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Beijing Liyuan Electronic Instrument Co., Ltd

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Fully automatic flow injection analyzer

NegotiableUpdate on 07/07

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Nature of the Manufacturer: Producers

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Overview

The flow injection analyzer adopts an optical system consisting of a cold light source and optical fibers. The cold light source has a service life of 100000 hours and stable optical energy output, which makes the preheating time short and the optical energy decay slow. It will not cause baseline drift due to overheating of the light source, and the optical system will achieve the best use conditions. The optical signal transmitted through the optical fiber will not be distorted, greatly reducing baseline noise and drift, and enhancing detection sensitivity

Product Details

The basic principle of flow injection

定量原理

The principle of peak height quantification is that visible light passes through a flow cell, and colored products absorb its photon energy, reducing the light energy. Photons scan the photovoltaic cell, converting light energy into electrical energy and generating voltage. The higher the light energy, the higher the voltage. When there is no sample current passing through the flow cell, no colored products are generated, and the light transmittance is the highest, corresponding to the highest voltage value. This is used as the baseline.

When there is a sample, colored products are generated, and the transmittance of light decreases, resulting in a corresponding decrease in the photoelectric voltage value. The level of this voltage value has a very good logarithmic relationship with the concentration of the sample.

We can treat the voltage value as the transmittance value and convert it logarithmically to the absorbance value, which has a good linear relationship with the colored generated concentration value. In the recorded calibration curve graph, a negative peak shape is obtained. According to Lambert Beer's law, when a parallel monochromatic light passes through a solution, the absorbance A of the solution to light is proportional to the product of the concentration c of the solution and the thickness l of the liquid layer.

The meaning of A or T represents the degree of absorption of light by the solution. A high A value or a low T value indicates a high degree of light absorption by the solution, indicating a low projected light intensity.

The absorption coefficient k is related to the properties of the solution, the type of solvent, the wavelength of the incident light, and temperature, but not to the concentration of the solution or the thickness of the liquid layer.

Flow injection system

The flow injection system consists of a pump, valve, mixing ring, pipeline, detector, etc.

There are two commonly used types of pumps: peristaltic pumps and infusion pumps.

A peristaltic pump consists of a driving motor, a pump head, a cover or belt, a pressure regulating device, and a pump tube. Commonly used motors include synchronous motors, reversible motors, and stepper motors. The pump head is composed of rollers, which are required to be precision machined from wear-resistant and corrosion-resistant materials. The roller and motor shaft must be strictly concentric. The capping is divided into multi pass integrated, split type, and tape pressing type. The first two have high requirements for the curvature of the cover. The pressure regulating device requires easy adjustment and does not change on its own after adjustment. The commonly used pump tubing is polyvinyl chloride, also known as pump tubing and silicone rubber pump tubing. The working principle of a peristaltic pump is that the pump tube is continuously compressed between the pump head and the cover, giving the pump tube the function of suction and infusion. The flow rate is determined by the rotational speed of the pump head, the inner diameter of the pump tube, and the degree of compression of the gland. Peristaltic pumps are relatively cheap and can meet the requirements. The most commonly used pump currently is the peristaltic pump, but it is only suitable for situations where the system pressure is relatively low.

For situations with high flow rate requirements and high system pressure, injection pumps are mostly used. The basic structure is that the spiral rod fixed on the bracket is driven by a stepper motor. When the spiral rod retracts, it drives the syringe piston to retract, and vice versa, it pushes the inhaled liquid into the pipeline. Due to the constant rotation of the spiral rod driven by the motor, it can achieve extremely stable flow velocity and withstand significant pressure. However, its disadvantage is that it is expensive and can only drive one flow path.

Single injection valve

Usually refers to a six hole two slot rotary valve, with a double-layer structure and three grooves on the rotor, evenly distributed on a concentric circle. The length of the grooves is 1/6 of the circumference of the concentric circle. There are 6 holes on the stator that can be connected to pipes, which are connected to the two ends of the rotating slot. Connect two opposing holes to form a sampling ring, with one side of the valve serving as the sample inlet and waste liquid outlet, and the other side serving as the reagent carrier liquid inlet and outlet to the detector. The rotation angle of the rotor is 60 °, and the sample strip is "cut into" the flow path by the rotation of the injection valve. In addition to the six way valve, there are also two-way, two-way, four-way, eight way, ten way and other types of valves that can be selected according to different flow path design requirements. The connection method is extremely flexible and can meet the needs of various systems.

The groove of the injection valve is located in the rotatable part of the valve. In the sampling state, the groove connects the sample inflow pipeline, sample outflow pipeline, and quantitative sampling ring. The sample flows into the sampling ring through the groove, fills the sampling ring, and flows out through another groove to complete quantitative sampling. Rotate the rotatable part of the injection valve to the injection state. At this time, the groove connects the reagent inflow pipeline, reagent outflow pipeline, and sampling ring. The sample filled with the sampling ring in the sampling state is "cut into" the flow path of the reagent and carried into the reaction tube, completing a sampling process.

Heating coil (also known as mixing coil or reaction coil)

A reaction coil is a place where the sample is injected into the reagent flow path through an injection valve, where the reagent is mixed and undergoes a chemical reaction. Generally, polytetrafluoroethylene tubes with an inner diameter of 0.5 or 0.8mm are wound in a circular shape, which is beneficial for increasing radial diffusion, reducing axial diffusion, and increasing the mixing degree between the sample and the reagent, while minimizing the dispersion of the sample in the carrier fluid. If the circle diameter is small, increasing radial diffusion is beneficial for the mixing of the sample and the reagent. The result is more symmetrical than the peak obtained from the same straight tube, higher and narrower, and the tighter the disk, the more obvious this effect. According to specific testing requirements, the length of the coil generally ranges from tens of centimeters to several meters.

detector

The commonly used detection methods in flow injection analysis include absorption spectrophotometry, turbidity method, chemiluminescence method, fluorescence method, and the principles of flow injection analysis. The original methods include absorption spectroscopy, flame photometry, ion selective electrode method, and voltammetry.

The detectors used in detection methods are basically divided into two categories: optical detectors and electrochemical detectors. The commonly used detectors nowadays are optical detectors, among which the most widely used is the spectrophotometer with a flow cell.

FIA vs CFA

Flow Injection Analyzer (FIA)

Flow Injection Analysis (FIA) is a wet microanalysis technique proposed by Danish scholars Ruzika and Hansen in 1974, based on continuous flow analysis, in response to market demands for specific fields such as small sample sizes, expensive reagents, and rapid analysis.

Flow injection analysis technology is a technique that injects a sample into a continuous liquid flow without bubble gaps under thermodynamic non-equilibrium conditions. The sample and reagent are mixed in a specific order and proportion, and then enter a flow cell for colorimetric analysis under non full reaction conditions. Quantification is performed using peak height or peak area.

Continuous Flow Analyzer (CFA)

Continuous Flow Analysis (CFA) was first introduced and used by Professor L Skeggs at the University of California, USA in 1954. This technology is an automatic continuous analysis technique that mixes reagent flow and sample flow in a specific order and ratio under thermodynamic equilibrium, and performs quantitative detection after complete reaction.

Continuous flow analysis technology uses continuous flow to extract sample solutions from various reagent containers, mix the samples with reagents in the flow system, and use a peristaltic pump to draw air, samples, and reagents into the determined flow path in a specific order and proportion, and finally reach the detector to complete the analysis process of detection. In application, CFA can be used for detecting complex substrates such as wastewater.

The following table provides a brief comparison between CFA and FIA.

project	CFA class instruments	FIA class instruments
market situation	CFA instruments are mostly from foreign brands.	There are mostly domestic brands of FIA instruments.
Instrument configuration	Module independent design or multi-channel combination.	Module independent design or multi-channel combination.
sample pretreatment	The sample can be injected directly without filtering or degassing.	The reagent needs to be degassed before each use.
Reaction pipeline	The pipe diameter is relatively thick (about 2.0 mm), mainly consisting of glass mixing rings	Thin pipe diameter (0.5~0.8 mm), made of PTFE plastic material
Distillation device	Blow off distillation and fraction collection, made of glass material, especially suitable for wastewater detection with complex substrates.	Using membrane separation distillation requires frequent membrane replacement
UV digestion	Made of quartz material, with a sufficiently long digestion tube and high digestion efficiency.	Weakened digestion function
Heating method	Oil bath or electric heating.	Oil bath or electric heating.
sample size	Peristaltic pump controls sampling volume	Multi way valve (commonly used six way valve) injection, more accurate injection, less sample required, and more precise analysis.
Flow detection pool	In addition to 1 and 3 cm, longer path flow cells can also be configured to achieve higher sensitivity.	1. 3 cm circulation pool
light source	LED lights or halogen lights.	LED lights or halogen lights.
detector	Silicon photodiodes, CCD detectors, and photovoltaic cells are commonly used.	Silicon photodiodes, CCD detectors, and photovoltaic cells are commonly used.
Analysis speed	10~120 samples per hour.	15~150 samples/hour, faster speed
Sample dosage	1-3 milliliters per time.	200-500 microliters/time, with low sample consumption

Overall, CFA pipelines are thick and not easily clogged, so no special pre-treatment is required and can tolerate "dirty" substrates such as sewage. FIA injection is more accurate, so the accuracy is high, but the pipeline is thinner and more suitable for cleaner water, such as drinking water. In recent years, R&D personnel have configured some online pre-processing before FIA, treating water "clean" before entering the FIA system, which may achieve both accuracy and resistance to "dirt".

1Flow injection analyzerInstrument Features

Stereoscopic structure, instrument adopts integrated channel design, sampling and reaction are integrated, without the need for a matching host

Piston pump replaces traditional peristaltic pump, with self setting flow rate and no need to switch peristaltic pump tubes, saving time and effort

流动注射分析仪

CAN port communication method, capable of linking multiple modules for simultaneous data analysis

The circulation pool adopts an adjustable angle suspension structure to prevent the formation of bubbles in the path. At the same time, it adopts a vibration suspension automatic bubble removal structure, which can instantly discharge bubbles and ensure the accuracy of measurement

流动注射分析仪

The optical system is composed of a cold light source and optical fibers. The cold light source has a service life of 100000 hours and stable optical energy output, which makes the preheating time short and the optical energy decay slow. It will not cause baseline drift or other problems due to overheating of the light source, achieving the best conditions for the optical system. The optical signal is not distorted during fiber transmission, greatly reducing baseline noise and drift, and enhancing detection sensitivity

IIFlow injection analyzerApplication Areas

Analysis of Drinking Water, Surface Water, Groundwater, and Wastewater - Volatile Phenols cyanide、 More than ten detection items including sulfides, anionic surfactants, total phosphorus, total nitrogen, ammonia nitrogen, nitrate, nitrite, etc

Soil and plant analysis - total nitrogen, nitrate, nitrite, available phosphorus, available boron and other items

流动注射分析仪
Beverage and Food Analysis - Cyanide in Alcohol

Fertilizer analysis - available phosphorus, ammonia nitrogen, nitrate, nitrite