AA-1800C atomic absorption spectrophotometer in cement quality testing - Database & Sql Blog Articles

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AA-1800C

Application of Atomic Absorption Spectrophotometer in Cement Quality Testing

Key words: atomic absorption spectrophotometer; cement quality testing;

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1

Principle of atomic absorption spectrophotometer

Atomic absorption spectrophotometer

It is designed according to Beer's law. Beer's law refers to the fact that when the incident light with a certain wavelength and intensity passes through a fixed solution of optical path length, the absorbance is proportional to the solution concentration, but in fact the incident light provided by the instrument is actually The light band consisting of a narrow wavelength range, because the material absorbs different wavelengths of light, it causes the deviation of the contrast ear law, and produces an error.

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On the other hand, since the basic assumption of Beer's law is that the absorbing particles are independent and have no interaction with each other, in fact, the interaction of the absorbing particles increases as the concentration increases, causing deviation from the ear's law. An error has occurred. To eliminate or reduce the method errors caused by the above two methods, it is necessary to be as monochromatic as possible and the concentration of the sample to be tested should be as low as possible.

2

, sample preparation methods and standard solutions, as well as selection of reagents and containers for experiments

Due to use

atom

Absorption spectrophotometer

The determination of some quality indicators in cement requires stricter preparation of sample solution, and the sample processing time is relatively long, while the cement quality inspection department and manufacturers require that the measurement speed be as fast as possible, so the author based on long-term work experience and cement sample specific In the case, a method for the treatment of cement atomic absorption samples was developed and proved to be practical. This method is practical. The specific method is as follows:

0.12g

~

0.14g

Specimen, accurate to

0.0001g

, placed in the silver enamel, joined

3g

Sodium hydroxide, in

750~C

~

780oC

Melting at high temperatures

10min

. Take it out slightly, it will be released.

100ml

In a beaker boiling near water, cover the watch glass and heat it on the electric furnace. After the frit is completely leached, remove the crucible and add it once under stirring.

35ml (1 1)

Hydrochloric acid solution with hot hydrochloric acid

(1 9)

Wash the crucible and lid and heat the solution to boiling. Cool down, then move people

250ml

In a volumetric flask, dilute to the mark with water and shake well. draw

5.00ml

Transfer the measured solution into

15Oral

In the volumetric flask, join

18mlHC1 (1 1)

Solution,

3ml (50g/1) SrC1

: The solution is diluted to the mark and shaken. Also configure the reagent blank solution. The method takes only one hour from sample processing to the results. If the same element is determined in batches, the superiority of the method is more pronounced. The standard solution used should be matched to the composition of the sample solution as much as possible to eliminate systemic interference. In the measurement process, the acidity has a great influence on the measurement results, so the acidity of the standard solution and the sample to be tested should be kept as consistent as possible. The amount of addition should be strictly controlled when the sample is treated with acid. The acidity of the sample solution is close to the acidity of the standard solution, reducing the interference of acidity. Since the atomic absorption spectrometer is a microanalytical method, the pure water used in the sample preparation process must be distilled water or deionized water, and the corresponding blank value should be made. The chemical reagent used to treat the sample is preferably made of excellent grade pure hydroxide. Sodium, hydrochloric acid and barium chloride. The preparation of the magnesium oxide standard solution should use a spectrally pure reference reagent to prevent errors due to insufficient purity of the experimental water and the reagents used. The use of electronic balances, pipettes, and volumetric flasks in the experiment must be used separately to prevent cross-contamination from affecting the measurement results. Standard equipment should pass the metrological verification before it can be used to ensure the accuracy of the measured data. In the process of measuring data, the accuracy from the preparation of standard solutions to the use of various containers is affected by laboratory environmental temperature building materials standardization and quality management. The calibration temperature of these glass instruments is generally

20

°C, and the actual temperature in our lab is usually not

2O

°C, will cause some errors, so try to keep the temperature of the laboratory at

20

°C or their calibration can be properly calibrated when using these glassware. On the other hand, in the measurement process, the temperature of the sample liquid containing the element ions to be tested also affects the measurement result, and the temperature of the sample liquid is high, and the result of the measurement also produces a positive error. Therefore, the temperature of the solution should be kept at room temperature before it can be determined.

3

Optimal measurement parameters

AA-1800C

The type of atomic absorption spectrophotometer has a very large influence on the background of different types of samples. Therefore, in actual work, it is necessary to establish a set of samples from sample preparation, standard solution preparation to atomic absorption spectroscopy according to the characteristics of the industry samples. The method determines the optimal experimental conditions for the final result.

3.1

Selection of absorption line When the ground state atoms of the elements in the sample are absorbed, a number of lines can be generated. Choosing the appropriate absorption line in actual work should be determined by experiment depending on the specific situation. The test method is to scan the emission spectrum of the hollow cathode lamp, to find out which of the available lines, and then to inhale the test solution, to observe the absorption of these lines, and to select the line that is undisturbed and has a moderate absorption value. Analysis line. The strongest absorption line is generally used for low concentration elemental analysis.

3.2

Spectral passband selection

Atomic absorption spectrophotometer

In other words, only the slit can change the pass band. The principle of selecting the slit width is to select a wider slit to reduce the noise of the detector when the monochromator can avoid the nearest non-resonant line, thereby improving the instrument. The signal-to-noise ratio ensures the stability of the measurement. However, the use of wider slits also results in reduced sensitivity. The experimental method for determining the appropriate slit is to suck the test solution into the flame, adjust the slit width, and measure the absorbance at different slit widths. When the absorbance is stable, the slit width at this time is most suitable.

3.3

Selection of lamp current The emission characteristics of a hollow cathode lamp depend on the operating current, which has an important influence on achieving optimum absorption sensitivity. If the lamp current is too large, although a strong emission intensity can be obtained and the stability of the measurement is improved, the life of the lamp is shortened due to the rapid gas consumption in the lamp. If the lamp current is small, the sensitivity can be improved, but the lamp current is too small. The hollow cathode lamp will have unstable emission intensity and low signal-to-noise ratio. Therefore, when choosing the lamp current, both sensitivity and stability must be considered. The choice of current is determined experimentally, that is, the hollow cathode lamp is capable of stable discharge and a smaller lamp current is used with a suitable signal-to-noise ratio.

3.4

Selection of atomization conditions The originalization of the sample determines the sensitivity, accuracy, and even interference of the elemental measurement. For premixed burners, it uses a combustion gas and atomizer to atomize the test solution. The amount of atomization of the test solution and the shape of the atomizer. The position of the dispersing ball and the pressure and flow rate of the combustion gas are directly related. Since the energy required for the atomization of different elements is different, the temperature of the flame is also different, so the appropriate values ​​of the combustion gas, the combustion gas and the burner height should be determined experimentally to obtain the highest measurement sensitivity. The specific test method is to absorb a certain concentration of the standard solution under the condition that other conditions are fixed, and change the gas flow rate and the absorption height respectively, and determine the peak value to determine the optimal parameter. The atomic absorption spectrophotometer should take into account the sensitivity of the analysis and the stability of the measurement when selecting the measurement parameters.

4

Chemical interference

Atomic absorption spectrometry

(

Atomic absorption spectrophotometer

There are various kinds of interferences, in which chemical interference is the main interference. The nature of chemical interference is mainly to form a strong chemical bond between the interferent and the interfered object, which is difficult to separate under normal conditions, so that the absorption is low. In actual work, how to judge the interference, in addition to the general information introduction, in the specific analysis can also use the dilution method for chemical interference detection, that is, the sample solution is diluted

2

~

5

Times, and then measured. The measurement results are judged by the mathematical statistics method. If the measurement results are consistent with the pre-dilution results, there is no significant interference. Otherwise, interference can be considered. For most elements, the interference can be reduced after dilution, as for the size of the interference. The standard addition method recovery test should be used to conclude that the smaller the recovery rate, the greater the interference. When there is chemical interference, consideration should be given to taking some measures to eliminate interference in the measurement method. A simple method is generally used: adding a release agent or protecting a complexing agent, such as adding an aluminum dichloride solution.

;

Sometimes, interference, ion exchange, precipitation, etc. can be used to pre-separate the interfering substances, or the standard addition method can be used to automatically compensate the interference of the trace elements, thereby eliminating the interference. Atomic absorption spectrometry

(

Atomic absorption spectrophotometer

Determination of various chemical indicators in cement, eliminating the errors caused by artificial measurement and titration operations, as long as the various experimental conditions and sample processing methods of the instrument are selected, the measurement results are accurate and fast, for cement quality indicators. Determination is a very good method.

Key words: atomic absorption spectrophotometer; cement quality testing;

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