Fish quality assessment with ion mobility based gas detector.

Measurement of the mixture of extractable volatile compounds of the gills of vendace was used in the fish freshness evaluation (Coregonus albula L.). MGD-1 gas detector was used for the detection of volatile compound profiles of hexane extracts of gills. The measuring principle of MGD-1 is ion mobility distribution and is based on IMCELL technique. A 2.5 microl sample of hexane extract was heated on a ceramic plate and the vapour was carried with a constant flow (2.5 I/min) of active carbon filtered air to the detector. The ion mobility distribution spectrum was measured every 1 second for 2 minutes. For reference, the microbial counts of gills, ATP-breakdown products (K-value) of fish flesh, electrical properties (Torrymeter scores) of fish skin and sensory evaluation scores were measured. The ion mobility distribution profiles of gills changed significantly during the 7 days storage period The findings related to freshness evaluation were supported by the reference methods. There is, however, a seasonal difference in the freshness probably due to seasonal variation of microbial flora. Besides the evaluation of fish quality, ion mobility distribution based technique provides a new analytical tool for food quality assessment.

Complexometric determination of clodronate in aqueous solutions and urine.

Three different procedures for the determination of clodronate by means of Th-EDTA-XO or Th-DCTA-XO (XO = xylenol orange) complexes are presented. According to the UV-VIS and 13C NMR measurements, XO is quantitatively replaced by the clodronate anion in the mixed ligand Th-EDTA-XO or Th-DCTA-XO complexes in slightly acidic solutions. This ligand replacement reaction can be applied to the determination of traces of clodronate. Procedures studied involve visual complexometric titration, spectrophotometric titration and conventional spectrophotometric determination. By visual complexometric titration it is possible to determine clodronate directly in human urine with acceptable accuracy and precision in the range 0.5-2.5 mg l-1. By diluting more concentrated urine samples 1:10 with water, samples of up to 80 mg l-1 can be determined with acceptable accuracy and precision. The working range of the method is linear up to 16 mg l-1 in aqueous solutions with the RSD-value varying between 0.7 and 3.8%. Interference caused by the major substances of human urine on the determination were studied.