PL206488B1 - Method for the cleaning of the microcapillary nebulizer - Google Patents

Description

(21) Filing Number: 378089 ^{(51) Int.Cl.}

B08B 3/04 (2006.01) G01N 27/62 (2006.01)

Patent Office of the Republic of Poland (22) Date of filing: November 18, 2005 (54)

The method of washing the microcapillary nebulizer

(43) Application was announced: May 28, 2007 BUP 11/07 (73) The right holder of the patent: INSTITUTE OF APPLIED OPTICS, Warsaw, PL (45) The grant of the patent was announced: August 31, 2010 WUP 08/10 (72) Inventor (s): ANDRZEJ RAMSZA, Warsaw, PL

PL 206 488 B1

Description of the invention

The present invention relates to a method of cleaning a microcapillary nebulizer.

One of the basic methods of introducing analytical liquid samples, including old sample solutions, to excitation sources in analytical spectroscopic techniques such as flame atomic absorption spectrometry, plasma excitation emission spectrometry or plasma excited mass spectrometry is nebulization, i.e. obtaining an aerosol of the sample in working gas.

Various types of devices (nebulizers) are known for this purpose, among which the most popular are pneumatic nebulizers (described, among others, in such items of scientific literature as:

1. K. Jankowski, "Microwave induced plasma as a source of excitation in spectrochemical analysis. Properties and applications, pp. 16 - 24, Publishing House of the Warsaw University of Technology,

Warsaw, 2001; 2. J.S. Babis, J.M. Kacsir, M.B. Denton, Appl. Spectrosc..43. 786 (1989); 3. K. Jankowski, D. Karmasz, A. Ramsza, L. Starski, A. Waszkiewicz, Spectrochim. Acta, Part B, 52, 1801 (1997)), which can be divided into:

- cross nebulizers

- coaxial nebulizers

- high pressure nebulizers

- Babbington type nebulizers

A characteristic feature of the first three types of nebulizers is the flow of the analyzed solution (analyte) through capillaries with diameters from 50 - 100 nm in cross and coaxial nebulizers and with much smaller diameters in the case of high pressure nebulizers. This is often the cause of their blockage by sediments or salt crystals falling out of the solution. Moreover, these nebulizers have a relatively low efficiency (for the first two, less than 5% of the analyte is converted to an aerosol), as well as the tertiary aerosol droplet size distribution (i.e. the aerosol emerging from the fog chamber) is shifted towards droplets with a diameter of 10-20 μm.

Washing these nebulizers always involves changing the agalite flowing through the capillary into a washing solution.

Analytical applications of Babbington type nebulizers include:

- V-groove nebulizers

- frit nebulizers

- microcapillary nebulizers (also called microcapillary nebulizers)

In nebulizers of this group, the analyte always flows freely in a thin layer through a specially created open channel, while the working gas flows through a capillary or numerous capillaries, breaking drops from the liquid layer. This prevents the nebulizers of this group from being blocked by solid impurities or precipitating crystals. Moreover, in frit and microcapillary nebulizers high efficiencies are obtained, even above 95% of the primary and depending on the fog chamber used, even up to 50% of the tertiary aerosol, and analytically advantageous droplet size distribution with diameters below 2 nm.

One problem for frit and microcapillary nebulizers are the so-called memory effects and the associated nebulizer wash times associated with their elimination. Washing is always done by changing the pumped analyte to a washing solution. For frit nebulizers, depending on the type of analyte, this time can be up to a dozen, and in extreme cases, several dozen minutes; for microcapillary nebulizers from several tens of seconds to several minutes.

Physically, the problem is that some amounts of the analyte penetrate the capillaries in the microcapillary plate due to cohesive forces, even though the gas flow direction is opposite to that of the penetrating analyte.

The essence of the invention is the method of cleaning the microcapillary nebulizer, which consists in introducing the following sequence of actions: after the measurement, the tube which supplies the analyte to the nebulizer is transferred to the vessel with the washing solution (the washing solution is selected depending on the composition of the analyte - it may be e.g. dilute acid in which the sample is digested, or e.g. a suitably selected organic solvent in the case of organic samples). During this time, as well as during the measurement, the working gas flows through the microcapillary plate. After the time necessary for pumping the washing solution into the plate, once it has been washed by the washing solution, the gas supply to the nebulizer is shut off for a few seconds, preferably by means of a solenoid valve blocked with the nebulizer. During this time, the pressure difference

The pressure on both sides of the microcapillary plate drops to zero and the washing solution flows more easily into the capillaries, washing away the residual analyte from them. The next step is to reopen the gas flow, which allows the washing solution to be pushed out of the capillaries along with the impurities remaining in the capillaries during the measurement. It is advantageous to carry out this sequence of actions 2-3 times.

In an embodiment of the invention, the method of washing the microcapillary nebulizer is carried out as follows: after the measurement, the tube which supplies the analyte to the nebulizer is transferred to the vessel with the washing solution. During this time, as well as during the measurement, the working gas flows through the microcapillary plate. The next step is a short-term, preferably 1-2 s, delivery of the washing solution to the pressure side of the plate from an independent pump, without interrupting the gas flow. During this time, the washing solution enters the capillaries and flows through them, at the same time washing away the impurities remaining after the measurement. It is advantageous to carry out this sequence of actions 2-3 times.

The solution according to the invention allows for faster washing of the microcapillary plate and, more importantly, more effective removal of elements from the previous sample from the plate, thus reducing the so-called memory effects.

Both methods of washing the microcapillary nebulizer can be used alternately, or only one of them can be used. By using one of the washing methods or alternating both washing methods, in each case a significant improvement in the time and accuracy of washing the nebulizer is obtained.

The subject matter of the invention is shown in an embodiment in the drawings, in which Fig. 1 shows a schematic view of a nebulizer with a solenoid valve, and Fig. 2 shows a nebulizer with an additional washing solution pump.

In the solution according to the invention, the nebulizer, in which the microcapillary plate 4 with capillaries 7 is placed, is provided with a fog chamber 11, preferably a cyclone. The analyte from the vessel 2 or the washing solution from the vessel 3 is supplied to the microcapillary plate 4 via a tube 1 by means of a peristaltic pump. The fog chamber 11 is equipped with a drain 8 in the lower part and an outlet 9 from the top, through which the aerosol is directed to the burner of the spectrometer. The working gas 5 is directed onto the microcapillary plate 4 in relation to the analyte through the solenoid valve 6.

In a variant of the invention, the nebulizer is equipped with an additional pump 12 for delivering the washing solution to the microcapillary plate 4 from the working gas supply side.

The washing of the microcapillary nebulizer is performed after the measurement has been carried out, so that the tubing 1, through which the analyte is supplied by the peristaltic pump 10, from the vessel 2 to the microcapillary plate 4, is transferred to the vessel 3 with the washing solution. During this time, as well as during the measurement, the working gas 5 flows through the microcapillary plate 4. After the time necessary for pumping the washing solution into the plate 4, when it is already washed by the washing solution, the supply of working gas 5 is shut off for a few seconds, preferably this is done by a solenoid valve 6 blocked with the nebulizer. After closing the gas supply, the pressure difference on both sides of the microcapillary plate 4 drops to zero and the washing solution flows more easily into the capillaries 7. Then, when the valve 6 is opened again, the working gas flows through the capillaries, which causes ejection of the washing solution from the capillaries 7 together with the impurities 7 remaining in the capillaries during the measurement. It is advantageous to carry out this sequence of actions 2-3 times.

In an embodiment of the invention, the method of washing the microcapillary nebulizer is carried out as follows: after the measurement, the tube 1, through which the analyte is supplied to the nebulizer, is transferred from the vessel 2 to the vessel 3 with the washing solution. During this time, as well as during the measurement, the working gas flows through the microcapillary plate 4. The next step is a short-term, preferably 1-2 seconds, feeding the washing solution from an independent pump 12 to the pressure side of the plate 4, without interrupting the gas flow. During this time, the washing solution enters the capillaries 7 and flows through them, simultaneously washing away the impurities remaining after the measurement.

It is advantageous to carry out this sequence of actions 2-3 times.

In both washing methods during washing (except for the period of closing the flow of working gas in the first method), there is a process of formation of an aerosol of the washing solution (similarly to the measurement of the analyte solution), which after the separation of larger drops in the fog chamber 11 is directed to the burner 9 and the effluent 8 is discharged from the fog chamber through the hydraulic seal.

PL 206 488 B1

Claims (3)

Patent claims 1. The method of washing the microcapillary nebulizer is carried out by changing the pumped analyte into a washing solution, characterized in that, after the measurement, the tube 1, through which the analyte is supplied from the vessel 2 to the nebulizer, is transferred to the vessel 3 with the washing solution, and at that time, as during the measurement, the working gas flows through the microcapillary plate 4, while after the time necessary to pump the washing solution into the plate 4, when it is already washed by the washing solution, the gas supply 5 is closed for a few seconds through the nebulizer line, preferably by means of a blocked with the nebulizer of the solenoid valve 6, during which the pressure difference on both sides of the microcapillary plate 4 drops to zero and the washing solution flows into the capillaries 7, then, after re-opening the valve 6, the gas flow causes the washing solution to be pushed out of the capillaries 7 along with the remaining ones during measurement of 7 impurities in capillaries. 2. The method of washing the microcapillary nebulizer is carried out by changing the pumped analyte into a washing solution, characterized in that, after the measurement, the tube 1, through which the analyte is supplied from the vessel 2 to the nebulizer, is transferred to the vessel 3 with the washing solution, and at that time, as and during the measurement the working gas flows through the microcapillary plate 4, then within a short time, preferably for a period of 1 - 2 s, the washing solution is fed from an independent pump 12 to the pressure side of the plate 4, without interrupting the gas flow, the solution at this time being the washing agent enters the capillaries 7 and flows through them simultaneously washing away the impurities remaining after the measurement. 3. A method of washing a microcapillary nebulizer according to claim 1; 3. The method of claim 1 or 2, characterized in that it is preferable to carry out the sequence of washing operations 2 or 3 times.