Nijhuma Kayal

Quantifying uncertainty in the measurement of arsenic in suspended particulate matter by Atomic Absorption Spectrometry with hydride generator

Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis. The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties. The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis, weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that during the period from 31st Jan. 2008 to 7th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m3 with 95% confidence level (k = 2).

Evaluation and Expression of Uncertainty in the Determination of Alumina in Deodorants Using Complexometric Method

Recent studies reveal that aluminum has several adverse effects on human life and causes several diseases. There are various sources by which aluminum call enter into a human body: The deodorant is one of them, In this paper, the concentration of alumina (%Al(2)O(3)) has been assessed for three different deodorants (namely, A, B, and C) using all indirect complexometric method along with all uncertainty budget. The uncertainty in the measurement has been evaluated and expressed according to the requirements of the standard ISO/IEC 17025:2005. It has been identified that the uncertainty in the measurement arises mainly from repeatability, standardization of zinc acetate, and volume measurement, which have been evaluated and combined according to the EURACHEM guidelines. The concentrations of alumina were 0.81 +/- 0.01, 0.73 +/- 0.01, and 0.49 +/- 0.01 g per 100 mL, respectively, for A, B, and C deodorants. The uncertainty in the measurement varies from 1.2 % to 2 % for the three deodorants. The results show that a person using A and B brand deodorants receives, respectively, 65 % and 48 % higher exposure to aluminum on the skin than a person using the C brand.

Fabrication of Mullite Bonded Porous SiC Ceramics via Sol-Gel Coated Precursor

In the present work oxide bonded porous SiC ceramics were fabricated using surface modified sol-gel mullite coated SiC particles. The coated powder was characterized by measuring zeta potential at different pH, XRD analysis, thermal analysis and FTIR spectroscopy. To observe the role of mullite source on the properties of final ceramics two other sources of mullite (commercial mullite and synthesized mullite through sol-gel route) were also used. Porous SiC ceramics were prepared by sintering powder compact of mullite coated SiC/SiC+mullite particles in air at 1300°C for 3 h keeping the mullite content same. The morphologies, phase composition, porosity, pore size distribution and mechanical strength of porous ceramics were examined as a function of mullite source. It was observed that the coating of SiC particles by sol-gel mullite precursor effectively reduced the % SiC oxidation degree from 51 to 33%. The ceramics obtained from sol-gel coated precursor had a flexural strength of ∼23 MPa at porosity of ∼45 vol% and ceramics fabricated from SiC with sol-gel derived mullite powder had a flexural strength of ∼25 MPa at porosity of ∼42 vol%. Microstructure observations revealed that neighbouring SiC particles were bonded by well-developed neck consisting of needle-shaped mullite grown in a siliceous matrix.

Stepwise complexometric determination of aluminium, titanium and iron concentrations in silica sand and allied materials

BackgroundThis study aimed at measuring the quantities of Al, Ti and Fe in silica sand and allied materials employing a complexometric method in the same analyte and a stepwise indirect titration with EDTA. The method involves the complexation of Al, Ti and Fe with excess EDTA and the selective de-complexation of TiO-EDTA and Al-EDTA complexes with tartaric acid and NaF respectively. In addition to its simplicity, rapidity and accuracy, the proposed method does not require the use of a separation technique or any sophisticated instrumentation.ResultsEach of the test samples were analyzed five times using the proposed method. The methods accuracy was confirmed by analyzing the US National Institute of Standards and Technologys (NIST) Standard Reference Materials (SRM) 81a, 89 and IPT SRM 61 using the procedure proposed, in addition to analyzing Ti and Fe levels by spectrophotometry and that of Al by complexometry.ConclusionThe study shows that there is good agreement between the proposed and existing methods. The standard deviations of the measurements were calculated by analyzing five replicates of each sample, and were found to be less than 1.5% in our method.

Selective masking and demasking for the stepwise complexometric determination of aluminium, lead and zinc from the same solution

BackgroundA complexometric method based on selective masking and de-masking has been developed for the rapid determination of aluminium, lead and zinc from the same solution in glass and glass frit samples. The determination is carried out using potassium cyanide to mask zinc, and excess disodium salt of EDTA to mask lead and aluminium. The excess EDTA was titrated with standard Mn(II)SO4 solution using Erichrome Black-T as the indicator. Subsequently selective de-masking agents – triethanolamine, 2,3-dimercaptopropanol and a formaldehyde/acetone mixture – were used to determine quantities of aluminium, lead and zinc in a stepwise and selective manner.ResultsThe accuracy of the method was established by analysing glass certified reference material NBS 1412. The standard deviation of the measurements, calculated by analysing five replicates of each sample, was found to be less than 1.5% for the method proposed.ConclusionThe novelty of the method lies in its simplicity and accuracy afforded by there not being a need for a prior separation or instrumentation. The proposed method was found to be highly selective for the precise determination of aluminum, zinc and lead in the routine analysis of glass batch and allied materials.

Properties of Porous SiC Ceramics Processed by Gelation and Consolidation of Boehmite Coated SiC Suspensions

ABSTRACT SiC powder was dispersed in various concentrations of boehmite sol. The boehmite coated SiC powder was characterized by zeta potential measurement, TEM and FT-IR analyses. Mullite bonded porous SiC ceramics were fabricated by sintering boehmite coated SiC powder compact via a pressureless sintering in air at 1300oC and were characterized by XPS, XRD, SEM analyses. The sintered ceramics have an interconnected open porous network with near uniform pore diameter. Rod shaped mullite crystals were observed in the neck region that bonded the SiC particles together. Effect of boehmite sol concentration on phase composition, microstructure, flexural strength, porosity and pore size distribution was studied. The ceramics synthesized from 30 wt% boehmite sol coated SiC powder contained 26 wt% mullite with ∼30 vol% porosity. GRAPHICAL ABSTRACT

Properties of mullite-bonded SiC ceramics from mullite precursor sol coated SiC powder and crystallization kinetics of mullite formation

Mullite bonded -bonded porous silicon carbide (SiC) ceramics were fabricated by sintering sol–gel mullite-coated SiC particles. The coated powder was characterized by measuring zeta potential at different pH, X-ray photoelectron spectroscopy (XPS), XRD analysis and thermal analysis. The thermal oxidation behaviour of coated SiC powder was examined by thermogravimetry (TG)-Differential thermal analysis (DTA) technique in dry air. Mullite formation exhibited two exothermic peaks; the first 1195–1213°C and the second at 1319–1358°C. The activation energy for mullite crystallization in the first step ranged from 884 to 1250 KJ mole− 1 and in second step it ranged from 759 to 1018 KJ mole− 1. Characterization of resulting SiC ceramics were done by XRD, SEM, TEM, EDS, porosity, pore size distribution analysis and measurement of mechanical strength. The ceramics with porosity ∼42 vol.-% exhibited flexural strength of ∼23 MPa. Microstructure observations revealed that neighbouring SiC particles were bonded by well-developed neck consisting of needle-shaped mullite grown in a siliceous matrix.