Atomic emission spectrometry (AES) is an optical analysis method based on measuring the wavelength and intensity of radiation during energy level transition in matter. Inductively coupled plasma atomic emission spectrometry (ICP-AES); ); Sometimes called ICP-OES, it comes from optical emission spectrometry, which distinguishes ICP light sources with ion lines as the main source from other light sources with atomic lines as the main source). It is an atomic emission spectrometry analysis technology with inductively coupled plasma as excitation light source. This technology began with the appearance of ICP in 1970s, and it is the fastest developing and most widely used atomic emission spectrometry technology so far. The principle is that the sample is completely decomposed by the high temperature generated by argon plasma to form excited atoms and ions. Due to the instability of excited atoms and ions, the outer electrons will jump from excited state to low energy level, thus emitting characteristic spectral lines. After being split by a light splitting system such as a grating, the intensity of a specific wavelength is detected by a detector, so as to determine the content of the elements to be detected in the sample.
Inductively coupled plasma (ICP) is a spectral light source with good evaporation-atomization-excitation-ionization performance. A high-frequency electromagnetic field is generated by a high-frequency current passing through an induction coil, so that the working gas forms a plasma, showing a flame-like discharge (plasma torch), reaching a high temperature of10000 K. Moreover, due to the annular structure of the plasma torch, it is beneficial for the sample to be injected from the central channel of the plasma, and the flame stability is maintained. When the flow rate of carrier gas is low (< 1 L/min), ICP can be penetrated, and the sample can stay in the central channel for 2 ~ 3 ms, completely evaporate and atomize. The high temperature of the central channel of ICP ring structure is higher than any flame or arc spark, which is the best excitation temperature of atoms and ions. The analyte is indirectly heated in the central channel, which has little effect on the discharge characteristics of ICP. ICP light source is a thin light source with small self-absorption, no electrode discharge and no electrode pollution. These characteristics make ICP light source have excellent analytical performance, which meets the requirements of an ideal analytical method. Therefore, ICP-AES analysis method has the following excellent analysis characteristics:
1)ICP-AES method is the simultaneous determination of multiple elements at first. No matter multi-channel direct reading or single-channel scanning instrument, a large number of elements (30 ~ 50 or even more) can be determined simultaneously in the same sample solution. There are 78 analytical elements reported in the literature, that is, all elements existing in nature except inert gases such as he, Ne, Ar, Kr and Xe have been reported by ICP-AES.
2)ICP has high evaporation, atomization and excitation ability. Due to the excellent characteristics of plasma light source, the chemical interference and matrix interference of classical spectral analysis method can be avoided, so the interference level is relatively low. The high temperature of the plasma torch can atomize and excite the elements that are difficult to excite in general chemical flame, which is beneficial to the determination of the elements that are difficult to excite. In addition, refractory metal oxides are not easy to form in Ar atmosphere, which makes the matrix effect and the influence of * * * elements not obvious. Moreover, the self-absorption phenomenon of ICP light source is very low, and the linear range of calibration curve can reach 5 ~ 6 orders of magnitude. In most cases, there is a simple linear relationship between the element concentration and the measured signal. Low concentration components (< 1 mg/L) and high concentration components (hundreds or thousands of mg/L) can be measured simultaneously. It is a very valuable analytical characteristic to give full play to the simultaneous determination of multi-elements by ICP-AES.
3)ICP-AES method has the stability and measurement accuracy of solution sampling analysis method (RSD < 1%). Its analytical accuracy can be comparable to that of wet chemical method. And the detection limit is very good, and the detection limit of many elements is <1mg/l.
The latest development of related instruments is as follows:
(1)Spectroblue ICP-OES- full spectrum direct reading plasma emission spectrometer
Spectroblue ICP-OES- full-spectrum direct-reading plasma emission spectrometer (Spike Company, Germany) is characterized in that the Paschen-Runge optical system with a focal length of 750 mm is adopted to collect the full-spectrum data of the first-order spectrum in the range of130 nm to 770 nm; Constant resolution (3pm pixel resolution) can be maintained in the wavelength range of 130 nm to 340 nm, and the pixel resolution above 340 nm is 6 pm; ; 15 linear CCD detector; UV-PLUS gas purification technology (argon is purified in a closed argon-filled optical room and circulated through a purification tube with a small diaphragm pump); OPI-AIR interface, cancel the external water cooling system; Two observation modes (axial or radial) are provided. Plasma interface (OPI) is adopted in radial observation: argon gas is introduced in the tangential direction of the interface, and then blown out from the outlet, which directly penetrates the plasma and blows off the tail flame to eliminate the interference of the matrix.
(2)Optima 7300 V spectrometer
Optima 7300 V is a desktop vertical torch inductively coupled plasma emission spectrometer (Figure 1), which can eliminate carbon deposition and minimize maintenance requirements. The radial observation function of the instrument can ensure fast and stable operation, and it is specially designed to meet the unique challenges of oil sample analysis or geological and metallurgical applications.
There are two models of Optima 7300 V series: ①Optima 7300 V engine oil version, which is suitable for engine oil analysis; ②Optima 7300 V HF version, suitable for geochemistry and high solid phase analysis.
Figure 1 Optima 7300V spectrometer
(3) Flat plasma technology
Optima 8x00 series ICP-AES is characterized by: reducing argon consumption, and flat plasma technology only needs 8 L/min plasma gas flow at any RF power; The extension of the far ultraviolet region (120nm) is beneficial to the selection of low background spectral lines and the analysis of nonmetallic elements (such as C, S, N, Cl, Br, I). Patented plasma two-way observation-using air to cut gas to eliminate cold tail flame and interference; High concentration and low concentration elements can be measured in the same way. Axial observation provides the lowest detection limit, and the observation height of radial observation is variable, which can expand the working range and eliminate ionization effect.
(4) Agilent 7 10 series ICP-OES-CCI.
Agilent 7 10 series ICP-OES-CCI has cold cone interface technology, two-way observation mode and CCD detector.
Second, the scope of application and application examples
(A) in the analysis of geological samples.
The instrument detection limit of ICP-AES is 0. 1 ~ 100 ng/ml. There are many spectral lines with different sensitivities in general elements, and the dynamic linear range is about 4 ~ 6 orders of magnitude. Therefore, ICP-AES is very suitable for the requirements of complex matrix, large element content range, many elements to be measured and large sample batch in geological analysis samples, and is suitable for the analysis of major, medium and trace elements in geological samples. At present, ICP-AES technology has been widely used in the field of geological analysis and has become an important multi-element analysis method in modern geological and mineral analysis laboratories.
Typical applications of ICP-AES in geological sample analysis are as follows.
1) is used to determine more than 20 elements such as barium, beryllium, calcium, cobalt, chromium, copper, iron, potassium, lithium, magnesium, manganese, sodium, nickel, lead, strontium, thorium, titanium, vanadium, zinc and scandium in rocks, soils and river sediments, especially suitable for the determination of large quantities of samples.
2) After lithium metaborate is melted, the main elements include silicon (silicon dioxide, alumina, calcium oxide, magnesium oxide, K2O, sodium oxide, titanium dioxide, manganese oxide and phosphorus pentoxide) and trace elements such as zirconium, strontium and barium. ) can be directly determined, and the precision required by full analysis can be achieved. Instead of complicated chemical analysis, the percentage and quality can be controlled between 99.3% and 65438+.
3) Determination of major and minor elements in mineral ore samples, some trace elements can only be determined after separation and enrichment. Such as hydrochloric acid, nitric acid, hydrofluoric acid, perchloric acid, pyrite, sphalerite, cobalt-nickel polymetallic ore, etc., and directly determine Al, Fe, Cu, Pb, Zn, Ca, Mg, K, Na, Sb, Mn, Ti, Li, Cd, Co, Ni, V, Ag and other 18 elements by ICP-AES.
4) After separation and enrichment by alkali fusion-cation resin or P507 resin, the contents of trace ultra-trace 15 rare earth elements in various geological samples were determined.
5) Direct determination of main cations (calcium, magnesium, potassium, sodium, etc.). ) and metasilicic acid and B in natural water samples. Determination of dozens of trace elements in natural water after precipitation, separation and enrichment of iron hydroxide.
6) Determination of boron, sulfur and other elements by mixed phosphoric acid solution -ICP-AES.
7) Determination of trace element titanium in geological samples by -ICP-AES after separation and enrichment with polyurethane foam.
ICP-AES technology is mainly used for the analysis of metallic elements, and the sensitivity of nonmetallic elements is poor, but it can well analyze high-content elements, such As P, S, B (if B is soluble in acid, it needs phosphoric acid protection), As, Se and so on. Some types of instruments can even analyze elements such as Cl, Br and I. Generally, the sensitive line of nonmetallic elements is in the far ultraviolet region, and there is an obvious oxygen molecular absorption band below 200 nm. For the wavelength below 190 nm, vacuum or inert gas should be used to prevent the absorption of oxygen molecules.
(2) Analysis of rare earth elements
Ma Lin et al. quickly determined Ba, Zr, Th, U, La, Ce, Eu, Hf, Gd and other elements in 1mol/L FeCl3 filtrate by ICP-IES. In the process of liquid-liquid extraction, iron was selectively and quantitatively extracted with ether, and the decontamination factor was 65000. The detection limits of U, Th, Ba and Zr in high iron ion concentration solution are 1 ~ 24 ng/ml, and the relative standard deviation is 0.9% ~ 4.6%. This method has been used to deal with radioactive materials.
(3) Analysis of trace elements in soil
PerkinElmer's ICP-OES can analyze all metal elements in the periodic table, and the detection limit is below 1× 10-9. At the same time, most nonmetallic elements, such as arsenic, selenium, phosphorus, sulfur, silicon, tellurium and so on. The detection limit is lower than 10× 10-9. If hydride generators are used together, the detection limit of these nonmetals can be increased by more than 10 times.
Praveen Sarojam et al. (20 10) used microwave digestion and other pretreatment techniques to detect soil samples with OptimaTM 7300 DV ICP-OES, and achieved good results.
Three. sources of information
/catalog/family/id/optima+8x00+ICP+OES+spectrometer? UTM _ media = LinkToEloquaGenericLanding
Marin A, Joaquin C, Karin P et al., 2009. Determination of Rare Earth Elements, Uranium, Thorium, Barium and Zirconium in Simulated Hydrogeological Leachate by ICP-AES after Matrix Solvent Extraction. Journal of Rare Earth, 27 (1):123 ~127
Praveen S, trace m. Characterization of soil by Optima 7300 DV ICP-OES, PerkinElmer, Inc.