A highly selective bulk optode based on 6-{4-(2,4-dihydroxy-phenyl)diazenyl)phenyl}-2-oxo-4-phenyl-1,2-dihydro-pyridine-3-carbonitrile incorporating chromoionophore V for determination of nano levels of cadmium

Eco-friendly optical sensor for precise detection of gold ions in diverse matrices through the integration of β-2-hydroxybenzyl-3-methoxy-2-hydroxyazastyrene in a PVC membrane

An environmentally conscious methodology is investigated for the precise and discerning identification of trace concentrations of gold ions in diverse matrices. A novel optical sensor membrane is proposed for the determination of Au3+ ions, utilizing the immobilization of β-2-hydroxybenzyl-3-methoxy-2-hydroxyazastyrene (HMHS) entrapped in polyvinyl chloride (PVC). The sensor incorporates sodium tetraphenylborate (Na-TPB) as the ionic additive and dibutyl phthalate (DBP) as a plasticizer. Under optimal conditions, the suggested sensor exhibits a linear calibration response to Au3+ ions within a concentration range of 5.0 to 165 ng mL-1. Detection and quantification limits are specified as 1.5 and 4.8 ng mL-1, respectively, with a rapid response time of 5.0 min. Upon presentation, this optical sensor not only affirms high reproducibility, stability, and an extended operational lifespan but also showcases exceptional selectivity for Au3+ ions. Notably, no discernible interference is observed when assessing the potential influence of other cations and anions on Au3+ ion detection. The adaptability of this optical sensor is validated through its successful application in determining Au3+ ion concentrations across various sample types, including water, environmental, cosmetics, and soil matrices.

Utilization of a novel PVC- optical sensor for high sensitive and selective determination of zinc ion in real samples

A novel and highly specific bulk membrane optode was developed for the ultra-sensitive detection of zinc(II) in biological, pharmaceutical, and water samples. The polymer inclusion membrane (PIM) utilized in this study consists of 50% polyvinyl chloride (PVC) as a base polymer, 9.00% DOP (dioctylphthalate) as the plasticizer, and 40.0% D2EHPA (di(2-ethlyhexyl)phosphoric acid) as the carrier. To facilitate the spectrophotometric determination of zinc(II), a colorimetric reagent, namely 4-(2-arsonophenylazo) salicylic acid (APASA) {1.00%, m/v}, was employed. When Zn(II) was extracted into the PIM, it led to the creation of the zinc-D2EHPA complex. This complex then underwent a reaction with APASA, resulting in the formation of a red Zn - APASA complex with a maximum absorption wavelength (λmax) of 558 nm. To optimize the response of the optode, a central composite design was employed, considering variables such as the amount of additive and reagent, response time, and pH. When operated under the specific optimal conditions, the sensor demonstrated a limit of quantification (LOQ) of 0.74 ng/mL (equivalent to 1.17 × 10-8 M) and a limit of detection (LOD) of 0.22 ng/mL (equivalent to 3.44 × 10-9 M). The optode membrane demonstrated excellent reproducibility, stability, and a relatively long lifespan, making it suitable for precise and accurate monitoring of Zn(II) ion content. Regeneration of the optode was achieved effectively using 0.25 nitric acid solution, and its response exhibited reversibility and reproducibility, showed a relative standard deviation of less than 1.33%. Moreover, the PIM-APASA optode exhibited a high level of effectiveness in accurately determining the presence of Zn(II) ions in real environmental samples.

An innovative approach in titanium determination based on incorporating 2-amino-4-((4-nitrophenyl)diazenyl)pyridine-3-ol in a PVC membrane

A pioneering optical sensor has been effectively developed to achieve precise and reliable detection of titanium ions. The sensor employs an optode membrane composed of 2-amino-4-((4-nitrophenyl)diazenyl)pyridine-3-ol (ANPDP) and sodium tetraphenylborate (NaTPB) incorporated into a plasticized PVC matrix, with dioctyl sebacate (DOS) acting as the plasticizer. When exposed to Ti4+ ions at pH 8.25, the color of the sensing membrane undergoes a distinctive transformation from yellow-orange to violet. Extensive investigations were carried out to assess and optimize various factors influencing the efficiency of ion uptake. Through careful experimentation, the optimum conditions were determined to be 60.0% DOS, 6.0% ANPDP, 30% PVC, and 4.0% NaTPB, with a rapid response time of 5.0 min. Within these conditions, the developed optode demonstrates an impressive linear range of 3.0-225 ng mL-1, boasting detection (LOD) and quantification (LOQ) limits of 0.91 and 2.95 ng mL-1, respectively. Moreover, the precision of the sensor, as indicated by the relative standard deviation (RSD%), remained consistently below 1.55% in six replicate determinations of 100 ng mL-1 Ti4+ across diverse membranes. The selectivity of the sensor was rigorously examined for a range of cations and anions, successfully establishing the tolerance limits for interfering species. Notably, the presence of EDTA as a masking agent did not compromise the high selectivity of the sensor. Consequently, the innovative probe holds significant potential as a reliable analytical tool for quantifying titanium content in various samples, including water, geological materials, soil, plants, paints, cosmetics, and plastics.

A modified selective optical sensor for selenium determination based on incorporating xylenol orange in a poly(vinyl chloride) membrane

A novel optical sensor has been developed to measure selenium ions. The sensor membrane was created by mixing xylenol orange (XO) and sodium tetraphenylborate (NaTPB) with a plasticized poly(vinyl chloride) membrane that contained o-nitrophenyl octyl ether (o-NPOE) as a plasticizer. XO was previously established for use in a colorimeter to measure selenium in water and other media. At pH 6.6, the color of the detecting membrane changed from orange to pink when in contact with Se4+ ions. Various variables affecting the uptake efficiency were evaluated and optimized. Under optimum conditions (i.e., 30% PVC, 60% o-NPOE, and 5.0% of both XO and NaTPB for 5.0 min as the response time), the proposed sensor displayed a linear range 10-175 ng mL-1 with the detection and quantification limits of 3.0 and 10 ng mL-1, respectively. Also, the precision (RSD%) was better than 2.2% for six replicate determinations of 100 ng mL-1 Se4+ in various membranes. For the detection of Se4+, the selectivity of the sensor membrane was investigated for a number of possible interfering inorganic cations, but no appreciable interference was found. With the use of a 0.3 M HCl solution, the sensor was successfully restored, and the response that may have been reversible and reproducible exhibited an RSD% of less than 2.0%. The sensor has been successfully used to analyze Se4+ ions in environmental and biological materials.

Optical chemical sensor of Gd(iii) based on 5-(2′-bromophenyl- azo)-6-hydroxypyrimidine-2,4-dione immobilized on poly(methyl methacrylate) and 2-nitrophenyloctylether matrix

A novel optical chemical sensor (optode) was fabricated for the determination of Gadolinium ions. The optical sensor was prepared by incorporating a recently synthesized ionophore, 5-(2′-bromophenylazo)-6-hydroxy pyrimidine-2,4-dione (BPAHPD), and 2-nitrophenyloctylether (NPOE) as a plasticizer in poly(methyl methacrylate) (PMMA) membrane. The color of the sensing membrane in contact with Gd(iii) ions changed from yellow to red-orange due to the adsorption of Gd(iii) with the maximum absorbance (λ_max) at 563 nm. The chemical sensor responds optimally towards Gd(iii) ions at the optimum conditions of pH 7.5, contact time 10 min, 150 ng mL⁻¹ Gd(iii), and 5.0 mL solution. The linear regression equation achieved was A = 4.36C (μg mL⁻¹) – 0.15 (r = 0.9976). A linear Gd(iii) calibration curve can be established in the concentration range of 5.0–250 ng mL⁻¹ with R² = 0.9976. Detection and quantification limits are 1.47 and 4.75 ng mL⁻¹, respectively. The molar absorptivity and Sandell sensitivity are found to be 6.86 × 10⁷ L mol⁻¹ cm⁻¹ and 0.023 ng cm⁻², respectively. In addition to its stability and reproducibility, the optode revealed a great selectivity toward Gd(iii) ions as compared to other coexisting ions in real samples. The recovery of Gd(iii) ions from the sensor material was achieved using 0.4 M HNO₃^. The offered optode sensor membrane has been employed to monitor Gd(iii) in soil, sediments, river water, and urine with an internal standard addition method and compared statistically with the ICP-OES method. The results revealed calculated t-values between 1.11–1.85, whereas F values were in the range of 2.46–3.77 which did not exceed the theoretical values, indicating no significant difference at 95% confidence level. The observed percent recovery is in the range of 97.24–102.52%.

A novel optical chemical sensor (optode) was fabricated for the determination of Gadolinium ions.