Many reagent tests involve the problem of the standard curve. The quality of the standard curve will directly affect the results of the experiment, and even related to the success or failure of the experiment, so how to draw or make a standard curve? 1. There are several issues to be noted when doing standard curve sample testing 1. The sample concentration and other indicators are calculated based on the standard curve, so first of all, the standard curve should be regarded as a more important thing than the formal experiment, otherwise the results of the subsequent experiments will not be discussed. 2. Set the standard concentration range of the standard curve sample to have a larger span, and to cover the concentration of the experimental sample you want to detect, that is, the sample concentration should be within the standard curve concentration range, including the upper and lower limits. For the S-shaped standard curve, try to make the concentration of the test sample in the middle of the steepest slope, that is, the curve is almost in a straight line. 3. It is best to use the ratio dilution method to prepare the concentration of the standard sample in the standard curve, so as to ensure that the concentration of the standard sample does not deviate greatly. 4. When testing standard samples, the concentration should be increased in order to reduce the effect of high concentration on low concentration and improve accuracy. 5. The number of samples of the standard curve is generally 7 points, but at least 5 points must be guaranteed. 6. The correlation coefficient of the standard curve is changed due to different experimental requirements, but in general, the correlation coefficient R is at least greater than 0.98, and for some experiments, at least 0.99 or even 0.999. Second, what equation to choose to fit The so-called "standard curve" used for immunoassays is actually called a fitting curve. It is of course ideal if the concentration of the standard point (which may be multiply diluted or not) during immunodetection and the corresponding absorbance (OD) value can present a linear relationship. At this time, the fitting can be conveniently obtained by EXELL etc. Curve, and then calculate the concentration value of the sample. However, we rarely do immunoassay. Sometimes, such an ideal situation can occur. The concentration of the standard and the corresponding OD value are often "S" -shaped curves. At this time, we cannot use the straight line fitting method. It is necessary to make a choice. Regarding the fitting method of standard curve, although straight line, quadratic curve, cubic curve, exponent, logarithm, etc. can be used for curve fitting in ELISA and other biological reactions, they are only applicable to part of the curve, and some are applicable. In the first half, some apply to the second half, some apply to the middle, and the logistic curve has a good applicability to all the curves. Of course, if it is used for quantification, it is better to be in the middle. Although none of these methods are universal, they can also be used. The key lies in which part of your standard curve is S-shaped, and which part of the curve you want to detect. The low-concentration part of the S curve can be fitted with a power equation, the low- and medium-concentration part can use a straight line equation, the middle part can use a logarithmic equation, and the middle and rear sections can use four parameters. At present, the most popular fitting method for immunoassay in the world is "four-parameter logic fitting". This fitting method can often accurately reflect the curve relationship between concentration and absorbance, so as to further obtain the substance to be tested in the sample more correctly. Concentration value. In fact, in a long interval, Logistic should fit perfectly. But it's not that it is omnipotent. In fact, not only ELISA, but many other biological reactions are S-shaped curves, which can also be fitted with Logistic curves. But building a model is one thing, and using it to quantify is another. If it is used for quantification, the middle part (the steeper part) of the S-shaped curve is better, and the calculation error of the flat parts at both ends will be large, sometimes even large. Windmill Bird Repeller,Bird Scarer Windmill,Bird Deterrent Windmill,Windmill Bird Scarers Hebei Liebang Metal Products Co.,Ltd , https://www.lbtraps.com