Reproducibility is a measure of how repeatable results are. There are several factors that have an impact on the reproducibility of results.
On a high level, there is:
A. reproducibility of the instrument measurement, which is influenced by the instrument design
B. reproducibility of the testing method, which is influenced by the testing method design
Reproducibility of results is influenced by ow repeatable:
1. your sample preparation is (hence it is important to always use a uniform representative sample),
2. your extraction and dilution solvent measurements are
3. your extraction times are
4. your injection technique is - therefore it is important to avoid having any bubbles in the injection syringe and always inject at a minimum 3x20uL (sample loop volume)
5. mobile phase is - pH, composition
6. instrument settings are - flow rates, temperatures
7. instrument itself - pump, column, detector
In the context of reproducibility, we will be considering everything constant and will consider only the instrument by injecting the same sample several times to judge the reproducibility.
Reproducibility is expressed as a relative standard deviation (RSD), which is a measure of variation and distribution of numbers, in our case results obtained.
In the world of analytical chemistry, RSD is highly dependent on where the measure is done - at the low end of the signal, middle, or the high end. High end (upper limit of calibration curve) and the middle tend to be more accurate with typical RSD 5% - 10%, while at the low end (lower limit of detection), the common RSDs are 10% - 20%.