Quantitative description of element concentrations in longitudinal river profiles by multiway PLS models

Partial least squares (PLS) models were used to examine the relationships between the distributions of elements in different compartments of a river. These relationships, if existing, enabled predictions to be made of the element concentrations in one compartment by knowing the concentrations in another compartment. The subjects of the study were the element concentrations measured in the water and the sediment of the river Saale as well as in the water and the suspended matter of the river Elbe. Special emphasis was placed on a comparison between two-way and three-way PLS.     

Assessing the deposition and remobilisation behaviour of metals between river water and river sediment using partial least squares regression

Partial least squares regression (PLS) as a method for multivariate data analysis has been applied to environmental data of the German rivers Saale, Ilm and Unstrut. Main aspects of the study are to describe the relationships of the distribution of metals between river water and river sediment using PLS. A simulation of the distribution of metals between the liquid and solid phase by variation of some parameters (e.g. conductivity, DOC, dissolved oxygen, pH, phosphate and suspended matter) is presented and compared with experimental results. Received: 15 July 1997 / Revised: 6 November 1997 / Accepted: 7 November 1997     

Assessing the deposition and remobilisation behaviour of metals between river water and river sediment using partial least squares regression

Partial least squares regression (PLS) as a method for multivariate data analysis has been applied to environmental data of the German rivers Saale, Ilm and Unstrut. Main aspects of the study are to describe the relationships of the distribution of metals between river water and river sediment using PLS. A simulation of the distribution of metals between the liquid and solid phase by variation of some parameters (e.g. conductivity, DOC, dissolved oxygen, pH, phosphate and suspended matter) is presented and compared with experimental results.     

Determination of human serum albumin and γ-globulin in a control serum solution by near-infrared spectroscopy and partial least squares regression

Near infrared (NIR) spectra in the 1300– 1850 nm region were measured for control serum solutions containing both albumin and γ-globulin of various concentrations. Partial least squares two (PLS2) regression was applied to the NIR spectra to determine simultaneously the concentrations of both proteins. For albumin, the correlation coefficient (R) of 0.988, the standard error of calibration (SEC) of 1.61 g/L, the standard error of prediction (SEP) of 1.29 g/L, the relative standard deviation (RSD) of 0.026 and the ratio of standard deviation of reference data in prediction to SEP (RPD) of 12.2 were obtained. For γ-globulin, the corresponding values were 0.997, 1.36 g/L, 1.35 g/L, 0.0365 and 8.66, respectively. The regression coefficients (RCs) of PLS factors were compared between albumin and γ-globulin, and the observed differences in the RCs were discussed based upon the differences in the hydration between albumin and γ-globulin. In order to explore the effects of various metabolites such as glucose, and cholesterol on the chemometrics models, the RCs for albumin and γ-globulin in the control serum solutions were also compared with those for albumin and γ-globulin in phosphate buffer solutions previously studied. The results of our experiments show that NIR spectroscopy with the use of PLS2 regression has considerable promise in nondestructive determination of the concentrations of blood serum proteins. Received: 31 December 1997 / Revised: 9 April 1998 / Accepted: 27 April 1998     

Quantitative Analysis of Chromium(VI) in Dilute Solution by Using Adsorption and Diffuse Reflectance Near‐infrared Spectroscopy

A method for quantitative determination of metal element in aqueous solution was developed by using adsorption and diffuse reflectance near‐infrared spectroscopy (DRNIRS). In this method, the analyte is firstly adsorbed onto the resin from the dilute solution, and then the adsorbed analyte is directly determined in the sorbent by using DRNIRS. Enrichment of the analyte is achieved by the adsorption from the dilute solution, and quantitative determination is accomplished by using multivariate calibration technique. Taking chromium(VI) in river water as the analytical target, adsorption conditions and the partial least squares (PLS) model was optimized. The results show that chromium(VI) can be immobilized onto the adsorbent and quantitatively measured by DRNIRS and multivariate calibration. With cross validation and external validation, the correlation coefficient between the reference and predicted concentration was found to be above 0.98 in the range of 0.75–29.90 mg·L⁻¹ for the PLS model, and the interference of the coexisting matrix was eliminated with the aid of multivariate calibration.     

Determination of naphthalenesulfonates in water by on-line ion-pair solid-phase extraction and ion-pair liquid chromatography with fast-scanning fluorescence detection

A fast analytical method for quantifying a mixture of 12 naphthalenesulfonates and naphthalenedisulfonates has been developed. This method consists of on-line ion-pair solid-phase extraction with PLRP-s sorbent and ion-pair liquid-chromatography using fast-scanning fluorescence spectrometer as a detection system and multivariate calibration. As complete separation is unnecessary, the compounds were analysed in isocratic conditions and the chromatographic analysis took only 25 min. Three-way partial least-squares (PLS) was used to carry out multivariate calibration for spiked tap water. In these conditions, quantification limits were between 0.01 and 3 μg l⁻¹. Repeatability was also evaluated and relative standard deviations (n=3) were between 0.5 and 4, depending on the compound. Finally, spiked tap and Ebro river waters were analysed to evaluate prediction capability of the method.     

Simultaneous Anodic Stripping Voltammetric Determination of Pb and Cd,Using a Vibrating Gold Microwire Electrode,Assisted by Chemometric Techniques

Simultaneous anodic stripping voltammetric determination of Pb and Cd is restricted on gold electrodes as a result of the overlapping of these two peaks. This work describes the quantitative determination of a binary mixture system of Pb and Cd, at low concentration levels (up to 15.0 and 10.0 µg L^?1 for Pb and Cd, respectively) by differential pulse anodic stripping voltammetry (DPASV; deposition time of 30 s), using a green electrode (vibrating gold microwire electrode) without purging in a chloride medium (0.5 M NaCl) under moderate acidic conditions (HCl 1.0 mM), assisted by chemometric tools. The application of multivariate curve resolution alternating least squares (MCR‐ALS) for the resolution and quantification of both metals is shown. The optimized MCR‐ALS models showed good prediction ability with concentration prediction errors of 12.4 and 11.4 % for Pb and Cd, respectively. The quantitative results obtained by MCR‐ALS were compared to those obtained with partial least squares (PLS) and classical least squares (CLS) regression methods. For both metals, PLS and MCR‐ALS results are comparable and superior to CLS. For Cd, as a result of the peak shift problem, the application of CLS was unsuitable. MCR‐ALS provides additional advantage compared to PLS since it estimates the pure response of the analytes signal. Finally, the built up multivariate calibration models, based either in MCR‐ALS or PLS regression, allowed to quantify concentrations of Pb and Cd in surface river water samples, with satisfactory results.     

Determination of antidepressants in surface and waste water samples by capillary electrophoresis with electrospray ionization mass spectrometric detection after preconcentration using off-line solid-phase extraction

A method for the quantitative determination of seven major antidepressants in surface waters and sewage treatment plant effluents by CE using ESI-MS is presented. Calibration curves for the selected analytes were prepared in Milli-Q purified water and Danube river water extract covering a concentration range of at least one order of magnitude. LODs achieved were between 6 and 13 microg/L for Trazodone and 39 and 53 microg/L for Sertraline in the Milli-Q purified water and Danube river water matrix, respectively. For sample preparation eight different SPE materials were investigated. Best results were obtained for a resin based on hydrophilic divinylbenzene (recoveries from Milli-Q purified water 93-96%; from Danube river water 85-99%). Finally, a series of eight sewage treatment plant effluents were investigated with respect to their content in the selected antidepressants. Six of these samples were tested positive for antidepressants, in particular Venlafaxine, Citalopram and Trazodone in concentrations between 36 and 322 ng/L.     

Resolution of Differential Pulse Voltammetric Peaks Using Genetic Algorithm Based Variable Selection‐Partial Least Squares and Principal Component‐Artificial Neural Networks

Differential Pulse Voltammetry has been used for the simultaneous determination of cysteine, tyrosine and trptophan on the unmodified glassy carbon electrode. In the analysis of these analytes in the same samples, the main difficulty is the high degree of overlapping of voltammograms. The relationships between the currents and the concentrations are complex and highly nonlinear. The predictive ability of principal component regression (PCR), partial least squares regression (PLS), genetic algorithm‐partial least squares regression (GA‐PLS) and principal component‐artificial neural networks (PC‐ANNs) were examined for simultaneous determination of three amino acids. For a regression model, everything that could not help in constructing the model may be considered as noise without further specification. PC‐ANN and GA‐PLS use significant data and show superiority over other applied multivariate methods. The proposed method was also applied satisfactorily to determination of analytes in some synthetic samples.     

Simultaneous analysis of riboflavin and aromatic amino acids in beer using fluorescence and multivariate calibration methods

The study demonstrates an application of the front-face fluorescence spectroscopy combined with multivariate regression methods to the analysis of fluorescent beer components. Partial least-squares regressions (PLS1, PLS2, and N-way PLS) were utilized to develop calibration models between synchronous fluorescence spectra and excitation-emission matrices of beers, on one hand, and analytical concentrations of riboflavin and aromatic amino acids, on the other hand. The best results were obtained in the analysis of excitation-emission matrices using the N-way PLS2 method. The respective correlation coefficients, and the values of the root mean-square error of cross-validation (RMSECV), expressed as percentages of the respective mean analytic concentrations, were: 0.963 and 14% for riboflavin, 0.974 and 4% for tryptophan, 0.980 and 4% for tyrosine, and 0.982 and 19% for phenylalanine.     

Isotachophoresis and isotachophoresis--zone electrophoresis separations of inorganic anions present in water samples on a planar chip with column-coupling separation channels and conductivity detection

The use of a poly(methylmethacrylate) chip, provided with two separation channels in the column-coupling (CC) arrangement and on-column conductivity detection sensors, to electrophoretic separations of a group of inorganic anions (chloride, nitrate, sulfate, nitrite, fluoride and phosphate) that need to be monitored in various environmental matrices was studied. The electrophoretic methods employed in this study included isotachophoresis (ITP) and capillary zone electrophoresis (CZE) with on-line coupled ITP sample pretreatment (ITP-CZE). Hydrodynamic and electroosmotic flows of the solution in the separation compartment of the CC chip were suppressed and electrophoresis was a dominant transport process in the separations performed by these methods. ITP separations on the chip provided rapid resolutions of sub-nmol amounts of the complete group of the studied anions and made possible rapid separations and reproducible quantitations of macroconstituents currently present in water samples (chloride, nitrate and sulfate). However, concentration limits of detection attainable under the employed ITP separating conditions (2-3 x 10(-5) mol/l) were not sufficient for the detection of typical anionic microconstituents in water samples (nitrite, fluoride and phosphate). On the other hand, these anions could be detected at 5-7 x 10(-7) mol/l concentrations by the conductivity detector in the CZE stage of the ITP-CZE combination on the CC chip. A sample clean-up performed in the ITP stage of the combination effectively complemented such a detection sensitivity and nitrite, fluoride and phosphate could be reproducibly quantified also in samples containing the macroconstituents at 10(4) higher concentrations. ITP-CZE analyses of tap, mineral and river water samples showed that the CC chip offers means for rapid and reproducible procedures to the determination of these anions in water (4-6 min analysis times under our working conditions). Here, the ITP sample pretreatment concentrated the analytes and removed nanomol amounts of the macroconstituents from the separation compartment of the chip within 3-4 min. Both the ITP and ITP-CZE procedures required no or only minimum manipulations with water samples before their analyses on the chip. For example, tap water samples were analyzed directly while a short degassing of mineral water (to prevent bubble formation during the separation) and filtration of river water samples (to remove particulates and colloids) were the only operations needed in this respect.     

Determination of Cu, Zn and Cd in water by FAAS after preconcentration by baker’s yeast (Saccharomyces cerevisiae) immobilized on sepiolite

By using the adsorbent Saccharomyces cerevisiae immobilized on sepiolite an adsorption-elution method was developed for the preconcentration of Cu, Zn, and Cd followed by flame atomic absorption spectrometry (FAAS). Recoveries were 98.3 ± 0.4% for Cu, 94.2 ± 0.3% for Zn, and 99.04 ± 0.04% for Cd at 95% confidence level obtained by the column method. The influence of sea water matrix elements on the separation of the trace elements was also assessed by using the column procedure. The breakthrough capacities were found to be 74 μmol/g for copper, 128 μmol/g for zinc and 97 μmol/g for cadmium. After optimization the proposed method was applied to the trace metal determination in sea and river water. Received: 8 June 1998 / Revised: 8 September 1998 / Accepted: 16 September 1998     

Determination of binary and ternary mixtures of pesticides in wetland waters by gas chromatography using partial least-squares analysis

Partial least-squares (PLS) analysis was applied for the first time to ternary and binary mixtures of pesticides producing overlapping peaks in gas chromatograms. Several preprocessing algorithms for pretreatment of data were tested for optimization of the PLS models, and the most advantageous were used in each case. Three different mixtures of pesticides were resolved with satisfactory results: parathion-methyl, chlorpyrifos-methyl, and vinclozolin; parathion-ethyl, chlorpyrifos, and triadimefon; and endosulfan sulfate and carbophenothion. The proposed models were applied to the determination of 3 mixtures of pesticides at levels of 0.02-1.00 ng/mL in wetland water samples after a preconcentration step with C18 cartridges, with recoveries ranging from 82.7 to 117.4%. The reported method is sufficiently sensitive to measure pesticide residues at the maximum allowable concentrations given in the European Union Drinking Water Directive.     

Separation of copper (II) ions from humic complexes with oxine-impregnated emulsion globules

A water-in-oil type emulsion containing oxine has been used for the discrimination of copper(II) ions and copper-humic complexes in aqueous solutions. A toluene solution containing oxine and nonionic surfactant (Span-80) was vigorously mixed with 1 mol/L HCl by ultrasonic irradiation. The resulting emulsion was added to water and dispersed by stirring as numerous small globules. Copper(II) ions were quantitatively permeated across the oil layer and incorporated in the tiny droplets of HCl, whereas copper-humic complexes remained in the sample solution. After collecting the dispersed emulsion globules, they were destroyed by heating to segregate the aqueous (HCl) and organic (toluene) phases. The copper in the aqueous phase was determined by graphite-furnace atomic absorption spectrometry (GFAAS). The analytical results agreed with those obtained by the adsorption method, where negatively charged humic complexes were selectively collected on a macroreticular anion exchanger Sephadex A-25 column. The conventional liquid-liquid extraction did not offer a chemical speciation because copper(II) ions and humic complexes were simultaneously extracted into the organic phase. The proposed emulsion method was successfully applied to the analysis of river water samples. Received: 14 April 1998 / Revised: 22 July 1998 / Accepted: 27 July 1998     

Drinking water quality from the aspect of element concentrations

Summary Drinking water in developed countries is usually treated by the water-purification system, while in developing countries untreated natural water such as well water, river water, rain water, or pond water are used. On the other hand, many kinds of mineral water bottled in plastic containers are sold as drinking water with or without gas in urban areas in many countries. Seawater under hundreds meters from the surface is also bottled and sold as drinking water with advertising good mineral balance. Various element concentrations in water samples for drinking were analyzed, and then it was considered the effects of elements on human health.     

Simultaneous Determination of Haloacetic Acids in Environmental Waters using Electrospray Ionization Liquid Chromatography Mass Spectrometry

Negative ionization electrospray liquid chromatography mass spectrometry was developed for the simultaneous determination of all nine haloacetic acids containing bromine and chlorine. Haloacetic acids were separated on a crosslinked polystyrene resin column using 3% acetic acid dissolved in acetonitrile:water (20:80) as mobile phase. The precision of this method varied from ±2.2 to ±7.1% for nine haloacetic acids. In addition, quantitative results obtained with spiked water samples at three different concentrations are described. The limit of detection of the proposed method using 200 mL of water samples was between 0.003 and 0.070 μg/L. This method was successfully applied to the trace determination of haloacetic acids in waste water, river water, and seawater.     

Heavy-metal pollution and its state in algae in Kakehashi river and Godani river at the foot of Ogoya mine, Ishikawa Prefecture.

Alga as Achnanthes minutissima among diatoms is a widely adaptable taxon on the state of an aquatic environment. In this study, it was found that diatom had a specific tolerance to heavy metals (Cu, Zn, Pb, and Cd etc.) in river water samples, because the diatom assemblage consisted of almost only Achnanthes minutissima in Kakehashi river and Godani river, which were polluted with waste water from Ogoya copper mine. The relationship between the concentrations of heavy metals (Cu, Zn, Pb and Cd) in river water and the attached substances (algae and silt etc.) and the relative abundances of diatom taxa were investigated in detail. The results indicated that the higher is the concentration of heavy metals in the river environment, the higher is only the relative abundances of Achnanthes minutissima. Thus, the taxon can be used as a bioindicator of heavy metal pollution. The relative rates of toxic chemical forms of copper in algae were 61 - 92% in the attached substances and 49-70% in the sediment on the river bed, respectively. Therefore, it was found that diatom as Achnanthes minutissima had a tolerance to heavy metals in river water, being able to live in such an environment. Since the water treated with calcium hydroxide from the deposition reservoir of Ogoya mine enters in Godani river, the river is polluted by heavy metals (Cu, Zn, Pb and Cd etc.). From the viewpoint of both biological and chemical analyses, Godani river is still polluted with heavy metals, because their concentrations in the river samples were very high. On the other hand, in Kakehashi river, the concentrations of heavy metals were very low and the distributions of some diatoms appeared in an unpolluted Nishimata river were observed. Therefore, Kakehashi river seems to be considerably recovered from heavy-metal pollution after closing the Ogoya mine.     

Analysis of the spatial distribution of the constituting elements in amorphous solids: Laser ablation with ICP spectrometry

Amorphous materials of the systems Si/B/N/C and Ba/Si/Al/O/C, which are highly resistant against thermal and chemical attack, were analyzed using laser ablation inductively coupled plasma atomic emission (LA-ICP-AES) and mass spectrometry (MS) in order to prove the applicability of these techniques to this special type of materials. Homogeneity was evaluated and the concentrations of the main components were determined with a resolution of 50 μm. A good reproducibility was obtained using one element for internal standardization (0.3–0.7% RSD for Si and Al with Ba as internal standard and about 1.5% for B with Si as internal standard). Scanning white light interferometry employed for the measuring of the crater volumes was tested to support the internal standardization method. Received: 13 May 1998 / Revised: 6 July 1998 / Accepted: 10 July 1998     

Analysis of the spatial distribution of the constituting elements in amorphous solids: Laser ablation with ICP spectrometry

Amorphous materials of the systems Si/B/N/C and Ba/Si/Al/O/C, which are highly resistant against thermal and chemical attack, were analyzed using laser ablation inductively coupled plasma atomic emission (LA-ICP-AES) and mass spectrometry (MS) in order to prove the applicability of these techniques to this special type of materials. Homogeneity was evaluated and the concentrations of the main components were determined with a resolution of 50 μm. A good reproducibility was obtained using one element for internal standardization (0.3–0.7% RSD for Si and Al with Ba as internal standard and about 1.5% for B with Si as internal standard). Scanning white light interferometry employed for the measuring of the crater volumes was tested to support the internal standardization method. Received: 13 May 1998 / Revised: 6 July 1998 / Accepted: 10 July 1998