A Multi-Pumping Gradient Calibration Module for Potentiometric Determination of Nitrate in Surface Water.

The novel, automated, multi-pumping flow system (MPFS) for online calibration and determination of nitrate in surface water is presented for the first time. The system was equipped with micropumps of three different nominal volumes (10, 20, and 50 µL). As a result, it was possible to prepare from one standard, directly in a flow system, up to seven standard solutions. Determination of nitrate was conducted in stop-flow conditions and is based on a commercially available ion selective electrode (ISE) application. It was found that the linearity and slope of the calibration graphs depend mainly on the characteristics of the ISE. The obtained results were very repeatable, owing to the high precision of the micro-pumps used. The R.S.D. for the stroke volume of each micro-pump was below 1%. The accuracy of the method was checked through determination of nitrate in surface water samples. The obtained results were compared with those of the reference method (photometric Hach cuvette tests). It was found that, at a 96% confidence level, the difference between the results obtained by the proposed method and the reference method was statistically insignificant. The accuracy of the method was confirmed through the determination of nitrate in Certified Reference Material. The relative deviation (R.D.) of the measured and the certified concentrations was 5%.

Development of the Microemulsion Electrokinetic Capillary Chromatography Method for the Analysis of Disperse Dyes Extracted from Polyester Fibers.

The study aimed to develop a method for the separation of dispersed dyes extracted from polyester fibers. Nine commercially available disperse dyes, which were used to dye three polyester fabrics, were tested. Extraction of dyes from 1 cm long threads was carried out in chlorobenzene at 100 °C for 6 h. The separation was performed using microemulsion electrokinetic capillary chromatography (MEEKC) with photodiode array detection. Microemulsion based on a borate buffer with an organic phase of n-octane and butanol and a mixture of surfactants, sodium dodecyl sulphate and sodium cholate, were used. The addition of isopropanol and cyclodextrins to microemulsion resulted in a notable improvement in resolution and selectivity. The content of additives was optimized by using the Doehlert experimental design. Values of the coefficient of variance obtained in the validation process, illustrating the repeatability and intermediate precision of the migration times fit in the range of 0.11-1.24% and 0.58-3.21%, respectively. The developed method was also successfully applied to the differentiation of 28 real samples-polyester threads collected from clothing. The obtained results confirmed that proposed method may be used in the discriminant analysis of polyesters dying by disperse dyes and is promisingly employable in forensic practice.

Electrochemical Sensing of Pb2+ and Cd2+ Ions with the Use of Electrode Modified with Carbon-Covered Halloysite and Carbon Nanotubes.

A novel voltammetric method for the sensitive and selective determination of cadmium and lead ions using screen-printed carbon electrodes (SPCEs) modified with carbon-deposited natural halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) was developed. The electrochemical properties of the proposed sensor were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the morphology and structure were established by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). A two-factorial central composite design (CCD) was employed to select the composition of the nanocomposite modifying the electrode surface. The optimal measuring parameters of differential pulse anodic stripping voltammetry (DPASV) used for quantitative analysis were established with the Nelder-Mead simplex method. In the analytical investigation of Cd(II) and Pb(II) ions by DPASV, the MWCNTs/C_Hal/Nafion/SPCE exhibited a linear response in the concentration range of 0.1-10.0 µmol L-1 (for both ions) with a detection limit of 0.0051 and 0.0106 µmol L-1 for Pb(II) and Cd(II), respectively. The proposed sensor was successfully applied for the determination of metal ions in different natural water and honey samples with recovery values of 96.4-101.6%.

Application of Capillary Electromigration Methods in the Analysis of Textile Dyes-Review.

Fiber traces are one of (micro)traces that can be found at a crime scene. They are easily transferable and, like other forms of evidence, can provide a link between a suspect and a victim. The main purpose of this review is to present methods developed to examine textile dyes extracted for forensic purposes using different capillary electromigration methods (CEMs). Scientific papers, mainly from the 20th century, provide reliable methods for the separation of water-soluble dyes. However, dyes insoluble in aqueous solutions have been and still are a challenge. Another problem is the sensitivity of the developed methods, which is, in most cases, insufficient for forensic examination of dyes extracted from a single fiber preserved at the crime scene. Although the methodologies already developed and presented in this review have the potential to be applied in a comparative analysis of textile dye traces, there seems to be a lot of work to be conducted. Some ideas on how to resolve these problems are presented and discussed in the article.

The Use of an Acylhydrazone-Based Metal-Organic Framework in Solid-Contact Potassium-Selective Electrode for Water Analysis.

A solid-contact ion-selective electrode was developed for detecting potassium in environmental water. Two versions of a stable cadmium acylhydrazone-based metal organic framework, i.e., JUK-13 and JUK-13_H2O, were used for the construction of the mediation layer. The potentiometric and electrochemical characterizations of the proposed electrodes were carried out. The implementation of the JUK-13_H2O interlayer is shown to improve the potentiometric response and stability of measured potential. The electrode exhibits a good Nernstian slope (56.30 mV/decade) in the concentration range from 10-5 to 10-1 mol L-1 with a detection limit of 2.1 µmol L-1. The long-term potential stability shows a small drift of 0.32 mV h-1 over 67 h. The electrode displays a good selectivity comparable to ion-selective electrodes with the same membrane. The K-JUK-13_H2O-ISE was successfully applied for the determination of potassium in three certified reference materials of environmental water with great precision (RSD < 3.00%) and accuracy (RE < 3.00%).

A multitechnique approach for discrimination and identification of lipsticks for forensic purposes.

Cosmetics are becoming more and more popular; consequently, the chance of finding them as microtraces at a crime scene increases. They are easily transferable and can provide a link between a suspect and a victim. For this reason, identifying and comparative analysis of red lipstick - the most popular and used - is required. The aim of this study was to apply a multitechnique methodology for the comparative forensic analysis of the red lipsticks traces of a very similar hue. For this purpose, four methods of different physicochemical basics - two nondestructive spectroscopic and two destructive separation techniques - were used. The possibilities and advantages of attenuated total reflection infrared spectroscopy (ATR-FTIR), confocal Raman microscopy (CRM), capillary electrophoresis (MEKC) and gas chromatography-mass spectrometry (GC-MS) have been combined. Specially prepared lipstick traces in various forms (imprints, smears) on different surfaces (absorbent and nonabsorbent) were analyzed to confirm the usefulness of the proposed methods. The premise is that if two methods yield a consistent result, the investigation is terminated at this stage. All investigated traces were properly identified. First, the ATR-FTIR method as a nondestructive technique is recommended. Sometimes, due to strong interferences from the substrates, the newly proposed method with the use of confocal Raman microscopy may be an alternative. The next recommendation is the MEKC method. Only in case of the absence of unambiguous conclusions, it is proposed to use the GC-MS method. This methodology has the potential to be applied in the comparative analysis of red lipsticks for forensic purposes.

Novel Integrated Flow-Based Steam Distillation and Titration System for Determination of Volatile Acidity in Wines.

Novel integrated flow-based steam distillation and titration system with spectrophotometric detection was developed for determination of volatile acidity in wines. Using the system, the distillation procedure was carried out in an automatic manner, starting with introducing into a heated steam distillation module a sample and subjecting it to steam distillation. Under selected conditions, all the analyte was transferred to the distillate; therefore, the system did not require calibration. The collected distillate and titrant were introduced into the next monosegments in varying proportions, in accordance with the developed titration procedure, and directed to the detection system to record the titration curve. The titration was stopped after reaching the end point of titration. Procedures for distillation and titration were developed and verified separately by distillation of acetic acid, acetic acid in the presence of tartaric acid as well as acetic acid, tartaric acid, and titratable acidity, with precision (relative standard deviation) and accuracy (relative error) for both procedures lower than 6.9 and 5.6%, respectively. The developed steam distillation and titration systems were used to determine volatile acidity in samples of white and rosé wines separately and as the integrated steam distillation and titration system, both with precision lower than 9.4% and accuracy better than 6.7%.

A Perspective of the Comprehensive and Objective Assessment of Analytical Methods Including the Greenness and Functionality Criteria: Application to the Determination of Zinc in Aqueous Samples.

The recently proposed concept of White Analytical Chemistry (WAC), referring to the Red-Green-Blue color model, combines ecological aspects (green) with functionality (red and blue criteria), presenting the complete method as "white". However, it is not easy to carry out an overall quantitative evaluation of the analytical method in line with the WAC idea in an objective manner. This paper outlines the perspective of the future development of such a possibility by attempting to answer selected questions about the evaluation process. Based on the study consisting in the evaluation of selected model methods by a group of 12 independent analysts, it was shown how well individual criteria are assessed, whether the variability of assessments by different people is comparable for each criterion, how large it is, and whether averaging the scores from different researchers can help to choose the best method more objectively.

An Automated Hydrodynamically Mediated Technique for Preparation of Calibration Solutions via Capillary Electrophoresis System as a Promising Alternative to Manual Pipetting.

In this paper, a novel procedure for preparing calibration solutions for capillary electrophoresis (CE)-based quantitative analysis is proposed. Our approach, named the automated hydrodynamically mediated technique (AHMT), uses a capillary and a pressure system to deliver the expected amount of working solution and diluent directly to a sample vial. As a result, calibration solutions are prepared automatically inside the CE instrument, without any or with minimal manual operation. Two different modes were tested: forward and reverse, differing in the direction of hydrodynamic flow. The calibration curves obtained for a model mixture of analytes using AHMT were thorough compared to the standard procedure based on manual pipetting. The results were consistent, though the volume of obtained calibration solutions and the potential risk of random errors were significantly minimized by AHMT. Its effectiveness was further enhanced by the application of SCIEX® nanoVials, reducing the actual volume of calibration solutions down to 10 µL.

Comprehensive Assessment of Flow and Other Analytical Methods Dedicated to the Determination of Zinc in Water.

An original strategy to evaluate analytical procedures is proposed and applied to verify if the flow-based methods, generally favorable in terms of green chemistry, are competitive when their evaluation also relies on other criteria. To this end, eight methods for the determination of zinc in waters, including four flow-based ones, were compared and the Red-Green-Blue (RGB) model was exploited. This model takes into account several features related to the general quality of an analytical method, namely, its analytical efficiency, compliance with the green analytical chemistry, as well as practical and economic usefulness. Amongst the investigated methods, the best was the flow-based spectrofluorimetric one, and a negative example was that one involving a flow module, ICP ionization and MS detection, which was very good in analytical terms, but worse in relation to other aspects, which significantly limits its overall potential. Good assessments were also noted for non-flow electrochemical methods, which attract attention with a high degree of balance of features and, therefore, high versatility. The original attempt to confront several worldwide accepted analytical strategies, although to some extent subjective and with limitations, provides interesting information and indications, establishing a novel direction towards the development and evaluation of analytical methods.

3D-printed manifold integrating solid contact ion-selective electrodes for multiplexed ion concentration measurements in urine.

Urinalysis is a simple and non-invasive approach for the diagnosis and monitoring of various health disorders. While urinalysis is predominantly confined to clinical laboratories the non-invasive sample collection makes it applicable in wide range of settings outside of central laboratory confinements. In this respect, 3D printed devices integrating sensors for measuring multiple parameters may be one of the most viable approaches to ensure cost-effectiveness for widespread use. Here we evaluated such a system for the multiplexed determination of sodium, potassium and calcium ions in urine samples with ion-selective electrodes based on state of the art octadecylamine-functionalized multi-walled carbon nanotube (OD-MWCNT) solid contacts. The electrodes were tested in the clinically relevant concentration range, i.e. ca. 10-4 - 10-1 mol L-1 and were proven to have Nernstian responses under flow injection conditions. The applicability of the 3D printed flow manifold was investigated through the analysis of synthetic samples and two certified reference materials. The obtained results confirm the suitability of the proposed system for multiplexed ion analysis in urine.

Nickel Content in Human Internal Organs.

With the growing interest in new applications of metals in modern technologies, an increase in their concentration in the environment can be observed, which, in consequence, may constitute a hazard to human health. That is why it is of a great importance to establish "reference" levels of particular elements (essential or toxic) in human biological samples.The aim of this paper was to determine nickel in autopsy tissues of non-occupationally exposed subjects in Southern Poland (n = 60). Measurements were performed by means of electrothermal atomic absorption spectrometry after microwave-assisted acid digestion according to previously optimized and validated procedure. The results obtained indicate that data cover the wide range of concentrations and generally are consistent with other published findings. Nickel levels in the brain, stomach, liver, kidneys, lungs and heart (wet weight) were between 2.15-79.4 ng/g, 0.5-44.2 ng/g,7.85-519 ng/g, 12.8-725 ng/g, 8.47-333 ng/g and 2.3-97.7 ng/g, respectively. Females had generally lower levels of nickel in tissues than males (statistically significant relationships were found for the liver, kidneys and lungs), and median nickel concentrations in all studied material within all age groups had very similar values, with the exception of stomach.

Modern Flow Analysis.

A brief overview of articles published in this Special Issue of Molecules titled "Modern Flow Analysis" is provided. In addition to cross-sectional and methodological works, there are some reports on new technical and instrumental achievements. It has been shown that all these papers create a good picture of contemporary flow analysis, revealing the most current trends and problems in this branch of flow chemistry.

3D-printed flow manifold based on potentiometric measurements with solid-state ion-selective electrodes and dedicated to multicomponent water analysis.

A 3D-printed flow manifold dedicated to potentiometric simultaneous determination of potassium, sodium, calcium and chloride in water is presented. The method is based on application of miniature solid-contact ion selective electrodes with a special design obtained with the use of 3D printing. The electrodes offer many attractive advantages including short response time and miniaturization feasibility. The use of the proposed novel electrodes enables performance of rapid potentiometric measurements in flow-injection technique and registration of many injection peaks in a short time. One of the advantages of using a special 3D-printed flow vessel for potentiometric measurements was miniaturization of electrodes and the possibility of integrating several (from three up to six) ion selective electrodes in one module enabling realization of multi-component analyses in the same time. Thanks to that the volume of each solution and measurement time were significantly reduced during multi-component analysis. In order to find out if the proposed manifold works properly, three multi-component synthetic samples and four certified reference materials were analyzed. The presented study shows that the proposed 3D-printed flow manifold with solid-state ion-selective electrodes could be an effective tool in a modern multi-component analysis meeting the requirements of green analytical chemistry.

Novel Approach to Automated Flow Titration for the Determination of Fe(III).

A novel approach to automated flow titration with spectrophotometric detection for the determination of Fe(III) is presented. The approach is based on the possibility of strict and simultaneous control of the flow rates of sample and titrant streams over time. It consists of creating different but precisely defined concentration gradients of titrant and analyte in each successively formed monosegments, and is based on using the calculated titrant dilution factor. The procedure was verified by complexometric titration of Fe(III) in the form of a complex with sulfosalicylic acid, using EDTA as a titrant. Fe(III) and Fe(II) (after oxidation to Fe(III) with the use of H2O2) were determined with good precision (CV lower than 1.7%, n = 6) and accuracy ( | RE | lower than 3.3%). The approach was applied to determine Fe(III) and Fe(II) in artesian water samples. Results of determinations were consistent with values obtained using the ICP-OES reference method. Using the procedure, it was possible to perform titration in 6 min for a wide range of analyte concentrations, using 2.4 mL of both sample and titrant.

Novel Approach to Sample Preconcentration by Solvent Evaporation in Flow Analysis.

A preconcentration module operated in flow mode and integrated with a sequential injection system with spectrophotometric detection was developed. Using the system, preconcentration was performed in continuous mode and was based on a membraneless evaporation process under diminished pressure. The parameters of the proposed system were optimized and the system was tested on the example of the spectrophotometric determination of Cr(III). The preconcentration effectiveness was determined using the signal enhancement factor. In the optimized conditions for Cr(III), it was possible to obtain the signal enhancement factors of around 10 (SD: 0.9, n = 4) and determine Cr(III) with precision and intermediate precision of 8.4 and 5.1% (CV), respectively. Depending on the initial sample volume, signal enhancement factor values of about 20 were achieved. Applicability of the developed preconcentration system was verified in combination with the capillary electrophoresis method with spectrophotometric detection on the example of determination of Zn in certified reference materials of drinking water and wastewater. Taking into account the enhancement factor of 10, a detection limit of 0.025 mg L-1 was obtained for Zn determination. Zn was determined with precision less than 6% (CV) and the results were consistent with the certified values.

Application of spectroscopic and separation techniques to the examination of the chemical composition stability of lipsticks exposed to various factors and storage conditions.

In this study, the stability of the chemical composition of lipsticks after exposure to various factors (substrate, time, individual variability, the impact of smoking, the effect of consuming beverages) and storage conditions (laboratory, insolation, without access to light) was examined. The following three analytical methods were used in the study: Attenuated Total Reflection technique (ATR), Gas Chromatography coupled to Mass Spectrometry (GC-MS) and Micellar Electrokinetic Capillary Chromatography (MEKC). Seven red lipsticks characterized by different chemical composition were analyzed. The analysis of variance (ANOVA) was used to estimate the impact of a given factor. It was noticed the lack of influence of individual variability, cigarette smoking and consumed beverages on the stability of the chemical composition of lipsticks. On the other hand, the changes in the chemical composition in lipstick traces depending on the time and storage conditions can be observed - especially when using the GC-MS method. In most cases, the results also indicated the possibility of identifying the lipstick left as a trace, using the ATR and MEKC method even after exposure to various factors and storage conditions. However, the main problem in the case of the ATR analysis is the occurrence of interference originating from the surface on which the trace of lipstick was applied. Ultimately, the conducted research provided evidence for the effectiveness of the MEKC method to the application in forensic science investigation.

Acidity constant of pH indicators in the supramolecular systems studied by two CE-based methods compared using the RGB additive color model.

Acid-base properties of methyl orange, bromocresol green, bromophenol blue, and bromothymol blue were thoroughly investigated in the past due to their application as colorimetric pH indicators. However, it is still unknown how these properties change upon the supramolecular host-guest interactions. Owing to the growing interest in using supramolecular host-guest interactions to reach expected modification of various physicochemical properties of guests, we decided to address this question in the present article. We estimated the shifts of pKa values induced by diverse hosts (cyclodextrins, cucurbiturils, calixarenes, micelles, and serum albumin) and performed a thermodynamic analysis of the selected systems. To make a deeper insight, we confronted the aforementioned dyes with the other kinds of molecules studied by us in the past. In overall, the results obtained demonstrate a large multiplicity of possible pKa behaviors, their poor predictability, and the existence of subtle structure-acidity relationships. In addition, we observed three thermodynamically different mechanisms of pKa alteration. Therefore, more studies are needed to bring closer the promising perspective of a programmable acidity's tuning. Our methodology was based on capillary electrophoresis (CE) applied in two parallel variants: a classical method based on the fitting of a nonlinear function, and an alternative two-value method (TVM), which requires over twice less measurements to estimate pKa. To identify the optimal approach for further studies, both methods were comprehensively compared and discussed based on the RGB additive color model, a user-friendly scale that integrates three primary aspects of an analytical method: analytical performance, green chemistry, and practicality.

Employment of electrostriction phenomenon for label-free electrochemical immunosensing of tetracycline.

The presented work describes a simple label-free electrochemical immunosensor for the determination of tetracycline (TC). The functioning of the sensor was based on the electrostriction of a antibody-terminated thiol layer self-assembled on a gold electrode surface, serving as a dielectric membrane. The intensity of electrostriction was correlated with the amount of TC captured through an affinity reaction with its specific antibody, and was followed in the form of capacitance-potential curves. The process of the immunosensor construction was optimized using electrochemical impedance spectroscopy (EIS). The chemisorption time of the thiol, the duration of the TCAb immobilization and its concentration were optimized. The developed immunosensor exhibited a linear response in two concentration ranges: from 0.95 to 10 µmol L-1 and from 10 to 140 µmol L-1, with the mean sensitivity of 6.27 nF µmol-1 L (88.67 nF µmol-1 L cm-2) and 0.56 nF µmol-1 L (7.84 nF µmol-1 L cm-2), respectively. The limit of detection was evaluated as 28 nmol L-1. The specificity of the proposed sensor toward other antibiotics, amoxicillin and ciprofloxacin, was examined. The immunosensor was successfully employed to quantify TC in a tablet form and in a matrix of river water.

Serum trace elements profile in the pediatric inflammatory bowel disease progress evaluation.

INTRODUCTION: Inflammatory bowel disease (IBD), a chronic inflammatory disorder of gastrointestinal tract, arises from complex interaction between genetics, environment, gut microbiota and mucosal immune response. Along with clinical, endoscopic and radiological evaluation various biomarkers are needed as an additional diagnostic tool, as well as to predict disease course and therapeutic outcomes. AIM: The aim of this study was to evaluate clinical value of essential trace elements (ETEs) serum concentration profile in the assessment of pediatric IBD diseases development. MATERIALS AND METHODS: Concentration of five ETEs: iron (Fe), zinc (Zn), copper (Cu), manganese (Mn) and selenium (Se) in serum of 41 children with newly diagnosed IBD (27 CD and 14 UC) and 20 healthy controls were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrometry (AFS) at the moment of diagnosis and after one year of treatment. RESULTS: The obtained results revealed significant differences in serum concentration profile of studied ETEs' for IBD pediatric patients and healthy controls. Decrease of iron, zinc and selenium and increase of copper and manganese serum concentration were observed in IBD patients at the time of diagnosis. The changes were reversible and after one year of treatment the studied ETEs serum concentration profile resembled much more that observed for healthy controls. Correlations between studied ETEs levels within cases (IBD, CD, UC) were also found to be different from those in healthy controls (HC). CONCLUSION: Although much more studies are required on the subject our results demonstrate a clinical value of ETEs serum concentration profile in pediatric IBD patients regarding disease development.