Non-chromatographic method for separation and determination of Fe, Ni and V porphyrins in crude oil.

A method combining ultracentrifugation and cloud point extraction is proposed for the separation and determination of Fe, Ni and V porphyrins in crude oil. An emulsion containing about 200 mg of crude oil, 6% (w v-1) of Triton X-100™, 1.6% (v v-1) of chloroform and 0.1 mol L-1 of HCl was prepared. An aliquot (1.5 mL) of this emulsion was ultracentrifuged to separate the crude oil heavy fraction (asphaltene and particulate matter) and inorganic species, organometallic compounds and porphyrins of Fe, Ni and V remained in the supernatant. Another aliquot (1.5 mL) was heated up to 90 °C for 5 min to separate the porphyrins, both heavy and light organics compounds, light organic and particulate matter by cloud point extraction, only the inorganic and ionic organometallic compounds species remained in the aqueous phase. The supernatant and aqueous phase were analysed by simultaneous graphite furnace atomic absorption spectrometry. The concentration determined in the supernatant was subtracted from that determined in the aqueous phase, providing the quantification of Fe, Ni and V porphyrin in the crude sample. The accuracy of the proposed method was checked using SARA reference method. The elemental determinations in the fractions obtained using the proposed method and the comparison by SARA showed an absence of Fe in the aromatics and resins fractions. The results showed that about 40% of Ni and 70% of V in the crude oil sample are bounded to porphyrins.

Fast emulsion-based method for simultaneous determination of Co, Cu, Pb and Se in crude oil, gasoline and diesel by graphite furnace atomic absorption spectrometry.

A method for the simultaneous determination of Co, Cu, Pb and Se in crude oil, gasoline and diesel samples using emulsion-based sampling and GF AAS is proposed. 400mg of sample was weighted in volumetric flask following the sequential addition of 125 µL of hexane and 7.5 mL of Triton X-100(®) (20% mv(-1)). Subsequently, the mixture was stirred in ultrasonic bath, during 30 min, before dilution to 25 mL with deionized water. Aliquots of 20 µL of reference solution or sample emulsion were co-injected into the graphite tube with 10 µL of 2 g L(-1) Pd(NO3)2. The pyrolysis and atomization temperatures were 1300°C and 2250°C, respectively. The limits of detection (n=10, 3σ) and characteristic masses were 0.02 µg g(-1) (0.32 µg L(-1)) and 18 pg for Co, 0.03 µg g(-1) (0.48 µg L(-1)) and 15 pg for Cu, 0.04 µg g(-1) (0.64 µg L(-1)) and 48 pg for Pb, and 0.11 µg g(-1) (1.76 µg L(-1)) and 47 pg for Se. The reliabilities of the proposed method for Co and Se were checked by SRM(®) 1634c Residual Oil analysis. The found values are in accordance to the SRM at 95% confidence level (Student's t-test). Each sample was spiked with 0.18 µg g(-1) of Co, Cu, Pb and Se and the recoveries varied from 92% to 116% for Co, 83% to 117% for Cu, 72% to 117% for Pb, and 82% to 122% for Se.

Unraveling the mysterious role of palladium in Feigl bis(dimethylglyoximate)nickel(II) spot tests by means of confocal Raman microscopy.

The acid protection effect promoted by traces of PdCl(2) in [Ni(dmgH)(2)] spot tests was elucidated from confocal Raman microscopy imaging, which revealed the formation of protecting layers of [Pd(dmgH)(2)] closing the extremities of the [Ni(dmgH)(2)] filaments.

Biomonitoring method for the simultaneous determination of cadmium and lead in whole blood by electrothermal atomic absorption spectrometry for assessment of environmental exposure.

The aim of this work is to propose a biomonitoring method for the simultaneous determination of Cd and Pb in whole blood by simultaneous electrothermal atomic absorption spectrometry for assessment of environmental levels. A volume of 200 microL of whole blood was diluted in 500 microL of 0.2% (wv(-1)) Triton) X-100+2.0% (vv(-1)) HNO3. Trichloroacetic acid was added for protein precipitation and the supernatant analyzed. A mixture of 250 microg W+200 microg Rh as permanent and 2.0% (wv(-1)) NH4H2PO4 as co-injected modifiers were used. Characteristic masses and limits of detections (n=20, 3s) for Cd and Pb were 1.26 and 33 pg and 0.026 microg L(-1) and 0.65 microg L(-1), respectively. Repeatability ranged from 1.8 to 6.8% for Cd and 1.2 to 1.7% for Pb. The trueness of method was checked by the analysis of three Reference Materials: Lyphocheck Whole Blood Metals Control level 1 and Seronorm Trace Elements in Whole Blood levels 1 and 2. The found concentrations presented no statistical differences at the 95% confidence level. Blood samples from 40 volunteers without occupational exposure were analyzed and the concentrations ranged from 0.13 to 0.71 microg L(-1) (0.32+/-0.19 microg L(-1)) for Cd and 9.3 to 56.7 microg L(-1) (25.1+/-10.8 microgL(-1)) for Pb.

Combination of ultrasonic extraction and stripping analysis: an effective and reliable way for the determination of Cu and Pb in lubricating oils.

The determination of metals in lubricating oil has been used as an important way to prevent components failures, to provide environmental information and in some cases, to identify adulteration. In this work, an effective and simple procedure is proposed for Cu and Pb determination in lubricating oils. An ultrasonic bath was employed for extraction of these elements from oil samples in a mixture 1:1 (v/v) of concentrated HCl and H(2)O(2). A very efficient extraction of Cu and Pb (approximately 100%) was attained after 30 min of ultrasound, allowing the simultaneous determination of both metals using square-wave anodic stripping voltammetry at thin-film gold electrodes. The extraction procedure was performed in 4 mL polypropylene closed vessels and dozens of samples could be treated simultaneously in the same ultrasonic bath. The regions of the ultrasonic bath, where the maximum efficiency of extraction was attained were evaluated. Over the optimized region, 30 samples can be treated simultaneously. Used lubricating oils from automotive engines were analyzed by using the optimized extraction procedure.

Iron overload in patients with chronic hepatitis C virus infection: clinical and histological study.

BACKGROUND: Recently it has been found that iron is an important element in the natural history of hepatitis C. Serum markers of iron stores are frequently increased in chronic hepatitis C virus (HCV)-infected carriers but the real impact of the hepatic iron overload is poorly understood. The purpose of the present paper was to determine the prevalence of iron overload and to study the relationship between hepatic iron concentration (HIC) and clinical, biochemical and histological characteristics in chronic HCV-infected carriers. METHODS: Patients presenting with anti-HCV and HCV-RNA were included. Hepatic iron concentration was determined in liver tissue by atomic absorption spectrophotometry. The association between HIC and age, gender, risk factor of transmission, duration of infection, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, iron and serum ferritin, transferrin saturation, HCV-RNA level, grading of inflammatory activity, staging of fibrosis, hepatic steatosis, and stainable iron was analyzed. Statistical analysis included the Mann-Whitney test and a multiple linear regression model. RESULTS: Ninety-six patients (58% male) with a mean age of 44 +/- 10 years were studied. Serum iron, ferritin and transferrin saturation were elevated in 28%, 27% and 12.5% of patients, respectively. Stainable iron was detected in few patients (15.6%). Higher grades of stainable iron (2 and 3) were observed in only 7%. The HIC (>30 mmol/g dry weight) was elevated in five patients (5%). Neither grading nor staging were related to HIC. Higher HIC were observed in male patients (P < 0.001), in patients with elevated serum ferritin (P = 0.001) and in patients with stainable iron (grades 2 and 3; P = 0.001). Multiple linear regression analysis showed that only stainable iron was independently correlated with HIC (P = 0.003). CONCLUSIONS: Iron overload in chronically HCV-infected patients was uncommon and hepatic iron content seemed not to be related to the liver damage process. In the eventuality of iron overload, histochemical liver iron is a useful marker to estimate HIC.

Multielement determination of cadmium and lead in urine by simultaneous electrothermal atomic absorption spectrometry with an end-capped graphite tube.

A method for the multielement determination of cadmium and lead in urine is proposed by simultaneous electrothermal atomic absorption spectrometry (SIMAAS) with an end-capped transversely heated graphite atomizer (EC-THGA). The best conditions for cadmium and lead determination were obtained in the presence of NH4H2PO4 as a chemical modifier, using 500 degrees C and 1800 degrees C as the pyrolysis and atomization temperatures, respectively. Urine samples were diluted 1 + 4 directly in autosampler cups with a mixture of 0.125% (w/v) Triton X-100 + 2.5% (v/v) HNO3 + 0.31% (w/v) NH4H2PO4. The optimized heating program was carried out in 57 s, and the instrument calibration was done with aqueous reference solutions. The use of EC-THGA increased the sensitivity of cadmium and lead by 14% and 25%, respectively. The detection limits (n = 20, 3delta) were 0.03 microg L(-1) (0.36 pg) for cadmium and 0.57 microg L(-1) (6.8 pg) for lead. The performance of EC-THGA was acceptable up to 500 heating cycles. The reliability of the entire procedure was checked with the analysis of a lyophilized urine certified reference material. The found concentrations were in agreement with the recommended values (95% confidence level).