• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 2001.10a
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• pp.171-174
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• 2001

Solid phase micro-extraction (SPME), a solvent-free, rapid and inexpensive method for the extraction of organic compounds from aqueous sample matrices, was evaluated for determination of the 120 pesticides in vegetables such as crown daisy, perilla leaf, leafy lettuce and to mato. The analysis conditions were chosen for the SPME method: 15 min of immersion of the PDMS fiber in 10 ml of the solution with stirring at 1,000 rpm. The recovery tests were carried out in triplicate. The range of recoveries was 0-142% for organochlorine pesticides and $4.9\sim200\%$ for organophosphorus pesticides. The recoveries were very low in the pesticide groups with low solubility in water. The recoveries became lower in proportion to the interference materials in vegetables. The recovery in tomato was relatively higher than that in perilla Ie af and crown daisy. The recovery values obtained by SPE and SPME were compared. In leaf y lettuce, recovery obtained by SPE method ranged from $58.1\%\;to\;136.1\%$ and recovery by SPME ranged from $9.6\%\;to\;176.3\%$ In organophosphorus pesticides. The recovery in SPME method was satisfactory with $136\%$ for ethoprophos, $119\%$ for methidathion and $113\%$ for diazinon. Meanwhile, recovery of EPN, phenthoate and 2,4-DDT revealed relatively low value of $38\%,\;41\%\;and\;3.4\%,$ respectively. However, most of pesticides applied to SPME method sho wed constant recovery and precision. From these results, it can be concluded that solid phase micro-extraction might be an appropriate method for the screening test of pesticides in vegetables.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.5
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• pp.732-739
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• 2002

Milk samples with different phenotype combination of $\{kappa}$-casein and ${\beta}$-lactoglobulin and different preheating temperatures of 30, 70, 75 and $80^{\circ}C$ were used for cheesemaking under laboratory conditions. For the 853 batches of cheese, mean composition was 59.64% total solids, 30.24% fat and 23.66% protein, and the whey contained 6.93% total solids, 0.30% fat and 0.87% protein. Least squares analysis of the data indicated that heating temperature of the milk and ${\kappa}$-CN/${\beta}$-LG phenotypes had significant effects on cheese and whey compositions. The total solids, fat and protein contents of cheese were negatively correlated with preheating temperatures of milk. Cheese from BB/BB phenotype milk had the highest and those from AA/AA phenotype milk had the lowest concentrations of total solids, fat and protein. Mean recoveries of milk components in the cheese were 53.71% of total solids, 87.15% of fat, and 80.32% of protein. For the 10 different types of milk, maximum recoveries of milk components in cheese occurred with preheating temperature of $70^{\circ}C$ or $75^{\circ}C$ and lowest recoveries occurred at $80^{\circ}C$. The whey averaged 6.94% total solids, 0.30% fat and 0.87% protein. Losses of milk components in the whey were lowest for milk preheated at $80^{\circ}C$ and for milk containing the BB/BB phenotype.

• Analytical Science and Technology
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• v.15 no.4
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• pp.346-359
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• 2002

The brominated flame retardants (BFRs) are one of the unregulated pollutants in Korea, which is recently highlighted the new pollutants of environmental contamination. In this study, the previous research papers related the BFRs were surveyed, and the analytical methods of BFRs were established. The results are followed; The 40 kinds of PBDEs standards were used to establish the analytical methods to perform the experiments of recoveries and detection limits in water and soil. The detection limits of PBDEs using GC/MS represented 5.0~10.0 pg/L for water and 0.5~2.0 ng/g for soil samples. The average recoveries of water samples were 89~98% with ethylacetate, n-hexane and dichloromethane, and 89~103% in combined solvent with n-hexane and acetone. In soxhlet extraction, the higher recoveries obtained the acetone:n-hexane(1:1) comparing with acetone:dichloromethane(1:1).

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.271-276
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• 2006

The outbreak cases of Cryptosporidium or Giardia from drinking water in abroad have drawn attentions on the public health. It is well known that Cryptosporidium is the most resistant organism against chlorine disinfection. To guesstimate the levels of Cryptosporidium and Giardia in Korean surface water, 1~2 samples from 22 drinking water sources in four Korean major rivers of Han, Keum, Nakdong, and Youngsan were monitored. In addition, two sites in Kyunganchon, a contaminated river were monitored for comparison. In source waters, detection rates of Cryptosporidium and Giardia were 15% (6/39) and 21% (5/24) with the range of 1~3 oocysts/10 L and 1~6 cysts/10 L, respectively. In Kyunganchon, they were 60% (6/10) and 70% (7/10) in the range of 1~9 oocysts/10 L and 10~72 cysts/10 L, respectively. When one of the source waters in Han river was monitored monthly, Cryptosporidium were found mostly in cold season. Matrix of the samples gave influence on the recoveries of the spiked protozoa. The recoveries of both Cryptosporidium and Giardia increased in the samples of Kyunganchon, known as contaminated area. However, protozoan recovery did not show significant relation with turbidity, the index of matrix contamination, which implies that there are additional unveiled features of matrix affecting the recoveries of the protozoa. The protozoan distribution in Kyunganchon showed significant relations with Cl. perfringens, anaerobic and spore forming indicator bacteria of fecal contamination by regression analysis, but not with turbidity, the general indicator of water quality.

• Analytical Science and Technology
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• v.15 no.3
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• pp.300-316
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• 2002

The extraction methods of PBBs from environmental samples by soxhlet extraction for solid phase and liquid-liquid extraction for liquid phase were compared. After extraction, silicagel and florisil as column clean up methods were used for the comparison of cleanup efficiency with different solvent system. Also, the analytical instruments were used GC/MSD. The 22 kinds of PBBs standards were used to establish the analytical methods to perform the experiments of recoveries and detection limits in water and soil. The detection limits of PBBs represented 5~10 ng/L for water and 0.5~3.5 ng/g for soil samples, respectively. The recoveries of water samples represented 96~107% in n-hexane, dichloromethane and toluene for water, and 60~80% in combined solvent with n-hexane and acetone. The recoveries of soil sample were surveyed 67~97% in soxhlet extraction and 64~76% in ultrasonic extraction with selected solvents.

• Analytical Science and Technology
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• v.13 no.5
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• pp.636-645
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• 2000

A method is described for the determination of organotins in water samples by GC/MS. Optimized derivatization methods for ethylation and hydrogenation of organotins were surveyed according to various reaction conditions such as time, pH and concentration of reagents. The organotins were extracted with n-hexane in presence of 0.1% tropolone and hydrogenated with sodium borohydride. Extraction recoveries of organotins with hydrogenation were in the range of 61-112%. After ethylation, organotins in water samples were extracted by liquid-liquid extraction (LLE) and solid-phase extraction (SPE). Using LLE, extraction recoveries were in the range of 74-113%. The recoveries ranged from 61-97% in the case of SPE with styrene-divinylbenzene copolymers. Method detection limits of hydrogenated and ethylated organotins ranged from 0.05 to 0.5 ng/ml and from 0.02 to 0.05 ng/ml, respectively.

• Korean Journal of Food Science and Technology
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• v.15 no.3
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• pp.209-214
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• 1983

Analytical methods on Stevia sweeteners are compared for their reproducibilities and recoveries. It is possible to separate stevioside, rebaudioside A, rebaudioside C, and dulcoside A through HPLC analysis. Steviolbioside, in addition to above 4 Stevia sweeteners, is detected through TLC scanner and TLC-FID assays. C.V.s on stevioside and rebaudioside A in HPLC analysis are 1.39 and 4.89%, which shows outstanding reproducibilities of this method. The recoveries of stevioside in HPLC, TLC scanner, and TLC-FID analyses are 97.7 89.4, and 97.3%. The recoveries of rebaudioside A in HPLC, TLC scanner, and TLC-FID assays are 90.8, 90.1, and 75.8%. Total content of Stevia sweeteners in 8 strains tested, ranges from 5 to 17% as dry weight basis.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.66-74
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• 1992

A method for the multiresidual simultaneous analysis of 11 thiocarbamates was studied using HPLC. Thiocarbamate in Chinese cabbage was analyzed in the order of extraction, partition, and cleanup in their optimum condition. Acetone was chosen as an extracting solvent. As a partitioning solvent, the mixture of 50% methylene chloride and petroleum ether containing extremely small water content showed good recoveries of thiocarbamate from the water layer. Partition efficiency was affected by pH of the water layer; it remained almost constant under the acidic and neutral condition while decreasing under the basic condition. The comparison done in cleanup step showed that the column chromatographic method is superior to the treatment of coagulating reagent. As an absorbent, the mixture of charcoal, magnesia, and celite with the ratio of 1 : 2 : 4 gave better recoveries and also effectively removed chlorophyll. Over the total procedure, the average recoveries for thiocarbamates in Chinese cabbage were 91% at about 2 ppm fortification level within the relative standard deviation of 8%, and the minimum detection limit (MDL) was 2.2${\sim}$9.3 ng.

• Elastomers and Composites
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• v.44 no.4
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• pp.442-446
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• 2009

Recovery behaviors of unfilled NR, BR, and SBR vulcanizates after aging with a circular deformation were compared to prevent the influence of reinforcing agent. Samples were aged at room temperature, 50, 70, and $90^{\circ}C$ for 10 days. Recovery increased by increasing the measurement time. Instantaneous recoveries less than 1.0 sec were obtained using the recovery variations with the measurement time. For aging at room temperature, difference in the recoveries of the rubber samples was not significant because the aging time was too short. However, for accelerated thermal aging at 50, 70, and $90^{\circ}C$, difference in the recoveries of the rubber samples was significant. Degree of recovery of BR specimen was higher than those of the others, while that of SBR was lowest. However, for accelerated thermal aging at $90^{\circ}C$, recovery of the NR sample was higher than that of the BR one. The initial recovery decreased by increasing the aging temperature and the decrement of SBR was larger than the others. The experimental results were explained with the resilience properties of rubbers and the crosslink density changes by thermal aging.

• Korean Journal of Food Science and Technology
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• v.28 no.6
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• pp.1033-1037
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• 1996

An attempt was made to analyze preservatives in flavor-containing curry and tomato ketchup without interference due to their of flavor components. Samples were steam-distillated and extracted with ether. Sorbic acid, benzoic acid, dehydroacetic acid and salicylic acid were analyzed by GC with capillary column. Benzoic acid and dehydroacetic acid in curry were interfered by flavor components, but there was no interference in case of tomato ketchup. Samples were pretreated with Sep-Pak $C_{18}$ cartridge and analyzed with HPLC to avoid any interference due to flavor components. The recoveries by HPLC were higher than those by GC. Recoveries of sorbic acid, benzoic acid and salicylic acid from curry were 79.9%, 71.2% and 64.4%, respectively. Recoveries of sorbic acid, benzoic acid and salicylic acid from tomato ketchup were 83.4%, 87.8% and 77.7%, respectively.