Atomic absorption spectrometry (AAS) is also called atomic absorption spectrometry. The basic principle is that each element has its own characteristic spectral line. When the light with a certain characteristic wavelength emitted by the light source passes through the atomic vapor of the sample to be tested, the outer electrons in the atom will selectively absorb the characteristic spectral line emitted by the same element, thus weakening the incident light emitted by the light source. The degree of attenuation of characteristic spectral lines due to absorption can be expressed by absorbance, which is proportional to the content of elements to be measured in the sample. That is to say, the greater the concentration of ground atoms, the more light is absorbed. By measuring the absorbed light, the contents of metals and metalloid substances in the sample can be determined. For most metal elements, the * * * vibration line is the most sensitive of all spectral lines of the element, which is the fundamental reason why this method has good selectivity and can determine trace elements.

Many elements can be determined by atomic absorption spectrometry, with flame atomic absorption spectrometry reaching the order of 10 -9 g/mL and graphite furnace atomic absorption spectrometry reaching the order of 10-13 g/mL. Its hydride generator can detect the trace of eight volatile elements, such as mercury, arsenic, lead, selenium, tin, tellurium, antimony and germanium. Widely used in geology, metallurgy, machinery, chemical industry, agriculture, food, light industry, biomedicine, environmental protection, material science and other fields.

Second, the scope of application and application examples

Uncertainty of Determination of Gold in Geochemical Samples by (1) Graphite Furnace Atomic Absorption Spectrometry

Z-3000 series atomic absorption spectrometer, newly introduced on 20 13, uses two perfectly matched photomultiplier tubes as detectors to receive radiation with polarization planes parallel to and perpendicular to the magnetic field, respectively, and measure π and σ components of atomic absorption spectrum lines to realize background correction. This is an ideal scheme, which can ensure the background correction at the same wavelength, the same measurement space and the same time (real-time).

The stability of Z-3000 AAS is excellent, because the resistance of graphite tube on ordinary atomic absorption graphite furnace is very small, so it needs low voltage and high current. Usually, it takes 400~600 A current for graphite tubes to heat up to 3000℃. Z-3000 AAS graphite furnace adopts high resistance graphite tube, and the resistance of graphite is 30 ~ 33 mω. The graphite tube with high resistance can work under small heating current. When the graphite furnace is heated to 3000℃, the current used by the commercial power is only15 A. Because of the low heating current value, the built-in transformer is connected with the graphite furnace by solid cables, and the loss in each contact and cable is extremely small. When the graphite furnace is heated at the maximum power, the heating rate reaches 2600℃/s, which improves the sensitivity, gives excellent detection stability and reproducibility, reduces matrix interference, and greatly improves the service life of graphite tubes, from 80 ~ 400 times/only to 2000 ~ 4800 times/piece.

With automatic voice navigation, full information analysis software, multimedia operation course and video maintenance program, the instrument can be operated almost without any instruction manual. In the Laboratory of Geology and Mineral Resources System, we have a broad user base and geochemical sample testing methods.

(2) Simultaneous determination of As, Cd, Cu, Cr, Ni, Pb and Ti in sediments by electrothermal atomic absorption spectrometry.

MaríA(20 12) used ET AAS to simultaneously determine the total amount and distribution of heavy metals AS, Cd, Cu, Cr, Ni, Pb and Ti in sediments. This method uses 3×3 Box-Behnken design matrix. The improved BCR continuous extraction scheme and the matrix conditions of total distribution analysis were optimized, and the suitable atomization temperature and the mass of Pd (NO3)2 and Mg (NO3)2 were determined. Considering the simultaneous determination of all elements in the matrix, cadmium and titanium are atomized at 1700℃, and arsenic, copper, chromium, nickel and lead are atomized at 2 100℃, without using chemical improver, and the standard calibration curve is used for calibration. The detection limits of arsenic, cadmium, chromium, copper, nickel, lead and thallium are 36.5pg, 1.8pg, 6.5pg, 28pg, 34pg, 46.5pg, 48pg, 0.1μ g and 0.00 1 respectively. By analyzing three standard reference materials of sediments (the total content of NCS-4 in CRM DC 733 15 and LKSD and the effective part of BCR 70 1), the method was verified, and good accuracy was obtained (p = 0.05, and the high recovery rate of each element in each matrix was shown), except for the distribution matrix of total arsenic, in which the analyte was lost. The accuracy of this method is between 0.6% and 6%.

(3) Determination of arsenic, selenium and mercury in wastewater by cold atomic absorption spectrometry.

Aaron et al. used PinAAcle 900T spectrometer, FIAS 400 flow injection system and Winlab 32TM data platform to analyze and test the arsenic, selenium and mercury contents in wastewater. The results are shown in table 1.

Table 1 system sensitivity index

The analysis results show that the detection limit of this method can meet the requirements of EPA sanitary standard for drinking water in the United States, the detection limits of As and Se can also meet the standards of Canadian Environment Committee (CCME), and the detection ability of this method can meet the detection limit standards of Canadian soil analysis. However, if we want to meet the standard of marine mercury protection proposed by CCME, this method needs to be equipped with FIMS or larger injection loop.

(4)contra？ Determination of Fe, Ca, K, Na and Mg in Feldspar by 700 Flame Atomic Absorption Spectrometry

In 2006, the German company Jena introduced the high-resolution flame/graphite furnace integrated continuous light source atomic absorption spectrometer contrAA? 700, the instrument adopts high focal length short arc xenon lamp, stepped grating spectrometer (optical resolution 0.002nm, wavelength range 189 ~ 900 nm) and CCD linear array detector, which can measure 67 kinds of metal elements in the periodic table, and may obtain more spectral information.

Song et al. (20 10) use contrAA? The contents of iron, calcium, potassium, sodium and magnesium in feldspar were determined by 700 (figure 1 ~ figure 10).

Figure 1 Characteristic absorption peak of iron

Fig. 2 Three-dimensional test peak diagram of iron

Fig. 3 Characteristic absorption peak diagram of calcium

Characteristic absorption peak diagram of calcium.

Fig. 5 Characteristic absorption peak diagram of potassium

Fig. 6 Three-dimensional test peak diagram of potassium

Characteristic absorption peak diagram of sodium.

Fig. 8 sodium three-dimensional test peak diagram

Fig. 9 Characteristic absorption peak diagram of magnesium

Figure 10 Three-dimensional test peak diagram of magnesium

The results show that continuous light source atomic absorption spectrometry can quickly and accurately determine the contents of trace metal elements such as iron, calcium, potassium, sodium and magnesium in feldspar. Even if the content of the elements to be detected in the sample digestion solution is extremely low, the sensitivity can be improved by increasing the number of pixels, which is one of the unique characteristics of continuous light source atomic absorption spectrometry compared with traditional atomic absorption spectrometry. In addition, the content of some elements is too high (percentage content). If the sub-sensitive line is selected, the traditional atomic absorption often has the problems of spectral interference and insufficient lamp energy due to the limited resolution and light source intensity, and the error caused by dilution is inevitable. Because the continuous light source has extremely high resolution (2pm) and high enough luminous intensity, spectral lines with different sensitivities can be selected at will, which can effectively avoid spectral interference and completely eliminate dilution error.

(5) Determination of potassium, sodium, arsenic, tin, lead and zinc in iron ore raw materials by flame atomic absorption spectrometry.

Song et al. (20 10) use the continuous light source ContrAA? The content of various metal elements in iron ore raw materials is accurately and quickly determined by 700, and the resolution is two orders of magnitude higher than that of traditional atomic absorption spectrometry. In the determination of high concentration sodium metal, sub-sensitive line can be selected to accurately realize the analysis and determination, thus effectively avoiding the error caused by dilution.

After acid pretreatment, the sample was diluted in a certain proportion and used ContrAA? 700 flame atomic absorption spectrometry for measurement. The measurement conditions are as follows:

Scientific and technological achievements of foreign geology and mineral resources

Where the standard curve of Sn is:

Scientific and technological achievements of foreign geology and mineral resources

Three. sources of information

Zhang Hua, Wang, 2008. Evaluation of uncertainty in determination of geochemical samples by graphite furnace atomic absorption spectrometry. Geology of mineral deposits, 27: 9 1 ~ 95.

Www.analytik-jena.com.cn/ Song Chunming et al. Jena Analytical Instruments AG, 20 10.

Aaron Hyman. Determination of As, Se and Hg in Water by Hydride Generation/Cold Atomic Absorption Spectrometry

Maria a? géne sis carrillo lvarez。 Simultaneous determination of arsenic, cadmium, copper, chromium, nickel, lead and thallium in total digested sediment samples and effective parts by electrothermal atomization atomic absorption spectrometry. Taranta, 97( 15):505~5 12.