can we calculate from slope of the linear concenteration
Yes, sensitivity is normally calculated from the slope of the linear calibration curve.
Don't calculate, measure it based on the data obtained. I prefer to start by determining the noise so I can then measure signal to noise ratio's at the lower end of detection. Perform a full calibration over the expected range and determine the best curve fit. Don't extrapolate the results. Interpolate only and be sure and define any LOD's within at least 3 standard deviations.
First, this topic was already discussed before (see link to RG discussion and links in this discussion). Another two articles worth for reading are attached too.
https://www.researchgate.net/post/How_to_calculate_limit_of_detection_limit_of_quantification_and_signal_to_noise_ratio
http://www.cysonline.org/article.asp?issn=2229-5186;year=2011;volume=2;issue=1;spage=21;epage=25;aulast=Shrivastava
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556583/
Detection limit can be calculates using the following formula;
LOD= (k * sb)/m
Where k is chosen to be 2 or 3; k value 2 corresponds to a confident level of 92.1%.. k value 3 corresponds to a confident level of 98.3%. sb is the standard deviation of the blank. and m is the calibration sensitivity that is slope of the linear plot between concentration vs current..
Often we are very interested in lower limit of quantification (LLOQ) to a certain defined precision. This is typically well above the detection limit.
Another issue here is whether the limits are defined as an "amount" or as a "concentration," suggesting that the volume required is also important to characterize performance.
A typical problem with sensors is their imperfect selectivity in complex samples with a varying matrix. This is why chemical sensors tend to be weak performers vs separation based technologies such as chromatography or mass spectrometry.
Few sensors are successful beyond pH, electrolytes, oxygen, peroxide, glucose, and lactate.
Qualitative YES/NO sensors for such things as pregnancy and HIV and syphilis etc. are also very important and successful.
Good points from Peter and Amal. In the field of sensors or/and biosensors, most publications have simplified these crucial parameters. If your sensors are close to a prototype device, then you should really systematically and precisely investigated sensitivity, LOD, and stability.
Ratio signal noise= 3 From slope can calculate the lowest amount detect and just replace the values. See example from biosensor and bioelect paper. As Shelley Minteer said. If you have problem: [email protected]
I am in hollyday
its very easy... please refer to my articles...
Article A Point-of-Care Immunosensor for Human Chorionic Gonadotropi...
Article Development of Highly Sensitive Polysilicon Nanogap with APT...
Agree! And be sure to consider the time response and "real samples" vs. standards and the sample volume required for the measurement. Temperature dependence is also likely to have a considerable influence and response vs. a small range of temperatures is frequently useful to know.
I would recommend that you find the dumbest experiment that you can think of that should give you no response or a textbook response (within the general area of what you want to use the sensor for!). Do it. If it doesn't respond, then you still don't know with certainty, but with more confidence. If it does respond or if it doesn't match the pre-supposed equations... then you are on to something significant.
The sensitivity is then defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is a constant with the units [V/K]. The sensitivity is the slope of the transfer function.
Agree. It is a measure of slope or "response" and is often confused with detection limit.
As many others have pointed out and could also be found in the literature, the general procedure is as follows :
( 1 ) For a particular volume of the analyte / target / biomarker containing solution, create a titration / calibration curve of different concentrations. These will give you the signal responses.
( 2 ) Also determine the blank response using a solution of the same volume but not containing the biomarker you want to detect. This will provide the background response. You can call this as noise.
(3) Next, determine the lowest concentration of the biomarker containing solution which has ratio of signal to noise >= 3. This will give you the limit of detection. The number 3 is derived from statistical calculation.
(4) Sensitivity is defined as the ratio of change in signal to change in concentration. Low value means it is less sensitive to change in concentration of target.
(5) In some literature signal-noise ratio is defined as ( mean of signal response - background response ) / standard deviation of background response. But from my experience, it is rare to use this definition while writing biosensor papers. Hope this will help you.
Dear Manikandan Mayilmurugan
The sensitivity S of a detector is its response y divided by its excitation x.
That is S=y/x,
If the device is nonlinear then one can define the differential sensitivity as Sdiff= dy/dx. There is also a normalized sensitivity Snor= (dy/y)/ (dx/x )
As for the minimum detectable excitation xmin is called the detectivity D of the detector and it is set by the noise in the detector. If the signal is immersed in the noise it could not be directly detected.
Best wishes
Hello Manikandan Mayilmurugan
Generally, the detection limit of a biosensor (probe) can be determined using the formula 3δ/S, where δ denotes the standard deviation of the blank signal and S denotes the slope of the linear calibration plot.
I hope this would be helpful..
Yes!! In the real world there are ambiguities with respect to the requirements of the measurements to support a DECISION of some kind. In a way, there is risk vs. benefit and we often will add a more confident number, such as Lower Limit of
Quantification (LLOQ) to apply in particular circumstances. There also is an ULOQ, helping to define a range of concentrations.
The LOD of a biosensor is the triple times of standard deviation of blank divided by slope of the concentration vs current graph. Sensitivity of a biosensor is the slope of linearity graph divided by the geometry/ active area of biosensor.
Hi Reem Khan
You can follow the following reference to calculate sensitivity
Odeh, A.A., Al-Douri, Y., Voon, C.H. et al. A needle-like Cu2CdSnS4 alloy nanostructure-based integrated electrochemical biosensor for detecting the DNA of Dengue serotype 2. Microchim Acta 184, 2211–2218 (2017). https://doi.org/10.1007/s00604-017-2249-5
Hello everyone, so over the past few years, I have been teaching a course on biosensors and have been constantly looking out for new raw data for students to practice the concepts of LOD, LOQ and decision limits. My question is, is anybody aware of any of the public database where I can find raw data in terms of concentrations, mean and std deviations? Thanks.
the detection limit is 1nM, what does it mean and M is referred to for what?
Akash Verma 1nM means 1 nano Molar. Check this : https://en.wikipedia.org/wiki/Molar_concentration
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