title: Miniaturized and direct spectrophotometric multi-sample analysis of trace metals in natural waters.
abstract: Trends in the analysis of trace metals in natural waters are mainly based on the development of sample treatment methods to isolate and pre-concentrate the metal from the matrix in a simpler extract for further instrumental analysis. However, direct analysis is often possible using more accessible techniques such as spectrophotometry. In this case a proper ligand is required to form a complex that absorbs radiation in the ultraviolet-visible (UV-Vis) spectrum. In this sense, the hydrazone derivative, di-2-pyridylketone benzoylhydrazone (dPKBH), forms complexes with copper (Cu) and vanadium (V) that absorb light at 370 and 395 nm, respectively. Although spectrophotometric methods are considered as time- and reagent-consuming, this work focused on its miniaturization by reducing the volume of sample as well as time and cost of analysis. In both methods, a micro-amount of sample is placed into a microplate reader with a capacity for 96 samples, which can be analyzed in times ranging from 5 to 10 min. The proposed methods have been optimized using a Box-Behnken design of experiments. For Cu determination, concentration of phosphate buffer solution at pH 8.33, masking agents (ammonium fluoride and sodium citrate), and dPKBH were optimized. For V analysis, sample (pH 4.5) was obtained using acetic acid/sodium acetate buffer, and masking agents were ammonium fluoride and 1,2-cyclohexanediaminetetraacetic acid. Under optimal conditions, both methods were applied to the analysis of certified reference materials TMDA-62 (lake water), LGC-6016 (estuarine water), and LGC-6019 (river water). In all cases, results proved the accuracy of the method.
authors.affiliation: Laboratory of Toxicology Faculty of Marine and Environmental Sciences, Universidad de Cádiz, Cádiz 11510, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Albendín
authors.affiliation: Department of Analytical Chemistry, Faculty of Marine and Environmenal Sciences, Universidad de Cádiz, Cádiz 11510, Spain. Electronic address: joseantonio.lopezlopez@uca.es.
authors.forename: José A
authors.initials: JA
authors.lastname: López-López
authors.affiliation: Department of Analytical Chemistry, Faculty of Marine and Environmenal Sciences, Universidad de Cádiz, Cádiz 11510, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Pinto
mesh_terms: D003300:Copper / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods; D005618:Fresh Water / Q000032:analysis*; D006835:Hydrazones / Q000737:chemistry; D007202:Indicators and Reagents; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D014639:Vanadium / Q000032:analysis*
chemical_list: D006835:Hydrazones; D007202:Indicators and Reagents; D014639:Vanadium; D003300:Copper
keywords: Box–Behnken; Cu; Microanalysis; Trace metals; V; dPKBH