As a high-precision detection device, total organic carbon analyzer is widely used in water quality monitoring, pharmaceuticals, semiconductor manufacturing and other fields. The accuracy of its detection results is affected by multiple factors. The following will comprehensively analyze the main influencing factors from the aspects of sample properties, instrument performance, operating conditions, environmental factors, and human factors:
1、 Sample characteristics and pretreatment
1. Sample uniformity and impurities: If the sample contains suspended particles or inorganic salts, it may cause blockage of the injection system or interfere with the oxidation reaction. For example, high salinity samples can easily trigger the "salt effect", leading to incomplete combustion or catalyst poisoning; When suspended solids are not sufficiently dispersed, local overheating may damage the reaction system. Therefore, it is necessary to improve uniformity through pre-treatment such as filtration (e.g. 0.45 μ m filter membrane), centrifugation, or dilution.
2. Sample preservation and biodegradation: Microbial activity in water samples can alter the organic content, requiring refrigeration or the addition of fungicides (such as copper sulfate) to inhibit degradation. Otherwise, the decomposition of organic matter during storage will result in a lower TOC value.
3. Special chemical composition interference: Strong oxidizing ions (such as Cl ⁻, SO ₄² ⁻) may participate in side reactions, consume oxidants, and release CO ₂; Nitrogen containing compounds (NH ∝/NO ₓ) are converted to N ₂ O at high temperatures, which was mistakenly included in the TOC results. At this point, interference needs to be eliminated through acidification blow off or specific absorption devices.
2、 Instrument performance and calibration maintenance
1. Differences in working principles: Although combustion oxidation method (≥ 680 ℃) can oxidize organic matter, it may be interfered by inorganic carbon (IC) and requires acidification pretreatment to remove IC; UV catalytic method has low energy consumption, but incomplete oxidation of complex organic matter (such as aromatic hydrocarbons) requires the combination of persulfate enhanced oxidation.
2. Calibration and hardware status: Calibration error is an important influencing factor, and using expired or concentration biased standard solutions for calibration will systematically deviate the results. It is necessary to regularly verify with certified standard substances. In addition, hardware losses such as combustion tube crystallization, catalyst failure, or saturation of CO ₂ adsorbent can lead to a decrease in sensitivity.
3、 Reagent and operating condition control
1. Reagent quality: Insufficient purity of the reagent (such as containing organic impurities) or expiration may introduce additional carbon sources, leading to an increase in background values. It is recommended to use high-purity reagents (such as chromatographic purity) and store them in a sealed and dark place.
2. Operating parameters: Temperature and pressure directly affect the oxidation reaction rate. The combustion method requires temperature control of ± 1 ℃, and pressure fluctuations may change gas solubility. It is necessary to maintain environmental stability. The injection volume must be strictly consistent, and a volume error exceeding 2% will cause significant deviation.
4、 Environmental and human factors
1. Laboratory environment: Temperature fluctuations>2 ℃ or humidity>60% may affect sensor stability. It is recommended to have an ambient temperature of 10-25 ℃ and humidity<60%. Samples or instrument components (such as optical windows) contaminated with dust or volatile organic compounds should be operated on a clean bench and regularly cleaned.
2. Operating standards: Insufficient personnel training may lead to improper operations (such as failure to perform blank experiments, incorrect flow rate settings), and regular training and adherence to SOP are required. Incomplete data recording will affect the traceability of results, and complete preservation of logs and original data is required.
The results of a total organic carbon analyzer are influenced by multiple factors such as sample properties, instrument status, operational details, environmental conditions, and human operation. To ensure data accuracy, a full process quality control system needs to be established, covering sample pretreatment, instrument calibration, reagent management, environmental control, and personnel training.