• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.223-228
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• 2006

High-performance liquid chromatography(HPLC) and fluorescence derivatization were applied for a trace-level N-nitrosodimethylamine(NDMA) analysis of water samples. Fluorescence intensity was optimized with the excitation wavelength of 340 nm and the emission wavelength of 530 nm. pH adjustment after denitrosation was necessary to get a maximum intensity at pH between 9 and 12. Maximum intensity was found with a dansyl chloride concentration of 330 to 500 mg/L. Percentile error in the water sample analyses through solid phase extraction was 12-162% and 6-23% for the lower concentration level(10-200 ng/L NDMA) and the higher level(100-1000 ng/L NDMA), respectively, showing more discrepancy in lower level. However, the average ratios of estimated NDMA to the standard NDMA were close to 1 for both concentration ranges, presenting this HPLC method could detect from tens to hundreds nanograms NDMA per liter. Accurate determination of NDMA, which was injected to a wastewater effluent, revealed the selectivity of fluorescence derivatization for the target compound(NDMA) in the presence of complex interfering compounds. The HPLC with fluorescence derivatization may be applicable for determining NDMA of water and wastewater samples fur various research purposes.

• Journal of Food Hygiene and Safety
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• v.13 no.1
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• pp.41-46
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• 1998

A postcolumn derivatization method was tried for the simultaneous determination of four major aflatoxins ($B_1,\;B_2,\;G_1,\;and\;G_2$) by high-performance liquid chromatography with fluorescence detection. As compared with a previous precolumn derivatization method, it was found that the postcolumn derivatization combined with an electrochemical cell (Kobra cell) was less time-consuming, safer, improved the sensitivity and selectivity, and provided good recoveries for aflatoxin $B_1$ (88.9%) and $G_1$ (100.5%). This method showed linearity from 10~100 ppb for aflatoxin $B_1\;and\;G_1$, and from 3~30 ppb for aflatoxin $B_2\;and\;G_2$. However, aflatoxin Bz and Gz were not detected satisfactorily although they showed good resolution.

• Archives of Pharmacal Research
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• v.23 no.1
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• pp.26-30
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• 2000

The enantiomers of the bronchodilator terbutaline were separated by reversed-phase high performance liquid chromatograhy after derivatization with 2,3,4,6-tetra-O-acetyl-\beta-D-glucopyranosyl isothiocyanate(GITC) reagent. The derivatization proceeded quantitatively within 1 h at room temperature. The corresponding diastereomeric thiourea derivatives were well resolved on an ODS column with acetonitrile-acetate buffer as a mobile phase. Elution orders of the diastereomers were confirmed by derivatization of R-(-)-terbutaline and S-(+)-terbutaline which were collected by semi-preparative chiral HPLC using Sumichiral OA-4700 column. The native fluorescence of terbutaline was quenched by derivatization with GITC. The detection limit was 25ng when monitored at UV 278 nm.

• Korean Journal of Veterinary Research
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• v.44 no.1
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• pp.23-28
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• 2004

We established a new method to analyze moxidectin using high performance liquid chromatography(HPLC) with fluorescence derivatization in order to obtain its residual profiles in biological samples. Recovery of moxidectin in tissue was 62% at 10 ppb. Average detection reproducibility in terms of coefficience variation was 4.47% at 0.32 to 10 ppb. Residual of moxidectin was studied in 44 Yorkshire-Landrace mixed bred male pigs administered subcutaneously 0, 200, or $800{\mu}g/kg$ body weight (BW) Residual profiles of moxdectin in blood, muscle, liver, kidney and fat of pigs were described. The concentration of the moxidectin in liver after administration of moxidectin was the highest among the tissues examined. Moxidectin in liver after administration of moxidectin as $200{\mu}g/kg$ BW was declined from $10.0{\pm}3.7ng/g$ at 10 day post administration to $0.5{\pm}0.3ng/g$ level at 40 day post administration. Residual levels of moxidectin in all samples were estimated to fall below the limit of quantitation (0.32 ng/ml) after 50 day after treatment of $200{\mu}g/kg$. Moxidectin showed no abnormal observations in all the clinical findings at any concentrations under these experimental conditions. In conclusion, this analysis method by HPLC after fluorescence derivatization was very effective for the detection of moxidectin in biological samples. We suggest that 50-day is safe enough for the withdrawal time of moxidectin in pigs, following the recommendation dose by the manufacturer.

• Journal of Food Hygiene and Safety
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• v.11 no.2
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• pp.149-157
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• 1996

A procedure for the determination of Aflatoxins in food and grains which utilizes reversed phased liquid chromatographic (LC) analysis with postcolumn derivatization by an electrochemical cell and determination with a fluorescence detector has been evaluated. The LC mobile phase was water-acetonitrile-methanol (6+2+2) with 1mM KBr and 1 mM HNO3 which gave baseline separation for the four Aflatoxins (AfB1, AfB2, AfG1, AfG2). The electrochemical cell set at 7V, generated bromine and derivatized aflatoxins B1 and G1, The derivatives were detected by the fluorescence detector. The aflatoxins in naturally contaminated corn samples were isolated by three different cleanup procedures: the AOAC method I column(CB method), a rapid filtrate column (Romer's column), and an immunoaffinity column. The final extract were quantitated with fluordensitometric TLC and the LC postcolumn derivatization techniques. The results were quite similar, however the LC technique showed less interferences and could be automated. Samples of corn, raw peanuts, peanut butter and dried dates were also analyzed successfully with this procedure.

• YAKHAK HOEJI
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• v.46 no.6
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• pp.392-397
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• 2002

A simple and sensitive high performance liquid chromatographic method to quantitate ursodeoxycholic acid in crude drug pharmaceuticals was investigated. Ursodeoxycholic acid react with 2-bromoacetyl-6-methoxynaphthalene (Br-AMN) in the presence of triethylamine to form highly fluorescent derivative. The derivatization procedure was performed at 7$0^{\circ}C$ and completed within 30 min. The optimal wavelength of the fluorescence detector are λ$_{ex}$=300 nm and λ$_{em}$ = 460 nm. The LOD of the ursodeoxycholic acid was 25 ng/mι based on the S/N =3, and the LOQ was 80 ng/mι based on S/N = 10. Crude drug pharmaceuticals pretreated by solid phase extraction (Sep-pak $C_{18}$ cartridge) which were shown very good separation and recovery values for the compound.d.

• Korean Journal of Veterinary Research
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• v.47 no.4
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• pp.389-393
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• 2007

In this study, the levels of aflatoxin $M_1$ ($AFM_1$) in milk were determined by HPLC with derivatization method. Milk samples were purified using $C_{18}$ disposable cartridge followed by derivatization with trifluoroacetic acid and analysed using HPLC with fluorescence detection. The recoveries of AFM1 from milk samples added $AFM_1$ at a level of 0.025~0.1 ng/ml were 94.7~98.0% with detection limit of 0.009 ng/ml. The amounts of $AFM_1$ were determined below 0.05 ng/ml for all tested samples of commercial milk collected in 1999 and 2000.

• Korean Journal of Veterinary Research
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• v.40 no.1
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• pp.35-41
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• 2000

We established a new method to analyze abamectin using HPTLC (high performance thin layer chromatography) in order to obtain its pharmacokinetic profiles in pigs. Recovery of abamectin in pig serum after fluorescence derivatization was $80.01{\pm}3.82%$ at 0.1ppm and $83.67{\pm}3.63%$ at 10ppm, respectively. Detection reproducibility in terms of coefficient variation (c.v.) was 3.09% and 2.74% (intra-day), and 3.71% and 51.7%(inter-day), for 0.1 and 10ppm, respectively. Pharmacokinetics of abamectin was studied in five Yorkshire-Landrace mixed bred male pigs ($35.0{\pm}2.7kg$) administered intramuscularly 0.3mg/kg b.w. Pharmacokinetic profiles of abamectin in pigs were described by the 1-compartment open model with first-order absorption and first-order elimination. AUC (area under the curve) was $262.65{\pm}16.44ng{\cdot}day/ml$ and the biological elimination half-life ($t_{1/2},\;k_e$) was $5.28{\pm}0.84$ days, indicating somewhat high bioavailability and long half-life by the intramuscular route. We suggest intramucular injection of abamectin could be also used in place of the recommended route of its subcutaneous administration so far.

• Archives of Pharmacal Research
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• v.20 no.5
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• pp.486-490
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• 1997

A stereospecific HPLC method has been developed for the resolution of the enantiomers of salbutamol in human urine. After solid-phase extraction and derivatization with (S)-(-)-${\alpha}$-methyl-benzyl isocyanate, the diastereomeric derivatives were resolved $(R_s=1.59)$ on $5{\mu}M$ octadecylsilan column using 47% methanol as a mobile phase with fluorescence detection. The detection limit of each enantiomer was 10 ng/ml (S/N=3).

• Analytical Science and Technology
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• v.8 no.4
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• pp.545-551
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• 1995

Five acid hydrazides as precolumn fluorescence derivatization reagents for carboxylic acids in HPLC, which have the benzofuran or benzothiazole moiety conjugated to a furan, thiophene or oxazoline ring, were synthesized and examined in view of reactivity, separability and sensitivity. Of these hydrazides, 2-(5-hydrazinocarbonyl-2-oxazolyl)-5,6-dimethoxybenzothiazole (BTOH) was most favorable. The detection limit of lauric acid as a model acid was 0.1 pmol per $10-{\mu}l$ injection volume at S/N=3, which was roughly equal to that of an analogous compound, 2-(5-hydrazinocarbonyl-2-furyl)-5,6-dimethoxybenzothiazole. The reagent allowed rapid assays of carboxylic acids ($C_{12:0}-C_{20:4}$) within 20 min with satisfactory scparability. The method was applied to the determination of fatty acids in human sera from healthy volunteers as well as from patients with diabetes or thyroid dysfunction.