In this study, we developed a rapid and simple analytical method for the simultaneous determination of pesticide residue in environmental water using an LC-Orbitrap (Q-Exactive Plus) with ...electrospray ionization mode. The detection process was performed in Full scan/ddMS2 mode. Sample preparation was performed using online SPE. Only 1 mL of each water sample was injected during the on-line SPE and the samples were ﾠ concentrated in a Hypersil GOLD aQ trapping column. We compared seven gradient programs and three analytical columns to analyze the 360 pesticides. Most compounds were detected using the CORTECS C18 column with the 7th gradient program method. The established method was validated by linearities, accuracy, precisions, and limits of quantification (LOQ) of the 340 pesticides. The calibration linearities were over 0.994 and LOQ were 5.2-283.3 ng/L. Accuracy and precision values were achieved in the ranges of 91-120% and ﾠ 0.63-8.21%, respectively. This method can be applied to effectively monitor the health of aquatic environments and can be potentially applicable in a variety of fields in the future. KCI Citation Count: 0
Quality control systems of environmental testing laboratories are operated on the basis of proficiency tests and on-site assessments conducted in nine fields of testing laboratories. In this study, ...the assessment results of quality control systems present in environmental testing laboratories are analyzed with respect to their conformance with international standards(ISO/IEC 17025). The assessment results of quality control systems of 357 environmental testing laboratories indicate that the majority of the targeted laboratories meet the conformity requirements but 10 laboratories do not meet the conformity requirements. According to the score distribution, the waste testing laboratory and persistent organic pollutants testing laboratory have the highest scores of 88.2 points and 87.6 points, respectively. The air quality testing laboratory and odor testing laboratory have the lowest scores of 82.3 points and 80.1 points. Furthermore, the overall average score has increased from 84.0 points in the year 2012 to 85.4 points in the year 2016. KCI Citation Count: 0
시험 · 검사방법의 유효성 검증 방법 비교 황종연; Jong Yeon Hwang; 이신우 ...
환경분석과 독성보건,
09/2019, Letnik:
22, Številka:
3
Journal Article
One of the most important purposes of a validation method is to verify whether a test method is suitable for the purpose of the test. In this study, validation parameters that are used by national ...and international institutes for test and inspection bodies are classified. As a result of classifying these general factors, method validation parameters were performed, including the following cases: ① the confirmation of a new test method, ② comparison between a non-standardized test method and standardized method, ③confirmation of a test method needing such extensions as a test method verification, verification of the test method applied between other test institutes or analysts, ④ verification of the required similarity between test methods, and ⑤ revalidation of the previously verified test methods. The general parameters applied in the validation processes were classified as follows; specificity, selectivity, linearity, sensitivity, accuracy, precision, detection limit uncertainty, quantitative limit, and range. By a comparison of the validation guidelines or guideline parameters applied by the test and inspection bodies, the survey results were considered to be useful in preparing validation guidelines for environmental testing and inspection methods. KCI Citation Count: 0
An analog-to-digital converter (ADC) is an essential device in mixed mode systems. The performance of the ADC, however, is deteriorated by coupled power supply noises through hierarchical chip-PCB ...power distributed networks (PDNs). In order to design a high-performance system, modeling and analysis of power supply noise effects on the ADC are necessary, as the power supply noise is coupled to the circuit through the hierarchical PDN structure in multilayer PCB substrates. In this paper, a hybrid model is proposed for analysis of power supply noise effects on the ADC. The model combines two modeling mechanisms. First, the coupling ratio of the power supply noise is derived by the combined model of hierarchical PDNs at the PCB and the chip. Second, an analytical model is proposed using equivalent circuits for analysis of the power supply noise effects on the ADC. The ADC is designed using a 0.13um CMOS process. The proposed model and analysis are verified based on a simulation from 100kHz to 4GHz. The performance of the ADC is dominantly affected by characteristics of the on-chip circuit under 100MHz. It is also confirmed that the Effective Number of Bits (ENOB) of the ADC is strongly dependent on the hierarchical PDN impedance over 100MHz. Furthermore, there are peak points caused by inter-modulation (IMD) and cavity resonances of PDN structures.
Introduction
Corrosion control of treated water is an important aspect of safe drinking water supplies. Highly corrosive water can cause system failures or result in health problems because of ...dissolved lead and other heavy metals from plumbing utilities. This paper is to evaluate corrosivity of water flowing in the distribution systems from water treatment plants in Korea
Experimental
The langelier Saturation index(LI), a measure of solution’s ability to dissolve or deposit calcium carbonate, is often used as an indicator of the corrosivity of water. LI is an equilibrium model derived from the theoretical concept of saturation. It indicates the degree of saturation of water with respect to calcium carbonate and can be calculated from
LSI = pHa -pHs
Where:
pHa : the measured water pH
pHs : the pH at which water with a given calcium and alkalinity as CaCO3 is an equilibrium with calcium carbonate.
The LI was calculated from the chemical parameters including Temperature, Alkalinity, Calcium, pH and Conductivity at major 70 WTPs in Korea from July 2014 to October 2015.
Result
s
Water quality parameters of treated water in Korean WTPs are shown in Fig. 1. From the recorded data , alkalinity ranged between 4.7 and 108.0 mg/L on average 31.6 mg/L as CaCO3. The concentration of Ca ranged between 1.86 and 44.8 on average 19.1mg/L in all WTPs. The result of pH varied from 6.33 to 8.40 on average 7.12, indicating sub-acid to sub-akaline in nature.
The calculated LI of raw and treated water were low (Fig.2). Mean LI values in raw water of WTPs were -0.93, -1.41, -1.68, and -1.80 for the Han, Nakdong, Keum, and Sumjin river basin, and values in treated water were -1.37, -1.78, -1.86, and -2.50 respectively.
LI of raw water from tributaries of four major rivers were relatively low and the geological characteristics of granite in Korea was considered as a main cause of it. Increased corrosivity of treated water resulted from the decrease of pH and alkalinity, which occurred during the purification process especially coagulant treatment. If the corrosion management guidelines were set to the Japan’s guideline(LI≥ -1.0), 61 water treatment plants among 70 were classified as which were required corrosion control(87%).
Based on the correlation results between LI and water quality parameters, pH and calcium concentration were confirmed as the major components for LI(Table 1).
Therefore, pH and Calcium concentration control is considered as an effective method for the management of corrosivity of tap water
According to investigated LI, the treated water in Korean WTPs during 2014~2015 can be classified as corrosive water. This result indicates that the further treatment will be needed for the safe domestic use of water.
Reference
A. B. Richard, E. M. Nancy, A. C. David, Strategies for assessing optimized corrosion control treatment of lead and copper, American Water Works Association, 2013, 105(5), pp. 62-75
Figure 1
Introduction
The principle oxidants in the drinking system are dissolved oxygen and chlorine, and the corrosion of water pipe is going alone because of oxidants reaction. Since 1930, pH control ...chemicals such as NaOH, Ca(OH)
2
, NaHCO
3
, and phosphate corrosion inhibitors have been used to prevent the corrosion of water pipes. However, to directly add Ca(OH)
2
at inlet of water well in production process of drinking water may cause a problem to make clouding phenomenon in tap water. The objective of this study removes such problems as the turbidity, strengthen more safety of water.
Experimental
Materials – The iron(carbon steel) was in the form of sheet 0.04 cm in thick and the following analysis: Fe 99.62%, Mn 0.26%, Cu 0.08%, Ni 0.05%, Mo 0.01%. specimens cut from this sheet measured 15cm×1.2cm. The chemicals used as corrosion inhibitors were NaOH, Ca(OH)
2
, and H
3
PO
4
and tap water used as blank. NaOCl was used to disinfect the drinking water made by the demo plant. In order to examine the effect of disinfectant residual concentration according to adding lime water and corrosion inhibitor such as ortho phosphate(H
3
PO
4
), the residual concentration of disinfectant was measured in carbon steel water pipe 50 m in length at the corrosion pilot plant and the temperature of solution was in room temperature between 5°C in the winter to 35°C in the summer. Chlorine residual concentration in the water pipes 50 m in length was measured for 5, 10, 20, 40, 60 min, respectively. The electrochemical tests was measured using Solartron Potentiostat 1480 and the test was performed in a typical three electrode cell which consist of carbon steel as working electrode, saturated calomel electrode as reference electrode, platinum counter electrode.
Result
s
HOCl and OCl
-
in drinking water which chlorine was added as disinfectant reach in equilibrium state at nearly pH 7.5. As pH increases, more of OCl
-
exists than the strong disinfectant, HOCl
-
, Increasing HOCl below pH 7.5 is more benefit in terms disinfectant efficiency. Figure 2 above shows the concentration of free residual chlorine with time. Running drinking water in the pipe, adding PO
4
decreased concentration of chlorine from 0.48 to 0.28 ppm for 40 min, NaOH decreased concentration of chlorine from 0.45 to 0.10ppm, Ca(OH)
2
decreased concentration of chlorine from 0.24 to 0.10 ppm, but tap water as blank degreased concentration of chlorine from 0.40 to 0.07 ppm for only 10 minutes. Of three corrosion inhibitors, PO
4
showed the highest reduced efficiency for the concentration of residual chlorine. To inhibit the reaction of chlorine with metal water pipe is similar to inhibit the corrosion reaction.
Reference
US EPA, Disinfection Profiling and Benchmarking, EPA Guidance Manual, August 1999.
American Society for Testing and Materials, G 4-95(1996).
Figure 1
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