The following is a comprehensive analysis of the usage details of the total organic carbon analyzer, covering key points throughout the entire process from preparation to detection:
1、 Startup and preheating
After turning on the instrument power, enter the initialization program and patiently wait for the system to complete the self-test process. Most models are equipped with automatic flushing function, which can synchronize pipeline cleaning. It is recommended that the preheating time be no less than 30 minutes to ensure that the core components such as the combustion furnace and infrared detector reach a stable working temperature and avoid baseline fluctuations caused by thermal drift affecting the detection results.
2、 Sample collection and preservation
Sampling containers must be strictly pre treated: glass containers need to be soaked in hydrochloric acid to remove inorganic carbon residues, while plastic containers are preferred to use low background materials. When collecting water samples, they should be slowly injected below the bottle mouth to prevent air disturbance from introducing microbial contamination. Samples containing particulate matter need to be filtered through a 0.45 μ m membrane, while turbid samples can be separated by centrifugation to obtain the supernatant. During the sample storage period, it needs to be refrigerated and transported, and the testing should be completed within 48 hours to avoid data bias caused by microbial reproduction.
3、 Reagent configuration and standard curve
The pressure of the carrier gas (such as high-purity oxygen) cylinder should be controlled within a specified range to ensure stable combustion efficiency. The standard solution of potassium hydrogen phthalate should be prepared and used immediately, with a gradient concentration covering the expected detection range. Before each analysis, it is necessary to establish a standard curve and force calibration through the origin to eliminate systematic errors. Pay special attention to the degradation of catalyst activity inside the high-temperature combustion tube, and regularly replace aging fillers to ensure oxidation efficiency.
4、 Key steps for sample determination
Before injection, rinse the injection needle with ultrapure water at least 3 times to eliminate any residue in the tubing. Set an appropriate injection volume, and for low concentration samples, a large volume injection mode can be used to improve sensitivity. Pay attention to observing whether the combustion peak shape is normal. Abnormal peaks may indicate salt deposition or interference from volatile organic compounds. Blank samples should be inserted between each batch of samples to monitor background values. When the blank value exceeds the set threshold, the machine should be stopped in a timely manner to investigate the source of contamination.
5、 Data Processing and Quality Control
The standard curve should be constructed using multi-point correction method, and the correlation coefficient should be ≥ 0.999. The spiked recovery rate experiment is a necessary means of verifying accuracy, with typical spiked amounts ranging from 50% to 100% of the sample concentration. The relative deviation of parallel samples should be controlled within ± 5%, and it is recommended to increase the number of repetitions for complex matrix samples. Regularly carry out deep cleaning procedures, including replacing combustion tube packing, cleaning key components such as gas-liquid separators.
6、 Special sample processing plan
For high salt samples, dilution method combined with electrolysis can be used to remove halide ions; Ultrasonic degassing treatment is recommended for sewage samples with high suspended solids. The oil substances in industrial wastewater are prone to clogging the injection valve and can be protected in real-time through an online plunger filter. For samples with a high proportion of volatile organic compounds, low-temperature enrichment modules can be used to improve capture efficiency.
The precision operation of the total organic carbon analyzer runs through the entire chain of sample pretreatment, instrument condition optimization, data acquisition, and quality control. Operators need to strictly follow standardized procedures and flexibly adjust parameters based on sample characteristics in order to obtain accurate and reliable detection results. Pay special attention to key indicators such as combustion tube brightness and flow meter readings during daily maintenance, and promptly identify and resolve potential faults and hazards.