JP2011209250A - Sample introduction device for induction coupling plasma analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve accurate and rapid qualitative analysis, quantitative analysis, and isotope ratio analysis of an element by preventing pollution (memory effect) caused by a sample solution attached to or accumulated in an induction coupling plasma analyzer or a sample introduction device.SOLUTION: The sample introduction device includes a replaceable sample solution introduction nozzle 23 branched from a sample introduction tube 26, and reduces a memory effect by simultaneously introducing a sample solution and a washing solution. An advantage thereof is that the time required for washing after measurement of the sample solution can be remarkably reduced and further precise element analysis is available.

Description

  The present invention relates to a sample introduction device for an inductively coupled plasma analyzer that enables quick and accurate “qualitative analysis / quantitative analysis / isotope ratio analysis” of elements. In the field of elemental analysis, “qualitative analysis” measures what elements are contained in a sample, “quantitative analysis” measures the amount of elements contained in a sample, “isotope ratio analysis” Refers to measuring the abundance ratio of an isotope of a certain element contained in a sample. “Isotope ratio analysis” is included in quantitative analysis in a broad sense, but is often distinguished from it, so it is described separately from quantitative analysis here. Hereinafter, “qualitative analysis / quantitative analysis / isotope ratio analysis” of elements will be collectively referred to as “elemental analysis”.

  An inductively coupled plasma analyzer is an analyzer of elements in a solution, and performs an inductively coupled plasma emission analyzer (hereinafter referred to as ICP-AES) that performs qualitative analysis of elements from the wavelength of light and performs quantitative analysis from the intensity of light. And an inductively coupled plasma mass spectrometer (hereinafter referred to as ICP-MS) that performs qualitative analysis of elements from the mass of ions and performs quantitative analysis and isotope ratio analysis from ion count rates and counts. Both consist of a nebulizer, spray chamber, plasma torch, work coil, high frequency power supply, and detector. A sample introduction tube is connected to the nebulizer, and the sample solution and the cleaning solution introduced into the sample introduction tube are fed by an ironing pump or the like and guided to the nebulizer. The nebulizer serves to spray the introduced sample solution or cleaning liquid in the form of a mist (hereinafter, the sample introduction tube to the nebulizer are collectively referred to as a sample introduction device). The spray chamber serves to screen the particle size of the atomized mist. A work coil is wound around the tip of the plasma torch, and high frequency power is applied to the work coil by a high frequency power source. By this high frequency power, the sample solution and cleaning liquid introduced and sprayed into the plasma torch become plasma together with a gas such as argon introduced at the same time. The detector performs elemental analysis from light or ions.

  A conventional technique will be described with reference to FIG. In FIG. 1, 1 is a sample solution, 2 is a cleaning liquid, 3 is a sample introduction tube, 4 is a squeezing pump for liquid feeding, and 5 is a nebulizer. The sample solution 1 or the cleaning solution 2 passes through the sample introduction tube 3 and reaches the nebulizer 5. After the measurement of the sample solution, the sample introduction tube is placed in the washing solution container and sprayed with the washing solution. After sufficient washing, the sample introduction tube is again placed in the sample solution vessel and the sample solution is introduced. That is, the sample solution and the cleaning solution are introduced alternately.

  However, the conventional technique has a problem that the sample introduction tube and the inductively coupled plasma analyzer are contaminated (hereinafter referred to as a memory effect) due to adhesion or retention of the sample solution. In the conventional sample introduction device, the sample solution passes through the sample introduction tube and is introduced into the inductively coupled plasma analyzer. At this time, some elements such as boron are part of the sample introduction tube and inductively coupled plasma analyzer. It is easy to stay in. Therefore, when analyzing a plurality of sample solutions, the remaining sample solution causes an increase in background intensity, which adversely affects the accuracy of subsequent analysis results of the sample.

  This problem is particularly serious in an apparatus that performs an extremely small amount of elemental analysis at the ppt level, such as ICP-MS. For this reason, in the conventional sample introduction apparatus, it is necessary to spray the cleaning liquid for a long time each time the sample solution is measured in order to suppress the memory effect.

As a measure to improve this, a sample introduction device (Patent Document 1) that does not use parts such as hexagonal valves and rotors that easily retain sample solutions, or two nebulizers and sample introduction pipes are switched for each sample. A sample introduction device (Patent Document 2) that cleans the other is disclosed. However, the apparatus of Patent Document 1 does not take measures against the memory effect on the sample introduction tube. The device of Patent Document 2 requires two nebulizers in principle. Neither device provides a measure for the memory effect in the spray chamber.

JP-A-8-055601 JP-A-5-142124

  The problem to be solved is a reduction in the memory effect, which is an obstacle to speed and accuracy when elemental analysis is performed by an inductively coupled plasma analyzer.

  The present invention is to efficiently reduce the memory effect by introducing the sample solution and the cleaning solution at the same time.

  The sample introduction apparatus of the present invention includes a replaceable sample solution introduction nozzle branched from the sample introduction tube, and simultaneously introduces the sample solution and the cleaning solution, thereby reducing the memory effect. Thereby, after measurement of the sample solution, there is an advantage that time required for cleaning can be greatly reduced and more accurate elemental analysis can be performed.

FIG. 1 is an explanatory view showing an outline of a conventional sample introduction apparatus. FIG. 2 is an explanatory view showing an outline of the sample introduction apparatus of the present invention. FIG. 3 is an explanatory diagram comparing the cleaning effects of the conventional sample introduction apparatus and the sample introduction apparatus of the present invention.

  The objective of introducing the sample solution and the cleaning solution at the same time was realized with the minimum number of parts. FIG. 2 is a schematic view of an embodiment of the apparatus of the present invention, in which 21 is a sample solution, 22 is a cleaning liquid, 23 is a replaceable nozzle, 24 is a cleaning pump for feeding a cleaning liquid, and 25 is a cleaning liquid and a sample. An ironing pump for solution feeding, 26 is a sample introduction tube, and 27 is a nebulizer.

  The flow of analysis performed by the inductively coupled plasma mass spectrometer using the present invention will be described. The sample solution 21 and the cleaning liquid 22 pass through the sample introduction tube 26 and reach the nebulizer 27. The sample solution and the cleaning solution are simultaneously sucked by the squeezing pumps 24 and 25 and introduced into the nebulizer. After the measurement, by removing the replaceable nozzle 23 and closing the lid, the path can be cleaned by introducing only the cleaning liquid. When measuring another sample solution in succession, it is possible to measure the next sample solution by installing a new replaceable nozzle after introducing the cleaning solution until the signal intensity becomes 1/500 of the sample solution spray. Become. Since the main body of the present invention is the method for introducing the sample solution and the cleaning liquid, description of the path after the nebulizer is omitted.

  By adopting such a method of introducing the sample solution and the cleaning liquid, rapid elemental analysis can be performed without requiring long-time cleaning. Furthermore, the background intensity can be reduced, and accurate elemental analysis can be performed.

[Example 1]
As a sample, NIST SRM 951a, a certified reference material for boric acid (Standard Reference Materials, SRM) supplied by National Institute of Standards and Technology, NIST of the United States, was used. Boric acid powder was dissolved in pure water and diluted to have a B concentration of 200 ppb when introduced into ICP-MS to prepare an aqueous boric acid solution. Using this boric acid aqueous solution as a sample solution, spraying the ICP-MS for about 30 minutes using a conventional sample introduction apparatus or the present invention, then introducing the cleaning solution, and measuring the cleaning time required until the signal intensity sufficiently decreases. . As the cleaning liquid, a mannitol-ammonia aqueous solution known as a boron cleaning liquid was used. It adjusted so that it might become a 0.25 mass% mannitol density | concentration in 0.1 M ammonia aqueous solution. Here, the criterion for judging that the signal intensity has sufficiently decreased is that the signal intensity is reduced to 1/500 of the time when the sample solution is sprayed. The actual measurement value in the measurement is shown in FIG.

The instrument used for the measurement is ICP-MS4500 manufactured by Yokogawa Analytical Systems. The measurement conditions are shown below.
RF output: 1340W
RF matching: 2V
Carrier gas (Ar): 1.11 L / min
Pump flow rate (during measurement): 0.3 mL / min
Pump flow rate (during washing): 0.9 mL / min
Spray chamber: Scott type (polyethylene)
Spray chamber temperature: 2 ° C
Nebulizer: Cross flow type (polyethylene)
Mass spectrometer: Quadrupole measurement mode: Number of measurement points for isotope measurement: 1 (peak top only)

[Comparative Example 1]
The cleaning time required until the signal intensity became 1/500 of that during spraying of the sample solution was measured under the same conditions as in Example 1 except that the conventional sample introduction apparatus (FIG. 1) was used. The actual measurement values are shown in FIG.

When a conventional sample introduction apparatus was used, it took 20 minutes or more for the signal intensity to become 1/500 that of the sample solution spray. On the other hand, in the case of using the sample introduction apparatus of the present invention, the signal intensity decreased to 1/500 when the sample solution was sprayed after about 4 minutes of washing time. From the above, it was confirmed that the time required for cleaning can be significantly reduced by using the sample introduction apparatus of the present invention, as compared with the case of using the conventional sample introduction apparatus. This is very useful because it can process a large number of analytical samples quickly.

  A sample solution and a cleaning solution can be introduced simultaneously by a sample introduction tube and a replaceable nozzle branched from the sample introduction tube, which can be applied to analysis of a sample in which a memory effect easily occurs.

DESCRIPTION OF SYMBOLS 1 Sample solution 2 Cleaning liquid 3 Ironing pump 4 Sample introduction pipe 5 Nebulizer 21 Sample solution 22 Cleaning liquid 23 Replacement type nozzle 24 Ironing pump (for liquid supply of cleaning liquid)
25 Ironing pump (for feeding cleaning solution and sample solution)
26 Sample introduction tube 27 Nebulizer

Claims (4)

A device for introducing a sample solution into an inductively coupled plasma analyzer that performs qualitative analysis, quantitative analysis or isotope ratio analysis of elements in a solution, a sample container for containing the sample solution, and the sample solution being an inductively coupled plasma analyzer A sample introduction device for an inductively coupled plasma analyzer, comprising: a washing solution container containing a washing solution for washing a path until the sample is introduced into the tube; and a sample introduction tube that sucks the washing solution and guides it to the inductively coupled plasma analyzer.   Features a replaceable sample solution introduction nozzle that branches from the sample introduction tube, connects to the sample container, sucks the sample solution, and guides it to the inductively coupled plasma analyzer, and simultaneously introduces the sample solution and the cleaning solution. The sample introduction device for an inductively coupled plasma analyzer according to claim 1.   About the sample introduction tube, a squeeze pump is provided at two locations between one end immersed in the cleaning liquid and a portion where the nozzle for introducing the sample solution is joined, and between the joined portion and the sample sprayer (nebulizer). The sample introduction apparatus for an inductively coupled plasma analyzer according to claim 1 or 2, wherein the introduction amount of the cleaning liquid and the cleaning liquid and the sample solution can be controlled to be constant. The sample introduction device for an inductively coupled plasma analyzer according to any one of claims 1 to 3, wherein the target element for qualitative analysis, quantitative analysis or isotope ratio analysis is boron.

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