Should we think about green or white analytical chemistry? Case study: Accelerated sample preparation using an ultrasonic bath for the simultaneous determination of Mn and Fe in beef.

Green Analytical Chemistry (GAC) metrics include a variety of criteria, such as the regent amounts and toxicity, energy consumption, generated waste, among others. The analytical greenness metric (AGREE) and its variant for sample preparation (AGREEprep) cover different aspects that contribute to the environmental sustainability of sample preparation. White Analytical Chemistry (WAC) considers not only environmental aspects but also analytical and practical aspects with a holistic vision based on a Red-Green-Blue color model. A case study is presented to assess the green and white profile of a method based on ultrasound-assisted extraction and determination of Mn and Fe in beef using microwave-induced plasma atomic emission spectroscopy (MP AES). The method was validated and resulted simple, fast without external heating using diluted acids. It was concluded that we should think in green sample preparation with the AGREEprep tool, as well as in white holistic assessments (WAC) as both constitute complementary tools.

Determination of major elements in igneous rocks using microwave plasma atomic emission spectrometry (MP-AES).

An analytical method for sample preparation of igneous rocks and subsequent determination of Si, Na, K, Ca, Mg, Al, Fe, Mn, Ba, Sr, and Ti by means of microwave induced emission spectrometry (MP-AES) was developed and validated. The proposed sample preparation procedure avoids the use of perchloric acid and provided accurate results even for silicon determination using an acid digestion with hydrofluoric acid. The determination of major elements in rocks is required for the design of classification diagrams that provides relevant information for geochemical analysis.•MP-AES showed to be an adequate technique to measure major and some trace elements that are relevant for classification of igneous rocks.•This method is in better agreement with the principles of the Green Analytical Chemistry and constitutes a reliable alternative to classical analytical and tedious procedures used for geochemical analysis.•The methodology was successfully applied to chemical classification of rocks from Valle Chico (Uruguay) using a Total Alkali-Silica Diagram (TAS).

Development of an Ozone-Assisted Sample Preparation Method for the Determination of Cu and Zn in Rice Samples.

A green analytical method for the determination of Cu and Zn in rice samples was developed. This method was based on an ozone-assisted extraction (OAE) in diluted acid media. A novel closed system was designed for this purpose that allowed four simultaneous sample treatments being safe for the laboratory environment. The method consisted in 0.5 g of the sample, 15 minutes of ozonation, and 3 minutes of centrifugation. The obtained supernatant was ready for Cu and Zn determinations by flame atomic absorption spectrometry. Detection limits were 0.20 and 0.08 mg kg-1 for Cu and Zn, respectively, with a precision (RSD) better than 5% for both elements. A certified reference material of rice flour was analyzed for trueness evaluation, and the mean recoveries (%) were 100.4 (Cu) and 95.9 (Zn). Several commercial rice samples were analyzed using this method, and the results were compared with those obtained using traditional microwave-assisted digestion (MAE). Both methods yielded comparable results. Cu and Zn levels were in accordance with reported values in other regions. The OAE resulted to be simple and economical and with results equivalent with those obtained using traditional sample preparation procedures as MAE with the advantage of being in good agreement with the principles of green analytical chemistry.

On-Line Preconcentration and Simultaneous Determination of Cu and Mn in Water Samples Using a Minicolumn Packed with Sisal Fiber by MIP OES.

An on-line preconcentration system for the simultaneous determination of Copper (Cu) and manganese (Mn) in water samples was developed and coupled to a microwave-induced plasma optical emission spectrometer (MIP OES). The flow injection system was designed with a minicolumn packed with sisal fiber (Agave sisalana). A multivariate experimental design was performed to evaluate the influence of pH, preconcentration time, and eluent concentration. Optimal conditions for sample preparation were pH 5.5, preconcentration time was 90 s, and HCl 0.5 mol L-1 was the eluent. The main figures of merit were detection limits 3.7 and 9.0 µg L-1 for Cu and Mn, respectively. Precision was expressed as a relative standard deviation better than 10%. Accuracy was evaluated via spiked recovery assays with recoveries between 75-125%. The enrichment factor was 30 for both analytes. These results were adequate for water samples analysis for monitoring purposes. The preconcentration system was coupled and synchronized with the MIP OES nebulizer to allow simultaneous determination of Cu and Mn as a novel sample introduction strategy. The sampling rate was 20 samples/h. Sisal fiber resulted an economical biosorbent for trace element preconcentration without extra derivatization steps and with an awfully time of use without replacement complying with the principles of green analytical methods.

Characterization of the effects involved in ultrasound-assisted extraction of trace elements from artichoke leaves and soybean seeds.

Ultrasonication is known to induce cavitation and can thus accelerate extraction, dissolution, digestion, and other processes, while the intense mixing caused by the propagation of ultrasound waves enhances analyte transfer to the extraction medium. Consequently, ultrasound-assisted extraction (UAE) is viewed as a simple procedure well suited for the extraction and subsequent determination of trace elements in food. Herein, we use different techniques to characterize several processes involved in probe- and bath-based UAE, apply them to the determination of trace metals (Cd, Cu, Ni, Pb, and Zn) in globe artichoke leaves and soybean seeds, and closely monitor the extraction rates of selected analytes. The developed UAE-based method is found to comply with the criteria of Green Chemistry and is concluded to be a reliable, simple, and cheap alternative to standard food analysis techniques.

Determination of pesticide residues in globe artichoke leaves and fruits by GC-MS and LC-MS/MS using the same QuEChERS procedure.

Aiming to select the most suitable sample preparation for the multiresidue analysis of pesticides in globe artichoke (Cynara cardunculus L.), a modified QuEChERS, a matrix solid phase dispersion and a dispersive ethyl acetate extraction were compared. Trueness and precision were determined at 0.2mgkg-1 for the three methods. The modified QuEChERS showed the best performance. The scope of the method was enlarged to 35 GC and 63 LC amenable pesticides, its overall performance was evaluated and validated to artichoke leaves and fruits according to DG-SANTE Guidelines. Different matrix effects were observed for most of the pesticides which were higher for leaves than fruits. Difenoconazole and flutriafol suffered signal suppression in leaves extracts but showed positive matrix effects in fruits. All pesticides were analyzed at or below their Maximum Residue Levels fixed for globe artichoke by the European Union. The method was successfully applied for the analysis of commercial samples.

Biomonitoring of arsenic in woodworkers exposed to CCA and evaluation of other non-occupational sources in Uruguay.

In Uruguay wood-impregnation plants use chromated copper arsenate (CCA) as preservative applying good manufacture practices (GMP). This study aims a retrospective evaluation of toxicologically relevant species levels in CCA exposed woodworker's urine (As-U) and an assessment of the effects of work risk factors and non-occupational sources in As-U of workers from a selected plant. From 2014 to 2016, As-U in 212 urine samples (As-U) of 73 woodworkers from six CCA impregnation plants were determined. In one of these plants, 35 workers were interviewed to obtain individual data of work tasks, lifestyles, diet, habits, etc. that may contribute to their overall exposure to Arsenic. Responses were statistically evaluated. Out of the 212 urine samples from 73 woodworkers, 96% showed lower levels of As-U than those established by health regulations (<35µgL-1). According to their work tasks 34% of 35 surveyed workers showed high exposure risk to As and 29% moderate exposure risk. Although they have lower levels of As-U owing to their personal protective equipment, As-U significantly correlate to work risk factors. Consumption of bottled water could also contribute to As-U levels as a non-occupational source. These results confirm that efforts of Uruguayan authorities to promote GMP were successful and justify the importance and frequency of As-U systematic biomonitoring for occupational risk assessment. A significant accomplishment of this work is that non-occupational sources of As-like bottled water consumption should also be considered in future studies.

A simple and fast ultrasound-assisted extraction procedure for Fe and Zn determination in milk-based infant formulas using flame atomic absorption spectrometry (FAAS).

A simple and fast ultrasound-assisted procedure for the determination of iron and zinc in infant formulas is presented. The analytical determinations were carried out by flame atomic absorption spectrometry. Multivariate experiments were performed for optimization; in addition, a comparative study was carried out using two ultrasonic devices. A method using an ultrasonic bath was selected because several samples can be prepared simultaneously, and there is less contamination risk. Analytical precision (sr(%)) was 3.3% and 4.1% for iron and zinc, respectively. Trueness was assessed using a reference material and by comparison of the results obtained analyzing commercial samples using a reference method. The results were statistically equivalent to the certified values and in good agreement with those obtained using the reference method. The proposed method can be easily implemented in laboratories for routine analysis with the advantage of being rapid and in agreement with green chemistry.

Infusion, decoction and hydroalcoholic extracts of leaves from artichoke (Cynara cardunculus L. subsp. cardunculus) are effective scavengers of physiologically relevant ROS and RNS.

The globe artichoke (Cynara cardunculus L. subsp. cardunculus) is a perennial plant cultivated in the Mediterranean region and Americas for its edible young flower heads and as an interesting source of bioactive compounds. The present study was undertaken to evaluate scavenging capacity against the most physiologically relevant reactive oxygen species (ROS) and reactive nitrogen species (RNS) of three different extracts from artichoke leaves (infusion, decoction and hydroalcoholic) using different solvents, commonly accepted for human consumption (water and a mixture of ethanol/water). Additionally, the phenolic compounds in each extract were identified and quantified by high performance liquid chromatography coupled to diode array and mass spectrometer detectors (HPLC-DAD-MS/MS). Chlorogenic acid was the major phenolic compound identified in all extracts, followed by 1,3-dicaffeoylquinic acid (cynarin), luteolin-7-rutinoside and the infusion extract presented the highest phenolic content (108mg/g extract, dry basis). In general, the extracts of artichoke leaves presented a remarkable capacity to scavenge ROS and RNS with IC50 values in a low µg/mL range (3.4-43µg/mL). These findings suggest that artichoke could be a potential source of natural antioxidants and has an undeniable nutraceutical value.

Determination of Total Selenium in Infant Formulas: Comparison of the Performance of FIA and MCFA Flow Systems.

Two flow methods, based, respectively, on flow-injection analysis (FIA) and on multicommutated flow analysis (MCFA), were compared with regard to their use for the determination of total selenium in infant formulas by hydride-generation atomic absorption spectrometry. The method based on multicommutation provided lower detection and quantification limits (0.08 and 0.27 µg L(-1) compared to 0.59 and 1.95 µ L(-1), resp.), higher sampling frequency (160 versus. 70 samples per hour), and reduced reagent consumption. Linearity, precision, and accuracy were similar for the two methods compared. It was concluded that, while both methods proved to be appropriate for the purpose, the MCFA-based method exhibited a better performance.

Automated method for the determination of total arsenic and selenium in natural and drinking water by HG-AAS.

A multicommutated flow system was designed and evaluated for the determination of total arsenic and selenium by Hydride Generation Atomic Absorption Spectrometry (HG-AAS). It was applied to the determination of arsenic and selenium in samples of natural and drinking water. Detection limits were 0.46 and 0.08 µg l(-1) for arsenic and selenium, respectively; sampling frequency was 120 samples h(-1) for arsenic and 160 samples h(-1) for selenium. Linear ranges found were 1.54-10 µg l(-1) (R = 0.999) for arsenic and 0.27-27 µg l(-1) (R = 0.999) for selenium. Accuracy was evaluated by spiking various water samples and using a reference material. Recoveries were in the range 95-116%. Analytical precision (s ( r ) (%), n = 10) was 6% for both elements. Compared with the Standard Methods, APHA, 3114B manual method, the system consumes at least 10 times less sample per determination, and the quantities of acid and reducing agent used are significantly lower with a reduction in the generation of pollutants and waste. As an additional advantage, the system is very fast, efficient and environmentally friendly for monitoring total arsenic and selenium levels in waters.

A simple automated method for the determination of nitrate and nitrite in infant formula and milk powder using sequential injection analysis.

A fast and efficient automated method using a sequential injection analysis (SIA) system, based on the Griess, reaction was developed for the determination of nitrate and nitrite in infant formulas and milk powder. The system enables to mix a measured amount of sample (previously constituted in the liquid form and deproteinized) with the chromogenic reagent to produce a colored substance whose absorbance was recorded. For nitrate determination, an on-line prereduction step was added by passing the sample through a Cd minicolumn. The system was controlled from a PC by means of a user-friendly program. Figures of merit include linearity (r(2) > 0.999 for both analytes), limits of detection (0.32 mg kg(-1) NO(3)-N, and 0.05 mg kg(-1) NO(2)-N), and precision (s(r)%) 0.8-3.0. Results were statistically in good agreement with those obtained with the reference ISO-IDF method. The sampling frequency was 30 hour(-1) (nitrate) and 80 hour(-1) (nitrite) when performed separately.

Determination of total by multicommutated-flow hydride generation atomic absorption spectrometry. Application to cow's milk and infant formulae.

A multicommutated flow system was designed and evaluated for the determination of selenium by hydride generation atomic absorption spectrometry (HG-AAS). It was applied to the determination of total selenium in samples of cow's milk (fluid and powder) and infant formulae. Linearity was satisfactory in the range up to 27.5 µg L-1 (h = 0.082 C + 0.0033, h = peak-height, absorbance, C = concentration in µg L-1, r2 = 0.999). Detection (3s) and quantification (10s) limits in solution were LD = 0.08 µg L-1 and LQ = 0.27 µg L-1, corresponding to LD = 3.2 µg kg-1 and LQ = 10.8 µg kg-1 in solid samples, and to LD = 0.8 µg L-1, LQ = 2.7 µg L-1 in fluid milk samples. Trueness was verified by analysis (n = 5) of two reference materials (NIST 1549, Non-fat Milk Powder and NIST 1846 Infant Formula). At the 95% significance level, results were statistically equivalent to the certified values. Instrumental precision (sr(%), n = 5) was in the range 1.4% to 11.7%, analytical precision (sr(%), n = 5) being 4.2 and 9.3% respectively for the determination of the above mentioned reference materials. The sampling frequency of the system was 160 hour-1.

Multiparametric flow system for the automated determination of sodium, potassium, calcium, and magnesium in large-volume parenteral solutions and concentrated hemodialysis solutions.

A multiparametric flow system based on multicommutation and binary sampling has been designed for the automated determination of sodium, potassium, calcium, and magnesium in large-volume parenteral solutions and hemodialysis concentrated solutions. The goal was to obtain a computer-controlled system capable of determining the four metals without extensive modifications. The system involved the use of five solenoid valves under software control, allowing the establishment of the appropriate flow conditions for each analyte, that is, sample size, dilution, reagent addition, and so forth. Detection was carried out by either flame atomic emission spectrometry (sodium, potassium) or flame atomic absorption spectrometry (calcium, magnesium). The influence of several operating parameters was studied. Validation was carried out by analyzing artificial samples. Figures of merit obtained include linearity, accuracy, precision, and sampling frequency. Linearity was satisfactory: sodium, r2>0.999 (0.5-3.5 g/L), potassium, r2>0.996 (50-150 mg/L), calcium, r2>0.999 (30-120 mg/L), and magnesium, r2>0.999 (20-40 mg/L). Precision (sr, %, n=5) was better than 2.1%, and accuracy (evaluated through recovery assays) was in the range of 99.8%-101.0% (sodium), 100.8-102.5% (potassium), 97.3%-101.3% (calcium), and 97.1%-99.8% (magnesium). Sampling frequencies (h-1) were 70 (sodium), 75 (potassium), 70 (calcium), and 58 (magnesium). According to the results obtained, the use of an automated multiparametric system based on multicommutation offers several advantages for the quality control of large-volume parenteral solutions and hemodialysis concentrated solutions.

A multicommuted flow system for the determination of dextrose in parenteral and hemodialysis concentrate solutions.

A new method is presented for the automation of the determination of dextrose in parenteral and hemodialysis solutions. The method is based on multicommutation flow analysis (MCFA) and exploits enzymatic reactions providing a colored derivative that is detected spectrophotometrically (Trinder's method). The reagent, comprising glucose oxidase, peroxidase, 4-hydroxybenzoate and a buffer was obtained from a commercial kit for the determination of glycemia. The flow system used three 3-way solenoid valves operating under computer control. The necessary software was developed for the purpose and compiled in QuickBASIC 4.0 The influence of some operating variables (segment size, number of segments and reactor length) was studied. Calibration curves in the range 0-1g/L presented a slight curvature and were fitted with a second-degree polynomial (h=-0.0632C(2)+0.6039C+0.166, r(2)=0.9973, h being the peak-height (absorbance) and C the concentration in g/L). The method was validated by analyzing artificial samples presenting accurately known concentrations of dextrose, and comparing the results with the known value and with value obtained by polarimetry. Recoveries were in the range 96.6-100.2%, and the difference with the polarimetric analysis was in the range 0.1-3.3%. Precision (R.S.D.,%) was better than 2.4%. Sampling frequency of the system was 90 samples/h, with a reagent consumption of 0.14 mL per sample.