Anoop Agrawal

Review of solid state electrochromic coatings produced using sol-gel techniques☆

Solid state electrochromic (EC) devices are composed of multiple thin film layers in which each coating performs specific optical and electrical functions. This review describes the principles, physical configuration and the materials employed to make the EC devices. The merits of sol-gel method to deposit coatings for this application are discussed. Sol-gel activities to date for making these devices and coatings are summarized.

Extraction of Beryllium from Refractory Beryllium Oxide with Dilute Ammonium Bifluoride and Determination by Fluorescence: A Multiparameter Performance Evaluation

Beryllium exposure can cause a number of deleterious health effects, including beryllium sensitization and the potentially fatal chronic beryllium disease. Efficient methods for monitoring beryllium contamination in workplaces are valuable to help prevent dangerous exposures to this element. In this work, performance data on the extraction of beryllium from various size fractions of high-fired beryllium oxide (BeO) particles (from < 32 μ m up to 212 μ m) using dilute aqueous ammonium bifluoride (ABF) solution were obtained under various conditions. Beryllium concentrations were determined by fluorescence using a hydroxybenzoquinoline fluorophore. The effects of ABF concentration and volume, extraction temperature, sample tube types, and presence of filter or wipe media were examined. Three percent ABF extracts beryllium nearly twice as quickly as 1% ABF; extraction solution volume has minimal influence. Elevated temperatures increase the rate of extraction dramatically compared with room temperature extraction. Sample tubes with constricted tips yield poor extraction rates owing to the inability of the extraction medium to access the undissolved particles. The relative rates of extraction of Be from BeO of varying particle sizes were examined. Beryllium from BeO particles in fractions ranging from less than 32 μ m up to 212 μ m were subjected to various extraction schemes. The smallest BeO particles are extracted more quickly than the largest particles, although at 90°C even the largest BeO particles reach nearly quantitative extraction within 4 hr in 3% ABF. Extraction from mixed cellulosic-ester filters, cellulosic surface-sampling filters, wetted cellulosic dust wipes, and cotton gloves yielded 90% or greater recoveries. Scanning electron microscopy of BeO particles, including partially dissolved particles, shows that dissolution in dilute ABF occurs not just on the exterior surface but also via accessing particles interiors due to porosity of the BeO material. Comparison of dissolution kinetics data shows that as particle diameter approximately doubles, extraction time is increased by a factor of about 1.5, which is consistent with the influence of porosity on dissolution.

Trace beryllium determination in polyvinyl alcohol wipes by extraction and fluorescence detection: interlaboratory analysis†

In the occupational hygiene field, polyvinyl alcohol (PVA)-based wipe materials are used extensively for beryllium (Be) sample collection and analysis. Hence there is a need for validated methods to determine trace Be in such sampling media. In this work an interlaboratory study was carried out to evaluate the performance of an extraction and fluorescence method for determining trace Be in PVA wipes containing refractory beryllium oxide (BeO). The method entails heated extraction with dilute ammonium bifluoride (NH4HF2), followed by fluorescence measurement of extracted Be in extract aliquots after reaction with the high quantum-yield fluorophore, hydroxybenzoquinoline sulfonate (HBQS). Certified BeO-spiked PVA wipe materials were prepared at six different levels ranging from 0.030 to 5.6 μg Be per wipe. Dry wipe materials and wipes wetted with 0.5 mL of deionized water were spiked as above. Duplicates of these materials, plus media blanks, were distributed to eight participating laboratories; spiking levels were unknown to the volunteers. Each participant was requested to carry out extraction and fluorescence measurement in accordance with an ASTM International standard test method, ASTM D7202, and to report their results in units of μg Be per wipe sample. Interlaboratory precision, as estimated by percent relative standard deviations (RSDs), ranged between 4.5% and 16%. Estimated percent Be recoveries were 90–99% for dry wipes and between 87 and 93% for wetted wipe materials after volume correction for water content.

Optical molecular fluorescence determination of ultra-trace beryllium in occupational and environmental samples using highly alkaline conditions

ABSTRACT Exposures to beryllium (Be), even at extremely low levels, can cause severe health effects in a percentage of those exposed; consequently, occupational exposure limits (OELs) promulgated for this element are the lowest established for any element. This work describes the advantages of using highly alkaline dye solutions for determination of Be in occupational hygiene and environmental samples by means of an optical molecular fluorescence technique after sample extraction in 1–3% (w˖w−1) aqueous ammonium bifluoride (NH4HF2). Improved attributes include the ability to further enhance the detection limits of Be in extraction solutions of high acidity with minimal dilution, which is particularly beneficial when NH4HF2 solutions of higher concentration are used for extraction of Be from soil samples. Significant improvements in Be method detection limits (MDLs) are obtained at levels manyfold below those reported previously for this methodology. Notably, MDLs for Be of <0.01 ng L−1 /0.1 ng per sample have been attained, which are superior to MDLs routinely reported for this element by means of the most widely used ultra-trace elemental measurement technique, inductively coupled plasma mass spectrometry (ICP-MS). Very low MDLs for Be are essential in consideration of reductions in OELs for this element in workplace air by health organisations and regulatory agencies in the USA and internationally. Applications of enhanced Be measurements to air filter samples, surface wipe samples, soils and newly designed occupational air sampler inserts are illustrated.

Beryllium Measurement in Commercially Available Wet Wipes

Analysis for beryllium by fluorescence is now an established method which is used in many government run laboratories and commercial facilities. This study investigates the use of this technique using commercially available wet wipes. The fluorescence method is widely documented [1,2] and has been approved as a standard test method by the ASTM International and the National Institute for Occupational Safety and Health. The procedure involves dissolution of samples in an aqueous ammonium bifluoride solution and then adding a small aliquot to a basic hydroxybenzoquinoline sulfonate fluorescent dye, (Berylliant™, Inc., Detection Solution Part #CH-2) and measuring the fluorescence. This method is specific to beryllium. This work will explore the use of three different commercial wipes spiked with beryllium as beryllium acetate or as beryllium oxide and subsequent analysis by optical fluorescence. The effect of possible interfering metals such as Fe, Ti, and Pu in the wipe medium is also examined.