Common problems and inspection methods of flame detectors

Flame detectors have fast reaction speed, small size, fast response, and wide linear range, and can be effectively used in combination with porous columns. They are currently ideal detectors for the use of trace elements in organic compounds. However, after a long period of application of instruments and equipment, some common failures in hardware configurations may occur. Generally, a FID system is mainly composed of three parts: a detector, an inspection power supply circuit (amplifier), and a gas path. When a fault occurs or the analysis spectrum is abnormal, the resolution should be checked from three aspects to prevent loss of direction. Based on long-term use, the common problems of the 1790F gas chromatography FID system are sorted out.

Common faults of flame detectors:

Do not ignite; The base flow is very large; Baseline drift is relatively severe.

Fault location:

Difficulty in gas path or detector.

Common faults:

Very noisy; The sensitivity decreased significantly; Can't come out of the peak.

Fault location:

Gas path, detector, and circuit problems.

Common faults:

The chromatographic peak shape is abnormal.

Fault location:

Difficulties in injector, gas path, and detector.

Common faults:

The signal is sometimes absent.

Fault location:

Circuit problems.

1. Gas path inspection

(1) Check for problems with radon, N2, and air flow. Too small air flow and severe steam leakage from the nozzle can also cause a relatively large explosion sound and prevent ignition; If the radon gas is too small and the N2 exchange is too high, the ignition will be confused and it will be very easy to shut down; Nozzle leakage and liquid chromatography column leakage not only make ignition difficult, but also lead to reduced sensitivity and even inability to peak; Inappropriate proportions of total radon and N2 flows will significantly affect sensitivity; Large total radon flow leads to increased noise.

(2) Is the air circuit system clean. Dirty gas path system software, including environmental contamination of the injector, environmental contamination of the detector, or insufficient aging of the liquid chromatographic column can cause base flow, noise, and baseline drift.

(3) Check the base flow size. Before ignition, the reference line of the amplifier should be set to the zero position and periphery of the video recorder as much as possible. Without rotating the zero adjustment resistor, after ignition, the distance between the recording pen and the zero position can be marked with the base current size, and can be determined by changing the measurement range of the video recorder or the loss multiplier of the amplifier.

Generally, when the radon gas is adjusted to the standard value after ignition, the deviation of the basic flow is less than 1mv, indicating that the system software is very clean.

2. Flame detector inspection

(1) Nozzle and nozzle mouth parts. The nozzle leakage of Xuzhou Jieneng Power Equipment Co., Ltd. will affect ignition, sensitivity, peak shape, and baseline drift; The nozzle mouth is higher than the plan view of the electrode circle, and the sensitivity decreases significantly. This is usually caused by the quartz stone nozzle being pressed by the column tube when filling the liquid chromatography column tube; Conversely, if the nozzle orifice is smaller than the plan of the electrode circle or the electrode collides with the nozzle, the noise will greatly increase.

(2) Inspection and collection pole. If the collector electrode is poorly insulated, the noise will be very loud, the reference line will be unstable, and the drift will be relatively serious; The collector ion current power cord is loose or disconnected, resulting in no peaks.

(3) The detector is not contaminated with the environment. The size of the base flow transition can be determined by using a partial warming method. The method to eliminate waste is to disassemble components and conduct high-temperature aging.