Phenanthrene degradation in subcritical water

Subcritical water (<374 °C and <221 bar) has unique characteristics such as dramatically decreased dielectric constant, surface tension, and viscosity with increasing temperature, allowing for dissolution and reaction of organics in high-temperature water to occur. Additionally, the dissociation constant of water at temperatures of 200-300 °C is three orders of magnitude greater than that of ambient water, which may also contribute to the reactivity of subcritical water with certain organic compounds. In this study, the degradation and oxidation of phenanthrene in subcritical water were investigated. Both deionized water and water with 3% hydrogen peroxide were used in the degradation and oxidation studies. The effect of temperature on degradation efficiency has been determined with a temperature range of 100-350 °C. When the temperature was increased from 150 to 350 °C, the amount of phenanthrene degraded varied from 6 to 243 μg in each milliliter of deionized water. However, these quantities were increased to 195 μg at 150 °C and 3680 μg at 350 °C in each milliliter of water with 3% hydrogen peroxide. Several degradation products including phenol, benzoic acid, and ketones were identified by using gas chromatography/mass spectrometry (GC/MS).     

Properties of subcritical water as an eluent for reversed-phase liquid chromatography—Disruption of the hydrogen-bond network at elevated temperature and its consequences

The use of subcritical water as an eluent for reversed-phase liquid chromatography is further explored. Shape selectivity as well as thermodynamic values for solute transfer were measured and compared to those seen with traditional ambient methanol/water and acetonitrile/water mobile phases. Linear solvation energy analysis was also used to analyze extrapolated values of the retention factor in pure water at ambient temperatures (k^′_w${k^{\prime }}_w$) for subcritical water and ambient hydroorganic mobile phases. Results indicate that it is likely that a large disruption in the hydrogen-bonding network of water at high temperatures causes unique chromatographic selectivity, as well as prohibits accurate extrapolation from high temperature to ambient conditions using pure water. Additionally, subcritical water was not found to be a suitable mobile phase for determining k^′_w${k^{\prime }}_w$ for use in estimating octanol/water partition coefficients.     

非线性主成分回归分光光度法同时测定复方制剂中两组分的含量

构造多组分体系的非线性模型,并用主成分回归法来解析,建立了同时测定两组分的非线性主成分回归分光光度法,方法用于复方苯甲酸制剂中苯甲酸和水杨酸含量的测定,结果优于线性主成分回归分光光度法。     

Determination of benzoic acid in milk by solid-phase extraction and ion chromatography with conductivity detection

A simple, fast, precise and eco-friendly method, based on ion chromatography (IC) with a suppressed conductivity detector, was proposed for the determination of benzoic acid (BA) inmilk in this paper. The chromatographic separation was accomplished by using an anion exchange column eluted with 3.2 μmol/L aqueous Na2CO3 and 1.0 mmol/L aqueous NaHCO3 at a flow-rate of 0.7 mL/min. Themethod validation experiment provided excellent results with respect to linearity (correlation coefficient up to 0.9997), limit of detection (0.1 μg/L), recovery values (ranging from 88.0% to 93.0%) and relative standard deviation (RSD) (below 2.2%, n = 7).     

Separation of polar and non-polar analytes using dimethyl sulfoxide-modified subcritical water

Separations using methanol–water or acetonitrile–water mixtures at different temperatures have been well investigated in reversed-phase liquid chromatography. However, reversed-phase separation with dimethyl sulfoxide (DMSO)–water mixtures is much less studied. In this work, separations of polyhydroxybenzenes, phenol derivatives, benzene, toluene, ethylbenzene, and xylenes (BTEX), and polycyclic aromatic hydrocarbons (PAHs) with DMSO-modified subcritical water were performed at several temperatures to evaluate the effect of temperature on the elution strength of DMSO–water mixtures. The column efficiency obtained by using DMSO-modified subcritical water was also studied. Finally, the resolution of ethylbenzene and p-xylene was investigated.     

食品中苯甲酸和山梨酸的气相色谱法分离分析

用毛细管气相色谱法对食品中的防腐剂苯甲酸和山梨酸进行了分离分析。样品用乙醚萃取，萃取物蒸发至干，残渣用氯仿溶解后直接进行色谱分析，FFAP石英毛细管柱，柱温220℃，邻苯二甲酸二甲酯为内标物。两种化合物在0.25mg/mL-4.00mg/mL范围内具有良好的线性关系。     

Evaluation of surfactant‐assisted pressurized hot water extraction for marker compounds in Radix Codonopsis pilosula using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry

In the move towards the elimination of organic solvents in the extraction process in botanicals, a new method combining surfactant and pressurized hot water extraction (PWHE) with an applied temperature below the boiling point and lower pressure from 10 to 20 bar was developed for the analysis of marker compounds that are reasonably hydrophobic such as tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol and tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol‐O‐β‐D‐glucoside in Radix Codonopsis pilosula (DangShen). Because reference substances for the proposed botanicals were not available, a method was developed to isolate the marker compounds in Radix Codonopsis pilosula. Other than surfactant‐assisted PHWE, the marker compounds present in Radix Codonopsis pilosula were extracted using pressurized liquid extraction (PLE) with methanol and PHWE with a mixture of water/ethanol (80:20). The extracts were analyzed using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry. With surfactant‐assisted PHWE, the effects of different added surfactants such as sodium dodecyl sulfate and Triton X‐100 was studied. Surfactant assisted PHWE with Triton X‐100 proved to be at least equivalent or better compared to Soxhlet extraction in terms of quantitative analysis of marker compounds in Radix Codonopsis pilosula. The method precision was less than 8% (RSD, n = 6). The presence of surfactants in PHWE was found to enhance the solubility of target compounds naturally occurring in medicinal plants.     

Pressurized hot water extraction of berberine, baicalein and glycyrrhizin in medicinal plants

Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC.     

Determination of airborne carbonyls via pentafluorophenylhydrazine derivatisation by GC-MS and its comparison with HPLC method

The classical analytical method for gaseous carbonyl measurements based on solid sorbent coated with 2,4-dinitrophenylhydrazine (DNPH) and analysis by HPLC/UV suffers from limited resolution of carbonyls with similar molecular structures and high molecular weights. In this paper, we report the development of a sensitive and reliable analytical method for simultaneous determination of 21 airborne carbonyls within the C₁-C₉ range. Carbonyls were collected on a sampling tube filled with 100 mg Tenax TA (60-80 mesh) sorbent coated with 1 μmol pentafluorophenyl hydrazine (PFPH), followed by solvent desorption and analysis by gas chromatography (GC)/mass spectrometry (MS). Common carbonyl gases including formaldehyde, acetaldehyde, butyraldehyde, hexaldehyde and benzaldehyde at ppbv levels were collected with efficiency greater than 90% onto sampling tubes at a flow rate of 100 mL min⁻¹. The limits of detection (LODs, signal/noise = 3) of the tested carbonyls were in the range of 0.08-0.20 ppbv for a sampled volume of 24.0 L. These limits are less than or comparable with those that can be obtained using the DNPH-HPLC method. The method has been field-tested both in ambient air of York and in diluted cigarette smoke. Comparing field tests with the classical DNPH-HPLC method, good agreement was displayed between the two methods for the same carbonyls, but with more carbonyl species detected by the PFPH-GC/MS method. The PFPH-GC/MS method provides better molecular separation for carbonyls with similar structures, is highly sensitivity and gives confirmation of identification by structures when detected using MS.     

Determination of oxytetracycline, tetracycline and chloramphenicol antibiotics in animal feeds using subcritical water extraction and high performance liquid chromatography

A rapid analytical method for the determination of oxytetracycline (OTC), tetracycline (TC) and chloramphenicol (CAP) antibiotics in animal feeds has been developed based on subcritical water extraction (SWE) without further sample clean-up followed by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. On extracting target antibiotics from spiked samples, the efficiency of the water extraction device was evaluated in terms of pH and volume of the extractant, temperature and time of the static extraction. The best extraction conditions were obtained by using 5.5 mL of water adjusted to pH 2 with hydrochloric acid as the extractant at 100 °C with 5-min static extraction. After filtration, 20 μL of the aqueous extract was directly injected into the HPLC column. Recoveries between 82.1% and 90.0% with relative standard deviations ranging between 1.6% and 4.8% were achieved from spiked animal feed samples by using this method. Compared with the traditional ultrasonic extraction, this procedure was remarkably more efficient in extracting OTC, TC and CAP, simpler to perform, and there was no use of toxic organic solvents.     

Automated on-fiber derivatization with headspace SPME-GC-MS-MS for the determination of primary amines in sewage sludge using pressurized hot water extraction

An automated, environmentally friendly, simple, selective, and sensitive method was developed for the determination of ten primary aliphatic amines in sewage sludge at μg/kg dry weight (d.w.). The procedure involves a pressurized hot water extraction (PHWE) of the analytes from the solid matrix, followed by a fully automated on‐fiber derivatization with 2,3,4,5‐pentafluorobenzaldehyde (PFBAY) and headspace solid‐phase microextraction (HS‐SPME) and subsequent gas chromatography ion‐trap tandem mass spectrometry (GC‐IT‐MS‐MS) analysis. The limits of detection (LODs) of the method were between 0.5 and 45 μg/kg (d.w.) for all compounds except for ethyl‐, isopropyl‐, and amylamine, whose LODs were 70, 109, and 116 μg/kg (d.w.), respectively. The limits of quantification (LOQs) were between 10 and 350 μg/kg (d.w.). Repeatability and intermediate precision, expressed as RSD(%) (n=3), were lower than 18 and 21%, respectively. The method developed enabled to determine primary aliphatic amines in sludge from various urban and industrial sewage treatment plants as well as from a potable treatment plant. Most of the primary aliphatic amines were found in the sewage sludge samples analyzed corresponding to the maximum concentrations to the samples from the urban plant: for instance, isobutylamine and methylamine were found at 7728 and 12 536 μg/kg (d.w.), respectively. Amylamine was detected only in few samples but always at concentrations lower than its LOQ.     

The effect of temperature on the solubility of benzoic acid derivatives in water

Using a laser monitoring observation technique, solubilities of o-nitro-benzoic acid, p-hydro-benzoic acid, p-methyl-benzoic acid and m-methyl-benzoic acid in water have been measured in the temperature range 290.15–323.15 K. The experimental data are regressed with the Wilson equation and the λH equation. The experimental results show that solubilities of these compounds in the range of 10⁻⁴–10⁻⁵ mole fraction in water, increase significantly with temperature. Except for o-nitro-benzoic acid, the solubility data are described adequately with the Wilson equation. The λH equation gives good agreement with all experimental data. The results indicate that the molecular structure and interactions affect the solubilities significantly.     

Identification and Determination of Nicorandil and its Degradation Products by HPLC and GC/MS

Nicorandil [N-(2-hydroxyethyl)-nicotinamide nitrate NIC] is a novel kind of compound in the treatment of angina pectoris. NIC can be degraded easily in storage. The degradation products include N-(2-hydroxyethy) nicotinamide (HN), nitrate ion (NI), and ni…     

基于纯水提取的烟熏鲣鱼中肌苷酸的提取方法

建立了一种基于纯水提取的新型烟熏鲣鱼中肌苷酸的提取方法。样品前处理采用95 ℃的纯水作为提取液,提取5 min。采用的色谱条件: 色谱柱为Agilent Zorbax SB-C18柱(150 mm×4.6 mm, 5 μm),柱温为30 ℃,流动相为甲醇-50 mmol/L乙酸铵水溶液(5:95, v/v),流速为1.0 mL/min,检测波长为254 nm。结果表明,该方法测定烟熏鲣鱼中肌苷酸含量的线性范围为1.0～120.0 mg/L;在0.40、2.00、4.00 g/kg (n=3)的添加水平下,回收率为84.6%～100.2%,测定结果的相对标准偏差(RSD)为1.00%～6.12%;检出限(信噪比(S/N)为3)为4 mg/kg;定量限(S/N=10)为12 mg/kg。该方法与常规采用的基于高氯酸的提取方法相比较,提取效率提高了37.0%,并且该方法操作安全、与环境友好,对烟熏鲣鱼中肌苷酸含量测定准确度良好,对其他食品中肌苷酸含量的测定具有借鉴意义,是一种值得推广的样品预处理方法。     

Solid phase extraction and analysis of horse urine for aminocaproic acid

Summary A rapid and efficient procedure is described for extraction and determination of aminocaproic acid in horse urine. Urine was extracted by passing through a bonded silica column (Bond-Elut). The adsorbed drug was washed free of endogenous materials before being eluted. The extract was then examined by thin-layer chromatography and HPLC. The purity of the extract was determined by gas chromatography-mass spectrometry.     

Industrial application of green chromatography--I. Separation and analysis of niacinamide in skincare creams using pure water as the mobile phase

In this work, chromatographic separation of niacin and niacinamide using pure water as the sole component in the mobile phase has been investigated. The separation and analysis of niacinamide have been optimized using three columns at different temperatures and various flow rates. Our results clearly demonstrate that separation and analysis of niacinamide from skincare products can be achieved using pure water as the eluent at 60 °C on a Waters XTerra MS C18 column, a Waters XBridge C18 column, or at 80 °C on a Hamilton PRP-1 column. The separation efficiency, quantification quality, and analysis time of this new method are at least comparable with those of the traditional HPLC methods. Compared with traditional HPLC, the major advantage of this newly developed green chromatography technique is the elimination of organic solvents required in the HPLC mobile phase. In addition, the pure water chromatography separations described in this work can be directly applied in industrial plant settings without further modification of the existing HPLC equipment.     

气相色谱测定食品中丙酸及其盐类

建立了气相色谱测定食品中丙酸及丙酸盐的分析方法。针对含油脂和不含油脂的食品，分别建立了脱脂提取法和直接提取法。考察不同pH值对丙酸溶解性和加标回收率的影响，通过对净化条件、pH值、提取剂的种类和提取次数等条件的优化，确定最佳处理条件为：样品加盐酸溶液调节pH ≤ 2，用5 mL正己烷脱脂，用5 mL乙酸乙酯提取2次，合并提取液，使用HP-INNOWAX毛细管色谱柱对丙酸进行分离，用氢火焰离子化检测器检测，外标法定量。结果表明，使用脱脂提取法得到丙酸的回收率为87.5%~97.6%，相对标准偏差为3.09%~6.86%（n=6）；使用直接提取法得到丙酸的平均回收率为90.1%~102.1%，相对标准偏差为3.32%~6.33%（n=6）。两种方法的线性范围为2~1000 mg/L（相关系数为0.9998），检出限为0.003 g/kg，定量限为0.01 g/kg。方法适用于多种食品中丙酸的检测，具有准确、快速、简便、灵敏度高等优点，为食品中丙酸含量的测定提供了新途径。     

野西瓜种子油中脂肪酸的气相色谱-质谱分析

采用加速溶剂萃取及索氏提取法,用正己烷和乙醚为提取剂从野西瓜种子中提取油脂,经浓H2SO4催化,甲醇甲酯化处理后,以气相色谱-质谱联用技术鉴定出野西瓜种子中的脂肪酸主要组成为:油酸、亚油酸、硬脂酸等,其中不饱和脂肪酸总量占91.4%,主要成分油酸占73.3%。野西瓜种子油具有较高的营养价值,同时也可为生物柴油提供良好的原料。     

Method for determination of fatty acid amides in polyethylene packaging materials—Gas chromatography/mass spectrometry

A new method for determination of fatty acid amides in polyethylene packaging film was developed using gas chromatography/mass spectrometry (GC/MS). Liquid extraction, Soxhlet extraction ultrasonic-assisted extraction and pressurized solvent extraction (PSE) methods were compared and the results showed that pressurized solvent extraction was the best for extracting these compounds. After extraction, solvent was blown by nitrogen and a trifluoroethyl derivation step was carried out. The derivative compounds were identified and quantified by GC/MS using an HP-Innowax column. The retention times were 6.20 min for derivative hexadecanoamide, 8.56 min for derivative octadecanamide, 8.84 min for derivative oleamide and 13.68 min for derivative erucamide, respectively. The detection limits were 61.0 ng g⁻¹, 74.0 ng g⁻¹, 103.0 ng g⁻¹, and 105.0 ng g⁻¹, respectively, and the linearity were good. The proposed method was applied satisfactorily to determine these chemicals in different types of polyethylene samples.     

捕集阱顶空气相色谱/质谱法测定水中的二氯一溴甲烷

建立了捕集阱顶空气相色谱/质谱测定水中二氯一溴甲烷的方法。采用正交实验设计对平衡温度、平衡时间、循环次数3个参数进行了优化,在平衡温度70 ℃、平衡时间20 min、循环次数2次的优化条件下,对水中的二氯一溴甲烷进行测定。结果显示,在0.1～10.0 μg/L范围内,二氯一溴甲烷的质量浓度和峰面积呈良好的线性关系,相关系数为0.9991。方法的检出限(S/N=3)为0.03 μg/L,定量限(S/N=10)为0.1 μg/L,回收率为83.1%～111.3%,相对标准偏差为1.7%～5.2%(n=6)。将该方法应用于水中二氯一溴甲烷的定性定量分析,效果良好。