Inductively coupled plasma spectroscopy common problems and techniques - Database & Sql Blog Articles

Photocoupler

Inductively coupled plasma atomic emission spectrometry

ICP-AES

It is a spectral analysis method with an inductively coupled plasma moment as an excitation source. It has the advantages of high accuracy, high precision, low detection limit, fast measurement, wide linear range, and simultaneous determination of various elements. It has been widely used abroad. Determination of dozens of elements in environmental samples and samples of rocks, minerals, metals, etc. Today, we bring you

ICP-AES

Analysis common

12

Fault problems and solutions!

1. Factors affecting plasma temperature are:

1 carrier gas flow rate: the flow rate increases, and the temperature of the central part decreases;

2 carrier gas pressure: the excitation temperature increases as the carrier gas pressure decreases;

3 frequency and input power: the excitation temperature increases with the increase of power, which is approximately linear. When other conditions are the same, the frequency is increased and the discharge temperature is lowered.

4 Effect of the third element: The plasma of the release agent with a low ionization potential will increase the electron temperature.

2. Elimination and suppression of ionization interference:

Interference caused by the ionization of atoms in the vapor phase of a flame or plasma. It reduces the number of neutral atoms in the analytical element in the flame, thus reducing the analytical signal. Excessive ionizing elements are added to the standard and analytical samples to stabilize the free electron concentration in the flame or plasma at a relatively high level, thereby inhibiting or eliminating ionization of the analytical elements. In addition, the higher the temperature, the greater the degree of ionization, so lowering the temperature also reduces ionization interference.

3. What are the main effects of the acidity of the reagent on the ICP-AES method?

The rate of increase and the intensity of the elements in the elements are lower than that of the aqueous solution; as the acidity increases, the intensity of the line decreases significantly; the effects of various inorganic acids are not the same, increasing in the following order:

HCl HNO3 HClO4 H3PO4 H2SO4

The change in line intensity is proportional to the change in the rate of increase. So at

ICP

In testing, it should be avoided as much as possible

H3PO4 H2SO4

The slit correction is performed as a medium.

4. The main types of spectral interference in the ICP-AES method:

Spectral line interference; interference of the spectral line to the analysis line; interference of the continuous background to the analysis line; interference caused by stray light; matrix interference; suppression of interference. For spectral line interference, it is generally preferred to replace the spectral line. The continuous background interference is generally eliminated by the method of the buckle background of the instrument. The matrix interference is generally the basic matrix or the standard addition method, and the suppression interference is generally separated or matrix.

5. Correction of sensitivity drift in ICP-AES analysis:

During the measurement process, the gas pressure change will affect the atomization efficiency and the distribution of the ground state atoms; in addition, capillary blockage, poor waste liquid discharge, will affect the solution lift and atomization efficiency; and voltage changes and even ambient temperature, etc. Many factors will cause the sensitivity to drift, and the calibration method can be measured every time.

10

Each sample is measured for a quality control sample close to the sample composition, and the standardized time interval is appropriately shortened according to the age of the instrument used.

6. How to avoid mutual contamination between samples in ICP analysis?

When measuring, do not measure the samples with large concentration difference in sequence. The samples with similar concentrations can be measured together. Between the samples, rinse with distilled water. When entering the standard sample test standard curve, it should be from low to high. Injection.

7. In the ICP-AES method, the acid used to decompose the sample must meet the following conditions:

As far as possible, the various elements are rapidly and completely decomposed; the amount of elements to be tested is negligible; when the sample is decomposed, the element to be tested should not be lost; no insoluble matter is formed between the elements to be tested; Small; does not damage the atomizer, torch, etc. Hydrofluoric acid can quickly damage the atomizer, the mist chamber and the torch.

8. In the ICP-AES method, why should we pay special attention to the configuration of the standard solution?

Incorrect configuration methods will lead to system deviation; media and acidity will not be suitable, and precipitation and turbidity will occur; improper grouping of elements will cause spectral interference between elements; reagents and solvents will not be pure enough, which will cause blank value increase and detection limit. The variation and the error increase.

9. Precautions for preparing multi-element stock standard solution for ICP analysis:

The solvent is made of high-purity acid or ultra-pure acid; using re-distilled ion-exchanged water; using spectrally pure, high-purity or reference material; some elemental elements are divided into several groups to avoid spectral interference or precipitation. For example, when measuring silicon, it is necessary to measure silicon separately.

10. What are the special requirements when using organic reagents for ICP analysis?

The high frequency power should generally be higher than the aqueous solution sample; the cooling gas flow rate should be increased, the carrier gas flow rate should be reduced, and the higher flow auxiliary gas should be introduced at the same time; there are some special requirements for the structure and installation of the torch tube; The organic solvent of the structure is used as a diluent.

11. What is the diluent? What are the requirements for the diluent used in the ICP-AES method?

Generally, samples with high viscosity are difficult to inject by pneumatic atomization. The low viscosity organic solvent is often used to dilute the sample. This organic solvent is called a diluent. The requirements are: 1 low viscosity; 2 molecules with fewer carbon atoms; 3 with moderate volatility; 4 no or less toxic gases; 5 allow higher injection volume without plasma Extinguished; 6 less carbon deposits at the torch nozzle.

12. What are the effects of thinner on ICP analysis?

The viscosity of the diluent affects the atomization injection rate and the rate; the density, viscosity and surface tension affect the initial tribute to the formation of the droplet; the boiling point affects the evaporation and entry of the droplet

ICP

The amount of organic solvent evaporation in the channel, thus affecting

ICP

Stability.