Table: Make the experimental data into a table. It shows the corresponding relationship between variables and reflects the changing law between variables. It is the basis of drawing curves.
Graphic formula: plot experimental data into curves. It intuitively reflects the relationship between variables. It can be seen in almost all reports and papers that it provides the necessary functional form for sorting into mathematical models (equations).
Functional formula: with the help of mathematical methods, the experimental data are arranged into equations or mathematical models in a certain functional form.
Familiar with the definitions of correlation and regression, correlation coefficient and the least square method of linear regression.
Familiar with the definition and inspection methods of each index in the verification of drug quality standard analysis methods.
Evaluation of content determination method (efficiency index-analytical quality factor);
Commonly used evaluation indexes of analytical efficiency include precision, accuracy, detection limit, quantitative limit, selectivity, linearity and range, reproducibility, durability and so on. The efficiency index of the determination method can be used to evaluate and analyze the determination method, and can also be used as the experimental research basis for establishing a new determination method.
1. Precise
Refers to the degree to which a group of measured values of the same homogeneous sample measured by this method are consistent with each other. The closer they are, the more accurate they are. In drug analysis, the commonly used standard (deviation) is poor (sd or S); Relative standard deviation (rsd), also known as coefficient of variation (cv), represents.
When analyzing biological samples, rsd is often used to express precision, which can be subdivided into intra-batch (or intra-day) precision and inter-batch (or inter-day) precision.
Intra-batch precision: refers to the precision of the same determination. Usually, 7- 10 samples of the same sample with high, medium and low concentrations are used, and the samples of each concentration are operated according to the suggested analysis method, and determined one by one after one start. Calculate the sd value and rsd value of each concentration sample. Intra-batch accuracy can also be regarded as intra-day accuracy. The relative standard deviation should be less than 5%, but not more than 10%.
Inter-batch precision: refers to the precision of different determinations. Usually, high, medium and low concentrations of the same sample are used, and 7- 10 copies are prepared for each concentration, and then frozen in the refrigerator. From the date of sample preparation, operate according to the proposed analysis method, take out one sample every day and calculate the sd value and rsd value of each concentration sample. Inter-batch accuracy can also be regarded as daytime accuracy. The relative standard deviation should be controlled within 65438 05%.
2. Accuracy (sex)
Refers to the degree to which the measured results are close to the true values, indicating the correctness of the analysis method.
Because the "true value" cannot be accurately known, it is usually expressed by the recovery rate test.
When determining the content of the preparation, the recovery rate test and rsd should be calculated by adding the API reference substance to the blank excipients, and the blank determination of the separate excipients should also be carried out. Each sample should be prepared by simulation, and at least three concentrations of high, medium and low should be determined, and each concentration should be determined three times. * * * 9 data are provided for evaluation.
Recovery rate = (average measured value m- blank value b)/ dose a× 100%%
The relative standard deviation of recovery rate should generally be less than 2%.
3. Detection limit
Refers to the minimum concentration of drug in the sample when the analytical method can distinguish the drug from the background signal, without quantitative determination. Lod is a performance index of limit test, which not only reflects the sensitivity and noise of methods and instruments, but also shows the level of blank (background) value after sample treatment. The detection limit should be determined according to the method adopted. When using instrumental analysis method, the sample with known concentration can be compared with the blank test, and the measured signal intensity S and noise (or background signal) intensity N of the drug to be tested can be recorded, so that the lowest drug concentration of the sample at S/N = 2 or S/N = 3 can be lod. ; The standard deviation of background response can also be obtained by several blank tests, and the standard deviation of three blank tests (that is, 3δ zero or 3s zero) can be used as the estimation value of detection limit. In order to make the calculated lod value consistent with the actually measured lod value, the correction coefficient (F) can be used to correct it, and then the samples with corresponding detection limit concentration can be prepared accordingly, and the lod can be determined through repeated experiments. If non-instrumental analysis method is used, the lowest detectable level is determined as the detection limit by analyzing the samples with known concentration.
4. Quantitative limit
It refers to the lowest concentration of drugs in a sample that can be determined by analytical methods under the premise of ensuring certain accuracy and precision.
It reflects the feasibility of the analytical method in the determination of low drug concentration samples. The difference between it and the above detection limit is that the quantitative limit is the minimum concentration of a drug in the sample medium, and the minimum concentration specified in the quantitative limit should meet certain precision and accuracy requirements. The method of determining the quantity limit also varies with the method used. When non-instrumental analysis method is used, it is the same as the above detection limit; If instrumental analysis method is used, the standard deviation of background response (blank standard deviation) measured by many blank tests is often multiplied by 10 as the estimation value of quantitative limit, and then it is verified by analyzing an appropriate number of samples known to be close to the quantitative limit or prepared with quantitative limit.