Azam Mukhtar

Recent developments in assessment of bio-accessible trace metal fractions in airborne particulate matter: A review

In the last years a great deal of research has been focused on the determination of harmful trace metals such as Cd, Co, Cr, Cu, Ni or Pb in airborne particulate matter (APM). However, the commonly applied determination of total element concentrations in APM provides only an upper-end estimate of potential metal toxicity. For improved risk assessment it is important to determine bio-accessible concentrations instead of total metal contents. The present review gives an overview of analytical procedures reported for measurement of bio-accessible trace metal fractions in APM. The different approaches developed for extraction of soluble trace metals in APM are summarized. Furthermore the analytical techniques applied for accurate determination of dissolved trace metals in the presence of complex sample matrix are presented. Finally a compilation of published results for bio-accessible trace metals in APM is included.

Aerosol size distribution and mass concentration measurements in various cities of Pakistan

During March and April 2010 aerosol inventories from four large cities in Pakistan were assessed in terms of particle size distributions (N), mass (M) concentrations, and particulate matter (PM) concentrations. These M and PM concentrations were obtained for Karachi, Lahore, Rawalpindi, and Peshawar from N concentrations using a native algorithm based on the Grimm model 1.109 dust monitor. The results have confirmed high N, M and PM concentrations in all four cities. They also revealed major contributions to the aerosol concentrations from the re-suspension of road dust, from sea salt aerosols, and from vehicular and industrial emissions. During the study period the 24 hour average PM(10) concentrations for three sites in Karachi were found to be 461 μg m(-3), 270 μg m(-3), and 88 μg m(-3), while the average values for Lahore, Rawalpindi and Peshawar were 198 μg m(-3), 448 μg m(-3), and 540 μg m(-3), respectively. The corresponding 24 hour average PM(2.5) concentrations were 185 μg m(-3), 151 μg m(-3), and 60 μg m(-3) for the three sites in Karachi, and 91 μg m(-3), 140 μg m(-3), and 160 μg m(-3) for Lahore, Rawalpindi and Peshawar, respectively. The low PM(2.5)/PM(10) ratios revealed a high proportion of coarser particles, which are likely to have originated from (a) traffic, (b) other combustion sources, and (c) the re-suspension of road dust. Our calculated 24 hour averaged PM(10) and PM(2.5) concentrations at all sampling points were between 2 and 10 times higher than the maximum PM concentrations recommended by the WHO guidelines. The aerosol samples collected were analyzed for crustal elements (Al, Fe, Si, Mg, Ca) and trace elements (B, Ba, Cr, Cu, K, Na, Mn, Ni, P, Pb, S, Sr, Cd, Ti, Zn and Zr). The averaged concentrations for crustal elements ranged from 1.02 ± 0.76 μg m(-3) for Si at the Sea View location in Karachi to 74.96 ± 7.39 μg m(-3) for Ca in Rawalpindi, and averaged concentrations for trace elements varied from 7.0 ± 0.75 ng m(-3) for B from the SUPARCO location in Karachi to 17.84 ± 0.30 μg m(-3) for Na at the M. A. Jinnah Road location, also in Karachi.

Determination of water soluble trace metals in airborne particulate matter using a dynamic extraction procedure with on-line inductively coupled plasma optical emission spectrometric detection

A novel continuous-flow system for the dynamic extraction of water soluble metal fractions in airborne particulate matter (APM) with subsequent inductively coupled plasma optical emission spectrometric (ICP-OES) analysis of derived extracts is presented. The fully automated extraction system with on-line multi-element detection offers enhanced sensitivity when compared to batch-wise counterparts; additionally it provides information about the extraction process. With the developed procedure detection limits in the order of 1.5 (Ba) to 8.0 (Ni) ng extractable mass per investigated sample could be achieved, which translates to method detection limits for soluble metal concentrations in APM ranging from 0.2 ng m(-3) (Ba) to 0.9 ng m(-3) (Fe). Reproducibility of analysis was determined by replicate measurement (n=6) of an APM sample with an aerodynamic diameter ≤10 μm (PM10), derived results varied between 3.5% (Mn) and 12.1% (Ni) relative standard deviation. Method validation was accomplished by comparison of extracted soluble and remaining non-soluble fractions with the total metal contents of the investigated PM10 samples, showing an excellent mass balance for all elements. Application of the developed procedure for the analysis of water soluble metal fractions in PM10 samples (n=16) from Linz (Austria) indicated a high variability of extractable fractions ranging from 11.7±7.2% (Fe) to 48.8±15.4% (Mn) of the total metal contents.

On-line determination of water-soluble zinc in airborne particulate matter using a dynamic extraction procedure coupled to flame atomic absorption spectrometry

In this work a flow injection procedure with FAAS detection for the on-line determination of water-soluble Zn in airborne particulate matter samples is presented. The method is based on a preliminary extraction of samples with water under dynamic conditions and the subsequent on-line FAAS measurement of the dissolved fraction of Zn. As compared to traditional batch-wise systems, the developed on-line extraction procedure offers enhanced sensitivity and sample throughput, reduced risk of sample contamination and the absence of metal redistribution or readsorption processes. With the use of two filter punches (diameter 9 mm) for analysis an instrumental detection limit of 2 ng Zn was obtained, which translates to a method detection limit of approximately 0.4 ng m−3 when considering the volumes of air collected per investigated aerosol sample. The reproducibility of analysis given as the relative standard deviation was 2.6% (n = 6). The procedure was applied for analysis of water-soluble Zn in aerosol samples from two urban sites in Austria. Accuracy of derived results was confirmed by analysis of the same sample set with a traditional batch-wise extraction approach as well as mass balance determination.

Development of an ETV-ICP-OES procedure for assessment of bio-accessible trace metal fractions in airborne particulate matter

The present study describes an ETV-ICP-OES procedure for determination of bio-accessible fractions of Ba, Co, Cu, Mn, Ni and Pb in airborne particulate matter. The method is based on the preliminary extraction of trace metals with synthetic gastric juice using a physiologically based extraction test and the subsequent measurement of gastric extracts with ETV-ICP-OES. Signal quantification was based on external calibration with aqueous standard solutions using In as internal standard. The limits of detection (LOD) calculated as three times the standard deviation (3σ) of the signal derived from filter blank samples ranged from 1.8 ng (Mn) to 12.2 ng (Cu) for analyzed aliquots of 40 μl sample extracts which translates to a method detection limit of 0.11 ng m−3 (Mn) to 0.75 ng m−3 (Cu). The reproducibility of analysis is given as the relative standard deviation varied from 1.9% (Cu) to 5.7% (Ni). Compared to conventional ICP-OES measurement of sample extracts, the developed ETV-ICP-OES procedure was found to offer enhanced sensitivity. The accuracy of the developed method was assessed by analysis of the same sample set with the conventional ICP-OES procedure using liquid sample introduction as well as by comparison of total metal contents and the cumulated sum of extractable metal contents and those remaining after sample extraction, showing good recoveries for all investigated elements. Finally the developed procedure was applied for determination of bio-accessible trace metal fractions in PM10 samples collected from Graz-Sud (Austria) indicating that mean bio-accessible metal fractions varied between 32 ± 14% (Ni) and 97 ± 36% (Pb).

A new approach for the determination of silicon in airborne particulate matter using electrothermal atomic absorption spectrometry

In this work a new procedure for element specific analysis of silicon in airborne particulate matter is presented. The method is based on a preliminary treatment of the aerosol samples with nitric acid and perchloric acid leading to a mineralization of the organic sampling substrate, dissolution of soluble material and a homogeneous suspension of the remaining non-soluble sample fraction. ETAAS measurement of the derived slurries was performed using a Zr-treated graphite tube which prevents the formation of stable silicon carbide during sample measurement. Losses of volatile silicon species during sample pyrolysis were overcome by using Co(II) as matrix modifier and a pyrolysis temperature of only 300 degrees C. Furthermore this low pyrolysis temperature prevents charring of organic material which enables accurate ETAAS analysis. The method including the developed pretreatment procedure was evaluated using the Standard reference material 2709 (San Joaquin Soil) from NIST (National Institute of Standards and Technology, Gaithersburg, MD, USA). Suitability for measurement of Si in airborne particulate matter with an aerodynamic diameter < or = 10 microm (PM10) was demonstrated by the analysis of selected aerosol samples and comparison of derived results with the findings obtained for the same samples after microwave digestion and subsequent ETAAS measurement. Finally the developed procedure was applied for the analysis of silicon in PM10 collected at an urban site in Vienna (Austria). Matrix matched calibration has been used for quantification of derived absorption signals. With the use of 20 microL sample injection volume for ETAAS analysis an instrumental detection limit of 52.2 microg L(-1) was obtained, which translates to method detection limits of approximately 0.52 microg m(-3) when considering the volumes of air collected per investigated aerosol sample. The reproducibility of analysis given as the relative standard deviation was 4.4% (n=12). Derived concentrations for Si in PM10 varied between 0.8 and 7.2 microg m(-3) which is in good accordance with the literature findings.

2-(2-Iodo-benzenesulfonamido)acetic acid.

The title compound, C8H8INO4S, is a halogenated sulfonamide, a medicinally important class of organic compounds. In the crystal structure, intermolecular O—H⋯O hydrogen bonds involving the carboxylic acid groups form characteristic centrosymmetric dimers. These dimers are further linked through centrosymmetric dimeric N—H⋯O interactions involving the amido H atom and a sulfonyl O atom. This leads to the formation of a ribbon-like polymer structure propagating in the b direction.

A new approach for determination of crustal and trace elements in airborne particulate matter

An ICP-OES procedure was developed for fast and accurate determination of various crustal (Al, Ca, Fe, Mg, Si) and trace elements (Ba, Cu, Mn, Na, K, Sr, Ti, Zn) in airborne particulate matter. The method is based on a preliminary treatment of the aerosol samples with a mixture of nitric acid and hydrogen peroxide at elevated temperature leading to a mineralization of the organic sampling substrate, dissolution of soluble material and homogeneous suspension of the remaining non-soluble fraction. After dilution the derived slurry solutions were measured using ICP-OES. The reproducibility of analysis given as the relative standard deviation (% RSD) varied between 3.2 and 6.8% for bulk constituents such as Al, Ca, Fe, Mg and Si whereas values ranging from 3.5 to 9.1% were obtained for trace metals present with distinctly lower abundance in PM10 (e.g. Ba, Cu, Mn, Sr, Zn). The limits of detection (LOD) calculated as three times the standard deviation (3σ) of the signal derived from filter blank samples ranged from approximately 1 ng m−3 (Sr) to 71 ng m−3(Ca). The developed procedure was evaluated by comparing the obtained results with the findings derived for the same set of aerosol samples analyzed using a microwave procedure for sample dissolution with subsequent ICP-OES analysis. Finally the developed procedure was applied for the analysis of crustal and trace elements in PM10 samples collected at an urban site (Getreidemarkt, Vienna) and a rural site (Hartberg, Styria), in Austria. The concentrations of the investigated crustal elements varied between some hundred ng m−3 and few µg m−3 with highest concentrations for Fe and Si, distinctly reduced concentrations ranging from some ng m−3 (Sr) to more than hundred ng m−3 (K) were found for trace elements. Observed PM10 concentrations were found to be in accordance to literature findings from urban sites in central Europe.