Noise chemical

To give increased sensitivity when the analysis is not limited by chemical noise, eg, in the ms/ms mode, array detectors (15) have been developed. 

The great advantage of SDM over SIM is that it usually confers even greater selectivity onto the analysis and reduces the amount of chemical noise observed. Selected-ion monitoring is concerned with particular... 

The interface generates a significant amount of solvent-associated chemical noise at low mass which makes this region unusable for analytical purposes. Since the ions generated from the analyte are molecular species, this is not usually a problem but must be considered when spectra are being interpreted. 

Chemical noise Signals from species other than the analyte present in the system or sample that cannot be resolved from that of the analyte. 

All f.a.b. spectra are characterized by (a) abundant, pseudomolecular ions for both the sample and the matrix, and (b) a relatively high level of chemical noise, resulting in a signal at every mass number up to the... 

The use of collision-induced dissociation (CID) and MS/MS techniques in conjunction with the API interfaces has dramatically impacted the fleld of environmental analysis. These techniques are now preferred for the determination of triazine compounds in water, soil, crops, etc., owing to the significant improvements in selectivity obtained via the monitoring of precursor-product ion pairs and increased sensitivity due to the reduction of chemical noise. 

It must be considered, though, that limits derived from the SNR characterize mainly instrumental noise and do not, as a rule, include chemical noise, viz such variations of measurement values which come from sample inhomogeneities, sample preparations in the course of the entire analytical... 

Busch, K.L. Chemical Noise in Mass Spectrometry. Part 11 - Effects of Choices in Ionization Methods on Chemical Noise. Spectroscopy 2003,18, 56-62. 

The detection limit is generally limited by electronic and mechanical noise, thermal drift, light source instabilities and chemical noise. But the intrinsic reference channel of the interferometric devices offers the possibility of reducing common mode effects like temperature drifts and non-specific adsorptions. Detection limit of 10 in refractive index (or better) can be achieved with these devices which opens the possibility of development of highly sensitive devices, for example, for in-situ chemical and biologically harmful agent detection. 

More recently, Brennan has shown that FAC-MALDI-MS can be used to screen small molecules, relying upon MRM transitions to overcome the chemical noise generated by the matrix [16]. This is an acceptable approach for known compounds, but for ligand discovery from uncharacterized mixtures, ion selection... 

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