Determination of volatile nitrosamines in meat products by microwave-assisted extraction and dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry

Microwave-assisted extraction (MAE) and dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) were evaluated for use in the extraction and preconcentration of volatile nitrosamines in meat products. Parameters affecting MAE, such as the extraction solvent used, and DLLME, including the nature and volume of the extracting and disperser solvents, extraction time, salt addition and centrifugation time, were optimized. In the MAE method, 0.25g of sample mass was extracted in 10mL NaOH (0.05M) in a closed-vessel system. For DLLME, 1.5mL of methanol (disperser solvent) containing 20μL of carbon tetrachloride (extraction solvent) was rapidly injected by syringe into 5mL of the sample extract solution (previously adjusted to pH 6), thereby forming a cloudy solution. Phase separation was performed by centrifugation, and a volume of 3μL of the sedimented phase was analyzed by GC-MS. The enrichment factors provided by DLLME varied from 220 to 342 for N-nitrosodiethylamine and N-nitrosopiperidine, respectively. The matrix effect was evaluated for different samples, and it was concluded that sample quantification can be carried out by aqueous calibration. Under the optimized conditions, detection limits ranged from 0.003 to 0.014ngmL(-1) for NPIP and NMEA, respectively (0.12-0.56ngg(-1) in the meat products).     

Development of Dispersive Liquid‐Liquid Microextraction Based on Solidification of Floating Organic Drop for the Determination of Trace Cobalt in Water Samples

A liquid‐phase microextraction technique was developed using dispersive liquid‐liquid microextraction based on solidification of floating organic drop combined with flame atomic absorption spectrometry, for the extraction and determination of trace amounts of cobalt in water samples. Microextraction efficiency factors, such as the type and volume of extraction and dispersive solvents, pH, extraction time, the chelating agent amount, and ionic strength were investigated and optimized. Under optimum conditions, an enrichment factor of 160 was obtained from 10.0 mL of water sample. The calibration graph was linearin the range of 1.15‐110 μg L^?1 with a detection limit of 0.35 μg L^?1. The relative standard deviation for ten replicate measurements of 10 and 100 μg L^?1 of cobalt were 3.26% and 2.57%, respectively. The proposed method was assessed through the analysis of certified reference water or recovery experiments.     

Optimization of a novel method based on solidification of floating organic droplet by high-performance liquid chromatography for evaluation of antifungal drugs in biological samples

In this study, a simple, rapid, and highly efficient liquid-phase microextraction method based on solidification of floating organic droplet was coupled with high performance liquid chromatography-photo diode array detection (HPLC-PDA) for determination of ketoconazole, clotrimazole, and miconazole as antifungal drugs. Central composite design (CCD) was used for optimization of several factors affecting the extraction efficiency. The optimized conditions were established to be 550 rpm for stirring rate, 35 min for extraction time, 57 °C for extraction temperature, 8.5 for solution pH, 10 μl for organic solvent volume, and 7% (w/v) of NaCl for ionic strength. Limit of detections (LODs) of the extraction method ranged from 0.01 to 0.1 μg L⁻¹ and the linear dynamic ranges (LDRs) ranged from 0.1 to 300 μg L⁻¹ for the three antifungal drugs. Relative standard deviations (RSDs) of the proposed method were 5-11%. Preconcentration factors in the range of 306-1350 were obtained at extraction time of 35 min. Finally, performance of the proposed method was evaluated for the extraction and determination of the drugs’ levels in microgram per liter in samples and satisfactory results were obtained.     

Evaluation of dispersive liquid-liquid microextraction for the simultaneous determination of chlorophenols and haloanisoles in wines and cork stoppers using gas chromatography-mass spectrometry

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was evaluated for the simultaneous determination of five chlorophenols and seven haloanisoles in wines and cork stoppers. Parameters, such as the nature and volume of the extracting and disperser solvents, extraction time, salt addition, centrifugation time and sample volume or mass, affecting the DLLME were carefully optimized to extract and preconcentrate chlorophenols, in the form of their acetylated derivatives, and haloanisoles. In this extraction method, 1mL of acetone (disperser solvent) containing 30μL of carbon tetrachloride (extraction solvent) was rapidly injected by a syringe into 5mL of sample solution containing 200μL of acetic anhydride (derivatizing reagent) and 0.5mL of phosphate buffer solution, thereby forming a cloudy solution. After extraction, phase separation was performed by centrifugation, and a volume of 4μL of the sedimented phase was analyzed by GC-MS. The wine samples were directly used for the DLLME extraction (red wines required a 1:1 dilution with water). For cork samples, the target analytes were first extracted with pentane, the solvent was evaporated and the residue reconstituted with acetone before DLLME. The use of an internal standard (2,4-dibromoanisole) notably improved the repeatability of the procedure. Under the optimized conditions, detection limits ranged from 0.004 to 0.108ngmL(-1) in wine samples (24-220pgg(-1) in corks), depending on the compound and the sample analyzed. The enrichment factors for haloanisoles were in the 380-700-fold range.     

Determination of the steroid hormone levels in water samples by dispersive liquid-liquid microextraction with solidification of a floating organic drop followed by high-performance liquid chromatography

In this study, the steroid hormone levels in river and tap water samples were determined by using a novel dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO). Several parameters were optimized, including the type and volume of the extraction and dispersive solvents, extraction time, and salt effect. DLLME-SFO is a fast, cheap, and easy-to-use method for detecting trace levels of samples. Most importantly, this method uses less-toxic solvent. The correlation coefficient of the calibration curve was higher than 0.9991. The linear range was from 5 to 1000 μg L⁻¹. The spiked environmental water samples were analyzed using DLLME-SFO. The relative recoveries ranged from 87% to 116% for river water (which was spiked with 4 μg L⁻¹ for E1, 3 μg L⁻¹ for E2, 4 μg L⁻¹ for EE2 and 9 μg L⁻¹ for E3) and 89% to 102% for tap water (which was spiked with 6 μg L⁻¹ for E1, 5 μg L⁻¹ for E2, 6 μg L⁻¹ for EE2 and 10 μg L⁻¹ for E3). The detection limits of the method ranged from 0.8 to 2.7 μg L⁻¹ for spiked river water and 1.4 to 3.1 μg L⁻¹ for spiked tap water. The methods precision ranged from 8% to 14% for spiked river water and 7% to 14% for spiked tap water.     

A new sample preparation method for determination of acidic drugs in sewage sludge applying microwave assisted solvent extraction followed by gas chromatography-mass spectrometry

This paper presents a new sample preparation procedure for determination of selected acidic pharmaceuticals (ibuprofen, naproxen, ketoprofen, and diclofenac) in sewage sludge using microwave assisted solvent extraction, dispersive matrix extraction (DME) followed by the conventionally applied solid phase extraction (SPE), derivatization, and gas chromatography-mass spectrometry. The recoveries calculated from analytical data of spiked sludge samples changed in the range of 80-105% ± 15% for the four pharmaceuticals in mixed and activated sludge depending on the efficiency of the clean-up procedure. The measured concentration values of ibuprofen and naproxen were identical in the mixed and the activated sludge samples. However, ketoprofen and diclofenac showed about twice as high concentration in activated sludge than in the mixed one independently of the applied extraction method. The typical concentration ranges of ibuprofen, naproxen, ketoprofen and diclofenac in sewage sludge were 10-30 ng/g, 30-50 ng/g, 50-130 ng/g, and 50-140 ng/g respectively.     

Combination of ionic liquid-based dispersive liquid-liquid micro-extraction with stopped-flow spectrofluorometry for the pre-concentration and determination of aluminum in natural waters, fruit juice and food samples

In this research, we combined ionic liquid-based dispersive liquid-liquid micro-extraction (IL-based DLLME) with stopped-flow spectrofluorometry (SFS) to evaluate the concentration of aluminum in different real samples at trace level. 1-Hexylpyridinium hexafluorophosphate [Hpy][PF₆] ionic liquid and 8-hydroxyquinoline (oxine), which forms a highly fluorescent complex with Al³⁺, were chosen as the extraction solvent and chelating agent, respectively. The hydrophobic Al-oxine complex was extracted into the [Hpy][PF₆] and separated from the aqueous phase. Then, the concentration of the enriched aluminum in the sediment phase was determined by SFS. Some effective parameters that influence the SFS signals and the micro-extraction efficiency, such as the suction and sending time, the concentration of the chelating agent, pH, the amount of the ionic liquid, the type of disperser solvent and diluting agent, ionic strength, extraction time, equilibration temperature and centrifugation time were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and enrichment factor were 0.05 μg L⁻¹ and 100, respectively. The relative standard deviation (RSD) for six replicate determinations of 6 μg L⁻¹ Al was 1.7%. The calibration graph using the pre-concentration system was linear in the range of 0.06-15 μg L⁻¹ with a correlation coefficient of 0.9989. The developed method was validated by the analysis of certified reference materials and applied successfully to the determination of aluminum in several water, fruit juice and food samples.     

分散固相萃取-高效液相色谱-质谱联用法测定水稻秸秆、糙米、稻壳和土壤中戊唑醇残留

建立了分散固相萃取-液相色谱-质谱法测定水稻秸秆、糙米、稻壳及土壤中戊唑醇残留量。方法以乙腈为萃取溶剂,N-丙基-乙二胺(PSA)为吸附剂,实现样品快速制备;在Zorbax Eclipse XDB-C18色谱柱上,以甲醇-5 mmol乙酸铵缓冲溶液(70/30,V/V)为流动相,采用电喷雾质谱检测器,选择离子监测模式,以m/z308为定量检测离子,戊唑醇保留时间在9.5 min左右,在0.005~2 mg/L范围内浓度与峰面积呈良好的线性关系,相关系数为0.9999。在4种样本中添加不同浓度戊唑醇其平均回收率在73.6%~105.8%,相对标准偏差(n=5)小于15%,检出限(S/N=5)为2.5×10-11g。该方法简单、快速、灵敏、准确。     

分散液相微萃取-气相色谱/质谱快速分析水中的硝基苯类化合物

建立了分散液相微萃取.气相色谱,质谱快速分析水中硝基苯、对硝基苯、1,3一二硝基苯和2,4-二硝基氯苯的新方法.将含有18μL氯苯(萃取荆)的0.25 mL丙酮(分散剂)作为萃取体系,快速注入到5.0 mL水溶液中.在4000r/min下离心2.0 min后,得到(10.0±0.5)μL沉积相(氯苯),取底部沉积相1.0μL进行气相色谱,质谱分析.方法线性范围0.5～50μg/L(r2=0.9986～0.9994),检出限0.2～0.5μg/L,相对标准偏差4.2%～7.3%(n=5).将该方法用于环境水样的测定,加标回收率72.9%～89.6%.     

Multiresidue analytical method of pesticides in peanut oil using low-temperature cleanup and dispersive solid phase extraction by GC-MS

A method for the determination of 33 pesticides in peanut oil by GC-MS was described. Two extraction procedures based on (i) low-temperature extraction and (ii) liquid-liquid extraction were tested for the optimization of the method. The mixture of anhydrous MgSO(4) with primary secondary amine (PSA) or with PSA and C(18) was performed as sorbents in dispersive SPE. Low temperature along with PSA and C(18) cleanup gave the best results. Pesticides were identified and quantified by GC-MS in SIM mode. The correlation coefficients, R(2), in the linear range tests were better than 0.990. The average recoveries for most pesticides (spiked at 0.02, 0.05, 0.2, and 1 mg/kg) ranged from 70 to 110%, the RSD was below 20% in most instances, and LODs varied from 0.5 to 8 mug/kg.