[Determination of 14 aniline and benzidine compounds in soil by gas chromatography-mass spectrometry].

The complex matrix of soil samples and low extraction efficiency of aniline compounds limit many methods developed for detecting aniline and benzidine compounds in soil. In this study, a rapid and sensitive method based on gas chromatography-mass spectrometry was developed for the simultaneous determination of 14 aniline and benzidine compounds in soil. The collected soil samples were sealed with 5% sodium sulfite solution and refrigerated to inhibit the oxidation of the target compounds for up to 7 d. The extraction efficiencies of accelerated solvent extraction and oscillating dispersion extraction were compared, and the recovery of accelerated solvent extraction was found to be unsuitable. Hence, three-phase oscillating dispersion extraction was adopted. A certain amount of alkaline aqueous solution was added to the test system during extraction to improve the extraction efficiency because aniline and benzidine compounds are weakly alkaline substances. When the pH of the extracted water phase was greater than 12, relatively good recoveries were obtained. Next, a mixed solvent of ethyl acetate-methylene chloride (1∶4, v/v) was added to extract the target compounds via oscillation for 20 min. The solid phase was discarded via centrifugation, and the aqueous and organic phases were transferred to a liquid separation funnel for further separation. Finally, the organic phase was retained. This pretreatment process prevents the co-extraction of acidic compounds or other impurities, thereby enhancing the purification ability of the method. Solid phase extraction (SPE) is generally recommended for soil extraction and purification. A preliminary test showed that compared with other columns, the Florisil SPE column could better retain the target substances and exhibited higher elution efficiency. After purification, the organic phase was concentrated to 1 mL using a nitrogen blower. The analytes were analyzed by gas chromatography-mass spectrometry using a capillary column (DB-35MS, 30 m×0.25 mm×0.25 µm). The temperature program was optimized to separate the target compounds at the baseline. Specifically, the initial oven temperature was set to 60 ℃, held for 2 min, increased to 130 ℃ at a rate of 5 ℃/min, increased to 300 ℃ at a rate of 30 ℃/min, and held for 4 min. The injector and ion source temperatures were 250 and 300 ℃, respectively. Aniline-d5 and acenaphthene-d10 were used as the internal standards for quantification. The effects of antioxidant addition, extraction solvent type, salting out, and other factors on extraction efficiency were investigated. The results showed that the method performed well under the optimized experimental conditions when actual soils were used as real sample matrices. The accuracy and precision of the proposed method were verified. A total of 14 aniline and benzidine compounds demonstrated good linearities in the range of 0.5-100 mg/L. The method detection limits (MDLs) ranged from 0.02 to 0.07 mg/kg, and the limits of quantification (LOQs) ranged from 0.08 to 0.28 mg/kg. The target compounds were spiked at contents of 1 and 10 mg/kg. The spiked recoveries of the 14 targets in actual soils were 62.9%-101%, and the relative standard deviations (RSDs) of six precision tests were 3.8%-10.3%. The proposed method effectively inhibited the oxidation of aniline and benzidine compounds during extraction, and the target compounds exhibited high recoveries and good stabilities in the presence of three phases. Moreover, the operating procedure was simple and easy to implement. The proposed method was applied to the soil collected from an industrial enterprise in Jiangsu province that was suspected to be contaminated with aniline, and two aniline compounds were detected. The developed method requires a small sample size, and the preservation step is simple and effective. In addition, it can be applied to various types of actual soils. The method meets the requirements of current soil pollution risk control standards for aniline and benzidine compounds in soils.

A fluorescence "turn-on" probe for Cu (â ¡) based on flavonoid intermediates generated by copper-induced oxidative cyclization and its fluorescence imaging in living cells.

A fluorescence "turn-on" probe for Cu (Ⅱ) ions was prepared based on the condensation reaction of coumaraldehyde and 1-hydroxy-2-acetylnaphthalene. A strong fluorescent flavonoid intermediate was formed and verified by the NMR and ESI-MS experiments. The water-soluble and pH dependence experiments were performed to confirm the optimal solvent condition (CH3CN: HEPES = 1:1, v/v, pH = 7.2-7.4). The dynamic experiments indicated that the formation process of the intermediate catalyzed by Cu(Ⅱ) ions was probably pseudo-first-order reaction process. The probe showed good selectivity toward copper ions and almost no interference except Ag+ ions by the selectivity and competitive experiments. The HeLa cells were used in the cell fluorescence imaging tests and it was demonstrated that the probe could be used in the phycological condition and showed weak cytotoxicity by the MTT experiments.

[Determination of polycyclic aromatic hydrocarbons in airborne particles by microwave extraction-high performance liquid chromatography].

A method by using microwave extraction and high performance liquid chromatography was developed to determine polycyclic aromatic hydrocarbons (PAHs) in airborne particles. The glass/quartz fiber filter, on which particles adsorbed, was extracted with a mixed solvent n-hexane/acetone (1:1, v/v) using microwave, and the subsequent purification of the extract was carried out by a florisil cartridge. The prepared sample was determined by high performance liquid chromatography coupled with photodiode array (PDA) and fluorescence dual-detector. The target compounds showed good linearity between the mass concentration of 20.0 µg/L and 500 µg/L, with the correlation coefficients not less than 0.9960. The spiked recoveries of target compounds in blank filter ranged from 56.3%-101%. The current method has been applied to investigate the distribution of PAHs in airborne particles in Nanjing City.

[Determination of trace and ultra-trace level bromate in water by large volume sample injection with enrichment column for on-line preconcentration coupled with ion chromatography].

A method for the determination of trace and ultra-trace level bromate in water by ion chromatography with large volume sample injection for on-line preconcentration was established. A high capacity Dionex IonPac AG23 guard column was simply used as the enrichment column instead of the loop for the preconcentration of bromate. High purity KOH solution used as eluent for gradient elution was on-line produced by an eluent generator automatically. The results showed that a good linear relationship of bromate was exhibited in the range of 0.05-51.2 µg/L (r ≥ 0.999 5), and the method detection limit was 0.01 µg/L. Compared with conventional sample injection, the injection volume was up to 5 mL, and the enrichment factor of this method was about 240 times. This method was successfully applied for several real samples of pure water which were purchased in the supermarket, and the recoveries of bromate were between 90%-100% with the RSDs (n = 6) of 2.1%-6.4% at two spiked levels. This method without pretreatment is simple, and of high accuracy and precision. The preconcentration can be achieved by large volume sample injection. It is suitable for the analysis of trace and ultra-trace level bromate.

[Determination of 21 phenolic compounds in soil by ultrasonic extraction-gas chromatography].

An effective method was developed to determine phenolic compounds in soil by ultrasonic extraction-gas chromatography (GC). The soil sample was extracted with methylene dichloride-hexane (2:1, v/v) for 3 min with the extraction temperature lower than 50 degrees C for 3 times. The extract was purified by alkaline aqueous solution (pH > 12), and the phenolic compounds were dissolved in aqueous solution. After the organic solution was discarded, the aqueous solution was adjusted to pH <3 and subsequently extracted with methylene dichloride-ethyl acetate (4:1, v/v) twice. The analytes were determined by GC-FID and quantified by external standard method. The limits of quantification for all tested phenolic compounds were 0.01-0.06 mg/kg in about 10 g soil samples. The recoveries were between 62.9% and 111.4% with the relative standard deviations (RSDs) in the range of 4.3%-24.0% (n = 6). The results showed that this method is sensitive, accurate, and suitable for the determination of the 21 phenolic compounds in soil.

Comparison of various extraction methods for policosanol from rice bran wax and establishment of chromatographic fingerprint of policosanol.

A capillary gas chromatographic (GC) method has been developed for the separation and determination of policosanol components extracted from rice bran wax. A Varian CP-sil 8 CB column was employed, and an oven temperature was programmed. Gas chromatography-mass spectrometry (GC-MS) was used to identify the composition of policosanol. Quantitative analysis was carried out by means of hydrogen flame ionization detector (FID) with dinonyl phthalate (DNP) as internal standard. The results indicated that the extract obtained by dry saponification has the highest contents of octacosanol and triacontanol among extracts by all used extraction methods including dry saponification, saponification in alcohol, saponification in water (neutralized and non-neutralized), and transesterification. Meanwhile, the GC-MS fingerprint of policosanol extracted by dry saponification has been established. Euclidean distance similarity calculation showed remarkable consistency of compositions and contents among 12 batches of policosanol from a rice bran wax variety. This protocol provided a rapid and feasible method for quality control of policosanol products.