US3731539A

US3731539A - Apparatus for the collection and analysis of samples

Info

Publication number: US3731539A
Application number: US00138678A
Authority: US
Inventors: K Brittan; J Lovelock
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-04-29
Filing date: 1971-04-29
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08

Abstract

An apparatus for the automatic collection and analysis of fluid samples and particularly for the monitoring of atmospheric pollutants. The apparatus comprises a plurality of traps for the collection of samples and which are in turn exposed for a predetermined time interval to the atmosphere. Thereafter the traps are transferred to an analysis station where pollutant contained in the traps is expelled for analysis into an analytical instrument.

Description

United States Patent [191 Brittan et al.

[ May 8, 1973 [54] APPARATUS FOR THE COLLECTION AND ANALYSIS OF SAMPLES [76] Inventors: Kenneth Walter Brittan, 126 Meadow Lane, Coalsville; James Ephraim Lovelock, Bowerchalke, near Salisbury, both of England 22 Filed: Apr. 29, 1971 21 Appl.No.: 138,678

[52] US. Cl. ..73/421.5 R, 23/255 R, 73/28 [51] Int. Cl. ..G01n 1/22 [58] Field of Search ..73/42l.5 R, 28;

[56] References Cited UNITED STATES PATENTS 2,489,654 11/1949 Main-Smith et al ..73/421 .5 R X 2,333,934 11/1943 Jacobson ..73/42l.5 R X 3,540,261 11/1970 Scoggins ..73/28 FOREIGN PATENTS OR APPLICATIONS Australia ..73/42l.5 R U.S.S.R. ..73/42l.5 R

Primary Examiner-Louis R. Prince Assistant Examiner-Joseph W. Roskos Attorney-Woodhams, Blanchard & Flynn [57] ABSTRACT An apparatus for the automatic collection and analysis of fluid samples and particularly for the monitoring of atmospheric pollutants. The apparatus comprises a plurality of traps for the collection of samples and which are in turn exposed for a pre-determined time interval to the atmosphere. Thereafter the traps are transferred to an analysis station where pollutant contained in the traps is expelled for analysis into an analytical instrument.

6 Claims, 8 Drawing Figures PATENTEB MAY 8 I973 sumlnrz ATM/P [FY APPARATUS FOR THE COLLECTION AND ANALYSIS OF SAMPLES The present invention relates to an apparatus for the collection of fluid samples. The invention is particularly applicable to the collection of samples during pollution studies.

One method of collection is to draw a sample into a bottle or trap by means of a pump or suction. The operation is carried out for a definite period of time whereafter the bottle is closed and labelled before being transported to a laboratory for analysis. The bottle may contain a material which can absorb suspected pollutants in the sample. The method can be used for testing gases e.g., atmospheric pollution and for testing liquids e.g., river pollution.

This known method can become tedious, resulting in operators being prone to error, when a large number of samples are required for a survey. The present invention seeks to provide an apparatus that can sample an environment automatically over a selected period of time and which can thereafter be connected to an analytical instrument, such as a gas chromatograph, for the automatic analysis of collected samples.

Thus according to the present invention an apparatus for the collection of fluid samples comprises a rotatable shaft having fixed for rotation therewith a carrier for a plurality of sample traps, the traps being arranged around the axis of rotation of the carrier, valves at the opposite ends of the carrier and in fluid communication with the traps for conducting samples into and out of the traps, a recording device for recording information peculiar to each trap, and a drive connection for rotating the shaft during analysis of collected samples.

In use in the field for the collection of samples the apparatus is mounted in a housing and the shaft is supported for rotation upon journals. The shaft is rotated by a motor, preferably driven from electric batteries contained in the housing. The shaft is rotated to bring each trap in turn into communication with the environment to be sampled at selected intervals. Thus, for example, in an apparatus having 24 traps, the shaft can be rotated through every hour so that at the end of 24 hours the shaft will have rotated through 360. Conveniently, a pump is provided for drawing samples into the traps.

Upon completion of a sampling operation, the apparatus is transferred to an analysis station at which a drive member engages the drive connection on the shaft to bring each trap successively to a position at which the collected sample is expelled into an analytical instrument. A master program can be provided to control the operation of the apparatus at the analysis station. Sample contained in the traps is expelled, as by heating, into the analytical instrument and the signals generated by the instrument can be recorded on the recording device to provide a record of the contents of each trap.

The invention thus provides an apparatus which can operate unattended in the field during the collection of samples and which when transferred to an analysis station for the analysis of the samples can likewise function in an automatic manner to record the results.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. I is a diagrammatic section through an apparatus as used for collecting samples in the field;

FIG. 2 is a diagrammatic section through the apparatus as used at an analysis station;

FIG. 3 illustrates diagrammatically a valve for controlling the entry and exit of samples into and out of traps;

FIG. 4 illustrates diagrammatically a mounting for traps in a carrier;

FIG. 5 illustrates diagrammatically a heater unit as sociated with the traps; and

FIGS. 6a, 6b and 6c are diagrammatic sections through the valve of FIG. 3 at positions P, Q and R respectively.

A sampling apparatus, illustrated diagrammatically in FIG. 1, is mounted in a housing 10 so as to be readily portable as a unit for location at places where samples are to be collected. The housing 10 is preferably provided with a lid or cover (not shown) so as to provide a weatherproof enclosure for the apparatus.

The apparatus comprises a motor 1, which can be driven from a battery contained within the housing, and which is connected to a drive shaft 5 by a releasable coupling 2. The drive shafi 5 is rotatably supported on trunnions 3 and carries a data recording drum 4, selector valves 6 and 6' one at each end of a carrier 7 for a plurality of traps and a worm gear wheel 8. Each of the

components

4, 6, 6', 7 and 8 is secured to the shaft 5 for rotation therewith. The coupling 2 is such that the shaft carrying the above components can be released from the motor 1 and lifted out of the housing 10.

For the sake of example only, the carrier 7 supports twenty four traps disposed uniformly about the shaft 5 and each trap is exposed by the selector valve 6 adjacent the recording drum 4 to the outside atmosphere which is being surveyed for pollution. The exposure time for each trap is one hour so that the collector system is able to collect samples over a period of 24 hours. The motor 1 is controlled by a clock to rotate the shaft at the desired rate. It will be appreciated that a pump 21 is provided so as to draw samples into the traps. The pump is driven by a motor 20 conveniently from the same power source as the motor 1.

Each trap in the carrier 7 may be formed from a glass tube 22 containing a material which will retain a pollutant, the presence of which is suspected in the, atmosphere to be sampled. The glass tube preferably has reduced, tapered ends which carry plugs of glass wool to retain the pollutant absorber within the tube. A typical absorber is activated charcoal. The glass of the tube is preferably of a heat resistant kind.

The valves 6 and 6' can be a twenty four way sliding valve or a valve of the kind as disclosed in British Pat. application No. l3745/70.

In sampling the opening and closing of consecutive traps overlap i.e., trap 2 will open before closure of trap l; trap 3 will open before closure of trap 2 etc. Upon analysis however, each trap is closed before the opening of a second trap. No overlapping of the opening of traps is permissible. Overlapping is required during sampling to ensure that an event e.g., a sudden burst of atmospheric pollution is captured in the trap systems. If this occurs during overlap two consecutive traps will contain the pollution. If there is no overlap an event could escape detection. In analysis it is necessary to know when the events occurred and therefore each trap is examined separately. The valve 6 positioned between the drum 4 and the carrier 7 and the second valve 6' positioned between the carrier 7 and the worm gear 8 are operated together. In order to achieve overlapping of traps on the one hand and the separate, discrete opening of each trap on the other hand the valves 6 and 6' are constructed as indicated diagrammatically in FIG. 3.

Thus each

valve

6, 6 can comprise an inner cylinder 30 provided with a plurality of axially extending through bores 31 adjacent the periphery thereof. In the case of an apparatus having 24 traps the inner cylinder 30 will be provided with 24 bores 31. Each bore accomodates a resilient conduit 32, such as a silicone rubber conduit, and each axial bore 31 communicates with the periphery of the cylinder through a radial bore 33 containing a sphere 34. The cylinder 30, which is mounted upon the shaft 5, is rotatable within and movable axially relative to an outer cylinder or shell 35.

At position P in FIG. 3 and as shown in FIG. 6a, the shell 35 is provided with a recess 36 which extends circumferentially over two adjacent bores 31. At position R in FIG. 3 and as shown in FIG. 60, the shell 35 is provided with a recess 37 which extends circumferentially over a single bore 31. At intermediate position Q and as shown in FIG. 6b, the shell 35 is not provided with a recess and has a plane inner face.

The operation of the

valve

6, 6 is such that when a sphere 34 is out of alignment with a recess in the inner face of the shell 35, the sphere squeezes closed the resilient conduit 32 accommodated in its associated bore 31. When a bore 33 is brought into alignment with a

recess

36 or 37 the sphere 34 therein is moved radially outwards into the recess by the inherent resilience of the tube which is thereby opened.

As shown in FIG. 3, the

valves

6, 6 include an inlet or outlet manifold 37. Each manifold comprises a chamber having a single inlet or outlet 38 and 24 outlets or inlets 39 each connected to a resilient conduit passing through the bores 31.

At position Q all traps are closed, at position P there is an overlap groove 36 in outer body 35 whereby two adjacent silicone rubber or like resilient tubes 32 are opened together over a portion of their total opening time. At position R there is no overlap and each rubber tube is opened and closed independently of any other tube. To move between positions P, Q, R the shaft or shell 35 is movable axially by means of a lever whilst the shell or shaft respectively is held fixed. Thus for sampling the lever is actuated to move valve into position P, for analysis the valve is moved into position R whilst for transport all valves are closed with the lever in position 0.

The sampling operation is as follows. The commencement of sampling is recorded on the drum 4 by an operator who switches on the pump and motor 1. Thereafter the operation is automatic. As the shaft 5 is rotated the twenty four traps are exposed sequentially at 1 hour intervals and the sampling operation is completed in 24 hours. The apparatus is arranged to switch off automatically after the exposure of the 24 traps. When the carrier is collected, an operator moves the lever to position Q to close all valves for transit to the analysis station.

For analysis of the contents of the traps, the shaft 5 carrying the

components

4, 6, 6, 7 and 8 is removed from the housing and placed upon a second support having trunnions as shown in FIG. 2. Whereas the sampling takes place in the field, analysis is generally carried out in a laboratory. The worm gear 8 now meshes with a screw 9 whose shaft is coupled to a master programmer. The master programmer can comprise input information to control an analytical cycle of a gas chromatograph or other analytical instrument and also input information to control the positioning of the carrier to bring each trap successively into the analysis position.

Still referring to FIG. 2, a sub-frame 11 supports a heater 1 1A for heating each trap in turn as it is brought beneath the heater upon rotation of the shaft 5. A platform 12 having an aperture 12A therein is arranged above the recording drum 4 to support a data producing means 13, for example a printer. The data producing means, which is controlled by signals generated by the analytical instrument (not shown) during analysis of the traps, records its output on the drum 4.

An electric motor 40 rotates the screw 9 one revolution at the end of each analysis. In the case of the present example having 24 traps the ratio between gear wheel 8 and screw 9 is 24:] with the result that each trap is moved through 15 upon a complete revolution of the screw 9.

A second motor 42 rotates a spindle 43 through 1 complete revolution during each analysis. The motor 42 is driven continuously and the spindle 43 carries a plurality of control cams 44, only two of which are illustrated in FIG. 2. One of the cams 44 serves to control the operation of the motor 40 and the remaining cams can be utilized to control the functioning of the analytical instrument.

In operation at the analysis station, the screw 9 is driven to rotate the traps in the carrier 7 successively beneath the heater 1 1A. Upon heating each trap in turn the pollutant which has been trapped therein is released and is drawn into the analytical instrument for analysis by virtue of a pressure differential created by a carrier gas employed to conduct the pollutant into the instrument, for example a gas chromatograph. The valves 6 are now in position R. The signal or signals generated by the analytical instrument is or are recorded on the drum 4 by the data producing means 13. This operation is repeated for each of the traps in the collector system. As mentioned above screw 9 serves to rotate the traps beneath the heater as well as being coupled to the master programmer for the analytical instrument. It is not essential to include a data producing means in the apparatus as the signals generated by the analytical instrument can be noted by an operator and recorded manually on the drum 4.

FIG. 4 illustrates the mounting of the traps. The carrier 7 comprises two

end discs

15, 16, having aligned, radial slots at their peripheries to receive the reduced diameter ends of the traps. The slots are provided with a resilient cushion or support for the traps. The traps are retained in position by retaining clips 45 which are secured to the discs, one adjacent each end of each trap. A conduit 20A is shown in FIG. 4 leading from a trap to valve 6.

Each trap 22 is situated within a heat reflector 18 of a polished metal such as aluminum or stainless steel.

The reflector l8 co-operates with a similar reflector forming part of the heater 11A. The two reflectors together form a reflector assembly having an elliptical section in a plane transverse to the longitudinal axis of a trap. The trap is located at one focus of the elliptical assembly and a heater element 45 is located at the other focus. The heater element 45 is preferably a radiant heater bar extending the length of the trap. FIG. 5 illustrates diagrammatically the arrangement of the reflectors in the heater unit and carrier. During analysis, each trap is brought in turn beneath the heater element. A heating current to heat the element may be determined by the master programmer in order to heat the traps at the required time in the analysis cycle. Radiation heating is preferred due to infra-red radiation penetrating the glass walls of the trap and being quickly absorbed by the material, e.g., activated char coal in the trap. However other modes of heating the traps are possible and the invention is not limited to radiation heating.

Whilst 24- traps have been given in example with reference to the drawings, it will be appreciated that the number of traps can be adjusted to suit particular requirements.

Silicone rubber is but an example of a suitable material for the resilient conduits of the valves 6, 6'. The conduits can each be formed from a composite tube having an outer silicone rubber tube lined with a plastics sheath, such as P.T.F.E. The plastics sheath will be bonded to the bore of the silicone rubber tube.

The apparatus is suitable for use with gases. For example, the apparatus can be used in air pollution studies in which a tracer gas is released into the atmosphere and recorded by arrays of sampling traps at different location.

We claim:

1. Apparatus for collecting fluid samples in the field and for presenting the collected samples at an analysis station comprising a rotatable shaft, a carrier secured for rotation with the shaft, a plurality of sample traps supported by the carrier, a pair of valve assemblies mounted on the shaft one at each end of the carrier, each valve assembly comprising a plurality of valve members operable to open and close upon rotation of the shaft and with one member of each assembly connected to and associated with one only of the traps whereby each trap is opened and closed in succession upon rotation of the shaft, means for drawing samples into the traps and first drive means for rotating the shaft at the field station, second drive means for rotating the shaft and means for expelling the collected samples from the traps at the analysis station.

2. An apparatus as claimed in claim 1 in which the fust drive means comprises a motor controlled by a clock and connected to the shaft by a releasable coupling.

3. An apparatus for the collection and analysis of fluid samples comprising a rotatable shaft, a carrier for a plurality of sample traps fixed for rotation with said shaft, a pair of valve assemblies mounted on the shaft one at each end of the carrier for controlling flow of samples into and out of the opposite ends of the traps, a first drive connection for rotating the shaft during collection of samples, and a second drive connection for rotating the shaft during analysis of collected samples the second drive connection comprising a gear w eel on the shaft engageable with an intermittently driven worm gear, the drive to said worm gear being controlled by a programmer whereby each trap in turn is moved through a sample release station.

41. An apparatus as claimed in claim 3 in which the sample release station includes a heater disposed adjacent the carrier.

5. An apparatus as claimed in claim 4 in which each trap is situated within a heat reflector, each heat reflector co-operating in turn with a heater reflector about the heater to form an elliptical assembly in a plane transvere to the longitudinal axis of a trap, each trap being located at one focus of the elliptical assembly and the heater being located at the other focus of the assembly.

6. An apparatus for the collection and analysis of fluid samples comprising a rotatable shaft, a carrier for a plurality of sample traps fixed for rotation with said shaft, a pair of valve assemblies mounted on the shaft one at each end of the carrier for controlling flow of samples into and out of the opposite ends of the traps, a first drive connection for rotating the shaft during collection of samples, and a second drive connection for rotating the shaft during analysis of collected samples, each valve assembly including a manifold and inner and outer valve members, the inner valve member having a plurality of axially extending bores each accommodating a resilient conduit connected to the manifold, a radial bore extending from each axially extending bore to the periphery of the inner valve member and accommodating a valve closure member, the inner valve member being rotatable within the outer valve member and axially movable relative to the outer valve member and recesses in the outer valve member to receive the valve closure member at selected angular positions of the inner valve member whereby to enable the resilient conduits to expand to permit sample flow therethrough.

Claims

2. An apparatus as claimed in claim 1 in which the first drive means comprises a motor controlled by a clock and connected to the shaft by a releasable coupling.

3. An apparatus for the collection and analysis of fluid samples comprising a rotatable shaft, a carrier for a plurality of sample traps fixed for rotation with said shaft, a pair of valve assemblies mounted on the shaft one at each end of the carrier for controlling flow of samples into and out of the opposite ends of the traps, a first drive connection for rotating the shaft during collection of samples, and a second drive connection for rotating the shaft during analysis of collected samples, the second drive connection comprising a gear wheel on the shaft engageable with an intermittently driven worm gear, the drive to said worm gear being controlled by a programmer whereby each trap in turn is moved through a sample release station.

4. An apparatus as claimed in claim 3 in which the sample release station includes a heater disposed adjacent the carrier.