Automated H2O2 monitoring during photo-Fenton processes using an Arduino self-assembled automatic system.

A cheap and easy to use Arduino self-assembled automatic system was employed to continuously monitor the hydrogen peroxide consumption during the photo-Fenton degradation of caffeine, selected as model target compound. The automatic system made it possible to measure the H2O2 concentration in the reaction cell via a colorimetric reaction and to take samples for HPLC analysis minimising the operator manual intervention and exposure to UV radiation. The obtained results were compared in terms of LOD and LOQ with H2O2 measurements manually performed using UV-Vis spectrophotometry, evidencing better analytical performance when using the automatic system; LOD and LOQ were respectively 0.032 mM and 0.106 mM for the automatic system against 0.064 mM and 0.213 mM for UV-Vis spectrophotometry. Furthermore, the photo-Fenton treatment was optimised by means of a Design of Experiments (DoE) investigating the effect of added H2O2 concentration, iron concentration and caffeine initial concentration on system performances. The use of the automatic device for such monitoring provided several advantages: automation (with consequent reduction of the workload), measurement increased precision, reduced reagents consumption and waste production in agreement with the principles of Green Analytical Chemistry.

Unveiling origins, composition, and appearance of ancient Islamic gold coins through elemental and smartphone-based colorimetric studies.

In this article, the Islamic gold coins collections of the University of Valencia is studied for the first time for its elemental composition and colorimetric properties. To that end, non-destructive elemental analysis using energy-dispersive X-ray fluorescence is applied to obtain the coins' elemental profile. Additionally, the colour of the coins is assessed using smartphone-based colorimetry as an innovative non-invasive method. Results indicate that the Islamic coins could be attributed to Almoravids, and the gold origin could be the famous Sudanese gold, an ore which was valued all over the world. Also, the text found in the coins was translated and allowed to objectively identify the mint and year. Based on these results, it can be seen that the earliest coins struck in the Iberian Peninsula are characterised by slightly lower gold concentrations than the ones struck in the northern part of Africa, pointing towards a potential recycling of coins which already circulated in the area. In conclusion, this work provides new analytical insights into a peculiar and unique type of samples, allowing to draw some conclusions in terms of their origins and materials, and for the first time allows to characterise the chromatic coordinates of this type of samples.

Smartphone-based procedure to determine content of single synthetic dyes in food using the Arata-Possetto extraction method.

The use of additives, including dyes, is common in the preparation of food products. The analytical control of artificial food dye content is relevant since some, such as azo dyes, may produce cancer and attention deficit disorders and hyperactivity in children. Consequently, the maximum permitted concentration of azo dyes in food is regulated by current legislation. Therefore, it is of interest to find simple and fast procedures for the control of these compounds. The aim of this study is to determine the concentration of azo dyes in food samples by the Arata-Possetto method - based on the extraction of azo dyes employing natural wool -, followed by the analysis of an image captured by a smartphone camera. After experimentally determining the optimal extraction conditions, the calibration curves for standard solutions of different food dyes and the color of the dyed wool were obtained. Results from dyed wool image processing were compared with the absorbance spectra of the solutions before extraction as measured by a diode array spectrophotometer. The spectrophotometric and the image processing procedures were employed to obtain the calibration curves for different food dyes, which were subsequently employed to analyze food samples. Statistical treatment shows that the results of both methods are comparable.

The casts of Pompeii: Post-depositional methodological insights.

The casts of Pompeii bear witness to the people who died during the Vesuvius 79 AD eruption. However, studies on the cause of death of these victims have not been conclusive. A previous important step is the understanding of the post-depositional processes and the impact of the plaster in bones, two issues that have not been previously evaluated. Here we report on the anthropological and the first chemical data obtained from the study of six casts from Porta Nola area and one from Terme Suburbane. A non-invasive chemical analysis by portable X-ray fluorescence was employed for the first time on these casts of Pompeii to determine the elemental composition of the bones and the plaster. Elemental profiles were determined providing important data that cross-referenced with anthropological and stratigraphic results, are clearly helpful in the reconstruction of the perimortem and post-mortem events concerning the history of these individuals. The comparative analyses carried out on the bone casts and other collections from burned bones of the necropolis of Porta Nola in Pompeii and Rome Sepolcreto Ostiense, and buried bones from Valencia (Spain), reveal the extent of high temperature alteration and post-depositional plaster contamination. These factors make bioarchaeological analyses difficult but still allow us to support asphyxia as the likely cause of death.

Development of an automated colorimeter controlled by Raspberry Pi4.

A low-cost new instrument to carry out automated colorimetric analysis has been developed. The device consists of a carousel sampler, built by a 3D-printer, and a Raspberry Pi4-controlled signal measurement module based on the RGBC (red, green, blue and clear) responses of a TCS34725 color light-to-digital converter with IR filter. The device has been tested with calibration standards of different food dyes (Tartrazine, Red Allure AC and Brilliant Blue FCF) and three food samples containing one of each food dye. The new device provides R2 > 0.995 and a LOD of 1.1, 1.4 and 0.1 µmol L-1 for each food dye, respectively. The results are statistically comparable to those obtained with a conventional benchtop spectrophotometer. The proposed device achieves a reduction in sample and waste volume and in analysis time, minimizes the use of energy, and allows in situ measurements, being an automated method it is safer for operators in comparison to the reference method, yielding similar analytical results and following the principles of green analytical chemistry.

Smartphone-based colorimetric study of adulterated tuna samples.

In this work, a colorimetric analysis of adulterated tuna samples is carried out using both a spectroradiometer and a smartphone as capture devices. Yellowfin tuna (Thunnus albacares) slices were treated with nitrate and nitrite salts, as well as with two different vegetable extracts (beetroot and radish), and the resulting NO2- and NO3- concentration was analysed using HPLC-DAD. The results indicate that both nitrite and beetroot treatments work properly as colouring agents in tuna, being nitrate also effective. When assessing the effect of radish, the final flesh had a more whitish colour. Overall, this approach allows to obtain colorimetric data which can distinguish among the different adulterating agents.

Green direct determination of mineral elements in artichokes by infrared spectroscopy and X-ray fluorescence.

Near infrared (NIR) and X-ray fluorescence (XRF) spectroscopy were investigated to predict the concentration of calcium, potassium, iron, magnesium, manganese and zinc in artichoke samples. Sixty artichokes were purchased from different Spanish areas (Benicarló, Valencia and Murcia). NIR and XRF spectra, combined with partial least squares (PLS) data treatment, were used to develop chemometric models for the prediction of mineral concentration. To obtain reference data, samples were mineralised and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Coefficients of determination obtained for the regression between predicted values and reference ones for calcium, potassium, magnesium, iron, manganese and zinc were 0.61, 0.79, 0.53, 0.77, 0.54 and 0.60 for NIR and 0.96, 0.93, 0.80, 0.79, 0.76 and 0.90 for XRF, respectively. Both assayed methodologies, offer green alternatives to classical mineral analysis, but XRF provided the best results in order to be used as a quantitative screening method.

Mineral profile of Spanish commercial baby food.

Commercial baby foods are an important part of the daily intake of babies from 6 to 12 months. The mineral profile of commercial baby foods in Spain was determined to establish levels of essential and non-essential elements, and their contribution to adequate intake (AI) and estimated average requirement (EAR). Thirty-five jars of commercial foods containing meat, fish, vegetables and fruit were obtained from the Spanish market and the mineral composition determined for 14 elements. In general, the baby foods analysed were sufficient for an adequate mineral intake, but contributions to AI and EAR for iron, zinc and calcium were very low (5-20%, 10-60% and 10-70%, respectively). This deficiency could be associated with growth problems or diseases in adulthood, and fortification of commercial products is recommended.

Mineral profile of kaki fruits (Diospyros kaki L.).

The main objective of this study was the determination of the mineral profile of 167 kaki fruit (Diospyros kaki L.) samples produced from different regions of Spain, including samples with the protected designation of origin (PDO) 'Kaki Ribera del Xúquer' Valencia (Spain). Samples were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Consumption of one piece of kaki fruit (200-400 g) would give a mineral intake providing 1-10% of the recommended daily allowance (RDA) for calcium, 1-30% for copper and potassium, 1-15% from iron and magnesium, up to 1% of sodium, and up to 4% of zinc. ANOVA analysis indicates differences between samples from different Spanish region, thus offering a way for authentication of PDO sample origin.

Determination of total mercury in nuts at ultratrace level.

Total mercury, at µg kg(-1) level, was determined in different types of nuts (cashew nut, Brazil nuts, almond, pistachio, peanut, walnut) using a direct mercury analyser after previous sample defatting and by cold vapour atomic fluorescence spectrometry. There is not enough sensitivity in the second approach to determine Hg in previously digested samples due to the strong matrix effect. Mercury levels in 25 edible nut samples from Brazil and Spain were found in the range from 0.6 to 2.7µg kg(-1) by using the pyrolysis of sample after the extraction of the nut fat. The accuracy of the proposed method was confirmed by analysing certified reference materials of Coal Fly Ash-NIST SRM 1633b, Fucus-IAEA 140 and three unpolished Rice Flour NIES-10. The observed results were in good agreement with the certified values. The recoveries of different amounts of mercury added to nut samples ranged from 94 to 101%. RSD values corresponding to three measurements varied between 2.0 and 14% and the limit of detection and quantification of the method were 0.08 and 0.3µg kg(-1), respectively.

Speciation of methylmercury in market seafood by thermal degradation, amalgamation and atomic absorption spectroscopy.

Sample thermal decomposition followed by mercury amalgamation and atomic absorption has been employed for the determination of methylmercury (MeHg) in fish. The method involves HBr leaching of MeHg, extraction into toluene, and back-extraction into an aqueous l-cysteine solution. Preliminary studies were focused on the extraction efficiency, losses, contaminations, and species interconversion prevention. The limit of detection was 0.018µgg(-1) (dry weight). The intraday precision for three replicate analysis at a concentration of 4.2µgg(-1) (dry weight) was 3.5 percent, similar to the interday precision according to analysis of variance (ANOVA). The accuracy was guaranteed by the use of fortified samples involving 83-105 percent recoveries, and certified reference materials TORT-2 (lobster hepatopancreas) and DORM-3 (dogfish liver), providing 107 and 98 percent recovery of certified values. The greenness of the method was also evaluated with the analytical eco-scale being obtained a final score of 73 points which means an acceptable green analysis. The method was applied to fifty-seven market samples of different fish acquired from local markets in several sampling campaigns. The content of MeHg found varied between 0.0311 and 1.24µgg(-1) (wet weight), with values that involve 33-129 percent of the total mercury content. Some considerations about food safety were also done taking into account data about Spanish fish consume and Tolerable Weekly Intake (TWI) established for MeHg.

Determination of mercury in rice by cold vapor atomic fluorescence spectrometry after microwave-assisted digestion.

A cold vapor atomic fluorescence spectrometry method (CV-AFS) has been developed for the determination of Hg in rice samples at a few ngg(-1) concentration level. The method is based on the previous digestion of samples in a microwave oven with HNO(3) and H(2)O(2) followed by dilution with water containing KBr/KBrO(3) and hydroxylamine and reduction with SnCl(2) in HCl using external calibration. The matrix interferences and the effect of nitrogen oxide vapors have been evaluated and the method validated using a certified reference material. The limit of detection of the method was 0.9ngg(-1) with a recovery percentage of 95+/-4% at an added concentration of 5ngg(-1). The concentration level of Hg found in 24 natural rice samples from different origin ranged between 1.3 and 7.8ngg(-1).

Non-chromatographic speciation of toxic arsenic in vegetables by hydride generation-atomic fluorescence spectrometry after ultrasound-assisted extraction.

A non-chromatographic, sensitive and simple analytical method has been developed for the determination of toxic arsenic species in vegetable samples by hydride generation-atomic fluorescence spectrometry (HG-AFS). As(III), As(V), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were determined by hydride generation-atomic fluorescence spectrometry using a series of proportional equations. The method is based on a single extraction of the arsenic species considered from vegetables through sonication at room temperature with H(3)PO(4) 1 mol L(-1) in the presence of 0.1% (w/v) Triton XT-114 and washing of the solid phase with 0.1% (w/v) EDTA, followed by direct measurement of the corresponding hydrides in four different experimental conditions. The limit of detection of the method was 3.1 ng g(-1) for As(III), 3.0 ng g(-1) for As(V), 1.5 ng g(-1) for DMA and 1.9 ng g(-1) for MMA, in all cases expressed in terms of sample dry weight. Recovery studies provided percentages greater than 91% for all considered species in spiked samples of chards and aubergines. Total toxic As found in the aforementioned samples was at the level of 90 ng g(-1); As(III) is followed by As(V), DMA and MMA which are the main species of As in chards being As(V) the main As compound in aubergines.

A review on molybdenum determination in solid geological samples.

This review highlights the necessity for the development of proper sampling and storage, fast pretreatment methodology followed by highly sensitive detection for the determination of molybdenum in geological samples. Distribution of concentration and chemical speciation of molybdenum analysis in solid geological matrices have also been discussed.

Determination of thallium in biological samples.

Determination of thallium has become a major interest because of its high toxicity, especially as the monovalent cation. Thallium poisoning in the human body must be checked quickly by analysis of biological samples. This review highlights the development of highly sensitive detection techniques applied to the determination of thallium in biological samples, with or without pretreatment, based on the literature compiled in Analytical Abstracts from 1990.

Non-chromatographic speciation of toxic arsenic in fish.

A rapid, sensitive and economic method has been developed for the direct determination of toxic species of arsenic present in fish and mussel samples. As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) were determined by hydride generation-atomic fluorescence spectrometry using a series of proportional equations without the need of a chromatographic previous separation. The method is based on the extraction of arsenic species from fish through sonication with HNO(3) 3moll(-1) and 0.1% (m/v) Triton and washing of the solid phase with 0.1% (m/v) EDTA, followed by direct measurement of the corresponding hydrides in four different experimental conditions. The limit of detection of the method was 0.62ngg(-1) for As(III), 2.1ngg(-1) for As(V), 1.8ngg(-1) for MMA and 5.4ngg(-1) for DMA, in all cases expressed in terms of sample dry weight. The mean relative standard deviation values (R.S.D.) in actual sample analysis were: 6.8% for As(III), 10.3% for As(V), 8.5% for MMA and 7.4% for DMA at concentration levels from 0.08mgkg(-1) As(III) to 1.3mgkg(-1) DMA. Recovery studies provided percentages greater than 93% for all species in spiked samples. The analysis of SRM DORM-2 and CRM 627 certified materials evidenced that the method is suitable for the accurate determination of arsenic species in fish.

Multicommutation as an environmentally friendly analytical tool in the hydride generation atomic fluorescence determination of tellurium in milk.

The aim of this study is to show the advantages of the emerging multicommutation methodology based on the use of solenoid valves for Te determination in milk by hydride generation atomic fluorescence spectrometry (HG-AFS). The delivery of a series of alternating sequential insertions of small volumes of samples and reagents gives rise to new hydrodynamic processes and exciting analytical potentials by controlling the time of flow through the on/off-switched solenoid valves. This drastically reduces the reagent consumption by a factor of 4 and the generation of effluents (590 mL h(-1) instead of 750 mL h(-1) generated by the continuous-mode measurement) and also provides an improvement in the laboratory productivity by an increase of the sample throughput (85 h(-1) compared to 20 h(-1) found in the continuous mode). So, multicommutation is an environmentally and economically sustainable alternative to the methodology based on continuous measurements. The multicommutation-based method developed was applied to tellurium determination in commercially available milk samples; a calibration range of 0.0-0.5 ng mL(-1) and a detection limit of 0.20 ng L(-1) with average relative standard deviation of 2.1% were found. Comparable results were obtained for a series of samples using both continuous and multicommutation HG-AFS modes.

Determination of As, Sb, Se, Te and Bi in milk by slurry sampling hydride generation atomic fluorescence spectrometry.

A simple and fast analytical procedure has been developed for the determination of As, Sb, Se, Te and Bi in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS). Samples were treated with aqua regia for 10min in an ultrasound water bath and pre-reduced with KBr for total Se and Te determination or with KI and ascorbic acid for total As and Sb, the determination of Bi being possible in all with or without pre-reduction. Slurries of samples, in the presence of antifoam A, were treated with NaBH(4) in HCl medium to obtain the corresponding hydrides, and AFS measurements were processed in front of external calibrations prepared and measured in the same way as samples. Results obtained by the developed procedure compare well with those found after microwave-assisted complete digestion of samples. The proposed method is simple and fast, and only 1ml of milk is needed. The values obtained for detection limit are 2.5, 1.6, 3, 6 and 7ngl(-1) for As, Sb, Se, Te and Bi respectively in the diluted samples, with average relative standard deviation values of 3.8, 3.1, 1.9, 6.4 and 1.2% for three independent analysis of a series of commercially available samples of different origin. Data found in Spanish market samples varied from 3.2+/-0.3 to 11.3+/-0.2ngg(-1) As, from 3.1+/-0.2 to 11.6+/-0.4ngg(-1) Sb, from 10.7+/-0.5 to 25.5+/-0.4ngg(-1) Se, from 0.9+/-0.2 to 9.4+/-0.6ngg(-1) Te and from 11.5+/-0.1 to 27.7+/-0.4ngg(-1) Bi.

Determination of ultratrace bismuth in milk samples by atomic fluorescence spectrometry.

A sensitive procedure was developed for determination of bismuth (Bi) in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS) after microwave-assisted sample digestion with HNO3 and H2O2. The method provides a sensitivity of 1832 fluorescence units (ng/mL) with a detection limit of 0.01 ng/mL, which corresponds to 20 pg absolute limit of detection, equivalent to 0.50 ng/g in the original sample. Application of the methodology to cow milk samples from the Spanish market showed the presence of Bi at a concentration of 11.8-28.8 ng/g, which compared well with data obtained after dry ashing of samples and with data obtained by inductively coupled plasma-mass spectrometry after microwave-assisted digestion.

Determination of arsenic and antimony in milk by hydride generation atomic fluorescence spectrometry.

A highly sensitive procedure has been developed for total arsenic and antimony determination in milk samples by hydride generation atomic fluorescence spectrometry after microwave-assisted sample digestion. The discrete introduction of 2 ml of digested sample in the automated continuous flow hydride generation system allows us to reduce drastically the sample and HCl consume and to determine several elements from a same sample digestion. The method provides detection limits of 0.006 and 0.003 ng ml(-1), a sensitivity of 2390 and 2840 fluorescence units per ng ml(-1) for As and Sb respectively, and average relative standard deviation of 2.3% for As and 4.8% for Sb. The analysis of cow milk samples, obtained from the Spanish market evidenced the presence of As at concentration levels from 3.4 to 11.6 ng g(-1) and Sb levels from 3.5 to 11.9 ng g(-1), thus in a proportion near to 1:1, which is in contrast with the 10:1 natural ratio between As and Sb and could evidence the effect of the introduction of new alloys and polymer materials in the industrial process of milk. The method was validated by the comparison of data found for commercial samples by using the proposed procedure and reference methods based on dry-ashing and AFS, and microwave-assisted digestion and inductively coupled plasma mass spectrometry determination.