JPH02502402A - Improved automatic atomic absorption spectrometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Improved automatic atomic absorption spectrometer General technical information Commonly used to analyze elements in various materials and trace trace elements. The analytical measurement method used is atomic absorption spectroscopy. In the most commonly used methods, analytical equipment The vapor phase is generated by means of vapor phase generation such as a nebulizer and the nebulizer. A burner mechanism is used to dissociate the atomized vapor into free atoms, and a burner mechanism is used to inject light into the atomized vapor. A monochromatic light source such as a hollow cathode lamp for transmitting atomic vapors and It consists of a device for separating and measuring monochromatic light. vapor phase odor and therefore the determination of the elements present in the liquid sample that gave it its vapor phase. The amount measurement is based on the monochromatic light characteristic intensity depending on the element after being absorbed in the burner flame. This is done by comparing the unabsorbed intensity of the light source.

Disclosure of invention The spectroscopic analysis system consists of the following basic parts:

1. 16 different follows in carousel Equipped to allow cathode lamps to be positioned quickly and accurately in the light path as required light source.

2. Convert the sample to atomic vapor and measure the absorption by the atoms, and sampling system for correlating concentrations in samples.

3. Separate the wavelength range of interest and convert the light into an electrical signal via a photomultiplier tube A monochromator for converting, displaying, and recording the results.

4. Combinator system for controlling the system, processing and displaying measured values Tem.

The system of the present invention described above has the following five improvements related to the claims. Exists.

1. Lattice drive 2. Optical alignment method of lamp carousel 3. Pulsed atomic source 4. Compensation method for lamp intensity drift 5. Dynamic range control These will be explained in order below.

1. Lattice drive A monochromator has a grating to disperse light of different wavelengths in different directions Ru. The wavelength of light passing through the monochromator is determined by the rotational position of the grating. grid The rotational position is determined by a novel drive mechanism.

FIG. 1 is a diagram showing the grid and its novel drive mechanism. The grid is in front of G is mounted so that it can rotate around an axis indicated by point P. Arm A is on the grid When attached, when the tote band or wire B pulls its arm, the It is designed to rotate the child. The tote band connects to the arm at hinge point H. tied together. Spring S maintains tension on the tote band. toe The band is connected to the drum D at 6 points and rotates around the drum less than once or It can be wrapped several times. The drum is driven by a motor (stepping, synchronous, or can be rotated around its axis M by a servo motor).

This mechanism is novel in at least the following respects.

(11)-) The band connects the arm of the lattice drive to the motor-driven drum. To be of.

(2) The specific mechanism of the system component depends on the angular position of the grating, more specifically on the motor. Relating the wavelength transmitted through the nochromator as a mathematical function to the angle of drum D Any other lattice drive mechanism also adjusts the motor shaft angle to this value. It is not to relate the lattice drive angle by the same mathematical function. . This mathematical function consists of the length of arm A, the length of tote member B, the diameter of drum p, and the This depends on the distance between the ram pivot point M and the grid pivot point P, and the shape of the drum. be. The drum may be circular or shaped to produce certain desired mathematical relationships. machined into shapes. For example, if the angular position of the drum is measured using a monochromator, a shape that is directly proportional to the energy of the light it emits (i.e., inversely proportional to the wavelength) It can be done.

When the functional relationship between motor position and wavelength deviates from the desired relationship, the deviation is called a controller. is corrected by the computer supplying the number of offsets in the motor position. Ru. In this case, the offset number is compared to when the function deviation has the simplest formula Calculated quickly. The accommodation adaptability in the functional relationship of the taut band system is This is caused by choosing the algebra mentioned above, but this is a simple mathematical formula. It is useful for correcting deviations.

The drive mechanism of the grating arm according to the prior art consists of a sine bar type. this is The wavelength at which the rotation angle of the motor in the drive talIl passes through the monochromator It is designed to be substantially directly proportional to . This drive mechanism is A worm gear finished with high precision is required, and on top of this worm gear Requires the contact point between the riding carriage and its arm to slide along the arm. seek Both worm gears and sliding contacts are subject to wear.

Tote band systems are not subject to such wear.

In other words, gears are not required in a mechanism where the motor is directly connected to the drum shaft M. This is because there are no contacts that move along arm A. tote bandoshi The stem also has a wavelength that is lower than what would be reasonable for a worm gear system. Wavelengths can be switched at high speeds (speeds that would traditionally cause wear and tear).

(The worm gear in this application must have a very precise pitch. stomach. This is a highly accurate method that allows wavelengths to be set reproducibly to within 0.1 nanometers. This is because the grid must be placed at. This precise pitch is exceptional This requires high-speed rotation for rapid scanning. ) Conventional technology drive The mechanism also includes mounting the grid directly on the motor shaft. child The sign bar should not have an abrasive surface that would allow rapid scanning of wavelengths. stomach. The direct connection of the motor shaft to the grid shaft is based on the motor position and through the monochromator. There is only one mathematical relationship between the The relationship is that wavelength is nonlinear, and the reciprocal of wavelength (frequency or photon energy) It is what happens. In order to achieve the required wavelength precision and accuracy, particularly high-precision modes are required. A wavelength scan is required, and this motor records the wavelength scan on a chart paper recorder. When driven, it must be driven such that its nonlinearity is compensated for.

The Tautband system is based on the functional relationship between motor shaft position and wavelength. In addition to greater flexibility than direct drive motor systems, the diameter of drum D It does not require a high-precision motor like the conventional technology when the length is considerably shorter than It is. The need for precision and accuracy is determined by appropriately determining the ratio of these two elements. decrease more.

The prior art also uses non-linear drums or cams (motorized) that directly touch the grating arms. (mounted on the shaft). In this case, the wavelength range covered The range is limited by the range of motion of the arm during one full revolution of the cam. covered There is a certain compromise between the range of wavelength ranges to be used and the precision and accuracy for setting the wavelength. is necessary.

Tautband systems can cover a wide wavelength range with high precision . This is especially true when a circular drum is used and the drum diameter is shorter than the arm length. can do well. (In this case, the taut band is It is wrapped around the drum one or more times. ) Unlike cam drives, totebas When a nonlinear drum is used with a waveguide system, the relationship between motor position and wavelength is The numerical relationship is not determined only by the shape of the drum; as already mentioned, it depends on the arm , the length of tote member B, the average diameter of drum D, and the pivot point M of the drum. It is also regulated by the distance to the axis point P of the grid. The tote band system is It does not have any members that rub against the lattice arms, as did other system systems. .

Another advantage of the system of the present invention is that it is more efficient than apical lead screws and therefore This means that energy requirements and driving costs can be reduced for the same performance. Ru.

2. Lamp carousel optical alignment method Each different chemical element whose absorbance is to be measured should be followed by a different cathode lamp. It requires In some cases, for several different elements It is sufficient to use one lamp. 1 mounted on the lamp gear row cell The six lamps are arranged so that each lamp occupies the exact position in the optical path when needed. is rapidly rotated.

A new (and necessary) feature of the carousel is that it accurately and quickly This is the ability to position quickly. It is the 21 point and carousel in Figure 2. This can be done quickly by rotating each of the points around the 22 points. Pl's Rotation around selects a reasonable ramp and makes it virtually vertically accurate. It is used for positioning. Also, the rotation around P2 is basically 21 above. occurs at the same time as rotation about a point, which causes the lamp to move in an essentially horizontal direction. The object is to bring it to the exact location where it is placed. Figure 2 shows the motor driven by motor M2. It shows the rotation around P2 caused by the ohmic gear W.

This can be done by other drive methods such as directly connecting the shaft of P2 to the motor shaft. It is possible.

A novel feature of the carousel is that it allows the lamps to be aligned horizontally and vertically. , using rotation around two pivot points.

Rotation is, for example, a horizontal movement of the entire carousel along a linear translation stage. It also takes place quickly with a simple mechanism.

In actual operation, when one lamp is installed in the carousel, the spectroscopic The computer system that controls the analyzer determines whether the lamp is aligned on the optical axis. To determine, the lamp is placed around Pl and P2 alternately in each direction. Scan 2 or 3 times. Two motor positions (motor moves the carousel to Pl and P2) ) is now stored in memory and a certain lamp is Used for positioning if required during analysis.

Prior art systems also provide a system in which the carousel moves about a pivot point P1; The accuracy of element alignment allows the mounting mechanism for each individual lamp to be manually operated. It includes the configuration.

3. Pulsed atomic source One claim provides for separating atoms from the surface of a solid sample (and The pulses are kept in a substantially free state for a period sufficient for their observation. This means using means of This means (a) is in close proximity to such sample surface; the separation effect of at least one gas jet arranged at It is a combination of To pulse this special form of discharge, (1 ) pulsing the electrical discharge; (2) pulsing the gas jet; and (3) There are three modes: both pulses are energized at the same time.

Another claim item addresses concerns that pulse energization of atomic pulsed light sources is associated with high current DC operation. The advantage is that a large amount of light can be absorbed by a large current without causing a loss of quality.

Prior art systems rely on pulse energization of follow-up cathode lamps by glow discharge. This includes: However, this prior art does not require a specially coupled discharge. The technique by which pulse energization can be performed is not obvious. For example, suddenly turn on (energized) ) It is common sense to expect that the gas jet caused by the discharge will blow away the discharge. . Also, the presence of the jet prior to the turn-on of the discharge indicates its presence during the electrical pulse. It is thought that this makes it impossible to cause a rapid discharge in the rapidly operating jet. There will be. Pulse operating mode (jet or discharge is turned on suddenly) Even if it is not possible to establish a This combined discharge operates in the well-known continuous mode by turning on the It is possible to establish it as

4. Compensation method for lamp intensity drift In conventional technology, absorbance is measured in the presence and absence of an absorber (absorbing phase). Requires knowledge of the light source signal in both. This is a cell that contains non-absorbing substances in the optical path. physically positioning the optical fiber to record its signal, and then moving said non-absorbing phase out of the optical path. In addition to physically removing the absorbing phase, the cell containing the absorbing phase is physically placed in the optical path to improve its reliability. This is commonly done by recording the number. This is because the intensity of the light source fluctuates over time. This is often done to compensate for This method also uses the spectrum It is also used to compensate for changes in the intensity of the light source depending on the wavelength during scanning. It will be done.

When using a pulsed atom source to supply absorbing atoms from a sample material records a signal before each pulse and indicates that the pulsed atom source is turned on. It is also possible to record the signal after the absorbing sample atoms are present in the optical path. It is possible to obtain these two signals by It has a composition. The general claims herein include: (a) during or after each pulse; Q) How to obtain these three signals before By making these two measurements for each pulse, physically between these measurements: It is possible to compensate for relatively rapid intensity changes over time of the light source. If you don't smoke The measurement of the acquired signal occurs just before turning on the sampling pulse (in microseconds). If done, the compensation can be done by methods that involve physical manipulation (even mechanical vibration methods). ), thereby increasing the lamp strength. Relatively rapid changes in temperature can be tolerated.

This pulsed method furthermore uses the same portion of the beam from the lamp for the two signals. This has the advantage that both can be observed by the same optical element. The double beam method is the same Sometimes different parts of the beam are observed, or the same part of the beam is observed in each beam. It is observed using different optical elements. Different parts of the beam are observed. If the parts are It is possible to demonstrate high accuracy. In addition, the same part of the beam may have different optical elements. When observed by This provides compensation for the error factors.

The claimed items are also not limited to the atomization of solid samples, but are This also applies to childization.

Another embodiment of this claim includes a pulsed absorbing atom source and a pulsed light source. By synchronizing, the optical measurement pulse of the non-absorbing phase is emitted just before the pulse of the absorbing source. and another non-absorbing phase optical measurement pulse occurs after pulse energization of the absorbing light source. It was made by sea urchin.

Temporarily separating the atomization process from the absorption measurement reduces the radiation noise from the absorption measurement. limiting and thus improving the detection limit.

Additionally, high-intensity light sources reduce front-end noise and improve detection limits. It is something.

5. Dynamic range control As already mentioned, a significant limitation of atomic absorption methods is the ability to make accurate measurements. Limited dynamic range (range of absorption and therefore concentration values) It is. The use of a pulsed source of absorbing atoms increases the dynamic range and changes in wavelength. or those that can be easily expanded without causing large losses in terms of time or samples. It is. This new method involves absorption.

When a continuous light source is used, multiple pulses are Many measurements can be taken. In addition, when a pulsed light source is used, the first absorption Select the light pulse delay time and pulse the lamp for the current absorption pulse. One measurement can be performed during the time period used to measure. that sun If we have some knowledge of a reasonable range of concentrations for the pull , you can selectively set the delay time before manipulating the sample.

In practice, the relationship between the delay time and the absorption occurring in the absorption pulse is determined by measurement. will be determined. This relationship has a large dynamic range over which concentrations can be accurately compared. used to establish That is, the delay time and the measured absorption amount are are also introduced into this relationship, covering a large dynamic range of concentrations. Obtain the effective absorbance (or parameter in some other units) for compensation be able to.

Analyte 16 is an existing multi-element AA measuring instrument are different in two fundamental aspects. First, it is required Analyze each sample completely for all elements before moving on to the next sample. commonplace A typical multi-element AA instrument first collects a group of samples, typically 50. , determine the single element contained in them all, and then determine the second element This will be analyzed by moving on to . Second, analyte 16 is a solid, undissolved substance. Analyte atom source t0 type non-heating atoma designed for sample analysis Designed for use with Isa. [Note: Conventional AA equipment uses a frame or uses a furnace atomizer, both of which are best suited for liquid phase analysis. It is something to do. Ko The analyzer 16 used with the atom source atomizer is a special The preferred average precision (0, 1%R5D), and the amount of sample is very small or ppm. Provides the ability to determine a wide range of concentrations down to compositional levels in the absence of It is something that Analyte 16AA-2 is also a problem with conventional AA equipment. It has good sensitivity to refractive elements such as B55ISTls and W. It is something that you have. Therefore, in experiments, X-ray fluorescence analysis or arc/spark Analyte 16AA as an alternative to or as a supplement to Park emission spectroscopy It is recommended to use a spectroscopic analyzer.

Analyte 16 is a saucer that can hold 16 follower cathode lamps. It is equipped with a kit. Some of these lamps can be multi-element light sources. I can do it. If the first element to be determined in a given sample is silver For example, the second element is iron, and the automatic operation is as follows.

The light source elements of the device are such that they accept light from the silver-followed cathode lamp. The light source emits excited light at a predetermined silver wavelength. Silver has been determined Later on, the optical system is driven to select the emission from the iron lamp and at the same time The nochromator is tuned to the iron wavelength and placed into operation. This is a complete sample This is done until it is analyzed. The time required for each measurement is 5 seconds or less per element. can be done. For samples, 10 elements are analyzed in 60 seconds and 20 elements are analyzed in 2 minutes. Can analyze elements.

Analyte 16 physically consists of three modules. First, optical modini The tool includes a lamp turret, monochromator, power supply, and microprocessor control. Contains rollers. The second module is an atom source atomizer. Third The module performs all the necessary controls and calculations for the meter and atomizer. I am using an IBM compatible personal computer.

Analyte 16 can also be used in conventional atomic ophthalmic atomizers (flame atomizers). ). In frame mode, analyte 16 is preferred Has almost the same performance as a sequential ICP (inductively coupled plasma) spectrometer It is something that However, analyte 16 has very little spectral interference. therefore, virtually all the originals developed in the past 25 years A particle absorption method can be used. Therefore, analyte 16 is sequential It is considered a valuable alternative to conventional ICP devices.

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Claims (1)

[Claims] All new devices, methods and other matters described in the specification.