PubMed · 14144153
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A M ROBINSON. 1964. HYPERBARIC OXYGEN UNIT.. https://pubmed.ncbi.nlm.nih.gov/14144153/
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A liquid chromatography-atmospheric pressure photoionization (APPI)-mass spectrometry method was developed for the determination of 22 carbamates including their metabolites in vegetables and fruits. For the optimization of APPI, several APPI ion source parameters were examined. As a result, many carbamates with APPI using the optimized parameter gave simple mass spectra, and a strong signal corresponding to [M + H](+) was observed except for aldicarb. However, some carbamate metabolites gave ammonium adduct ions [M + NH(4)](+) as base peak ions. The mean recovery of each carbamate from grape and onion samples spiked at 5 ng/g was 81.7-105.7%, with relative standard deviations of 3.3-5.9%. Furthermore, matrix constituents did not significantly influence the ionization efficiency. The limit of detection (S/N = 3) in grape and onion was in the range of 0.33-3.33 ng/g. For the robustness of this method, this system has been used to analyze 50 samples, and the intensities for all carbamates were found to be unaffected by the contamination of the APPI source by sample matrix constituents. This result indicates that the method is reliable.
The miniaturized mass-spectrometric detector with atmospheric pressure chemical ionization (APCI) is described. The analyzer employed in this instrument is the monopole with rod 54 mm in length and 2 mm in radius, which retains its efficiency up to 0.13 Pa ( approximately 10(-3)Torr). Together with the ion source, channeltron ion detector, radio frequency power supply and preamplifier, it is packed into a case with dimension of 185 mm x 100 mm x 70 mm. Mass spectrometer with the whole vacuum system weighs about 20 kg. In spite of low power of the vacuum system, the limit of detection at ppt level is achieved. The "strong" fragmentation mode is suggested for high-specific detection of phosphor-containing substances. The detector conforms to multicapillary column attachment.
A simple and rapid simultaneous analytical method of four post-harvest fungicides, o-phenylphenol (OPP), diphenyl (DP), thiabendazole (TBZ), imazalil (IMZ) and its major metabolite R14821 (IMZ-M) in citrus fruits was developed. These compounds were extracted under basic conditions with diethyl ether. The organic layer was washed with water and evaporated at moderate pressure adding methanol. These compounds were determined by liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure photoionization (APPI). The recoveries of the five compounds added to citrus fruits at 1 microg/g ranged from 67 to 100%, with relative standard deviations (R.S.D.) ranging from 2 to 8%. The detection limits (S/N = 3) were 0.01 microg/g and 0.05 microg/g (DP).