US3163699A - Sampling apparatus for flame photometer - Google Patents

Description

Dec. 29, 1964 J. J. J. STAUNTON 3,163,699

SAMPLING APPARATUS FOR FLAME PHOTOMETER Filed April 3, 1961 ATTORNEYS.

ments for on the order of ml.'of sample.

p messes Ice Patented Dec. 29, l fi l This invention relates to apparatus adapted to sample liquids for analysis in a flame photometer.

A flame photometer consists of a burner system producing a high temperature non-luminous flame, a means for introducing into the flame a finely divided aerosol formed from the sample undergoing analysis, and a photometer for measuring the intensity of light given off by the flame as it excites the sample. This intensity measurement can be related to the rate at which the considered constituent of the sample is excited by the flame which rate in turn is a function of the volume of sample entering the flame per second and the concentration of the excited constituent. I

An accurate measurement therefore requires that the sample be introduced into the flame as. an aerosol at a steady, reproducible rate. The most generally used system for forming and introducing the aerosol is atomization of the liquid sample either into the fuel stream to the burner or directly into the flame itself. The sample may either be poured into a receiver from which it passes to the atomizer, or suction from the atomizer may be used to draw the sample from a beaker or sample cup.

Such systems handleone sample at a time. If poured into a reservoir, the sample must be completely exhausted before a subsequent sample maybe handled. If introduced by suction from a sample cup, the removal of the cup terminates introduction and clears the way for the next sample. Both methods, however, limit the speed at which successive or serial samples maybe analyzed. In a laboratory handling hundreds of similar samples an hour, such methods are too slow.

It is an important object ofthe present invention to provide improved sampling apparatus which is capable of presenting samples to the atomizer at as high a rate as the photometer can effect a reliable reading of their content. With one of the faster contemporary flame photometers,

for instance, the normal rate by priorart sample handling of about 30. samples per hour can be increased to 250, an ifiprease of overeight times. I

Another important object is to provide sampling apparatus in which the required volume of'samples is substantially. decreased, and micro-determination may-be performed. For example, the sample volume may be re duced to as little as 0.2 ml., as compared to prior require- An additional object is to provide sampling apparatus which requires no moving mechanical sample handling or locating devices. An accompanying advantage is that samples are not spilled within the apparatus, which is a hazard inthe prior; suction type sampling methods.

A further object is to provide sampling apparatus which is very versatile and adaptable, and may be employed with V discrete samples, serial, samples, .or continuous sample Theapparatus is welladapted for automatic op An additional object is to provide compact, simple,

economical, and reliable sampling apparatus.

I These. and other objects, advantages, and functions of the invention will be apparent from the specification and from the attached drawings illustrating preferred embodh FIGURE 1 is a schematic vertical sectional and eleva tional view of flame photometer apparatus including the sampling apparatus; and I FIGURE 2 is a like view of another embodiment of the flame photometer apparatus.

A preferred embodiment of the sampling apparatus of the invention includes a sample container, inlet means on the container, outlet means on the container, and means for mounting a capillary tube in the container extending from outside the container. In preferred embodiments of the invention, means are provided for removing a sample from the container. Valvemeans preferably are connected to the outlet means. 7

The sampling apparatus is adapted for use in combination with an atomizer for a flame photometer. The atomizer may be adapted, for example, to atomize a liquid sample into the fuel stream to the burner of a flame photometer, or it may be a component of an atomizer burner, wherein the sample is atomized directly into the burner flame. In either case, the atomizer is mounted above the sample container, and a capillary tube extends from the atomizer into the container.

Referring to the drawings, a conventional atomizer burner of a flame photometer is illustrated in FIGURE 1 and indicated by the number lltl. This type of burner is preferred in the invention for steadier operation and efficient sample utilization. FlGURE 2 illustrates another type of conventional burner 12, which is connected to a conventional separate sample atomizer 14. Each burner is supplied with fuel gas, through respective gas conduits 16 and i8, and each is supplied with a stream of air, oxygen or suitable oxidant gas through an oxidant conduit, 20 and 22 respectively.

The liquid sample is introduced into the flame in the form of a finely divided sprayor aerosol. In'the atomizer burner of FIGURE 1, a sample is aspirated through a capillary tube 24, which extends through the orifice 25 in the orifice plate as constituting the upper end of an atomizer tube 28. The suction produced by the flow of oxidant gas entering through the conduit 2rd and passing through the atomizer tube 28 draws a sample on the capillary tube, and the sample is atomized at the orifice plate 26 and dispersedin the flame 30. A photometer,

atomizer 1d. The construction of the spray chamber 36 of the atomizer separates the larger particlesof liquid. The large particles collect andare removed through a .drain conduitiid at the base of the chamber, which conduit includes a seal 4%? to prevent the escape of gas. The fuel gas and the oxidant gas containingflnely divided liquid sample admix in the burner 12 and form a flame 42,.Whichis measured by a photometer. I

In the prior flame photometers, the apparatus so far described was employed together with a sample cup 'Which was inserted at the bottom of the capillary tube 24 or the capillary '32. Suchapparatus was limited to the analysis of discrete samples, which were inserted one at The present invention does away with this a time.

restricted, tedious, and hazardousmanner of operation.

In each illustrative embodiment of the invention, an

inverted T-shapedsample container 44 is provided, which includes a normally vertically arranged tubular neck 46, a normally horizontally arranged tubular inletarm 43, and a normally horizontally arranged tubular outlet'arm 5th. The base 52of the sample container 44 preferably is concave, thereby providing a sump 54 at the junction of the neck and arms. For most versatile use, the sample container 44 has a small internal volume, the inlet arm 48 is restricted adjacent to the sump to provide a a narrow passageway 5'6, and the outlet arm 50 is restricted to provide a narrow passageway 58.

The inlet arm 48 of the container 44 may be connected to or integral with a supply tube or suitable conduit 60, which may have either a larger bore 62 or a similarly restricted bore, as desired. The supply conduit may be filled from a funnel 64, or be connected to another source of discrete, serial, or continuous samples.

The outlet arm 50 is connected to a small bore tube 66 or other suitable conduit, and a valve 68 is connected thereto. The valve is in turn connected to a conduit '79, which leads to a vacuum pump or other suitable sample removing means, not shown, through a waste trap 72 if desired.

The capillary tube 24, or 32, is inserted closely adjacent to the base 52 in the sump 54 of the sample container. Suitable sealing means such as a rubber plug 74 are provided between the neck 46 of the container and the capillary tube, which extends in sealing engagement therethrough. The upper end of the plug 74 receives the atomizer tube 28 tightly, so that the burner 16 provides support for the sample container 44. The small volume sample well and insertion of the capillary tube close to the bottom of the sump 54 thereof render it possible to analyze samples as small as 0.2 ml., which volume is enough to reach a teady indication of the flame photometer.

When analyzing discrete samples, the sample may be poured into the funnel 6 4, and it will run down into the container 44. Suction through the capillary tube 24 assists the sample flow past the constriction at the end of the narrow inlet bore 56 by removing the trapped air. With the outlet valve 63 closed, the sample automatically will be restricted from flowing out into the tube 65 or up into the container neck 46 by air trapped in the respective spaces. In this manner of operation, it is preferred that the outlet arm 56) and the connecting tube 66 have as small an internal volume as possible. Sufiicicnt immersion of the capillary tube 24 results from this construction to eliminate interference with flow rate through the capillary by surface tension of the sample or by vortex formation.

Excess sample may be permitted to stand in the supply conduit 60, up to a head of an 8" column of water in one embodiment without significant el fcct on the emission of the flame, if the solution is being analyzed for alkali metals or the like. This is because the change in flow rate associated with the change in head is compensated by a change in temperature of the flame. When the solution is being analyzed for calcium, for example, the emission drops with increasing head, leveling otf in the particular embodiment illustrated in FIGURE 1 of the drawing, at a head of approximately 20 cm. If greater accuracy is desired in analyzing for such materials, the liquid head may be substantially eliminated by disposing the tube in horizontal position. This provides a latitude in sample size, makes possible extended observations without reading drift, and makes feasible accurate measurement of serial samples.

When the reading has been obtained, it is unnecessary to wait for the sample to be completely atomized. The remainder of the sample may be rejected immediately by opening the valve 68 in the line to the vacuum punt The valve preferably is quick-acting for discrete samples. In case the next sample is different, a rinse may be poured in the funnel 64 and immediately exhausted. T he rinse may be distilled Water or it may comprise a 1% nonionic detergent solution followed by 1% caprylic alcohol in acetone, to maintain cleanliness and wettability for free draining. In the case of samples of like characteristics, the rinse between samples may be unnecessary, inasmuch as the residue remaining in the system from the first sample will be negligible due to the free draining and nontrapping characteristics of the preferred embodiment.

The enlarged bore 62 of the supply tube 60 facilitates the introduction of a sample without trapping an air bubble. On automatic serial runs, it may be advantageous to employ a restricted bore 62, to provide intentional trapping of air bubbles to serve as separators of adjacent samples. An adjustable throttling type valve 68 then preferably is employed, and it may be adjusted to maintain a suitable slow rate of how through the system. As each sample passes the capillary tube 24', a. portion is atomized, and the flame photometer reading reaches an equilibrium value long enough to be noted or recorded. Should a constricted supply tube 60 not be available, portions of water or detergent solution may be interposed between samples for analysis, to separate the samples and clean the apparatus. Alternatively, in the case of samples having distinctivecharacteristics, the separators may be omitted, and readings may be made on the plateau reached by the indicating meter just prior to the change due to the next sample. When analyzing serial samples, it is unnecessary to confine the samples in the sump 54 by means of trapped air as in the case of discrete samples. Consequently, the length of the outlet arm and the size of the conduit 66 connected thereto are not limited.

One of the advantageous features of the invention is its flexibility in handling serial samples. A wide range of sample size may be accommodated while maintaining a maximum rate, by proper selection of the setting of the valve 68.

Even greater speed and convenience may be achieved by using a recorder as an indicating instrument and an automatic sampling device which delivers the samples to the conduit 60. By incorporating a differentiating circuit with suitable time delay on the recorder, it is further possible to automatically determine the time when a steady equilibrium reading has been attained, and forthwith operate the valve 68 to reject the unnecessary remainder of the sample, and, if desired, an intervening rinse, so as to initiate the measurement of the next sample without delay. It will be apparent that further extension of automatic features may be made.

The invention makes possible continuous monitoring of a process through the supply tube 60, connected directly or through a suitable pressure break to the process feed line. Reference or zero samples, or rinsing porttions may be introduced at intervals by appropriate manual or automatic valving. If air bubble separators are desired, they may be injected at intervals or as required or they can be allowed to enter automatically by interrupting sample delivery. The apparatus adapts itself readily to any of these methods of operation, due to its non-trapping, free-draining construction and its insensit6igity to variations in the liquid level in the supply conduit The invention thus provides important improvements in sampling apparatus for flame photometers. It is particularly characterized by rapid and reliable operation, and the utility of flame photometer apparatus is extended to micro-determinations. The invention overcomes prior disadvantages and provides a number of significant advantages over the prior methods and apparatus.

It will be apparent that various changes and modifications may be made in the construction, arrangement, and manner of operation of the preferred embodiments which have been illustrated and described, within the spirit and scope of the invention. It is intended that such changes and modifications be included within the scope of the appended claims.

What ,I claim as new and desire to secure by Letters Patent of the United States is:

1. Sampling apparatus for a flame photometer comprising a container having a vertically arranged neck and a sump below the neck, a capillary tube mounted in said neck for conducting liquid samples from said sump to an vatomizer, a horizontally arranged inlet arm connecting to said container for introducing liquid samples into said sump, a horizontally arranged outlet arm connecting to said container for carrying fluids from said sump, differential pressure fluid-withdrawing means connected to said outlet arm, and valve means mounted in said outlet arm between said container and said fluid-withdrawing means for controlling fluid-flow through said sump.

2. Flame photometer apparatus comprising a container having a vertically arranged neck and a sump below the neck, a capillary tube mounted in said neck for conducting liquid samples from said sump to an atomizer, a horizontally arranged inlet arm connecting to said container for introducing liquid samples into said sump, said inlet arm being restricted near its outlet into said sump, a horizontally arranged outlet arm connecting to said container for carrying fluids from said sump, a vacuum pump connected to said outlet arm for pulling liquid samples past said restriction and through said sump, and valve means mounted in said outlet arm between said container and said pump means for controlling fluid flow through said sump.

3. The photometer of claim 2 in which said outlet arm is restricted.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. SAMPLING APPARATUS FOR A FLAME PHOTOMETER COMPRISING A CONTAINER HAVING A VERTICALLY ARRANGED NECK AND A SUMP BELOW THE NECK, A CAPILLARY TUBE MOUNTED IN SAID NECK FOR CONDUCTING LIQUID SAMPLES FROM SAID SUMP TO AN ATOMIZER, A HORIZONTALLY ARRANGED INLET ARM CONNECTING TO SAID CONTAINER FOR INTRODUCING LIQUID SAMPLES INTO SAID SUMP, A HORIZONTALLY ARRANGED OUTLET ARM CONNECTING TO SAID CONTAINER FOR CARRYING FLUIDS FROM SAID SUMP, DIFFERENTIAL PRESSURE FLUID-WITHDRAWING MEANS CONNECTED TO SAID OUTLET ARM, AND VALVE MEANS MOUNTED IN SAID OUTLET ARM

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