Dechlorination of PCB contaminated transformer oils by extraction with acetone

Neutron activation analysis was used to study the dechlorination of transformer oils containing 2000 ppm of polychlorinated biphenyls by solvent extraction with acetone. The distribution coefficients of PCBs between acetone and oil have been measured and they vary from 1.25 to 1.45. The concentration of PCBs in the oil can be reduced from 2000 ppm to less than 25 ppm in five extraction cycles.     

Comparison of methods for the gas-chromatographic determination of PCB congeners and chlorinated pesticides in marine reference materials

Summary Three gas-chromatographic (GC) columns with different selectivity (DB-5, DB-1701, and C-18) and two different GC detectors (electron-capture and mass-spectrometric) were used to analyze three Standard Reference Materials (SRMs), which are available from the National Institute of Standards and Technology (NIST), and two Certified Reference Materials (CRMs), which are available from the Community Bureau of Reference (BCR), for polychlorinated biphenyl (PCB) congeners and chlorinated pesticides. The materials analyzed were: SRM 1588, Organics in Cod Liver Oil; SRM 1941, Organics in Marine Sediment; SRM 1974, Organics in Mussel Tissue (Mytilus edulis); CRM 349, Chlorobiphenyls in Cod Liver Oil; and CRM 350, Chlorobiphenyls in Mackerel Oil. Results from these different methods are compared, and concentrations for additional PCB congeners and chlorinated pesticides in these reference materials, which have not been measured previously, are reported.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Comparison of methods for the determination of fluorine in plants

Summary The determination of fluorine in plant material has been carried out by potentiometry using an ion-specific electrode. The decomposition of the material has been performed by the oxygen flask combustion, by NaOH fusion or by leaching with nitric acid. Both the first mentioned procedures are accurate and show the same precision, the first one being less time-consuming. Other methods have been found to be unnecessarily complicated.

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Vergleich von Methoden zur Fluorbestimmung in Pflanzen

Zusammenfassung Die Bestimmung wurde potentiometrisch mit Hilfe einer ionenspezifischen Elektrode durchgeführt. Der Aufschluß erfolgte durch Verbrennung im Sauerstoffkolben, Schmelze mit NaOH oder Auslaugen mit Salpetersäure. Die beiden erstgenannten Verfahren erwiesen sich als die genauesten und zeigten gleiche Reproduzierbarkeit, wobei die Verbrennung im Sauerstoffkolben weniger zeitaufwendig ist. Andere Methoden sind unnötig kompliziert.

     

Comparison of methods for the determination of vanadium in sea-water

Procedures for the determination of vanadium in sea-water have been independently developed at two laboratories. The separation and concentration steps were distinctly different and quantification was by neutron activation or atomic absorption. Both methods provide a reliable measurement of vanadium concentration at natural levels in sea-water.     

Comparison of activation methods for mercury determination

A comparative study is made on different activation methods for mercury analysis. Mercury concentrations down to 0.1 ppm were determined instrumentally via the isotopes¹⁹⁷Hg (T=65 h) and²⁰³Hg (T=47 d). A high-resolution Ge(Li) detector was used in measuring the activity and a small computer for data reduction. Up to 500 samples were measured daily. Chemical separations were performed on samples with low mercury concentrations. Sensitivity of 0.01 ppm was attained by precipitating HgS from basic solutions and counting¹⁹⁷Hg on NaI(T1) detector. A new rapid instrumental method was also developed based on^199mHg (T=43 min). This short-lived isotope was activated with resonance neutrons. The sensitivity of the method is 0.5 μg and it requires only 1 hr.     

Comparison of four extraction methods for the analysis of pharmaceuticals in wastewater

As one category of the most urgent emerging pollutants, pharmaceuticals have provoked much public and scientific attention due to widespread contamination in aquatic environment. In this study, two active methods by Oasis HLB and MCX and two passive methods by XAD-16 and XAD-16/7 were evaluated for determining the concentrations of 10 pharmaceuticals (carbamazepine, clofibric acid, diclofenac, gemfibrozil, ibuprofen, ketoprofen, naproxen, paracetomol, terbutaline and triclosan) in reclaimed wastewater. Recoveries of the target pharmaceuticals extracted by MCX were higher than HLB except for diclofenac and ketoprofen. For the passive methods, the addition of polar resin XAD-7 improved the recovery compared with the addition of XAD-16 only. The mean recoveries of the target analytes by XAD-16/7 ranged from 22 to 75.8%. The limit of quantification (LOQ) ranged between 25 and 280 ng/L. In addition, by comparing the accuracy and precision of XAD-16/7 method and MCX method, we further demonstrated that the XAD-16/7 method can be satisfactorily used for the analysis of pharmaceuticals in wastewater samples. We applied the method to some wastewater samples from sewage treatment plant (STP) nearby Riverside, CA to track the concentration change of pharmaceuticals in the treatment processes. The result shown that pharmaceuticals were effective reduced in STP mostly by activated sludge.     

An evaluation of four titrimetric methods for the determination of lead in ores

Four titrimetric methods for the determination of lead in ores were evaluated. In the absence of bismuth and indium, a method based on EDTA titration of lead, after chloroform extraction of lead diethyldithiocarbamate, yields accurate and more precise results than the other methods evaluated. Interference from indium can be avoided by di-isopropyl ether extraction of its bromide from 6M hydrobromic acid. Interference from bismuth can be eliminated by separating it from lead by chloroform extraction of its xanthate from 2M hydrochloric acid-tartaric acid media.     

Comparison of methods for the determination of ochratoxin A in wine

Different analytical methods for the determination of ochratoxin A (OTA) in wine have been compared. Sample clean-up was based on solid-phase extraction (SPE) with (i) immunoaffinity or (ii) RP-18 sorbent materials applying different experimental protocols. The detection of OTA was accomplished with high-performance liquid chromatography (HPLC) combined either with electrospray ionisation (ESI) tandem mass spectrometry (MS-MS) or fluorescence detection (FL). Comparative method evaluation was based on the investigation of 18 naturally contaminated red wine samples originating from different European countries. The analytical results are discussed in view of the respective method validation data and the corresponding experimental protocols. In general, analytical data obtained with RP-18 SPE combined with LC-MS-MS detection and immunoaffinity extraction combined with FL offered comparable good results in the sub-ppb concentration level indicating that high selectivity of either the sample clean-up or, alternatively the detection system are equally well-suited to guarantee an accurate OTA analysis in wine.     

Comparison of four chromogenic reagents for the flow-injection determination of aluminum in water

Pyrocatechol violet (PCV), aluminon, eriochrome cyanine R (ECR) and eriochrome cyanine R with cetyltrimethylammonium bromide (ECR/CTA) are compared as chromogenic reagents for the flow-injection determination of aluminium in water. The detection limit of the ECR/CTA method is 1 μg Al 1^?1. The detection limits of the PCV and ECR methods are 5 μg Al 1^?1. The aluminon method is the least sensitive, with a detection limit of 50 μg Al l^?1. Interference from iron, fluoride, phosphate and the acidity of the sample were investigated. The interference from iron is suppressed by hydroxylammonium chloride/1,10-phenanthroline in the PCV and ECR/CTA methods at concentrations less than 5 mg Fe l^?1. In the ECR and aluminon methods, iron <5 mg l^?1) is masked by ascorbic acid. Fluoride at <0.2 mg l^?1 can be tolerated in all methods. The aluminon method can tolerate up to about 500 mg l^?1 in the three other methods. All methods are sensitive to changes in acidity of the samples; the acidity should be 0.08–0.12 M HCl.     

Comparison of four microwave digestion methods for the determination of selenium in fish tissue by using hydride generation atomic absorption spectrometry

Four microwave digestion methods of fish tissue for selenium determination by hydride generation atomic absorption spectrometry were compared, in which potassium hexacyanoferrate(III) was chosen as a masking agent for eliminating matrix interferences. The results showed that the methods employing HNO(3)/H(2)O(2), HNO(3)/K(2)S(2)O(8)/H(2)O(2) and HNO(3)/H(3)PO(4)/H(2)O(2) digestion media were unreliable. However, the decomposition using the digestion media of HNO(3)/H(2)SO(4)/H(2)O(2) enabled adequate digestion of fish tissue and retention of selenium in a state amenable for determination. Therefore, the digestion procedures with HNO(3)/H(2)SO(4)/H(2)O(2) media are proposed for the determination of selenium in fish tissue by hydride generation atomic absorption spectrometry. The recoveries of the spiked samples investigated ranged from 90 to 102%. The result obtained from analyzing the NIES CRM No. 6 mussel was in good agreement with the reference value (reference value: 1.5 mug/g; found: 1.45 +/- 0.05 mug/g). The limit of detection for selenium was 0.03 mug/g dry mass for a 100 mg sample. The contents of selenium in local fish species investigated ranged from 0.49 to 2.90 mug/g, and the relative standard deviation for the determination of selenium was less than 8%.     

Comparison of three colorimetric methods for the determination of manganese in freshwaters

Three calorimetric methods for the determination of manganese in freshwaters have been investigated and compared with the atomic-absorption spectrometry (AAS) method. Two of the methods, viz. the formaldoxime (FAD) and pyridylazonaphthol (PAN) methods were found to yield poor calibration curves upon standardization, and to have high average errors for the estimation of manganese concentrations in standard solutions. The FAD method, when applied to freshwater samples, was found to be subject to an interfering UV absorbance which could not be negated successfully by a reagent blank; the method thus tended to give high estimations at low concentrations of manganese, but the results obtained also appear to be very sensitive to the nature of the freshwater matrix. On the other hand the PAN method was found to give very high estimations for the concentration of manganese, in both standard solutions and in freshwater samples, owing to the nature of the absorbance of the ligand used for manganese determination. This method also appears to be affected by the freshwater matrix, leading to gross overestimation of manganese levels. A third method, based on a porphyrin ligand [T-(4-CP)P], was found to give results comparable with those of the AAS method in estimating the soluble manganese content in freshwaters.     

Interlaboratory comparisons and improvements of methods for acid number determination in used motor oils

The results of two interlaboratory comparisons of acid number determinations in used motor oils are discussed. It is shown that the comparability of the measurement results is not as good as that required by known standards for petroleum products. The problem is motor oil contaminants which accumulated during use, and which are the source of a matrix effect in the acid number determination. The standard methods’ drawbacks are analyzed and some improvements are proposed. Repeatability and accuracy of the improved methods are evaluated. Received: 11 December 2001 Accepted: 15 February 2002     

Comparison of four digestion methods for the determination of selenium in bovine liver by hydride generation and atomic-absorption spectrometry in a flow system

A flow system for hydride generation and atomic-absorption spectrometry is described, and the results from the optimization of the equipment for selenium determination are reported. For a sample volume of 0.6 ml the limit of detection for selenium was 0.1 mug l . and the imprecision less than 1% RSD at the 10-mug l . level. Four digestion procedures for selenium in bovine liver have been tested. All procedures gave concordant results, provided that the standard-additions method was used. The accuracies of the overall analytical procedures were estimated by comparison with results from neutron-activation analysis and analysis of NBS Bovine Liver, No. 1577. These comparisons proved that the accuracies of the procedures described in this paper are good.     

Trends in bioanalytical methods for the determination and quantification of club drugs: 2000-2010

The term 'club drug' can be loosely defined as any substance used to enhance social settings. Such drugs are commonly found at raves or similar all-night dance parties and include methamphetamine, 3,4-methylenedioxymethamphetamine, gamma-hydroxybutyrate (GHB), ketamine (KET), and flunitrazepam (FLU). These drugs have potentially dangerous side effects including hallucinations, paranoia, amnesia and hyperthermia. In addition, GHB, KET and FLU are considered predatory drugs due to their roles in drug-facilitated sexual assault. Forensic and regulatory agencies routinely have the need for determination and accurate quantification of these drugs in biological fluids, especially in cases of mortality or criminal investigations. This review presents the chromatographic and spectroscopic methods published for such analyses over the last decade, including sample preparation techniques and validation data.     

葡萄籽提取物中原花青素含量不同测定方法比较

原花青素是从植物中分离得到的一类黄烷醇单体及其聚合体的多酚类化合物 ,前者为黄烷 4 醇或黄烷 3,4 二醇 ,后者则为缩合单宁、红粉和酚酸 ,如下图所示。该类化合物具有生物活性 ,如抗氧化和自由基清除能力等[1] ,而机体内脂质氧化和自由基的产生是引发肿瘤等多种疾病的主要原因。国外以葡萄籽提取物中原花青素作为主要活性成分的药品及食品营养补充剂较多 ,国内也有多家企业正着手该类产品的研发与生产。目前 ,关于原花青素含量的测定方法尚无统一标准 ,相关文献报道也较少。本文对葡萄籽提取物中原花青素含量测定的三种不同方法进行了对…     

Comparative methods in the determination of wax content and pour points of crude oils

In this research, differential scanning calorimetry (DSC) and gas chromatography is used to determine the wax content of fourteen crude oils of different sources. Different empirical equations were applied to compare the wax content of crude oils. For the fourteen crude oil samples with the wax content ranging from 7.5 to 43.8 mass%, it was observed that the results of empirical equations were in good agreement with those determined by DSC and GC. Accordingly, a correlation between ASTM pour point and the temperature at which 2 mass% of wax has precipitated out from crude oil is developed.     

Two green chromatographic methods for the quantification of tamsulosin and solifenacin along with four of their impurities

Modern analytical procedures often include impurity profiling to verify the potency, safety, and effectiveness of new formulations. We had to develop techniques based on green analysis since the detrimental influence of solvents and chemicals on the environment has now become a serious concern. Two selective, sensitive, and green liquid chromatography methods were established and fully validated for quantitation of tamsulosin hydrochloride and solifenacin succinate along with four of their official and/or related impurities namely; tamsulosin sulfonic acid, tamsulosin impurity H, solifenacin impurity A and solifenacin impurity C. The first used high-performance thin-layer chromatography with silica gel 60 F254 plates as the stationary phase and an elution system of ethyl acetate:butanol:glacial acetic acid (10.0:0.4:0.1, by volume) and a scanning wavelength of 225.0 nm. The second method depended on HPLC with diode array detection. Chromatographic separation was accomplished on a Zorbax SB C₁₈ (250 × 4.6 mm², 5 μm) column utilizing a mixture of 10.0 mM sodium dihydrogen phosphate (pH 3.0, adjusted by o-phosphoric acid) and methanol, at a flow rate of 0.8 mL/min in a gradient elution mode and then the separated peaks were scanned at a wavelength of 225.0 nm. To assess the greenness profile, three distinct methodologies were applied.