AU623851B2

AU623851B2 - Improved automatic atomic absorption spectrometer

Info

Publication number: AU623851B2
Application number: AU13963/88A
Authority: AU
Inventors: Al E. Bernhard; Theodore James Scuitto; Thomas John Scuitto
Original assignee: Leeman LLC
Current assignee: Leeman LLC
Priority date: 1987-02-17
Filing date: 1988-02-12
Publication date: 1992-05-28
Anticipated expiration: 2008-02-12
Also published as: WO1988006280A1; JPH02502402A; EP0346387A4; AU1396388A; EP0346387A1

Description

AU-AI-13963/88

PCT

WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau 0 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATFNT COOPERATION TREATY (PCT) (51) International Patent Classification 4 G01J 3/42 (11) InternatiM oblicati umb WO 88/ 06280 p. International, Publication ate 25 August 1988 (25.08.88) f J t a 1 (21) International Application Number: PCT/US88/00455 (22) International Filing Date: 12 February 1988 (12.02.88) (31) Priority Application Number: 014,873 (32) Priority Date: (33) Priority Country: 17 February 1987 (17.02.87) (71)72) Applicants and Inventors: SCUITTO, Thomas, John [US/US]; 704 Foss Road, Talent, OR 97540 (US).

SCUITTO, Theodore, James [US/US]; 1508 Southwest Jordan, Grants Pass, OR 97426 BERNH- ARD, Al, E. [US/US]; Beach Street at Highway 1, Brookings, OR 97415 (US).

(74) Agents: LIPPMAN, Peter, I. et al.; Ashen, Golant, Martin Seldon, 10920 Wilshire Boulevard, Suite 1000, Los Angeles, CA 90024 (US).

(81) Designated States: AT, AT (European patent), AU, BB, BE (European patent), BG, BR, CH, CH (European patent), DE, DE (European patent), DK, Fl, FR (European patent), GB, GB (European patent), HU, IT (European patent), JP, KP, KR, LK, LU, LU (European patent), MC, MG, MW, NL, NL (European patent), NO, RO, SD, SE, SE (European patent), SU.

Published With international search report.

Before the expiration of the time limit for amending the claims and to be republished in the event of the receipt of amendments.

A.O.J.P, 13 OCT 1988

AUSTRALIAN

1 4 SEP 1988 PATENT OFFICE (54) Title: IMPROVED AUTOMATIC ATOMIC-ABSORPTION SPECTROMETER BH A

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i:i 1 (57) Abstract An atomic absorption spectrometer in which each sample is analyzed for all desired elements before starting the next sample. New features include the grating drive, lamp-carousel alignment, pulsed atom source, lamp-drift compensation. and dynamic range control. The grating is driven by an arm the arm by a taut band wound on a drum and the drum directly by a motor. The lamp carousel mounts on an "L"-shaped rocker with one horizontal and one vertical arm. The carousel rotates on a horizontal axis (PI) at the end of the vertical arm. The rocker itself pivots on a horizontal axis (P2) at the corner of the L; it is driven about its axis by a motor (M2) and screw at the other end of the L. Carousel rotation on its axis moves the right lamp into position and adjusts it accurately in vertical direction. Pivoting of the rocker simultaneously on its corner axis positions the lamp accurately in the horizontal direction. The pulsed atom source is a combined angled-gas-jet- and discharge unit. During pulses it yields high absorption with better detectability limits; average power is lower. The lamp-drift compensator makes double duty of the absorber pulsation to obtain a lamp-intensity reading between pulses. Dynamic range control is obtained by even further exploiting the pulsation, namely by taking measurements at a known delay (and decay) time after each pulse.

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IMPROVED AUTOMATIC ATOMIC-ABSORPTIONN SPECTROMETER

BACKGROUND

1. FIELD OF THE INVENTION This invention relates generally to atomic-absorption spectrometry; and more particularly to a new spectrometer for obtaining multiple atomic-absorption measurements much more quickly, easily and accurately.

2. PRIOR ART A commonly used instrumental analysis method for the elemental analysis of various materials for trace and minor elements is the atomic absorption method. In the most used manifestation the analytical instrument consists of a means for generating a vapor such as a nebulizer; a burner assembly to disassociate into free atoms the vapor delivered by S* the nebulizer: a source of monochromatic light such as a hollow cathode lamp which light is directed through the atomized vapor, and a device for isolating and measuring the monochromatic light after it has passed through the atomized vapor. The quantitative measurement of the elements present in the vapor and thus the liquid sample from which the vapor was derived is made by comparing the intensity of the monochromatic light characteristic of an element after absorption in the burner flame to the unabsorbed intensity of the light source.

The wavelength-region isolating device, called a monochromator, requires some mechanism for driving a diffraction grating (or other dispersive element). Some li r ;t

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0l; t i~i.°24 -2prior artisans have driven gratings with sine-bar devices, or direct motor-shaft-to-grating connections. Others have used nonlinear drums or cams for interconnecting grating arms with motors.

The sine-bar mechanism produces a drive whose angular rotation of the motor is substantially directly proportional to the wavelength passing through the r-nchromator. This drive requires a worm gear that is highly accurate throughout its length, and it requires a point of contact between the carriage that rides on the wnn gear and the arm that slides along the arm. The worm gear and the sliding contact are both subject to wear.

Direct grating mount to a motor shaft does not introduce the wearing surfaces of the sine bar, and it allows rapid scanning of the wavelength. Connecting the motor ahaft directly to the grating shaft prodLxes only one -mathemratica! relationship between the motor position and the wavelEngth passing through the nonochromator: the relationship is nonlinear in wavelength and the inverse of wavelength (freqency or photon ergy). A special high precision motor is required to achieve the necessary wavelength precision and accuracy, and the motor must be driven in such a maner that the nonlinearity is compensated for when wavelength scanning is recorded on a strip chart recorder for exanple.

Next we consider the nonlinear drum or cam (mounted 0; a rotor shaft) that is in direct contact with the grating arm. In this case the wavelength range covered is limited by the extent of the motion of the arm as the cam rotates thro gh one full revolution. A ccqrn-ise is necessary between the range of the wavelength region covered and the 3 I accuracy and precision with which the wavelength can be set.

2 We shall only very briefly discuss prior-art devices 3 for lamp positioning and alignment. They are generally 4 rudimentary and unsatisfactory. Most of these devices have a lamp-carrying carousel. For accurate alignment each 6 individual lamp must be manually adjusted on its mount.

7 Prior AA spectrometers are also limited by difficulty 8 in obtaining optical absorption measurements in a favorable 9 range. Precision and accuracy depend greatly on the range in which measurements are made.

11 It should be mentioned that some prior workers have 12 used pulsed lamps. Pulsing of lamps allows signal handling 13 on an a. c. basis, with various well-known advantages.

S14 In atomic-absorption work it is necessary to collect s some information as to the intensity of the light-source signal both in the presence of and in the absence of an *Ij° absorber. This is usually done by atomizing distilled I 18 water, which is essentially nonabsorbing for the 19 monochromatic light used to measure the element, and 20 recording the signal; and then ceasing the introduction of 4 distilled water into the flame and instead atomizing the 22 liquid sample to be analyzed, and recording the signal.

1 "3 This is done rather frequently to compensate for changes in X- 24 the light source intensity with time.

S26" We will further mention that heretofore an important S2b limitation of absorption methods is the limited dynamic 27 range (of absorbance values and therefore concentrations) S 28 over which accurate measurements can be made.

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3A In accordance with one aspect of the present invention there is disclosed a method for making atomic-absorption measurements for a plurality of samples, comprising the steps of: selecting a particular sample; and then analyzing the selected sample for a plurality of elements in turn, one at a time in a preestablished sequence, by making at least one atomic-absorption measurement corresponding to each element of the plurality; and then repeating the selecting and analyzing steps for a plurality of different particular samples.

In a preferred form, for each selected sample, at least one atomic-absorption measurement is made for every element of the plurality before making any atomic-absorption measurement for any subsequent sample.

In a further preferred form, the analyzing step comprises, for one particular element of the plurality, the substeps of: positioning the selected sample for measurement; automatically selecting and moving into measurement position a particular lamp that emits a narrow spectral line of a particular wavelength used for analyzing the selected sample for the particular 20 element; automatically adjusting a monochromator to that particular wavelength of that spectral line; and then automatically sensing the light of that particular wavelength received from that particular lamp through the monochromator and through 25 the selected sample, for use in determining the amount of the particular element in the selected sample.

!IAD/1463o S -4 1 SUMMARY OF THE DISCLOSURE 2 S3 The spectrometer system consists of these basic parts: 4 1. a light-source system that has up to 16 different hollow-cathode lamps mounted in a carousel so j 6 that each lamp can be rapidly and accurately 7 positioned in the optical path when needed; i 8 2. a sampling system that converts a sample into an 9 atomic vapor so that the absorption of the atoms can be determined and related to the 11 concentration in the original sample; 12 3. a monochromator that isolates the wavelength 0 0 013 region of interest, converts the light into an 0* 00 *0'14 electronic signal via a photomultiplier tube and 0* 15 displays and records the results; and .16 4. a computer system that controls the system and j S 17 processes and displays the measurements.

18 Our instrument differs in two fundamental ways from S now-existing multielement AA instruments. First, it analyzes each sample fully for all desired elements before 21 moving on to the next sample. Conventional multielement AA 22 instruments analyze a group of, say, fifty samples by 23 determining a single element in all of them, then going to 24 a second element, and so on. Second, our instrument is 6O 25 intended for use with the Analyte Atomsource (trademark) i 26 nonthermal atomizer, which is designed for the analysis of n 27 solid, undissolved samples. Conventional atomic-absorption 28 instruments use either a flame or a furnace atomizer, both i "11 O *i\ \%Wy^w U6,V^

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Fitted with the Atomsource Atomizer, our spectrometer preserves the flame-AA advantages of specificity and ease of use, but gives even better precision RSD), and can determine a wide range of concentrations, from ppm to constituent levels, with little or no sample preparation. Our invention also has good sensitivity for refracto"y elements such as B, Si, Ti and W, which in conventional AA give problems. A lab might therefore consider using the present AA instrument instead of, or as a supplement to, an X-ray fluorescence or an arc/spark emission spectrometer.

The present invention is equipped with a turret that can hold sixteen hollow-cathode lamps, some of which can be multielement sources. If the first element to be determined in a given sample is, say, silver, and the second is iron, the automated operation is as follows.

The instrument source optics are set automatically to accept light from the silver hollow-cathode lamp, while the monochromator drives to the preselected silver wavelength.

Immediately after silver has been determined, the optics move to select the emission from the iron lamp, while the monochromator moves to the iron wavelength, and so on until the sample has been completely analyzed. The time for each..

determination can be as short as five seconds per element. A sample can be analyzed for ten elements in sixty seconds, and for twenty elements in under two minutes.

Physically, our invention consists of three modules.

The optical module includes the lamp turret, monochromator, 0000

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0@ 0000 fi S3 *r @0 *B beT- 6 -6- 1 power supplies, and microprocessor controllers. The second 2 module is the Atomsource Atomizer. The third is an IBM- 3 compatible personal computer, which provides all required 4 control and intelligence for instrument and atomizer.

The present instrument can also be provided with a 6 conventional atomic-absorption flame atomizer. In the 7 flame mode, our invention has performance that is 8 approximately equivalent to that of a good sequential ICP 9 (inductively coupled plasma) spectrometer. Our invention has, however, far fewer spectral interferences, and can use 11 all the well-established atomic-absorption methods that 12 have been developed over the past twenty-five years. Our 13 invention is therefore worth considering as an alternative s ee S 14 to sequential ICP instruments.

so 15 Our new spectrometer incorporates these improvements, 16 which will be discussed in this order: 17 1. grating drive, 18 2. lamp-carousel optical-alignment method, 19 3. pulsed atom source, I ii!! 20 4. compensation method for lamp intensity drift, and 21 5. dynamic range control.

22 The grating is driven by an arm, the arm in turn by a 23 taut band wound on a drum, and the drum directly by a 24 motor. The arm is spring-biased to hold the band taut.

*s 0 25 This drive system is far less susceptible to S26 frictional wear than prior-art sine-drive systems. It is 27 also far less demanding of motor-drive precision than 28 earlier direct-motor-drive systems.

a o rhT w1 -7- The lamp-carousel subsystem includes an "L"-shaped 2 rocker carriage, with one horizontal and one vertical arm.

3 The carousel is mounted to rotate on a horizontal axis at 4 the erd of the vertical arm. The rocker itself pivots on a horizontal axis at the corner of the L; it is driven about 6 its axis by a motor and near-vertical screw at the other 7 end of the L.

8 Rotation of the carousel on its axis moves the right 9 lamp into position and adjusts it accurately in the vertical direction. Pivoting of the rocker simultaneously 11 about its corner axis positions the lamp accurately in the 12 horizontal direction.

13 The pulsed atom source is a combined angled-gas-jetand-discharge device. During the pulses it provides high 4 -*615 absorption with better detectability limits; average power is lower.

Prior art includes pulsing a hollow cathode lanp, which is a glow .oe o..

j 18 discharge. It is not obvious however from this prior art that this 19 special combined discharge can be pulsed. For example, it wiuld be 0 20 reasonable to expect that a gas jet whien suddenly turned on would blow e••I out the electrical discharge.. It would also be reasonable to expect that 22 the presence of a jet prior to turning on the electrical discharge would 23 make it impossible to rapidly establish during the electrical pulse an 24 electrical discharge in the rapidly moving jet. Even if it were not possible to establish a pulsed mode of operation (where the jet or |0 electrical discharge are suddenly turned on) it is still possible to 27 establish the previously kaxwn continuous mode of operation of the 28 combined discharge by tle_ different means of slowly turning on the Jet.

i: 1~ -8ii The lamp-drift compensator makes double duty of the 2 absorber pulsation to obtain a lamp-intensity reading 3 between pulses. This intensity reading can be used to 4 provide correction, i. establish a more stable baseline, in view of lamp-intensity fluctuations.

6 Dynamic range control is obtained by even further 7 exploiting the pulsation, namely by taking measurements at 8 a known delay (and decay) time after each pulse. Decay of 9 the discharge is reproducible; hence the time delay used can be translated into an absorption-value correction 11 factor.

12 All of the foregoing operational principles and .13 advantages of the present invention will be more fully i U appreciated upon consideration of the following detailed description, with reference to the appended drawings, of Iwhich: 18 19 BRIEF DESCRIPTION OF THE DRAWINGS 2T Fig. 1 is a simplified and highly schematic diagram of :22 the taut-band grating drive, which in principle may be 23 either in elevation or in plan.

24 Fig. 2 is a like diagram of the lamp-carousel .46.21 positioning system, except that it is preferably considered 26 as an elevational view.

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9 1 DETAILED DESCRIPTION 2 OF THE PREFERRED EMBODIMENTS 3 4 1. Grating Drive.

The mrtchroator has a grating that disperses light of different 6 wavelengths in different directions. The wavelength of light that passes 7 through the monochromtor is determined by the rotational position of 8 the grating. The rotatironal position of the grating is deterrndied by a 9 unique drive mechanism.

Figure 1 is a schematic diagram of the grating and its unique drive 11 mechanism. The grating is monted so that its front surface G pivots 12 about an axis at point P. An arm A is attached to the grating mount to 13 allow the grating to be rotated as the taut band or wire B pulls on the :.1.4 arm. The taut band or wire is connected to the arm at a hinge point H. A spring S helps to keep the band or wire taut. The band is corrected to a S" drum D at point C and wraps around drum, less than one time or up to 0 1 many times around the drum. The drum is rotated about its axis M by a motor (stepping, synchronous, or servo).

19 i| T1 This nechanism is unique for at least two reasons: see.

2* (1)because a taut band or wire comects the arm of the grating W drive to a motorized drum and e23 (2)because the particular arrangement of the parts causes the .24 angular position of the grating, and more importantly the wavelength 25 that passes through the nxtchroator, to be related by a unique 0 0o 26 mathematical function to the angle of drum D; no other grating drive 27 mechanism relates the angle of a notor shaft to the angle of the grating 28 drive by this same mathematical function. This mathematical function I; T r L 0 m I 1 depends upon the length of the arm A, the length of the taut member B, 2 the diameter of the drum D, the distance between the pivot points of the 3 drum M and the grating P, and the rhape of the drum. The drum may be 4 circular in shape, or it may be nachined to have a shape that prodxces a particular desirable mathematical relationship. For example, the dnrn 6 could be shaped so that the angle of the drum position could be directly 7 proportional to the energy of the light passing through the 8 ntnochromator (that is, inversely proportional to the wavelength). Or 9 the drum could be shaped so that the angle of the drum position is directly proportion to wavelength.

11 When the functional relationship between rotor position and 12 12 wavelength deviates fron a desired relationship, the deviation can be corrected by the cop.uter supplying an offset number for 1 the position of the otor. In this case the offset rnrber can be calculated nore quickly when the deviation has the simplest mathematical form. The versatility of the taut band system to adjust the functional relationship by selecting dimensions I-y S18 listed in the previous paragraph helps to achieve a deviation 19 with the simplest nmathemnatical form.

46** £"As will be recalled, we have explained above various disadvantages of sine-bar drives, direct motor-to-grating 3 2 drives,, and nonlinear cam or drum systems. We there noted 23 that prior-art drive systems of the sine-bar type-are particularly susceptible to wear.

The taut band system is not subject to such wear because there are 26 no gears if the motor is connected directly to the drum shaft M, and 27 there is no sliding contact that moves along the arm A. The taut band 28 system also allows the wavelength to be changed ch more rapidly than syst0in also allows the wavelength to be changed nuch more rapidly than

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I would be reasonable (because of rapid wear) for the worm gear system.

S2 (The worm gear in this application must have a very fine pitch because 3 the grating must be positioned with great accuracy to achieve a 4 reproducible wavelength setting that is better than 0.1 narnxeters. The fine pitch requires exceptionally high speed rotation for rapid 6 scanning.) 7 8 In addition to being more versatile than the direct drive motor 9 system in the functional relationship between motor shaft position and wavelength, the taut band system does not require a motor with such high 11 precision when the diameter of the drum D is considerably less than the 12 length of the arm A. The demand on precision is decreased by 01."13 approdximately the ratio of these two dimensions.

0 0 0 The taut band system is able to cover a wide welength range with o accuracy, especially when a circular drum is used and the diameter of *16 the drum is smaller tai the length of the arm. (In this case the taut

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band wraps around the drum more than once during a wide wavelength 18 scan.) Unlike the cam drive, when a nonlinear drun is used with the taut 19 band system, the functional relationship between motor position and 20 avelength is determined not only by the shape of the drunm, but as "2121 mentioned above also by the length of the arm A, the legth of the taut 22 member B, the average diameter of the drum D, and the distance between 23 the pivot points of the d-rum M and the grating P. The taut band system *4 has no member that rubs against the grating arm as does the camn system.

.5 Another advantage is that thLis is mnore efficient than the acme lead 26 screw and therefore energy required and drive costs are lower for the 27 sarme performance.

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12 2. Lamp carousel optical alignment Each different chemical element who*se absorption is to be determnined requires a different hollow cathoxde lamp. In a few cases one lamp moy suffice for a few different eleents. Up to 16 lamps are mounted on a lamp cxrousel that rapidly rotates each lanp into an accurately determined position in the optical path ten the laap is needed.

A unique (and necessary) feature of the carousel is its ability to accurately and rapidly position each lamp that is present in the carousel. It does this rapidly because of the way that the carousel is pivoted about two points PI and P2 in Figure 2. Pivoting about PI m7oes the proper lamp into position and positions it accurately in a substantially vertical direction. Pivoting about P2, which occurs essentially during the sam tie that the movemenit about PI occurs, positions the lamp accurately in a substantially horizontal direction.

Figure 2 shws the motion about P2 being done with a worm gear W driven by a motor S2. O'ser driving methods are possible, such as a direct connection of the shaft of P2 to a motor shaft.

A unique feature of the carousel is the use of pivoting around tw pivots to align the larrp in the horizontal and vertical directions.

Pivoting can be done more rapidly and with a simpler mechanism than moving the entire carousel horizontally along a linear translation stage for exanple.

In operation, when a lamp is first mounted in the carousel, the computer system that controls the spectrometer scans the lamp alternately about FPI and P2 two or three times in each direction to determine uihen the lamp is centered on the optical axis.The two motor positions (for the motors that drive the carousel about P1 and P2) are j I Di MMMMMIMMMM 1- 13 1 then stored in memory for later use to position the lamp when the lamp 2 is reded during a chemical analysis.

3 4 3. Pulsed atcrn source One claim here is for a pulsed means of remrving atons frcm the 6 surface of a solid sample (and keeping the atoms in a substantially free 7 state long enough for them to be observed) that combines the removal B 8 effects of at least one jet of gas disposed adjacent such sample 9 surface and pointing at a substantially nonzero angle toward such surface and a low pressure electrical discharge. lhere are three 11 ways to pulse this special type of discharge pulse the electrical 12 discharge, pulse the gas jet, and pulse both simultanexusly.

*13 Another claim is that pulsing the atom source has the advantage of getting high absorption genrated by high current pulses without the 0 •:nM instability associated with high current DC operation. This also permits I "•f better limits of detectability for less power costs.

S18 19 4. Compensation method for lamp intensity drift 2t It is uniquely possible when using a pulsed atom source to supply the :22 absorbing atons from the sample material, to obtain these t) signals by 23 recording the signal before each pulse and then recording the signal :24 after the pulsed atom source has been turned on and the absorbing sample atoms are in the optical path. The general claim here is either this 0 26 method of obtaining these two signal before and during each pulse or/and 27 the use of a pulsed absorber to allow this ethod to be used x-itholut 28 14 using an external force to physically manipulate the ronabsorber mid absorber between these measurements.

By making these two reasurements for each pulse, it is possible to compensate for relatively rapid changes with time in the light sour-ce intensity. If the measurement of the nxiabsorber signal is made just prior to (within microsecondis of) turning mn the sam~pling pulse, then the compensation can be achieved oni a time scale that is considerably shorter than can be done with the mrethods that involve physical manipulation (even with mrech-anically vibrating systm); mo're rapid changes in the lamp intensity can thereby be tolerated.

Thlis pulsed methodi also has the advantage of observing the saepr of the beanm from the lamrp for both signals, arnd with the same optical coponnts in the beam~. D,.ible 'beam system~ either observe different parts of the beam at the samre time, or the same part of the beam~ with different optical ccxpnets in each beam. W.hen different parts of the beam are observed, each part my behave somewhnat differently, and the comrpensationi will not, then-, be ccxapletely accurate. W-)en the sane part is observed by different optical components, then the optical components may not be identical, causing the compensation to be somewhiat inaccurate.

Tt-e claim~ presented here are not restricted to solid sanple atomizationi but apply to flame atomrizationi as well.

Another embdiment of this claim is the use of a pulsed light source that is syrronized with the pulsed absorbing sou~.rce so that a nabsorber light measurement pulse occurs just prior to the pulse of the absorbing source, andi another occurs after the absorbing source is ]i 15 S1 pulsed on.

2 Also the separation of the atomization process from the absorption 3 measurement temporally, also eliminates the emission noise from the 4 absorption measurement thus improving detection limits.

In addition high intensity light source pulses reduce front end noise 6 7 mproving detection limits.

8 5. Dynamic range control.

9 The use of a pulsed source of absorbing atoms allows the dynamic range to be easily extended without changing 11 wavelength and without a significant loss of time or sample. This unique 12 mrrethod involves making measurments at a known delay time after the absorber pulse is turned off (and the absorption has had a chance to I .j decay) when the absorption is too high during the pulse.

When a continuous light source is used, then many measurenents can 1'*l •I be made at fixed delay-time intervals after each pulse. The data for the best delay-timne interval are then selected for use after the S18 measuriennts have been conpleted. When a pulsed light source is used, 19 then a measurement made during a previous absorber pulse can be used to select the delay time to pulse the lamp for the present absorber pulse.

S21 Alternatively, the delay time can be set before a sample is run if some C...22 previous knowledge of the approximate range of concentration is 23 available for the sanple.

7, In practice, the relationship between delay time and absorbance

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S" .2l relative to the absorbance that occurs during the absorber pulse is 26 determined by measurement. This relationship is used to establish a S 27 large dynamic range over which concentrations can be accurately S28 compared; that is, the delay time and the measured absorbance are both 1^^1 4i O< o 0i I I 16 entered into this relationship to obtain an effective absorbaryze (or 2 parameter with some other name) for crparison paxrposes over a large 3 dynamic range of concentrations.

4 It will be understood that the foregoing disclosure is intended to be merely exemplary, and not to limit the scope 6 of the invention which is to be determined by reference 7 to the appended claims.

9 11 12 0 ge .19 :*2 61 so. *26 23 26 27 AI 28

Claims

2. The method of claim 1, wherein, for each selected sample, at least one atomic-absorption measurement is made for every element of the plirality before making any atomic-absorption measurement for any subsequent sample.
3. The method of claim 1 or 2, wherein the analyzing step comprises, for one particular element of the plurality, the substeps of: positioning the selected sample for measurement; automatically selecting and moving into measurement position a particular lamp that emits a narrow spectral line of a particular wavelength used for analyzing the selected sample for the particular element; automatically adjusting a monochromator to that particular wavelength of that spectral line; and then automatically sensing the light of that particular wavelength received from that particular lamp through the monochromator and through the selected sample, for use In determining the amount of the particular element in the selected sample.
4. The method of claim 3, wherein the analyzing step further comprises, for a second particular element of the plurality, the subsequent substeps of: while the selected sample remains positioned for measurement, automatically selecting and moving into measurement position a second narrow-line lamp that emits a spectral line of a second wavelength used for analyzing the selected sample for the second particular element; while the selected sample remains positioned for measurement, automatically adjusting a monochromator to the second wavelength; and 463o 1 18 then, while the selected sample remains positioned for measurement, automatically sensing the amount of light of the second wavelength received from the second lamp through the monochromator, for use in determining the amount of the second particular element in the selected sample. The method of claim 3, wherein the analyzing step further comprises, for a particular element of the plurality, the subsequent substeps of: while the selected sample and the particular lamp remain in position, automatically adjusting the monochromator to a second particular wavelength used for analyzing the selected sample, said second particular wavelength corresponding to a second narrow spectral line emitted by that same lamp; and then, while the selected sample remains positioned for measurement, automatically sensing the amount of light of that second wavelength received from that same lamp through the monochromator, for use in determining the amount of the particular element in the same selected sample. A method for making atomic-absorption measurements for at •least one sample, with respect to a plurality of elements; said method comprising the steps of: S: automatically determining optimum instrument settings for each element, including the position of a lamp used for making a measurement for that element; and automatically recording values representative of the determined optimum instrument settings for each element; after the determining and recording steps, selecting a particular sample; and i then automatically analyzing the selected sample for a plurality of elements in turn, one at a time in a preestablished automatic sequence, by making at least one atomic-absorption measurement corresponding to each element of the plurality; and wherein: the analyzing step comprises, for each element, the substep of automatically recalling the recorded values for that element; IAD/14630 i r. 19 the analyzing step also comprises, for each element, the substep of automatically using the recalled values to restore the determined optimum instrument settings for that element; the determining step comprises scanning each lamp along substantiaiiy orthogonal directions to determine an optimum position of that lamp relative to an optical axis; the values recorded in the recording step comprise lamp-position values representative of the optimum position of each lamp along the substantially orthogonal directions; the recalling substep, for each element, comprises recalling the recorded lamp-position values for a lamp associated with that element; and the using substep, for each element, comprises using the recalled lamp-position values to control a servomechanism in automatic repositioning of the associated lamp at the optimum position along the substantially orthogonal directions.
7. The method of claim 6, wherein: said scanning comprises scanning each lamp at least twice o alternately along said substantially orthogonal directions.
8. The method of claim 6, wherein: .in the analyzing step, said at least one atomic-absorption measurement corresponding to each element of the plurality is made before making any atomic-absorption measurement for any other sample. S. 9. The method of claim 8, wherein: the plurality of elements constitutes all of the elements of interest for the selected sample. The method of claim 6, further comprising the step of: after the selecting and analyzing steps, repeating the selecting and analyzing steps for a plurality of different particular samples. Y 11. A method for making atomic-absorption measurements for a plural-ity of samples, comprising the steps of: selecting a particular sample; and i then analyzing the selected sample for a plurality of elements in turn, one at a time-in a preestablished sequerse, by making at least i i AA IlAD/1463o i Yi M t 20 one atomic-absorption measurement corresponding to each element of the plurality, before making any atomic-absorption measurement for any other sample; and then repeating the selecting and analyzing steps for a plurality of different particular samples; wherein the analyzing step comprises, for one particular element of the plurality, the substeps of: positioning the selected sample for measurement; having in, or moving into, measurement position a lamp that emits light used for analyzing the selected sample for the particular element; automatically isolating, from the light emitted by the lamp, a narrow spectral band about a particular wavelength used for analyzing the selected sample for the particular element, by automatically adjusting a monochromator to that particular wavelength of that spectral band; and than automatically sensing the amount of light of that particular wavelength received in that isolated band through the monochromator and through the selected sample, for use in determining the amount of the particular element in the selected sample.
12. The method of claim 11, wherein the analyzing step further comprises, for a second particular element of the plurality, the subsequent substeps of: while the selected sample remains positioned for measurement, automatically isolating a second narrow spectral band, about a second !wavelength, used for analyzing the selected sample for the second particular element; while the selected sample remains positioned for measurement, .automatically adjusting a monochromator to the second wavelength; and then, while the selected sample remains positioned for measurement, automatically sensing the amount of light of the second wavelength received in the second band through the monochromator and through the selected sample, for use in determining the amount of the second particular element in the selected sample.
13. A method for making atomic-absorption measurements for a plurality of samples, comprising the steps of: i AD/1463o T i 0 *Vr '7 1 I 21 selecting a particular sample; and then analyzing the selected sample for a plurality of elements in turn, one at a time in a preestablished sequence, by making at least one atomic-absorption measurement corresponding to each element of the plurality, before mking any atomic-absoption measurement for any other sample; and then repeating the selecting and analyzing steps for a plurality of different particular samples; wherein the analyzing step comprises, for one particular element of the plurality, the substeps of: positioning the selected sample for measurement; having in, or moving into, measurement position a lamp that emits light used for analyzing the selected sample for the particular element; automatically isolating, from the light emitted by the lamp, a narrow spectral band about a particular wavelength used for analyzing the selected sample for the particular element; by automatically adjusting a monochromator to that particular wavelength of that spectral band; then automatically sensing the amount of light in that particular band received through the monochromator and through the S selected sample, for use in determining the amount of the particular element in the selected sample; then, while the selected sample and the lamp remain in position, automatically selecting, from the light emitted by the lamp, a second narrow spectral band about a second particular wavelength used for analyzing the selected sample for the particular element; then, while the selected sample and the lamp remain in position, automatically adjusting the monochromator to the second particular wavelength used for analyzing the same selected sample; and then, while the selected sample remains positioned for measurement, automatically sensing the amount of light in the second band received from the same lamp through the monochromator and through the selected sample, for use in determining the amount of the particular element in the same selected sample. i 1AD/1463o gAIT 0 22
14. A method of making atomic-absorption measurements I substantially as described herein with reference to the drawings. DATED this FOURTH day of MARCH 1992 I Thomas John Scuitto Theodore James Scuitto i Al E. Bernhard Patent Attorneys for the Applicants SPRUSON FERGUSON S** I AD/1463o oo oo *o*o* go* *o o*o* 1*1 0*