• 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.

• Environmental Analysis Health and Toxicology
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• v.17 no.1
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• pp.37-51
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• 2002

Eleven phenols including two chlorophenols, eight alkylphenols and bisphenol A were derivatized with isobutylchloroformate to form their isobutoxycarbonyl derivatives. Standard phenol mixture was concentrated for the isobutoxycarbonyl (isoBOC) derivatization and analysed by gas chromatography/mass spectrometry (GC/MS). The recoveries of the derivatization method of alkylphenols, chlorophenols, and bisphenol A were calculated by gas chromatography/mass spectrometry-selected ion monitoring mode using two work-up methods for comparison; shaking and heating method. The linear detector responses were obtained in the concentration range of 5∼400 ng, with correlation coefficients varying from 0.9755∼0.9981. Recoveries of the alkylphenols, chlorophenols, and bisphenol A were determined by gas chromatography/mass spectrometry-selected ion monitoring mode using two work-up methods for comparison ; the US-EPA method and the isoBOC derivatization method, Eleven phenols in water samples were extracted with dichloromethane and then concentrated. Also, solid-phase extraction (SPE) with XAD-4 and subsequent conversion to isobutoxycarbonyl derivatives for sensitive analysis with the selected ion-monitoring (SIM) mode. The recoveries were 85.1∼109.9％ and 90.3∼126.6％ for the US-EPA method and the isoBOC.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1533-1538
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• 2005

We have determined the contents of monosaccharides in the hydrolysates of some yogurt and orange juice products by derivatizing monosaccharides with p-aminobenzoic acid ethyl ester (ABEE). The separation of the ABEE-derivatized monosaccharides was efficiently carried out by HPLC using a microcolumn packed with the Alltima $C_{18}$ stationary phase. The concentrations of monosaccharides were determined based on the measured peak area/height counts. ABEE derivatization of fructose and its detection have never been successfully carried out before this work. In this study, two peaks were observed in a fixed ratio for ABEE-fructose, and the ratio was maintained over a wide range of fructose concentration. In order to prove the validity of the above method, we compared the concentrations of glucose, galactose and fructose determined by ABEE derivatization and UVD (ultraviolet detector) chromatography with those determined by RID (refractive index detector) chromatography without derivatization. The determined concentrations of monosaccharides obtained from the two chromatographic methods were found close to each other within acceptable error ranges.

• Archives of Pharmacal Research
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• v.26 no.9
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• pp.697-705
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• 2003

The alkylphenols, chlorophenols, and bisphenol A were determined by gas chromatography/mass spectrometry-selected ion monitoring (GC/MS-SIM) followed by two work-up methods for comparison: isobutoxycarbonyl (isoBOC) derivatization and tert-butyldimethylsilyl (TBDMS) derivatization. Eleven endocrine disrupting chemicals (EDCs) of phenols in biological samples were extracted with acetonitrile and then the acetonitrile layer underwent freezing filtration 6$0^{\circ}C$ for 2 hours. Solid-phase extraction (SPE) was used with XAD-4 and subsequent conversion to isoBOC or TBDMS derivatives for sensitivity analysis with the GC/MS-SIM mode. For isoBOC derivatization and TBDMS derivatization the recoveries were 92.3∼150.6% and 93.8∼108.3%, the method detection limits (MDLs) of bisphenol A for SIM were 0.062 $\mu$ g/kg and 0.010 $\mu$ g/kg, and the SIM responses were linear with the correlation coefficient varying by 0.9755∼0.9981 and 0.9908∼0.9996, respectively. When these methods were applied to mackerel samples, the concentrations of the 11 phenol EDCs were below the MDL.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.432-438
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• 2007

Environmentally important phthalic esters have been analyzed by GC-MS in terms of individual phthalic esters or total phthalic esters directly or after derivatization. Derivatization improves the chromatographic characteristics of the highly polar phthalic esters. This study focused on the GC-MS determination of the total phthalic esters and the individual phthalic esters simultaneously. The phthalic esters were hydrolyzed to phthalate and corresponding alcohols in 1 M NaOH solution at 90 oC for 30 min followed by extraction with ethyl acetate after acidifcation. The phthalic acid and alcohols were simultaneously silyl derivatized using bis(trimethylsilyl)trifluoroacetamide (BSTFA) to their corresponding silyl ester and ethers in the mixture of 60% acetone and 40% ethyl acetate at room temperature within 30 min. Because of the high reactivity of BSTFA with the phthalic acid and alcohols effective silyl derivatization was possible simultaneously. GC-MS analysis of the silyl derivatives of phthalic acid and alcohols was performed. The total phthalic ester content was estimated from the analytical result of phthalic silyl ester, while the individual phthalic ester was quantified from the analytical results of alcoholic silyl ethers. This technique was applied to spiked tab water and real seawater samples from the Lake Shihwa in Korea. The results were checked against the results from the direct GC-MS analysis of the phthalic esters and reasonable recoveries with high sensitivity were achieved. The recoveries were higher than 75% with low relative standard deviation (below 10%).

• Journal of Microbiology and Biotechnology
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• v.11 no.5
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• pp.819-824
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• 2001

The principal DNA modification systems of the amino-acid-producing bacteria Corynebacterium glutamicum AS019, Brevibacterium flavum BF4, and B. lactofermentum BL1 was investigated using two approaches; digestion of plasmid DNA isolated from these species TseI and Fnu4HI, and sequence analysis of the putative methyltransferase target sites following the derivatization of DNA using metabisulfite treatment. The C. glutamicum and B. flavum strains showed similar digestion patterns to the two enzymes, indicating that the target for cytidine methyltransferase recognizes 5'-GCSGC-3'(where S is either G or C). Mapping the methylated cytidine sites by bisulfite derivatization, followed by PCR amplification and sequencing, was only possible when the protocol included an additional step eliminating any underivatized DNA after PCR amplification, thereby indicating that the derivatization was not $100\%$ efficient. This may have been due to the high G0C content of this genus. It was confirmed that C. glutamicum AS019 and B. flavum BF4 methylated the cytidine in the $Gm^5CCGC$ sequences, yet there were no similar patterns of methylation in B. lactofermentum, which was consistent with the distinctive degradation pattern seen for the above enzymes. These findings demonstrate the successful application of a modified bisulfite derivatization method with the Corynebacterium species for determining methylation patterns, and showed that different species in the geneus contain distinctive restriction and modification systems.

• 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.

• Analytical Science and Technology
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• v.28 no.2
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• pp.112-116
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• 2015

Extraction of quaternary ammonium compounds (choline and betaine) from plant samples (spinach) using ion exchange resin (AG1, OH⁻ form) is a very simple and inexpensive approach. However, it is very hard to determine amounts of choline and betaine simultaneously using high-performance liquid chromatography-ultraviolet (HPLC-UV) detection. Unlike choline, betaine has low molar absorptivity in UV-visible (UV-Vis) region, which makes it difficult to carry out UV-Vis detection of betaine. The mixture of quaternary ammonium compounds (choline and betaine) was derivatized using 2-bromo acetophenone as a derivatizing agent. As a result, choline did not react with the derivatizing agent, whereas betaine formed a betaine derivative. This betaine derivative exhibited detectable UV absorption with baseline separation between choline and the betaine derivative. Thus, with this method, choline and betaine can be determined simultaneously by using the HPLCUV method through one-step derivatization, which is an easy, sensitive, and reliable method.

• Korean Journal of Pharmacognosy
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• v.48 no.1
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• pp.46-50
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• 2017

This study was conducted to investigate the antioxidative activities and tyrosinase inhibition effects of fractions from the distilled water extract of Inonotus obliquus. Moreover, GC-MS based analysis with trimethylsilyl (TMS) derivatization was carried out for active compound in the extract of I. obliquus. In DPPH radical scavenging ability, $SC_{50}$ values of the ethyl acetate fraction was 0.393 mg/ml as a result of the most effective than other fractions. Meanwhile, aqueous fraction showed higher effect in tyrosinase inhibitoty activity. In GC-MS based analysis with TMS derivatization, 7 compounds including syringic acid, vanillic acid and protocatechuic acid were observed in ethyl acetate fraction, and oxalic acid is the main compound in aqueous fraction. As a result, it was confirmed that oxalic acid in aqueous fraction from the distilled water extract of I. obliquus was a compound showing tyrosinase inhibition effect.

• 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.