A step towards accreditation: A robustness test of etching process

Multiclass determination of endocrine disruptors in urine by hollow fiber microporous membrane and liquid chromatography

A simple and rapid methodology was developed using hollow fiber membrane microporous and a 96-well plate system for a high throughput multiclass determination of endocrine disruptors in human urine (diclofenac, diazepam, carbamazepine, ibuprofen, naproxen, carbofuran, methyl parathion, 17-α-ethynyl estradiol, bisphenol A and benzophenone). The quantification and detection of the chemicals were carried out by an HPLC-diode array detector. The fixed conditions for carrying out the method optimization were 1.5 mL of sample and 300 μL of solvent desorption. Multivariate and univariate models were applied to optimize the parameters of the method, achieving the following conditions: 20% diluted urine, 1-octanol of extraction solvent impregnated in the microporous membrane, 70 min extraction in pH 3.0 and 30 min with a mixture of 75% methanol and 25% acetonitrile (v/v) for the desorption. The R² were ≤ 0.9973 for ibuprofen. The LOD ranged from 3.3 to 16.7 ng mL^-1 and the LOQ from 10 to 50 ng mL^-1. Relative recoveries ranged from 71% to 126%. The repeatability (n = 3) ranged from 0.22% to 12.01%, and the intermediate precision (n = 9) ranged from 0.13% to 17.76%. The method presents a good alternative for the determination of different classes of compounds in human urine.

Alpha track registration and revelation in CR-39 using new etching method for ultratrace alpha radioactivity quantification in solution media

A CR-39 based method was developed for measuring the ultra-trace alpha radio activities in aqueous samples having curie levels of γ/β-radio activities. The chemical etching method was optimized to reveal the alpha tracks in CR-39. This new chemical etching method involved the use of a phase transfer catalyst tetraethylammonium bromide which reduced the track revelation induction time without deteriorating the track-etch parameters. The alpha track-etch parameters such as bulk-etch rate, track-etch rate, induction time, and the critical angle of alpha track registration were measured at 60 and 70 °C, with and without using a phase transfer catalyst in the chemical etching for the comparison and optimization. The track registration efficiency of CR-39 in the solution medium was measured using the samples having known alpha activity of mixPu, and value obtained was found to be (4.42 ± 0.12) × 10−4 cm. The registration efficiency value thus obtained was corroborated with the expected efficiency expected from the calculated range of alpha particles in the solution. This CR-39 based method was employed to quantify the alpha activity, as low as 0.2 Bq mL−1, in the aqueous radiopharmaceutical samples having the curie levels of γ/β radio activities.

High-throughput approach for the in situ generation of magnetic ionic liquids in parallel-dispersive droplet extraction of organic micropollutants in aqueous environmental samples

In this work, a novel and high-throughput parallel-dispersive droplet extraction (Pa-DDE) based on in situ formation of the hydrophobic MILs ([Co(C₄IM)₄⁺²]2[NTf₂^-], [Ni(C₄IM)₄⁺²]2[NTf₂^-] and [Ni(BeIM)₄⁺²]2[NTf₂^-]) is demonstrated, for the first time, for the determination of benzophenone, metolachlor, triclocarban, pendimethalin, 4-methylbenzylidene camphor, and 2-ethylhexyl-4-methoxycinnamate from aqueous environmental samples. This experimental setup is comprised of a 96-well plate system containing a set of magnetic pins which were used to collect the MIL droplet after in situ formation. This consolidated system enabled simultaneous extraction of up to 96 samples and MIL production in one step. Using this apparatus, sample preparation times of 0.78 min per sample was achieved. The experimental conditions were carefully optimized using uni and multivariate approaches. The optimal conditions were comprised of sample volume of 1.25 mL, 4 mg of [Co(C₄IM)₄⁺²]2[Cl^-] and 40 μL of LiNTf₂ for the in situ formation, and dilution in 20 μL of acetonitrile. The analytical parameters of merit were successfully determined with LODs ranging from 7.5 to 25 μg L^-1 and coefficients of determination higher than 0.989. Intraday and interday precision ranged from 6.4 to 20.6% (n = 3) and 11.6-22.9% (n = 9), respectively, with analyte relative recovery ranging between 53.9 and 129.1%.

Robustness testing of an in-situ caesium extraction unit

Following on from the successful development and validation of a prototype automated unit for the extraction of radiocaesium from seawater, the unit was redesigned to be smaller, easier to transport and better suited for field work. An extension of the validation process was undertaken to include robustness testing. Robustness testing evaluates the behaviour of a procedure when deliberate small changes are made. This requires the identification and testing of experimental factors which could have an impact on the results. The Plackett-Burman approach was adopted to minimise the number of experiments needed for testing. The study showed that the analytical method was not sensitive to any of the factors tested, indicating that the method is robust.