This review describes applications of flow analytical systems to the determination of trace components in seawater samples. Determination of trace components is important to understand the mass circulation, and to evaluate the degree of pollution, however, the trace analysis of seawater is not an easy task because of high salinity of the seawater. The flow analytical system can be solutions for preconcentration of analytes in addition to separation of matrix. Various applications of flow analytical systems for the analysis of seawater are classified with their detection methods.
A flow injection (FI) system is presented for simple, rapid and sensitive determination of bromate at sub ppm levels in salts. In order to achieve highly sensitive and selective determination of bromate in salts, the anion-exchange separation/preconcentration of bromate using 1.0 M NaCl as an eluent was developed and directly in-line coupled with spectrophotometric detection at 592 nm based on the bromate oxidation of V (IV) and complex formation of resulting V (V) with Nitro-PAPS [2-(5-Nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)-phenol] in a flow injection system. The present FI system offers many advantages with respect to simplicity and sensitivity, with a short analysis time (about 10 min), low limit of determination (0.05 ppm) in salts, and good reproducibility (rsd<3%). The results for analysis of commercially available sea salts (11 samples) and imported solar salts (4 samples) using the present FI system have revealed that BrO3-contents in all of these samples are less than 0.05 ppm.
The conditions for concentrating trace sulfate ion in sodium chloride reagent using a zirconium-loaded cation exchange resin cartridge were examined. Sulfate ion contents were determined by means of ion chromatography after sulfate ion preconcentration. The suitable pH range for sulfate ion adsorption was found to be from 2 to 4. Absorbed sulfate ions were eluted using 5ml of 0.05M sodium hydroxide. Sulfate ions were also adsorbed in 20% sodium chloride solution. The minimum limit of determination was 0.02mg/kg when 50ml of a 10% sample solution was concentrated. The trace sulfate ion contents of sodium chloride reagents of volumetric-analysis, special, extra-pure and pharmacopoeia grades were determined with this method.
Functionalized cellulose (Chelest Fiber IRY, abbreviated as IRY) with imminodiacetic acid was used to separate and concentrate trace Mn (II) from aqueous solution in both batch and column experiments. 200 mg of Mn (II) was quantitatively retained at pH>4 by using 0.3g of adsorbents, stirring time was more than 5min, and aqueous phase volume was 100mL. The retention of 20μg of Mn (II) on the adsorbent (1.0g) was not affected by the flow rate of sample solution up to 25mL/min (studied flow rate range 4-25mL/min). The sorbed Mn (II) was eluted with 10mL 1mol/L HNO3at a flow rate of about 5mL/min, with a recovery rate of over 98%. The sorption follows Langmuir and Freundlich isotherms. The maximum sorption capacity was found to be 0.75mmol/g IRY. The developed method was applied to the separation and determination of trace Mn (II) in saline samples.
In our investigation we proposed a quantitative analysis system for manganese (II) cation in NaCl matrix by means of solid state electron spin resonance (ESR) spectroscopy. The signal is due to Mn2+, which results in six hyperfine splitting of equivalent intensities owing to the nuclear spinI=5/2 of Mn nuclei. In typical NaCl matrix of food, however, the Mn2+signals exhibit non-equivalent hyperfine intensity with relatively much higher intensity in the central groups. Mn2+contents in the NaCl matrix of the foods were determined by ESR. These studies reported Mn2+content in the food, for example, Uji-cha (maccha); 195.00μg/g and red Hibiscus (Hibiscus sabdariffa)-cha; 216.00μg/g. On as hand, Mn2+contents in the drinks were determined Uron-cha in the pet-bottle, 0.900μg/mL, and Beer made from barley, 0.082μg/mL.
Sequential extraction procedure was applied to the volcanic marine sediments collected at Wakamiko Caldera in Kagoshima Bay and Teishi Knoll in Sagami Bay for interpretation of their sedimentary environments. The extraction behaviors of arsenic and antimony in the Wakamiko Caldera sample suggest that those elements, which have been introduced to seawater through volcanic hydrothermal fluids, have been held in sediments in two states;one is in the oxidative form, in which they may be scavenged by iron-manganese hydroxides, and the other is in the reductive form, like sulfides. Contrary to this, arsenic sulfides are not found in the Teishi Knoll sample, although the existence of antimony sulfides is suggested. The existence of arsenic sulfides in the Wakamiko Caldera sample may be ascribed to the relatively high concentration of hydrogen sulfide in the hydrothermal fluids ejected there. The sequential extraction procedure for volcanic marine sediments is thus a useful tool for the chemical characterization of hydrothermal fluids supplied from the seabed, where the sediment samples were collected.