Now showing items 1-4 of 4

    • Article

      Analysis of nitrite in aqueous solutions containing concentrated matrix ions using an octadecyl-poly(vinyl alcohol) gel microbore column and an electrochemical detector 

      S Rokushika, K Kihara, FM Yamamoto & PF Subosa - Journal of High Resolution Chromatography, 1991 - Dr. Alfred Huethig Publishers
      The importance of the analysis of low level nitrite concentrations in aqueous samples is increasing in various fields such as environmental, food, and aquaculture chemistry. Recent progress in ion chromatography paved the way to the direct analysis of nitrite in water samples at ppm to sub ppb levels. However, analysis of low level nitrite in highly concentrated salt matrix still remains a difficult problem. The presence of a large amount of the matrix ion makes establishment of an ion exchange equilibrium very difficult in the column, often resulting in bad peak shapes [1].

      In previous papers, we reported the analysis of a nitrite and other anions in chloride matrix on a conventional low capacity anion-exchange column by means of a heart-cut and recycling method [1] and by using a potassium chloride eluent [2]. To monitor the nitrite peak, both a UV detector and a conductimetric detector has been used [3]. Several groups have demonstrated the potential of an electrochemical detector for a specific and sensitive detection of nitrate. [4-6].

      Poly(vinyl alcohol) (PVA) gel have been introduced recently as a chemically stable HPLC column packings [7-9]. It was found that when an acidic eluent was employed, a PVA gel and its acylated gel columns produced large capacity factors for nitrite [10].
    • Article

      Ion chromatography of inorganic anions in brine samples 

      PF Subosa, K Kihara, S Rokushika, H Hatano, T Murayama, T Kubota & Y Hanaoka - Journal of Chromatographic Science, 1989 - Oxford University Press
      An ion chromatographic method for separating and detecting anions in brine samples is described. Nitrite, bromide, nitrate, and sulfate ions in brine samples are well separated when chloride ion concentration in the sample solution is below 2000 ppm. However, at higher chloride concentrations, nitrite and chloride peaks are not resolved. Low level nitrite ion in the brine sample is separated from a major chloride ion by a heart-cutting and recycling system. After elution, the unresolved portion, including the nitrite ion, is cut and trapped in a 10-mL sample collecting loop and reinjected on the column by using 6- and 4-port valve systems. The detection limit of nitrite spiked in the seawater samples is 0.5 ppm.
    • Article

      Ion chromatography of nitrite, bromide and nitrate ions in brine samples using a chloride-form anion-exchange resin column 

      S Rokushika, K Kihara, PF Subosa & WX Leng - Journal of Chromatography A, 1990 - Elsevier
      In aquaculture research, maintenance of water culture quality is of great importance. Recent improvement in fishpond management and fish culture systems, such as intensive feeding and fertilization, have created complex problems. Deterrioration of weter quality is primarily the resulting effect of these improvements. Foe example, high-protein feeds and nitrogen fertilizers applied in fishponds produce considerable amount of nitrate in the water. Moreover, their synergistic effects cannot be ignored. Hence the routine determination of nitrite in fishpond water is required.

      Since its introduction by Small et al., ion chromatography has been widely used for the determination of ions in water. However,the presence of very high concentrations of chloride is the main obstacles in the analysis of seawater samples, affecting the separation and detection not only of nitrite but also of other anions.

      Itoh and Shinbori applied ion chromatography to the analysis of seawater using a 125-cm long column and a conductimetric detector. This technique provided by a simple and sensitive analysial method for brine samples. However, nitrite could not be determined owing to the presence of a large chloride peak.

      Attempts to determine nitrite in seawater also led to innovations in the methodology. Lee and Field employeed a post-column cerium flourescence detection system to determine nitrite and nitrite in drinking water and seawater. The use of a pretreatment column in the silver form for removal of chloride has been reported.

      Various detectors have been applied in ion chromatography in addition to the conductimetric detector. The UV detector has been shown to be luseful detector for several kinds of inorganic anions. Selected detection of specified inorganic ions can be achieved by tuning the wavelength of the UV detector in ion chromatography and also in ion-exclusion chromatography. The elemination of the chloride matrix interference in the sub-ppm determination of nitrite in seawater was achieved by a heart-cutting and recycling method using a dual detection system consisting of conductimetric and UV detectors. This method, however, requires valve switching during analysis and needs a long analysis time.

      This paper describes a simple and rapid method of UV-absorbing anions, such as nitrite, nitrite and bromide, in brine samples using a chloride-form anion-exchange resin column combined with a UV detector.
    • Article

      Mycoflora of the 'green water' culture system of tiger shrimp Penaeus monodon Fabricius 

      EM Leaño, GD Lio-Po, LA Nadong, AC Tirado, RB Sadaba & NG Guanzon - Aquaculture Research, 2005 - Blackwell Publishing Ltd
      This study was conducted to quantify and characterize the mycoflora associated with the ‘green water’ culture system of Penaeus monodon. Samples of water, tilapia gut and mucus, and shrimp hepatopancreas from three shrimp farms were collected during 15, 30, 45 and 60 days of culture (DOC). Results showed that high fungal loads were observed in tilapia gut (total: 117–1352 colony forming unit (CFU) 5 cm hind gut−1; yeasts: 0–136 CFU 5 cm hind gut−1) and mucus (total: 12–311 CFU (5 cm2)−1; yeasts: 0–88 CFU (5 cm2)−1), while minimal fungal populations were observed in water samples (total: 0–110CFU mL−1; yeasts: 0–5 CFU ml−1). Shrimp hepatopancreas harboured a very low number of filamentous fungi (0–27 CFU 0.1 g−1) and yeasts (0–7CFU 0.1 g−1) especially at 60 DOC. The filamentous fungal isolates were dominated by Penicillium and Aspergillus species, while the yeast populations were dominated by Rhodotorula and Saccharomyces species. The dominance of these fungi on tilapia mucus and gut and their presence in the rearing water might play an important role in the overall mechanisms involved in the control of luminous Vibrio in the ‘green water’ grow-out culture of P. monodon.