APCI vegetables

Aman, R. et al.. Application of HPLC coupled with DAD, APcI-MS and NMR to the analysis of lutein and zeaxanthin stereoisomers in thermally processed vegetables. Food Chem., 92 753, 2005. 

In addition to HPLC/fluorescence, there are references to the use of both APCI and/or ESI with HPLC/MS for the determination of A/-methyl carbamate insecticides in a variety of matrices." Ongoing studies at the US EPA for the determination of /V-methyl carbamate insecticides in nine fmits and vegetables at the 1.0 ngg level are described below. The fruits and vegetables investigated were cranberries, peaches, blueberries, kiwi, carrots, tomatoes, potatoes, lettuce, and grapefmit juice. The purpose of including an account of this work is to illustrate why HPLC/MS/MS is the method of choice for residue work at the 1.0 ng g level, especially for difficult matrices. 

Liquid chromatography, coupled to the different ionization sources, is generally the technique most used to characterize the phenolic profile in fruit and vegetable products. With regard to the source ionization, it seems that ESI is used more frequently than other sources, such as APCI or APPI. Another important aspect of this technique is the ionization of phenolic compounds. Negative ionization seems to be more suitable... 

Vegetable juice p-carotene isomers, astaxanthin, zeaxanthin, canthaxanthin, echinenone Extraction with MTBE, photo isomerization C-30 MeOH-MTBE HPLC/DAD (450 nm)/MS/ APCI(+) 1 pmol for P-carotene 70... 

This chapter is devoted to the analysis of pesticides and related compounds. LC-MS characteristics of various classes of pesticides are described, i.e., the mass spectral information obtained using electrospray ionization (ESI) and atmospheric-pressure chemical ionization (APCI). Next, typical strategies with the analysis of pesticides in environmental samples and in fmit and vegetables are discussed. 

Barnes and coworkers pioneered in this area. They reported the analysis of diflubenzuron in mushrooms [39], and of diflubenzuron and clofentezine in various fmit drinks [73], and the development of a multiresidue study for ten pesticides in fmit, involving ionization polarity switching in LC-APCI-MS [123]. In these studies, significant attention is paid to matrix-dependent ion suppression or enhancement effects (Ch. 6.7), which is observed even in APCI. Matrix effects in food analysis must be studied in detail for each fmit or vegetable. Obviously, optimization of the sample pretreatment procedures plays an important role in method development for pesticide residue analysis in food. 

C. Blasco, Y. Fic6, J. Manes, G. Font, Determination of fungicide residues in fruits and vegetables by LC-APCI-MS, J. Chromatogr. A, 947 (2002) 227. 

H.R. Mottram, S.E. Woodbury, R.P. Evershed, Identification of TAG positional isomers present in vegetable oils by LC-APCI-MS-MS, Rapid Commun. Mass Spectrom., 11 (1997) 1240. 

The detection and identification of phenolic compounds, including phenolic acids, have also been simph-fied using mass spectrometry (MS) techniques on-hne, coupled to the HPLC equipment. The electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) interfaces dominate the analysis of phenohcs in herbs, fmits, vegetables, peels, seeds, and other plants. In some cases, HPLC, with different sensitivity detectors (UV, electrochemical, fluorescence), and HPLC-MS are simultaneously used for the identification and determination of phenolic acids in natural plants and related food products.In some papers, other spectroscopic instmmental techniques (IR, H NMR, and C NMR) have also been apphed for the identification of isolated phenolic compounds. 

The contamination of fruits and vegetables with pesticides became a problem with the increased application of pesticides because of an intensified agriculture. So the comparison of APCI and ESI-LC-MS for the determination of 10 pesticides of carbamate type (pirimicarb, carbofuran, 3-hydroxycarbofuran, aldicarb, and its metabolites, the sulfoxide and the sulfone), besides others in fruits, met the... 

For the analysis of 10 carbamates in fruits and vegetables a comparison of ESI and APCI-LC-MS switching from positive to negative ionisation was performed (cf APCI carbamates). APCI was more efficient than ESI. Detection Umits were equivalent to 0.002-0.033 mg per kg of crop [358]. Nevertheless, DiCorcia applied ESI-LC-MS(-I-) to analyse 12 N-methylcarbamate insecticides in 10 types of fruits... 

FIGURE 4.28 Positive APCI chromatograms for (a) soybean oil, (b) canola oil, and (c) vegetable shortening. 

For the differentiation of analyzed oil and testing, given the possibility of detecting the presence of vegetable oil blended with VOO, the authors propose the identification of TAG peaks using MS with positive APCI and the calculation of the peak area ratio values, dividing an indicator peak area by a marker peak area. The obtained results clearly show that the peak area ratio values of analyzed oil samples are markedly different and the adulterated VOO samples are detected. Thus, this method is able to detect VOO samples adulterated with 1% of soybean oil and walnut oil, or with 5% of hazelnut oil. The detection threshold for this method is much lower than other LC-MS methods developed previously. 

Ursolic, oleanolic, and betuUnic adds as well as miscellaneous vegetable extracts were developed on RP C18 plates using n-hexane/ethyl acetate (5 1). A TLC-MS approach was employed to confirm the presence of the adds in the plant extracts studied. A CAMAG TLC-MS interface was used for the elution of compounds from TLC plates into the ion trap mass spectrometer with an APCI source. Mass spectra were recorded in negative-ion mode. In order to differentiate between the isomeric ursolic, oleanolic, and betulinic adds by means of MS, tand and triple MS experiments were performed. Betulinic add conld be readily distinguished from ursolic and oleanolic adds. MS/MS/MS spectra of the two latter adds varied mainly in the... 

Typical examples of flavonoid herbs examined by HPLC or CE have already been described in a previous contribution of this volume series [11]. This chapter aims to describe three mass techniques, the electrospray ionization MS, (ESI-MS), atmospheric pressure chemical ionization MS (APCI-MS), and ion trap MS (ITMS) techniques, and their application to the analysis of flavonoids in some standardized herbal extracts with proven therapeutic efficacy. In addition, the flavonoid composition of some commonly consumed vegetables with aromatic or savory properties (culinary herbs) is described. 

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