Noise and drift
In HPLC we deal with the time-dependent process. The appearance of the component from the column in the detector represented by the deflection of the recorder pen from the baseline. It is a problem to distinguish between the actual component and artifact caused by the pressure fluctuation, bubble, compositional fluctuation, etc. If the peaks are fairly large, one has no problem in distinguishing them. However, the smaller the peaks, the more important that the baseline be smooth, free of noise, and drift.
Baseline noise is the short time variation of the baseline from a straight line caused by electric signal fluctuations, lamp instability, temperature fluctuations and other factors. Noise usually has much higher frequency than actual chromatographic peak. Noise is normally measured "peak-to-peak": i.e., the distance from the top of one such small peak to the bottom of the next. Sometimes, noise is averaged over a specified period of time. Noise is the factor which limits detector sensitivity. In trace analysis, the operator must be able to distinguish between noise spikes and component peaks. A practical limit for this is a 3 x signal-to-noise ratio, but only for qualitative purposes. Practical quantitative detection limit better be chosen as 10x signal-to-noise ratio. This ensures correct quantification of the trace amounts with less than 2% variance. Figure below illustrates this, indicating the noise level of a baseline(measured at highest detector sensitivity) and the smallest peak which can be unequivocally detected.
Definition of noise, drift, and smallest detectable peak.
Another parameter related to the detector signal fluctuation is drift. Noise is a short-time characteristic of a detector, an additional requirement is that the baseline should deviate as little as possible from a horizontal line. It is usually measured for a specified time, e.g., 1/2 hour or one hour. Drift usually associated to the detector heat-up in the first hour after power-on. Figure also illustrates the meaning of drift.
absorbance units full scale
higly unretainable and has high absorption at 260 nm
Random changes.This would be called genetic drift.
I think you mean genetic drift. Genetic drift is not strong enough in itself to cause speciation generally. Genetic drift is merely a sampling error in allele frequency change due to random events.
Blood groups are affected by genetic drift randomly, making it special.
to calculate signal to noise use this formulae peak hight *2/noise level
Unstbilized column will deviate baseline as little as possible from a horizontal line
NP-HPLC is "Normal Phase" HPLC, wherein the solvents used are less polar than the substrate in the HPLC column (e.g. using hexane or dichloromethane with a silica HPLC column). RP-HPLC is "Reverse-Phase" HPLC, wherein the solvents used are more polar than the substrate in the HPLC column (e.g. using Water and Methanol with a octadecylsilane (ODS or C18) column).
HPLC is advanced
why RT was shifting & how to RT calculation in HPLC
HPLC columns. (HPLC - High Performance Liquid Chromatography.)
Answer: HPLC standards are an indispensible tool for analytical HPLC applications. They are used to monitor column performance & calibrate detector response.
mixture of enantiomers can be separated by HPLC
"RS-HPLC method" means "Related Substance HPLC Method".
GLC has a stationary liquid phase and gas moving phase HPLC had a stationary solid phase and liquid moving phase HPLC is done under high pressure. HPLC can be used for thermally unstable compounds as opposed to GLC HPLC can be used for polar or low volatile compounds as opposed to GLC
You can purchase used HPLC detectors and other equipment from the usedhplc website or from the ebay bidding website. Alternatively you can buy HPLC detectors from the equipnet website.
The Time-Taken the sample Or elute in the column is called the retention time in hplc.