non-interfering components in the removing solution through the anion exchange membrane, Convert the main component composition. When the component to be analyzed is originally nonionic, it is not necessary to add a chelating reagent or an ion pair forming reagent.

A dilute sulfuric acid solution or a dodecyl sulfuric acid solution is often used as a cation-interfering component removing solution, but another acid may be used. For example, when dilute sulfuric acid is used, a cation interfering component (eg, Na ⁺ ) and H ^{+ of the} dilute sulfuric acid are exchanged via the cation exchange membrane. Sodium hydroxide solution is often used as a solution for removing anion-interfering components.
In the case of analysis by P-MS or ICP-ES, since NO ₃ ^- and HCO ₃ ^- also have little interference, a NaNO ₃ , HNO ₃ , NaHCO ₃ solution or the like may be used. For example, when using sodium hydroxide,
Anionic interfering components (eg, Cl ⁻ ) and OH ^{− of} sodium hydroxide exchange via the anion exchange membrane. Also, for example, when dilute sulfuric acid and sodium hydroxide are used as the respective removing solutions, H ⁺ and OH ⁻ exchange with the interfering components, respectively, and enter into the sample solution. Because it is H ₂ O, it does not disturb the measurement. When dilute sulfuric acid and NaNO ₃ solution are used, H ⁺ and NO ₃ ⁻ enter the sample solution, but HNO ₃ hardly interferes with ICP-MS or ICP-ES.

[0007]

In the apparatus constructed as described above, the cation exchange membrane functions to exchange the cation interfering component in the sample solution with the cation non-interfering component in the removing solution. The removing solution constantly supplies cations which do not disturb the analysis to the cation exchange membrane, and at the same time functions to remove the cation interfering components which have passed through the cation exchange membrane out of the system. The anion exchange membrane functions to exchange anion blocking components in the sample solution and non-blocking components in the removing solution. The removing solution constantly supplies anions which do not disturb the measurement to the anion exchange membrane, and at the same time, functions to remove the anion interfering components which have passed through the anion exchange membrane to the outside of the system.

The chelating reagent and the ion-pair forming reagent form a complex or an ion pair with the analyte, and when the interfering component is a cation, convert the analyte into an electrically neutral or anionic compound. If the interfering component is an anion, the analyte is exchanged for an electrically neutral or cationic compound.If the interfering component is both a cation and an anion, the analyte is To an electrically neutral compound. If the component to be analyzed is originally neutral, it need not be added.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings based on embodiments. FIG. 1 is a configuration diagram of the online interference component removing apparatus of the present invention. The on-line interference component removing apparatus according to the present invention includes a sampling valve 1 for collecting an analysis sample (for example, seawater) in a flow of a dilute nitric acid solution.
A sampling valve 2 for separating the chelating reagent into the flow of the dilute nitric acid solution, a liquid sending pump 3 for flowing the analysis sample and the chelating reagent, an analysis sample flow path 4 for flowing the analysis sample and the chelating reagent, It is mainly composed of a reaction coil 5 and an ion exchange section 6 provided sequentially in the middle of the analysis sample flow path 4. The reaction coil 5 mixes and reacts the analysis sample and the chelating reagent fractionated by the sampling valves 1 and 2 to make the ions to be analyzed in the analysis sample solution electrically neutral. The ion exchange section 6 includes a cation exchange membrane 7 and an anion exchange membrane 8 disposed facing the analysis flow channel so as to sandwich the analysis sample flow channel 4 from both sides. , 8 the sample solution is pumped. A cation removing liquid supply flow path 9 and an anion removing liquid supply flow path 10 are provided so as to communicate with the ion exchange unit 6. The cation-removing liquid supply flow path 9 and the anion-removing liquid supply flow path 10 carry cation-disturbing components and anion-disturbing components in the sample solution that have passed through the cation exchange membrane 7 and the anion exchange membrane 8, respectively. At the same time, other cations and anions that do not disturb the analysis are supplied to the analysis sample solution via the cation exchange membrane 7 and the anion exchange membrane 8, respectively.

FIG. 2 shows a sample, Cu, which is a component to be analyzed.
^{2+, +} cations interfering components Na, anionic interfering components Cl ^{chromatography} is sampled, the chelating reagent HL mixed reaction solution indicates a state of the ion exchange when it is introduced into the ion exchange unit 6. When, for example, dilute sulfuric acid H ₂ SO ₄ is used as the cation interfering component removing solution, the cation interfering component Na ⁺ and the dilute sulfuric acid H ⁺ are exchanged via the cation exchange membrane. For example, when sodium hydroxide NaOH is used as a liquid for removing anion interference components, anion interference components are removed.
Cl ^- and OH Sodium hydroxide ^- is exchanged via the anion exchange membrane, H ⁺ and OH ^- by replacing with each interference component, but enters the sample solution, it reacts H ₂ Since it becomes O, it does not disturb the measurement.

In FIGS. 1 and 2, an on-line interference component removing apparatus for transmitting and removing high concentrations of cations and anions which interfere with the analysis from the analysis sample solution has been described.
In the cation on-line interference component removal apparatus for permeating and removing only high-concentration cations that interfere with analysis from the analysis sample solution, the anion exchange membrane and the anion supply / removal line are unnecessary in FIG. Conversely, in the anion on-line interference component removal apparatus for permeating and removing only high-concentration anions that interfere with analysis from the analysis sample solution, the cation exchange membrane and the cation supply / removal line are unnecessary in FIG. is there. In addition, in order to transmit and remove high concentrations of cations and anions that interfere with analysis from the analysis sample solution, cation exchange membranes and anion exchange membranes are provided on both sides of the analysis sample flow path in FIG. Instead of the ion exchange section, a cation exchange section having only a cation exchange membrane communicating with the cation removal supply flow path and an ion exchange section having only an anion exchange membrane communicating with the anion supply flow path are provided. And may be arranged in series along the analysis sample flow path.

Further, a description will be given of an apparatus in which the on-line interference component removing apparatus of FIG. 1 is applied to a case where heavy metals in seawater are measured by ICP-MS or ICP-ES. PH2 as sample
After dispensing appropriate amounts (eg, 0.1 ml) of the seawater and the APDC 0.1% solution respectively stored in the sampling valves 1 and 2,
By switching the sampling valve, the seawater sample and the chelating reagent are respectively introduced into the flow path of dilute nitric acid (for example, 5 mM HNO ₃ ). After the seawater sample and the chelating reagent are mixed and reacted in the reaction coil 5, the mixture is sent to the ion exchange unit 6. The sample solution coming out of the ion exchange section 6 is introduced into ICP-MS or ICP-ES for analysis. Table 1 shows the results of analysis by ICP-MS when the on-line interference component removing apparatus of the present invention was used (column No. 4 in Table 1) and when it was not used (column No. 1 in Table 1). The column numbers No. 2 and No. 3 in the table are the results of analysis without adding a chelating reagent. The results of column numbers No. 1 and No. 2 are values obtained by analyzing natural seawater, and the results of column numbers No. 3 and No. 4 show that the concentrations of each heavy metal This is the value when the sample to which the standard solution was added was analyzed. Here, as an example, the main cation interfering components in seawater, Na ⁺ and Mg2 ⁺ , and the analyte, Cu
The signal intensities of ²⁺ , Cd ²⁺ and Pb ²⁺ were shown. From this table, 99.99% of Na ⁺ and Mg ^{2 +} which are interfering components due to ion exchange
% Or more (signal intensity is ²³ Na ⁺
In case of, reduced from 2 × 10 ⁹ to 1 × 10 ⁵ , In case of ²⁵ Mg ²⁺ , 2 × 1
0 ⁸ to 5 × 10 ³ ). In addition, the analysis target component C
If u ²⁺ , Cd ²⁺ , and Pb ²⁺ are not complexed by the chelating agent, they will be removed in the same manner as Na ⁺ and Mg ^{2 +} (result of column No. 3). It can be seen that by being converted to a neutral compound, it was introduced into the plasma without being removed from the sample solution (result of column No. 4).
Large interfering components, for example, Na ⁺ is present in large amounts, Na ⁺ and Ar molecular ions ⁽⁴⁰ Ar ²³ Na ⁺⁾ is generated a plasma gas, which overlaps a signal to match the ⁶³ Cu ⁺ a mass number of 63 Interference ( ⁶³ Cu ^{+ in} column No. 1 is 1 × 10 ⁵ ). C
natural isotopic ratio of u ⁽⁶³ Cu / ⁶⁵ Cu) is 7: should be 3, the Na ⁺ is not removed, a large outlier from this ratio. On the other hand, when the interfering component was removed, a value almost close to the natural isotope ratio was obtained, indicating that interference by molecular ions was removed.

[Table 1]

When arsenic in seawater is analyzed by ICP-MS, chloride ions (Cl ⁻ ) in seawater and diatomic ions of Ar ( ⁴⁰ Ar ³⁵ Cl ⁺ ), which is a plasma gas, have a mass number of arsenic of 75 ( ⁷⁵ As ⁺ )
Overlap with and cause great interference. In seawater, arsenic exists in the form of anions such as arsenite and arsenite, but is also converted to a neutral compound by reacting with a chelating reagent.
Table 2 shows the results of analysis by ICP-MS in the same manner as described above. Table 2 shows the major interfering anion components in seawater
95% or more of Cl ^- or Br ^- is removed (signal intensity
³⁵ Cl ^- decreases when the 1 × 10 ⁷ to 4 × 10 ⁵ of, ⁷⁹ Br ^- in the case 4 × 1
0 drops ⁵ from 2 × 10 ^3), and arsenic is converted into electrical complex neutral by APDC, you can see that this is introduced into the plasma without being removed from the sample solution (column number N
o.4). If Cl ^- is present in large quantities, even if As is not present, 1.4
The value was × 10 ³ (column number No. 1), indicating that Cl ⁻ significantly interfered with the analysis of As. In the above method,
Elements that form a complex with APDC and become electrically neutral, for example, As, Cd, Cu, Co, Ni, Fe, Cr, Mn, Mo, Sb, Pb, Zn
Elements etc., Na ⁺ is the major salt in seawater, Mg ^2+, Cl ^-,
Analysis can be performed online without interference from Br- ^{and the} like. Further, if another chelating reagent such as oxine is used instead of APDC, the kind of element that can be analyzed can be changed.

An example of measuring trace amounts of Mg ²⁺ and Ca ²⁺ in high concentration salt water used in the soda industry by ICP-ES. When high salt solution is mixed and reacted with an EDTA solution (eg, 0.1%) as a chelating reagent, Mg ²⁺ and Ca ²⁺ become MgEDTA ^2- and CaEDTA, respectively.
It is converted to the ^2- anion form. In ICP-ES, high concentration
Cl ^- because no interference is introduced, there needs to be removed is only cations Na ^+. Therefore, in this case, Na ⁺ is removed from the analysis sample solution using the apparatus described in the cation on-line interference component removal apparatus for transmitting and removing only high-concentration cations that hinder analysis. . If dilute sulfuric acid is allowed to flow as a removing solution, H ⁺ exchanges with Na ⁺ via a cation exchange membrane. As a result, Cl ^-, S
O ₄ ^2-, ClO ^{₂ -} to (included in saline as an electrolyte by-products) are each HCl, is introduced as the acid of H ₂ SO _4, HClO _2,
It does not clog the nebulizer or the tip of the plasma torch, and does not interfere with the measurement of Mg and Ca in ICP-ES.

[0015]

As described above, the interference component removing apparatus of the present invention converts an ion to be analyzed into an ion having a charge opposite to that of an electrically neutral or interfering ion, and then disturbs the ion which interferes with the analysis. Removal of on-line by an ion exchange membrane makes it possible to analyze trace heavy metals in high salt concentration samples such as seawater and alkali melting solutions by ICP-MS and ICP-ES. Also, in LC-MS, by removing the electrolytes (salts) that cause the decrease in ionization efficiency on-line, it is possible to ionize physiologically active substances and environmental pollutants with high efficiency, improving the analysis sensitivity. effective. Further, the present invention enables the removal of components that interfere with the measurement on-line, so that the analysis time is significantly reduced and the complicated pretreatment and separation operations are saved.

[Table 2]

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an on-line interference component removing apparatus of the present invention.

FIG. 2 is an explanatory diagram of a reaction occurring in the on-line interference component removing apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sampling valve (for sample) 2 Sampling valve (for chelating reagent) 3 Liquid sending pump 4 Analysis sample flow path 5 Reaction coil 6 Ion exchange part 7 Cation exchange membrane 8 Anion exchange membrane 9 Cation removal liquid supply flow path 10 Anion removal liquid supply channel

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-53-149182 (JP, A) JP-A-3-144356 (JP, A) JP-A-57-74660 (JP, A) JP-A-2- 66450 (JP, A) Japanese Utility Model Showa 60-179850 (JP, U) Japanese Patent Publication No. 2-25146 (JP, B2) Environmental Chemistry, Vol. 5, No. 2, pp. 360-361 (1995) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) G01N 1/00-1/34 G01N 21/62-21/74 G01N 30/00-30/96

Claims (4)

(57) [Claims] An analysis sample flow path through which an analysis sample solution flows, and an ion to be analyzed, which is provided in the middle of the analysis sample flow path, reacts with a chelating reagent or an ion pair forming reagent to be electrically neutralized. A reaction coil for converting into a form, an ion exchange section provided in the middle of the analysis sample flow path, and a high concentration of cations provided in the ion exchange section and obstructing analysis from the analysis sample solution. And a cation exchange membrane and an anion exchange membrane for permeating and removing anions, respectively, and simultaneously transporting the interfering ions permeating the cation exchange membrane and the anion exchange membrane out of the ion exchanger, A cation removing solution supply flow path and an anion removing solution supply flow for supplying different cations and anions that do not disturb the analysis to the analysis sample solution through the cation exchange membrane and the anion exchange membrane, respectively. And an on-line interference component removing device. 2. An analysis sample flow path for flowing an analysis sample solution, and an ion to be analyzed, which is provided in the middle of the analysis sample flow path, reacts with a chelating reagent or an ion pair forming reagent to be electrically neutral or neutral. A reaction coil for converting to an anion form, an ion exchange section provided in the middle of the analysis sample flow path, and a high-concentration positive electrode provided in the ion exchange section and obstructing analysis from the analysis sample solution. A cation exchange membrane for permeating and removing ions, and a cation exchange membrane that transports interfering ions that have passed through the cation exchange membrane to the outside of the ion exchanger and simultaneously removes another cation that does not interfere with analysis. And a cation removal liquid supply channel for flowing cations to be supplied to the analysis sample solution through the sample. 3. An analysis sample flow path through which an analysis sample solution flows, and an ion to be analyzed, which is provided in the middle of the analysis sample flow path, reacts with a chelating reagent or an ion pair forming reagent to be electrically neutral or neutral. A reaction coil for converting to a cation form, an ion exchange section provided in the middle of the analysis sample flow path, and a high-concentration shade which is provided in the ion exchange section and interferes with analysis from the analysis sample solution. An anion exchange membrane for permeating / removing ions, and transporting interfering ions permeating the anion exchange membrane out of the ion exchanger, and simultaneously exchanging another anion that does not interfere with the analysis. An on-line interference component removing device, comprising: an anion removing solution supply flow path for flowing an anion to be supplied to an analysis sample solution through a membrane. 4. An analysis sample channel through which an analysis sample solution flows, and an ion to be analyzed disposed in the middle of the analysis sample channel reacting with a chelating reagent or an ion pair forming reagent to be electrically neutralized. A cation exchange section and a cation removal supply flow path according to claim 2, which are disposed in the middle of the analysis sample flow path; An on-line interference component removing device comprising an ion supply channel, wherein the cation exchange section and the anion exchange section are arranged in series along the analysis sample channel.