KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 https://bestjournal.
id/index.
php/kovalen Preconcentration of Cr (VI) Using Ca-Alginate-EDTA Microcapsules in a Column System for UV-Vis Spectrophotometric Analysis Ika Yekti LianasariA.
Aman Sentosa Panggabean.
Resma Lita Farlianti Department of Chemistry.
Faculty of Mathematics and Natural Sciences.
Mulawarman University.
Jln.
Barong Tongkok No.
Gunung Kelua Campus.
Samarinda.
Indonesia Abstract.
This study introduces optimized Ca-Alg-EDTA microcapsules specifically designed as a highperformance column filler for the preconcentration and sensitive detection of toxic Cr(VI) in aquatic systems.
Monitoring Cr(VI) at trace levels is critical due to its high toxicity and environmental persistence.
Unlike previous alginate-based sorbents, this work focuses on a synergistic EDTA integration within a column-switching framework to enhance retention efficiency .
73 %) and capacity .
3995 mg/.
Analytical validation using UV-Vis spectrophotometry demonstrated excellent linearity (R2 = 0.
with a low detection limit of 0.
014 mg/L, ensuring reliability for samples with minimal analyte concentrations.
The methodAos robustness was confirmed through Mahakam River water analysis, yielding a 93.
05 % recovery in compliance with AOAC 2002 standards.
This optimized microencapsulation approach provides a cost-effective and sustainable solution for routine environmental monitoring of heavy metal contamination.
Keywords: Ca-Alg-EDTA.
Cr(VI), microcapsules, preconcentration.
UV-Vis Spectrophotometry Abstrak.
Penelitian ini memperkenalkan mikrokapsul Ca-Alg-EDTA teroptimasi yang dirancang khusus sebagai pengisi kolom berkinerja tinggi untuk prakonsentrasi dan deteksi sensitif Cr(VI) yang beracun dalam sistem Pemantauan Cr(VI) pada level runut sangat krusial karena toksisitasnya yang tinggi dan persistensinya di lingkungan.
Berbeda dengan sorben berbasis alginat sebelumnya, penelitian ini berfokus pada integrasi sinergis EDTA dalam kerangka sistem kolom untuk meningkatkan efisiensi retensi .
,73 %) dan kapasitas .
,3995 mg/.
Validasi analitik menggunakan spektrofotometri UV-Vis menunjukkan linearitas yang sangat baik (R2 = 0,9.
dengan limit deteksi rendah sebesar 0.
014 mg/L, memastikan keandalan untuk sampel dengan konsentrasi analit Ketangguhan metode ini dikonfirmasi melalui analisis air Sungai Mahakam, menghasilkan perolehan kembali sebesar 93,05 % yang sesuai dengan standar AOAC 2002.
Pendekatan mikrokapsul teroptimasi ini memberikan solusi yang hemat biaya dan berkelanjutan untuk pemantauan rutin kontaminasi logam berat di Kata kunci: Ca-Alg-EDTA.
Cr(VI), mikrokapsul, prakonsentrasi, spektrofotometri UV-Vis Received: November 24, 2025.
Accepted: January 7, 2026 Citation: Lianasari.
Panggabean.
, and Farlianty.
L .
Preconcentration of Chromium (VI) Ions Using Ca-Alginate-EDTA Microcapsules with Column Method and UV-Visible Spectrophotometry.
KOVALEN: Jurnal Riset Kimia, 11.
: 94-105.
INTRODUCTION
ultratrace levels .
1 Ae 0.
5 yuN g/L) is challenging Chromium exists primarily as trivalent as it often falls below the detection limits of Cr.
and the highly toxic, carcinogenic standard UV-Vis spectrophotometry.
Thus, an efficient preconcentration step is essential to A Cr(VI).
Monitoring Cr(VI) Corresponding author E-mail: ikayektilsari@gmail.
https://doi.
org/10.
22487/kovalen.
2477-5398/ A 2025 Lianasari et al.
This is an open-access article under the CC BY-SA license.
KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
interferences (Makosim et al.
, 2020.
Pratiwi et The novelty of this work lies in the systematic , 2.
Among various techniques, column-based solid-phase addresses the sensitivity gap of UV-Vis spectrophotometry for trace Cr(VI) analysis.
sorbents is preferred for its low cost and high evaluating the retention capacity and applying the method to Mahakam River water samples, alginate-based this research provides a robust and eco-friendly hydrogels are leading sustainable materials for framework for routine environmental monitoring heavy metal adsorption due to their tunable of toxic chromium.
Recent porosity and high site density (He et al.
, 2.
While alginate forms stable, non-toxic Caalginate gels, its pristine form lacks sufficient MATERIALS AND METHODS Materials The chemicals used were of analytical selectivity (Indriyani et al.
, 2.
Modification (Ethylenediaminetetraacetic EDTA
(DPC),
K2Cr2O7, 1,5- CaCl2, alginate.
EDTA.
HCl.
H3PO4.
H2SO4, acetone, powerful polydentate ligands that form stable and deionized water.
Real samples were complexes with metal ions within the alginate matrix (Wang et al.
, 2.
(Tenggarong Seberan.
EDTA
Previous research has utilized modified Ca- Mahakam River Instrumentation alginate for capturing metals such as Cd.
Mn.
Instrumentation Orion Cu, and Pb (Sari et al.
, 2016.
Yantyana et al.
AquaMate 8100 UV-Vis Spectrophotometer for Specifically, magnetite-alginate (MNPs- Cr(VI) quantification at yuImax, a Bruker Alpha II ALG) microcapsules have shown significant FT-IR for functional group characterization, and potential for Cu(II) analysis, proving that functionalized alginate can enhance analytical performance (Lianasari et al.
, 2.
However, synergistic effect of Ca-Alg-EDTA for Cr(VI) Procedure Preparation of standard Cr(VI) A 100 mg/L stock solution was prepared Most Cr(VI) studies rely on expensive from K2Cr2O7.
Working standards .
01 Ae 0.
resins or acid-activated alumina (Panggabean mg/L) were prepared by serial dilution.
et al.
, 2.
, which lack the sustainability of Preparation of colorimetric reagent microencapsulated biopolymers.
Furthermore, specialized chelating resins remain a key strategy for flow-based trace metal analysis in river water (Amran et al.
, 2.
This Ca-Alg-EDTA designed as a high-performance column filler.
5% 1,5-diphenylcarbazide was dissolved in acetone.
pH Adjustment All solutions were adjusted to pH 2 A0.
using H2SO4 and H3PO4 to facilitate the Cr(VI)-DPC KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
Absorbance was measured after 5 Ae 10 minutes of color development.
Synthesis of Ca-Alg-EDTA microcapsules Validation and statistical analysis The method was validated for linearity.
Limit Detection (LoD).
Limit Microcapsules were synthesized via the Quantitation (LoQ) based on the standard extrusive dripping method.
Sodium alginate deviation of the intercept and the slope of the solution .
5 Ae 3%) was mixed with varying calibration curve.
Precision was expressed as masses of EDTA .
5 Ae 3 .
This mixture was Relative Standard Deviation (% RSD) from ten added dropwise through a syringe into a CaCl2 replicates, while accuracy was evaluated solution .
1 Ae 2 M) under constant magnetic through a spike-recovery test .
5 mg/L stirring .
The resulting beads were additio.
on Mahakam River samples, following filtered and air-dried at a controlled room AOAC 2002 benchmarks.
temperature for 48 hours to ensure consistency in particle size and porosity (Figure .
RESULTS AND DISCUSSION
Optimization of Ca-Alg-EDTA Microcapsule Synthesis Effect of varying CaCl2 and Na-alginate The optimization of CaCl2 and Na-alginate concentrations was evaluated using a batch system to identify the most effective matrix for Cr(VI) retention (Figure .
The highest Figure 1.
Ca-Alg-EDTA microcapsules Preconcentration and column procedure A glass column .
nternal diameter: 1 c.
was packed with 0.
3 g of optimized Ca-AlgEDTA resin .
ed height: approx.
1 c.
investigate the preconcentration efficiency, 10 mL of 0.
5 mg/L Cr(VI) was passed through the column at a controlled flow rate of 1.
0 mL/min.
The retained Cr(VI) was eluted using 0.
1 M HCl.
The effect of eluent volume .
Ae 10 mL) and contact time .
Ae 120 mi.
was systematically After each cycle, the resin was washed with deionized water for regeneration and reusability tests.
retention efficiency .
6 %) was achieved using a combination of 0.
1 M CaCl2 and 1% Naalginate.
Statistically efficiency were observed as concentrations increased to 2 M CaCl2 and 3 % alginate.
This concentrations of Ca2 and alginate increase the cross-linking density, creating a rigid and compact "egg-box" structure.
Such high density restricts the internal diffusion of Cr(VI) ions into the microcapsule core, thereby reducing the available effective surface area (Indriyani et al.
Wang et al.
, 2.
The 0.
1 M/1 %
combination was selected as it provided an optimal balance between structural stability and matrix porosity.
KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
Figure 2.
Effect of concentration variation on retention efficiency Effect of EDTA mass EDTA acts as a powerful hexadentate chelating The influence of EDTA mass on the agent, introducing additional carboxyl (-COOH) retention efficiency of Cr(VI) is illustrated in and amine (-NH.
groups into the polymer Figure 3.
The data shows a progressive At a mass of 3 g, the ratio of EDTA to increase in efficiency from 39.
12 % .
the alginate backbone provides the maximum EDTA) to a peak of 63.
4 % .
t 3 g EDTA).
availability of these functional groups, which "trap" Cr(VI) coordination bonding.
The significant jump in surface-to-ligand ratio, allowing for better accessibility of the analyte to the internal pores of the resin.
While higher masses might theoretically provide even more sites, 3 g was selected as the optimum to maintain the Figure 3.
Effect of varying EDTA mass on retention efficiency.
This linear enhancement is directly related to the density of active binding sites within the Ca-alginate matrix.
This is consistent with the analytical performance observed in MNPs-ALG systems, where the integration of active components into the alginate structure leads to compared to pristine alginate (Lianasari, 2.
structural integrity of the microcapsule, as excessive EDTA can sometimes weaken the Ca-alginate cross-linking, leading to a more fragile gel (Pratiwi et al.
, 2020.
Wang et al.
Determination of Retention Efficiency and Capacity The adsorption performance of Ca-AlgEDTA microcapsules across varying initial Cr(VI) concentrations is presented in Figures 4 Lianasari et al.
KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 The highest retention efficiency reached peaked at 0.
3995 mg/g when the concentration 73 % at an initial concentration of 0.
4 mg/L, was increased to 2.
5 mg/L.
while the maximum retention capacity .
Figure 4.
Effect of initial Cr(VI) concentration on the retention efficiency of Ca-Alg-EDTA microcapsules .
=3, pH 2 A 0.
5, contact time 24 .
Figure 5.
Effect of initial Cr(VI) concentration on the retention capacity of Ca-Alg-EDTA microcapsules .
=3, pH 2 A 0.
5, contact time 24 .
As the concentration of Cr(VI) increases sites reach equilibrium, a "competitive effect" 4 mg/L, the retention efficiency occurs among the remaining free ions in the begins to decline despite the increase in the solution, preventing further adsorption due to total mass of metal adsorbed per gram of resin the limited number of specific coordination sites .
etention capacit.
This plateau in capacity at (Pratiwi et al.
, 2020.
Wang et al.
, 2.
The 5 mg/L signifies a saturation point.
Based on steady capacity value at higher concentrations adsorption theory, this behavior indicates that confirms that the Ca-Alg-EDTA matrix operates the active functional groups on the surface and via a site-specific binding mechanism, which is within the pores of the microcapsules have ideal for preconcentration purposes where high been fully occupied by Cr(VI) ions.
Once these selectivity at trace levels is required.
KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
Preconcentration Optimization in Column System kinetic equilibrium within the column packing Effect of contact time steadily and reached an optimum of 55.
89 % at The influence of contact time on Cr(VI) (Figure .
The retention efficiency increased 50 minutes.
adsorption was evaluated to determine the Figure 6.
Effect of contact time Mechanistically, this behavior is governed step transitions from surface diffusion to site by mass transfer from the bulk solution to the saturation as the coordination capacity of the surface of the Ca-Alg-EDTA microcapsules.
modified ligands is reached (He et al.
, 2.
During the initial stages .
Ae 40 minute.
, there is an abundance of vacant EDTA coordination sites, leading to a rapid uptake of Cr(VI).
time progresses to 50 minutes, the system approaches a breakthrough point where the rate of adsorption equals the rate of desorption, signifying that the active sites are nearing Effect of eluent volume The elution process is critical for the recovery of preconcentrated analytes.
shown in Figure 7, the optimum eluent volume was found to be 3 mL, yielding the highest concentration of 0.
498 mg/L.
Beyond 60 minutes, the efficiency tends to stabilize, suggesting that the "mass transfer zone" has moved through the entire bed height of the column, and additional contact time no longer significantly improves retention (Pratiwi et al.
, 2.
This optimization strategy in column-packed systems is crucial to balance the interaction time and the flow rate, ensuring maximum uptake of metal ions as previously demonstrated in other preconcentration studies using inorganic-filled columns (Simanjuntak et , 2.
This equilibrium behavior aligns with Figure 7.
Effect of varying eluent volume the fundamental mass transfer principles of alginate-based systems, where the rate-limiting KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
The use of 0.
1 M HCl as an eluent cost-effectiveness promotes the desorption of Cr(VI) through a environmental friendliness of the Ca-Alg-EDTA protonation mechanism.
At low pH, the high concentration of H ions competes with the metal ions for the binding sites on the EDTA Characterization Spectroscopy Results FT-IR ligands and the alginate carboxyl groups.
The The functional groups of Ca-Alg and Ca- protonation of these functional groups weakens Alg-EDTA microcapsules were identified using the coordination bonds, effectively releasing FT-IR spectroscopy to confirm the successful modification of the alginate matrix (Figure 8 and Cr(VI) (Panggabean et al.
, 2.
The choice of a Table .
small eluent volume 3 mL, is essential to The FT-IR spectrum of Ca-Alg displays achieve a high Preconcentration Factor (PF).
characteristic peaks at 3422.
76 cm-A (O-H).
According to Turan et al.
, an ideal 18 cm-A .
symmetric COO- stretchin.
, elution process should recover the maximum 55cm-A .
ymmetric COO- stretchin.
, and amount of analyte in the smallest possible 54 cm-A (C-O-C glycosidic bon.
These volume to ensure the highest sensitivity for bands are consistent with the established UV-Vis (Yantyana et al.
, 2.
The presence of these Increasing calcium-crosslinked volume beyond 3 mL resulted in a decrease in the measured concentration due to the dilution biopolymers extracted from seaweed, which effect, where the total mass of the desorbed are characterized by a high density of carboxyl metal is distributed across a larger volume of and hydroxyl sites as the primary points for liquid (Wang et al.
, 2019.
Pratiwi et al.
, 2.
metal binding (Kamisyah et al.
, 2.
This efficiency in using a small volume of eluent Figure 8.
FT-IR characterization of (A) Ca-Alg microcapsules and (B) Ca-Alg-EDTA microcapsules KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
Table 1.
Comparison of Ca-Alg and Ca-Alg-EDTA Microcapsule Spectra Functional Group Reference Wave Number Range .
OOeH
C=O
COeOOeC
Literature Identified Results Ca-Alg
Ca-Alg-EDTA
Coe
COeH
NOeH
COeN
Significant Yantyana et
, 2018
Wang et al.
absorption bands were observed following the integrated into the polymer matrix, providing the necessary active sites for Cr(VI) chelation.
incorporation of EDTA.
The emergence of a sharp peak at 1733.
02 cm-A is attributed to the C=O stretching of the carboxylic acid or ester/amide groups from the EDTA molecule.
Validation of Analytical Method Linearity.
LoD, and LoQ The Cr(VI) The shift of the COO- band from 1411.
55 cm-A quantification was established both before and 07 cm-A indicates a change in the after the preconcentration step (Figure .
The chemical environment linear range was observed between 0.
01 and the carboxylate 5 mg/L.
Before Preconcentration: y = intercalation between the EDTA ligands and the 4899x 0.
0114 (R2 = 0.
and After alginate backbone Preconcentration: y = 2.
0107 (R 2 =
(Wang et al.
, 2.
Furthermore, the disappearance of the broad O-H band and the appearance of a new band The increase in the slope .
after 72 cm-A (N-H stretchin.
, coupled with the C-N stretching at 1273.
49 cm-A, confirms the effectiveness of the Ca-Alg-EDTA column in formation of amide linkages.
This indicates that enriching the analyte.
The R2 values exceeding the amino groups of EDTA reacted with the 999 indicate excellent linearity according to carboxylate groups of the alginate via a Riyanto .
As shown in Table 2, the LoD condensation-like 014 mg/L, and the LoQ was 0.
046 mg/L.
microencapsulation process.
These spectral These low values confirm that the method is changes provide robust evidence for the sufficiently sensitive to monitor trace levels of successful synthesis of the Ca-Alg-EDTA Cr(VI) in environmental waters that typically fall hybrid material, where the EDTA ligands are below the direct detection limit of UV-Vis KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
Figure 9.
Determination of Cr(VI) standard solution calibration curve Table 2.
LoD and LoQ test results Calculation Result c Oe ycyc.
2 2,63 UI 10-4
Standard Deviation (SD) 8,1 UI 10-3
LOD
0,014 mg/L LOQ 0,046 mg/L Precision and accuracy the Horwitz CV .
redicted % RSD based on The precision was evaluated using the This indicates that the method Relative Standard Deviation (%RSD) from ten is highly reproducible even at the lowest tested As presented in Table 3, the % RSD concentration .
01 mg/L).
096 % Ae 5.
74 %) were all lower than Table 3.
Precision test results Standard .
g/L) ycu
%RSD
691UI10-3
Horwitz CV represents the maximum Horwitz 6 % and 93.
94 %, which comply with the AOAC .
acceptance criteria of concentration level.
values below this limit 80Ae110 %.
This confirms that the Ca-Alg-EDTA indicate acceptable method reproducibility.
microcapsules do not introduce significant Accuracy was assessed through a spikerecovery test across three concentration levels systematic errors during the adsorption-elution (Table .
The results yielded recoveries KOVALEN: Jurnal Riset Kimia, 11.
, 2025: 94-105 Lianasari et al.
Table 4.
Accuracy test results yc ycycn Standard .
g/L) ycu Recovery Real sample application and matrix To evaluate potential matrix effectsAisuch The developed method was applied to Mg2 , or organic matte.
in the river waterAia Mahakam River water samples.
The detected as interference from other dissolved ions (Fe3 , spike of 0.
5 mg/L Cr(VI) was added.
Cr(VI) concentration was 0.
0877 mg/L (Table Table 5.
Results of Cr(VI) concentration determination in a real sample Sample Mahakam River Water Ci .
g/L) C Eluat .
g/L) % Recovery The recovery for the real sample was 05 %, which is well within the acceptable mg/L and excellent recovery .
05 %) in complex Mahakam River water samples.
This high recovery suggests that the Ca- The novelty of this work lies in the Alg-EDTA microcapsules possess excellent selectivity for Cr(VI), effectively isolating the microencapsulation within a column system to target analyte from the complex river water bridge the sensitivity gap of standard UV-Vis However, this study has This effectiveness in trace metal limitations, particularly the absence of long- enrichment from river term reusability assessments and detailed consistent with the performance of chelating kinetic modeling to fully understand the systems reported in earlier preconcentration adsorption rate.
Furthermore, while the material studies (Amran et al.
, 2.
cost-effective, biopolymer-based comparison with commercial ion-exchange CONCLUSION This resins remains to be explored.
Future research should focus on Scanning sensitive and eco-friendly preconcentration Electron Cr(VI) Microscopy (SEM) optimized Ca-Alg-EDTA microcapsules.
The modeling to clarify the energetic distribution of integration of EDTA into the alginate matrix binding sites, and testing the resinAos stability over multiple adsorption-desorption cycles.
coordination sites, achieving a maximum Ultimately, these Ca-Alg-EDTA microcapsules retention capacity of 0.
3995 mg/g and an offer a promising, sustainable alternative for the efficiency of 74.
73 %.
The method proved routine detection of toxic heavy metals in highly reliable for environmental monitoring, as natural water systems.
demonstrated by the low detection limit .
Lianasari et al.
REFERENCES