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Chinese Journal of Chromatography
2014, Vol. 32, No. 11
Online: 08 November 2014

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Application of three-way data analysis (second-order tensor decomposition) algorithms in analysis of liquid chromatography ZHANG Jin, PENG Qianrong, XU Longquan, YANG Min, WU Aijing, YE Shizhu 2014, 32 (11):  1165-1171.  DOI: 10.3724/SP.J.1123.2014.07036 Abstract ( 573 )   [Full Text(HTML)] () PDF (1465KB) ( 200 )   Using dropline separation, tangent skimming, and triangulation to estimate the area of an overlapping chromatographic peak might contribute to a large deviation. It is easy, however, to eliminate these errors caused by geometric segmentation using three-way data analysis (second-order tensor decomposition) algorithms. This method of chromatographic analysis has many advantages: automation, anti-interference, high accuracy in the resolution of overlapping chromatographic peaks. It even makes the final goal of analytical chemistry achievable without the aid of complicated separation procedures. The core of this method is the process of utilizing useful information and building models through chemometric algorithms. Three-way chromatographic data set can be divided into trilinear dataset and nontrilinear dataset, correspondingly, three-way data analysis (second-order tensor decomposition) algorithms can be divided into trilinear algorithms and nontrilinear algorithms. In this paper, three-way calibration used in liquid chromatography for complex chemical systems in the last decade is reviewed, and focused on sample pretreatment, auxiliary algorithms, the combination and comparison of correction algorithms.

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Structure identification of reactive dyes by high performance liquid chromatography-photodiode array detection/mass spectrometry FU Xinmei, ZHANG Rong, WU Zuwang 2014, 32 (11):  1172-1180.  DOI: 10.3724/SP.J.1123.2014.07038 Abstract ( 528 )   [Full Text(HTML)] () PDF (1011KB) ( 247 )   Based on years of experience on analyzing reactive dyes by high performance liquid chromatography-photodiode array detection/mass spectrometry (HPLC-DAD/MS), the essential applications for current structure identification of the commercial reactive dyes are summarized in three aspects. Commercial dyes always include several kinds of components. They are assistants for increasing solubility of synthetic dyes, multi-color synthetic dyes and their by-products derived from synthesis and storage. HPLC-DAD/MS technique can separate most of the components, and provide UV-Vis spectra and mass spectra individually. The separation and analysis can be achieved only through one injection without pre-purification of commercial dyes. Compared with traditional analytical methods, HPLC-DAD/MS technique reduces greatly not only the workload of analysis but also provides fully the actual compositions of the dyestuff. The reactive groups can react with ethanolamine or diethanolamine under moderate condition without structure destruction of dyes. The molecular masses before and after derivatization can be determined by MS, and then the type and number of reactive groups can be ascertained by so called "mass difference by derivative method". The chromophore of the dye can be identified by full spectrum scanning function of DAD. HPLC-DAD/MS analytical technique is very special and useful for the structure analysis of multi-component mixed commercial dyes. As examples, the identifications of three multi-component mixed structures of commercial dyes (Reactive Gray, Reactive Supra Black and Reactive Marine Blue) were given.

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Analysis of rice leaves proteomes by liquid chromatography-tandem mass spectrometry based on the purification using a novel affinity detergent removal spin column CAO Xiaolin, GONG Jiadi, CHEN Mingxue, YU Shasha, BIAN Yingfang, CAO Zhaoyun 2014, 32 (11):  1181-1186.  DOI: 10.3724/SP.J.1123.2014.06035 Abstract ( 718 )   [Full Text(HTML)] () PDF (1072KB) ( 225 )   A purification method was established for the analysis of proteomes in rice leaves based on a novel detergent removal spin column (DRSC). The proteins were extracted by phenol protein extraction method followed by sodium dodecyl sulfate (SDS) lysis. The lysate was purified by the detergent removal spin column and the enzymolytic peptides were detected by the nanoflow liquid chromatography-hybrid linear trap quadrupole orbitrap mass spectrometry (nanoLC-LTQ/Orbitrap). In terms of SDS removal efficiencies and protein identification, the method of DRSC was compared with those of filter aided sample preparation (FASP) and acetone precipitation. As a result, there were good efficiencies (>95%) of SDS removal for the three methods. With the DRSC purification strategy, 563 proteins were identified from rice leaves, while only 196 and 306 proteins were identified by FASP and acetone precipitation procedures respectively, in spite of certain complementarities among these identified proteins by the three methods. DRSC is suitable for proteins with various relative molecular masses and pI values. However, there were similar losses of proteins with different relative molecular masses and pI values with the other two methods. Using the established method, 588 proteins were identified by once injection analysis. According to the molecular functions, 296 proteins with at least two identified peptides can be classified into eight categories with binding activity, enzyme activity, transporter activity, inhibitor activity, structural constitute, catalytic activity, other and unknown functions. The method provides technical reference for conducting rice proteomes.

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Application of precursor ion scanning method in rapid screening of illegally added phosphodiesterase-5 inhibitors and their unknown derivatives in Chinese traditional patent medicines and health foods SUN Jing, CAO Ling, FENG Youlong, TAN Li 2014, 32 (11):  1187-1196.  DOI: 10.3724/SP.J.1123.2014.06015 Abstract ( 815 )   [Full Text(HTML)] () PDF (3114KB) ( 194 )   The compounds with similar structure often have similar pharmacological activities. So it is a trend for illegal addition that new derivatives of effective drugs are synthesized to avoid the statutory test. This bring challenges to crack down on illegal addition behavior, however, modified derivatives usually have similar product ions, which allow for precursor ion scanning. In this work, precursor ion scanning mode of a triple quadrupole mass spectrometer was first applied to screen illegally added drugs in complex matrix such as Chinese traditional patent medicines and healthy foods. Phosphodiesterase-5 inhibitors were used as experimental examples. Through the analysis of the structure and mass spectrum characteristics of the compounds, phosphodiesterase-5 inhibitors were classified, and their common product ions were screened by full scan of product ions of typical compounds. Then high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method with precursor ion scanning mode was established based on the optimization of MS parameters. The effect of mass parameters and the choice of fragment ions were also studied. The method was applied to determine actual samples and further refined. The results demonstrated that this method can meet the need of rapid screening of unknown derivatives of phosphodiesterase-5 inhibitors in complex matrix, and prevent unknown derivatives undetected. This method shows advantages in sensitivity, specificity and efficiency, and is worth to be further investigated.

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Measurement of sialic acid from lipoproteins and human plasma by liquid chromatography-tandem mass spectrometry GUO Shoudong, SANG Hui, YANG Nana, KAN Yujie, LI Fuyu, LI Yu, LI Fangyuan, QIN Shucun 2014, 32 (11):  1197-1200.  DOI: 10.3724/SP.J.1123.2014.07002 Abstract ( 710 )   [Full Text(HTML)] () PDF (828KB) ( 263 )   A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established to quantify sialic acid (N-acetylneuraminic acid, NANA) from lipoproteins and human plasma. The method was used to investigate the different contents of NANA from lipoproteins between diabetic with an average age of 51.6 years and healthy participants with an average age of 50.7 years. The NANA from lipoprotein samples was hydrolyzed by acetic acid (pH=2) at 80 ℃ for 2 h and analyzed by the optimized LC-MS/MS method after high speed centrifugation and filtration. The limits of detection and quantification of NANA were 7.4 and 24.5 pg, respectively. The linear range was 2.5-80 ng/mL for NANA and the correlation coefficient (R2) was more than 0.998. The levels of NANA in the plasma of type Ⅱ diabetics and healthy participants were (548.3±88.9) and (415.3±55.5) mg/L, respectively; and the levels of NANA from very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL) of the type Ⅱ diabetics and the healthy participants were (4.91±0.19), (6.95±0.28), (3.61±0.22) μg/mg and (2.90±0.27), (7.03±0.04), (2.40±0.09) μg/mg, respectively. The sialic acid levels of VLDL and HDL from the type Ⅱ diabetics were markedly higher than those of the corresponding healthy participants with the similar ages (P<0.01). The method can rapidly determine the sialic acid from lipoproteins, and is reproducible and time saving.

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Determination of 12 bisphenol substances in functional foods by QuEChERS and high performance liquid chromatography-tandem mass spectrometry GAO Mengjie, ZHOU Yao, SHENG Yonggang, ZHAO Shanzhen, DENG Xiaojun, GUO Dehua, DING Zhuoping, WANG Guomin, PENG Tao 2014, 32 (11):  1201-1208.  DOI: 10.3724/SP.J.1123.2014.06037 Abstract ( 539 )   [Full Text(HTML)] () PDF (2406KB) ( 176 )   A method based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the simultaneous determination of 12 bisphenol substances in functional foods (powder, tablet, capsule) was presented. The samples were extracted by acetonitrile containing 1% (v/v) acetic acid followed by further cleaned up using matrix solid-phase dispersion to remove matrix interferences. The separation of the 12 bisphenol substances was performed on a Thermo Aquasil C18 column (150 mm×4.6 mm, 3.0 μm), and determined in the positive and negative MRM modes by MS/MS using matrix-matched external standard method. The results demonstrated that the calibration curves were of good linearity with the correlation coefficients greater than 0.99. The limits of detection (LODs, S/N>3) were in the range of 0.1-0.5 μg/kg and the limits of quantitation (LOQs, S/N>10) were 0.4-1.7 μg/kg. The recoveries of the 12 bisphenol substances spiked at three levels (2.0, 5.0 and 10.0 μg/kg) in matrix ranged from 60.5% to 116.3% with the relative standard deviations (RSDs) of 6.8% to 11.2%. The established method is simple, time-saving and sensitive. It can meet the requirements for current regulations while achieving qualitative and quantitative determination of the 12 bisphenol substances in functional foods.

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Simultaneous determination of three estrogens in feed by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry XIAO Quanwei, WU Wenlin, YANG Wanlin, LIANG Run, LI Shaobo, LIU Lingli 2014, 32 (11):  1209-1213.  DOI: 10.3724/SP.J.1123.2014.07039 Abstract ( 584 )   [Full Text(HTML)] () PDF (854KB) ( 119 )   A method was developed for the simultaneous determination of three estrogens (17β-estradiol, estradiol benzoate, estradiol valerate) in feed by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS). After the sample was extracted by acetonitrile and cleaned-up on a Heaion C18 solid phase extraction (SPE) column, the three estrogens were separated by an ACQUITY UPLC BEH C18 column (50 mm×2.1 mm, 1.7 μm) with gradient elution using acetonitrile and 0.1% ammonia solution as mobile phases and finally confirmed and quantified in multiple reaction monitoring (MRM) mode. The internal standard calibration curves were used for the quantification. The results showed that all the estrogens were determined with excellent linear relationships from 10 μg/L to 200 μg/L for 17β-estradiol and estradiol valerate, and from 5 μg/L to 200 μg/L for estradiol benzoate. The correlation coefficients (r) of the three estrogens were not lower than 0.996. The limits of detection for 17β-estradiol, estradiol benzoate and estradiol valerate were 7 μg/kg, 5 μg/kg and 7 μg/kg, respectively. The average recoveries were 96.5%-102.0%. The results demonstrated that the developed method can simultaneously determine the three estrogens in feed with advantages of simple pretreatment, rapid analysis, low limit of detection and high accuracy.

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Preparation of microcystin-LR molecularly imprinted polymer coated stir bar and its adsorptive performances QIU Xiuzhen, LIANG Yong, GUO Huishi 2014, 32 (11):  1214-1218.  DOI: 10.3724/SP.J.1123.2014.07001 Abstract ( 609 )   [Full Text(HTML)] () PDF (3195KB) ( 245 )   An effective method for the preparation of magnetic molecularly imprinted polymers (MIPs) on attapulgite (ATP) using microcystin-LR (MC-LR) as template molecule through reversible addition fragmentation chain transfer (RAFT) radical polymerization was reported. A novel MIPs stir bar sorptive extraction (SBSE) coating was prepared by sol-gel method. The structure and morphology of MIPs were characterized by infrared spectroscopy (IR) and transmission electron microscopy (TEM). The adsorption performance of SBSE coated with MC-LR was studied by high performance liquid chromatography (HPLC). The results showed that under the optimized experimental conditions, the present method has high selectivity to MC-LR. A good linearity was achieved for MC-LR over the range of 0.010-5.0 mg/L and the limit of detection (S/N=3) was found to be as low as 0.27 μg/L. The proposed method was successfully applied to the determination of MC-LR in water samples. The average recoveries ranged from 83.33% to 100.07% with the relative standard deviations (RSDs) of 1.40%-9.17% at three spiked levels (20, 40 and 80 μg/L). The developed method is rapid, selective and sensitive, and adapts to the analysis of trace MC in water samples.

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Enantioseparation and determination of atenolol enantiomers in tablets on a β-cyclodextrin-based chiral stationary phase by high performance liquid chromatography CHENG Biaoping, LI Laisheng, ZHOU Rendan, NIE Guizhen, ZHANG Hongfu 2014, 32 (11):  1219-1224.  DOI: 10.3724/SP.J.1123.2014.07018 Abstract ( 651 )   [Full Text(HTML)] () PDF (1606KB) ( 207 )   A novel dinitrophenyl ether β-cyclodextrin-bonded chiral stationary phase (NESP) for HPLC was prepared with ordered mesoporous SBA-15 as matrix. The fast enantioseparation of atenolol enantiomers on the new stationary phase was achieved through the optimization of mobile phase composition, column temperature and other factors in polar organic solvent mode. The optimized composition of mobile phase was acetonitrile/methanol/glacial acetic acid/triethylamine (90:10:2.5:3.0, v/v/v/v) at the flow rate of 0.5 mL/min. The column temperature was set at 20 ℃. The detection wavelength was 275 nm. The resolution of atenolol enantiomers was 1.73 with a rather short analysis time, about 20 min, under the above conditions. The atenolol was extracted with methanol from the tablets and analyzed by direct injection for HPLC. A new quantitative method of atenolol enantiomers in tablets was established after the condition optimization. The good linear relationships for two atenolol enantiomers were observed in the range of 2.5-100 mg/L with r of 0.9992 and 0.9989, respectively. The recoveries of atenolol enantiomers in tablet samples were 94.60%-97.24%. The relative standard deviations (RSDs) of this method were not greater than 0.92% for intra-day and 1.86% for inter-day, respectively. The detection limits (S/N=3) of concentrations were less than 0.2 mg/L for both enantiomers. The established method is simple and of high selectivity, high recovery and low cost for enantiomer analysis by using homemade cyclodextrin-based chiral column. It has a good application prospect for the fast quality control and the pharmacokinetics study of chiral drugs.

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Application of 1-ethyl-3-methyl imidazole L-lactate as the chiral ligand for the enantioseparation of amino acids HUANG Lu, YU Lishuang, CHEN Yiting 2014, 32 (11):  1225-1229.  DOI: 10.3724/SP.J.1123.2014.06040 Abstract ( 636 )   [Full Text(HTML)] () PDF (1549KB) ( 247 )   Enantioseparation of tryptophan enantiomers (Trys), tyrosine enantiomers (Tyrs) and phenylamine enantiomers (Phes) by chiral ligand exchange capillary electrophoresis (CLE-CE) using 1-ethyl-3-methyl imidazole L-lactate ([EMIM][L-Lac]) as the chiral ligand was studied. The effects of background electrolytes and central ions, the molar ratio and concentration of the chiral ligand and central ion, running buffer solution pH on the enantioseparation of Trys, Phes and Tyrs were investigated. Good enantioseparation of three pairs of enantiomers were obtained with 40.0 mmol/L [EMIM][L-Lac] and 20.0 mmol/L cupric chloride (pH 4.5). To validate the good behavior of [EMIM][L-Lac], L-lactate (L-Lac) was further used as the chiral ligand for the enantioseparation of Trys. The contrast experiment showed that Trys could only be partially enantioseparated by L-Lac. Moreover, the enantioseparation was improved by adding 1-ethyl-3-methyl imidazole acetate (EMIM-Ace) which markedly prolonged the migration time of Trys to more than 30 min. In contrast, the migration time of Trys was obtained in 15 min by [EMIM][L-Lac]. Finally, the enantioseparation mechanism was further discussed. The experimental results showed that in the EMIM-Ace assisting L-Lac system, EMIM-Ace was only used to suppress the electroosmotic flow and was not involved in the chiral ligand exchange reaction, while in the [EMIM][L-Lac] system, the chiral ligand taking part in the reaction was mainly unionized [EMIM][L-Lac] rather than L-Lac formed by ionized L-Lac ions.

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Rapid detection of eight fluorescent whitening agents in textile by ultra performance convergence chromatography TANG Juan, DING Youchao, CAO Xizhong, QI Yan, QIAN Kai 2014, 32 (11):  1230-1235.  DOI: 10.3724/SP.J.1123.2014.07030 Abstract ( 632 )   [Full Text(HTML)] () PDF (906KB) ( 258 )   An accurate quantitative and confirmative method has been developed for the determination of eight fluorescent whitening agents (FWAs) in textile by ultra performance convergence chromatography (UPC2) coupled with photo diode array (PDA) detection, including 1,2-bis(5-methyl-2-benzoxazole)ethylene (PF), 7-diethylamino-4-methylcoumarin (SWN), 2,2'-(2,5-thiophenediyl)bis(5-(1,1-dimethylethyl)-benzoxazol (OB), 2-[4-[2-[4-(2-benzoxazolyl) phenyl]ethenyl]phenyl]-5-methyl-benzoxazol (KSN), 1,4-bis(2-cyanostyryl)benzene (ER-Ⅰ), 1-(2-cyanostyryl)-4-(4-cyanostyryl)benzene (ER-Ⅱ), 2,2'-(1,4-naphthalenediyl)bis-benzoxazol (KCB), 4,4'-bis[2-(2-methoxyphenyl)ethenyl]-1,1'-biphenyl (FP). The sample was extracted with xylene and concentrated by a rotary evaporator, and then qualitatively and quantitatively analyzed by UPC2. The separation of target compounds was achieved on an ACQUITY UPC2 HSS C18 SB column (100 mm×3.0 mm, 1.8 μm) by a gradient elution with supercritical carbon dioxide and methanol as mobile phases. External standard method was used for the quantitative determination and the calibration curves showed good linearity in the concentration range of 1.0-20.0 mg/L for the eight target compounds with correlation coefficients not less than 0.9991. The limits of quantification of the eight compounds (LOQs, S/N=10) were 0.70-0.95 mg/L. The average recoveries of the eight compounds ranged from 90.9% to 96.5% at the spiked levels of 2.0, 5.0, 10.0 mg/kg with the relative standard deviations (RSDs) of 2.8%-4.2%. The method is simple, accurate and time-saving with high sensitivity, and can be used for the rapid determination of the eight FWAs in textile.

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Molecular composition of saturated hydrocarbons in diesels by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry NIU Luna, LIU Zelong, ZHOU Jian, CAI Xinheng, TIAN Songbai 2014, 32 (11):  1236-1241.  DOI: 10.3724/SP.J.1123.2014.07015 Abstract ( 580 )   [Full Text(HTML)] () PDF (2279KB) ( 232 )   An analytical method for separation and identification of the saturated hydrocarbons in diesels at molecular level by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOF MS)was established. The saturated hydrocarbons were pre-separated from diesel samples by solid phase extraction before GC×GC-TOF MS analysis. More than 1000 individual compounds (including paraffins, naphthenes and olefins) in coker diesel were tentatively identified based on NIST library search, mass spectrum resolution, boiling point distribution law and separation characteristics. Normal paraffins showed great regularity and could be identified easily through the relative position with pristane and phytane. The cyclic alkanes arranged above paraffins with the increasing number of rings. The normal alkyl cyclohexanes and cyclopentanes were well distinguished due to the difference of their polarity. Normal α -olefins which were often neglected in the past were also identified. With the support of the above-introduced identification, the distribution by structural type and carbon number were presented using peak area normalization. This analytical method was successfully used to investigate the molecular composition of saturated fractions in different diesel samples. All the results indicated that the molecular compositions of saturates in catalytic cracking diesel and coker diesel were significantly different because of the processing mechanism. This method provided technical support for the characterization of saturated hydrocarbons in diesels and the investigation of processing mechanism.

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Sample pretreatment for the measurement of phthalate esters in complex matrices LIANG Jing, ZHUANG Wan'e, LIN Fang, YAO Wensong, WEN Yuyun, OU Yan, GONG Zhenbin 2014, 32 (11):  1242-1250.  DOI: 10.3724/SP.J.1123.2014.07051 Abstract ( 785 )   [Full Text(HTML)] () PDF (950KB) ( 252 )   Sample pretreatment methods for the measurement of phthalate esters (PAEs) by gas chromatography-mass spectrometry (GC-MS) in various complex matrices, including sediment, soil, suspended particle matter, urban surface dust, Sinonovacula Constricta, cosmetic, leather, plastic and coastal/estuarine seawater, were proposed. The pretreatment which was appropriate for GC-MS detection was focused on the investigation and optimization of operating parameters for the extraction and purification, such as the extraction solvent, the eluant and the adsorbent of solid phase extraction. The results of the study of pretreatment for various complex matrices showed that methylene chloride was the best solvent for the ultrasonic extraction when solid-liquid extraction was used; silica gel was the economical and practical adsorbent for solid-phase extraction for purification; C18 was the most commonly adsorbent for preconcentration of PAE in coastal/estuarine seawater sample; the mixed solution of n-hexane and ethyl acetate with a certain proportion was the suitable SPE eluent. Under the optimized conditions, the spiked recoveries were above 58% and the relative standard deviations (RSDs) were less than 10.5% (n=6). The detection limits (DL, 3σ) were in the range of 0.3 μg/kg (dibutyl phthalate)-5.2 μg/kg (diisononyl phthalate) for sediment, and 6 ng/L (dipropyl phthalate)-67 ng/L (diisodecyl phthalate) for costal/estuarine seawater. The pretreatment method for various complex matrices is prominent for the measurement of the 16 PAEs with GC-MS.

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Generic method for determination of volatile organic solvents in cosmetics DA Jing, HUANG Xianglu, WANG Gangli, CAO Jin, ZHANG Qingsheng 2014, 32 (11):  1251-1259.  DOI: 10.3724/SP.J.1123.2014.07020 Abstract ( 634 )   [Full Text(HTML)] () PDF (920KB) ( 279 )   A generic screening, confirmation and determination method was established based on 36 commonly used volatile organic solvents in cosmetics by headspace gas chromatography-mass spectrometry (GC-MS). This method included a database for pilot screening and identification of those solvents and their quantitative method. Pilot screening database was composed by two sections, one was household section built by two columns with opposite polarities (column VF-1301ms and DB-5ms) using retention index in different column systems as qualitative parameter, and the other was NIST MS search version 2.0. Meanwhile, the determination method of the 36 volatile solvents was developed with GC-MS. Cosmetic samples were dissolved in water and transferred to a headspace vial. After 30 min equilibration at 60 ℃, the samples were analyzed by GC-MS equipped with a capillary chromatographic column VF-1301ms. The external calibration was used for quantification. The limits of detection were from 0.01 to 3.3 μg/g, and the recoveries were from 60.77% to 126.6%. This study provided a generic method for pilot screening, identification, and quantitation of volatile organic solvents in cosmetics, and may solve the problem that different analytical methods need to be developed for different targeted compounds and pilot screening for potential candidate solvent residues.

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Determination of 19 phthalate esters in cucumbers using QuEChERS coupled with gas chromatography-triple quadrupole mass spectrometry SUN Xin, QI Li, QIN Tingting, WANG Minglin 2014, 32 (11):  1260-1265.  DOI: 10.3724/SP.J.1123.2014.05004 Abstract ( 644 )   [Full Text(HTML)] () PDF (854KB) ( 295 )   An efficient method using QuEChERS equipped with triple quadrupole GC-MS/MS for the simultaneous detection of 19 phthalate acid ester residues in cucumbers was established. The phthalate acid esters were extracted from cucumber samples by ultrasonic with acetonitrile. The extracts were salted out and centrifuged with anhydrous magnesium sulfate and sodium chloride. The supernatants were enriched by vacuum distillation, and then purified by C18 adsorbent. The 19 phthalate esters were separated on an HP-5ms UI column (30 m×0.25 mm×0.25 μm), and determined using MS/MS in multiple reactions monitoring mode. The method showed favorable qualitative and quantitative analysis of the phthalate esters with good linearity (r ≥ 0.9995) in the linear range of 10-5000 μg/kg and the limits of detection (LODs) were 0.2-3.5 μg/kg. With the proposed method, the recoveries were evaluated in cucumbers at the spiked levels of 10, 100 and 500 μg/kg. The results showed that the average recoveries were ranged from 63.3%-127.8% and the relative standard deviations (RSDs) were 0.5%-13.3%. In short, the proposed method with high sensitivity and good accuracy can meet the determination requirements for multi-residues. Furthermore, the method can be applied for the simultaneous determination of phthalate acid esters in cucumbers.

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Determination of indicator polychlorinated biphenyls in vegetable oils by double clean-up-gas chromatography DING Liping, CAI Chunping, WANG Danhong 2014, 32 (11):  1266-1270.  DOI: 10.3724/SP.J.1123.2014.06010 Abstract ( 570 )   [Full Text(HTML)] () PDF (868KB) ( 188 )   To investigate the residues of seven indicator polychlorinated biphenyls (PCBs) in vegetable oils, a method was established for the determination of trace PCBs in vegetable oils by double clean-up coupled with gas chromatography (GC). After extracted with acetonitrile, the sample extract was concentrated to dryness followed by re-dissolving with hexane. And the solution was pretreated by adding concentrated sulfuric acid followed cleaned-up with silica gel in dispersive solid-phase extraction protocol, then analyzed by GC with external standard method. Under the optimized chromatographic conditions, the analysis was carried out with a capillary column (HP-5, 30 m×0.32 mm×0.25 μm) at a flow rate of 0.8 mL/min, and the sample volume was 1.00 μL. Monitoring with an electron-capture detector, all the target analytes were separated by temperature-programming of the column. Good linearities were obtained in the range of 10-500 μg/L for the seven indicator PCBs with the correlation coefficients greater than 0.999. For different matrices, the limits of detection (S/N=3) and limits of quantitation (S/N=10) were in the range of 1.8-8.9 μg/kg and 5.9-29.8 μg/kg, respectively. At three spiked levels of 10, 20 and 100 μg/kg of the seven indicator PCBs in olive oil, palm oil and peanut oil blank samples, the average recoveries ranged from 71.0% to 105.5% with the RSDs of 4.0%-11.3%. The method is simple, rapid and accurate, and can be used for the routine analysis of the indicator PCBs in vegetable oils.

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Protein enrichment based on large volume recycling injection ZHANG Quanqing, ZHANG Lei, GAO Xiaodi, ZHANG Weibing, ZHANG Qinghe 2014, 32 (11):  1271-1274.  DOI: 10.3724/SP.J.1123.2014.09019 Abstract ( 498 )   [Full Text(HTML)] () PDF (977KB) ( 133 )   Biological proteins have great differences in size, hydrophobicity, pH and relative abundance. Especially, the relative contents of high-abundance proteins and low abundance proteins can reach 11 orders of magnitude or more in blood. However, the contents of proteins which have an important impact on the biological function and have related to major diseases are usually very low in body fluids or tissues. So, it is very meaningful to detect the low abundance proteins in biological samples. A method of large volume recycling injection was developed as a new sample enrichment technology in this study. The low absolute contents of proteins in a sample were improved by increasing the volume of sample, and the enrichment efficiency was also increased with the addition of injection times. With the pork liver protein as an example, under the optimized conditions, the representative contents which were no peaks or little peaks and more peaks with low signals were studied. The contents of peaks at the retention times of 11.38 min and 12.58 min were enriched by 11 time injections of 500 μL each time. The enrichment factors respectively reached 52 and 61 which were closed to theoretical values. This method can be used for the enrichment of biological protein samples.

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Determination of principal components and related substances in adenosine disodium triphosphate preparation by ion chromatography SHAN Guangzhi, ZONG Yanping, WANG Xiao, LU Jinghua 2014, 32 (11):  1275-1279.  DOI: 10.3724/SP.J.1123.2014.07012 Abstract ( 1148 )   [Full Text(HTML)] () PDF (848KB) ( 311 )   A new method was developed for the determination of adenosine disodium triphosphate (ATP-Na2) and its related substances in ATP-Na2 preparation by ion chromatography (IC). The sample was diluted with ultrapure water and filtrated by 0.22 μm polyether sulfone filter membrance, and then analyzed by IC directly without any more pretreatment. The analysis was performed on a Dionex IonPac AS11-HC column(250 mm×4 mm) and a guard column IonPac AG11-HC (50 mm×4 mm). A KOH eluent generator cartridge was used for gradient elution at the flow rate of 1.0 mL/min. The detection was performed by a Dionex suppressed (Dionex AERS 500 4-mm) conductivity detector. The injection volume was 10 μL. The assay was quantitatively completed by external standard method and the related substances were calculated with correction factors. The linear ranges of the method for ATP-Na2, adenosine disodium diphosphate (ADP-Na2) and adenosine disodium monophosphate (AMP-Na2) were 0.000146-1.83 g/L (r=0.9997), 0.000484-1.51 g/L (r=0.9996) and 0.000426-0.804 g/L (r=0.9999), respectively. The average recoveries of ATP-Na2 were 96.50%, 96.57% and 96.77% at three spiked levels. The limits of quantitation (S/N=10) of ATP-Na2, ADP-Na2 and AMP-Na2 were 1.5 ng, 4.8 ng, 4.3 ng, and the limits of detection (S/N=3) were 0.58 ng, 1.21 ng, 1.28 ng, respectively. The results demonstrated that the system has the advantages of high sensitivity, facile automation and simple sample pretreatment. The method is suitable for the quality control of adenosine disodium triphosphate preparations.

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Determination of oxygenates in syngas-to-olefin products by solid phase extraction combined with gas chromatography-mass spectrometry LIU Junyan, TIAN Wenqing, LI Jiwen, WANG Chuan, GU Songyuan 2014, 32 (11):  1280-1285.  DOI: 10.3724/SP.J.1123.2014.06043 Abstract ( 488 )   [Full Text(HTML)] () PDF (897KB) ( 224 )   The syngas-to-olefin (SGTO) products mainly consist of hydrocarbons along with small amounts of oxygenates as the byproducts. A C18 solid-phase extraction (SPE) column was used for oxygenates enrichment in SGTO products. As the hydrophobic compounds, the hydrocarbons had stronger interaction with a C18 SPE column than oxygenates. Under the optimized elution conditions, the oxygenates were first eluted from the C18 SPE column with 60% (v/v) methanol solution. The fraction of oxygenates was then analyzed with gas chromatography-mass spectrometry (GC-MS) for qualification and gas chromatography-hydrogen flame ionization detection (GC-FID) for quantification. The FID response factors of n-alkanol and n-ketone were used for alkanols and ketones quantitative calculation and the method recoveries were 88%-98% and 64%-87% respectively. In the range of 197-4785 mg/L, good linear relationships of the FID responses with the corresponding mass concentrations of the standard samples were obtained with the linear regression coefficients greater than 0.99. Sixty-seven oxygenates were analyzed qualitatively and quantitatively. The results showed that the fraction of the oxygenates mainly consists of alkanols and ketones. The total content of the oxygenates in SGTO products was 6.2%. The enrichment method only requires a very small amount of sample and the total process can be completed within 10 min. The analysis results of SGTO product studies can provide the necessary basic data for SGTO catalysts and dynamics studies.

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Determination of 16 phthalate acid ester residues in health wine by gas chromatography-triple quadrupole mass spectrometry LU Li, GONG Xu, FENG Youlong 2014, 32 (11):  1286-1292.  DOI: 10.3724/SP.J.1123.2014.07011 Abstract ( 694 )   [Full Text(HTML)] () PDF (883KB) ( 188 )   A method for the analysis of sixteen phthalate acid ester (PAE) residues in health wine was developed using gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS). The health wine samples were extracted with n-hexane by liquid-liquid extraction method before analysis. The samples were detected by GC-QQQ-MS with electron impact source (EI) in selected ion monitoring (SIM) mode after extraction. The separation was performed on an HP-5MS capillary column (30 m×0.25 mm×0.25 μm) with temperature programming. The retention time and the fragment ion abundance ratio were used to judge the qualitative results, and the quantitation was performed with standard curve method of the characteristic ion chromatographic peak area-concentration. Eighty-one batches of health wine samples were detected using the method. The results showed that the method had good linear relationships with correlation coefficients (r2) not less than 0.9959. The recoveries of fifteen PAEs ranged from 88.6% to 107.3% except dimethyl phthalate (DMP) which was 52.3%-58.7% in all the three spiked levels with the relative standard deviations of 0.1%-6.8%(RSD, n=6). The limits of detection were between 0.002 mg/L to 0.061 mg/L. The limits of quantification were between 0.005mg/L and 0.202 mg/L. The method is accurate, sensitive, proprietary and suitable for the simultaneous determination of the sixteen phthalate acid esters in health wine.