Mass spectrometry HPLC detectors

GC-EAD Gas chromatography combined with an EAG detector GC-MS Gas chromatography combined with mass spectrometry HPLC High performance liquid chromatography KI Kovats retention index... 

Natural products and natural-like compounds, generally coming from microbes, plants, sponges and animals [2, 3] may be fully identified and quantified by means of modem and advanced analytical techniques, such as high-performance liquid chromatography (HPLC) coupled to various detectors - from the most common UV/Vis to mass spectrometry and tandem mass spectrometry (HPLC-MS and HPLC-MS/MS). The role of MS is to provide quantitative and qualitative information about mixtures separated by liquid chromatography [4],... 

Notes LOD, limit of detection MeOH, methanol EtOH, ethanol ACN, acetonitrile EtAC, ethyl acetate SPE, solid phase extraction HLB (hydrophilic lipophilic balanced) TFA, trifluoroacetic acid GC, gas chromatography TMS, trimethylsilyl MS, mass spectrometry HPLC, high-performance liquid chromatography DAD, diode array detector NMR, nuclear magnetic resonance ESI, electrospray ionization APCI, atmospheric pressure chemical ionization CE, capillary electrophoresis ECD, electrochemical detector CD, conductivity detector TLC, thin layer chromatography PDA, photodiode array detector. 

The easiest way to perform specificity for any HPLC method is to perform this test in conjunction with a forced decomposition study. The utilization of mass spectrometry (MS) detector (in series) after a Photo Diode Array (PDA) detector to obtain more information is encouraged (in terms of mass-to-charge ratio of parent ions, initial fragmentation pattern, and peak purity). 

When two compounds with very close, or even superimposable, RT and identical UV spectra appear in a chromatogram, it is necessary to use more sophisticated detectors that can yield much more structural information without requiring the isolation of the compounds. One often uses HPLC-mass spectrometry (HPLC-MS) and HPLC-nuclear magnetic resonance (HPLC-NMR). 

Detection methods HPLC-DAD, HPLC with diode-array detection. HPLC-(ESI-MS), HPLC with electrospray ionization mass spectrometry. RP-HPLC, revcrsed-phase HPLC. UPLC/Q-TOFMS, UPLC with quadrupole-time of flight mass spectrometry. HPLC-APCI-MS, HPLC with atmospheric pressure chemical ionization mass spectrometry. CE-IT-MS, capillary elecliophoresis-ion-1r mass spectrometry. LC-ESI-ITMS, liquid chromatography-electrospray ionization ion trap mass spectrometry. LC-ELSD, LC with evaporative light scattering detector. DNBZ-Cl, 3,5-dinitrobenzoyl chloride. 

Figure 1 Steps for determination of organomercury compounds. CV-AAS, cold vapor-atomic absorption spectrometry CV-AFS, cold vapor-atomic fluorescence spectrometry GC, gas chromatography GC-ECD, gas chromatography-electron capture detection AED, atomic emission detector ICP-MS, inductively coupled plasma-mass spectrometry HPLC, high-performance liquid chromatography.

In addition to the spectrometric detectors, HPLC has also been coupled with other detection systems, such as mass spectrometry (MS). Specificity can be highly improved using tandem mass spectrometry (HPLC-MS/MS) (Holler et al. 2006 Yomota and Ohnishi 2007). High sensitivity and selectivity can also be achieved by HPLC coupled with electrochemical detection (Kucera et al. 2007). 

UV detection is used in most chiral analysis by HPLC and other liquid chromatographic modalities. However, some other detectors, such as conductivity, fluorescent and refractive index types, are also used. The choice of detector depends on the properties of the racemic compound to be resolved [41, 144]. Chiroptical detectors, which are based on the principle of polarimetry [145] or circular dichroism [146, 147], are also available. The enantiomer (+)- or (—)-notation is determined by these detectors. Some organochlorine pesticides are not UV-sensitive, and hence they are difficult to detect in liquid chromatography. The detection of these types of pollutant can be achieved by using a mass spectrometry (MS) detector, and therefore LC-MS instruments are now being put on the market for routine use [148, 149]. 

Table 28-1 lists the most common detectors for HPLC and some of their most important properties. The most widely used detectors for LC are based on absorption of ultraviolet or visible radiation (see Figure 28-8). Fluorescence, refractive-index, and electrochemical detectors are also widely used.. Mass spectrometry (MS) detectors are currently quite popular. Such LC/MS systems can greatly aid in identifying the analytes exiting from the HPLC column as discussed later in this section. 

Some High-Performance Liquid Chromatography (HPLC) Procedures for the Determination of Multiple Classes of Food Flavonoids with Electrochemical (ECD), Fluorimetric, and Mass Spectrometry (MSD) detectors ... 

Detectors Most of the detectors used in HPLC also find use in capillary electrophoresis. Among the more common detectors are those based on the absorption of UV/Vis radiation, fluorescence, conductivity, amperometry, and mass spectrometry. Whenever possible, detection is done on-column before the solutes elute from the capillary tube and additional band broadening occurs. 

The recent development and comparative application of modern separation techniques with regard to determination of alkylphosphonic acids and lewisite derivatives have been demonstrated. This report highlights advantages and shortcomings of GC equipped with mass spectrometry detector and HPLC as well as CE with UV-Vis detector. The comparison was made from the sampling point of view and separation/detection ability. The derivatization procedure for GC of main degradation products of nerve agents to determine in water samples was applied. Direct determination of lewisite derivatives by HPLC-UV was shown. Also optimization of indirect determination of alkylphosphonic acids in CE-UV was developed. Finally, the new instrumental development and future trends will be discussed. 

Coupling of analytical techniques (detectors) to high-performance liquid chromatographic (HPLC) systems has increased in the last tree decades. Initially, gas chromatography was coupled to mass spectrometry (MS), then to infrai ed (IR) spectroscopy. Following the main interest was to hyphenate analytical techniques to HPLC. 

ECD = electron capture detector GC = gas chromatography HPLC = high-performance liquid chromatography MC = microcoulometric detector MS = mass spectrometry NICI = negative ion chemical ionization RSD = relative standard deviation SPE = solid phase extraction... 

D2O = deutered water. HPLC = high performance liquid chromatography. IS = internal standard. MeOH = methanol. MS = mass spectrometry. NMR = nuclear magnetic resonance. PDA = photodiode array detector. TEA = triethylamine. MTBE = methyl tert-butyl ether. 

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