Synthesis and application of a carbamazepine-imprinted polymer for solid-phase extraction from urine and wastewater

A molecularly imprinted polymer (MIP) designed to enable the selective extraction of carbamazepine (CBZ) from effluent wastewater and urine samples has been synthesised using a non-covalent molecular imprinting approach. The MIP was evaluated chromatographically in the first instance and its affinity for CBZ also confirmed by solid-phase extraction (SPE). The optimal conditions for SPE consisted of conditioning of the cartridge using acidified water purified from a Milli-Q system, loading of the sample under basic aqueous conditions, clean-up using acetonitrile and elution with methanol. The attractive molecular recognition properties of the MIP gave rise to good CBZ recoveries (80%) when 100 mL of effluent water spiked with 1 μg L⁻¹ was percolated through the polymer. For urine samples, 2 mL samples spiked with 2.5 μg L⁻¹ CBZ were extracted with a recovery of 65%. For urine, the linear range was 0.05-24 mg L⁻¹, the limit of detection was 25 μg L⁻¹ and precision, expressed as relative standard deviation at 0.5 mg L⁻¹ (n = 3), was 3.1% and 12.6% for repeatability and reproducibility between days, respectively.     

Novel catalytic oxidative coupling reaction of N,N-dimethyl-p-phenylenediamine with 1,3-phenylenediamine and its applications to the determination of copper and iron at trace levels by flow injection technique

A new catalytic oxidative coupling reaction of N,N-dimethyl-p-phenylenediamine (DPD) with 1,3-phenylenediamine (mPD) in the presence of hydrogen peroxide has been developed for trace metals analysis. The rate of the oxidation/coupling reaction can be enhanced significantly by iron, copper and cobalt. These metal ions can catalyze the oxidation reaction of DPD to form an oxidized product; the oxidized DPD was then coupled with mPD to give a blue-colored product which was measured spectrophotometrically at 650 nm. On the basis of such a reaction scheme, two simple flow injection analysis methods for the determination of copper and iron have been developed. Detailed studies on chemical and FIA variables affecting the sensitivity of the detection were carried out. Interferences from several ionic species were examined for the determination of copper: the interference effect by Fe(III) and Fe(II) up to 1.5 mg L⁻¹ was successfully suppressed by pretreating sample with ammonium acetate buffer solution (pH 8.4). Good linearity of a standard calibration graph was obtained over the ranges of 0-8 and 0-2 μg L⁻¹ of copper and iron, respectively, and the detection limits were 0.05 and 0.02 μg L⁻¹ for copper and iron, respectively. The precision of the methods in terms of relative standard deviation were 1.4 and 1.5% of R.S.D. which were obtained from 10 injections of 2.0 and 1.0 μg L⁻¹ of standard copper and iron, respectively. The proposed methods were successfully applied to the determination of copper and iron in tap and river water samples. The accuracy of the proposed methods was assessed by the analysis of certified reference material of river water.     

Voltammetric determination of Se(IV) and Se(VI) in saline samples—Studies with seawater, hydrothermal and hemodialysis fluids

Determination of Se(IV) and Se(VI) in high saline media was investigated by cathodic stripping voltammetry (CSV). The voltammetric method was applied to assay selenium in seawater, hydrothermal and hemodialysis fluids. The influence of ionic strength on selenium determination is discussed. The CSV method was based on the co-electrodeposition of Se(IV) with Cu(II) ions and Se(VI) determined by difference after sample UV-irradiation for photolytic selenium reduction. UV-irradiation was also used as sample pre-treatment for organic matter decomposition. Detection limit of 0.030 μg L⁻¹ (240 s deposition time) and relative standard deviation (RSD) of 6.19% (n = 5) for 5.0 μg L⁻¹ of Se(IV) were calculated. Linear calibration range for selenium was observed from 1.0 to 100.0 μg L⁻¹. Concerning the pre-treatment step, best results were obtained by using 60 min UV-irradiation interval in H₂O₂/HCl medium. Se(VI) was reduced to the Se(IV) electroactive species with recoveries between 91.7% and 112.9%. Interferents were also investigated.     

Headspace liquid-phase microextraction using ionic liquid as extractant for the preconcentration of dichlorodiphenyltrichloroethane and its metabolites at trace levels in water samples

A novel technique, high temperature headspace liquid-phase microextraction (HS-LPME) with room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]) as extractant, was developed for the analysis of dichlorodiphenyltrichloroethane (p,p′-DDT and o,p′-DDT) and its metabolites including 4,4′-dichlorodiphenyldichloroethylene (p,p′-DDE) and 4,4′-dichlorodiphenyldichloroethane (p,p′-DDD) in water samples by high performance liquid chromatography with ultraviolet detection. The parameters such as salt content, sample pH and temperature, stirring rate, extraction time, microdrop volume, and sample volume, were found to have significant influence on the HS-LPME. The conditions optimized for extraction of target compounds were as follows: 35% NaCl (w/v), neutral pH condition, 70 °C, 800 rpm, 30 min, 10 μL [C₄MIM][PF₆], and 25 mL sample solutions. Under the optimized conditions, the linear range, detection limit (S/N = 3), and precision (R.S.D., n = 6) were 0.3-30 μg L⁻¹, 0.07 μg L⁻¹, and 8.0% for p,p′-DDD, 0.3-30 μg L⁻¹, 0.08 μg L⁻¹, and 7.1% for p,p′-DDT, 0.3-30 μg L⁻¹, 0.08 μg L⁻¹, and 7.2% for o,p′-DDT, and 0.2-30 μg L⁻¹, 0.05 μg L⁻¹, and 6.8% for p,p′-DDE, respectively. Water samples including tap water, well water, snow water, reservoir water, and wastewater were analyzed by the proposed procedure and the recoveries at 5 μg L⁻¹ spiked level were in the range of 86.8-102.6%.     

Sensitive determination of hydrazine in water by gas chromatography–mass spectrometry after derivatization with ortho-phthalaldehyde

A gas chromatography–mass spectrometric (GC–MS) method has been established for the determination of hydrazine in drinking water and surface water. This method is based on the derivatization of hydrazine with ortho-phthalaldehyde (OPA) in water. The following optimum reaction conditions were established: reagent dosage, 40 mg mL⁻¹ of OPA; pH 2; reaction for 20 min at 70 °C. The organic derivative was extracted with methylene chloride and then measured by GC–MS. Under the established condition, the detection and the quantification limits were 0.002 μg L⁻¹ and 0.007 μg L⁻¹ by using 5.0-mL of surface water or drinking water, respectively. The calibration curve showed good linearity with r² = 0.9991 (for working range of 0.05–100 μg L⁻¹) and the accuracy was in a range of 95–106%, and the precision of the assay was less than 13% in water. Hydrazine was detected in a concentration range of 0.05–0.14 μg L⁻¹ in 2 samples of 10 raw drinking water samples and in a concentration range of 0.09–0.55 μg L⁻¹ in 4 samples of 10 treated drinking water samples.     

Bioreduction of methyl o-chlorobenzoylformate at 500 g L without external cofactors for efficient production of enantiopure clopidogrel intermediate

Biocatalytic reduction of methyl o-chlorobenzoylformate (CBFM) provides a green and direct access to methyl (R)-o-chloromandelate [(R)-CMM], an intermediate for a platelet aggregation inhibitor named clopidogrel. As much as 500 g L⁻¹ of CBFM was stoichiometrically converted into enantiopure (R)-CMM at 20 °C by using a whole-cell catalyst coexpressing an aldo-keto reductase from Bacillus sp. and a glucose dehydrogenase (GDH). In addition to the high productivity of 812 g L⁻¹ d⁻¹, this new whole-cell reduction is attractive by eliminating the need of an added external cofactor.     

Determination of cadmium in alcohol fuel using Moringa oleifera seeds as a biosorbent in an on-line system coupled to FAAS

In this study a new method for determination of cadmium in alcohol fuel using Moringa oleifera seeds as a biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. Flow and chemical variables of the proposed system were optimized through multivariate designs. The limit of detection for cadmium was 5.50 μg L⁻¹ and the precision was below 2.3% (35.0 μg L⁻¹, n = 9). The analytical curve was linear from 5 to 150 μg L⁻¹, with a correlation coefficient of 0.9993. The developed method was successfully applied to spiked alcohol fuel, and accuracy was assessed through recovery tests, with recovery ranging from 97.50 to 100%.     

DRC™ ICP-MS coupled with automated flow injection system with anion exchange minicolumns for determination of selenium compounds in water samples

A flow injection system with anion exchange resin minicolumns was coupled with dynamic reaction cell (DRC™) ICP-MS for the determination and speciation of selenite and selenate at sub μg L⁻¹ levels. The charged selenate and uncharged selenite were separated on the first resin column in which only selenate was retained. The unretained selenite was then deprotonated with alkaline solution, and the resulting anionic selenite species was collected on the second column serially connected downstream. By setting a sample loop, total selenium can be determined together with selenite and selenate. The selenium species was eluted by nitric acid and carried to DRC™ ICP-MS for their detection. Using ammonia as reaction gas, the detection of ⁷⁸Se was improved. The enrichment factor was 20 for 10 mL of sample. The standard deviations (n = 5) of peak heights were 4.9%, 4.1%, and 7.0% for a 5.0 × 10⁻² μg L⁻¹ selenite and selenate, and total Se, respectively. The calibration graphs were linear from 2.0 × 10⁻² to 1.0 μg L⁻¹ selenite and selenate. And, the linearity for total selenium was good in the range of 10.0 × 10⁻² to 1.0 μg L⁻¹. The proposed method has been demonstrated for the application to natural and bottled drinking water samples.     

Liquid-phase microextraction and fibre-optics-based cuvetteless CCD-array micro-spectrophotometry for trace analysis

Liquid-phase microextraction (LPME) has been investigated for trace analysis in the present work in conjunction with fibre-optic-based micro-spectrophotometry which accommodates sample volume of 1 μL placed between the two ends of optical fibres. Methods have been evolved for the determination of (i) 1-100 μM and 0.5-20 μM of thiols by single drop microextraction (SDME) and LPME in 25 μL of the organic solvent, respectively, involving their reaction with the Ellman reagent and ion pair microextraction of thiolate ion formed; (ii) 70 μg to 7 mg L⁻¹ of chlorine/chlorine dioxide by headspace in-drop reaction with alternative reagents, viz., mixed phenylhydrazine-4-sulphonic acid and N-(1-naphthyl)ethylenediamine dihydrochloride, o-dianisidine, o-tolidine, and N,N-diethyl-p-phenylenediamine; (iii) 0.2-4 mg L⁻¹ of ammonia by reaction with 2,4-dinitro-1-fluorobenzene to give 2,4-dinitroaniline which was diazotized and coupled with 1-naphthylamine, the resulting dye was subjected to preconcentration by solid-phase extraction and LPME; and (iv) 25-750 μg L⁻¹ of iodide/total iodine by oxidation of iodide by 2-iodosobenzoate, microextraction of iodine in organic solvent, and re-extraction into aqueous starch-iodide reagent drop held in the organic phase. LPME using 25-30 μL of organic solvent was found to produce more sensitive results than SDME. The cuvetteless spectrophotometry as used in combination with sample handling techniques produced limits of detection of analytes which were better than obtained by previously reported spectrophotometry.     

Development of a sensitive and selective kojic acid sensor based on molecularly imprinted polymer modified electrode in the lab-on-valve system

In this work, a kojic acid electrochemical sensor, based on a non-covalent molecularly imprinted polymer (MIP) modified electrode, had been fabricated in the lab-on-valve system. The sensitive layer was synthesized by cyclic voltammetry using o-phenylenediamine as the functional monomer and kojic acid as the template. The template molecules were then removed from the modified electrode surface by washing with NaOH solution. Differential pulse voltammetry method using ferricyanide as probe was applied as the analytical technique, after extraction of kojic acid on the electrode. Chemical and flow parameters associated with the extraction process were investigated. The response recorded with the imprinted sensor exhibited a response in a range of 0.01-0.2 μmol L⁻¹ with a detection limit of 3 nmol L⁻¹. The interference studies showed that the MIP modified electrode had excellent selectivity. Furthermore, the proposed MIP electrode exhibited good sensitivity and low sample/reagent consumption, and the sensor could be applied to the determination kojic acid in cosmetics samples.     

The use of a polymer inclusion membrane for separation and preconcentration of orthophosphate in flow analysis

A highly sensitive flow analysis system has been developed for the trace determination of reactive phosphate in natural waters, which uses a polymer inclusion membrane (PIM) with Aliquat 336 as the carrier for on-line analyte separation and preconcentration. The system operates under flow injection (FI) and continuous flow (CF) conditions. Under optimal FI conditions the system is characterised by a linear concentration range between 0.5 and 1000 μg L⁻¹ P, a sampling rate of 10 h⁻¹, a limit of detection of 0.5 μg L⁻¹ P and RSDs of 3.2% (n = 10, 100 μg L⁻¹) and 7.7% (n = 10, 10 μg L⁻¹). Under CF conditions with 10 min stop-flow time and sample solution flow rate of 1.32 mL min⁻¹ the flow system offers a limit of detection of 0.04 μg L⁻¹ P, a sampling rate of 5 h⁻¹ and an RSD of 3.4% (n = 5, 2.0 μg L⁻¹). Interference studies revealed that anions commonly found in natural waters did not interfere when in excess of at least one order of magnitude. The flow system, operating under CF conditions, was successfully applied to the analysis of natural water samples containing concentrations of phosphate in the low μg L⁻¹ P range, using the multipoint standard addition method.     

Solid-phase spectrophotometric determination of nickel in water and vegetable samples at sub-mug l(-1) level with o-carboxylphenyldiazoaminoazobenzene loaded XAD-4

A highly sensitive and selective solid-phase spectrophotometric method for the determination of sub-μg l⁻¹ level nickel(II) is described. Nickel(II) was sorbed on a styrene-divinylbenzene-type resin Amberlite XAD-4 as a Ni(II)-o-carboxylphenyldiazoaminoazobenzene (o-CDAA) complex. At pH 9.0, resin phase absorbances at 588 and 800 nm were measured directly with an apparent molar absorptivity of 2.95×10⁷ g mol⁻¹ cm⁻¹. The linear range of the determination was 1.2-41 μg g⁻¹ resin. The detection limit and the quantification limit were found to be 0.24 and 0.76 μg g⁻¹ resin, respectively. The relative standard deviation of 10 replicate determinations of 1.0 μg nickel(II) in 100 ml sample was of 1.5%. The tolerance limit of coexistent ions was also investigated. Most of them are in tolerable amount. For practical analyses, 1 ml acetylacetone used can eliminate the interferences caused by Cu and Fe. The procedure was validated by analysis a certified water reference material (GBW 08618 Beijing, China) and a tomato leaf certified reference material (GBW 08402 Beijing, China) with the results in agreement with the certified values. The method was applied to the determination of nickel(II) in water and vegetable samples with satisfactory results.     

Synthesis of three haptens for the class-specific immunoassay of O,O-dimethyl organophosphorus pesticides and effect of hapten heterology on immunoassay sensitivity

A general and broad class-specific enzyme-linked immunosorbent assay was developed for the O,O-dimethyl organophosphorus pesticides, including malathion, dimethoate, phenthoate, phosmet, methidathion, fenitrothion, methyl parathion and fenthion. Three haptens with different spacer-arms were synthesized. The haptens were conjugated to bovine serum albumin (BSA) for immunogens and to ovalbumin (OVA) for coating antigens. Rabbits were immunized with the immunogens and six polyclonal antisera were produced and screened against each of the coating antigens using competitive indirect enzyme-linked immunosorbent assay for selecting the proper antiserum. The effect of hapten heterology on immunoassay sensitivity was also studied. The antibody-antigen combination with the most selectivity for malathion was further optimized and tested for tolerance to co-solvent, pH and ionic strength changes. The IC₅₀ values, under optimum conditions, were estimated to be 30.1 μg L⁻¹for malathion, 28.9 μg L⁻¹ for dimethoate, 88.3 μg L⁻¹ for phenthoate, 159.7 μg L⁻¹ for phosmet, 191.7 μg L⁻¹ for methidathion, 324.0 μg L⁻¹ for fenitrothion, 483.9 μg L⁻¹ for methyl parathion, and 788.9 μg L⁻¹ for fenthion. Recoveries of malathion, dimethoate, phenthoate, phosmet and methidathion from fortified Chinese cabbage samples ranged between 77.1% and 104.7%. This assay can be used in monitoring studies for the multi-residue determination of O,O-dimethyl organophosphorus pesticides.     

Flow injection determination of aluminium by spectrofluorimetric detection after complexation with N-o-vanillidine-2-amino-p-cresol: the application to natural waters

An on-line flow injection spectrofluorimetric method for the direct determination of aluminium in water samples is described. The method is based on the reaction of aluminium with N-o-vanillidine-2-amino-p-cresol (OVAC) in acidic medium at pH 4.0 to form a water-soluble complex. The excitation and emission wavelengths were 423.0 and 553.0 nm, respectively, at which the OVAC-Al complex gave the maximum fluorescence intensity at pH 4.0 in a 50% methanol-50% water medium at 50 °C. An interference from fluoride ions was minimised by the addition of Be²⁺. Other ions were found not to interfere at the concentrations likely to be found in natural waters. The proposed methods were validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. Under these conditions, the calibration was linear up to 1000 μg L⁻¹ (r = 0.999). The limit of detection (3σ) for the determination of Al(III) was 0.057 μg L⁻¹ and the precision for multiple determinations of 3 ng mL⁻¹ Al(III) prepared in ultra-pure water was found to be 0.62% (n = 10).The Schiff base ligand could be used to determine ultra-trace aluminium from natural waters. Analysis of environmental certified reference materials showed good agreement with the certified values. The procedure was found to be equally applicable to both freshwater and saline solutions, including seawater.     

On-line sorptive preconcentration platform incorporating a readily exchangeable Oasis HLB extraction micro-cartridge for trace cadmium and lead determination by flow injection-flame atomic absorption spectrometry

A simple, sensitive and inexpensive flow injection solid phase extraction (SPE) system was developed for automatic determination of trace level concentrations of metals. The potentials of this novel scheme, coupled to flame atomic absorption spectrometry (FAAS), were demonstrated for trace cadmium and lead determination in environmental water samples. The method was based on on-line chelate complex formation of target species with ammonium diethyldithiophosphate (DDTP), retention onto the surface of reversed-phase poly(divinylbenzene-N-vinylpyrrolidone) co-polymeric beads (Oasis HLB) and elution with methanol prior to atomization. A special PVC adapter was designed for easy and rapid replacement of the commercially available SPE cartridge. All main chemical and hydrodynamic parameters affecting the complex formation, sorption and elution of the analyte were optimized thoroughly. Moreover, the effect of potential interfering species occurring in environmental samples was also explored.For 90 s preconcentration time, enhancement factors of 155 and 180, detection limits (3s) of 0.09 μg L^− 1 and 0.9 μg L^− 1 and relative standard deviations (R.S.D.) of 2.9% (at 4.0 μg L^− 1) and 2.6% (at 20.0 μg L^− 1) were obtained for cadmium and lead, respectively, with a sample throughput of 24 h^− 1. The measurement trueness of the developed method was evaluated by analyzing a certified reference material and spiked environmental water samples. The proposed method is well suited to detect the target elements at concentration levels below the maximum allowed concentrations endorsed by the European Framework Directive (2008/105/EC) in inland and coastal waters.     

On-line solid phase extraction system using 1,10-phenanthroline immobilized on surfactant coated alumina for the flame atomic absorption spectrometric determination of copper and cadmium

An on-line solid phase extraction (SPE) preconcentration system coupled to flame atomic absorption spectrometer (FAAS) was developed for determination of copper and cadmium at μg L⁻¹ level. The method is based on the on-line retention of copper and cadmium on a microcolumn of alumina modified with sodium dodecyl sulfate (SDS) and 1,10-phenanthroline and subsequent elution with ethanol and determination by FAAS. The effect of chemical and flow variables that could affect the performance of the system was investigated. The relative standard deviation (n = 6) at 20 μg L⁻¹ level for copper and cadmium were 1.4 and 2.2% and the corresponding limits of detection (based on 3σ) were 0.04 and 0.14 μg L⁻¹, respectively. The method was successfully applied to determination of copper and cadmium in human hair and water samples.     

Montmorillonite as an adsorbent for extraction and concentration of atrazine, propazine, deethylatrazine, deisopropylatrazine and hydroxyatrazine

Adsorption properties of the clay mineral montmorillonite in the potassium homoionic form (KMT) was investigated to achieve the extraction and concentration of the herbicides atrazine (AT) and propazine (PROP), as well as the main degradation products of atrazine, namely deethylatrazine (DEA), deisopropylatrazine (DIA) and hydroxyatrazine (ATOH). A batch approach was proposed, with recovery percentages for AT, PROP and DIA higher than 90% at concentrations of 0.50 and 2.50 μg L⁻¹. For DEA and ATOH, however, low recoveries were obtained. For DEA, this fact can be explained by its low K_d with KMT, contrary to ATOH, which interacts strongly with the mineral surface, hindering the complete desorption and hence, generating low recovery percentages. The influence of pH, ionic strength and humic acid was studied, and a comparison with the C₁₈ phase as SPE cartridges was carried out. Montmorillonite showed a similar performance to commercial cartridge for concentrations of AT, DEA and PROP, but better recoveries for DIA was obtained using the clay mineral. For ATOH the recovery was also higher on the clay mineral, although for this compound the most suitable SPE cartridge is constituted by cation exchange resin. After the concentration and elution steps, the 0.50 and 2.50 μg L⁻¹ gave chromatographic peak areas that could be easily quantified with an analytical curve obtained in the concentration range between 7.5 and 100 μg L⁻¹. The obtained concentration factors are suitable to allow the application of the method to the monitoring of triazine residues in drinking water.     

Speciation analysis of mercury in sediments, zoobenthos and river water samples by high-performance liquid chromatography hyphenated to atomic fluorescence spectrometry following preconcentration by solid phase extraction

A high-pressure microwave digestion was applied for microwave-assisted extraction (MAE) of mercury species from sediments and zoobenthos samples. A mixture containing 3 mol L⁻¹ HCl, 50% aqueous methanol and 0.2 mol L⁻¹ citric acid (for masking co-extracted Fe³⁺) was selected as the most suitable extraction agent. The efficiency of proposed extraction method was better than 95% with R.S.D. below 6%. A preconcentration method utilizing a “homemade” C18 solid phase extraction (SPE) microcolumns was developed to enhance sensitivity of the mercury species determination using on-column complex formation of mercury-2-mercaptophenol complexes. Methanol was chosen for counter-current elution of the retained mercury complexes achieving a preconcentration factor as much as 1000. The preconcentration method was applied for the speciation analysis of mercury in river water samples. The high-performance liquid chromatography-cold vapour atomic fluorescence spectrometric (HPLC/CV-AFS) method was used for the speciation analysis of mercury. The complete separation of four mercury species was achieved by an isocratic elution of aqueous methanol (65%/35%) on a Zorbax SB-C18 column (4.6 mm × 150 mm, 5 μm) using the same complexation reagent (2-mercaptophenol). The limits of detection were 4.3 μg L⁻¹ for methylmercury (MeHg⁺), 1.4 μg L⁻¹ for ethylmercury (EtHg⁺), 0.8 μg L⁻¹ for inorganic mercury (Hg²⁺), 0.8 μg L⁻¹ for phenylmercury (PhHg⁺).     

Cell-sorption of paramagnetic metal ions on a cell-immobilized micro-column in the presence of an external magnetic field

The cell-sorption of paramagnetic ions of Mn²⁺ and Cr³⁺ onto a Chlorella vulgaris(C. vulgaris) cell-immobilized micro-column was significantly improved in the presence of an external magnetic field generated in a finite solenoid, by placing the micro-column in the center of the solenoid in a sequential injection system. Magnetic field creates an opposite drift velocity on the hydrated paramagnetic ions against the flow of the sample zone, retards the moving velocity of the metal ions and provides extra contacting time with the cells on the micro-column and offers more chances for the paramagnetic ions to interact with the various functional groups or binding sites on the cell surface, which significantly facilitates cell-sorption of the paramagnetic ions. The sorption efficiencies of Mn²⁺ and Cr³⁺ at the 20 μg L⁻¹ level were improved from 45 to 80% and 60 to 90%, respectively, in a magnetic field of 240 mT.The system was applied for the separation/preconcentration of ultra-trace level of manganese. The presence of an external magnetic field significantly alleviated the interfering effects from coexisting metal ions. Within a liner range of 0.025-0.5 μg L⁻¹ and a sampling volume of 500 μL, an enrichment factor of 21.2, a limit of detection of 0.008 μg L⁻¹, along with a sampling frequency of 20 h⁻¹ was attained, achieving a precision of 2.1% R.S.D. (0.2 μg L⁻¹). Manganese contents in a certified reference material of riverine water and a snow water were analyzed.