US3708228A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Sampling technique for atomic absorption spectroscopy
Assignee: Applied Biosystems Inc
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Filing: 1971-04-30
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Granted: 1973-01-02
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Expires: 1991-04-30
Abstract
Abstract A sampling technique for atomic absorption spectroscopy uses a very small quantity (e.g., 10 Mu l) of, for example, an organic fluid (e.g., blood) for determining small relative quantities of a reasonably volatile metal (e.g., lead). The sample is placed in a small cup-shaped holder and dried by heating; the organic components are then at least partially oxidized as by adding 20 Mu l of 100-volume (30 percent) hydrogen peroxide solution and heating until completion of reaction and redrying, both heating steps being at about 140* C by means of a hot plate. The sample holder is then placed under a central aperture in a relatively long absorption tube located in the conventional flame so as to surround the conventional radiation beam of an atomic absorption spectrometer. The relative diameter of the sample holder and of the absorption tube aperture and their relative position are such that a small proportion of the flame enters the aperture so that the sample material is caused to enter the absorption tube but is not flushed out of the open ends thereof for at least a few seconds. Both improved reproducibility and a sensitivity gain factor of about 5 is obtained relative to the use of somewhat larger non-symmetrical (e.g., boat-shaped) sample holders without an absorption tube. Blood lead levels of less than 0.1 Mu g per ml (i.e., less than 0.001 Mu g in a 10 Mu l sample) can readily be determined at an analysis rate of up to 50 samples per hour.
Inventors
- 👤 H Delves
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 22:00
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/62; G01N21/71
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
290 words
In an atomic absorption spectrometer for determining the quantity of a metallic element of interest in a sample material of the type having: a source of radiant energy including at lease one spectral line corresponding to an absorption line of said element of interest in its atomic state; means for directing a beam of said radiant energy through a sample location at which a flame is located to a spectrometric system, said system including a detector for measuring the amount of absorption occurring at said atomic spectral line so as to yield an indication of the quantity of said metallic element of interest contained in said sample material, the improvement comprising: an open-ended elongated tube of substantially constant interior cross-section positioned at said sample location, above and therefore in thermal contact with the flame, said tube having its longitudinal axis aligned with said beam of radiant energy so that said tube surrounds at least a substantial part of said beam; said elongated tube comprising a symmetrical sample-receiving aperture in its bottom surface, substantially at the middle of its longitudinal length; a symmetrical substantially cup-shaped sample holder positionable in the flame directly below said sample-receiving aperture; said sample-receiving aperture and the upper part of said cup-shaped sample holder being of such relative diameter and being spaced vertically apart such a distance that an extremely small part of the flame enters said sample-receiving aperture along with the vaporized sample components, whereby at least a substantial amount of said metallic element of interest is rapidly caused to enter said tube and therefore said beam of radiant energy in its atomic state, and said tube causes said metallic element of interest to remain in said radiant energy beam for at least a few seconds.
Claim 2
Dependent Claim
85 words
An improved atomic absorption spectrometer according to claim 2, in which: the diameter of said upper part of said cup-shaped sample holder is slightly larger than the diameter of said sample-receiving aperture; and said upper part of said sample holder is spaced below the effective plane of said sample-receiving aperture a distance somewhat greater than the difference between said diameters, whereby a small part of the flame can enter said sample-receiving aperture by travelling around the edge of said upper part of said sample holder.
Claim 3
Dependent Claim
75 words
An improved atomic absorption spectrometer according to claim 3, in which: the relative diameters of said upper part of said cup-shaped sample holder and of said sample-receiving aperture are such that said sample holder upper part diameter is approximately 1/2 unit larger than said sample-receiving aperture diameter; and said upper part of said sample holder is spaced below the effective plane of said sample-receiving aperture a distance of between about 1 and about 3 units.
Claim 4
Dependent Claim
52 words
An improved atomic absorption spectrometer according to claim 3, in which: the longitudinal length of said elongated tube as measured between its open ends is about an order of magnitude greater than the diameter of said sample-receiving aperture, whereby the vaporized sample components remain within said elongated tube for an appreciable time.
Claim 5
Dependent Claim
75 words
An improved atomic absorption spectrometer according to claim 5, in which: the effective average interior diameter of said elongated tube is the same order of magnitude as said diameter of said sample-receiving aperture and therefore is about an order of magnitude less than said longitudinal length of said elongated tube, whereby the vaporized sample components substantially fill the interior cross-section of said elongated tube well before they reach and therefore leave the open ends thereof.
Claim 6
Dependent Claim
22 words
An improved atomic absorption spectrometer according to claim 2, in which: said open-ended elongated tube comprises at least about 99 percent nickel.
Claim 7
Dependent Claim
21 words
An improved atomic absorption spectrometer according to claim 2, in which: said cup-shaped sample holder comprises at least 99 percent nickel.
Claim 8
Dependent Claim
314 words
In an atomic absorption spectroscopic analysis technique of a sample material of the type in which: a beam of radiation, including at least one spectral line corresponding to an absorption line of a metallic element of interest in its atomic state contained in said sample material, is traversed through a sample location at which a flame is located, and then is detected in such a way as to measure the amount of absorption occurring at said atomic spectral line, so as to yield an indication of the quantity of said element of interest in its atomic state, the improvement for analyzing a liquid sample containing both such metal of interest and a substantial quantity of at least one oxidizable organic component comprising: a. placing a known quantity of said liquid sample in a small symmetrical crucible; b. drying the original liquid sample in said crucible; c. heating the dried sample in said crucible under such conditions and at a temperature sufficiently high to cause both a substantial oxidization of at least some of the oxidizable components of the original liquid sample and subsequent drying of said mixture, said temperature, however, being below the ignition temperature of said components; d. and positioning said symmetrical crucible into the flame at said sample location in such manner that the vaporized sample components, including said metallic element of interest in its atomic state are carried by the flame into the path of said beam of radiation while also causing said components to be held in said beam for a period of time substantially greaTer than the normal traversal time of said flame across said beam, whereby the nonspecific radiation absorption of said organic components is reduced and the absorption of said metallic element of interest in its atomic state is separated in time from said nonspecific absorption, so as to facilitate separate measurement of said atomic state absorption.
Claim 9
Dependent Claim
31 words
An improved atomic absorption spectroscopic analysis technique according to claim 9 in which: an oxidizing agent is added to the dried sample in said crucible prior to the heating step (c).
Claim 10
Dependent Claim
53 words
An improved atomic absorption spectroscopic analysis technique according to claim 9 in which: said liquid sample is blood; and a volume of 30 percent hydrogen peroxide solution approximately equal to twice the volume of said liquid blood sample is added following the initial drying step (b) and prior to the heating step (c).
Claim 11
Dependent Claim
23 words
An improved atomic absorption spectroscopic analysis technique according to claim 9 in which: said heating step (c) is performed at approximately 140* C.
References Cited (Backward Citations)
US3565538A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-01-02 | 1976-07-03 | 1977-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-02 | 1980-07-03 | 1981-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-02 | 1984-07-03 | 1985-01-02 | $7700.00 | Window Closed / Lapsed |