Atmospheric-pressure chemical analysis

B. Herbreteau, A. Salvador, M. Lafosse and M. Dreux, SFC with evaporative lightscattering detection and atmospheric-pressure chemical-ionisation mass specti ometiy for methylated glucoses and cyclodextiins analysis, Analusis 27 706-712 (1999). 

A number of analytical techniques such as FTIR spectroscopy,65-66 13C NMR,67,68 solid-state 13 C NMR,69 GPC or size exclusion chromatography (SEC),67-72 HPLC,73 mass spectrometric analysis,74 differential scanning calorimetry (DSC),67 75 76 and dynamic mechanical analysis (DMA)77 78 have been utilized to characterize resole syntheses and crosslinking reactions. Packed-column supercritical fluid chromatography with a negative-ion atmospheric pressure chemical ionization mass spectrometric detector has also been used to separate and characterize resoles resins.79 This section provides some examples of how these techniques are used in practical applications. 

The most recent progress in MS analysis of chlorophylls has been obtained with the development of atmospheric ionization methods such as atmospheric pressure chemical ionization (APCl) and electrospray ionization (ESI). These techniques have demonstrated much more sensitivity than thermospray ionization, detecting chloro-... 

Polymeric precolumns of styrene-divinylbenzene were used by Aguilar et al. to monitor pesticides in river water. Water samples (50 mL) were trace enriched on-line followed by analysis using LC combined with diode-array detection. LC atmospheric pressure chemical ionization (APCI) MS was used for confirmatory purposes. It was found that after the pesticides had been extracted from the water sample, they could be stored on the precartridges for up to 3 months without any detectable degradation. This work illustrates an advantage of SPE for water samples. Many pesticides which may not be stable when stored in water, even at low temperature, may be extracted and/or enriched on SPE media and stored under freezer conditions with no detectable degradation. This provides an excellent way to store samples for later analysis. 

Desai,M.J., Armstrong, D.W. (2004). Analysis of native amino acid and peptide enantiomers by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. J. Mass. Spec. 39, 177-187. 

A range of MS ionisation techniques are available. Atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI) are becoming the methods of choice for the analysis of low molecular weight additives of mass/ charge (m/z) ratio <3,000. 

For confirmatory assay, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is becoming more frequently used in the analysis of OTC owing to its high sensitivity and ability. Electrospray ionization (ESI) [55-57] and atmospheric pressure chemical ionization (APCI) [41] methods combined with tandem mass spectrometry are favored because of their higher sensitivity and better reproducibility. Hamscher et al. [58] developed a method for the determination of persistent TC residues in soil fertilized with manure by HPLC tandem mass spectrometry, MS-MS, and confirmation by MS-MS-MS. Zhu et al. [59] developed an LC-tandem mass spectrometry for the analysis of common tetracyclines in water. The detection limit for oxytetracycline was 0.21 pg/L. Lykkeberg et al. [60] used LC-MS/MS for determination of oxytetracycline and its impurities EOTC, TC, ETC, ADOTC, oc-AOTC, and /i-AOTC. 

G.A. van der Doelen, K.J. van den Berg, J.J. Boon, N. Shibayama, E.R. de la Rie, W.J.L. Genuit, Analysis of fresh triterpenoid resins and aged triterpenoid varnishes by high performance liquid chromatography atmospheric pressure chemical ionisation (tandem) mass spectrometry, Journal of Chromatography A, 809, 21 37 (1998). 

For the last several years, mass spectrometry with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) have determined the trends in the analysis of dyes. Since 1987, various variants of ESI have been used in which droplet formation was assisted by compressed air,[1,2] temperature (e.g. Turbo Ion Spray ) or ultrasound, and they were able to handle flow rates up to 1 2 ml min This made a combination of analytical RPLC and ESI easily and widely used. The reason why it often was (and is) used instead of a traditional UV-Vis detector is the better sensitivity and selectivity of MS in comparison with spectrophotometric detection. Apart from these advantages, MS offers easily interpretable structural information. However, various... 

DGE a AC AMS APCI API AP-MALDI APPI ASAP BIRD c CAD CE CF CF-FAB Cl CID cw CZE Da DAPCI DART DC DE DESI DIOS DTIMS EC ECD El ELDI EM ESI ETD eV f FAB FAIMS FD FI FT FTICR two-dimensional gel electrophoresis atto, 10 18 alternating current accelerator mass spectrometry atmospheric pressure chemical ionization atmospheric pressure ionization atmospheric pressure matrix-assisted laser desorption/ionization atmospheric pressure photoionization atmospheric-pressure solids analysis probe blackbody infrared radiative dissociation centi, 10-2 collision-activated dissociation capillary electrophoresis continuous flow continuous flow fast atom bombardment chemical ionization collision-induced dissociation continuous wave capillary zone electrophoresis dalton desorption atmospheric pressure chemical ionization direct analysis in real time direct current delayed extraction desorption electrospray ionization desorption/ionization on silicon drift tube ion mobility spectrometry electrochromatography electron capture dissociation electron ionization electrospray-assisted laser desorption/ionization electron multiplier electrospray ionization electron transfer dissociation electron volt femto, 1CT15 fast atom bombardment field asymmetric waveform ion mobility spectrometry field desorption field ionization Fourier transform Fourier transform ion cyclotron resonance... 

In off-line coupling of LC and MS for the analysis of surfactants in water samples, the suitability of desorption techniques such as Fast Atom Bombardment (FAB) and Desorption Chemical Ionisation was well established early on. In rapid succession, new interfaces like Atmospheric Pressure Chemical Ionisation (APCI) and Electrospray Ionisation (ESI) were applied successfully to solve a large number of analytical problems with these substance classes. In order to perform structure analysis on the metabolites and to improve sensitivity for the detection of the various surfactants and their metabolites in the environment, the use of various MS-MS techniques has also proven very useful, if not necessary, and in some cases even high-resolution MS is required. 

Several years later, the next step in the application of MS-MS for mixture analysis was developed by Hunt et al. [3-5] who described a master scheme for the direct analysis of organic compounds in environmental samples using soft chemical ionisation (Cl) to perform product, parent and neutral loss MS-MS experiments for identification [6,7]. The breakthrough in LC-MS was the development of soft ionisation techniques, e.g. desorption ionisation (continuous flow-fast atom bombardment (CF-FAB), secondary ion mass spectrometry (SIMS) or laser desorption (LD)), and nebulisation ionisation techniques such as thermospray ionisation (TSI), and atmospheric pressure ionisation (API) techniques such as atmospheric pressure chemical ionisation (APCI), and electrospray ionisation (ESI). 

The qualitative determination of anionic surfactants in environmental samples such as water extracts by flow injection analysis coupled with MS (FIA-MS) applying a screening approach in the negative ionisation mode sometimes may be very effective. Using atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI), coupled with FIA or LC in combination with MS, anionic surfactants are either predominantly or sometimes exclusively ionised in the negative mode. Therefore, overview spectra obtained by FIA—MS(—) often are very clear and free from disturbing matrix components that are ionisable only in the positive mode. However, the advantage of clear... 

For sensitive quantification in LC-MS analysis of non-ionic surfactants, selection of suitable masses for ion monitoring is important. The nonionic surfactants easily form adducts with alkaline and other impurities present in, e.g. solvents. This may result in highly complicated mass spectra, such as shown in Fig. 4.3.1(A) (obtained with an atmospheric pressure chemical ionisation (APCI) interface) and Fig. 4.3.2 (obtained with an ESI interface). 

Negative atmospheric pressure chemical ionization (APC) low-energy collision activation mss spectrometry has also been employed for the characterization of flavonoids in extracts of fresh herbs. Besides the separation, quantitative determination and identification of flavonoids, the objective of the study was the comparison of the efficacy of the various detection systems in the analysis of flavonoids in herb extracts. Freeze-dried herbs (0.5g of chives, cress, dill, lovage, mint, oregano, parsley, rosemary, tarragon and thyme) were ground and extracted with 20 ml of 62.5 per cent aqueous methanol. After sedimentation the suspension was filtered and used for HPLC analyses. Separations were carried out in an... 

With the development of sophisticated ionization techniques including electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), HPLC-MS techniques have been successfully applied to the online analysis of ginsenosides in extracts and biological fluids (Fuzzati, 2004). In terms of sensitivity and specificity, an MS detector is better than UV or ELSD. Among the various MS methods, the HPLC-MS-MS (or just LC-MS-MS) technique is to date the most sensitive method for detection and quantification of ginsenosides. 

Atmospheric Pressure Chemical Ionization (APCI)/MS APCI/MS is used to analyze compounds of intermediate molecular weight (100-1,500 da) and intermediate polarity and is particularly useful for the analysis of biochemicals such as triacylglycerides, carotenoids, and lipids (Byrdwell, 2001). For volatile, nonpolar compounds of low molecular weight, GC/MS is preferred to APCl/MS whereas APl-electrospray/ MS provides better results for larger, more polar materials. The selection of APCl/MS over GC/MS or APl-electrospray/MS depends on the compounds to be analyzed. Many LC/MS instruments can be easily switched between APCl/MS and APl-electrospray/MS so that it can be rapidly determined which ionization process is more suitable to a given chemical. Additional manipulations such as pre and postcolumn derivatization reactions (Nagy et al., 2004 Peters et al., 2004) or coulometric oxidation (Diehl et al., 2001) can make the chemicals of interest more amenable to detection by APCI. 

Backstrom B, Cole MD, Carrott MJ, Jones DC, Davidson, G, et al. 1997. A preliminary study of the analysis of Cannabis by supercritical fluid chromatography with atmospheric pressure chemical ionization mass spectroscopic detection. Sci Justice 37 91. 

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