Hydride Generation Atomic Fluorescence Analyzer System

Abstract

The present invention discloses a hydride generation atomic fluorescence analysis system, including a sampling system, a gas-liquid separator, an atomizer and an inert gas generating device, wherein a reduction reaction is performed in the gas-liquid separator to generate a mixed gas, and the mixed gas enters the atomizer through a carrier gas, and the atomizer includes an inner tube and an outer tube sleeved on the outer side of the inner tube, and is characterized in that a gas outlet pipe of the gas-liquid separator is connected to the outer tube, and the inert gas generating device is connected to the inner tube. The present invention utilizes the original quartz furnace to implement the outer tube sampling, the hydrogen flame is very easy to ignite, and the detection sensitivity is improved, which is an innovation of the atomic fluorescence analysis technology.

Description

[0001] This application is a divisional application. The parent application number is 201910227203.7, the application date is March 25, 2019, the priority number is 201811270818.X, the priority date is October 29, 2018, and the name of the invention is: Atomic fluorescence analysis method with external tube injection. Technical Field

[0002] The invention belongs to the field of analytical chemistry and relates to atomic fluorescence analysis. It changes the traditional injection mode and corresponding technology of the atomizer in atomic fluorescence analysis, and specifically relates to the improvement of the injection method in the original atomic fluorescence analysis method. Background Art

[0003] Atomic fluorescence analysis has been widely used in the determination of trace elements such as As, Sb, Bi, Hg, and Se. The basic principle is that the ions of the element to be measured react with a strong reducing agent (usually potassium borohydride or sodium borohydride) in an acidic medium (usually hydrochloric acid) to be reduced to gaseous hydrides or atoms, while producing a large amount of hydrogen. The hydride molecules dissociate into ground state atoms in a high-temperature hydrogen flame and are excited to a high-energy state by the radiation of a specific frequency of the excitation light source. Since the high energy level is extremely unstable, the excited state atoms emit fluorescence of a characteristic wavelength in the form of light radiation during the de-excitation process. The fluorescence intensity is related to the concentration of the element to be measured, and the concentration of the element to be measured is obtained by measuring the intensity of the fluorescence signal through a detector (usually a photomultiplier tube).

[0004] The atomic fluorescence analysis device (also called atomic fluorescence instrument, atomic fluorescence photometer) designed according to the above principle mainly includes an infusion system, a steam generation system (or reactor), an atomizer, an excitation light source and a detection system. The test solution and the reducing agent are transmitted through the infusion system and carried by the carrier liquid (also called carrier fluid) into the reactor for chemical reaction to generate gaseous hydride molecules and hydrogen, which enter the atomizer under the carrier gas (usually argon).

[0005] The atomization of hydrides relies on the high temperature of the hydrogen flame, and the atomization process is completed using a quartz furnace in the atomizer. Figure 1 As shown, the quartz furnace is usually in the form of a sleeve tube, including a central tube (inner tube) and an outer tube. The carrier gas (argon gas) carries hydrides and hydrogen and is led out from the central tube deep inside the quartz furnace. The shielding gas (argon gas) is input from the outer tube. The hydrides led out of the central tube are atomized in the ignited hydrogen flame (shielding gas argon gas protection). Usually, a small flow of carrier gas (Ar gas) is used to carry the hydrogen flame to obtain a stable and slender hydrogen flame. The furnace wire used to ignite the hydrogen is located at the mouth of the outer tube. Since the mouth of the central tube of the quartz furnace is located inside the quartz furnace and is a certain distance away from the mouth of the outer tube of the quartz furnace, the hydrogen flame is often unable to be ignited, especially for elements that generate less hydrogen in the reaction. This becomes an obstacle for the atomic fluorescence spectrometer to measure these elements. Summary of the invention

[0006] The object of the present invention is to provide a hydride generation atomic fluorescence analysis system to effectively solve the above-mentioned problems in atomic fluorescence analysis.

[0007] The hydride generation atomic fluorescence analysis system of the present invention includes a sampling system, a gas-liquid separator, an atomizer and an inert gas generating device. A reduction reaction is carried out in the gas-liquid separator to generate a mixed gas, and the mixed gas enters the atomizer through a carrier gas. The atomizer includes an inner tube and an outer tube mounted on the outer side of the inner tube. It is characterized in that the gas outlet pipe of the gas-liquid separator is connected to the outer tube, and the inert gas generating device is connected to the inner tube.

[0008] Preferably, the mixed gas includes hydride of the element to be detected and hydrogen.

[0009] Preferably, the inert gas is argon.

[0010] Preferably, the flow rate of the carrier gas carrying the mixed gas into the outer tube of the atomizer is 1000-1200 ml / min.

[0011] Preferably, the flow rate of the inert gas introduced into the inner tube of the atomizer is 400-600 ml / min.

[0012] Preferably, the element to be detected is As, Hg, Se, Pb or Cd.

[0013] Preferably, the carrier gas is an inert gas. Preferably, the carrier gas is argon.

[0014] By adopting the above scheme, the present invention does not change the structure of the original atomizer during the atomic fluorescence analysis process, and uses a prototype quartz furnace to implement external tube sampling, thereby overcoming the defects of internal tube sampling. The hydrogen is heated by the furnace wire located at the mouth of the outer tube, and the hydrogen flame is very easy to ignite. The hydrogen flame formed is large and stable, and the measurement sensitivity is significantly improved. Experiments have shown that the external tube sampling method of the present invention is particularly suitable for elements that produce less hydrogen, and solves the problems in previous atomic fluorescence detection.

[0015] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the original sampling method of the quartz furnace in atomic fluorescence analysis;

[0017] Figure 2 It is a schematic diagram of the external tube sample injection method of the present invention in atomic fluorescence analysis;

[0018] Figure 3The peak curve of Cd (A width, fluorescence value-time) and the 0.1-0.5 ng / mL standard curve of Cd (B width, fluorescence value-concentration) were measured by the atomic fluorescence analysis method of the present invention using the external tube injection in Example 1;

[0019] Figure 4 In Example 2, the atomic fluorescence analysis method with external tube sampling of the present invention was used to simultaneously determine the peak curve of Hg / As (A width, fluorescence value-time) and the standard curve of a mixed solution of 0.1-0.5 ng / ml Hg and 10-50 ng / ml As (B width, fluorescence value-concentration).

[0020] Figure 5 The peak curve of Pb (A width, fluorescence value-time) and the 2-10 ng / mL standard curve of Pb (B width, fluorescence value-concentration) were determined by the atomic fluorescence analysis method with external tube sampling of the present invention in Example 1. DETAILED DESCRIPTION

[0021] The present invention discloses an atomic fluorescence analysis method for external tube sampling. Figure 2 Shown and Figure 1 In comparison, this method connects the hydride and hydrogen mixed gas (produced in the gas-liquid separator) carried by the carrier gas (argon gas) originally connected to the inner tube of the quartz furnace to the outer tube, and at the same time connects the shielding gas (Ar gas) tube of the outer tube to the inner tube as auxiliary gas; on the other hand, the flow rate of the carrier gas (also Ar gas) carrying the mixed gas is increased to 1000-1200ml / min, and the shielding gas flow rate (Ar gas volume) is reduced from the original 1000ml / min to 400-600ml / min. Some elements can be measured even without introducing auxiliary gas (i.e. 0ml / min).

[0022] The outer tube sampling method of the present invention changes the traditional mode of introducing hydrides (or Hg atoms) through the inner tube of the atomic fluorescence method. The mechanism is as follows: the gaseous atoms or molecules and hydrogen produced by the chemical reduction reaction are introduced from the outer tube of the quartz furnace along with the carrier gas Ar gas, and the hydride of the element to be measured (or mercury atoms) and the hydrogen mixture rise along the inner wall of the outer tube of the quartz furnace. The hydrogen is immediately ignited by the heat at the mouth of the quartz furnace tube, and the hydride is dissociated under the high temperature of the hydrogen-oxygen flame in the Ar gas atmosphere. The auxiliary gas (usually argon) that enters the inner tube pulls the hydrogen flame upward, and the hydrogen flame formed is much larger than that of the inner tube sampling, see Figure 2 shown.

[0023] This injection method combined with the original atomic fluorescence analysis process has been successfully used in the determination of As, Hg, Se, Pb and Cd in a variety of samples, improving the sensitivity of atomic fluorescence determination and solving the problem of atomic fluorescence analysis for the determination of trace elements such as Pb.

[0024] The existing atomic fluorescence instrument can be used in the detection. The atomic fluorescence instrument includes a sample injection system, a gas-liquid separator, an atomizer, an excitation light source and a detector. The specific operation of the detection example using the atomic fluorescence instrument is as follows:

[0025] Operation 1. Connect the gas outlet branch pipe (hydride, hydrogen and carrier gas mixture) of the gas-liquid separator to the outer tube of the atomizer quartz furnace, and connect the auxiliary gas (Ar gas) to the inner tube of the quartz furnace;

[0026] Operation 2. Turn on the power of the atomic fluorescence analyzer, select single channel or dual channel on the setting page of the desktop system, confirm the test conditions, light up the excitation light source of the element to be tested and preheat for 5-10 minutes;

[0027] Operation 3. Open the valves of the carrier gas and auxiliary gas (both can be Ar gas) cylinders, adjust their respective gas pressures and flows according to the settings, open the exhaust device of the atomizer, and connect the electric furnace wire power supply;

[0028] Operation 4. Start the sampling system to inject samples. After the gas-liquid separator completes the reduction reaction, the heating filament, excitation light source and detector of the quartz furnace work to obtain the fluorescence signal value of the element to be tested in the test solution; the peak curve of the fluorescence signal (fluorescence value-time) can be generated synchronously;

[0029] Operation 4. Obtain the fluorescence signal values ​​of the elements to be measured in the standard series solutions respectively, and prepare a fluorescence value-concentration standard curve; determine the fluorescence signal value of the elements to be measured in the sample solution, obtain the concentration of the elements to be measured in the sample solution from the standard curve, and calculate the content of the elements to be measured in the sample after inputting relevant parameters.

[0030] The above method can be used to determine a single element or two or more elements at the same time. When determining multiple elements, a standard mixed solution containing each element (the concentration of each element may be different) is prepared, and the sample is injected once and the corresponding excitation light of each element is used to act on the sample simultaneously to obtain the fluorescence signal values ​​of different elements respectively, and the content of the element to be measured in the sample is obtained according to the standard curve of the corresponding element.

[0031] The present invention is further described below in conjunction with specific examples, which are provided for illustrative purposes only and are not intended to limit the present invention. The concentration of reagents in the examples is expressed as a percentage by mass.

[0032] Example 1: Analysis of Cd

[0033] Test samples: rice, soybeans

[0034] Preparation of cadmium standard curve: First prepare 10ng / ml cadmium standard solution (prepared now), then take 0, 0.5, 1.0, 1.5, 2.0, 2.5ml of this standard solution in 50ml plastic quantitative bottles, add 4ml of 50% HCl solution and 5ml of 5% thiourea to each solution, dilute to the scale with water, the concentration of this standard series solution is 0, 0.1, 0.2, 0.3, 0.4, 0.5ng / ml Cd. After shaking well, measure the fluorescence signal of blank and standard series solutions according to the operation process, and prepare the standard curve (see Figure 3 Panel B, the slope of the standard curve exceeds 4000 / ng / ml. Panel A is the peak curve of Cd). During the operation, both the carrier gas and the auxiliary gas are Ar gas, and the flow rate of the argon gas (outer tube) as the carrier gas is controlled to 1000-1200ml / min, and the argon gas in the inner tube as the auxiliary gas is closed (the flow rate is 0ml / min).

[0035] Preparation and determination of test solution: Weigh 0.1-0.2g of rice or soybean sample, place in a 50ml plastic quantitative bottle, add 4ml of 50% HCl and 5ml of 5% thiourea, shake for 5-10min, dilute to scale with water, shake well and use the sample solution as the test solution to determine the fluorescence signal of the sample solution in the same way as the standard curve determination, obtain the Cd concentration from the standard curve and convert it into the content in the sample. The determination results of Cd in food samples are shown in Table 1.

[0036] Table 1. Test results of Cd in rice and soybean powder (ng / g)

[0037]

[0038]

[0039] From the data in the table, it can be seen that although the sample weight (G) varies greatly, the atomic fluorescence analysis using external tube sampling can quickly determine the cadmium in rice and other foods, and the measured Cd content in the sample is consistent with the recommended value.

[0040] Example 2: Simultaneous determination of Hg / As

[0041] Test sample: Soil

[0042] Since the content of As in soil is much higher than that of Hg, the existing atomic fluorescence spectrometer has not been able to simultaneously measure Hg and As in such samples. This embodiment uses the external tube sampling atomic fluorescence detection technology to achieve simultaneous detection of Hg and As in the same sample.

[0043] Preparation of standard curve: Prepare a mixed standard solution containing 500ng / ml As and 5ng / ml Hg in advance. Take 0, 1, 2, 3, 4, 5ml of this standard solution in a 50ml plastic quantitative bottle, add 5ml of 5% Vc-5% thiourea solution and 10ml of 50% HCl, dilute with water to the scale, and the Hg concentration in the obtained series of standard solutions is 0, 0.1, 0.2, 0.3, 0.4, 0.5ng / ml, and the As concentration is 0, 10, 20, 30, 40, 50ng / ml.

[0044] Select the dual-channel mode (equipped with excitation light sources corresponding to Hg and As respectively), and simultaneously determine the fluorescence signals of Hg and As in the blank and standard series solutions according to the above operation process, and prepare the standard curves of 0.1-0.5ng / mlHg and 10-50ng / mlAs of the mixed standard solution respectively. Figure 4 The A amplitude is the peak curve of Hg / As. Figure 4 Panel B is the standard curve of the mixed standard solution Hg and As (the signal of the standard curve is calculated based on the spectrum area, and the blank area has been subtracted). During the operation, both the carrier gas and the auxiliary gas are Ar gas, and the flow rate of the argon gas (outer tube) as the carrier gas is controlled at 1000-1200 ml / min, and the flow rate of the argon gas (inner tube) as the auxiliary gas is controlled at 400-600 ml / min.

[0045] Preparation and determination of test solution: 0.1-0.2g soil sample is placed in a 50ml plastic quantitative bottle, 5ml of 5% Vc-5% thiourea solution is added, 10ml of 50% HCl is added, and diluted to the scale with water. After shaking, the sample solution is used as the test solution. The fluorescence signals of Hg and As in the sample solution are determined simultaneously according to the same operation as in the standard curve determination. The concentrations of the corresponding elements are obtained according to their respective standard curves, and the contents of each element in the sample are calculated. The determination results are shown in Table 2.

[0046] Table 2. Simultaneous determination results of soil Hg / As

[0047]

[0048] The data show that the method and device solve the difficulty of simultaneously determining Hg and As in soil. It can also be seen that although the Hg content in the six samples (standard samples) varies greatly, the test results are consistent with the recommended value, indicating that the atomic fluorescence analysis method is highly accurate. In addition, in this embodiment, the two elements coexist in the test solution, sampling is completed once, and the detection of the dual-channel detection system is also completed once, and the entire test process is fast.

[0049] Example 3: Analysis of Pb

[0050] Test samples: Chemical reagents calcium chloride and calcium hydroxide

[0051] Preparation of lead standard curve: First prepare 100ng / ml lead standard solution, then take 0, 1, 2, 3, 4, 5ml of this standard solution in 50ml plastic quantitative bottles, add 10ml of 50% HCl solution and 5ml of 5% thiourea to each solution, dilute to the scale with water, the concentration of this standard series solution is 0, 2, 4, 6, 8, 10ng / ml Pb. After shaking well, measure the fluorescence signal of blank and standard series solutions according to the operation process, and prepare the standard curve (see Figure 5 B and A are the peak curves of Pb). During the operation, both the carrier gas and the auxiliary gas are Ar gas, and the flow rate of the carrier gas (outer tube) is controlled at 1000-1200 ml / min, and the flow rate of the auxiliary gas (inner tube) is controlled at 400-600 ml / min.

[0052] Preparation and determination of test solution: Weigh 0.2-0.3g of chemical reagent sample, transfer to a 50ml plastic quantitative bottle after dissolving, add 10ml of 50% HCl and 5ml of 5% thiourea, shake for 5-10min, dilute to scale with water, shake well and use the sample solution as the test solution to determine the fluorescence signal of the sample solution in the same way as the standard curve determination, obtain the concentration of Pb from the standard curve and convert it into the content in the sample. The determination results of Pb in chemical reagents are shown in Table 3.

[0053] Table 3. Determination results of Pb in calcium chloride and calcium hydroxide (ng / g)

[0054]

[0055]

[0056] The original atomic fluorescence analysis requires very strict control of acidity at 2% in the determination of Pb, otherwise no fluorescence signal can be detected. However, it is difficult for the test solution after pretreatment to meet this requirement. Moreover, the amount of hydrogen generated by the test solution with 2% acidity after the reduction reaction is small and difficult to ignite. This embodiment uses an external tube injection method while increasing the carrier gas flow rate. The hydrogen flame is easy to ignite. Atomic fluorescence analysis of Pb in a test solution with 10% acidity can form an obvious Pb peak curve (see Figure 5 (B) to improve the detection sensitivity and realize the determination of Pb.

Claims

1. A hydride generation atomic fluorescence analysis system, comprising a sampling system, a gas-liquid separator, an atomizer and an inert gas generating device, wherein a reduction reaction is performed in the gas-liquid separator to generate a mixed gas, and the mixed gas enters the atomizer through a carrier gas, and the atomizer comprises an inner tube and an outer tube sleeved on the outer side of the inner tube, characterized in that: The gas outlet pipe of the gas-liquid separator is connected to the outer pipe, and the inert gas generating device is connected to the inner pipe; the mixed gas includes hydride of the element to be measured and hydrogen.

2. The atomic fluorescence analysis system according to claim 1, characterized in that: The inert gas is argon; the inert gas generating device is an argon gas cylinder.

3. The atomic fluorescence analysis system according to claim 1, characterized in that: The flow rate of the carrier gas carrying the mixed gas into the outer tube of the atomizer is 1000-1200 ml / min.

4. The atomic fluorescence analysis system according to claim 1, characterized in that: The flow rate of the inert gas introduced into the inner tube of the atomizer is 400-600 ml / min.

5. The atomic fluorescence analysis system according to claim 1, characterized in that: The element to be detected is As, Hg, Se, Pb or Cd.

6. The atomic fluorescence analysis system according to claim 1, characterized in that: The carrier gas is an inert gas.

7. The atomic fluorescence analysis system according to claim 1, characterized in that: The carrier gas is argon.

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