Image Reversal Resist Photolithography of Silicon-Based Platinum and Silver Microelectrode Pattern

Silicon-based platinum (Pt) and silver (Ag) microelectrodes are constructed using photolithography technique and used in detecting arsenic activity in different electrolytes. Pt and Ag have good properties either as a working, a counter, or a reference electrode due to their low electrical resistance, high melting point, and high chemical stability. This chemical sensor has the ability to detect the changes in the level or activity of arsenic in electrolytes. Patterning these metals by wet chemical or dry etching is not a feasible process as these metals cannot be etched properly. The lift-off process can be applied to ease the etching process, but it has a major problem whereby the metal particles or ears may remain at the edges at the end of the process. The process variables, particularly the resist slope, were investigated to reduce possible defects using an image reversal resist. The thickness and angle of the resist side wall were measured by SEM. The effects of many factors that may influence or resist steep angle formation were analyzed and optimized with the Design of Experiment (DOE) technique to achieve the target recipe of resist angle < 60°. The lower angle of the resist side wall resulted in a better percentage yield of good electrode pattern after the lift-off process. The ability of fabricated microelectrode and influence of supporting electrolytes in arsenic determination were discussed.

Footprint of Arsenic Contamination in Sediments and Water from Mining Sites – A case study based on multivariate optimization by GF AAS

Arsenic contamination is worrisome in mineral exploration regions. Efficient arsenic monitoring is dependent on detectability at trace level in environmental matrices. This paper presents a procedure to evaluate the occurrence of arsenic in environmental sediment and water samples collected from a mining area in Catalão, Goiás State (GO), Brazil. The water and sediment samples were analyzed by graphite furnace atomic absorption spectrometry (GF AAS) after appropriate chemical treatment. For the arsenic determination, analytical performance was improved employing multivariate tools. The instrumental conditions were optimized using a 23 factorial design and the response surface methodology (RSM) was applied with a central composite design (CCD). Iridium was used as a permanent modifier. The results for the sediment samples showed arsenic concentrations below the threshold for adverse effects ranging from 2.06 to 3.82 mg Kg-1. The concentrations in water samples were below LOD. The LOD and LOQ were, respectively, 0.33 and 1.09 µg L-1 to water and digested sediment samples. Under the optimal conditions, the dynamic working range was linear of LOQ to 50.0 µg L-1. The method was applied to determine concentrations of arsenic in water and sediments collected from mining sites, which can be used to assess the availability of arsenic in the region.

Trace level determination of various types of analyte using selective chemosensor: a general survey

Trace level determination of analyte is an extremely important phenomenon and highly relevant area of environmental science, biology, medicine and pharmacology. In this review we have described different type of chemosensor that have been used so far for trace level determination of different types of analyte. Applications of chemo sensor in the arsenic determination have been discussed here. Determination of amino acid by fluorescence spectroscopy has been depicted. Detection of poisonous organic analytes by chemosensor have been made. Some chemosensors have been found to be effective to the determination of selective cations. Various techniques used for determination of analyte by using chemo sensor as well as probable sensing mechanism have been explained here.

HG-ICP-OES Technique, a Useful Tool for Arsenic Determination in Soft Water

This paper presents a fast, sensitive, linear and precise method for the determination of arsenic (As) at trace levels, from different types of water (drinking, mineral, surface water and groundwater) using hydride generation and optical emission spectrometry with inductively coupled plasma (HG-ICP-OES). In order to generate the hydride, the initial pretreatment of the samples with a mixture of potassium iodide and ascorbic acid is necessary, in hydrochloric acid medium for reducing the As5+ to As3+ ions and for the subsequent formation of the hydride from As3+ ions and sodium borohydride, in a continuous-flow cell. The quantification limit of the method (LOQ = 0.43 �g/L), the precision (3.41%), the recovery yield (95%) and the measurement uncertainty of 24% frame the method within the limits imposed by the acceptance criteria of an analytical method for arsenic determination. The proposed method was tested on several types of water, the obtained results being compared to those obtained by applying two sensitive and selective alternative methods using ICP-MS, respectively ultrasonic nebulizer and ICP-OES.

A simple paper-based approach for arsenic determination in water using hydride generation coupled with mercaptosuccinic-acid capped CdTe quantum dots

Paper-based device with MSA-CdTe QDs as arsenic detection probe is presented.

Universal isotope dilution analysis of arsenic with labelled methane gas by dynamic reaction cell ICP-MS

Universal ID method using a labelled reaction gas in ICP-DRC-MS was investigated and was developed for arsenic determination.

Trace Arsenic Determination in a TiO2 Pigment Matrix Using Electrothermal Atomic Absorption Spectrometry

This work describes the use of electrothermal atomic absorption spectrometry in combination with a pyrolytic graphite-coated tube with a platform for trace arsenic (As) determination in titanium dioxide (TiO2) pigment. This type of matrix is challenging, as complete digestion in hydrofluoric acid-containing solution is needed. First, closed-vessel microwave digestion was performed for the full-sample decomposition. Next, a temperature program was optimized for drying, pyrolysis, and atomization temperatures. Furthermore, the use of a chemical modifier mixture was proposed that reduced the background contribution and prevented significant analyte loss and therefore improved the analytical procedure. The optimized method was validated for the detection (LOD) and quantification (LOQ) limits, the linear concentration range, accuracy, and precision. Special attention was devoted to the matrix-matching solutions in the calibration procedure. Linearity was confirmed in the 5.0 to 100.0 µg/L concentration range ( R2 = 0.999). The average recovery for 16 different real TiO2 pigment samples was 92.0%, and the relative standard deviation value for six replicate measurements was ≤10.4%. Moreover, the LOD and LOQ in terms of the TiO2 pigment mass was determined to be 0.2 µg/(g TiO2) and 0.7 µg/(g TiO2), respectively. The latter complies with Commission Directive 2008/128/EC, which does not allow more than 3 µg As/(g product) as the specific criteria of purity. Finally, based on scanning electron microscopy analysis of unused and several times used pyrolytic graphite-coated tubes, usage of the tube 250 times before replacement is recommended.

FEASIBILITY OF DIRECT SOLID SAMPLING FOR ARSENIC DETERMINATION IN SULFUR-CONTAINING ACTIVE PHARMACEUTICAL INGREDIENTS BY GF AAS

A method for As determination in sulfur-containing active pharmaceutical ingredients (SC-APIs) by direct solid sampling graphite furnace atomic absorption (DSS-GF AAS) was developed. The proposed method was successfully applied to three SC-APIs (hydrochlorothiazide, furosemide and sulfadiazine). Palladium was used as chemical modifier as well as hydrogen during the pyrolysis allowing the direct determination of As in the SC-APIs without interferences caused by gaseous sulfur species. Sample masses (hydrochlorothiazide) from 0.4 to 3 mg were used and calibration with aqueous standard solutions was feasible. The limit of quantification was 0.033 mg g-1 and the calibration ranged from 0.1 to 1.6 ng As. Recoveries for As solutions added directly to the solid samples were between 95 and 103%, showing a good accuracy. The method validation highlighted its robustness, since variation in pyrolysis and atomization temperatures, as well as in Pd and sample masses, did not change significantly the results. Additional experiments showed that this method can be applied to other SC-APIs (as e.g., furosemide and sulfadiazine). Arsenic concentration in hydrochlorothiazide samples ranged from 0.13 to 0.48 mg g-1, while in furosemide and sulfadiazine samples it was from 0.49 and 0.54 mg g-1, respectively. The use of DSS-GF AAS does not require previous sample digestion and As could be directly determined in the solid samples providing some advantages, as lower risks of contamination and analyte losses, good accuracy and limits of quantification.