Energy dispersive X-ray fluorescence sulfur analyzerAs a fast and accurate sulfur content detection device, the sulfur analyzer is widely used in fields such as petroleum, coal, and chemical engineering. The reliability of its detection results directly depends on standardized calibration operations. This article will systematically summarize the calibration process and key points of the sulfur analyzer from the aspects of calibration basis, preliminary preparation, core calibration methods, calibration verification, and precautions.
1、 Calibration Basis and Scope of Application
1. Core basis: Calibration must strictly follow relevant national standards and industry specifications, mainly referring to the "Calibration Specification for Energy Dispersive X-ray Fluorescence Spectrometer" (JJF 1160-2019), "Determination of Sulfur Content in Petroleum Products by Energy Dispersive X-ray Fluorescence Spectroscopy" (GB/T 17040-2019) and other standard requirements, to ensure that the calibration process is compliant and the results are effective.
2. Scope of application: This summary method is applicable to X-ray fluorescence sulfur analyzer based on energy dispersion principle, covering routine calibration types such as zero point calibration, span calibration, curve calibration, etc. in daily use. It is suitable for calibration scenarios of sulfur analyzer for different sample types such as liquid, solid (such as coal, ore), powder, etc.
2、 Preparation before calibration
1. Equipment and environmental inspection
(1) Equipment status: Confirm that the sulfur analyzer has stable power supply, reliable grounding, no damage to core components such as X-ray tubes and detectors, and no abnormal alarms; After turning on, complete the self-test to ensure that the instrument is in normal working condition.
(2) Environmental conditions: The calibration environment should meet the requirements of a temperature of 15 ℃~30 ℃, humidity ≤ 70%, no strong vibration or electromagnetic interference, and be away from dust, corrosive gases, and direct sunlight to avoid environmental factors affecting calibration accuracy.
2. Preparation of standard materials and auxiliary tools
(1) Standard substances: Select certified standard substances (CRM), whose sulfur content range should cover the detection range of the instrument, and the matrix should be consistent with the actual detection sample (such as using petroleum based sulfur standard substances for detecting petroleum samples and coal based standard substances for detecting coal). The number of standard substances should not be less than 3 concentration points (including low, medium, and high concentrations).
(2) Auxiliary tools: Prepare sample cups, sample films (such as polyester film, polypropylene film, ensuring no significant absorption of X-rays), samplers, scales (accuracy 0.1mg), etc. that meet the requirements. All auxiliary tools must be clean, dry, and free of sulfur contamination.
3、 Core calibration method
1. Zero point calibration (blank calibration)
(1) Calibration purpose: To eliminate the influence of instrument baseline drift, sample cup and sample membrane self sulfur contamination on detection results, and ensure the accuracy of low concentration sample detection.
(2) Operation steps: ① Select sulfur free blank samples (such as high-purity isooctane, blank sample film), put them into clean sample cups, ensure that the sample film is flat, wrinkle free, and undamaged, and the sample cup is well sealed; ② Place the blank sample into the instrument sample stage and set the detection parameters (such as measurement time, X-ray tube voltage/current) according to the instrument operating specifications; ③ Start the measurement, repeat the measurement 3 times, and record the results of each test; ④ The instrument automatically calculates the blank average value as the zero calibration value, completes the zero calibration, and saves the parameters.
2. Span calibration (single point calibration)
(1) Calibration purpose: To correct the sensitivity deviation of the instrument, suitable for daily rapid calibration or scenarios with narrow detection ranges and single sample matrices.
(2) Operation steps: ① Select certified standard substances that are consistent with the actual sample matrix and have sulfur content close to the commonly used detection range; ② Process standard materials according to sample preparation requirements (liquid samples are directly loaded into sample cups, while solid samples need to be ground to a uniform powder and compacted); ③ Place the standard substance into the instrument, set parameters consistent with the actual detection, perform 3 repeated measurements, and calculate the average value; ④ Enter the instrument calibration interface, input the standard value of the standard substance, compare the measured average value with the standard value, and the instrument automatically corrects the calibration coefficient to complete the span calibration.
3. Calibration of working curve (multi-point calibration)
(1) Calibration purpose: Suitable for scenarios with wide detection range and complex sample matrix, establish standard curves through multi-point fitting to improve detection accuracy across the entire range.
(2) Operation steps: ① Select 3-5 certified standard substances with different sulfur contents, covering the entire detection range of the instrument (low concentration points close to the detection limit, high concentration points close to the upper limit of the range), and the interval between adjacent concentration points is reasonable; ② Process all standard substances according to a unified sample preparation process to ensure consistency in the preparation process (such as sample size, compaction pressure, sample film thickness, etc.); ③ Place each concentration standard substance into the instrument in sequence and repeat measurements (3-5 times for each sample) under the set detection parameters. Record the measurement values for each time and calculate the average value; ④ Enter the instrument curve calibration interface, input the sulfur content standard value of each standard substance and its corresponding measurement average value, select the appropriate fitting method (such as linear fitting, quadratic polynomial fitting), and the instrument will automatically generate a working curve; ⑤ Verify curve correlation: Ensure that the curve correlation coefficient R ² is ≥ 0.995. If the correlation does not meet the standard, the standard substance, sample preparation process, or instrument parameters need to be rechecked and recalibrated.
4. Instrument performance verification and calibration
(1) Calibration purpose: Regularly verify the stability, repeatability, and accuracy of the instrument to ensure its continuous reliability after calibration.
(2) Operation steps: ① Select 1-2 intermediate concentration certified reference materials as validation samples; ② Measure and verify samples according to the daily testing process, and record the measurement results; ③ Calculate the relative error between the measured value and the standard value (with a requirement of ≤± 5%, adjusted according to the standard requirements), and also calculate the relative standard deviation of repeated measurements (RSD ≤ 3%); ④ If the relative error or RSD exceeds the allowable range, it is necessary to recalibrate and troubleshoot the instrument (such as X-ray tube aging, detector contamination, etc.).
4、 Calibration cycle and records
1. Calibration cycle: Under normal circumstances, the sulfur analyzer needs to undergo a comprehensive calibration (working curve calibration) every 6 months; In daily use, zero calibration and span calibration are required every time the machine is turned on or the sample substrate is replaced; If the instrument malfunctions and is repaired, has abnormal test results, or has been out of use for a long time before being restarted, it is necessary to recalibrate the full range working curve.
2. Calibration records: Establish a complete calibration ledger, detailing the calibration date, calibration personnel, instrument model and number, standard substance information (name, number, concentration, expiration date), calibration method, calibration parameters, measurement results, curve correlation, verification results, and other information to ensure traceability of records.
5、 Calibration precautions
1. Standard substance management: Standard substances must be used within their validity period and stored under the required conditions (such as sealing, avoiding light, refrigeration, etc.) to avoid contamination or deterioration; The standard substance after opening should be used as soon as possible, and the remaining part should be properly stored and labeled with the opening date.
2. Consistency of sample preparation: During the calibration process, the sample preparation process (such as sampling amount, grinding fineness, compaction pressure, sample film type and thickness) must be completely consistent with the actual tested sample, otherwise it may cause calibration deviation.
3. Instrument parameter stability: During the calibration process, parameters such as X-ray tube voltage, current, and measurement time must be kept stable and cannot be changed arbitrarily; If parameters need to be adjusted, recalibration is required.
4. Safe operation: During the calibration process, it is necessary to strictly follow the X-ray safety operation specifications and avoid direct contact with the X-ray source; When the instrument is running, the sample room door needs to be closed to prevent X-ray leakage.
5. Fault handling: If there are problems such as large fluctuations in measurement results and poor curve correlation during the calibration process, it is necessary to first check whether the standard substance has failed, whether the sample is contaminated, and whether the instrument components are normal before recalibrating. It is strictly prohibited to forcibly complete calibration without troubleshooting.
In conclusion,Energy dispersive X-ray fluorescence sulfur analyzerThe calibration of the instrument needs to be combined with the detection scenario to select the appropriate calibration method, strictly follow the standard requirements, pay attention to early preparation, operational standardization, and later verification, in order to ensure the accuracy and reliability of the instrument detection results and provide strong support for subsequent detection work.