Interference effects in atomic launch spectra analysis can result in systemic or accidental errors in sample measurements. The mechanisms derived from the disturbance phenomenon can be divided into spectral and non-spectral interference, which refers to the indistinguishability of radiation signals from signals and jammers in the line of analysis of the element to be detected; non-spectral spectral typologies include physical, chemical and ionizing interference。
I. Spectra interference
Atom-launched spectrometers work, with a high energy intensity that stimulates the light source, creating 100,000-10 million spectral lines in the 200-1000 nm wavelength range, with an average of 100 spectral lines distributed at 0. 1 mm width, so that almost every element's analytical line is subject to varying degrees of spectral interference. When icp spectrometers are used, greater spectral overlap interference than other light sources becomes the main disturbance in icp-aes。
Spectrum interference can be divided into spectral overlapping and background disturbances。
1. Spectrum overlapping interference
It refers to a spectral overlap or partial overlap on the analytical line of the measured element by another element, in two cases:
(1) direct overlap of spectrum lines, i. E. Complete overlap of the jamming lines with the analytical lines。
At this point, correction can be made using the intervention factor method, which is the ratio of the increase in the concentration of the analytical element to the concentration of the interference element。
If the cr element in the geological sample is determined, the presence of a large number of fe is disturbed when measured on the cr analysis line 205. 552 nm, and if the mass concentration of fe is 1000 mg/l increases cr's mass concentration by 0. 2 mg/l, the fe's interference factor k for cr is:
The measured concentration at interference with the analysis of the elements is the apparent concentration cs, which is the true concentration ct after correction with the interference factor:
Ct=cs-kcd
In formula, the cd is the concentration of interference elements。
The following should be satisfied using the interference coefficient method:
The concentration of the interference element shall be known and shall remain constant within the measured element analysis concentration。
2 the interference factor k is associated with the spectrometer's resolution capacity, and the k values are not the same using different instruments, and the k values in the literature are used only as a reference, most of which should be self-measured。
In the icp spectroscopy analysis, the disturbance wavelengths of common element analysis lines and common element interference factors can be found in the icp spectroscopy analysis monograph。
(2) complex spectrum overlap analysis lines and two or more jamming lines overlap or partially overlap. At this point, if the interference coefficient method is used, the error result is obtained, so k is not a constant and a multispectral alignment process is used to correct it。
In modern atomic launch spectrometers, the application of high-resolution technology has reduced spectral interference, in particular the widespread application of the meso-step and holographic spectrometers, significantly reduced fragmentation, increased chromatography and effectively eliminated and reduced spectral interference。
Background interference
It refers to interference resulting from the formation of a series of series of spectra superheaves on the analytical line. Background interference is divided into four scenarios, as shown in the figure。
There are several cases of spectral background disturbance
(a) simple smooth spectra background; (b) slope background; (c) curved background; (d) complex structural background
(1) when a simple smooth spectra background analysis line peak is superimposed on a smooth background, it moves up in parallel, using a single point correction from the peak, i. E. The value of the background strength is deducted from the peak strength of the underlying background:
Ia=iab=icb
(2) an analysis of the background strength of the slope background is gradual with the wavelength, but the change is linear and can be corrected by two points from the peak, i. E., by measuring the background strength of the two points at an equal distance on both sides of the spectral peak, taking their averages and then deducting the background average from the peak strength of the context:
(3) the curved background analysis line is located on the side of the high-strength spectra of the element with which it coexists and forms the slope background of the gradient, which, if the line is of greater intensity, can still be calibrated at two points above the peak of the linear slope background, and if the line of analysis is of lower intensity, the error of the law correction is greater and gives incorrect measurements. For this spectral background correction, the correction is completed by using the blank background correction method, i. E. The spectral strength corresponding to the blank in a solution without the element to be detected, and by subtracting the spectral strength (observed strength) measured by the element to be detected。
(4) the complex structural background, which is a spectral background, is usually a mixture of molecular spectrospectral bands or spectral lines. A blank solution correction is most appropriate for this context。
The presence of background disturbances affects the accuracy of the results of the analysis and should be deducted, but the deduction applied introduces additional errors and should therefore minimize or inhibit the background depending on the reasons given in the context, although it would be preferable to opt for a non-disrupting analytical line before spectrometry。
Ii. Non-spectral interference
In atomic launch spectral analysis, non-spectral interference involves physical, chemical and ionizing interference。
1. Physical interference
Analysis of the physical properties of the test fluid, such as differences in viscosity, density and surface tension, which affect the efficiency of the icp fogging, causes changes in spectral strength, or physical or physical interference, which are divided into acid and salinity effects:
(1) the acid effects are analysed by the icp and the sample is made of a sample solution by acid solution, with effects on spectral strength due to the type and concentration of acid. The effect of inorganic acid on spectral strength is usually significantly reduced with increased acidity, as follows:
The acid effect is expressed as the ratio between the spectral strength at the time the acid exists and the spectral strength at the time the acid exists (deional water solution)。
(2) salt effects shall increase the sample concentration (increased salinity) and their viscosity, surface tension, etc., will increase, thereby affecting the input sample, the mistization efficiency and the reduced transmission of aerosols, and thus the reduction in the spectral strength of the analytical line。
The underlying method of removing physical interference is the use of matrix matching, i. E. Maintaining the same acidity and salinity levels in standard and analytical sample solutions and blank solutions。
2. Chemical interference
Chemical interference, also known as the “solvent evaporation effect”, is the pervasive interference effect of atomic absorption and flame light. If ca is measured, the phosphate root or al would cause interference, at which point the release agent should be added to reduce the chemical disturbance, which has a small impact in the icp spectra but still exists。
Ionizing interference
For ionable elements, volatilizing into flames, with the occurrence of ionizing, increasing electron density, resulting in an ionizing balance m
M++e - distortion in the direction of neutral atoms also reduces the spectral strength, so that ionizing interference is severe in flame light. Ionizing interference is much weaker in icp spectra analysis, but still exists。
The effect of ionizing interference on the spectra of sodium elements is as follows:
(1) ionized interference with the ion line in na reduces the spectral strength and increases the spectral strength in na atom。
(2) ionising interference of na with the ca (422. 673nm) spectral line can be reduced at an observation height of up to 15 mm from the torch and up to 1700 ug/ml from the na atom. In general, however, increased observational heights and increased ionizing interference may be due to lower spectral intensity due to lower temperatures of the icp torches at higher observed altitudes。
To eliminate ionizing interference, the matrix matching method may be used, or the standard addition method may be used for quantitative analysis。
Iii. The matrix effect
The matrix effect is the effect on the analysis of the spectral strength and the spectral background of changes in the main components of the sample, which is also an interference effect in spectral analysis。
The matrix effect is essentially the sum of the various interference effects. The matrix effect is mainly non-spectral interference, but also includes background disturbances in spectral interference and trigger disturbances。
Influencing interference is a phenomenon that causes changes in the light source temperature, electron density, atoms and ion distribution in the light source as a result of changes in the sample composition, leading to changes in the spectral strength and spectral background。
Cognisant matrix effects are the result of a combination of multiple interference effects。
The matrix effects are associated with the type, content (concentration) of the jamming elements and are also influenced by icp spectroscopy conditions such as high frequency (hf) power, airborne flow, and observational altitude。
The matrix effect can be expressed by the ratio b of the spectral strength of the line of analysis to the ib of the spectral strength of the line of analysis if the (gaps) effect exists。
B = ib/ib
When b > 1, the effect of the matrix is enhanced, b
In order to reduce the effects of matrix effects in spectral analysis, the following methods could be used:
(1) use of robustness (robust) analytical conditions or enhanced conditions. In the icp spectra analysis, high hf power, low load flow, moderate observation altitude should be used to inhibit the matrix effect。
(2) when the standard solution series is formulated using the matrix matching method, the same amount of base composition as the sample solution is to be added to match the main components of the standard solution series with the analysis sample solution。
(3) the standard addition method may be used when the matrix matching method is used, where the inclusion of the matrix composition is 1. 2 orders of magnitude greater than the pureness of the analysis of the sample and sometimes difficult to obtain, without the use of the matrix material。
(4) chemical separation is followed by icp spectra analysis of the sample solution after separation of the matrix composition。
