US3438711A

US3438711A - Burner system with heated spray chamber for spectroscopic analysis

Info

Publication number: US3438711A
Application number: US339218A
Authority: US
Inventors: August Hell
Original assignee: Beckman Instruments Inc
Current assignee: Beckman Coulter Inc
Priority date: 1964-01-21
Filing date: 1964-01-21
Publication date: 1969-04-15
Anticipated expiration: 1986-04-15
Also published as: GB1093523A; DE1598031B2; DE1598031A1; GB1093522A

Description

Apnl 15, 1969 A. HELL. 3,438,711

BURNER SYSTEM WITH HEATED SPRAY CHAMBER FOR SPECTROSCOPIC ANALYSIS Filed Jan. 21, 1964 Sheet of z mvrsmon AUGUST HELL ATTORNEY Aprll 15, 1969 A. HELL 3,438,711

BURNER SYSTEM WITH HEATED SPRAY CHAMBER FOR SPECTROSCOPIC ANALYSIS Filed Jan. 21, 1964 Sheet 2 of s INVENTOR AUGUST HELL FIG. 4 B.Y/7 W;(

ATTORNEY Aprll 15, 1969 A. HELL 3,438,711

BURNER SYSTEM WITH HEATED SPRAY CHAMBER FOR SPECTROSCOPIC ANALYSIS Filed Jan. 21, 1964 Sheet 3 of 3 FIG. 5

INVENTOR.

' AUGUST HELL ATTORNEY United States Patent Oflice 3,438,711 Patented Apr. 15, 1969 3,438,711 BURNER SYSTEM WITH HEATED SPRAY CHAM- BER FOR SPECTROSCOPIC ANALYSIS August Hell, Whittier, Calif., assignor to Beckman Instruments, Inc., a corporation of California Filed Jan. 21, 1964, Ser. No. 339,218 Int. Cl. G01n 21/00; G013 3/00; B05b 1/14 US. Cl. 356-36 22 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for obtaining a larger concentration of atomic vapor greater than that heretofore obtainable particularly for use in atomic absorption spectroscopic analysis are disclosed. The method includes the steps of spraying a sample dissolved in a solvent into a heated chamber where the solvent is evaporated, delivering the vaporized solvent and the sample to a condensing chamber for condensing the solvent, mixing the remaining solvent and sample with a fuel and igniting the result ing mixture. Apparatus is disclosed for carrying out the method which consists of a heated spray chamber and an atomizer for spraying a solution of solvent and sample into the chamber and a condensing chamber in fluid communication with the heated spray chamber. The condenser is connected to a suitable burner, preferably a laminar flow burner.

A burner head, particularly adapted for use with fuel-s of high burning velocity is also disclosed, which generally comprises a head member with an elongated slot therein and removable strips and spacers such that a plurality of narrow slits, the width of which may be varied, are provided.

This invention relates to a burner system for spectroscopic analysis and, in particular, to a burner system which is most advantageously used for atomic absorption analysis.

Generally in spectroscopic analysis the sample is fed into the flame of a burner in the form of a fine mist. If the mist is generated in a conventional atomizer burner by aspirating the sample with one of the flame gases at the bottom of the flame, a large gas stream velocity is required. Therefore, only fuel gases with high burning velocities such as acetylene or hydrogen can be used with the conventional atomizer burner. Also, because of its shape, the flame of the atomizer burner provides only a short absorption path for the crossing light beam of a monochromator. Furthermore, increasing the sample spray rate and hence the atom population of the analyte (the substance being analyzed) in the flame to enhance analytic sensitivity causes a sharp drop in flame temperature and the flame becomes more noisy and less transparent due to incomplete evaporation of the sample. Yet, for some elements the high flame temperatures which can be obtained with the combustion gases used in the atomizer burners are mandatory.

Therefore, the burners more widely used in atomic absorption analysis utilize combustion gas mixtures with relatively small burning velocities and flame temperatures, such as coal gas, propane, or acetylene-air mixtures. These flames are acoustically quiet, have a laminar gas flow pattern and can be maintained in a lengthy, extended form, thus forming a long absorption path for the light beam. Hereinafter, such burners will be referred to as laminar flow burners. However, unlike the atomizer burner, direct atomization of a sample is not feasible for the slow burning flame of a laminar flow burner. Therefore, separate spray chambers have been used in the past in connection with the burner. The sample is atomized and sprayed into the spray chamber and is premixed with the combustion gases for the burner and then delivered into the burner. This in an inefiicient method since a large percentage of the sample globules generated by the atomizer hits the walls of the spray chamber and the larger drops settle out on the way to the burner-head. Moreover, the gas stream can only carry a moderate mist concentration. Deliberate overloading of the gas stream with mist causes only a high recombination rate of smaller sample globules to larger drops. Hence, the sample loss to the walls of the spray chamber increases rapidly with the overload of sample and makes the method more and more inefficient. Also, the flame itself can only evaporate a certain amount of sample completely. If it is overloaded with mist, it can cool down so far that the chemical compounds of the sample are no longer broken down efiiciently. Beyond a certain limit, the flame will die out or become intolerably nontransparent due to light scattering at the non-evaporated water drops.

It is, therefore, the principal object of the present invention to overcome the above disadvantages by providiug a burner system which increases the sample vapor in the flame of a burner without overloading the flame with solvent mist or vapor.

It is a further object of the invention to provide a burner system for atomic absorption or the like which provides uniformity and fineness of sample fed to the flame and much higher sensitivity and stability over conventional burners.

A further object of the invention is to provide a burner for atomic absorption analysis which eliminates flashback, provides a stable, wide flame and is highly versatile.

According to the principal aspect of the present invention, a large concentration of atomic vapor greater than that heretofore obtainable is made available in a flame for spectroscopic analysis. The sample dissolved in a solvent is first atomized and sprayed into a heated spray chamber. The solvent in the spray is evaporated in the spray chamber to transform the sample mist into the form of an aerosol, which is understood to mean a cloud of small solid particles of clustered analyte molecules. Thereafter, the vaporized solvent and sample aerosol are delivered to a condensing chamber in which most of the solvent is condensed on the walls of the chamber thereby leaving only a fraction of the solvent and the aerosol in the chamber which is delivered to a burner to be mixed with the flame-gases of the burner. By this method, a high concentration of sample in the flame of a burner is provided without overloading the flame with solvent mist or vapor and, therefore, the sensitivity of the burner is greatly increased.

According to a secondary aspect of the present invention, there is provided a burner which is particularly advantageous for atomic absorption analysis. The burner has a chamber therein which converges to a narrow elongated slot at the upper end of the burner. Rather than having merely a single slot at the outlet end of the burner, there is provided an elongated strip positioned lengthwise in the slot to divide the slot into two narrow slits. This arrangement permits a wider flame to be delivered from the burner and prevents flashback in the burner. A further feature of the improved burner is a means for changing the width of the slits at the tip of the burner so that different types of gases may be used in the burner.

Other objects, aspects and advantages will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a partial longitudinal sectional view through the burner system of the present invention;

FIG. 2 is a perspective view of the burner of the present invention with the shield around the burner partly broken away;

FIG. 3 is a longitudinal sectional view through the novel burner of the invention;

FIG. 4 is a fragmentary view of the shoulder plate on the top of the body of the burner; and

FIG. 5 is a partial longitudinal section through a modified form of the burner system of the present invention.

Referring now to the drawings in detail, the principal components of the novel invention are a housing 10, an atomizer sprayer 12, heating means 14, a chamber 15, a condenser 16 and a burner 18. In accordance with the method of the invention, a sample is first dissolved in a suitable solvent and is atomized and sprayed through the sprayer 12 into the chamber 15 preferably by means of the oxidant which is used in the burner 18. The sample spray or mist is heated in chamber 15 to completely evaporate the solvent and to transform the sample into an aerosol. Then the oxidant-evaporated solvent-aerosol mixture passes from the chamber 15 into the condenser 16 where the major portion of the evaporated solvent vapor condenses on the walls of the condenser and the remainder of the solvent (approximately becomes again the form of a mist which is microscopicaly fine and very uniform. The formation of a mist will mainly occur around the sample particles of the aerosol. A small percentage of the sample particles hitting the walls of the condenser will be lost for the analysis. However, a much greater percentage of the solvent vapor than of the aerosol is condensed out from the mixture entering the condenser. Therefore, as to the gases which are delivered to the burner and maintained in the flame, the ratio between the solvent and the sample is increased many-fold over that obtainable by conventional burner systems which results in significant improvements in sensitivity.

Although any suitable design of the various parts described above may be utilized, two preferred embodiments of the invention are disclosed herein for purposes of illustration.

Referring now to FIG. 1 in detail, the chamber is preferably cylindrical in shape and is concentrically positioned with respect to the cylindrical condenser 16. Both the chamber and condenser 15 and 16 are disposed at an angle with respect to a horizontal plane for the reason as will appear later. At the upper end of the housing 10 there is provided a central opening 20 which receives a circular plate 22 which closes the opening. The plate 22 has a central opening 24 in which there is mounted the tip of the sprayer 12 fixed to the housing 10 by bracket 13. A duct 27 connects the inlet of the sprayer to a pressurized source of oxidant (not shown) used for the burner which may be either oxygen or air, and duct 26 delivers a sample disolved in a suitable solvent to the sprayer. It is important that the sprayer 12 has high stability since the stability of the whole burner system depends greatly upon the sprayer. Any drift in the spray rate will show up in a change in the signal of the spectrophotometer (not shown) used in connection with this system. The sprayer must, therefore, be of high quality. It has been found to be advantageous to provide a plurality of openings 28 in the plate 22 which surround the sprayer tip 12 so that some air is sucked into the chamber 15 under general operating conditions. The passage of air through the openings 28 tends to smooth out the pressure fluctuations, if any, of the burner especially at the onset of the feed of the sample-solvent mixture into the chamber. Without these openings, it is possible that the flame may be blown out when spraying is started.

Once the sample spray or mist is in the chamber, the chamber must be heated sufliciently to completely evaporate the solvent in the spray. A conduction type heating chamber may be used, as has been used occasionally in the art, however, such a chamber has the disadvantage that the cooling of the walls causes drifting, especially at continued high spray rates of sample into the chamber. Thus, in accordance with the present invention, it has been found most advantageous to overcome the problem of drifting by utilizing infrared heating to evaporate the solvent which is sprayed into the chamber 15. Infrared heating has the advantage that the fine sample drops evaporate before they have the opportunity to hit the walls of the chamber and thus are lost for analysis. The infrared heating chamber 15 is shown in FIG. 1 as bounded or defined by a central cylindrical wall 30 of near infrared transmitting, glass, the plate 22, and a portion of the end plate 64. Fused silica or preferably Pyrex may be used for the glass cylindrical wall 30. The cylindrical glass wall 30' is positioned within a central opening 32 in a boss 33 in the end plate 34 of the condenser 16 and the upper end of the glass wall bears upon an annular shoulder 36 on the cap 22. A pair of

annular plates

38 and 40 surround the glass Wall 30 and a cylindrical reflector 42 is connected by any suitable means to the two

plates

38 and 40*. A heating wire 44 is wound in the annular space between the reflector 42 and cylindrical glass wall 30 and has a pair of leads 46, only one being shown, which extends outside the housing 10 for connection to a suitable power source. Preferably, the heating wire 44 consists of NiCr which is wound in the form of a small, long spiral and connected in a zig-zag manner to the

opposite plates

38 and 40 by hooks 47. The use of the infrared heating system is important because the heat transfer does not only occur along the heated wall, but within the total volume of the chamber. Furthermore, because the temperature of the heater 14 is appreciably higher than the temperature which would be feasible for a chamber with walls heated by thermal conduction, the spectral energy distribution of the radiation in the novel chamber is more favorable for the evaporation of the solvent in the spray than that obtainable in a conduction heated chamber.

As mentioned before, heated spray chambers are old in the art for use with burners for spectroscopy. However, the problem with the conventional spray chamber and burner combination is that the flame of the burner can handle only a certain amount of water vapor or solvent. A large amount of vapor in the hot combustion gases of the burner increases the streaming velocity at the burner tip markedly while at the same time diluting the combustion gases and reducing the burning velocity. Therefore, the flame is lifted off from the burner tip and extinguished. Thus, the problem which must be solved is to remove most of the water vapor from the gas stream while retaining the sample aerosol in the burner gases. This is performed in the present invention by means of a condenser 16. The condenser may have any suitable configuration and is shown in FIG. 1 as comprising a cylindrical housing 48 which is attached to the housing 10 by welding 50 or the like at the joint of the two housings. A cooling coil 52 in the form of a hollow tube is wound about the housing 48 of the condenser and also extends around the housing 10 to reduce undesired outside radiation from the heater. The coil 52 is connected to any suitable supply of water or cooling liquid, not shown. Within the cylindrical housing 48, there is positioned a second cylindrical member 54 which has a plurality of ring shaped cooling plates 56 connected thereto. Positioned within the cylinder 54 is a second cylinder 58 also having a plurality of ring shaped cooling plates 60 positioned between the plates 56 thereby providing a bellow-shaped path for fluid flow through the condenser. End plates 62 and 64 are positioned at the opposite ends of the cylinder 54 and each is provided with openings 66 and 68, respectively, for permitting the flow of gas therethrough. An end plate 70 closes the open end 72 of the condenser 16 and is integral with the end of the cylinder 58. The end plate has an opening 7-3 therein for receiving a central duct 76 and an opening 78 which permit the flow of cooling liquid through the central cylinder 58. Thus, there is provided by this condenser an arrangement whereby the gases passing from the spray chamber 15 have a long path to slide along the cool surfaces of the condenser to remove the solvent from the gas.

Due to the difference in the diffusion rate between the Water molecules in the gas phase and the particles of the aerosol, which can be considered as huge molecules, the concentration of water vapor decreases more than the concentration of the analyte particles while the vapor-aerosol mixture is sliding along the cooled walls of the condenser. It should be noted that the spacing between the cooling plates 56 and 60 should be large enough to avoid a partial obstruction of the gas path by drops formed from condensed solvent,

A small outlet 80 is provided at the lower end of the condenser 16 so that condensed solvent may run down the inclined condenser and drain out through the opening 80. From there, the liquid may be drained to waste.

After the major portion of the solvent is condensed in the condensing chamber 16, the sample aerosol and a very small portion of the remaining solvent passes through the openings 66 in the end plate 62 and pass out an outlet 74 at the end of the condenser. The outlet 74 has an opening 75 which receives a fuel line 77 for delivering fuel to the burner 18. The outlet duct 74 is connected by a sleeve 81 to the burner inlet 82. The duct 74 and inlet 82 must be of suflicient length to permit a complete mixing of the aerosol-oxidant mixture and the fuel from the fuel line 77 before reaching the burner 18. The burner is shown as surrounded by a chimney 84 having a window 86 therein through which the light beam of a monochromator (not shown) extends.

The preferred burner to be used with the chamber 15 and condenser 16 of the invention is shown in detail in FIGS. 2 to 4. The burner includes a body portion 88 which is somewhat wider than the inlet 82 and is tapered towards its upper end as seen in FIG. 3 and is provided with a chamber 90 which converges towards the upper portion of the burner. A shoulder plate 92 having an elongated narrow slot 94 is integral with the upper portion of the body 88 of the burner and the slot 94 is aligned with the chamber 90. The shoulder plate may be cooled by means of a cooling coil, not shown, which surrounds the body of the burner 88 just below the shoulder plate, The body 88 includes a novel burner head 96 which is seated on the upper flat surface of the shoulder plate 92.

The burner head consists of two symmetric-

a1 pieces

98 and 100 which have recessed, flat,

parallel walls

102 and 104 and tapered

outer walls

103 and 105. When the two

pieces

98 and 100 of the head are fastened together by screws 6 and 108, a narrow slot 110 is provided between the

walls

102 and 104 which is aligned with the slot 94 in the shoulder plate 92. While the main portion of the burner may be made of aluminum, it is preferable that the head be made out of stainless steel to reduce unwanted changes in the dimensions of the slot 110 during operation. Positioned between the two pieces of the

head

98 and 100 is an elongated metal strip 111, preferably of stainless steel, which is the same height as the head 96 and extends for the full length thereof thereby dividing the slot 110 into a pair of

narrow slits

112 and 114. The head 96 is afiixed to the shoulder plate 92 of the burner by means of suitable spring clips 116 and 118 so that the head may be readily removed from the burner. An important feature of this burner head is that it may be removed from the burner body and the

screws

106 and 108 removed so that metal strips 111 of different thickness may be disposed between the two pieces 98 and of the burner head and, also,

spacers

117 and 119 may be positioned on either side and at both ends of the strip 111. By adding these spacers or additional spacers and changing the thickness of the strip 111, both the over-all width of the slot 110 and the width of the

slits

112 and 114 of the head may be increased as desired which makes the burner extremely versatile for use with different types of fuel. If the slot of the burner head has a fixed dimension, only one fuel may be used with a given combustion gas volue. By increasing the thickness of the strip 111 the width of the flame produced by the burner is increased which permits a wide optical beam to be used and thus a greater photometric sensitivity and a better signal to noise ratio is achieved. Preferably, the metal strip 111 is tightly clamped at one end between the

side pieces

98 and 100 and the other end is kept loose enough to allow independent thermal expansion. Hence, thermal tensions are prevented from being generated between the burner head and the rest of the burner and, thereby, slot distortions which occasionally occur in one piece burner assemblies are prevented. The strip 111 serves the additional important function of preventing flash-back into the burner While still permitting a relatively wide double slot 110 for the flame. Without the elongated strip, the over-all width of the slot 110 would have to be about the same size as the width of either of the

slits

112 or 114 to prevent flash-back.

A further important feature of the burner is the provision of the chimney 84 which is fitted on the burner by sliding the chimney over the burner with the slots in the chimney registering with the tabs 122 on the sides of the body of the burner. The chimney not only provides a means for protecting the flame from side drafts and thus provides stabilization of the flame, but also adds to the shaping of the flame cross-section. Whether the flame is wide or narrow depends upon the stream of air at the burner head. The flame stability may be optimized if the air stream which supplies a portion of the oxygen for combustion of the fuel is fed to the flame from below, at a slight angle. The air flow should be smooth and steady. This is achieved by having the chimney extend far below the burner head and having it spaced from the walls of the burner so that cold air is sucked in from underneath the burner and slides up in laminar flow between the flat burner walls and the chimney thus cooling both the burner and the chimney. As best seen in FIG. 3, the sides of the shoulder plate 92 of the burner are close to the chimney, thereby providing a restriction for the air stream. Due to this restriction and the streamlined profile of the burner head 96 provided by the tapered

walls

103 and 105, the air slides along the tapered walls of the tapered burner head 96 and strikes the flame under a slight angle from underneath. The delivery of air to the flame in this manner greatly enhances the stability of the flame. By the novel head of this burner and the chimney surrounding the burner, a burner is provided which has greatly improved stability, versatility, is free from flash-backs, and may have an adjustable burner slot to accommodate different fuels.

The table below shows the concentration of several samples in ppm. which provides one percent absorption when a light beam from a monochromator passes through a flame containing the sam le.

Sample concentration (p.p.m.) which provides 1% absorption The concentrations listed in column A were determined by using a burner as shown in FIGS. 24 which received the samples from a spray chamber and condenser apparatus as shown in FIG. 1. In column B, the sample concen tration for each sample listed is obtained from data appearing in Performance of a Simple Atomic Absorption Spectrophotometer by B. M. Gatehouse and I. B. Willis in Spectrochemia Acta, 1961, vol. 17, pp. 710-718, in which a conventional laminar flow burner system was used. By comparing the concentrations listed in columns A and B it can be readily seen that the system of the present invention required much less concentration of sample for the same amount of absorption of the light beam than required in the conventional system. In other words, the system described herein has much greater sensitivity than the conventional system. It is to be noted that the sensitivity of the burner system of this invention would be the same as listed in the table above even if a conventional burner were used rather than that shown in FIGS. 24 because the burner provides stability in the flame and versatility but not sensitivity.

In FIG. 5 there is shown a slightly modified form of the burner system of the present invention. The heating chamber and sprayer 12 are the same as is shown in FIG. 1 whereas the condenser 16 differs only in certain details as will be described below. The important feature of this embodiment of the invention is that a low profile burner 124 is provided so that a conventional monochromator may be used with the burner system that need not be mounted in a high position so that the light beam will coincide with the window in the chimney 84 surrounding the burner. The low profile is provided by removing the inlet duct 82 of the burner and replacing it with a duct 126 which extends centrally into the condenser 16, in which duct the mixing of oxidant, fuel and sample takes place prior to the delivery thereof to the burner. The body 88 and head 96 of the burner 124 are essentially the same as that shown in FIGS. 2 to 4 and the burner is preferably surrounded by a chimney, not shown.

The condenser in FIG. 5 comprises an outer cylinder 127 in which there is mounted a pair of

perforated end plates

128 and 130. These plates are connected to an inner cylinder 132 which surrounds the tube 126. Cooling ducts 134 surround the cylinder 127 and additional cooling ducts 136 surround the cylinder 132. Hence, vapor and aerosol from the chamber 10 passing through the perforated plate 128 flow along the cool surfaces between the walls of the outer cylinder 127 and the inner cylinder 132, through the perforated plate 130 at the other end, and back toward the first end plate 128 to the inlet end 140 of the duct 126. A second tube 138 has at one end an opening into the inlet end 140 of the tube 126 and has its other end extending outwardly from the condenser for connection to the fuel source, not shown, for the burner 12 4. Thus, after the majority of the solvent in the spray is condensed in the condenser 16, the aerosol will mix with the burner fuel in the duct 126 and complete mixture thereof will be obtained by the turbulent flow through the duct by the time the mixture reaches the outlet end 142 of the duct 126. It can be readily seen therefore that a compact, low profile burner system is provided by this arrangement which does not require any special mounting of a monochromator used therewith.

It is to be understood that the burner system of the present invention may be used for other types of spectroscopic analysis other than atomic absorption. For example, the heating chamber 15, sprayer 12 and condenser 16 combination may be used for flame emission spectroscopy with only slight modification, and a conventional type of laminar flow burner may be used other than the burner shown in FIGS. 2 and 4 in the drawings. Even an atomizer burner could be used. In such a case, the spray chamber would have to be made air tight to permit the build up of necessary pressure to deliver the aerosoloxidant mixture to the burner. The burner system can also be used when the spray chamber is not heated. In this case sensitivities similar to that of a conventional burner system are obtained. This means that the analytical range can be changed easily when high sensitivities are not required, yet all the favorable stability features of the system are maintained.

Although several embodiments of the invention have been disclosed herein for purposes of illustration, it will be understood that various changes can be made in the form, details, arrangement and proportions of the various parts in such embodiments without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. In a method for providing a large concentration of atomic vapor in a burner flame for spectroscopic analysis, the steps comprising:

providing a solution comprising a sample dissolved in a solvent;

transforming said solution into a spray;

heating said spray to evaporate said solvent and to transform the sample into an aerosol;

condensing the evaporated solvent; and

delivering the aerosol to a burner for spectroscopic analysis.

2. In a method for providing a large concentration of atomic vapor in a burner flame for spectroscopic analysis, the steps comprising:

dissolving a sample in a solvent to provide a solution;

transforming said solution into a spray;

heating said spray to a sufficient temperature to evaporate said solvent and to transform the sample into an aerosol;

condensing the evaporated solvent; and delivering the aerosol to a burner for spectroscopic analysis.

3. A method as set forth in claim 2 wherein the heating of said spray is performed with infrared energy.

4. A method as set forth in claim 2 wherein said spray is heated to a sufficient temperature to completely evaporate said solvent.

5. A method as set forth in claim 2 wherein said solution is transformed into a spray by a pressurized burner oxidant.

6. In a method for providing a large concentration of atomic vapor in a burner flame for spectroscopic analysis, the steps comprising:

dissolving a sample in a solvent to provide a solution;

spraying said solution by a pressurized burner oxidant into a chamber;

heating the sprayed solution in said chamber to evaporate said solvent and to transform the sample into an aerosol; delivering the evaporated solvent and aerosol to a condenser;

heating said spray to a sufficient temperature to coinpletely evaporate said solvent and to transform the sample into an aerosol; and

condensing the major portion of the evaporated solvent on a surface other than the aerosol whereby a large concentration of sample aerosol is provided.

8. In a method for providing a large concentration of atomic vapor in a burner flame for atomic absorption or flame emission spectroscopic analysis, the steps comprising:

dissolving a sample in a solvent to provide a solution;

spraying said solution by a pressurized burner oxidant into a chamber;

heating the sprayed solution by infrared energy to a suflicient temperature to completely evaporate said solvent and to transform the sample into an aerosol;

delivering the evaporated solvent and aerosol to a condenser;

condensing the major portion of the evaporated solvent onto the Walls of said condenser;

mixing the aerosol, the remainder of said evaporated solvent and burner oxidant with a burner fuel; and burning said mixture in a burner for spectroscopic analysis.

9. In an apparatus for providing a large concentration of sample aerosol for delivery to a burner for spectroscopic analysis, the combination of:

a chamber;

means opening into said chamber for spraying a solution of sample dissolved in a solvent into said chamber;

means for heating the spray to suflicient temperature to evaporate the solvent into a vapor and to transform the sample into an aerosol;

vapor condensing means in fluid communication with said chamber for condensing the major portion of .the vapor onto the walls of the condensing means;

and

said vapor condensing means having an outlet for connection to a burner. 10. An apparatus as set forth in claim 9 wherein said heating means produces infrared energy.

11. An apparatus as set forth in claim 9 wherein said outlet comprises a tube having an inner end extending into said condensing means and said condensing means including a duct having one end opening into said inner end of said tube and the other end extending outside of said condensing means for connection to a burner fuel supply.

12. An apparatus as set forth in claim 9 wherein said chamber includes a Wall of infrared transmitting material and said heating means comprises a reflector positioned adjacent said wall and a heating wire positioned between said reflector and said wall of transmitting material.

13. In an apparatus for providing a large concentration of sample aerosol for delivery to a burner for spectroscopic analysis, the combination of: a chamber having a Wall portion; means in said wall portion for spraying a solution of sample dissolved in a solvent into said chamber;

said wall portion having a plurality of openings surrounding said spraying means to compensate for pressure fluctuations caused by said spraying means;

means extending about said chamber for generating infrared energy of sufficient amount to evaporate the solvent into a vapor and to transform the sample into an aerosol;

vapor condensing means in fluid communication with said chamber, said vapor condensing means for condensing the major portion of the vapor onto said vapor condensing means; and

said vapor condensing means having an outlet for connection to a burner.

14. In a burner system for spectroscopic analysis, the combination of:

a chamber;

means for spraying a solution into said chamber;

heating means for heating said chamber;

vapor condensing means in fluid communication with said chamber; and

a burner having an inlet connected to said condensing means.

15. A burner system as set forth in claim 14 wherein said heating means produces infrared energy.

16. A burner system as set forth in claim 14 wherein said burner is substantially vertically disposed and said condensing means has an opening at the lower end thereof adjacent to said burner and said condensing means is tilted at an angle with respect to a horizontal plane whereby condensed vapor may escape from said condensing means.

17. In a burner system for spectroscopic analysis, the combination of:

a chamber having a wall portion;

means in said wall portion for sprayinga solution into said chamber;

said wall portion having a plurality of openings surrounding said spraying means;

heating means for heating said chamber;

vapor condensing means in fluid communication with said chamber; and

a burner having an inlet connected to said condensing means.

18. In a burner system for spectroscopic analysis, the

combination of:

a chamber;

means for spraying a solution of sample dissolved in solvent into said chamber;

heating means for evaporating said solvent into a vapor and for transforming the sample into an aerosol;

vapor condensing means in fluid communication with said chamber, said condensing means having an outlet tube with one end extending into said condensing means and the other end outside said condensing means;

a duct having one end opening into said one end of said outlet tube and the other end extending outside of said condensing means for connection to a burner fuel supply whereby the aerosol and fuel are mixed in said tube; and

a burner connected to said outlet tube.

19. A burner system as set forth in claim 18 wherein said burner is substantially vertically disposed and said condensing means has an opening at the lower end thereof adjacent to said burner and said condensing means is tilted at an angle with respect to a horizontal plane whereby condensed vapor may escape from said condensing means; and

the upper end of said burner being below the upper end of said chamber and condensing means.

20. In a burner system for spectroscopic analysis, the

combination of:

a chamber;

means for spraying a solution into said chamber;

heating means for heating said chamber;

vapor condensing means in fluid communication with said chamber;

a burner having an inlet connected to said condensing means, said burner including an inlet for a burner fuel;

said burner having a body with a chamber therein converging to a narrow elongated slot at the upper end of said body and an elongated strip positioned lengthwise in said slot dividing said slot into two narrow slits.

21. In a burner system as set forth in claim 20 including means for varying the width of said slot.

22. In a burner system for spectroscopic analysis, the combination of:

a chamber;

means for spraying a solution into said chamber;

1 1 l 2 heating means for heating said chamber; 3,163,699 12/1964 Staunton 88--14 vapor condensing means in fluid communication with 1,330,464 11/ 1931 l nt r.

Said chamber; 8 OTHER REFERENCES a burner having an inlet connected to said condensing Meloche. Flame Photometry Analytical Chemistry means; said burner lncluding an inlet for a burner 5 VOL 28, NO 12 December 1956 p 1845 relied On- .fuel; Menzies: A Study of Atomic Absorption Spectrosaid burner terminating in a burner head having a scopy Analytical Chemistry, VOL 32 8, July 1960) plurality of slits therein.

References Cited 10 JEWELL H. PEDERSEN, Primary Examiner. UNITED STATES PATENTS F. L. EVANS, Assistant Examiizen 2,828,532 4/1958 Taylor 158116 X 2,857,801 10/1958 Murray 158111 X 2,959,217 11/1960 Barnes et a1 239-652 239552, 568, 590, 597; 356-87, 187