Positive Matrix Effects Research Articles

Electrospun nanofibers for localized drug release of a neuroprotective natural extract of Usnea ghattensis

This research is based on the incorporation of the methanolic extract of the Usnea ghattensis into poly (caprolactone) (PCL) nanofibers (NFs) to investigate the capacity in reducing reactive oxygen species (ROS). PCL-NFs were fabricated by the electrospinning technique and are investigated as potential dressing material focused on the release of usnic acid (PCL-USNIC NFs), and its encapsulation efficiency and kinetic release were analyzed by high performance liquid chromatography (HPLC). This investigation was performed by analyzing the usnic acid concentration as a function of the distance from the mat center point. The kinetic release analysis is also developed with the usnea ghattensis extract (PCL-USNEA NFs), performing a metabolomic analysis of the released molecules as a function of time by nuclear magnetic resonance (NMR). Usnic acid was revealed as the most relevant compound together with other molecules, such as sucrose, mannitol, arabitol or glycerol that generate a positive matrix effect on the release of usnic acid. Finally, we analize the cytotoxicity and the neuroprotective effect of PCL-USNEA and PCL-USNIC NFs using a human neuroblastoma cell line model. Negligible toxicity was appreciated for both polymeric systems, showing high protective effects in presence of highly oxidative environment (e.g. in presence of H2O2).

Occurrence and Consequences of Matrix Effects in Simultaneous Multi-class LC-MS/MS Determination of Pesticides, Pharmaceuticals and Perfluoroalkylsubstances in Different Types of Groundwater

Matrix effects are a recent remarkable feature in quantitative LC-MS/MS analysis. In this work, the matrix effects of a multiclass mixture of 46 analytes - pesticides, pharmaceuticals and perfluoroalkylsubstances in different types of natural groundwater were studied. Groundwater samples were spiked with different standards from different chemical groups and determined by direct injection and liquid chromatography coupled to tandem mass spectrometry. Matrix effects were assessed by matrix factors calculated using the slope ratio technique. Groundwater samples were sampled in different boreholes in several places in Slovakia. The relationship with the various detected inorganic parameters was investigated and discussed. Most of the studied analytes showed negative matrix effects. Some analytes showed weak negative or positive matrix effects. The results show that average matrix factors obtained from different sampling sites are not a reliable tool and matrix effects need to be monitored depending on the sampling location. Only weak or no correlation of the matrix factors with the determined inorganic parameters was found. Geochemical composition of boreholes samples was determined and the differences in the macrochemical composition of the samples was evaluated. Model samples of ultrapure water enriched with NaCl, Na2CO3 and NaNO3 at various concentration levels were tested and the matrix effects were not observed. Other content of sample than cations Na+ were responsible for the matrix effects. It was found that the most affected compounds are sulfamethoxazole, sulfadiazine, metamitron, chloridazon and also caffeine. The results show that the detailed study is suitable as a tool for a deeper understanding of matrix effects in different types of groundwater. The proper ground water sample must be selected for reliable results of quantitative analysis.Graphical

Simultaneous detection of gizzerosine and its precursor histamine in feeds and raw materials using UHPLC–MS/MS to evaluate feed safety risks

Gizzerosine is a biogenic amine in feeds with a physiological toxicity 1,000 times that of its precursor, histamine, causing high mortality in poultry. Because feeds containing gizzerosine usually contain high concentrations of histamine, it is of great significance to establish a method for the simultaneous detection of gizzerosine and histamine for feed safety. Herein, we first developed a detection method using 50 % (v/v) acetonitrile(ACN) containing 1 % (v/v) ammonium hydroxide (AH) extraction to synchronously monitor gizzerosine and histamine in feeds and raw materials via UHPLC–MS/MS. Due to the serious positive matrix effect (ME) in existing LC–MS/MS, this study reduced the ME of samples by purifying the extract solution using a mixed-mode cation exchange based solid phase extraction column (MCX-SPE), and simultaneously obtained accurate quantities of 5–500 ng mL−1 gizzerosine and 25–2,500 ng mL−1 histamine. The limit of detection (LOD) values for gizzerosine and histamine were 1.02 ng mL−1 and 3.00 ng mL−1, respectively, which were approximately 390 and 8,000 times more sensitive than the maximum recommended dosage of gizzerosine (0.4 mg kg−1) and limitation standards of histamine (25 mg kg−1) in fish meal, respectively. The samples could only be evaluated in 2 h. The average recoveries of the 6 types of feeds and raw materials ranged from 79.73 % to 110.31 % with a relative standard deviation (RSD) ranging from 1.29 % to 13.35 %. The average recoveries of feeds were generally lower than those of raw materials. Our method was efficient, simple, rapid, accurate, sensitive, and suitable for the simultaneous quantitative analysis of gizzerosine and histamine contents in various feeds, which provided technical support for the quality evaluation of feeds.

Commutability of possible external quality assessment materials for progesterone measurement

BackgroundThe commutability of control materials used for external quality assessment (EQA) programs is of great importance. Evaluating the commutability of control materials is crucial to assess their suitability for EQA programs. MethodsForty-eight individual patient serum samples, commercial EQA samples, human serum pools (HSPs), commercially available sterile filtered charcoal stripped serum (CS) and swine serum were analyzed using the isotope dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) comparative method and six immunoassays for progesterone. The commutability was assessed according to the EP14-A2 guideline and the difference in bias approach, respectively. ResultsAccording to the EP14-A2 guideline, HSPs and CS were commutable for all the tested immunoassays, while swine serum showed positive matrix effects in some assays. Based on the difference in bias approach, a large number of inconclusive and noncommutable results appeared. ConclusionsThe commutability of the processed materials varied depending on which evaluation approach and criterion was applied. Noncommutability of the EQA materials was observed. And HSPs and CS were possible commutable candidate control materials according to the EP14-A2 guideline.

Evaluation of Matrix Effect of Chilli, Cabbage and Bitter Gourd in Multiclass Multi-pesticide Residue Analysis Using Gas Chromatography Mass Spectrometry (GC-MS)

Matrix effect of twenty three (23) multi-class pesticides in three different vegetables (Bitter gourd, Chilli, Cabbage) was evaluated using modified QuEChERS [Quick (Qu), Easy (E), Cheap (Ch), Effective (E), Rugged (R) and Safe (S)] coupled with GC-MS analysis. Validation parameters (linearity, LOD, LOQ, accuracy and precision) were determined for multi-residue analysis. The Horwitz ratio was used to explain for intra-laboratory precision. The matrix effect (% ME) for each pesticide in each vegetable was assessed based on the study of slope ratio of linearity curves obtained from solvent and respective vegetable matrix. Most of the compounds had positive matrix effect and cabbage was found to be the least sensitive matrix compared to others. Recovery study was carried out fortifying pesticide mixture prepared from both pure solvent and matrix. The values of recovery percentages were satisfactory when calculated with matrix matched standard mixture (79% to 108%), with an acceptable relative standard deviation (RSD) (<20%). The results of the present study truly revealed the influence of matrix in pesticide residue estimation.

Methodology for Analysis of UV Filters in Tilapia Using Off-line MSPD Followed by On-line SPE–LC/UV

A sensitive method was developed and validated for the determination of UV filters (oxybenzone, octocrylene, 4-methyl-benzylidene camphor, 2-ethylhexyl-4-methoxycinnamate and avobenzone) in tilapia muscle using matrix solid-phase dispersion followed by on-line solid-phase extraction–liquid chromatography/UV. The validation showed good linearity from 100 to 3600 ng g−1 with r2 values > 0.98. Precision values with relative standard deviations were < 24% for all analytes. The accuracy was evaluated with the recovery of spiked muscle samples, and it ranged between 89 and 96% for most analytes, except 2-ethylhexyl-4-methoxycinnamate. A positive matrix effect was observed for oxybenzone, so a matrix-matched calibration curve was used for quantitation purposes. This methodology was applied to incurred samples of fish exposed to the analytes for 3 days (100 μg L−1 each). Residual quantities of the contaminants were measured after 24, 48 and 72 h of exposure, and concentrations ranged between 400 and 2900 ng g−1. The developed method was able to quantify all of the target compounds at trace levels.

Analysis of polyhalogenated carbazoles in sediment using liquid chromatography–tandem mass spectrometry

The purpose of this study was to develop a novel and sensitive method for the analysis of carbazole and polyhalogenated carbazoles (PHCs) in sediment using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Briefly, 5.0 g of freeze-dried sediment samples were extracted with dichloromethane using pressurized liquid extraction (PLE). The extract was purified with Florisil solid phase extraction cartridge, filtered through 0.22 µm polytetrafluoroethylene filter using a glass syringe, followed by LC-MS/MS analysis. Besides parameters for LC-MS/MS analysis, sample preparation procedures (including solvents for PLE, sorbents for cleanup, and filters for sample filtration) were optimized. The limits of detection and limits of quantification of target compounds were in the ranges of 3.0 × 10−3 to 0.22 ng g−1 dry weight (d.w.) and 1.0 × 10−2 to 0.75 ng g−1 d.w., respectively. The recoveries of target compounds in the spiked sediments at 2.0 ng g−1 d.w. and 10 ng g−1 d.w. were 64.8–91.8% and 70.9–124.7%, respectively, with relative standard deviations being less than 13.2%. Except that 36-BCZ had positive matrix effects of 63.3%, the sediment matrices generally displayed low or medium negative matrix effects on the other target compounds during LC-MS/MS analysis. The developed method was applied in the analysis of carbazoles and PHCs in sediment samples from Jiulong River, Fujian, China and all the target compounds were detected in the samples.

Biomass-burning derived aromatic acids in NIST standard reference material 1649b and the environmental implications

Biomass burning is a serious problem in the environment and climate system. However, the source identification of biomass-burning aerosols was somewhat impeded, partly due to the difficulty in quantification of relevant molecular markers. In this study, we present reference values for five aromatic acids (including p-hydroxybenzoic, vanillic, dehydroabietic, syringic and p-coumaric acids) in the NIST Standard Reference Material (SRM) 1649b. The concentration of levoglucosan was also revisited. Notable positive matrix effect was found for vanillic, dehydroabietic, syringic and coumaric acid. Using the standard addition method, the average value of p-hydroxybenzoic, vanillic, syringic, dehydroabietic and p-coumaric acids in SRM 1649b were found to be 26.9, 9.53, 1.13, 7.60 and 1.66 μg g−1, respectively. The analytical method developed in this study was also applied to the PM10 samples from Beijing and PM2.5 samples from South Asia (Godavari, Nepal). The ratios of vanillic to p-hydroxybenzoic acid and syringic to vanillic acid further suggested that their biomass-burning types are mainly related to hard wood and herbaceous species (i.e., agricultural residues).

Liquid Chromatographic MS/MS Analysis of a Large Group of Insecticides in Honey by Modified QuEChERS

The analytical tool for analysis of pesticide residues in honey must still be improved. Therefore, a sensitive, selective, rapid, and reliable analytical method for the analysis of pesticide residue belonging to 29 different classes at very low concentration levels was developed. Over 130 insecticides were extracted from the honey matrix using different amounts of sample, concentrations of the extraction solvent, and cleanup sorbents. Acceptable extraction recoveries accounting for matrix effect were obtained using the cleanup sorbent combination chitosan/aluminum oxide/C8 (200/200/200 mg) and 1% FA in ACN. Determinations were made by liquid chromatography-tandem mass spectrometry (LC–MS/MS). For most compounds, the recoveries range from 70 to 120%, with relative standard deviations < 20%. Linear correlation coefficients (r2) were higher than 0.99 at concentration levels of 0.001–0.100 mg kg−1. A positive matrix effect was observed for up to 95% of organophosphates and 43% of pyrethroids and a negative effect for 37% of neonicotinoids. This work showed that the presented method is convenient and reliable for quick monitoring of insecticides in honey samples.

Validation of a method for extraction of polycyclic aromatic hydrocarbons from sewage sludge and analysis by GC-MS

ABSTRACTIn the present study, the solid–liquid extraction with low temperature purification was validated for the determination of 16 polycyclic aromatic hydrocarbons from sewage sludge by gas chromatography-mass spectrometry. Recoveries ranged 70–114% for naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene and chrysene, while the compounds benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene showed recoveries of between 40 and 70%. The relative standard deviation was less than 13% for all of the compounds. Negative matrix effect was observed on the 10 compounds with less retention time in the chromatographic analysis and positive matrix effect noticed on the others. The limits of quantification were from 2 to 20 μg kg−1, about 30 times less than the maximum residue limit allowed in sludge by the European Union. The validated method produced quantification of 11 PAHs in one sludge sample at concentrations ranging 20–2000 μg kg−1.

Matrix Effects in Detection of Phthalate Esters from Wheat by a Modified QuEChERS Method with GC/MS

Nowadays, there is a lack of information regarding the occurrence and the content of phthalate esters (PAEs) contamination in wheats. In this study, a QuEChERS-GC/MS method was validated to measure trace levels of 14 PAEs in wheats. The work also focused on the matrix effects (MEs) which were evaluated through the study of slope ratios obtained of solvent and wheat matrix curves. All of the PAEs had positive MEs, and the percentage values were in a range of 5.4% (diisobutyl phthalate) to 53.7% (di-n-hexyl phthalate). The average recoveries (spiked at 0.06, 0.20, and 0.60 mg kg−1) had been considered satisfactory values between 84.8 and 120.3% with relative standard deviations of 0.6–9.0% for intra-day precision and 1.0–8.6% for inter-day precision. The limits of detection and limits of quantification ranged from 0.1 to 2.5 μg kg−1 and 0.13 to 5.0 μg kg−1, respectively. Following the employment of a top-down empirical model, the relative expanded measurement uncertainties were in the range of 21–43% (coverage factor k = 2, at 95% confidence). Based on the established method, PAEs in seven commercial wheat were evaluated, where 5 out of 14 studied PAEs were revealed in all of wheats, ranging from 0.028 to 0.669 mg kg−1. One of them exceeded the upper limits 0.3 mg kg−1 set for dibutyl phthalate in China.

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.

Evaluation of QuEChERS Sample Preparation and Gas Chromatography Coupled to Mass Spectrometry for the Determination of Pesticide Residues in Grapes

An effective analytical method for pesticides multiresidue determination in grape samples was developed and validated. A modified quick, easy, cheap, effective, robust and safe (QuEChERS) method was used to extract the target compounds. Several sorbent materials were tested for the clean-up step using dispersive solid phase extraction (d-SPE) and Florisil® was selected. Samples extracts were evaporated before injection in the gas chromatography with mass spectrometry (GC-MS) system in order to improve detectability. Recoveries from blank samples spiked at 0.04, 0.3 and 1.0 mg kg−1 ranged from 95 to 102% with relative standard deviation (RSD) from 1.3 to 19.7%. Method limits of detection (LODm) and quantification (LOQm) ranged from 0.006 to 0.012 and 0.02 to 0.04 mg kg−1, respectively. The positive matrix effect caused an increase in the peak areas of all compounds and matrix matched calibration curve linearity (coefficient of determination, r2) was higher than 0.98 for all target analytes. The validated method was successfully applied for the determination of 19 pesticides in grape samples.

Evaluation of the Bias of Serum Magnesium Measurements and the Commutability of Processed Materials.

Measuring serum magnesium plays an important role in the diagnosis of diseases. The performance of serum magnesium measurements is most conveniently monitored by external quality assessment (EQA) or proficiency testing (PT) schemes. However, the commutability of EQA samples and calibrators is often unknown, and the effectiveness of EQA schemes is limited. We designed the present study to evaluate the matrix effects of processed materials and the accuracy of routine methods. Inductively coupled plasma mass spectrometry was applied as a comparative method, and 12 routine methods composed of 12 kits, their supporting calibrators, and a Hitachi 7180 automatic analyzer were chosen as the test methods. Serum from 48 single patients and 24 processed materials were quantified by the comparative and routine methods. The 95% prediction intervals and relative bias were calculated at three medical decision levels (0.60 mmol/L, 1.00 mmol/L, and 2.50 mmol/L) according to EP9-A2 and EP14-A2. The commutability of the materials was evaluated by comparing the values of the processed materials with the limit bias, and the accuracy of the routine methods was evaluated by the relative bias. The precision of all of the assays was good (total CV < 2.01%), and the decision coefficients were high, most were greater than 0.99. The 2013 and 2014 EQA samples showed positive matrix effects in some of the assays; the human serum pools were commutable in all of the assays; the certified reference materials were commutable in most of the assays; the calibrators showed matrix effects in some of the assays; the aqueous reference materials showed matrix effects in most of the assays and could only be used in the reference methods. For all of the assays, the range of the mean bias was -0.04 - 0.06 mmol/L (-4.52% - 7.20%), and the range of the expected bias at the three medical decision levels was -0.03 - 0.06 mmol/L (-4.27% - 9.30%) at 0.6 mmol/L, -0.05 - 0.06 mmol/L (-4.79% - 6.31%) at 1.00 mmol/L, and -0.364 - 0.10 mmol/L (-13.66% - 4.05%) at 2.50 mmol/L. For most of the assays, the biases were in an acceptable range, whereas the accuracy of some of the assays needs improvement. Human serum pools prepared from patient samples were commutable, and other materials still exhibited matrix effects.

Matrix effect in guava multiresidue analysis by QuEChERS method and gas chromatography coupled to quadrupole mass spectrometry

“Quick, Easy, Cheap, Effective, Rugged and Safe” (QuEChERS)-GC/MS analytical technique was used to evaluated matrix effect of twenty-two pesticides in guava. Validation parameters (selectivity, linearity, LOD, LOQ, accuracy and precision) were determined for multiresidue analysis. Statistical test (t-student) was applied to the coefficients of the curves obtained for the guava matrix. The matrix effect (ME) for each pesticide was evaluated through the study of slope ratios obtained of solvent and guava matrix curves. Most of the compounds had positive ME. The rates of recovery were satisfactory (73.97-119.38%), with a coefficient of variation (CV) less than 20%. Analysis of commercial guava samples showed the presence of 5 types of pesticides residues at levels ranging from 0.1 to 0.5mg·kg−1. The results reveal the presence of unauthorized pesticides for cultivation of guava. This data can assist government agencies to ensure food security.

Detection of some industrially relevant elements in water by electrolyte cathode atmospheric glow discharge optical emission spectrometry

An electrolyte cathode atmospheric glow discharge optical emission spectrometry (ELCAD-OES) method was developed for the detection of the industrially relevant In, Rh and Te in water samples. Acid/additive type, sample pH and flow rate were optimized. The UV–Vis spectrum was scanned for analytical lines, free from spectral overlap interferences, and sensitive enough for quantifying the analytes at mg L−1 or lower levels. In several cases, the background spectrum of the ELCAD hindered the use of conventional, resonant analytical lines in the UV due to overlaps with bands of molecular species (e.g., OH, NO, N2). Te and Rh showed lower emission intensities than In (determined at In I 451.1nm), even using the most sensitive, interference-free transitions (i.e., Te I 214.3nm, Te I 238.6nm and Rh I 437.5nm). The emission intensities were highly sample pH dependent, i.e., analytical signals could only be detected at pH levels lower than 2. Conversely, the use of acidity lower than pH1 caused lower plasma volume, due to its contraction into the sample introduction capillary, and discharge instability in terms of its frequent self-extinction. The detection limits for In, Rh and Te were 0.01, 0.5 and 2.4mgL−1, respectively. Calibration curves were linear up to 100–150mgL−1. The precision for In, Rh and Te in aqueous standards, expressed as relative standard deviation (RSD), was not higher than 4.6%, 6.4% and 7.4%, respectively. Samples with high salt content (e.g., well water) caused positive matrix effects (i.e., 2.0- to 3.6-fold signal enhancements), but also ~1.5 times higher RSDs.

Ultrasonic degradation of acetaminophen in water: Effect of sonochemical parameters and water matrix

This paper deals about the sonochemical water treatment of acetaminophen (ACP, N-acetyl-p-aminophenol or paracetamol), one of the most popular pharmaceutical compounds found in natural and drinking waters. Effect of ultrasonic power (20–60W), initial ACP concentration (33–1323μmolL−1) and pH (3–12) were evaluated. High ultrasonic powers and, low and natural acidic pH values favored the efficiency of the treatment. Effect of initial substrate concentration showed that the Langmuir-type kinetic model fit well the ACP sonochemical degradation. The influence of organic compounds in the water matrix, at concentrations 10-fold higher than ACP, was also evaluated. The results indicated that only organic compounds having a higher value of the Henry’s law constant than the substrate decrease the efficiency of the treatment. On the other hand, ACP degradation in mineral natural water showed to be strongly dependent of the initial substrate concentration. A positive matrix effect was observed at low ACP concentrations (1.65μmolL−1), which was attributed to the presence of bicarbonate ion in solution. However, at relative high ACP concentrations a detrimental effect of matrix components was noticed. Finally, the results indicated that ultrasonic action is able to transform ACP in aliphatic organic compounds that could be subsequently eliminated in a biological system.

Matrix effect and retention efficiency of hydrophilic-lipophilic balance cartridges in multi-residual determination of veterinary drugs in river water

Matrix effect is an important interfering factor in LC-MS quantitative analysis. In this paper, matrix effects and retention efficiencies of 33 veterinary drugs spiked in river water were studied on hydrophilic-lipophilic balance (HLB) cartridges of 3 brands (Waters, Supelco, and CNW), using LC-MS/MS for detection and reverse osmosis (RO) water as the control under 500-fold concentration. In RO water, only the exogenous matrix effects were observed on three brands of HLB cartridges. Most quinolones and tetracyclines showed positive matrix effects. Estrogens showed negative matrix effects on two brands of HLB cartridges. Sulfonamides were not obviously affected by matrix effects. Chloramphenicols showed negative matrix effects on one brand of HLB cartridge. In river water, matrix effects were different from those of the RO water due to the combined exogenous and endogenous interfering substances. Sulfonamides showed slight matrix effects as those in RO water. Most quinolones and tetracyclines showed positive matrix effects. Chloramphenicols and estrogens showed negative matrix effects. Compared to the external standard method, matrix matched calibration method effectively overcame the matrix effects with better quantitative results. The recoveries of 33 target veterinary drugs spiked in river water at 50 ng/L and 200 ng/L levels were in the ranges of 40.3%-146.0% (Waters), 37.8%-104.2% (Supelco), and 52.9%-150.1% (CNW) with RSDs (n = 4) of 0.2%-14.6%. The results indicated that there was no significant difference in the retention efficiency between the 3 HLB cartridges with the matrix matched calibration method. This study provided supporting data for the HLB cartridge selection in multi-residual determination of the veterinary drugs in river water samples.

Block-Copolymers of Polyacrylamide with Poly(Ethylene Oxide) Forming Intramolecular Polycomplexes

Diblock-copolymers of polyacrylamide (PAA) and monomethyl ethers of poly(ethylene glycol) (MEPEG) of different molecular weights (M vMEPEG = 7.5 ⋅ 102 − 5 ⋅ 103) are obtained. The positive matrix effect depending on the length of MEPEG chains is revealed. The copolymerization kinetics is measured by dilatometry and compared with that of AA homopolymerization. Molecular parameters of synthesized copolymers are determined by size exclusion chromatography (SEC). Structural investigations are carried out by differential scanning calorimetry (DSC).