Colorimetric analysis of heavy metal ions can be realized by the aid of Ag nanoparticles to improve the analytical characteristics. The method is based on the localized surface plasmon resonance (LSPR) properties of the Ag nanoparticles (AgNPs). In this work, we applied the AgNPs with the addition of dithizone to further improve the selectivity and sensitivity of Pb2+ analysis. Colorimetric sensing of Pb2+ ions based on the polyvinyl alcohol (PVA)-stabilized-colloidal AgNPs in the presence of dithizone is reported. A linear decrease in the AgNPs LSPR absorbance at 421 nm was observed along with the increase in the Pb2+ concentration in the range of 0.50–10 µg/L. The other ions give a minor change in the LSPR absorbance of colloidal AgNPs. The Pb2+ limit of detection, the limit of quantification, and sensitivity were found to be 0.64 ± 0.04 µg/L, 2.1 ± 0.15 µg/L, 0.0282 ± 0.0040 L/µg (n = 5), respectively. The obtained sensitivity is comparable with that of the immunosensing method. The proposed method could offer a good alternative for colorimetric analysis of Pb2+ ions by using nanoparticles in the presence of ligands, which can improve selectivity.

Analysis of Fe3+ ion present in aqueous solutions is always of interests. Recently, this ion has been analyzed by colorimetric methods using colloid of silver nanoparticles (AgNPs) in capping agents of polymers. The reaction mechanism between AgNPs and Fe3+ is still subject to the further investigation. In this work, 1,10-phenanthroline was used to probe the reaction mechanism between AgNPs and Fe3+ ion in the solution. The colloids of AgNPs were prepared in the polyvinyl alcohol (PVA) solution and reacted with Fe3+. The colloid surface plasmon absorbance decreases linearly along with the increase in Fe3+ concentration. The addition of 1,10-phenanthroline to mixture changes the solution to red, indicating that the reaction produces Fe2+. This suggests that the reduction of the AgNPs absorbance is the result of oxidation of the Ag nanoparticles along with the reduction of Fe3+.

Citral-Methylanthranilate Schiff base was synthesized by the reaction of citral and methylanthranilate in simple condensation technique. The synthesis was carried out at temperature (90 ± 5) °C and various synthesis times of 15 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, and 4 hours. Product of Citral-Methylanthranilate Schiff base spreads color in bright red to black brown as the synthesis times increases. The results of the refractive index of synthesis time variation were 1.541 to 1.561. The values of density at various synthesis times were 1.017 to 1.042 g/mL. The results of the specific gravity of synthesis time variation were 1.026 to 1.050. Analysis with GC-MS was performed to prove that citral-methylanthranilate was actually formed and resulted in the peaks at 18.023 and 19.123 minutes.

Kemampuan adsorpsi ion besi oleh sedimen telah dikaji dalam pengaruh variasi konsentrasi ion besi dan waktu kontak untuk menentukan isoterm dan kinetika adsorpsi. Isoterm adsorpsi didasarkan pada hasil adsorpsi ion besi pada konsentrasi 10 sampai 30 ppm dengan interval 5 ppm. Lebih lanjut, kinetika adsorpsi ditentukan dari variasi waktu kontak yaitu 30 sampai 150 menit dengan interval 30 menit. Semua hasil adsorpsi ion besi oleh sedimen diukur dengan menggunakan spektrofotometer serapan atom. Hasil penelitian menunjukkan bahwa adsorpsi ion besi oleh sedimen mengikuti isoterm BET dengan nilai CBET sebesar 18,6667 L/mg dan korelasi sebesar 0,8577. Model kinetika adsorpsi yang lebih sesuai adalah pseudo orde dua dengan nilai R2 sebesar 0,9999 dan nilai k2 adalah 84,604 g mg-1 jam-1.   Kata kunci: Isoterm Adsorpsi, kinetika, ion besi, sedimen