Evaluation of the sorption/desorption processes of pesticides in biodegradable mulch films used in agriculture

Microplastics from mulch films can be a source of chemical contamination to agricultural soils. In this context, biodegradable films have been widely positioned as a greener choice. However, their sorption/desorption capabilities, in contrast to the conventional plastic types remain understudied. It is for this reason that objective evaluation of their interactions with residual agricultural contaminants becomes important. Our findings reveal that polyethylene (PE) mulch films retained lower amounts of pesticide residues and demonstrated a higher desorption/release [median desorption = 71.86 μg/L or about 50%], while polybutylene adipate terephthalate (PBAT) mulch films retained higher amounts of pesticide residues onto their surface and demonstrated a much lower desorption [median desorption = 24.27 μg/L or about 17%] after a spraying event. A higher ambient temperature had no significant effect on final desorption amounts in both PE [median = 65.27 μg/L at 20 °C and 74.23 μg/L at 40 °C] and PBAT [median = 24.26 μg/L at 20 °C and 24.78 μg/L at 40 °C] mulch films. However, it did favour a faster desorption pace in PE films. Desorption in PBAT and PE plastic types was correlated with the log Kow value [Spearman's correlation: 0.857 and 0.837 respectively, p < 0.05]. However, only a moderate correlation with pKa was observed in PBAT [Spearman's correlation: 0.478, p < 0.05], while none for PE plastic type. Sorption of pesticides onto biodegradable PBAT microplastics were best explained by Elovich [R2: 0.937-0.959] and pseudo-second order kinetics [R2: 0.942-0.987], suggesting the presence of chemisorption. Furthermore, Weber Morris plots suggested the presence of a multi-step process and Boyd plots indicated that film diffusion or chemical bond formation was the rate-limiting step governing this phenomenon.

Quantification of nanoplastic uptake and distribution in the root, stem and leaves of the edible herb Lepidum sativum

This study confirms the uptake, translocation and bioaccumulation of 100 nm polystyrene nanoplastics in the root, stem and leaves of the plant Lepidum sativum at exposure concentrations ranging from environmentally realistic 10 μg/L up to a high of 100 mg/L. Accumulation in plant tissues was characterised by aggregation in the intercellular spaces and heterogeneous distribution. Nanoplastic presence was confirmed in the root tips, root surface and stele, lateral roots, root hairs, stem vascular bundles, leaf veins and mesophyll, as well as leaf epidermis including stomatal sites. Quantification results show that majority of the particles were retained in the root and accumulation in stem and leaves was only 13 to 18 % of the median value in roots. There was a reduction of 38.89 ± 9.62 % in the germination rate, 55 % in plant fresh weight, as well as in root weight (> 80 %), root length (> 60 %), shoot weight (51 to 78 %) and number of lateral roots (> 28 %) at exposure concentrations at and above 50 mg/L. However, lower, environmentally probable exposure concentrations did not affect the plant health significantly. Our results highlight the urgent need for further exploration of this issue from the point of view of food safety and security. STATEMENT OF ENVIRONMENTAL IMPLICATION: Micro and nanoplastics have been reported in agricultural environments across the globe and reports regarding their hazardous effects over agricultural and plant health call for an urgent exploration of this issue. This work demonstrates the uptake, bioaccumulation and distribution of nanoplastics in an edible plant at an environmentally realistic concentration and raises serious concerns regarding the possible implications for food safety and security. It presents a novel approach which addresses the quantification of nanoplastic accumulation in plant tissues and helps identify the mechanism and trends behind this phenomenon which has been a challenge up until now.

Pesticide residues evaluation of organic crops. A critical appraisal

In the last decade, the consumption trend of organic food has increased dramatically worldwide. Since only a few pesticides are authorized in organic crops, concentrations are expected to range at zero or ultra-trace levels. In this context, the aim of the present study was to investigate the need for an improvement in the residue controls at very low concentrations (<0.010 mg kg-1) and to assess the impact of the scope of the analytical methods for this type of crops. For that purpose, a monitoring study for fruit and vegetable samples covering a wide range of pesticides (3 2 8) at low LOQs (0.002-0.005 mg kg-1) was developed. The results showed that the impact of applying analytical methods with low LOQs was not very relevant in the majority of the cases. However, a wide scope presented a high influence on this evaluation, especially regarding the inclusion of very polar compounds and metabolites.

A non-targeted metabolomic approach to identify food markers to support discrimination between organic and conventional tomato crops

In the last decade, the consumption trend of organic food has increased dramatically worldwide. However, the lack of reliable chemical markers to discriminate between organic and conventional products makes this market susceptible to food fraud in products labeled as "organic". Metabolomic fingerprinting approach has been demonstrated as the best option for a full characterization of metabolome occurring in plants, since their pattern may reflect the impact of both endogenous and exogenous factors. In the present study, advanced technologies based on high performance liquid chromatography-high-resolution accurate mass spectrometry (HPLC-HRAMS) has been used for marker search in organic and conventional tomatoes grown in greenhouse under controlled agronomic conditions. The screening of unknown compounds comprised the retrospective analysis of all tomato samples throughout the studied period and data processing using databases (mzCloud, ChemSpider and PubChem). In addition, stable nitrogen isotope analysis (δ¹⁵N) was assessed as a possible indicator to support discrimination between both production systems using crop/fertilizer correlations. Pesticide residue analyses were also applied as a well-established way to evaluate the organic production. Finally, the evaluation by combined chemometric analysis of high-resolution accurate mass spectrometry (HRAMS) and δ¹⁵N data provided a robust classification model in accordance with the agricultural practices. Principal component analysis (PCA) showed a sample clustering according to farming systems and significant differences in the sample profile was observed for six bioactive components (L-tyrosyl-L-isoleucyl-L-threonyl-L-threonine, trilobatin, phloridzin, tomatine, phloretin and echinenone).

Quantitative determination of poly(amidoamine) dendrimers in urine by liquid chromatography/electrospray ionization hybrid quadrupole linear ion trap mass spectrometry

RATIONALE

Dendrimer nanocarriers have become of increasing interest in the field of biomedicine for their drug delivery potential. Surface modifications and optimized nanosize control are the strategies being followed to enhance drug delivery efficacy and renal clearance, especially for dendrimers of a lower generation number. The aim of this study was the development and performance evaluation of an analytical method for the quantitative determination of polyamidoamine (PAMAM) dendrimers in urine.

METHODS

PAMAM dendrimers (generations G0 to G3) were analyzed using liquid chromatography/electrospray ionization hybrid quadrupole linear ion trap mass spectrometry (LC/ESI-QqLIT-MS). Quantitative analysis was performed in selected reaction monitoring (SRM) mode. To confer a higher degree of confidence on the identification of PAMAM dendrimers, an SRM scan and collision-induced dissociation (CID), as a dependent scan, were performed in one single run using the information-dependent acquisition (IDA) mode.

RESULTS

The LC/ESI-QqLIT-MS method, in SRM mode, allowed quantitative determination in urine matrix with good repeatability and reproducibility (relative standard deviation (R.S.D.) from 2 to 15%), linearity (R >0.99) over the concentration range (6∙10^-4 to 5∙10^-2  mmol.L^-1 ), and sensitivity within the micromolar range. The detection limit values were above 1∙10^-4  mmol.L^-1 in both solvent and urine, for the generations studied.

CONCLUSIONS

The developed method has demonstrated a capability for the identification and quantification of PAMAM dendrimer nanoparticles in a complex liquid matrix. The use of an LC/ESI-QqLIT-MS system, of modest m/z range and unit resolution, offers an alternative in the analysis of lower generation PAMAM dendrimers between mass analyzers of higher resolution and the conventional LC-UV method that is commonly applied for dendrimer quantification, but which lacks sufficient identification capacity. Copyright © 2013 John Wiley & Sons, Ltd.

New trends in the analytical determination of emerging contaminants and their transformation products in environmental waters

Since the so-called emerging contaminants were established as a new group of pollutants of environmental concern, a great effort has been devoted to the knowledge of their distribution, fate and effects in the environment. After more than 20 years of work, a significant improvement in knowledge about these contaminants has been achieved, but there is still a large gap of information on the growing number of new potential contaminants that are appearing and especially of their unpredictable transformation products. Although the environmental problem arising from emerging contaminants must be addressed from an interdisciplinary point of view, it is obvious that analytical chemistry plays an important role as the first step of the study, as it allows establishing the presence of chemicals in the environment, estimate their concentration levels, identify sources and determine their degradation pathways. These tasks involve serious difficulties requiring different analytical solutions adjusted to purpose. Thus, the complexity of the matrices requires highly selective analytical methods; the large number and variety of compounds potentially present in the samples demands the application of wide scope methods; the low concentrations at which these contaminants are present in the samples require a high detection sensitivity, and high demands on the confirmation and high structural information are needed for the characterisation of unknowns. New developments on analytical instrumentation have been applied to solve these difficulties. Furthermore and not less important has been the development of new specific software packages intended for data acquisition and, in particular, for post-run analysis. Thus, the use of sophisticated software tools has allowed successful screening analysis, determining several hundreds of analytes, and assisted in the structural elucidation of unknown compounds in a timely manner.

Analytical improvements of hybrid LC-MS/MS techniques for the efficient evaluation of emerging contaminants in river waters: a case study of the Henares River (Madrid, Spain)

PURPOSE

Instrumental capabilities and software tools of modern hybrid mass spectrometry (MS) instruments such as high-resolution mass spectrometry (HRMS), quadrupole time-of-flight (QTOF), and quadrupole linear ion trap (QLIT) were experimentally investigated for the study of emerging contaminants in Henares River water samples.

METHODS

Automated screening and confirmatory capabilities of QTOF working in full-scan MS and tandem MS (MS/MS) were explored when dealing with real samples. Investigations on the effect of sensitivity and resolution power influence on mass accuracy were studied for the correct assignment of the amoxicillin transformation product 5(R) amoxicillin-diketopiperazine-2',5' as an example of a nontarget compound. On the other hand, a comparison of quantitative and qualitative strategies based on direct injection analysis and off-line solid-phase extraction sample treatment were assayed using two different QLIT instruments for a selected group of emerging contaminants when operating in selected reaction monitoring (SRM) and information-dependent acquisition (IDA) modes.

RESULTS AND DISCUSSION

Software-aided screening usually needs a further confirmatory step. Resolving power and MS/MS feature of QTOF showed to confirm/reject most findings in river water, although sensitivity-related limitations are usually found. Superior sensitivity of modern QLIT-MS/MS offered the possibility of direct injection analysis for proper quantitative study of a variety of contaminants, while it simultaneously reduced the matrix effect and increased the reliability of the results. Confirmation of ethylamphetamine, which lacks on a second SRM transition, was accomplished by using the IDA feature.

CONCLUSION

Hybrid MS instruments equipped with high resolution and high sensitivity contributes to enlarge the scope of targeted analytes in river waters. However, in the tested instruments, there is a margin of improvement principally in required sensitivity and data treatment software tools devoted to reliable confirmation and improved automated data processing.

Fast separation liquid chromatography-tandem mass spectrometry for the confirmation and quantitative analysis of avermectin residues in food

A new residue analytical method for the confirmation and quantification of avermectin residues in food is described in this article. This method allows a fast analysis for the determination of avermectin residues, abamectin (ABM), ivermectin (IVM), emamectin benzoate (EMA) and doramectin (DOR) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Separation was performed using a short column of 1.8 microm particle size. The hybrid quadrupole/linear ion trap (QqQ(LIT)) system via the linearly accelerating (LINAC) high-pressure collision cell, allows the MS detection in multiple reaction monitoring (MRM) mode operating in fast scan acquisition times. The effect of reduced dwell times on mass spectral quality and sensitivity is evaluated in this study. For quantitative purposes, the influence of dwell time on S/N ratio and peak area was observed. ABM, IVM, EMA and DOR show an increased trend of peak area and S/N ratio, when dwell times are of 50 ms against 10-20 ms, suited when the number of compounds to be analyzed is higher. The sensitivity achieved by using the LC-MS/MS system is enough for the confirmation of avermectin residues in the selected commodities (salmon muscle and pepper) at trace concentration levels (sub-microg/kg and microg/kg) and therefore a sample pre-concentration step was not necessary. The instrumental limits of quantification (ILQ) are in the range of 0.15-5 ppb. Samples were extracted by solid-liquid extraction (SLE) procedure using acetonitrile, and cleaned-up using alumina. The average recoveries obtained were acceptable (80-95%). The calibration curves were linear over the working range from ILQs to 500 microg/kg. For the quantitative analysis, matrix-matched calibration and dilution of SLE extracts was proven as reliable alternative to compensate matrix-effects and for its feasible application in routine analysis.