Determination of chloramphenicol, enrofloxacin and 29 pesticides residues in bovine milk by liquid chromatography-tandem mass spectrometry

A sensitive method for determination of chloramphenicol, enrofloxacin and 29 pesticides residues in bovine milk by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. Residues of the targets were extracted from milk with acetonitrile, cleaned up by C₁₈-SPE cartridge, and then determined by HPLC-MS/MS. The MS detection was operated in positive or negative ionization mode, depending on the compounds. For confirmation of each target compound, two precursor ion > product ion transitions were selected by multi-reaction monitoring mode (MRM). The method showed good linearity for all the tested compounds over the studied concentration range with correlation coefficient higher than 0.9910. Recoveries for the studied compounds at three spiked levels (0.05, 0.10, 0.19 mg kg⁻¹) in bovine milk were in the range of 71-107% with RSDs not larger than 13.7%, except that recoveries of trifluralin ranged between 62% and 70% at the spiked levels. Limits of quantitation for the analytes were estimated to range between 0.03 × 10⁻³ and 14.5 × 10⁻³ mg kg⁻¹. The proposed method was applied for the determination of the analytes residues in real samples. The found levels of the analytes in milk samples were lower than maximum residues levels (MRL).     

Occurrence of multiclass UV filters in treated sewage sludge from wastewater treatment plants

Many substances related to human activities end up in wastewater and accumulate in sewage sludge. So far, there is only one extensive survey on the occurrence of UV filter residues in sewage sludge. However, more data are required to draw a reliable picture of the fate and effects of these compounds in the environment. This study attempts to fill this gap through the determination of selected UV filters and derivatives namely 4-methylbenzylidenecamphor, benzophenone-3, octocrylene, ethylhexylmethoxycinnamate, ethylhexyldimethyl PABA, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, and 4,4′-dihydroxybenzophenone in treated sewage sludge.The target compounds were extracted using pressurized liquid extraction and after this, determined by ultra high resolution liquid chromatography-tandem mass spectrometry. The determination was fast and sensitive, affording limits of detection lower than 19 ng g⁻¹ dry weight (dw) except for 2,4-dihydroxybenzophenone (60 ng g⁻¹ dw). Good recovery rates, especially given the high complexity of sludge matrix (between 70% and 102% except for 2,4-dihydroxybenzophenone (30%)) were achieved.The application of developed method allowed reporting for the first time the occurrence of two major degradation products of benzophenone-3 that have estrogenic activity in sewage sludge: 4,4′-dihydroxybenzophenone (in 5/15 WWTPs) and 4-hydroxybenzophenone (in 1/15 WWTPs). Results revealed the presence of UV filters in 15 wastewater treatment plants in Catalonia (Spain) at concentrations ranging from 0.04 to 9.17 μg g⁻¹ dw.     

Incidence of thyroid disease following exposure to polybrominated biphenyls and polychlorinated biphenyls, Michigan, 1974-2006

Thyroid hormones, which influence body metabolism and development, could be affected by persistent organic pollutants. We sought to examine the relationship between polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) and thyroid disease. We employed incidence density sampling to perform a nested case control analysis of the Michigan Long-Term PBB Cohort. Cohort members (n = 3333) were exposed to PBBs through contaminated cattle feed in 1973-1974 and to PCBs through daily life. Those with detectable serum PBB and PCB concentrations at enrollment were categorized into tertiles of PBB and PCB exposure. Case-patients were cohort members answering “Yes” to “Has a healthcare provider ever told you that you had a thyroid problem?” during follow-up interviews; control-patients were cohort members answering “No”. We used odds ratios (OR) with 95% confidence intervals (CI) to compare odds of thyroid disease by PBB and PCB exposure and by various risk factors. Total cumulative thyroid disease incidence after 33 years was 13.9% among women and 2.6% among men. After adjusting for body mass index, we found no statistically significant differences in odds of any type of thyroid disease among women or men with elevated PBB or PCB exposure. Compared to control-patients, women with thyroid disease had increased odds of being overweight/obese (OR = 2.82, 95% CI: 1.94-4.11) and developing infertility (OR = 1.71, 95% CI: 1.08-2.69), diabetes (OR = 1.61, 95% CI: 1.04-2.51), or arthritis (OR = 1.71, 95% CI: 1.18-2.50) during follow-up. Additional research should explore potential associations between PBBs/PCBs and thyroid disease among children exposed in utero.     

Retention time profiling of all 136 tetra- through octa- chlorinated dibenzo-p-dioxins and dibenzofurans on a variety of Si-Arylene gas chromatographic stationary phases

The applicability of three different Silphenylene Silicone co-polymer (Si-Arylene) GC stationary phases (J&W Scientific DB-5ms, Varian VF-5ms, and VF-Xms) has been evaluated for the separation of all 136 tetra- through the octa- chlorinated dibenzo-p-dioxins (PCDD) and chlorinated dibenzofurans (PCDF) from closely eluting isomers using gas chromatography/high resolution mass spectrometry (GC/HRMS). Their relative performance data are compared to the “conventional” 5% diphenyl 95% dimethylpolysiloxane GC column (Supelco Equity-5) and to each other based on absolute retention times, visualized mass chromatograms, and the separation of 2,3,7,8-substituted isomers. VF-Xms GC column was able to demonstrate a better performance towards separation of 2,3,7,8-substituted PCDD/PCDF compared to other Si-Arylene GC columns tested, where only 2,3,4,7,8-PnCDF can not be resolved from 1,2,3,6,9-PnCDF and 2,3,4,6,7,8-/1,2,3,6,8,9-HxCDF and 1,2,3,7,8,9-/1,2,3,4,8,9-HxCDF can be at least partially resolved. These data suggest that the development of a single GC column for the separation of all 17 2,3,7,8-substituted dioxins and furans is feasible, which therefore could be used as a standard tool for the PCDD/PCDF methods globally including USEPA methods 1613b, 8290A, 8280B, European Standard Method EN 1948, Canadian methods DFPCB-E3418, EPS 1/RM/19, Japanese methods JIS K0311 and JIS K0312. Having one specific GC column to separate all 2,3,7,8-substituted PCDD/PCDF will significantly improve the data quality, comparability by the various methods and assessment techniques while simultaneously leading to a more cost and time efficient operation.     

微波消解-ICP—MS测定土壤和水系沉积物中的重金属

建立了一种采用逆王水和氢氟酸的混合体系微波酸消解土壤与水系沉积物,电感耦合等离子体质谱法快速测定六种金属元素（As、Cd、Pb、Cu、Cr和Ni）含量的方法。本文研究了消解温度和消解时间对消解效果的影响。结果表明,在190℃下运行25分钟对土壤与水系沉积物中的六种金属元素均具有很好的消解能力,备元素的测定值与标准值相符。在对实际土壤与水系沉积物样品进行分析后得出采样区域的土壤与沉积物中这六种金属含量水平正常。     

电除尘器斜气流状态下粉尘沉降试验研究

针对电除尘器在实际运行过程中出现的除尘效率下降问题,提出斜气流这一新型技术,对均匀气流与斜气流分布状态进行可视化研究;在两种气流状态下进行粉尘沉降试验,对试验结果进行对比分析、总结相应规律;对我国电除尘器气流技术的发展提出了建议。     

氦质谱检漏仪在锅炉检漏中的应用

介绍了一种应用氦质谱检漏仪准确查找锅炉轻微漏点的方法。该检漏方法与一般带压查漏方法相比,具有安全性高、经济性好和操作方便等优点,属检漏技术的创新,为同类锅炉检测提供参考。     

Microwave-assisted stripping of oil contaminated drill cuttings

The application of microwave heating technology to conventional gas stripping processes has been investigated in the remediation of contaminated drill cuttings. The technical feasibility and limitations of nitrogen and steam stripping processes are demonstrated, and it is shown that the combination of microwave heating with the stripping process offers a step change in performance. Order of magnitude improvements in processing time are shown for the microwave-assisted processes, as well as greatly improved levels of remediation. The mechanisms of contaminant removal are discussed, along with the phenomena which occur with microwave heating processes. The energy requirements of each of pure gas and microwave-assisted processes are also discussed, and the potential applications of each technology are highlighted relative to the overall remediation requirements.     

Mass Load-Based Pollution Management of the Han River and Its Tributaries, Korea

Spatio-temporal variations of biochemical oxygen demand (BOD) and total coliform (TC) in the Han River, Korea, were investigated in terms of concentration-based and mass loading-based approaches. Considering the river water quality criteria regulated by the Ministry of Environment in Korea, the tributaries linked to the mainstream of the Han River were found to be highly contaminated with respect to both BOD and TC and, in fact, most of the tributaries exceeded the maximum water quality criteria. To evaluate the pollution impact of tributaries on the mainstream, the monthly water quality monitoring data for six years (from 1995 to 2000) were collected from the Han River basin, and statistically analyzed using Pearson’s correlation coefficient. The results revealed that mass loading-based approach was superior to the concentration-based approach for effective Han River watershed management. Overall results supported that the mass loading-based approach associated with total maximum daily loads (TMDL) management would be a useful and suitable protocol in watershed management for improving the water quality of the Han River and protecting public health. Therefore, this study supporting TMDL management can be applicable to a wide array of contaminants and watershed settings in Korea.     

Crosslinking and stabilization of high fractional free volume polymers for gas separation

Crosslinkable poly(4-methyl-2-pentyne) (PMP) membranes were cast from carbon tetrachloride solutions containing PMP and either 4,4′-diazidobenzophenone or 4,4′-(hexafluoroisopropylidene)diphenyl azide. The composite membranes were transparent and homogeneous and were crosslinked by UV irradiation at room temperature or thermal treatment at 180 °C. Low levels of the bis(aryl azide) (1–4.5 wt%) were effective in rendering the membranes insoluble in cyclohexane and carbon tetrachloride, both are good solvents for PMP, thus PMP can easily be converted to mechanically stable membranes with permeabilities and selectivities comparable or higher than those of the well-known poly(dimethylsiloxane) (PDMS). The permeabilities of O₂, N₂, H₂, CH₄ and CO₂ were measured. Compared to pure PMP, the crosslinked membranes containing bis(aryl azide) had lower permeabilities and higher selectivities, consistent with a reduction in free volume.