Determination of alternariol in tomato paste using solid phase extraction and high-performance liquid chromatography with fluorescence detection.

Alternaria spp. produce a wide variety of toxic metabolites with different chemical structures. Tomato products have been considered a likely source of Alternaria toxins in the human diet because Alternaria is an important spoilage mold of tomatoes. A new method for the determination of these mycotoxins in tomato paste, involving solid phase cartridges for extraction before HPLC fluorescence detection with a reversed phase column and isocratic elution, was developed. The method was demonstrated to be linear in the range 5.2-196 ppb of alternariol (AOH) in tomato paste. Good recoveries were obtained for AOH at all levels assayed (minimum 77.2%). The detection limit of the AOH toxin in real samples of tomato paste was low, 1.93 ppb. The precision of the method was demonstrated with a good repeatability (RSD = 2.98%) and reproducibility (RSD = 9.35%).     

Determination of chloroethenes in environmental biological samples using gas chromatography coupled with solid phase micro extraction

Summary An analytical method has been developed to determine the chloroethene series, tetrachloroethene (PCE), trichloroethene (TCE),cisdichloroethene (cis-DCE) andtransdichloroethene (trans-DCE) in environmental biotreatment studies using gas chromatography coupled with a solid phase micro extraction (SPME) technique. The volatile chlorinated compounds in aqueous solution can be analyzed directly without solvent extraction, purge and trap, or thermal heating. The calibration curves have demonstrated good linear relationships within 50.0 to 3000.0 g L^–1 concentration range. Detection limits are 18.0, 5.0, 25.0, and 42.0 g L^–1, for PCE, TCE,cis-DCE andtrans-DCE, respectively. Factors which affect the SPME process, such as sample adsorption time, thermal desorption time, and concentration of salt in the matrix, have also been evaluated.     

Determination of benzimidazole fungicides in soil samples using microwave-assisted micellar extraction and liquid chromatography with fluorescence detection

A simple and fast analytical method was developed for the determination of benzimidazole fungicides (benomyl, carbendazim, thiabendazole, and fuberidazole) in soil samples. The analytes were extracted from the soil samples by means of conventional microwave-assisted extraction, using the non-ionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monooalkyl ether (Genapol X-080) as extractants. Determinations were made by using liquid chromatography with direct fluorescence detection. The use of an analytical column Symmetry C-18 offered short retention times of analytes without the need of any pH regulators with mobile phase methanol-water (50 + 50, v/v). The best results were obtained using 5% (v/v) POLE as extractant with recoveries of the fungicides in spiked soil samples between 71 and 105%. The results were compared with those obtained when Soxhlet extraction was applied to the same soil samples.     

Hollow fiber-based liquid phase microextraction combined with high-performance liquid chromatography for the analysis of gabapentin in biological samples

Three-phase hollow fiber microextraction technique combined with high performance liquid chromatography-ultra violet (HPLC-UV) was applied for the extraction and determination of gabapentin in biological fluids. Gabapentin (GBP) was derivatized with 1-fluoro-2,4-dinitrobenzene, as a UV absorbent agent in borate buffer (pH 8.2) before extraction. The derivative product of GBP was extracted from the 8.5 mL of acidic solution (source phase) into an organic phase (dihexyl ether) impregnated in the pores of a hollow fiber and finally back-extracted into 24 μL of the basic solution (pH 9.1) located inside the lumen of the hollow fiber (receiving phase). The extraction took place due to pH gradient between the inside and outside of the hollow fiber membrane. In order to achieve maximum extraction efficiency, different parameters affecting the extraction conditions were optimized. Under the optimized conditions, preconcentration factor of 95 and detection limit (LOD) of 0.2 μg L⁻¹ were obtained. The calibration graph was linear within the range of 0.6-5000 μg L⁻¹. Finally, the feasibility of the proposed method was successfully confirmed by extraction and determination of GBP in human urine and plasma samples in the range of microgram per liter and suitable results were obtained (RSDs < 6.3%).     

Determination of 90Sr in environmental samples using solid phase extraction chromatography

The p-tert-butyl calix[4]arene thiophenol derivative was successfully synthesized with reflux condition and was characterized by FT-IR and ¹H-NMR. This work mainly adopted the method of controlling variables. The results showed that the optimum pH value, temperature and extraction time were respectively 4.5, 25 °C and 90 min. By calculating the data of the enthalpy change and gibbs free energy, indicating that the process of reaction was an exothermic and spontaneous process, and it demonstrated a close agreement with pseudo-second-order kinetic model. It is also found that the coexisting cations on the extraction of uranium had greater influence.

     

Determination of phenols in water using liquid phase microextraction with back extraction combined with high-performance liquid chromatography.

Liquid phase microextraction with back extraction (LPME/BE) combined with high-performance liquid chromatography (HPLC) was studied for the determination of a variety of phenols in water samples. The target compounds were extracted from 2-ml aqueous sample adjusted to pH 1 (donor solution) through a microliter-size organic solvent phase (400-microl n-hexane), confined inside a small PTFE ring, and finally into a 1-microl basic aqueous acceptor microdrop suspended inthe aforementioned solvent phase from the tip of a microsyringe needle. After extracting for a prescribed time, the microdrop was taken back into the syringe and directly injected into an HPLC for detection. Factors relevant to the extraction procedure were studied. At the optimized extraction conditions, a large enrichment factor (more than 100-fold) can be achieved for most of the phenols within 35 min. The detection limit range was 0.5-2.5 microg/l for different analytes in aqueous samples. The results demonstrate the suitability of the LPME/BE approach to the analysis of polar compounds in aqueous samples.     

Determination of ochratoxin A in wine using liquid-phase microextraction combined with liquid chromatography with fluorescence detection

A liquid-liquid microextraction technique (LPME) has been applied to the extraction of ochratoxin A (OTA) from wine prior to its quantification by HPLC-fluorescence detection. OTA was extracted from wine, through 1-octanol immobilized in the pores of a porous hollow fiber, and introduced into 1-octanol inside the fiber. Recovery was 77%. The method was adequate for quantification of OTA in wine at levels within the range 0.25-10 ng/ml with a LOD of 0.2 ng/ml, and can be a simple and inexpensive alternative to the use of inmunoaffinity columns in order to quantify OTA levels in wine.     

Determination of fluoroquinolones in edible animal tissue samples by high performance liquid chromatography after solid phase extraction

In the present work, a rapid, accurate, and sensitive method has been developed for the quantitative determination of five fluoroquinolones (enoxacin, ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin) in edible animal tissues (muscle tissue, liver, kidney, and eggs). The separation was accomplished on an Inertsil (250 x 4 mm) C8, 5 microm, analytical column, at ambient temperature within 15 min. The mobile phase consisted of a mixture of citric acid (0.4 mol L(-1))-CH3OH-CH3CN (87:9:4% v/v). UV detection at 275 nm yielded the following limits of detection: 100 pg per 20 microL injected volume for enoxacin, norfloxacin, and ciprofloxacin, 20 pg for ofloxacin, and 200 pg for enrofloxacin. Peaks in real samples were identified by means of a photodiode array detector. The method was validated in terms of intra-day (n = 8) and inter-day (n = 8) precision and accuracy. Tissue samples were purified from endogenous interference by solid-phase extraction using Oasis HLB cartridges. The solid-phase extraction protocol was optimized in terms of retention and elution. Recovery rates at fortification levels of 40, 60, and 80 ng/g ranged from 82.5% to 111.1%. The applicability of the method was examined using real samples from a chicken treated orally with the five studied fluoroquinolones.     

分子印迹固相萃取-高效液相色谱法测定猪肉中红霉素残留

采用沉淀聚合法,以红霉素（erythromycin,ERY）为模板,甲基丙烯酸（methacrylic acid,MAA）为功能单体,乙二醇二甲基丙烯酸酯（ethyleneglycoldimethacrylate,EGDMA）为交联剂,甲醇/乙腈（1:4,v/v）为致孔剂制备了ERY分子印迹聚合物（molecularly imprinted polymers,MIPs）。通过扫描电镜、平衡吸附实验等对制备的印迹和非印迹聚合物进行表征和测定,结果表明所制备的MIPs对ERY具有特异性吸附作用。Scatchard分析证明MIPs对ERY的吸附存在两类不同结合位点,最大表观结合量（Q_max）和平衡解离常数（K_d）分别为Q_max1=45.24 mg/g,K_d1=0.028 g/L; Q_max2=87.53 mg/g,K_d2=0.20 g/L。以制备的MIPs为吸附剂的分子印迹固相萃取柱,结合高效液相色谱法能够快速检测猪肉样品中的ERY残留,线性范围为0.5~50 mg/L（r²=0.9994）,检出限（S/N=3）为0.2 mg/kg。猪肉样品中不同添加水平下ERY的加标回收率为95.2%~104.2%,相对标准偏差（RSD）小于5%。该方法选择性好,灵敏、可靠,可用于猪肉等复杂食品样本中ERY残留的检测。     

A new interface for coupling solid phase microextraction with liquid chromatography

A modified Rheodyne 7520 microsample injector was used as a new solid phase microextraction (SPME)–liquid chromatography (LC) interface. The modification was focused on the construction of a new sample rotor, which was built by gluing two sample rotors together. The new sample rotor was further reinforced with 3 pieces of stainless steel tubing. The enlarged central flow passage in the new sample rotor was used as a desorption chamber. SPME fiber desorption occurred in static mode. But all desorption solvent in the desorption chamber was injected into LC system with the interface. The analytical performance of the interface was evaluated by SPME–LC analysis of PAHs in water. At least 90% polycyclic aromatic hydrocarbons (PAHs) were desorbed from a polyacrylonitrile (PAN)/C18 bonded fuse silica fiber in 30 s. And injection was completed in 20 s. About 10–20% total carryovers were found on the fiber and in the interface. The carryover in the interface was eliminated by flushing the desorption chamber with acetonitrile at 1 mL min⁻¹ for 2 min. The repeatability of the method was from 2% to 8%. The limit of detection (LOD) was in the mid pg mL⁻¹ range. The linear ranges were from 0.1 to 100 ng mL⁻¹. The new SPME–LC interface was reliable for coupling SPME with LC for both qualitative and quantitative analysis.     

固相萃取-微乳液相色谱法测定环境水体中的3种酚类化合物

建立了固相萃取-微乳液相色谱法同时测定环境水体中的苯酚、双酚A (BPA)、2,4-二氯苯酚3种酚类化合物的检测方法。水样加酸酸化后,经C18固相萃取小柱富集净化,用微乳液相色谱法测定3种目标物的含量。在Inertsil C18色谱柱(150 mm×4.6 mm, 5 μm)上以微乳(3.0%十二烷基硫酸钠(SDS)-6.0%正丁醇-0.8%正庚烷-90.2%(水+0.5%HAc))和乙腈作为流动相进行梯度洗脱,流速1.0 mL/min,检测波长280 nm。结果表明,苯酚、双酚A、2,4-二氯苯酚的检出限(S/N=3)依次为0.74、8.0、8.0 μg/L,线性范围在0.1~10 mg/L范围内,相关系数(r)均大于0.999。将3种酚类化合物定量加到空白水样中,苯酚、双酚A、2,4-二氯苯酚的加标回收率分别为82.7%、87.8%、82.6%,其RSD均小于5%(n=6)。对环境水样的酚类化合物分析也取得了良好的加标回收率,其值均在85.7%~113.2%之间。结果表明,该方法准确可靠、灵敏度高,适用于环境水体中酚类化合物的检测。     

Determination of fungicides in water using liquid phase microextraction and gas chromatography with electron capture detection

A hollow fiber liquid phase microextraction (HF-LPME) and gas chromatographic-electron capture detection (GC-ECD) method for the determination of six fungicides (chlorothalonil, hexaconazole, penconazole, procymidone, tetraconazole, and vinclozolin) in 3 ml of water was described. The method used 3 μl of toluene as extraction solvent, 20 min extraction time with pH 4, stirring at 870 rpm, and no salt addition. The enrichment factors of this method were from 135 to 213. Limits of detection were in the range of 0.004-0.025 μg/l. The relative standard deviations (RSDs) at 0.1 and 5 μg/l of spiking levels were in the range 3-8%. Recoveries of six fungicides from farm water at a spiking level of 0.5 μg/l were between 90.7 and 97.6%. The method compared favorably with the traditional method in terms of the sample size, analysis time, and cost.     

Simultaneous determination of pharmaceutically active compounds in wastewater samples by solid phase extraction and high-performance liquid chromatography with diode array and fluorescence detectors

In the present work, an analytical method for the simultaneous determination of five anti-inflammatory drugs (acetaminophen, diclofenac, ibuprofen, ketoprofen and naproxen), an antiepileptic drug (carbamazepine) and a nervous stimulant (caffeine) is proposed for the routine analysis of these pharmaceuticals in wastewater influents and effluents from WWTPs. The method involves pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction cartridges. Final analysis of the selected pharmaceutical compounds was carried out by high-performance liquid chromatography (HPLC) with diode array detector (DAD). Confirmation of the presence of the fluorescence compounds (ibuprofen and naproxen) was performed by on-line fluorescence detection. Recoveries were ranged from 71 to 103% with relative standard deviation below 15.1%. Limits of quantification were in the range 6.2–319.8 and 3.0–160.0 ng ml⁻¹ for influent and effluent wastewater samples, respectively. The described method was applied to the determination of the drugs in wastewater samples from four treatment plants in Seville.     

Analysis of non-anthocyanin phenolic compounds in wine samples using high performance liquid chromatography with ultraviolet and fluorescence detection

A simple and rapid HPLC method with UV and fluorescence detection (FLD) for the separation of ten phenolic compounds including gallic acid, catechin, epicatechin, caffeic acid, coumaric, trans-piceid, cis-piceid, trans-resveratrol, cis-resveratrol and quercetin is reported. The UV and fluorescence detector in series provided a high selectivity for the determination of these compounds. Precisions, recoveries and LODs achieved for all the analytes were satisfactory. The proposed method was applied to the determination of these compounds in commercially available red wines.     

Improved method for the determination of anatoxin-a and two of its metabolites in blue-green algae using liquid chromatography with fluorescence detection

Anatoxin-a, a neurotoxin produced by blue-green algae (BGA) species, can cause death to exposed organisms. In North America, BGA are harvested and sold as food supplements, some of which contain elevated levels of other algal toxins, such as microcystins. Concern that elevated levels of anatoxin-a also may be present in BGA food supplements has led to the development of a simple method to determine the presence of anatoxin-a in BGA. Some researchers have successfully analyzed this compound using liquid chromatography with fluorescence detection by forming a fluorescent derivative with 4-fluoro-7-nitrobenzofurazan (NBD-F) in water and phytoplankton extracts. With this method, the background noise is high in BGA extracts due to the presence of co-extractives. Addition of o-phthaldialdehyde (OPA) and mercaptoethanol to the extract before addition of the NBD-F resulted in the successful removal of primary amines from the background noise when the NBD-F derivatives were detected with fluorescence. Improved chromatograms were obtained when extracts were cleaned up in this manner, leading to a lower detection limit (approximately 50 microg/kg) for anatoxin-a. The detection limits obtained for the 2 degradation products dihydroanatoxin-a and epoxyanatoxin-a in BGA extracts were similarly low (55 and 65 microg/kg, respectively).     

Determination of atrazine in environmental and biological samples using solid phase extraction and spectrophotometry

An analytical method employing a combination of solid phase extraction and spectrophotometry is proposed for the determination of a widely used herbicide atrazine. This combination is very simple and cheaper than chromatography and mass spectrometry based methods. The proposed method also reduced the use of toxic solvents. The method is based on the reaction of atrazine with pyridine to form a quaternary halide, which forms a carbinol base in the presence of alkali. Carbinol undergoes cleavage of heterocyclic ring to form glutaconic aldehyde that is subsequently coupled with sulphanilic acid to give a yellow orange dye which is measured spectrophotometrically at 460 nm. Beer’s law is obeyed in the range 0.07–0.7 μg/mL of atrazine. Molar absorptivity and Sandell’s sensitivity were found to be 2.2 × 10⁵ L/mol cm and 0.0009 μg/cm², respectively. Breakthrough volume is found to be more than 100 mL. The use of solid phase extraction increases the sensitivity ten times. The proposed method is sensitive and found to be free from the interference of a large number of foreign species and other pesticides. The developed method was applied to spiked environmental and biological samples, the recovery was in the range from 95.2 to 99.2% with RSD of 0.36%. The article is published in the original.     

Determination of eight fluoroquinolones in groundwater samples with ultrasound-assisted ionic liquid dispersive liquid–liquid microextraction prior to high-performance liquid chromatography and fluorescence detection

An ultrasound-assisted ionic liquid dispersive liquid–liquid microextraction (US-IL-DLLME) procedure was developed for the extraction of eight fluoroquinolones (marbofloxacin, norfloxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, oxolinic acid and nalidixic acid) in groundwater, using high-performance liquid chromatography with fluorescence detection (HPLC-FD). The ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution using a small volume of disperser solvent (0.4 mL of methanol), which increased the extraction efficiency and reduced the equilibrium time.     

Determination of camptothecin in biological fluids using reversed-phase high-performance liquid chromatography with fluorescence detection

Camptothecin, a plant alkaloid with antitumor activity, is a potent and rapidly acting inhibitor of DNA synthesis. The objective of this study was to develop a sensitive high-performance liquid chromatographic (HPLC) method for the detection and estimation of the camptothecin concentration in biological fluids. Using HPLC coupled with fluorescence detection, at an excitation wavelength of 370 nm and an emission wavelength of 434 nm, we found that the lower limits of detection for camptothecin in aqueous, plasma and urine samples were 0.5, 1 and 10 ng/ml, respectively. The ideal mobile phase used was methanol-10 mM potassium phosphate (75:25, v/v, pH 4.0). To determine the utilization of the method in a biological system, we studied the pharmacokinetics of camptothecin in mice. Elimination of camptothecin from mice blood was triphasic and followed first-order kinetics. The half-life of camptothecin in mouse blood was 25.7 min. Our studies indicate that HPLC with fluorescence detection for the determination of camptothecin in different media is a simple, rapid, sensitive and reproducible method.     

Hollow fiber-based liquid phase microextraction combined with high-performance liquid chromatography for extraction and determination of some antidepressant drugs in biological fluids

The applicability of hollow fiber-based liquid phase microextraction (HF-LPME) was evaluated for the extraction and preconcentration of three antidepressant drugs (amitriptyline, imipramine and sertraline) prior to their determination by HPLC-UV. The target drugs were extracted from 11.0 mL of aqueous solution with pH 12.0 (source phase) into an organic extracting solvent (n-dodecane) impregnated in the pores of a hollow fiber and finally back extracted into 24 μL of aqueous solution located inside the lumen of the hollow fiber and adjusted to pH 2.1 using 0.1 M of H₃PO₄ (receiving phase). The extraction was performed due to pH gradient between the inside and outside of the hollow fiber membrane. In order to obtain high extraction efficiency, the parameters affecting the HF-LPME including pH of the source and receiving phases, the type of organic phase, ionic strength and volume of the source phase, stirring rate and extraction time were studied and optimized. Under the optimized conditions, enrichment factors up to 300 were achieved and the relative standard deviation (R.S.D.%) of the method was in the range of 2-12%. The calibration curves were obtained in the range of 5-500 μg L⁻¹ with reasonable linearity (R² > 0.998) and the limits of detection (LODs) ranged between 0.5 and 0.7 μg L⁻¹ (based on S/N = 3). Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in urine, plasma and tap water samples. The results indicated that hollow fiber microextraction method has excellent clean-up and high-preconcentration factor and can be served as a simple and sensitive method for monitoring of antidepressant drugs in the biological samples.     

High performance liquid chromatography analysis of MESNA (2-mercaptoethane sulfonate) in biological samples using fluorescence detection

MESNA is the sodium salt of 2-mercaptoethane sulfonate, a thiol-containing drug. It is an antioxidant used particularly in renal protection. Several studies have proved that MESNA has beneficial effects in ischemic acute renal failure where it scavenges reactive oxygen species (ROS), due to the presence of the thiol group. It also reduces the size of urinary bladder cancer. MESNA was proved to be effective in preventing hemorrhagic cystitis induced by high doses of several chemotherapeutic regimens such as cyclophosphamide and ifosfamide. It has been shown that MESNA functions as an uroprotective substance in drug-induced experimental bladder cancer models. Moreover, recent studies have suggested that it is also effective in reducing intestinal inflammation in colitis. Because of the increased level of interest in using MESNA for treating various disorders, a new and sensitive method was needed to understand the pharmacokinetics of this drug. Accordingly, we developed a new method for determining free MESNA in biological samples by using ThioGlo-3 [3H-Naphto [2,1-b] pyran, 9-acetoxy-2-(4-(2,5-dihydro-2, 5-dioxo-1H-pyrrol-1-yl) phenyl-3-oxo)] as the derivatizing agent. MESNA was detected fluorimetrically by reverse-phase HPLC using acetonitrile:water (75:25) along with acetic acid and phosphoric acid (1 mL/L each) as the mobile phase. The detection limit was 1.64 nm per 20 microL injection volume, with a linearity (r = 0.999) in the calibration curve extending over a range 2.5-2500 nm. The coefficients of variation for within-run and between-run precision were 0.43 and 3.31%, respectively. The relative recoveries in the biological samples were in the range 87 +/- 6 to 93 +/- 2.4%. The concentrations of MESNA in the biological samples (lungs, liver, kidney and brain) were determined. The highest concentration of MESNA was found in plasma. Of all the tissues, the kidney was found to have the highest concentration while the liver had the lowest concentration.