The ascorbic acid (or vitamin C) content of the fruits and vegetables grown in the district of Trabzon (Turkey) was determined by UV−vis spectrophotometry. Fe, Cu, and Zn contents of the same materials were measured by atomic absorption spectrophotometry, and a comparison was made between the values of local and imported produce. Keywords: l-Ascorbic acid; iron; copper; zinc; determination; dry-ashing; atomic absorption; spectrophotometry; vegetable; fruit

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Electron Impact Mass Spectra of some 1,2,4Oxadiazole and Oxadiazine DerivativesAs a part of our on-going research on the molecular rearrangement of 1,2,4-oxadiazoles and oxadiazines several compounds of this type have been prepared' and their activities are being examined.* Some of these compounds, especially those bearing a sulphur atom are well known to exhibit a wide range of biological a~tivities.~ We wish to report here electron impact (EI) mass spectra of these compounds for which few data are available in the literature.The EI mass spectra of the compounds 1 and 2 were recorded on a Finnigan MAT 90 instrument and an AEI MS 9 instrument with a 70 eV ionization energy. The relative abundances of the principal fragment ions are shown in Table 1.The expected fragmentation pathway of 1,2,4-oxadiazoles under EI is the retro-1,3-dipolar cycloaddition to form a nitrile (RCN) and a nitrile oxide (RCNO) as complementary ions.4 In this way, for compounds 1 the fragments at m/z 103 (la, lc), 41 (lb) and 119 (la, lc), 57 (lb) can be assigned to the corresponding nitriles and nitrile oxides, respectively. The base peak for la is observed as RCNO whereas in the case of lb, to which an amidoxime group is attached, it is at m/z 98. This might be attributed nominally to the generation of 3,5dimethyl-1,2,4-oxadiazole during the bond cleavage between the amidoxime moiety and the exocyclic methylene followed by a hydrogen transfer. The same assumption may be valid for lc that has also a peak at m/z 160 with lower intensity. The base peak for lc is recorded at m/z 105 which might be regarded as PhCHNH' (benzaldehyde iminium cation).'