高效毛细管电泳法测定牛奶和奶粉中残留的三聚氰胺

建立了牛奶和奶粉中三聚氰胺的高效毛细管电泳-二极管阵列检测器(HPCE-DAD)检测方法。使用长度58.5 cm、内径75 μm的毛细管柱,分离电压25 kV,进样量3.5 kPa (35 mbar)×8 s,分离温度25 ℃,缓冲溶液20 mmol/L 柠檬酸-40 mmol/L 磷酸氢二钠(pH 2.6),检测波长232 nm。分析物在1~100 mg/L 范围内线性良好,r2>0.997;牛奶和奶粉的定量限分别为0.5 mg/kg和1.0 mg/kg。在添加水平为定量限浓度至50 mg/kg时的回收率为72.2%~97.3%,相对标准偏差为2.1%~3.9%。     

Determination of urinary catecholamines with capillary electrophoresis after solid-phase extraction

The stabilities of 3,4-dihydroxybenzylamine (DHBA), dopamine, 3-methoxytyramine, normetanephrine and metanephrine standards under acid, base and enzymatic hydrolysis conditions were studied. Basic incubation media were not suitable for 3,4-dihydroxy compounds, but acid and enzymatic hydrolysis conditions were applicable to all the compounds. The results of acid and enzymatic hydrolysis were comparable and the enzymatic hydrolysis was applied to a urine matrix. A method including solid-phase extraction (SPE) with a copolymer sorbent was developed for purification of the urine samples. Due to poor recovery of DHBA, the most frequently used internal standard in catecholamine analysis, this compound was replaced with the 3-O-methoxy structure. The recoveries of the compounds in spiked urine samples in SPE were between 96.4 and 124.4%. The repeatability of the combination of enzymatic hydrolysis and SPE pretreatment was good for all the compounds, except for dopamine and 3-methoxytyramine due to some matrix compounds still interfering with the separation. The analyses were performed with capillary electrophoresis in an ammonium acetate buffer with UV detection. The validation data for the compounds including limit of detection, limit of quantification, linearity and repeatability of the method are presented.     

牛奶样品中新霉素残留量的离子色谱法测定

建立了阴离子交换色谱-脉冲安培检测分析牛奶中新霉素残留量的方法.实验采用三氯乙酸沉淀蛋白,弱阳离子交换固相萃取柱富集净化,处理牛奶样品,并考察了三氯乙酸浓度、样品过柱速度以及洗脱剂浓度等因素对牛奶中新霉素测定结果的影响.牛奶中新霉素的回收率在50.3%～76.9%范围内,基底加标工作曲线的相关系数为0.9949(n=6),线性范围为10.0～160.0ng/mL.所建立的方法可满足牛奶中低新霉素残留量的检测需要.     

Determination of quinolones in milk samples using a combination of magnetic solid-phase extraction and capillary electrophoresis

A magnetic solid-phase extraction (MSPE) method combined with capillary electrophoresis for the simultaneous determination of seven quinolones (QNs) (danofloxacin, ciprofloxacin, marbofloxacin, enrofloxacin, difloxacin, oxolinic acid, and flumequine), using (S)-(+)-6-methoxy-α-methyl-2-naphthaleneacetic acid as internal standard, in milk samples was developed. The variables involved in the preconcentration magnetic procedure were: the composition of the magnetic support composition, the sample pH, and the weight of magnetic adsorbent used. The variables were optimized using a simplex-lattice design. Different magnetite covered with octyl-phenyl silica adsorbents were synthesized by varying the molar ratio of phenyltrimethylsilane and octyltrimethoxysilane; the solids were evaluated for QN preconcentration. Under optimal conditions, a linear range was obtained from 27 to 1000 μg L(-1) with limits of detection ranging from 9 to 12 μg L(-1) for the seven QNs. The absolute recoveries of the seven QNs at three different spiked levels (40, 150, and 400 μg L(-1) ) ranged from 74% to 98% with a relative standard deviation less than 10% in all cases. The proposed method was applied to analyze 20 whole milk samples of different brands. All samples were positive for the presence of QN residues; in some cases, extract dilution was required. The concentrations found are in the range from 31.1 to 5047.3 μg L(-1) . Marbofloxacin was the most frequently found. The method proposed offers advantages in terms of simplicity, sensitivity, efficiency, cost, and analysis time making it an alternative for the analysis of QNs in whole milk samples.     

Determination of acidic herbicides in surface water by solid-phase extraction followed by capillary zone electrophoresis

A rapid solid-phase extraction-capillary zone electrophoresis (CZE) method for determining 2,4-dichlorophenoxyacetic acid, 4-(2,4-dichlorophenoxy) butyric acid, and 2,4,5-trichlorophenoxyacetic acid in real water samples is described. Factors affecting the recoveries and detection of the targets are investigated. With samples being acidified to pH 2 and salted by sodium sulfate to 2% (w/w), an average recovery of greater than 85% is obtained using ethyl acetate as the eluent on an octadecylsilane-bonded silica cartridge. A running buffer of 5 mM sodium tetraborate in a water-acetonitrile mixture (70:30, v/v) adjusted to pH 9 is employed in the CZE analysis, and the targets can be analyzed within 7 min with good reproducibility and acceptable sensitivity. The method is suitable for detecting herbicide residues of sub-parts-per-billion levels in surface water. A local pond water is analyzed, and the concentrations of 2,4-dichlorophenoxyacetic acid and 4-(2,4-dichlorophenoxy) butyric acid are detected to be 0.27 +/- 0.03 ppb and 0.61 +/- 0.08 ppb, respectively.     

Determination of nitroimidazole antibiotics based on dispersive solid-phase extraction combined with capillary electrophoresis

For a long time, the detection of nitroimidazole antibiotics (NIABs) has been a research focus in environmental analytical chemistry. In this work, a novel technique for the analysis of nitroimidazoles was established based on capillary electrophoresis (CE). UiO-66, synthesized using a solvothermal method, was utilized as an adsorbent in the dispersive solid-phase extraction (DSPE) of five different NIABs. The separation and detection of NIABs in environmental water samples were accomplished using the CE diode array detection method. The optimal extraction conditions were obtained after systematically studying the effects of adsorption time, the amount of extractant, and elution solvent on extraction efficiency. According to the results of the study, the limit of detections of the five NIABs were between 16 and 97 ng/mL, the relative standard deviations were between 0.32% and 0.55%, and the spike recoveries were between 87.43% and 104.8%. This study presents a novel technique for measuring NIABs in complex water samples.     

Determination of sulfonylurea herbicides in soil extracts by solid-phase extraction and capillary zone electrophoresis

Summary Sulfonylurea herbicides in soil extracts were concentrated using off-line solid-phase extraction (SPE), and determined by capillary zone electrophoresis (CZE) and UV detection. The method involves extraction of soils with 0.1 M NaHCO₃ solution and subsequent preconcentration by using C₁₈ cartridges prior to separation of the pesticide using CZE. The results show that a C₁₈ cartridge is suitable for the purification of sulfonylurea herbicides in soil extracts with the recoveries ranging from 65–103%. The separation conditions affecting the resolution and detection sensitivity was systematically investigated. The sulfonylureas were resolved well using 30 mM sodium acetate (NaAc)/acetic acid (HAc)+10% acetonitrile (ACN) buffer at pH 4.80. The calibration plots for the test solutes in the concentration of 0.2–50 mg L⁻¹ were linear with detection limits in the range of 0.05–0.10 mgL⁻¹. The proposed method has been successfully demonstrated for the determination of sulfonylurea herbicides in soil samples.     

Determination of tobacco-specific N-nitrosamines in rabbit serum by capillary zone electrophoresis and capillary electrophoresis-electrospray ionization-mass spectrometry with solid-phase extraction

In this paper, we propose a new strategy for separation and determination of tobacco-specific N-nitrosamines (TSNAs), a group of strong carcinogens found only in tobacco products, by using CZE and CE-MS associated with SPE. Six TSNAs: N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol were simultaneously separated by either of two CZE methods, one of which worked with ammonium formate buffer (pH 2.5) and another with citrate buffer (pH 2.4), as well as a CE-MS method. The CZE conditions including pH and concentration of running buffer, capillary length, applied voltage, and capillary temperature were systematically optimized. For CE-MS method, an optimized sheath liquid consisted of methanol-water was used at a flow rate of 10 muL/min. With SPE procedure, our proposed CE-MS method was successfully applied to determine TSNAs after 15 min metabolism in rabbits. A comparison study between CZE and CE-MS methods for quantitative purposes was carried out, showing that both methods provided similar separation efficiency, selectivity, repeatability, linearity, and recovery. However, CE-MS method was better suited for the analysis of TSNAs in complicated biological samples for its sensitivity and extra information on molecular structure. Having good accordance with our previous work by using LC-MS, the new CE-MS method is expected to be an alternative to the LC-MS method and applied to study the metabolism of TSNAs.     

固相萃取-高效液相色谱法测定浓缩苹果汁中的多菌灵残留量

报道了固相萃取-高效液相色谱法测定浓缩苹果汁中多菌灵残留量的方法.样品经适量水稀释后,C18固相萃取柱提取净化,用V(甲醇)∶V(二氯甲烷)=1∶1淋洗,HPLC法测定.在添加水平为0.10,0.50,2.0 mg/kg时,多菌灵的回收率在92.6%～108.3%之间;RSD＜3% (n=6),检出限为0.02 mg/kg,该方法的测定结果满足农药残留量的检测要求.     

Determination of oxytetracycline and some impurities in plasma by non-aqueous capillary electrophoresis using solid-phase extraction

Summary The potential of a non-aqueous, capillary electrophoresis (NACE) system for separating oxytetracycline from three of its impurities—tetracycline, 4-epioxytetracycline and 4-epitetracycline—using UV detection has been studied. The running buffer was: 25 mM sodium acetate, 1 mM EDTA, methanesulfonic acid, pH 4, dissolved in MeOH-ACN (50∶50,v/v). The method was also used to determine these compounds in pig plasma. A solid-phase extraction (SPE) procedure as a clean-up step has also developed. For this we tested Sep Pak C₁₈, LiChrolut EN and OASIS cartridges. OASIS cartridges were best. Recoveries were 90–100% for all compounds except EOTC which had a recovery of 74%.     

Determination of triazine herbicides in natural waters by solid-phase extraction and non-aqueous capillary zone electrophoresis

Capillary zone electrophoresis (CZE) in an organic medium was used to analyse triazines at sub-ppb concentration levels in natural waters after a preconcentration step using conventional C18 cartridges and new Oasis HLB devices. With both sorbents, satisfactory results were obtained on analysing deionized water. However, on analysing natural waters, both sorbents showed very different types of behaviour. The different variables affecting the elution of both sorbents were studied, resulting in the choice of Oasis HLB as the most suitable for later separation by CZE in non-aqueous medium. Combination of a preconcentration step with electrokinetic injection revealed that capillary electrophoresis with simple UV detection can also be used satisfactorily for the quantification of micropollutants in natural waters. The detection limits obtained varied between 0.01 and 0.05 microg l(-1), depending on the type of matrix analysed. The day-to-day precision varied between 0.9% and 2.3%, expressed as the relative standard deviation.     

Gentamicin assay in human serum by solid-phase extraction and capillary electrophoresis

We describe the development of a capillary electrophoresis method for the determination of gentamicin C1, C1a, C2a, and C2 components in human serum. Using a weak cation-exchanger with 20 mM phosphate buffer, pH 7.4, 200 mM borate buffer, pH 9.0, and ammonia/methanol, solid-phase extraction (SPE) of gentamicin components from the human sera was performed. The extract was derivatized with 1,2-phthalic dicarboxaldehyde/mercaptoacetic acid reagent. The derivatives were separated with a background electrolyte comprising 60 mM 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer at pH 9.5 containing 31.6% m/v methanol, and quantified with UV-light absorption detection at 230 nm. The identity of the gentamicin components was confirmed by mass spectrometry. The SPE recovery of the gentamicin ranged from 78% to 93%. The calibration curves were linear from the concentration limit of quantitation (LOQ) to 30 mg/L for the gentamicin mixture. The LOQ for gentamicin C1 was 0.33 mg/L, for C2a 0.23 mg/L, C2 0.25 mg/L, C1a 0.27 mg/L and the concentration limit of detection (LOD) for C1 was 0.15 mg/L, C2a 0.11 mg/L, C2 0.12 mg/L, C1a 0.13 mg/L. Intra-assay relative standard deviation (RSD) values were for C1 (5%), C1a (7%), C2 (6.5%) and C2a (9%); inter-assay RSD values were for C1 (11%), C1a (13.3%), C2 (15%) and C2a (14%). The Pearson's correlation between capillary electrophoresis and immunoassay revealed a linear relationship between these two techniques with r = 0.9. This method for determination of gentamicin C1, C1a, C2a, and C2 in human serum can thus be used in the entire therapeutic concentrations range of gentamicin.     

Determination of melamine in dairy products by an electrochemiluminescent method combined with solid-phase extraction

An electrochemiluminescence (ECL) enhancement method combined with solid-phase extraction has been developed for the determination of melamine in dairy products. It was found that melamine in a strong base solution is able to enhance the ECL of Ru(bpy)₃²⁺ at glass carbon electrode. The optimum experimental conditions for the determination of trace melamine by ECL, such as scan mode and scan rate of the applied potential, the type of buffer solutions and their pH conditions, were investigated. Under optimized conditions, the enhanced ECL intensity was linearly proportional to the logarithm of melamine concentration in the range of 0.01-1.0 ppb, and the detection limit was 0.003 ppb. The method has been successfully demonstrated to determine melamine in dairy products including liquid milk, yogurt and milk powder samples. The relative standard deviations ranging from 5.3% to 11.2% and the recoveries from 95.2% to 102.4% were acquired by this method. A possible mechanism for the ECL enhancement effect was also proposed.     

Dispersive solid-phase extraction based on butylamide silica for the determination of sulfamethoxazole in milk samples by capillary electrophoresis

A new method based on the combination of dispersive solid-phase extraction and capillary electrophoresis is proposed for the determination of sulfamethoxazole in milk samples. Butylamide silica was synthesized and used as extractant. Factors involved in sample treatment method such as: butylamide silica amount, NaOH concentration in methanol, sample volume, and dispersion time were evaluated using a Taguchi parameter design. Under optimal conditions, average recoveries ranged from 73 to 85% with a limit of detection of 0.05?mg?L^?1 were achieved. The proposed method is a useful technique for cleanup milk samples.     

Rapid determination of cyclamate in foods by solid-phase extraction and capillary electrophoresis

A method for the determination of cyclamate in food was developed using solid-phase extraction (SPE) and capillary electrophoresis (CE) with indirect ultraviolet (UV) detection. A 5-10 g sample in 0.1 mol/L hydrochloric acid was homogenized and made up to a volume of 50 mL with 0.1 mol/L hydrochloric acid. After the sample was centrifuged, 25 mL of supernatant was loaded into an Oasis HLB SPE cartridge. The cartridge was washed with 2 mL of demineralized water followed by 2 mL of 50% aqueous methanol, and cyclamate was eluted with 4.5 mL of 50% aqueous methanol. The eluate was added to a solution of sodium propionate (internal standard) for CE analysis. The cyclamate in the eluate was electrophoresed on a fused-silica capillary using 1 mmol/L hexadecyltrimethylammonium bromide and 10 mmol/L potassium sorbate as a running buffer. Detection and reference wavelengths of cyclamate determined with a UV detector were 300 and 254 nm, respectively. The calibration curves for cyclamate showed good linearity in the range of 2-1000 microg/mL and the limits of detection in beverage, fruit in syrup, jam, pickles and confectionary are sample dependent and ranged from 5-10 microg/g. The recovery of cyclamate added at a level of 200 microg/g to various kinds of foods was 93.3-108.3% and the relative standard deviation was less than 4.9% (n=3). A number of commercial samples were analyzed using the proposed method. Cyclamate was detected in one waume, two pickles, and two sunflower seeds. The quantitative values determined with CE correlated to those from high-performance liquid chromatography (HPLC) (the detected values of cyclamate in a sunflower seed measured by CE and HPLC were 3.40 g/kg and 3.51 g/kg, respectively). This analytical method for cyclamate using CE is especially suitable for use in the field.     

SPE-HPLC法测定枸杞中阿维菌素B1a残留量

建立了固相萃取前处理净化技术-高效液相色谱(HPLC)法检测枸杞中阿维菌素B1a残留量的方法.样品用乙腈提取,经C18固相萃取柱净化,采用C18柱(250 mm×4.6 mm i.d.,5 μm)分离,以V(甲醇):V(水)=85:15为流动相,在245 nm下进行检测.阿维菌素B1a在0.20～2.00 μg/mL范围呈良好的线性关系(γ=0.9994);该方法检出限(S/N=3)为0.02mg/kg;添加回收率为88.3%～102.5%,相对标准偏差为2.1%～3.8%.     

高效液相色谱法测定奶粉和液态奶中的三聚氰胺

建立了奶粉和液态奶中三聚氰胺的高效液相色谱（HPLC）检测方法。经阳离子交换固相萃取柱净化后的样品采用HPLC测定。优化的色谱条件：C18柱（4.6 mm ×200 mm,5 μm）,流动相为乙腈-0.01 mol/L庚烷磺酸钠（pH 3.3）（体积比为10∶90）,流速为1.0 mL/min,检测波长为236 nm,柱温为40 ℃,进样量为20 μL。方法的线性范围为1~500 mg/L,检出限为0.2 mg/kg （S/N=3）,定量限为1 mg/kg （S/N=15）,回收率为81.4%~83.7%,相对标准偏差为3.3%~8.5%（n=6）。     

Determination of tylosin in feeds by liquid chromatography with solid-phase extraction

A method was developed for the determination of tylosin in feeds. The method involves extraction of tylosin with methanol, concentration under a stream of nitrogen, and cleanup using Phenomenex C18 solid-phase extraction cartridge. Analyte separation and quantitation were achieved by gradient reversed-phase liquid chromatography and UV absorbance at 285 nm with a reference wavelength of 320 nm with column temperature of 45 degrees C. Average spike recoveries for samples prepared at 4 spiking levels (22.7, 181, 907, and 1000 g/ton) were 111.0, 94.9, 96.2, and 98.6%, respectively. The overall method precision at each of the 4 spiking levels was < or = 7.85% relative standard deviation. The limits of detection and quantitation (g/ton) were 2.16 and 7.20 g/ton, respectively.     

毛细管电泳电致化学发光法测定牛奶样中的土霉素残留量

以铕离子(Ⅲ)掺杂类普鲁士蓝(Eu-PB)化学修饰铂电极为工作电极,基于铜(Ⅱ)-土霉素配合物对三联吡啶钌(Ⅱ)电致化学发光强度的增敏作用,建立了用毛细管电泳电致化学发光法测定土霉素的新方法。实验对毛细管电泳分离条件和电化学发光检测条件进行了优化。在最佳实验条件下,电致化学发光峰面积与铜(Ⅱ)-土霉素配合物的浓度在0.138～46.1μg/mL范围内呈良好的线性关系,检出限为57.0ng/mL(3σ)。本法用于牛奶样中土霉素残留量的测定,加标回收率为95.5%(n=5)。     

Determination of nonsteroidal anti-inflammatory drugs in biological fluids by automatic on-line integration of solid-phase extraction and capillary electrophoresis

A new, automatic method for the clean-up, preconcentration, separation, and quantitation of nonsteroidal anti-inflammatory drugs (NSAIDs) in biological samples (human urine and serum) using solid-phase extraction coupled on-line to capillary electrophoresis is proposed. Automatic pretreatment is carried out by using a continuous flow system operating simultaneously with the capillary electrophoresis equipment, to which it is linked via a laboratory-made mechanical arm. This integrated system is controlled by an electronic interface governed via a program developed in GWBasic. Capillary electrophoresis is conducted by using a separation buffer consisting of 20 mM NaHPO4, 20 mM beta-cyclodextrin and 50 mM SDS at pH 9.0, an applied potential of 20 kV and a temperature of 20 degrees C. The analysis time is 10 min and the detection limits were between 0.88 and 1.71 microg mL(-1). Automatic clean-up and preconcentration is accomplished by using a C-18 minicolumn and 75% methanol as eluent. The limit of detection of NSAIDs can be up to 400-fold improved when using sample clean-up. The extraction efficiency for these compounds is between 71.1 and 109.7 microg mL(-1) (RSD 2.0-7.7%) for urine samples and from 77.2 to 107.1 microg mL(-1) (RSD 3.5-7.1%) for serum samples.