Multi-year interlaboratory exercises for the analysis of illicit drugs and metabolites in wastewater:development of a quality control system

Thirty-seven laboratories from 25 countries present the development of an inter-laboratory testing scheme for the analysis of seven illicit drug residues in standard solutions, tap- and wastewater. Almost 10 000 concentration values were evaluated: triplicates of up to five samples and 26 laboratories per year. The setup was substantially improved with experiences gained across the six repetitions (e.g. matrix type, sample conditions, spiking levels). From this, (pre-)analytical issues (e.g. pH adjustment, filtration) were revealed for specific analytes which resulted in formulation of best-practice protocols for inter-laboratory setup and analytical procedures. The results illustrate the effectiveness of the inter-laboratory setup to assess laboratory performance in the framework of wastewater-based epidemiology. The exercise proved that measurements of laboratories were of high quality (>80% satisfactory results for six out of seven analytes) and that analytical follow-up is important to assist laboratories in improving robustness of wastewater-based epidemiology results

Characterization of the retention of artificial sweeteners by hydrophilic interaction liquid chromatography

The aim of this work was to study the chromatographic behavior of polar artificial sweeteners on three hydrophilic interaction liquid chromatography (HILIC) columns: Kinetex HILIC (unbounded silica, core shell), ZIC HILIC (sulfoalkylbetain) and TSKgel Amide-80 (amide). The studied analytes were dipeptides (aspartame, neotame, advantame, alitame), sulfamates (acesulfame, saccharin, cyclamate), and sugars (sucralose, neohesperidin dihydrochalcone). Critical parameters such as the mobile phase pH, buffer concentration, column temperature, and organic modifier were studied for the investigation of the retention mechanism. Partition and adsorption models were also used. The retention mechanism of dipeptides seems to be partition for the aqueous layer and weak electrostatic interactions or hydrogen bonds. For the sulfamates, on Kinetex and ZIC HILIC columns, it is likely that partitioning to the aqueous layer is combined with the ERLIC phenomena at pH 5.5. For the TSKgel Amide, the partition and the hydrogen bonds formed between the analytes and carbamoyl groups of the stationary phase play an important role in the retention mechanism. For sucralose, partition seems to be the predominant mechanism in every column, while, for neohesperidin dihydrochalcone, both partition to aqueous layer and hydrogen bonding seems to contribute to the retention. This is also the first report of a method for the chromatographic determination of advantame, a new sweetener. © 2018 Taylor & Francis

Reduction of interferences in the determination of lanthanides, actinides and transition metals by an octopole collision/reaction cell inductively coupled plasma mass spectrometer – Application to the analysis of Chios mastic

Lanthanides, actinides and transition metals have demonstrated the ability to be used as fingerprint for the specification of the authenticity and geographical origin of food commodities. Therefore, the existence of analytical methods for their determination is of great importance, since both producers and consumers could benefit. An inductively coupled plasma mass spectrometric (ICP-MS) method was developed and validated for the determination of these elements in a Protected Designation of Origin product, the Chios mastic gum. A multivariate strategy for the microwave digestion of mastic was carried out. Five factors were studied and optimized. Hold time, temperature and HF volume, were found to be the most critical factors, so further optimization was performed. Molecular oxide (MO+, MO2+) and hydroxide (MOH+) interferences were investigated. The capability of an octopole collision/reaction cell ICP-MS to attenuate or remove these interferences was studied. The effect of instrumental parameters on MO+/M+, MOH+/M+ and MO2+/M+ ratios was studied to ensure that observed changes were a result of alteration of the parameter and not due to random fluctuations. Moreover, the effect of kinetic energy discrimination to suppress these species was demonstrated. The energy losses of ions were measured from stopping curves and the estimation of collision cross sections was done. Efficiencies of He and H2 gases were compared and H2 was finally selected for all elements. The calculated recoveries were ranged between 70 and 70% and 104% and the relative standard deviations (intermediate precision) were generally under 16%. The limits of detection were 0.07 ng g−1 (Dy, Th) – 1.4 ng g−1 (Ce). © 2017 Elsevier B.V

Comparison of chemical modifiers for the determination of vanadium in water and oil samples by electrothermal atomization atomic absorption spectrometry

Chemical modifiers (isomorphous metals and other compounds such as NH4SCN and ascorbic acid) for the determination of vanadium are described. Ascorbic acid (100 μg) eliminated the interferences from NaCl, CaCl2 and FeCl3 salts. The mass of the metallic modifiers and the maximum permissible pyrolysis temperature (t(pyr)) have been carefully optimized. Magnesium nitrate (20 μg), rhodium (2 μg) and platinum (2.5 μg) increased t(pyr) from 1100°C, without modifiers, to 1500, 1700 and 1600°C, respectively. The characteristic mass without modifiers was 21.2 pg, whereas in the presence of 20 pg of Mg(NO3)2, 1 μg of Rh and 1 μg of Pt, the characteristic mass was 20.5 pg, 14.7 pg and 14.4 pg, respectively, measuring the peak absorbance with a moderately used graphite tube (around 100 atomization cycles). The LOD was generally 0.5 μg l-1 without chemical modifier and the same with 1 μg of Pt. The efficiency of the above metals as chemical modifiers was tested in the analysis of oil standards diluted with isobutyl methyl ketone (IBMK). It was found that 1 μg of Pt increased the t(pyr) from 1000°C to 1400°C and decreased the characteristic mass from 27.5 to 15.3 pg measuring the peak absorbance with a new graphite tube. Magnesium nitrate was inadequate for this type of sample. The ageing of the graphite tube surface affected the vanadium determination. A slow drift in sensitivity appeared with increasing atomization cycles. This was controlled with periodic recalibration using integrated absorbance measurements

Fate and biotransformation of metal and metalloid species in biological wastewater treatment processes

Suspended and attached growth wastewater treatment processes are widely used for the removal of biodegradable organic constituents and nutrients from wastewater. The frequent detection of toxic metals and metalloids in wastewater contributed to the publishing of numerous papers in the past, investigating their presence, toxicity and behavior in biological wastewater treatment systems (BWTS). In most of these studies, data were referred to total element concentration. However, nowadays it is generally accepted that toxicological and physicochemical properties are differentiated according to elemental speciation. The literature review revealed that there are enough studies investigating chromium species presence, toxicity, fate and biotransformation in BWTS, whereas there are fewer data for organotin compounds. Even less studies exist for arsenic, mercury and selenium species. Most of the results are referred to the activated sludge process. The biotransformation mechanisms are element-dependent. The reduction of Cr(VI) to Cr(III), the sequential debutylation of tributyltin and triphenyltin to inorganic tin, the oxidation of As(III) to As(V) and their methylation to organoarsenicals have been observed. Despite the gaps in the literature, these preliminary, in many cases, results indicate that biological wastewater treatment processes could be used in the future for the detoxification of metal-and metalloid-laden wastewater, allowing the reuse of wastewater and sludge