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The calculation of the detection limited LOD
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Martha Kirtley
The calculation of the detection limited LOD
3S/N is not a formula. It should be based on the signal -to -noise ratio, that is, S/Nu003e 3 as a judgment.
The prerequisite for detecting the calculation of the limit is: after deducting the blank value, when the content of the object to be tested is approaching 0, the signal is approaching 0, and the two can be regarded as [123 near 0. [123 can be regarded as [123 ]direct ratio.
Since the blank value always fluctuates (accidental error) in actual experiments, only when the difference between the signal and the blankness is large enough can the obtained readings obtained in full Only at this time can the obtained readings be regarded as evidence that the number of readings is to be tested. The minimum to generate this signal is to detect the limit.
So how can it be regarded as "the difference between the signal and the blankness is large enough"? As mentioned above, the fluctuation of the blank value as the starting point is the point. The volatility of the blank value can be represented by multiple measurement of the blank value. Therefore, when the difference (signal value) of the average value of the instrument and the average value of the blank value is greater than the standard deviation of the blank value, it can be regarded as "enough", and the mathematical formula is expressed as s/nu003e 3 3 Essence
3S/N is not a formula. It should be based on the signal -to -noise ratio, that is, S/Nu003e 3 as a judgment.
The prerequisite for detecting the calculation of the limit is: after deducting the blank value, when the content of the object to be tested is approaching 0, the signal is approaching 0, and the two can be regarded as [123 near 0. [123 can be regarded as [123 ]direct ratio.
Since the blank value always fluctuates (accidental error) in actual experiments, only when the difference between the signal and the blankness is large enough can the obtained readings obtained in full Only at this time can the obtained readings be regarded as evidence that the number of readings is to be tested. The minimum to generate this signal is to detect the limit.
So how can it be regarded as "the difference between the signal and the blankness is large enough"? As mentioned above, the fluctuation of the blank value as the starting point is the point. The volatility of the blank value can be represented by multiple measurement of the blank value. Therefore, when the difference (signal value) of the average value of the instrument and the average value of the blank value is greater than the standard deviation of the blank value, it can be regarded as "enough", and the mathematical formula is expressed as s/nu003e 3 3 Essence
The following is the actual calculation.n is the standard deviation of the blank value. The actual calculation method is to determine the blank value at least 11 times in the actual experiment, calculate the average value, then reduce the average value of each blank value, then square square meter, and then reduce the 11 square meters of square square meters.In addition to the decrease of the number of measurements (the measurement 11 times is 10 times), and finally this number is opened.
After n, the minimum signal difference required by the detection limit is obtained by 3 (the difference between the average value of the instrument reading and the blank value) is 3N.Then you need to convert this minimum signal difference to the required measuring object content.According to the premise of "when the content of the object is approaching 0, the signal is approaching 0, and the two can be regarded as a proportional relationship near 0", the measurement of a signal to be close to zero to deduct the blank value to deduct the blank valueAfter the average value is proportional to the slope of the relationship, and then use 3n to divide the slope to detect the limit.
The following is the actual calculation.n is the standard deviation of the blank value. The actual calculation method is to determine the blank value at least 11 times in the actual experiment, calculate the average value, then reduce the average value of each blank value, then square square meter, and then reduce the 11 square meters of square square meters.In addition to the decrease of the number of measurements (the measurement 11 times is 10 times), and finally this number is opened.
After n, the minimum signal difference required by the detection limit is obtained by 3 (the difference between the average value of the instrument reading and the blank value) is 3N.Then you need to convert this minimum signal difference to the required measuring object content.According to the premise of "when the content of the object is approaching 0, the signal is approaching 0, and the two can be regarded as a proportional relationship near 0", the measurement of a signal to be close to zero to deduct the blank value to deduct the blank valueAfter the average value is proportional to the slope of the relationship, and then use 3n to divide the slope to detect the limit.
3 S/N The landlord may not be comprehensive.Generally s/n u003d 3 is LOD, LOQ is s/n u003d 10. So, LOQ can be about 3 times the LOD.LOD is generally determined by the concentration of signal -to -noise ratio (that is, s/n) u003d 3, but it is actually rigorous than this requirement.Because once you determine the LOD, in case your instrument fluctuations cause the sensitivity to reduce the sensitivity, you will not reach this minimum detection limit, so it is recommended to choose the LOD of the guarantee in the actual operation.
3 S/N The landlord may not be comprehensive.Generally s/n u003d 3 is LOD, LOQ is s/n u003d 10. So, LOQ can be about 3 times the LOD.LOD is generally determined by the concentration of signal -to -noise ratio (that is, s/n) u003d 3, but it is actually rigorous than this requirement.Because once you determine the LOD, in case your instrument fluctuations cause the sensitivity to reduce the sensitivity, you will not reach this minimum detection limit, so it is recommended to choose the LOD of the guarantee in the actual operation.
The prerequisite for detecting the calculation of the limit is: after deducting the blank value, when the content of the object to be tested is approaching 0, the signal is approaching 0, and the two can be regarded as [123 near 0. [123 can be regarded as [123 ]direct ratio.
Since the blank value always fluctuates (accidental error) in actual experiments, only when the difference between the signal and the blankness is large enough can the obtained readings obtained in full Only at this time can the obtained readings be regarded as evidence that the number of readings is to be tested. The minimum to generate this signal is to detect the limit.
So how can it be regarded as "the difference between the signal and the blankness is large enough"? As mentioned above, the fluctuation of the blank value as the starting point is the point. The volatility of the blank value can be represented by multiple measurement of the blank value. Therefore, when the difference (signal value) of the average value of the instrument and the average value of the blank value is greater than the standard deviation of the blank value, it can be regarded as "enough", and the mathematical formula is expressed as s/nu003e 3 3 Essence
The prerequisite for detecting the calculation of the limit is: after deducting the blank value, when the content of the object to be tested is approaching 0, the signal is approaching 0, and the two can be regarded as [123 near 0. [123 can be regarded as [123 ]direct ratio.
Since the blank value always fluctuates (accidental error) in actual experiments, only when the difference between the signal and the blankness is large enough can the obtained readings obtained in full Only at this time can the obtained readings be regarded as evidence that the number of readings is to be tested. The minimum to generate this signal is to detect the limit.
So how can it be regarded as "the difference between the signal and the blankness is large enough"? As mentioned above, the fluctuation of the blank value as the starting point is the point. The volatility of the blank value can be represented by multiple measurement of the blank value. Therefore, when the difference (signal value) of the average value of the instrument and the average value of the blank value is greater than the standard deviation of the blank value, it can be regarded as "enough", and the mathematical formula is expressed as s/nu003e 3 3 Essence
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After n, the minimum signal difference required by the detection limit is obtained by 3 (the difference between the average value of the instrument reading and the blank value) is 3N.Then you need to convert this minimum signal difference to the required measuring object content.According to the premise of "when the content of the object is approaching 0, the signal is approaching 0, and the two can be regarded as a proportional relationship near 0", the measurement of a signal to be close to zero to deduct the blank value to deduct the blank valueAfter the average value is proportional to the slope of the relationship, and then use 3n to divide the slope to detect the limit.
After n, the minimum signal difference required by the detection limit is obtained by 3 (the difference between the average value of the instrument reading and the blank value) is 3N.Then you need to convert this minimum signal difference to the required measuring object content.According to the premise of "when the content of the object is approaching 0, the signal is approaching 0, and the two can be regarded as a proportional relationship near 0", the measurement of a signal to be close to zero to deduct the blank value to deduct the blank valueAfter the average value is proportional to the slope of the relationship, and then use 3n to divide the slope to detect the limit.
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quantitative limit is s/n u003d 3
quantitative limit is s/n u003d 3
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