Kamal Swami

Determination of trace metals in atmospheric aerosols with a heavy matrix of cellulose by microwave digestion-inductively coupled plasma mass spectroscopy

Abstract A microwave digestion method followed by inductively coupled plasma mass spectrometric (ICP-MS) analysis was developed to determine trace metal concentrations in atmospheric aerosol samples with a heavy matrix of cellulose material. A combination of HF–HNO 3 –H 2 O 2 –H 3 BO 3 was used for digestion. The background spectral features contributed by the matrix elements were studied. In particular, spectral and non-spectral interference caused by B and F were investigated. Detection limits of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb and Pb were determined in the presence of various amounts of matrix elements. In general, the detection limits of most elements degraded with an increase in B and F. Vanadium (V) suffered most due to severe spectral interference from 11 B 40 Ar + and/or 19 F 16 O 16 O. The concentrations of elements in filter paper matrix blanks were measured. An NIST standard (urban particulate matter, 1648), as well as real world atmospheric aerosol samples from Whiteface Mountain, NY, and from Mayville, NY were pressed into pellets with a great amount of cellulose filter material and digested, and the concentrations of trace metals were determined. For the NIST standard, the recoveries of V, Mn, Fe, Co, Ni, Cu, Zn, Cd, As, Sb and Pb were over 90%, while 77 and 70% for Cr and Se, respectively. For the atmospheric aerosol samples from Whiteface Mountain and Mayville, NY, only the values of Fe, Se, As, Sb and Zn could be compared with those obtained through instrumental neutron activation analysis, and the agreement was within ±10%.

Trends in atmospheric elemental carbon concentrations from 1835 to 2005

225, and 62 ng m � 3 , respectively. We also collected � 55 cm long sediment cores from West Pine Pond near Whiteface Mountain. The cores were sliced and their 210 Pb ages determined. The first (top) five slices each represented sediment deposition over 7 years and the remaining 13 years each. EC was chemically separated from the sediment samples from four cores, and its concentration in each slice was determined using the thermal optical method. The [EC]sed followed closely that of [EC]atm from 1978 to 2005. Assuming wet and dry deposition as the only source, we can show that [EC]sed = K[EC]atm, where K (m 3 g � 1 ) is a constant for a given lake. From [EC]atm, and [EC]sed for the 1978–2005 period, K was determined to be 10,400 ± 4,400 m 3 g � 1 . With this value used for K and [EC]sed, the [EC]atm values were determined from 1835 to 1978. The [EC]atm from 1835–1862 was � 30 ng m � 3 , which may be close to the preindustrial background level. The [EC]atm was 65 ng m � 3 for the 1863–1875 period, then increased sharply, reaching a maximum value, 760 ng m � 3 , from 1917–1930. From 1931–1943 through 1978–1984, the concentration decreased gradually, from 680 to 560 ng m � 3 . The concentrations for 1985–1991, 1992–1998, and 1999–2005 were 295, 195, and 60 ng m � 3 , respectively. Model calculations for BC emissions from fossil fuel

Trace Metals Analysis of Legal and Counterfeit Cigarette Tobacco Samples Using Inductively Coupled Plasma Mass Spectrometry and Cold Vapor Atomic Absorption Spectrometry

ABSTRACT A closed-vessel microwave-digestion method was developed for the determination of trace amounts of Be, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, Tl, and Pb by inductively coupled plasma mass spectrometry and Hg by cold-vapor atomic absorption spectrometry in cigarette tobacco samples. In order to gauge the effectiveness of the digestion procedure, recovery studies were conducted using solutions prepared from National Institute of Standards and Technology Standard Reference Material 1573a Trace Elements in Tomato Leaves and Polish Certified Reference Material Virginia Tobacco Leaves. Limits of detection were below 1 µg g−1 for all elements studied. Samples from two genuine-brand and three counterfeit packs were analyzed. The mean amounts of Be, As, Mo, Cd, Sb, Tl, Pb, and Hg were higher in counterfeit cigarettes, while the amounts of V, Cr, Mn, Co, Cu, Zn, Se, and Ba were comparable among legal and counterfeit cigarettes; the amount of Ni was higher in the legal cigarettes. Evaluation of Be, As, Mo, Cd, Sb, Tl, Pb, and Hg with their potential hazards for smokers is briefly discussed.

Mercury impairment of mouse thymocyte survival in vitro: involvement of cellular thiols.

Heavy metals are well known to be able to induce immunotoxicity, but comparative metal studies related to apoptosis have not been conducted. In the present study, the effects of arsenic, cadmium, gold, lead, manganese, and mercury on thymocytes from BALB/c mice were analyzed. Thymic cells were cultured for 3–24 h in vitro in the absence or presence of metal, and markers of apoptosis or cell death, including annexin V binding, DNA loss/oligonucleosomal fragmentation, 7-amino-actinomycin D uptake (loss of impermeance), changes of the mitochondrial membrane potential (JC-1 fluorescence), and Western analysis of cellular thiols, were assayed. Mercury (Hg) was the only metal shown to be consistently toxic with the dose and times utilized. Cadmium (Cd) was the only other metal tested that also produced some significant level of DNA loss; however, the induction of apoptosis by Cd was not as consistent as that observed with Hg. When Hg was added with 2-mercaptoethanol (2-ME), Hg produced greater toxicity. Endogenous DNA synthesis by thymocytes was immediately inhibited by Hg and Hg + 2-ME. The Hg + 2-ME-induced apoptosis appeared to be associated with altered levels of cellular thiols, in that glutathione (GSH) depletion was significant in comparison to the non-metal control and Hg alone. The increased Hg-induced toxicity in the presence of 2-ME likely was due to the ability of 2-ME to enhance (10- to 20-fold) the cellular uptake of Hg. Western analysis with biotin maleimide demonstrated that Hg + 2-ME and to a lesser extent the positive control dexamethasone eliminated many reactive thiols; the major thiol-reactive protein still reactive with the maleimide probe had an approximate Molecular Mass of 45 kD. Surprisingly, Hg alone enhanced the expression of this thiol-expressing protein, which by Mass Spectrometry (MS)/MS analysis was shown to be β-actin. Hg also produced the appearance of yet to be identified new proteins. Based on the results with Hg + 2-ME, it is suggested that numerous protein thiols participate in maintenance of cell survival and their loss is associated with apoptosis. The increased expression of new thiol-reactive proteins or thiol-reactive proteins with altered electrophoretic profiles needs to be further investigated. However, the enhanced toxicity attributed to Hg + 2-ME suggests that increased intracellular oxidative stress, observed as increased depletion of GSH, is responsible for the accelerated cell death. This work was supported by National Institutes of Health grant ES11135. The authors acknowledge use of the Immunology and Biological Mass Spectrometry Facilities of Wadsworth Center. We also especially appreciate the assistance of Kathy Lubowski, Joan Pedersen-Lane, and Renjie Song.

Pyrolysis and combustion of liquids and solids containing pentachlorophenol

The effect of concentration, residence time, and matrix on the formation of PCDDs/PCDFs from the combustion of pentachlorophenol in the presence of a flame and from its pyrolysis at atmospheric pressure was studied.

ICP-MS determination of lead isotope ratios in legal and counterfeit cigarette tobacco samples

A method for the determination of Pb isotope ratios (IR) in cigarette tobacco by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) has been developed and applied to tobacco samples from genuine and counterfeit cigarettes obtained in the USA. The IR 207Pb/206Pb, 208Pb/206Pb, 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb were measured using a Q-ICP-MS instrument. Two certified reference materials, grown in the USA and Bulgaria, were also analysed for comparison with the tobacco samples, as were tobacco samples from cigarettes obtained in Pakistan and China. The precision of the results was sufficient to distinguish between the counterfeit and genuine USA cigarettes. All of the genuine cigarettes and both reference materials, grown in different regions, were statistically distinct based on the measured ratios. The counterfeit cigarettes were indistinguishable from the reference material grown in Bulgaria. The technique shows promise as a method for identifying counterfeit cigarettes, possibly determining the source region.

Thermally induced formation of PCDD and PCDF from tri- and tetrachlorobenzene in dielectric fluids

Abstract The thermal behavior of dilute (5000-50 ppm) solutions of tri- and tetrachlorobenzene in mineral oil, silicone oil, and tetrachloroethylene (TCE) has been investigated. Although pyrolyses or combustion of neat chlorobenzenes readily forms significant yields of PCDDs/PCDFs, corresponding treatment of dilute solutions was generally non-productive. This result is consistent with the proposition that, under the conditions studied, the rate-limiting step for PCDD/PCDF formation is bimolecular in chlorobenzene. In contrast, earlier studies of PCBs implied a rate-limiting step that was unimolecular in chloroaromatics. Combustion of dilute solutions of chlorobenzenes in tetrachloroethylene did produce detectable concentrations of PCDF; this result reflects combination of chlorobenzene and TCE- or TCE-derived species.

Thermally-induced formation of polychlorinated dibenzofurans from Aroclor 1254 contaminated silicone oil and tetrachloroethylene

Abstract Pyrolysis of solutions of Aroclor 1254 at atmospheric pressure and its combustion in the presence of a flame in a tubular flow furnace was carried out. The effect of temperature and residence time on the formation of PCDFs in two different solvent matrices was investigated.

Sensitive Measurement of Se and Te in Cloud Water and Ambient Particulate Matter

ABSTRACT Analytical methods have been developed to measure low levels of trace elements (Te and Se) in cloud droplets and aerosol particulates. For water collected from cloud droplets, pneumatic nebulization coupled with inductively coupled plasma mass spectrometry yielded sufficient sensitivity to allow measurement of Se and Te after a 20-fold hotplate preconcentration. In cloud water samples collected on July 23, 1995, at Whiteface Mountain, New York, USA, Se and Te concentrations appeared to track one another, suggesting that Te could become a viable tracer element given that Se is already a proven tracer in the study of oxidation of SO2 into . For aerosol filter samples, a microwave digestion scheme was developed to dissolve the sample, resulting in highly diluted Se and Te concentrations, too low to be measured by pneumatic nebulization inductively coupled plasma mass spectrometry Hydride generation inductively coupled plasma mass spectrometry was used to improve the detection limits of Se and Te by a factor of 30. It enabled the detection of Se and Te in the low ng/L range in aqueous solution, or in the pg/m3 range in aerosol samples. An aerosol particulate standard (SRM1648, Urban Particulate Matter; NIST) and a sediment standard (GSD11; Institute of Geophysical and Geochemical Prospecting of China) were digested and analyzed to validate the methods.