In this report aimed on further development of a high-sensitivity capillary gel electrophoresis (CGE) method for analysis of DNA fragments, we firstly explored online transient isotachophoresis (tITP) preconcentration combined with fluorescence detection (FD). The fluorescence signal (excitation: 488 nm; emission: 590 nm) was generated using the intercalating dye of ethidium bromide (EB). It was found when the leading electrolyte (LE) was injected behind the sample zone, such a special tITP mode has significant advantages to solve the bubble formation issue and to improve the analytical performance stability. Two standard DNA samples, a 50 bp DNA step ladder and the phiX174/HaeIII digest, were used to evaluate the qualitative and quantitative abilities of the tITP-FD approach. A highly diluted sample (10,000-fold in the water, e.g. the phiX174/HaeIII digest diluted from 500 microg/ml to the 50 ng/ml level) was enriched and detected; the LOD was down to 0.09 ng/ml for the 72 bp fragment, apparently improved more than 1000-fold in comparison with UV detection. Although the RSD of peak areas (n=3) was around 15.5% for the sample was electrokinetically injected, good linearity of peak area response showed that the proposed method is suitable for quantitative analysis.
close to the theoretical value for both compounds, and almost all organic carbons in each solution were detectable by TOC equipment. On the other hand, the COD oxidation rate in both the saccharide and amino acid solutions decreased according to the increase in the solutions' concentration, and there were also significant differences in the decomposition rate in each compound. The relationship between field data on COD and TOC in Shinji and Nakaumi lakes may be approximated by a quadratic expression, but the approximated curve did not pass the original point.This result indicates that there are some organic compounds that can be decomposed by TOC equipment but not by COD analytical methods, and the decomposition of COD was insufficient in high concentrations in environmental water. Therefore, we consider COD not to be an appropriate indicator of the organic compounds in public waters;instead, TOC should be used.
The release of nitrogen and phosphorus from sediments at high water temperatures was studied by taking weekly measurements at Lake Shinji, a brackish lake in Japan. A severe phosphorus release was observed at high temperatures from August to September. On the other hand, a nitrogen release was observed in July, but not from August to September when the water temperature was higher. Lower nitrite-nitrogen and nitrate-nitrogen concentrations in the water during high water temperature period suggest that the effect of denitrification was minute. The results showed that nitrogen release from sediments in the lake occurs earlier in the year than the phosphorus release.
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