Gradient blank signal

A blank signal is usually inevitable in a gradient run, due to contaminations in the weaker solvent. Therefore, a blank experiment needs to be performed and the results of the actual experiment need to be compared with the blank (see also figure 6.6). 

The program starts and ends at the purge segment (P). The reason for this is related to the typical baseline observed in a gradient elution LC experiment (figure 6.6b). Unlike the situation in GC, the main cause of the blank signal in programmed solvent LC is formed... 

Figure 5.14 Gradient elution chromatogram of a mixture of phenolic solutes. The six numbered peaks refer to the sample. The remaining signals to the blank. Linear gradient 0 — 100% methanol in water. /0=125 s. Figure taken from ref. [536]. Reprinted with permission.

Figure 6 Positive ion atmospheric pressure chemical ionization (APCI) LC-MS analyses of (A) hexane extract of 200 fiL of human serum, and (B) solvent blank showing no signals at m/z 269. The computer-reconstructed mass chromatogram at m/z 269 is shown from the full-scale data. The HPLC solvent system consisted of a 25 min linear gradient from 50 44.5 5 0.5 to 50 4.5 45 0.5 methanol/water/methyl-tert-butylether/acetic acid (v/ v/v/v). (From Ref. 310.)...

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