From a glimpse into the key aspects of calibration and correlation to their practical considerations in chemical analysis.

In this tutorial review, we provide a guiding reference on the good practice in building calibration and correlation experiments, and we explain how the results should be evaluated and interpreted. The review centers on calibration experiments where the relationship between response and concentration is expected to be linear, although certain of the described principles of good practice can be applied to non-linear systems, as well. Furthermore, it gives prominence to the meaning and correct interpretation of some of the statistical terms commonly associated with calibration and regression. To reach a mutual understanding in this significant field, we present, through a practical example, a step-by-step procedure, which deals with typical challenges related to linearity and outlier assessment, calculation of the associated error of the predicted concentration, and limits of detection. The utilization of regression lines to compare analytical methods is also elaborated. The results of regression and correlation data are acquired by implementing the Excel spreadsheet of Microsoft, being perhaps one of the most widely used user-friendly software in education and research.

Magnetic Solid-Phase Extraction Based on Silica and Graphene Materials for Sensitive Analysis of Emerging Contaminants in Wastewater with the Aid of UHPLC-Orbitrap-MS.

With the advancement of technology and nanotechnology, new extraction sorbents have been created and effectively used for the magnetic solid-phase extraction of target analytes. Some of the investigated sorbents have better chemical and physical properties, exhibiting high extraction efficiency and strong repeatability, combined with low detection and quantification limits. In this study graphene oxide (GO) magnetic composites were prepared and used as magnetic solid-phase extraction (MSPE) adsorbents along with synthesized silica based magnetic nanoparticles (MNPs) functionalized with the C18 group for the preconcentration of emerging contaminants (ECs) in wastewater samples generated from hospital and urban facilities. The sample preparation with magnetic materials was followed by UHPLC-Orbitrap MS analysis for the accurate identification and determination of trace amounts of pharmaceutical active compounds and artificial sweeteners in effluent wastewater. Optimal conditions were used for the extraction of ECs from the aqueous samples, prior to UHPLC-Orbitrap MS determination. The proposed methods achieved low quantitation limits between 1.1-33.6 ng L-1 and 1.8-98.7 ng L-1 and satisfactory recoveries in the range of 58.4%-102.6%. An intra-day precision of less than 23.1% was achieved, while inter-day RSD% values in the range of 5.6-24.8% were observed. These figures of merit suggest that our proposed methodology is suitable for the determination of target ECs in aquatic systems.

Phototransformation of Three Psychoactive Drugs in Presence of Sedimental Water Extractable Organic Matter.

Psychoactive drugs are classified as contaminants of emerging concern but there is limited information on their fate in surface waters. Here, we studied the photodegradation of three psychoactive drugs (sertraline, clozapine, and citalopram) in the presence of organic matter (WEOM) extracted under mild conditions from sediment of Lake Pamvotis, Greece. Spectral characterization of WEOM confirmed its humic-like nature. Preliminary experiments using chemical probes showed that WEOM was able to produce oxidant triplet excited state (3WEOM*), singlet oxygen (1O2), and hydroxyl radicals under irradiation with simulated solar light. Then, WEOM at 5 mgC L-1 was irradiated in the presence of the three drugs. It enhanced their phototransformation by a factor of 2, 4.2, and 16 for sertraline, clozapine, and citalopram, respectively. The drastic inhibiting effect of 2-propanol (5 × 10-3 M) on the reactions demonstrated that hydroxyl radical was the key intermediate responsible for drugs photodegradation. A series of photoproducts were identified by ultra-high performance liquid chromatography (UHPLC) coupled to high resolution mass spectrometry (HR-MS). The photodegradation of the three drugs proceeded through several pathways, in particular oxidations of the rings with or without O atom inclusion, N elimination, and substitution of the halogen by OH. The formation of halogenated aromatics was observed for sertraline. To conclude, sedimental natural organic matter can significantly phototransform the studied antidepressant drugs and these reactions need to be more investigated. Finally, ecotoxicity was estimated for the three target analytes and their photoproducts, using the Ecological Structure Activity Relationships (ECOSAR) computer program.

Investigation of the Aquatic Photolytic and Photocatalytic Degradation of Citalopram.

This study investigated the direct and indirect photochemical degradation of citalopram (CIT), a selective serotonin reuptake inhibitor (SSRI), under natural and artificial solar radiation. Experiments were conducted in a variety of different operating conditions including Milli-Q (MQ) water and natural waters (lake water and municipal WWT effluent), as well as in the presence of natural water constituents (organic matter, nitrate and bicarbonate). Results showed that indirect photolysis can be an important degradation process in the aquatic environment since citalopram photo-transformation in the natural waters was accelerated in comparison to MQ water both under natural and simulated solar irradiation. In addition, to investigate the decontamination of water from citalopram, TiO2-mediated photocatalytic degradation was carried out and the attention was given to mineralization and toxicity evaluation together with the identification of by-products. The photocatalytic process gave rise to the formation of transformation products, and 11 of them were identified by HPLC-HRMS, whereas the complete mineralization was almost achieved after 5 h of irradiation. The assessment of toxicity of the treated solutions was performed by Microtox bioassay (Vibrio fischeri) and in silico tests showing that citalopram photo-transformation involved the formation of harmful compounds.

Effects of anti-androgens cyproterone acetate, linuron, vinclozolin, and p,p'-DDE on the reproductive organs of the copepod Acartia tonsa.

The study was performed to detect the effects of anti-androgenic compounds on the reproduction. In this paper alterations observed in the marine calanoid copepod Acartia tonsa exposed to environmental concentrations of cyproterone acetate (CPA), linuron (LIN), vinclozolin (VIN), and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) for 21 days covering a full life cycle are described. Histological alterations were studied with a focus on reproductive organs, gonad and accessory sexual glands. Exposure to ≥1.2 µg L(-1) CPA caused degeneration of spermatocytes and deformation of the spermatophore in males. In a single male exposed to 33 µg L(-1) CPA, an ovotestis was observed. In CPA exposed females, enhancement of oogenesis, increase in apoptosis and a decrease in proliferation occurred. Exposure of males to ≥12 µg L(-1) LIN caused degenerative effects in spermatogonia, spermatocytes and spermatids, and at 4.7 µg L(-1) LIN, the spermatophore wall displayed an irregular formation. In LIN exposed females, no such structural alterations were found; however, the proliferation index was reduced at 29 µg L(-1) LIN. At an exposure concentration of ≥100 µg L(-1) VIN, distinct areas in male gonad were stimulated, whereas others displayed a disturbed spermatogenesis and a deformed spermatophore wall. In VIN exposed female A. tonsa, no effects were observed. Male A. tonsa exposed to p,p'-DDE displayed an impairment of spermatogenesis in all stages with increased degrees of apoptosis. In p,p'-DDE-exposed females, a statistical significant increase of the proliferation index and an intensification of oogenesis were observed at 0.0088 µg L(-1).

Residues of selected polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP) in postmortem lungs from Epirus, northwestern Greece.

Organochlorine (OC) pesticides and polychlorinated biphenyls (PCB) are compounds characterized as persistent organic pollutants (POP) in the environment. These compounds are monitored globally since they enter the human body and accumulate in tissues, resulting in consequent adverse effects. In this study concentrations of selected OC compounds were determined in human autopsy lungs from Epirus, a relatively restricted region in northwestern Greece. This is the first epidemiologic study from Greece reporting on monitoring of environmental pollutants in human autopsy material. Thirty lungs collected from that number of autopsy cases were analyzed: 19 males and 11 females. The age range was 14-91 yr (mean ± SD = 61.8 ± 22.5 yr). Twenty-two cases (73%) were positive for at least one pollutant and eight cases were negative (27%). PCB were the most abundant class of contaminants, detected in 15 out of the 30 cases (50%). Dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexanes (HCH) were second and third in abundance with 9 (30%) and 8 (27%) positive cases, respectively. The frequency of detection showed a tendency to increase with age of individuals. The patterns of OC found in human autopsy lungs were similar to those reported previously for other human specimens. Our results demonstrated a similar trend in contamination sources and distribution has occurred in western Greece as noted globally.

Wax screen-printable ink for massive fabrication of negligible-to-nil cost fabric-based microfluidic (bio)sensing devices for colorimetric analysis of sweat.

Fabric-based microfluidic analytical devices (µADs) have emerged as a promising material for replacing paper µADs thanks to their superior properties in terms of stretchability, mechanical strength, and their wide scope of applicability in wearable devices or embedded in garments. The major obstacle in their widespread use is the lack of a technique enabling their massive fabrication at a negligible-to-nil cost. In response, we report the development of a wax ink with proper thixotropic and hydrophobic properties, fully compatible with automatic screen-printing that allows the one step massive fabrication of microfluidics on a cotton/elastane fabric, with a printing resolution 400 µm (hydrophilic channel) and 1000 µm (hydrophobic barrier), without being necessary any post curing. The cost of the ink (50 g) and of each microfluidic device is ca. 2.3 and 0.007 €, respectively. The active component of the ink was a refined beeswax in a matrix based on ethyl cellulose in 2-butoxy ethyl acetate. Screen-printed fabric µADs were used for the simultaneous colorimetric determination of pH and urea in untreated human sweat by using multivariate regression analysis. This method enabled the direct measurement of urea using urease, regardless of the sweat's pH, and shows strong agreement with a reference method.

Ecotoxicity and rapid degradation of quaternary ammonium compounds (QACs) subjected to combined vacuum UV and UV-C treatment.

Quaternary ammonium compounds (QACs) are active ingredients in a palette of commercially available disinfectants, sanitizers, and biocides. QACs are widely used because of their broad-spectrum antimicrobial properties but the ubiquitous uses have resulted in frequent detection in aquatic and terrestrial matrices including domestic wastewater, surface waters, urban soils and sediments. An increased domestic QACs consumption has increased the environmental occurrence, and investigation of mitigation methods and effects on non-target organisms are in demand. In this study, we examined the potential ecotoxicity of six QACs and investigated the effect of combined vacuum UV (185 nm) and UV-C (254 nm) irradiation (VUV/UVC) on degradation and mitigation of ecotoxicity of QACs. The study showed that combined VUV/UVC irradiation facilitated rapid degradation of benzalkonium chloride, benzethonium chloride, didecyldimethylammonium chloride, dodecyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride. The estimated half-lives varied between 2 and 7 min, and degradation was affected by the initial QAC concentrations, the UV fluence, and the water matrix. The potential ecotoxicity of QACs and VUV/UVC treated QACs was examined using a battery of test organisms that included the luminescent bacterium Aliivibrio fischeri, the gram-negative and gram-positive bacteria Escherichiacoli and Enterococcus faecalis, the freshwater microalga Raphidocelis subcapitata, and the crustacean Daphia magna. The potential for trophic transfer of QACs was investigated in a simplified aquatic food web. Test organisms from different trophic levels were included to assess adverse effects of bioactive compounds in VUV/UVC treated samples including transformation products. The study showed that several QACs were highly toxic to aquatic test organisms with EC50 and/or EC20 values < 1 µM. VUV/UVC treatment of QACs resulted in substantial photolysis of the parent compounds and comprehensive mitigation of the ecotoxicity potential. VUV/UVC represent an attractive oxidation technology for abatement QACs in contaminated water because the process does not require addition of catalysts or precursors.

Configuration of a Simple Method for Different Polyamides 6.9 Recognition by ATR-FTIR Analysis Coupled with Chemometrics.

This study proposes a simple approach for the recognition of polyamide 6.9 samples differing in impurity amounts and viscosities (modulated during the synthesis), which are parameters plausibly variable in polymers' manufacturing processes. Infrared spectroscopy (ATR-FTIR) was combined with chemometrics, applying statistical methods to experimental data. Both non-supervised and supervised methods have been used (PCA and PLS-DA), and a predictive model that could assess the polyamide type of unknown samples was created. Chemometric tools led to a satisfying degree of discrimination among samples, and the predictive model resulted in a great classification of unknown samples with an accuracy of 88.89%. Traditional physical-chemical characterizations (such as thermal and mechanical tests) showed their limits in the univocal identification of sample types, and additionally, they resulted in time-consuming procedures and specimen destruction. The spectral modifications have been investigated to understand the main signals that are more likely to affect the discrimination process. The proposed hybrid methodology represents a potential support for quality control activities within the production sector, especially when the spectra of compounds with the same nominal composition show almost identical signals.

Evaluation of matrix solid-phase dispersion extraction for the determination of polycyclic aromatic hydrocarbons in household dust with the aid of experimental design and response surface methodology.

A simple, fast, and inexpensive procedure for sample preparation based on matrix solid-phase dispersion was developed for the determination of Environmental Protection Agency 16 priority polycyclic aromatic hydrocarbons in indoor dust samples. Parameters that affect the extraction efficiency such as type of dispersant, elution solvent, and solvent volume were evaluated and optimized with the aid of experimental design and response surface methodology. Analysis was performed by HPLC coupled with UV-Vis diode array detector (UV-DAD). For verification, a GC coupled with a mass spectrometer in SIM mode was also applied. Recoveries obtained were from 53 to 120% for all target analytes with detection limits ranging from 0.2 to 10 ng/g and 0.2 to 2 ng/g for LC-UV-DAD and GC-MS, respectively. The optimized method was used for the analysis of 11 household dust samples collected from private houses.

Development and application of chemometric-assisted dispersive liquid-liquid microextraction for the determination of suspected fragrance allergens in water samples.

A simple and green method based on dispersive liquid-liquid microextraction, mated to chemometrics and followed by mass spectrometric detection for the determination of suspected fragrance allergens in water samples is developed and assessed in this work. Volume of extraction and disperser solvent, pH, ionic strength, extraction time, sample volume, as well as centrifugation time were initially optimized in a fractional factorial design. The obtained significant factors were optimized by using a central composite design and the quadratic model between the dependent and the independent variables was built. The obtained optimal conditions were: aqueous sample of 3.8 mL, 100 µL chloroform, 1.40 mL acetone, 4 min centrifugation time, natural pH containing 5% (w/v) NaCl, and centrifugation speed 4000 rpm. Method proved to be linear over a wide range of concentration for all analytes with R(2) between 0.9807 and 0.9959. The repeatability and reproducibility of the proposed method, expressed as relative standard deviation, varied between 3-13% and 4-16%, respectively. The limits of detection ranged from 0.007 to 1.0 µg L(-1) . The recommended method was applied to water samples including baby bath as well as swimming pool water samples and was compared with a previously reported method.

Application of Fabric Phase Sorptive Extraction (FPSE) Engaged to Tandem LC-MS/MS for Quantification of Brorphine in Oral Fluid.

Brorphine (1-[1-[1-(4-bromophenyl) ethyl]-piperidin-4-yl]-1,3-dihydro-2H-benzo [d]imidazol-2-one) is one of the most recent novel synthetic opioids (NSOs) on the novel psychoactive substances (NPSs) market, involved in over 100 deaths in 2020. Brorphine is a substituted piperidine-benzimidazolone analogue that retains structural similarities to fentanyl, acting as a full agonist at the µ-opioid receptor. Oral Fluid (OF) is an alternative matrix, frequently analyzed for the detection of NPS. Fabric phase sorptive extraction (FPSE) is a superior, green-sample -preparation technology recently applied for drug analysis. This contribution presents the development and validation of a method, based on the application of FPSE and liquid chromatography-tandem mass spectrometry (LC-MS/MS), to determine/quantitate brorphine in OF. The method's linearity ranged between 0.05 and 50 ng/mL (R2 = 0.9993), the bias ranged between 12.0 and 16.8%, and inter- and intra-day precisions ranged between 6.4 and 9.9%. Accuracy and extraction efficiency lied between 65 and 75%. LOD/LOQ were 0.015 ng/mL/0.05 ng/mL. Analyte's post-preparative stability was higher than 95%, while no matrix interferences and carryover between runs were observed. This is the first report introducing the application of FPSE for NPS determination, specifically, the quantification of brorphine in OF, thereby presenting a simple, rapid, sensitive, specific, effective, and reliable procedure engaged to LC-MS/MS that is suitable for routine application and the analysis of more NPSs.

Quantification and Classification of Diclofenac Sodium Content in Dispersed Commercially Available Tablets by Attenuated Total Reflection Infrared Spectroscopy and Multivariate Data Analysis.

A new methodology, based on Fourier transform infrared spectroscopy equipped with an attenuated total reflectance accessory (ATR FT-IR), was developed for the determination of diclofenac sodium (DS) in dispersed commercially available tablets using chemometric tools such as partial least squares (PLS) coupled with discriminant analysis (PLS-DA). The results of PLS-DA depicted a perfect classification of the tablets into three different groups based on their DS concentrations, while the developed model with PLS had a sufficiently low root mean square error (RMSE) for the prediction of the samples' concentration (~5%) and therefore can be practically used for any tablet with an unknown concentration of DS. Comparison with ultraviolet/visible (UV/Vis) spectrophotometry as the reference method revealed no significant difference between the two methods. The proposed methodology exhibited satisfactory results in terms of both accuracy and precision while being rapid, simple and of low cost.

Study of the photoinduced transformations of sertraline in aqueous media.

In the present study, the photoinduced degradation of the antidepressant drug sertraline under artificial solar radiation was examined. Photolysis was studied under different experimental conditions to explore its photolytic fate in the aqueous environment. Photolytic degradation kinetics were carried out in ultrapure water, wastewater effluent, as well as in the presence of dissolved organic matter (humic acids), bicarbonate and nitrate ions which enabled their assessment on sertraline photo-transformation. The reaction of sertraline with photoactive compounds accelerated sertraline transformation in comparison with direct photolysis. Moreover, TiO2-mediated photocatalytic degradation of sertraline was investigated, and focus was placed on the identification of by-products. As expected, photocatalysis was extremely effective for sertraline degradation. Photocatalytic degradation proceeded through the formation of forty-four transformation products identified by HPLC-HRMS and after 240 min of irradiation total mineralization was achieved. Microtox bioassay (Vibrio fischeri) was employed to assess the ecotoxicity of the photocatalysis-treated solutions and results have indicated that sertraline photo-transformation proceeds through the formation of toxic compounds.

Developments on chemometric approaches to optimize and evaluate microextraction.

Chemometric experimental design in microextraction plays a crucial role in sustaining the highest quality of analytical data. Making use of the main significant points of chemometric experimental design and microextraction in analytical chemistry we formed the core of this review article. A step-by-step chemometric approach is provided to optimize and validate microextraction-based analytical processes. Significant applications are reported with developments related to microextraction combined with chemometric optimization processes. As it appears from the numerous examples provided in this review, a great number of researchers give credit to the combination of microextraction and chemometrics recognizing that it significantly streamlines sample processing. Moreover, the combination of microextraction with chemometrics addresses problems relating to improvement in detectability and method validation. A worked example on the microextraction of polychlorinated biphenyls is incorporated into the relevant sections of this article and comprehensively provides in a rational and integrated way guidance to people dealing with this subject.

Determination of pesticides and toxic potency of rainwater samples in western Greece.

Rainwater samples from four municipalities located in Achaia Prefecture, Greece, were collected from March to September 2006. The toxic potency of pollutants present in 36 rainwater samples was tested using Daphnia pulex. The pesticide determination was conducted with GC-MS. Only phosphamidon was detected, which appeared in 52% and 13% of the rural and urban areas, respectively. The toxicity of rainwater was determined in 52% and 46.7% of the rural and urban area samples, respectively. Chemical analyses showed that in rural areas, the PO(4)(3-) ions had higher concentrations than in urban areas. On the other hand, the SO(4)(2-), NO(-)(3), and NO(-)(2) anions are more highly concentrated in urban areas. Correlation analysis proved that the toxicity of the rainwater samples is moderate, affected by the presence of the insecticide only in the rural areas. The results indicated that toxicity can be directly assessed via bioassays, even when unknown pollutants are present.

Sustainable production of a new generation biofuel by lipase-catalyzed esterification of fatty acids from liquid industrial waste biomass.

In this work we suggest a methodology comprising the design and use of cost-effective, sustainable, and environmentally friendly process for biofuel production compatible with the market demands. A new generation biofuel is produced using fatty acids, which were generated from acidogenesis of industrial wastes of bioethanol distilleries, and esterified with selected alcohols by immobilized Candida antarctica Lipase-B. Suitable reactors with significant parameters and conditions were studied through experimental design, and novel esterification processes were suggested; among others, the continuous removal of the produced water was provided. Finally, economically sustainable biofuel production was achieved providing high ester yield (<97%) along with augmented concentration (3.35M) in the reaction mixtures at relatively short esterification times, whereas the immobilized lipase maintained over 90% of its initial esterifying ability after reused for ten cycles.

Determination of UV-filter residues in bathing waters by liquid chromatography UV-diode array and gas chromatography-mass spectrometry after micelle mediated extraction-solvent back extraction.

A preconcentration methodology utilizing the cloud point phenomenon is described in this study for the determination of sunscreen agent residues in bathing waters by reversed phase liquid chromatography with UV detection and gas chromatography (GC) with mass spectrometric (MS) detection. The method employs the entrapment of the analytes in the micelles of the non-ionic surfactant TX-114, upon increase of the solution temperature to 60 degrees C. The analytes are either re-extracted or back extracted from the final micellar extract into appropriate organic solvents, a procedure that facilitates the direct application of the method not only with liquid chromatography but mostly importantly with gas chromatographic analysis. Ultrasonication was employed to assist the procedure and accelerate the extraction of the analytes into the solvent phase. Under the optimum experimental conditions, the method affords satisfactory recoveries in the range of 95-102% and relative standard deviation lower than 6% without interference from the presence of the surfactant. The method was successfully applied to the determination of UV filters in natural waters.

Metolachlor photodegradation study in aqueous media under natural and simulated solar irradiation.

To elucidate the photochemical behavior of pesticide metolachlor, degradation was carried out in aqueous media of different compositions such as sea, river, lake, and distilled water under natural and simulated solar irradiation. In addition, the effect of important constituents of natural water such as dissolved organic matter (DOM, isolated from Pamvotis Lake) and nitrate ions was also examined. It was found that photodegradation proceeds via a pseudo-first-order reaction in all cases. The presence of DOM inhibits the photolysis reaction with half-lives ranging from 87 to 693 h whereas the degradation rate was accelerated up to 11 times in the presence of NO(3)(-). In addition, the toxicity of the degradation products formed (generally through hydroxylation, dealkylation, and cyclization reactions) was also performed using the marine luminescent bacterium Vibrio fisheri. Our results indicated a toxicity increase of the irradiated solution showing that photoproducts of higher acute toxic effects were formed.

Analysis of antifouling biocides Irgarol 1051 and Sea Nine 211 in environmental water samples using solid-phase microextraction and gas chromatography.

This study develops a method for the analysis of biocides Irgarol 1051 and Sea Nine 211 in environmental water samples, using solid-phase microextraction (SPME). Their determination was carried out using gas chromatography with flame thermionic (FTD), electron-capture (ECD) and mass spectrometric detection. The main parameters affecting the SPME process such as adsorption-time profile, salt additives and memory effect were studied for five polymeric coatings commercially available for solid-phase microextraction: poly(dimethylsiloxane) (100 and 30 microm), polyacrylate, poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB 65 microm) and Carbowax-divinylbenzene (65 microm). The method was developed using spiked natural waters such as tap, river, sea and lake water in a concentration range of 0.5-50 microg/l. All the tested fiber coatings have been evaluated with regard to sensitivity, linear range, precision and limits of detection. Typical RSD values (triplicate analysis) in the range of 3-10% were obtained depending on the fiber coating and the compound investigated. The recoveries of biocides were in relatively high levels 60-118% and the calibration curves were reproducible and linear (R2>0.990) for both analytes. The SPME partition coefficients (Kf) of both compounds were also calculated experimentally in the proposed conditions for all fibers using direct sampling. Finally the influence of organic matter such as humic acids on extraction efficiency was studied, affecting mostly Sea Nine 211 uptake by the fiber. Optimum analytical SPME performance was achieved using the PDMS-DVB 65 microm fiber coating in ECD and FTD systems for Sea Nine 211 and Irgarol 1051, respectively.