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Volatiles from Russet Burbank potatoes inoculated with Erwinia carotovora subsp. carotovora, E. carotovora subsp. atroseptica, Pythium ultimum, Phytophthora infestans, or Fusarium sambucinum were monitored by sampling the head space 3, 4, and 5 days after inoculation, using a solid phase microextraction (SPME) fiber to trap and gas chromatography with flame ionization detector (GC-FID) to fingerprint volatiles. Noninoculated (NON) potatoes served as the control. Volatile fingerprints varied among diseases. Within a disease, the fingerprints varied with time since inoculation and among blocks. In general, more volatiles were observed on the fourth and fifth day after inoculation than on the third day. The amount of volatile compounds produced (peak area) within a disease group increased with incubation time; however, the variation among blocks was much higher. The amount of volatiles produced, in general, was associated with disease severity. Disease-specific volatiles were observed. The F. sambucinum chromatogram had two unique peaks at retention time (RT) = 14.1 and 17.3 min. P. infestans produced few peaks and the profile was quite similar to NON. In contrast, E. carotovora subsp. carotovora, E. carotovora subsp. atroseptica, and Pythium ultimum produced many peaks, and the P. ultimum was different from the bacteria, in that the chromatogram peaks at RT = 4.04 and 8.76 min were absent. Instead, it produced a distinct peak at RT = 1.71 min. E. carotovora subsp. carotovora and E. carotovora subsp. atroseptica couldn't be discriminated based on unique peaks; however, they varied in concentration of volatiles produced. E. carotovora subsp. carotovora produced more of RT = 2.0 min and less of RT = 2.3 and 2.44 min than E. carotovora subsp. atroseptica. A back-propagation network (using neural networks) was developed to classify volatile profiles into six disease-groups. Cross-validation classification probabilities were NON = 71, E. carotovora subsp. carotovora = 71, E. carotovora subsp. atroseptica = 71, P. ultimum = 67, Phytophthora infestans = 46, and F. sambucinum = 75%.

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Volatile metabolites from headspace gas of carrot cv. Vita-treat inoculated with water or four different pathogens Botrytis cinerea, Erwinia carotovora subsp. carotovora, Aspergillus niger and Fusarium avenaceum were profiled using gas chromatography and mass spectrometry to develop a technology to discriminate diseases. The inoculation of carrot roots with water or different pathogens released a total of 137 different volatile metabolites. Among them, 39 compounds were relatively consistent and 11 were specific to one or more diseases/ inoculations. E. carotovora subsp. carotovora produced seven disease-specific metabolites: 1-butanol, 3-methyl; 1-pentanol; 1-propanol, 2-methyl; 2,3butanedione; boronic acid, ethyl; butane, 1-methoxy-3-methyl; and ethane, ethoxy. Some metabolites were disease/inoculation discriminatory and were not detected in all treatments: 1,2-dimethoxy-ethene was common in carrots inoculated with E. carotovora subsp. carotovora and B. cinerea, while 2-butanone, 3-chloro-4-hydroxy-1,4-diphenyl was common in carrots inoculated with E. carotovora subsp. carotovora, F. avenaceum and water-inoculated control. The significant mass ions, based on univariate analysis, from a total of 150 (46-195 m/z) and compounds from a total of 32 were further subjected to stepwise discriminant analysis and discriminant analysis. The models for 3 days after inoculation (DAI) were better than those for 6 DAI and 3 + 6 DAI, where up to 90% of the observations were correctly classified into respective inoculations. The disease-discriminatory compounds from different diseases/inoculations and discriminant analysis models developed here have the potential for the early detection and discrimination of postharvest diseases of carrot cv. Vita-treat, after validation under commercial conditions.

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An ultra performance liquid chromatography-tandem mass spectrometric method, with modified QuEChERS method for sample preparation, was developed for the determination of the 4 kinds of 29 banned and restricted veterinary drugs in chicken muscle, chicken liver, porcine muscle and porcine liver samples. The drugs were extracted with McIlvaine buffer solution and acetonitrile, then cleaned-up by modified QuEChERS method, and finally analyzed by ultra performance liquid chromatography-tandem mass spectrometry in multiple reaction monitoring mode via positive electrospray ionization. The method was validated at three fortification levels (LOQ level, 20 µg/kg and 50 µg/kg) in chicken muscle, chicken liver, porcine muscle and porcine liver samples. The validation results were as follows. The correlation coefficients of the standard calibration curves for the 29 veterinary drugs were all between 0. 993 and 0. 999 over their own concentration ranges. The average recoveries of the 29 drugs were between 71. 5% and 93. 2%, with the relative standard deviations (RSDs) between 0. 8% and 7. 7%. The limits of determination (S/N=3) of the drugs were between 0. 3 and 3. 0 µg/kg. The limits of quantification (S/N≥10) were 1. 0 µg/kg for amantadine, 10.0 µg/kg for the tetracycline drugs, and 5. 0 µg/kg for all the other drugs. It was indicated that the method developed is easy, sensitive, and has a good purification effect. The sensitivity, accuracy and precision of the method were all acceptable, and it can meet the requirements of the multiple residue analysis. So, this method can be further applied to investigate the veterinary drug residues in animal derived foods.