Optical fiber mercury biosensor based on immobilized urease and bromothymol blue onto the alginate-chitosan membrane in the flow-system

An optical fiber biosensor has been developed for the detection of mercury ion based on inhibition of urease immobilized onto alginate–chitosan membrane, coupled with bromothymol blue (BTB) in the flow system. To get a good performance of the biosensor toward Hg(II) ion detection, the experimental parameters of the biosensor were optimized. Here, the maximum wavelength was detected at 580 nm, with the optimum response at pH of 6. The calibration curve had a dynamic working range at 10 to 500 μg/L of Hg(II) ion with a detection limit of 12.1 μg/L biosensor has been performed by the addition of 1 mM ethylenediaminetetraacetic acid (EDTA) solution, in which five-time cycles have been achieved with the inhibition decrease to 9.94% from the original biosensor response. Applying the biosensor to the real samples showed conformity of results with the reference method, cold vapor atomic absorption spectrometry (CV-AAS). Therefore, this biosensor can be used as a method for routine analysis in the determination of Hg(II) concentration in an aqueous sample.

Presence of Arsenic in Potential Sources of Drinking Water Supply Located in a Mineralized and Mined Area of the Sierra Madre Oriental in Mexico

Mine wastes from the La Aurora mine in the state of Guanajuato were generated by the flotation process and placed in four tailing dumps on the local stream while the plant operated. Given that these wastes contain toxic elements, it is important to establish their impact on the quality of several surrounding natural sources of water that are considered potential drinking water supplies. This study identified four water source types, in which the contents of arsenic (As), mercury (Hg), and thallium (Tl) were exceeded, according to international guideline values for drinking water quality. The first type of aqueous sample corresponded to leachates produced by rainwater infiltration in tailings and water–mineral waste interactions. The second type corresponded to surface water along the Xichú and La Laja Streams, and the third and fourth types involved two groundwater well samples and spring samples, respectively. The Chiquito Stream was used as a reference area that had not been impacted by the mine wastes. The isotopic signatures associated with δ34Ssulfate and δ18Osulfate compositions from the El Ojo de Agua spring are similar to those of the Santa María River and are different from those of the mine waste leachates. This study shows evidence of the presence of As in the El Ojo de Agua spring, which results from dissolution of secondary mineral phases that were produced by alteration of the mine wastes, which then migrated along the Xichú Stream system until reaching the spring. These As-bearing fine particles are prone to dissolution when in contact with this water source. Principal component analysis revealed that the observed As, Tl, and Hg can be attributed to weathering of the mine wastes. However, the results suggest that a natural contribution of these elements could be associated with rainwater–igneous rock interactions.

Reactivation of varicella zoster infection presenting as acute retinal necrosis post COVID 19 vaccination in an Asian Indian male

Purpose: To present the clinical features of a rare case of varicella zoster infection following one dose of Coronavirus Disease 2019 (COVID-19) vaccination in an elderly Asian Indian male. Methods: Retrospective observational case report. Results: A 71-year-old gentleman presented to us with complaints of reduced vision associated with redness and pain in his right eye for 1 week. On examination he revealed a right eye pan uveitis picture with circumcorneal congestion, multiple fine keratic precipitates, anterior chamber cells and flare, vitritis and widespread areas of acute retinal necrosis. His left eye was within normal limits. Ten days prior to the presentation he had received the first dose of COVID-19 vaccine following which he had developed fever for 2 days that preceded the red eye. The patient’s aqueous sample tested positive for varicella zoster virus (VZV) by nested polymerase chain reaction (PCR) method. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in reverse transcriptase polymerase chain reaction (RT-PCR) assay from the aqueous and also from the nasopharyngeal swab was negative. Conclusion and significance: To the best of our knowledge this is the earliest description of a case that has a viral reactivation following COVID-19 vaccination. Elderly people with pre-existing comorbidities, may be at a risk of both primary coronavirus infection and unconceivable risk of aberrant immune reactions leading to a different virus infection or reactivation need to be kept in mind. We present a possible link between SARS-CoV-2 virus vaccination and varicella zoster reactivation in this patient.

Determination of BTEX Compounds in Contaminated Water Using the Novel Vacuum-Assisted-Total Vaporization SPME Method and GO-APTES Fiber

A novel and reliable microextraction technique was used for the fast determination of benzene, toluene, ethylbenzene and xylenes (BTEX) from contaminated water without any extra steps for the preparation or extraction of the aqueous sample. Vacuum-assisted-total vaporization-solid-phase microextraction (SPME) eliminated one of the partitioning steps in conventional headspace SPME and caused an increase in the sensitivity and speed of the method. A home-made graphene oxide/3-aminopropyl-triethoxysilane nanocomposite SPME fiber was synthesized and used as the extraction phase for efficient extraction. Several crucial parameters were optimized, such as the vaporization time and temperature, extraction time and desorption conditions. At the optimum experimental conditions, a linear wide range calibration curve over a wide range of 1–5,000 ng mL−1 and a relative standard deviation (n = 6) of 6.6–7.3% were obtained. The result of the determination of BTEX as a human health risk from real samples, using the proposed method, revealed an acceptable agreement with a valid method.

Reagent Activated Cotton Fiber for Rapid Determination of Aldehydes in Diverse Matrices

A method to capture and analyze aldehydes in either solution or gas samples on cotton fiber, activated with O-benzyl hydroxylamine (OBA), is developed. The stability of the reagent activated cotton fiber (RACF) with and without capturing aldehydes was 17 days and 24 Hrs, respectively, qualifying the technique for field applications. Thus the aldehyde capturing can be done outside the lab using RACF in any closed environment and bring back to the lab for the quantitative analysis.. The analytical method is based on the gas chromatographic analysis of aldoxime formed between aldehydes and OBA on RACF. Optimized experimental conditions required 50 mg of RACF to capture aldehydes with a reaction time of 15 minutes. The technique detects aldehydes much below the permissible exposure limits of 25 ppm for acetaldehyde (CH3CHO) and 0.75 ppm for formaldehyde (HCHO). The method’s detection limits are 4 ppb of HCHO, 8 ppb of CH3CHO in the gas sample, and 1.5 ppb of HCHO, and 19 ppb of CH3CHO in the solution or aqueous sample. The analytical method was validated within the established quantitation ranges as per the required International Council for Harmonization Guidelines (CPMP/ICH/381/95). The RACF is a quick tool to measure aldehydes in a polymer sample, laboratory cupboards or refrigerators, and chemical products. The method described here complies with green analytical chemistry principles such as reduction in a solvent, chemical sample size and waste generation, cost-effectiveness, and usage of a biodegradable substrate.