Extraction of parabens by melamine sponge with determination by high-performance liquid chromatography

In the present study, we propose a novel method for the extraction of parabens in personal care products. A new, simple adsorptive material was obtained by combining metal-organic frameworks and melamine sponges using the adhesive property of polyvinylidene fluoride. This new material, metal-organic frameworks/melamine sponges, was found to be particularly suitable for solid-phase extraction. The structural characteristics of metal-organic frameworks/melamine sponges were first analyzed by scanning electron microscopy. Subsequently, solid-phase extraction was performed on sample solutions, and the extracted substances were then analyzed by high-performance liquid chromatography. Following optimization of important experimental conditions, excellent recovery rates were obtained. Our novel method was then applied to the extraction of four parabens (methylparahydroxybenzoates, ethylparahydroxybenzoates, propylparahydroxybenzoates, and butylparahydroxybenzoates) from real samples. The results yielded limits of detection of 0.26–0.41 ng/mL. The inter- and intra-day recoveries were 104.0–109.7% and 91.2–98.1%, respectively (relative standard deviation, <13.8%).     

鸡蛋中三聚氰胺的液相色谱快速测定

建立了鸡蛋中三聚氰胺的液相色谱快速检测方法。样品经1%三氯乙酸溶液超声提取,磺基水杨酸和乙腈沉淀蛋白,高速离心分离,上清液过滤后直接由高效液相色谱分析。在优化的条件下,样品的色谱分析时间仅为10 min;三聚氰胺标准品在0.05～20 mg/L范围内,线性相关系数为0.9999;方法定量限为0.10 mg/kg (S/N＞10);1.0,2.0,4.0,6.0 mg/kg 4个加标水平测试,回收率在94.2%～107%之间;6次平行测试的相对标准偏差(RSD)为1.53%～2.06%。该方法前处理简单、分析速度快、灵敏度高,满足鸡蛋中三聚氰胺检验工作的快速测定要求。     

反相高效液相色谱法同时分析三聚氰酸和三聚氰胺

建立了同时分析三聚氰酸和三聚氰胺的反相高效液相色谱法．发现三聚氰酸和三聚氰胺在C8柱上的保留比在C18柱上明显要强,这一结果表明三聚氰酸和三聚氰胺在反相固定相中的保留并非以通常的疏水分配作用为主导．方法的紫外检测下限为0．034～0．31mg／L,标准曲线线性范围为0．5-100mg／L．方法不经特殊的样品前处理即可用于奶粉和游泳池水等样品中三聚氰酸和三聚氰胺的同时分析．     

Simultaneous determination of cytosine arabinoside, its nucleotides and metabolites by ion-pair high-performance liquid chromatography

Currently available high-performance liquid chromatographic assays for cytosine arabinoside (ara-C) and its metabolites suffer from two major shortcomings: inability to resolve both ara-C and its nucleotides in a single chromatographic step and/or inadequate sensitivity to allow quantitation of intracellular cytosine arabinofuranoside-5'-triphosphate (ara-CTP) without the use of radiolabelled drug. In this paper, we describe a new ion-pairing high-performance liquid chromatographic assay for ara-C in biological samples that can separate ara-C from its nucleotides, metabolites, and naturally occurring ribonucleotides in a single chromatographic step with a lower limit of quantitation of 5 pmol for ara-C and 10 pmol for ara-CTP. Examples of the utility of this assay are shown in studies of intracellular pharmacokinetics of ara-C in cultured human breast cancer cells and in analysis of plasma nucleoside levels in patients receiving high-dose thymidine chemotherapy. We conclude that this assay provides a rapid and versatile system that can be applied to the study of both cellular and plasma nucleoside pharmacokinetics.     

气相色谱-质谱法测定鸡肉中残留的环丙胺嗪及其代谢物三聚氰胺

建立了鸡肉中残留的环丙胺嗪及其代谢物三聚氰胺的气相色谱-质谱(GC-MS)检测方法。样品经酸化的乙腈-水溶液提取、二氯甲烷去脂、混合型的阳离子交换(MCX)固相萃取柱净化、N,O-双三甲基硅基-三氟乙酰胺(BSTFA)衍生化后进行GC-MS测定。环丙胺嗪采用外标法定量,三聚氰胺以三聚氰胺-15N3为内标定量。结果表明,环丙胺嗪与三聚氰胺的线性范围均为100～1000 μg/L,定量限为20 μg/kg。在20,40,80 μg/kg 3个添加浓度下目标化合物的平均回收率为75%～110%,批内、批间相对标准偏差分别小于10%和15%。该方法样品前处理简单,测定灵敏度高,定性准确,选择性好,可实现鸡肉中环丙胺嗪与三聚氰胺残留的同时测定。     

Simultaneous determination of nitrite and nitrate in dew, rain, snow and lake water samples by ion-pair high-performance liquid chromatography

A simple, fast, sensitive and accurate reversed-phase ion-pair HPLC method for simultaneous determination of nitrite and nitrate in atmospheric liquids and lake waters has been developed. Separations were accomplished in less than 10 min using a reversed-phase C₁₈ column (150 mm × 2.00 mm i.d., 5 μm particle size) with a mobile phase containing 83% 3.0 mM ion-interaction reagent tetrabutylammonium hydroxide (TBA-OH) and 2.0 mM sodium phosphate buffer at pH 3.9 and 17% acetonitrile (flow rate, 0.4 mL/min). UV light absorption responses at 205 nm were linear over a wide concentration range from 100 μg/mL to the detection limits of 10 μg/L for nitrite and 5 μg/L nitrate. Quantitation was carried out by the peak area method. The relative standard deviation for the analysis of nitrite and nitrate was less than 3.0%. This method was applied for the simultaneous determination of nitrite and nitrate in dew, rain, snow and lake water samples collected in southeast Massachusetts. Nitrate was found being present at 4.79-5.99 μg/mL in dew, 1.20-2.63 μg/mL in rain, 0.32-0.60 μg/mL in snow and 0.12-0.23 μg/mL in lake water. Nitrite was only a minor species in dew (0.62-0.83 μg/mL), rain (<0.005-0.14 μg/mL), snow (0.021-0.032 μg/mL) and lake water (0.12-0.16 μg/mL). High levels of nitrite and nitrate observed in dew water droplets may constitute an important source of hydroxyl radicals in the sunny early morning.     

Separation of arsenic species by ion-pair and ion exchange high performance liquid chromatography

Arsenite, arsenate, monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine and the tetramethylarsonium ion were subjected to ion-exchange and ion-pair reversed phase HPLC. The ion exchange method was superior in selectivity and time of analysis for the arsenic anions. The ammonium ions used for the ion-pair method only resulted in separation of some of the anionic arsenic compounds. Flame atomic absorption spectrometry was used for on-line arsenic-specific detection.     

Residue determination of cyromazine and its metabolite melamine in chard samples by ion-pair liquid chromatography coupled to electrospray tandem mass spectrometry

A method has been developed for the sensitive and selective determination of cyromazine and its metabolite melamine in chard samples. Both compounds are small polar basic molecules, making their determination at residue levels complicated. The method involves an extraction procedure with phosphate buffer and methanol using high-speed blender, the addition of tridecafluoroheptanoic acid (TFHA) as ion-pair reagent and the injection of the five-fold diluted extract on liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI–MS/MS). The method has been validated for chard samples, spiked at 0.05 and 0.5 mg kg⁻¹. Quantification was carried out by using matrix-matched standards calibration and recoveries were satisfactory, with mean values for cyromazine of 103% and 93%, and relative standard deviations lower than 7%. In the case of melamine, recoveries were 89% and 86%, with relative standard deviations lower than 13%. A limit of quantification of 0.05 mg kg⁻¹ was obtained for both compounds, with the limit of detection below 0.01 mg kg⁻¹. The method, with very little sample handling and good sensitivity, was applied to the rapid determination of low residue levels of these compounds in chards from field residue trials. All the quality controls included during the analysis were satisfactory with average recoveries of 92% and 78% for cyromazine and melamine, respectively.     

Advances on melamine determination by micellar liquid chromatography: A review

Melamine is a toxic triazine which has been recently proven as a threat to human health. It can be ingested by several methods, being the most important the unethical adulteration of protein-rich foodstuff for economic reasons. This review presents several analytical methods, taken from the literature studies, devoted to the determination of melamine in milk, dietetic supplements, drinking and wastewater, swine kidney, plasma, and urine, using micellar liquid chromatography (MLC). We consider that the control of these samples is crucial to prevent and manage melamine intoxication. This technique has been demonstrated as an excellent tool to determine organic compounds in these matrices. We detail the optimization strategy and the obtained results in the different steps of method development, such as sample pretreatment, chromatographic separation, and validation process. The similarities and differences of the procedures have been described and discussed, as well as their advantages. The main ones were the possibility of direct injection and the efficient chromatographic elution, in spite of the complexity of the samples. Besides, it was found that the MLC procedures were fast, easy-to-handle, inexpensive, eco-friendly, safe, and useful for routine analysis. Therefore, they represent an excellent alternative to reliably evaluate the melamine concentration in that kind of samples.     

Simultaneous determination of lamotrigine, zonisamide, and carbamazepine in human plasma by high-performance liquid chromatography

A high-performance liquid chromatography assay with ultraviolet detection was developed for the simultaneous determination of the anti-epileptic drugs lamotrigine, carbamazepine and zonisamide in human plasma and serum. Lamotrigine, carbamazepine, zonisamide and the internal standard chloramphenicol were extracted from serum or plasma using liquid-liquid extraction under alkaline conditions into an organic solvent. The method was linear in the range 1-30 microg/mL for lamotrigine, 2-20 microg/mL for carbamazepine, and 1-40 microg/mL for zonisamide. Within- and between-run precision studies demonstrated coefficient of variation <10% at all tested concentrations. Other anti-epileptic medications tested did not interfere with the assay. The method is appropriate for determining lamotrigine, carbamazepine and zonisamide serum or plasma concentrations for therapeutic monitoring.     

Simultaneous determination of myocardial nucleotides, nucleosides, purine bases and creatine phosphate by ion-pair high-performance liquid chromatography.

An ion-pair reversed-phase high-performance liquid chromatographic method is described for the separation and quantification of myocardial nucleotides, nucleosides, their metabolites and creatine phosphate-related compounds in a single run. Separation of a standard mixture containing 21 compounds was achieved on a 5-microns Hypersil ODS column with a 5-min isocratic elution (buffer: 0.1 M NaH2PO4, pH 5.5, containing 5.9 mM tetrabutylammonium hydrogen-sulphate) followed by a slow linear gradient to 17% acetonitrile. The method was applied to extracts of freeze-clamped rat heart tissue samples as well as to extracts of neonatal rat heart cardiomyocytes, and it provided good resolution of high-energy phosphates, including creatine phosphate, as well as of their degradation products.     

Simultaneous determination of rifampicin and sulbactam in mouse plasma by high-performance liquid chromatography

A simple and rapid high-performance liquid chromatographic (HPLC) method with ultraviolet detection has been developed and validated for the simultaneous determination of rifampicin and sulbactam in mouse plasma. Plasma samples were deproteinized with acetonitrile and separated by HPLC on a RP-18 (125 x 4 mm, 5 microm) column and gradient elution with potassium dihydrogen phosphate solution (pH 4.5; 50 mm) and acetonitrile at a flow-rate of 1.0 mL/min. Rifampicin and sulbactam were monitored at 230 nm and confirmed by means of their UV spectra using a diode-array detector. The method was linear at plasma levels from 1 to 100 microg/mL for rifampicin and from 5 to 200 microg/mL for sulbactam. The limits of quantification were 0.6 microg/mL for rifampicin and 4.2 microg/mL for sulbactam. The intra- and inter-day precisions of the method (RSD) were lower than 5% for both compounds. Average recoveries of rifampicin and sulbactam from mice plasma were 98.2 and 89.3%, respectively. The developed method was successfully applied to the determination of the pharmacokinetic profile of both compounds in mice.     

Automated analysis of fluvoxamine in rat plasma using a column-switching system and ion-pair high-performance liquid chromatography

We have established a robust, fully automated analytical method for the analysis of fluvoxamine in rat plasma using a column-switching ion-pair high-performance chromatography system. The plasma sample was injected onto a precolumn packed with Shim-pack MAYI-ODS (50 microm), where the drug was automatically purified and enriched by on-line solid-phase extraction. After elution of the plasma proteins, the analyte was back-flushed from the precolumn and then separated isocratically on a reversed-phase C18 column (L-column ODS) with a mobile phase (acetonitrile-0.1% phosphoric acid, 36:64, v/v) containing 2 mM sodium 1-octanesulfonate. The analyte was monitored by a UV detector at a wavelength of 254 nm. The calibration line for fluvoxamine showed good linearity in the range of 5-5000 ng/mL (r > 0.999) with the limit of quantification of 5 ng/mL (RSD = 6.51%). Accuracy ranged from -2.94 to 4.82%, and the within- and between-day precision of the assay was better than 8% across the calibration range. The analytical sensitivity and accuracy of this assay is suitable for characterization of the pharmacokinetics of orally-administered fluvoxamine in rats.     

SPE-LC-MS联用同时测定环境水样中痕量三聚氰胺和灭蝇胺

建立了一种同时测定环境水样中痕量三聚氰胺和灭蝇胺的固相萃取-高效液相色谱-质谱联用(SPE-LC-MS)分析方法。水样经PCX柱固相萃取,以CN柱为分析柱,V(甲醇)∶V(水)=30∶70为流动相,采用电喷雾正离子模式全扫描,三聚氰胺、灭蝇胺的定量离子分别为m/z127,m/z167,获得的最低检出限分别为0.05,0.08μg/L,对不同来源的实际水样加标回收率为85.2%～104.2%,相对标准偏差为1.5%～5.1%。应用该方法测定了湖水、河水、江水等不同基质实际水样。     

气相色谱-质谱联用法同时测定乳及乳制品中的三聚氰胺及肌酐

建立了同时测定乳制品中三聚氰胺及肌酐的气相色谱-质谱联用方法。样品经1%三氯乙酸溶液萃取,混合型阳离子交换固相萃取净化,提取液用氮气吹干后加入N,O-双(三甲基硅基)三氟乙酰胺-三甲基氯硅烷(BSTFA-TMCS)硅烷化试剂,于75 ℃下衍生60 min,最后采用选择离子模式下的气相色谱-质谱测定。三聚氰胺和肌酐的定量限分别为0.10 mg/kg和0.20 mg/kg;在0.1～50 mg/L范围内的线性相关系数均大于0.99。实际样品中,肌酐在10～100 mg/kg和三聚氰胺在0.1～5.0 mg/kg添加范围内的回收率分别为80.7%～116.8%和77.6%～107.5%,相对标准偏差分别小于9.4%和8.5%。该方法能有效除去干扰,灵敏度高,回收率较好,可用于乳制品中三聚氰胺和肌酐的同时测定。     

Simultaneous determination of nitrite and nitrate by normal phase ion-pair liquid chromatography

Normal phase ion-pair high performance liquid chromatography has been used for simultaneous separation of nitrite and nitrate using tetraethylammonium (TEA)(+) as ion-pairing reagent. The concentration effect of (TEA)(+), buffer salt and pH of the eluent on separation is investigated. The UV detector response at various wavelengths has been optimized. The performance of the proposed method is compared with ion chromatography for quantification of the anions in potable water, wastewater and in food samples, such as spinach and lettuce.     

Simultaneous determination of oxycodone and its major metabolite, noroxycodone, in human plasma by high-performance liquid chromatography

Oxycodone (14-hydroxy-7,8-dihydrocodeinone) is a potent opioid receptor agonist. In the present study, a liquid-liquid extraction-based reversed-phase HPLC method with UV detection was validated and applied for the analysis of oxycodone and its major metabolite, noroxycodone, in human plasma. The analytes were separated using a mobile phase, consisting of acetonitrile and phosphate buffer (8:92, v/v) at a flow rate of 1 mL/min, and UV detection at 205 nm. The retention times for oxycodone, noroxycodone and codein (internal standard) were 14.7, 13.8 and 10.2 min, respectively. The validated quantitation range of the method was 2-100 ng/mL for oxycodone and 10-100 ng/mL for noroxycodone. The developed procedure was applied to assess the pharmacokinetics of oxycodone and its metabolite following administration of a single 20 mg oral dose of oxycodone hydrochloride to one healthy male volunteer.     

Simultaneous quantitative determination of resorcinol and 1-Naphthol in haircolor products by high-performance liquid chromatography

Summary A high-performance liquid chromatographic method has been developed for the simultaneous quantitative determination of resorcinol and 1-naphthol in hair tonic and haircolor products. The two compounds could be separated on a μBondapak C₁₈ column by elution with 50∶50 (v/v) methanol-water as mobile phase. The retention times of resorcinol and 1-naphthol were 2.5 and 7.0 min, respectively. Seven dye intermediates could be analyzed within 12 min without any interference with the peaks of resorcinol and 1-naphthol from other cosmetic ingredients present in the haircolor liquid or cream. The results obtained were in good agreement with those obtained by a spectrophotometric method.