Chinese Journal of Chromatography

Development of surface tension induced control and manipulation inside microchannels

LIN Jin-Ming

2010, 28 (10): 913-914. DOI: 10.3724/SP.J.1123.2010.00913

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Recent advances of high performance chemically bonded silica gel stationary phases

TONG Wei, ZHANG Yangjun, QIN Weijie, QIAN Xiaohong

2010, 28 (10): 915-922. DOI: 10.3724/SP.J.1123.2010.00915

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The advances of the development and the application of silica packing medium in high performance liquid chromatography (HPLC) are reviewed. The physicochemical properties on surface and the methods of pre-processing of this medium are introduced. The bonding modes and the classes of chemically bonded stationary phase are described. The applications of silica packing medium in HPLC and its developing trends are also outlined.

Determination of organic acids and phenols in oil field water by solid phase extraction-ion chromatography and gas chromatography-mass spectrometry

ZHONG Ying, YU Chiling, PENG Ping’an

2010, 28 (10): 923-928. DOI: 10.3724/SP.J.1123.2010.00923

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A method was developed for the determination of low relative molecular mass organic acids and phenols in oil field water with high salinity by ion chromatography (IC) and gas chromatography-mass spectrometry (GC-MS) respectively after solid phase extraction. The experiment showed that organic acids can be well separated from phenols by a Waters Oasis HLB column under neutral pH condition. The former was quantitated by IC after effective removal of chloride by Ag2O and Ag-H columns; and the later was quantitated by GC-MS after the desorption by methyl tertiary butyl ether (MTBE)/methanol (9:1, v/v) and the dehydration by freeze-drying together with anhydrous sodium sulfate. The average recoveries of added standards were more than 80%. The relative standard deviations (RSDs, n=6) were between 2.38% and 9.45%, and all the quantitative limits were less than 88.9 μg/L. The results prove that this method is suitable for the determination of low molecular mass organic acids and phenols in water samples with the chloride content up to 150 g/L.

Investigation of pyrolysis process of caffeic acid in nitrogen using thermogravimetry-single drop microextraction-gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy

YANG Ji, YANG Liu, ZHU Wenhui, WU Yiqin, CAO Qiue

2010, 28 (10): 929-934. DOI: 10.3724/SP.J.1123.2010.00929

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The thermal decomposition behavior of caffeic acid was investigated using the thermogravimetry-single drop microextraction-gas chromatography-mass spectrometry (TG-SDME-GC-MS) and Fourier transform infrared spectroscopy. The heating rate and the air flow rate were set at 5 ℃/min and 400 mL/min, respectively. The evolved components of caffeic acid from thermogravimetry were extracted with ethanol by single drop microextraction in the temperature range of 160~360 ℃. Then the extract was separated and analyzed by GC-MS. Thus, the dynamic changes of the relative contents of 5 main pyrolysis products with the increase of temperature were identified and monitored. The alterations of functional groups of the solid residues at each weight-lose-point were analyzed by Fourier transform infrared spectroscopy. The results showed that the main reason for the weight loss of caffeic acid can be concluded to the generation of mass pyrocatechol at 240~360 ℃ and 4-ethylcatechol at 200~220 ℃. The molecular structure of caffeic acid was completely decomposed at 230 ℃. This method provides a significant approach for the investigation of the thermal decomposition behavior of material with the continuous rising of temperature.

Research of Raw Milk Fingerprint Based on HPLC-MS ESI－

2010, 28 (10): 935-939.

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The HPLC-MS fingerprint of raw milk extracted by acetonitrile was established to evaluate the quality of raw milk．A total of 11 peaks had been identified. The methodology was studied by the relative peak area and relative retention time with No. 7 peak as the reference. The results showed that the fingerprint established by this method has reasonable precision, reproducibility and stability with the relative standard deviations (RSDs) less than 0.79% for the relative retention time and less than 2.84% for the relative peak area．This method has provided a feasible analytical approach to explore the overall quality characteristics of raw milk.

Determination of free formaldehyde in mushrooms by derivative solution extraction and high performance liquid chromatography

LV Chunhua, CHEN Xiaomei, SHI Yingzhu, LIU Haishan

2010, 28 (10): 940-944. DOI: 10.3724/SP.J.1123.2010.00940

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A derivative solution extraction was applied to determine free formaldehyde in mushrooms by high performance liquid chromatography. The formaldehyde in mushrooms directly reacted with 2,4-dinitrophenylhydrazine in acetonitrile-phosphate buffer (pH 5) (1:1, v/v) solution, and then determined by high performance liquid chromatography. The formaldehyde formation by enzyme reaction in mushrooms was inhibited in acetonitrile-phosphate buffer (pH 5) (1:1, v/v) solution, and therefore only free formaldehyde was extracted. To improve the detecting efficiency, 2,4-dinitrophenylhydrazine was dissolved in the solution and free formaldehyde was directly derived during extracting process. The recoveries were 89.2%, 91.7% and 90.4% at the spiking levels of 5.0, 10.0 and 20.0 mg/kg of formaldehyde in mushrooms, respectively, and the relative standard deviations (n=6) were less than 5.0%. The limit of quantification of the formaldehyde in mushrooms was 5.0 mg/kg. The method has been applied to the determination of formaldehyde in real samples and the results showed that the content of formaldehyde was significantly lower than that obtained by the traditional methods. The method has the advantages of simple operation, good accuracy, and meets the requirement of the determination of naturally-occurring formaldehyde in mushrooms.

Determination of organic acids in honey by solid phase extraction-high performance liquid chromatography

ZHU Xiaoling, YE Fei, YANG Jie, XIAO Xiao, WEN Hong, LIU Rui,

2010, 28 (10): 945-949. DOI: 10.3724/SP.J.1123.2010.00945

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A method for the simultaneous determination of 5 organic acids (L-malic acid, maleic acid, succinic acid, citric acid, D-malic acid) in honey was developed by solid-phase extraction and high performance liquid chromatography (SPE-HPLC). The sample was purified by a Bond Elutes SAX SPE cartridge after pretreatment, then separated using a reversed-phase C18-MS-IIcolumn. A 2% metaphosphoric acid solution was used as the mobile phase at a flow rate of 0.7 mL/min. The detection was performed by a diode array detector at 210 nm. Under these conditions, the linear ranges of the method for L-malic acid was 5.0~500 mg/L, for maleic acid was 0.1~500 mg/L, and for succinic acid, citric acid, D-malic acid were 18.0~500 mg/L. The correlation coefficients of 5 organic acids were more than 0.9967. The average recoveries of 5 organic acids were 86.0%~103.9% with the relative standard deviations of 5.7%~9.8% (n=6). The detection limits ranged from 0.06 to 9.4 mg/kg. The method can be used for determining organic acids in honey samples.

Determination of the effective contents of “small cation” in drilling fluid additives using ion-pair reversed-phase liquid chromatography with evaporative light scattering detection

XIA Xiaochun, GUO Lei, ZHAO Zhiqiang, LIU Keqing, YAN Changhong, YI Yong

2010, 28 (10): 950-954. DOI: 10.3724/SP.J.1123.2010.00950

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A method was developed for the determination the effective contents of “small cation”, 2,3-epoxypropyltrimethylammonium chloride (EPTMAC) and 3-chloro-2-hydroxypropyl-trimethylammonium chloride (CHPTMAC), in drilling fluid additives using ion-pair reversed-phase liquid chromatography with evaporative light scattering detection. The separation was performed on an Atlantis column (150 mm×4.6 mm, 5 μm) with the mobile phase of methanol-5 mmol/L heptafluorobutyric acid (10:90, v/v)at a flow rate of 1 mL/min. The drift tube temperature of the evaporative light scattering detector was set at 50 ℃ and the gas pressure was set at 206.7 kPa (30 psi). The sample was diluted by extra pure water and filtrated for analysis. The EPTMAC and CHPTMAC were completely separated and determined within 10 min. The calibration curves of them were fitted by quadratic equations. The correlation coefficients for both of them were 0.9995. The limits of detection were 13 mg/L and 18 mg/L, and the limits of quantifications were 45 mg/L and 61 mg/L for EPTMAC and CHPTMAC, respectively. Their average recoveries were 91.2%~98.6% and 93.2%~102.3% with the relative standard deviations (n=5) of 1.7%~2.5% and 1.2%~1.8%. These results demonstrate that the proposed method is simple and fast for the quality control of “small cation” in drilling fluid additives in oilfield.

Simultaneous determination of acetylacetone and acetone in the reaction mixture for producing acetylacetone by high performance liquid chromatography

ZENG Hongyan, DUAN Zhengkang, LUO Aiwen, ZENG Zhiding

2010, 28 (10): 955-958. DOI: 10.3724/SP.J.1123.2010.00955

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A method was developed for the simultaneous determination of acetylacetone and acetone in the reaction mixture for producing acetylacetone from ketene-acetone process by using reversed-phase high performance liquid chromatography. An Agilent Eclipse XDB-C18 column (150 mm×4.6 mm, 5 μm) was used for the separation at the column temperature of 30 ℃. Tetrahydrofuran-water (15:85, v/v), including 0.1 mol/L monosodium phosphate, was used as the mobile phase (pH 4.0~5.0) at a flow rate of 0.6 mL/min. The detection was performed at 270 nm by an ultraviolet absorbance detector. The quantitative analysis was performed using an external standard calibration curve. Under the optimized conditions, the linear ranges for acetylacetone and acetone were 0.01~50.00 mg/L and 0.01~30.00 mg/L, respectively, and the correlation coefficients were both above 0.9999. The contents of acetylacetone and acetone were determined by this method. The repeatabilities of the analytical results were excellent and the relative standard deviations were less than 1.0%. The spiked recoveries of acetylacetone and acetone were 99.00%~101.50%. Compared with the ultraviolet spectrophotometric analysis of acetylacetone, the relative error was 1.48%. This method provides the basis for the determination of acetylacetone produced by acetone, as well as the similar mixed system. Simultaneously, it is simple, accurate and efficient for determining ketone compounds.

Simultaneous determination of phenobarbital, estazolam and clonazepam in human plasma by micellar liquid chromatography

SHI Jiehua, PENG Li

2010, 28 (10): 959-964. DOI: 10.3724/SP.J.1123.2010.00959

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An analytical method based on micellar liquid chromatography has been developed for simultaneous determination of phenobarbital, estazolam and clonazepam in human plasma. The effects of the concentrations of surfactant, cosurfactant and hydrogen ion in mobile phase (hereafter abbreviated respectively as CM, Cφ and CH) on the retention behavior of the 3 compounds were investigated in terms of three-phase equilibrium theory. The quantitative relationships between the logarithm of retention factor (log k) and the parameters of solutes properties and the composition of mobile phase were set with multiple linear regression method. The experimental results showed that the retention factors (k) of solutes were decreased with the increase of the concentration of surfactant, cosurfactant and hydrogen ion in the mobile phase. The effects of changes of CM, CH and Cφ on retention factors were fully consistent with the theoretical modeling. And there is better multielement linear relationship between the log k of solutes and the logarithm of hydrophobic parameter (log P) and ionization constant (Ka) of solutes and CM, CH and Cφ in the mobile phase. The separation efficiency between phenobarbital, estazolam, clonazepam and other components in human plasma was better under the selected chromatographic conditions. The linearities were good in the ranges of 2.5~50 mg/L of phenobarbital, 0.25~5.0 mg/L of estazolam and 0.05~5.0 mg/L of clonazepam. The method is simple, accurate and reproducible for the determination of phenobarbital, estazolam and clonazepam. The limits of detection (LODs) for phenobarbital, estazolam and clonazepam were found to be 10.27, 1.17 and 0.867 ng (S/N=3), respectively. The recoveries of the method for the determination of phenobarbital, estazolam and clonazepam were 99.80%~102.9%, 94.00%~98.20% and 96.30%~98.70%, respectively.

High performance liquid chromatographic fingerprint analysis of flavonoids from Houttuynia cordata Thunb.

LU Hongmei, PENG Lihua, GUO Fangqiu, WU Xianjin, LIANG Yizeng

2010, 28 (10): 965-970. DOI: 10.3724/SP.J.1123.2010.00965

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The method of high performance liquid chromatographic (HPLC) fingerprint analysis for flavonoids from Houttuynia cordata Thunb. was established with uniform experimental design and information theory evaluation. The fingerprint similarity of 10 batches of Houttuynia cordata Thunb., which were planted under the same cultivation conditions, was evaluated with the developed method and the fingerprint evaluation software proposed by our laboratory. The similarity was greater than 0.90. The contents of rutin, quercitrin and quercetin were 0.25%~0.34%, 0.27%~0.37% and 0.012%~0.016%, respectively. Furthermore, obvious difference was observed among the fingerprints of three kinds of flavonoids produced from different seasons and different parts through principal component analysis and content determination, and the difference from medicinal parts was greater than that from season. This method provide reliable basic information for the specification of flavonoids from Houttuynia cordata Thunb. in the pharmaceutical and medicinal practical application.

Influence of selector configurations of biselector chiral stationary phases on enantioseparation

ZHANG Juan, WEI Wenjuan, CHEN Wei, WU Yuanxin, BAI Zhengwu

2010, 28 (10): 971-976. DOI: 10.3724/SP.J.1123.2010.00971

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In order to investigate the influence of selector configurations of a biselector chiral stationary phase (CSP) on its chiral recognition, a new biselector CSP was prepared in this work using (1S,2S)-(~)-1,2-diphenylethylenediamine (DPEDA) and L-(~)-dibenzoyl tartaric acid (DBTA) as the chiral origins. The enantioseparation ability of the biselector CSP was evaluated towards chiral analytes of different structures under normal, polar organic and reverse phase modes. The chromatographic separation results showed that the enantioseparation ability of the CSP was equivalent to that of another biselector CSP in previous work, which was derived from (1R,2R)-(+)-1,2-DPEDA and L-(~)-DBTA. However, the chiral compounds separated on the two CSPs were not identical. The influence of selector configurations of biselector CSPs on the chiral recognition was discussed. In the event that the two selectors in a biselector CSP were prepared from different chiral compounds, the stereo-configurations of the two selectors cannot simultaneously match the ones of a chiral analyte, thus causing the decrease in the enantioseparation ability of the biselector CSP.

Preparation and evaluation of an eremomycin-bonded chiral monolithic column for capillary electrochromatography

LEI Wen, ZHANG Lingyi, WAN Li, ZHU Yaxian, QIN Sasa, ZHANG Weibing

2010, 28 (10): 977-983. DOI: 10.3724/SP.J.1123.2010.00977

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Based on the high activity of epoxy group of glycidyl methacrylate monolith, eremomycin-bonded chiral stationary phase (CSP) which has 22 different types of chiral centers was prepared by a one-step derivatization process. The preparation conditions were optimized and the preparation can be carried out in a wide pH range (6.0~9.0). The optimized concentration of eremomycin reactant solution was 42 g/L. The optimized method was simple and mild. Prepared CSP was evaluated by separating racemic mixtures of five amino acids and a chiral drug (rosiglitazone) in capillary electrochromatography mode and all of enantiomers were baseline separated. Analysis time of each pair of enantiomers was less than 4 min, so that rapid analysis can be achieved. The effects of organic modifier, buffer pH, and buffer concentration on the separation were investigated. It shows that eremomycin-bonded CSP has good chiral recognition ability. Chiral recognition mechanisms of different solutes on eremomycin-bonded CSP are discussed.

Determination of mannitol, monosaccharides and lactulose in mouse urine by high performance anion exchange chromatography coupled with pulsed amperometric detection

ZHOU Li, LIU Ju, ZHENG Ting, DING Hui, SHI Chaoou

2010, 28 (10): 984-988. DOI: 10.3724/SP.J.1123.2010.00984

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A method of high performance anion exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD) was established for the determination of mannitol, monosaccharides (galactose, glucose, mannose and fructose) and lactulose in mouse urine. The samples were first centrifuged, and then filtered through molecular film to eliminate the proteins. The analysis was performed on a CarboPacTM PA1 column using gradient elution with water and 250 mmol/L sodium hydroxide as the mobile phase. All of the six carbohydrates had good linear relationships (0.988≤r2≤0.999) in the range of 0.1~5.0 mg/L. The recoveries were between 95.5% and 104.2% and the limits of detection were between 0.0013 and 0.004 8 mg/L. The method is accurate, fast and simple. It can be used to analyse six carbohydrates simultaneously and track the metabolic relationships among mannitol, monosaccharides and lactulose during the metabolism of the carbohydrates.

Determination of 2-methyl benzofuran and 2,4-diphenyl-4-methyl- 1-pentene in industrial phenol by solid-phase microextraction coupled with gas chromatography

LOU Dawei, SUN Xiuyun, YANG Jixue, LI Zien, NIU Chunfang, ZHAO Fei, JIANG Guoyu, HU Chunfu, NIU Zhimeng, JIN Hui

2010, 28 (10): 989-992. DOI: 10.3724/SP.J.1123.2010.00989

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An analytical method based on solid-phase microextraction (SPME) coupled with gas chromatography for the determination of organic impurities (2-methyl benzofuran and 2,4-diphenyl-4-methyl-1-pentene) in industrial phenol was developed. The SPME parameters such as extraction temperature, extraction time, and the desorption time were optimized. The optimized parameters were as follows: extraction temperature was 20 ℃, extraction time was 10 min, and desorption time was 30 s. The results demonstrated that the linearities of calibration curves were good in the ranges of 0.05~1.06 mg/L and 0.05~0.99 mg/L with the correlation coefficients of 0.990 and 0.992 for 2-methyl benzofuran and 2,4-diphenyl-4-methyl-1-pentene, respectively. The limits of detection (LODs) were 0.5 and 1.6 μg/L for 2-methyl benzofuran and 2,4-diphenyl-4-methyl-1-pentene, respectively. The relative recoveries were 104% and 113% for 2-methyl benzofuran and 2,4-diphenyl-4-methyl-1-pentene at the spiked level of 0.1 mg/L with triplicate determination. The method is simple, rapid and sensitive for the quantitative analysis of trace organic impurities in industrial phenol.

Determination of tetraethyllead in water by gas chromatography-mass spectrometry

YANG Lili, WANG Meifei, LI Juan, HU Enyu

2010, 28 (10): 993-996. DOI: 10.3724/SP.J.1123.2010.00993

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A new method for the determination of tetraethyllead (TEL) in water by gas chromatography-mass spectrometry (GC-MS) has been developed. The TEL in water samples (200 mL) was extracted with hexane (50 mL) by adding 20 g NaCl, then the extracted solution was concentrated into 1.0 mL and the internal standard (naphthalene-d8) solution was added to every concentrated solution. The pretreated samples were analyzed by GC-MS. An amount of 1.0 μL solution was injected onto an HP-5ms capillary column (30 m×0.25 mm×0.25 μm) and determined by GC-MS in selected ion monitoring (SIM). The selected monitoring ions were m/z 136, 236, 237, 294 and 295. The m/z 295 was selected as quantitative ion for TEL and m/z 136 for the internal standard. The method had good linearity over the tested concentration range of 0.02~0.40 mg/L (r=0.9998) for TEL. The analytical performance characteristics of the proposed procedure were as follows: the detection limit for TEL in 200 mL water sample was 0.04 μg/L. The average recoveries and the relative standard deviations of TEL were 92.2%~103% and less than 13.3%, respectively. The method is rapid, convenient and accurate for the determination of water samples.

Determination of decoquinate in chicken meat by high performance liquid chromatography-tandem mass spectrometry

CHEN Ruiqing, YU Daojin, CHEN Feng, HUANG Yifan

2010, 28 (10): 997-1000. DOI: 10.3724/SP.J.1123.2010.00997

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A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the determination of decoquinate (DEC) residue in chicken meat. The sample was extracted with acetonitrile, cleaned-up with hexane, and purified with solid phase extraction (SPE) cartridge. The mobile phase was acetonitrile (containing 0.1% formic acid) and water (containing 0.1% formic acid). The analyte was identified by positive electrospray ionization (ESI+) mode and multiple reaction monitoring (MRM) mode. The results showed as follows: The calibration curve showed good linearity within the concentrations of 1~200 μg/L with the correlation coefficient (r2)＞0.99. At the spiked levels of 1, 10 and 100 μg/kg, the recoveries of DEC were 78.2%~107.4%. The relative standard deviations (RSDs) of intra- and inter-days were both less than 15%. The limit of detection of DEC was 0.25 μg/kg and the limit of quantification was 0.5 μg/kg. The method is simple, sensitive and accurate in the determination of DEC residue, which can meet the requirements of the domestic and international legislations.

Determination of epigoitrin and goitrin in Isatidis Radix by chiral high performance liquid chromatography

NIE Lixing, WANG Gangli, DAI Zhong, LIN Ruichao

2010, 28 (10): 1001-1004. DOI: 10.3724/SP.J.1123.2010.01001

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A Chiralpak IC column (250 mm×4.6 mm, 5μm) was used to establish normal phase high performance liquid chromatographic (NP-HPLC) method for the chiral separation of epigoitrin (R-goitrin) and goitrin (S-goitrin) in Isatidis Radix. The composition of mobile phase, flow rate and column temperature were optimized to get better resolution. The final chromatographic conditions were established as follows: n-hexane-isopropanol (90:10, v/v) as the mobile phase with a flow rate of 0.8 mL/min, the detection wavelength at 245 nm and the column temperature at 20 ℃. Under the above optimized chromatographic conditions, the resolution of 3.4 was achieved for epigoitrin and goitrin. The limit of detection (LOD) was 2.0 mg/L. The linear range was 0.02~2.0 g/L. The average recovery was 101% with the relative standard deviation (RSD) lower than 3.0% (n=6). The proposed method was exclusive by determining the antivirus epigoitrin and its enantiomer separately, which provided the effective quality control of Isatidis Radix.

Simultaneous determination of three components in Pediatric Paracetamol and Amantadine Hydrochloride Granules using high performance liquid chromatography with gradient elution and dual wavelength detection

ZHANG Yihua, JIANG Jianguo, HAN Xuejing, ZHANG Shiliang

2010, 28 (10): 1005-1008. DOI: 10.3724/SP.J.1123.2010.01005

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A high performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of paracetamol, caffeine and chlorphenamine maleate in Pediatric Paracetamol and Amantadine Hydrochloride Granules. The separation was performed on a Diamonsil C18 column with 0.1% triethylamine aqueous solution (adjusted pH to 3.7±0.5) and acetonitrile as the mobile phase of gradient elution at a flow rate of 1.0 mL/min. The detection wavelengths were set at 280 nm and 210 nm. The linearities were wide (2.4~60, 0.14~3.6, 0.019~0.48 μg for paracetamol, caffeine and chlorphenamine maleate, respectively)and the average recoveries were not less than 99.0%. The method is simple, accurate and reproducible. It is a good method for the quality control of Pediatric Paracetamol and Amantadine Hydrochloride Granules.

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