Matrix-matched Calibration Curves Research Articles

Determination of 16 ultraviolet–absorbing compounds in marine invertebrates by using LC-USI-MS/MS coupled with QuEChERS

In this study, we examined multiple endocrine-disrupting ultraviolet-absorbing compounds (UVACs) in marine invertebrates used in personal care products and packaging. Modified QuEChERS and liquid chromatography UniSpray ionization tandem mass spectrometry were used to identify 16 UVACs in marine invertebrates. Matrix-matched calibration curves revealed high linearity (r ≥ 0.9929), with limits of detection and quantification of 0.006–1.000 and 0.020–3.000 ng/g w.w., respectively. In oysters, intraday and interday analyses revealed acceptable accuracy (93%–120%) and precision (≤18%), except for benzophenone (BP) and ethylhexyl 4-(dimethylamino) benzoate. Analysis of 100 marine invertebrate samples revealed detection frequencies of 100%, 98%, 89%, 64%, and 100% for BP, 4-hydroxybenzophenone, 4-methylbenzophenone, 4-methylbenzylidene camphor, and benzophenone-3 (BP-3), respectively. BP and BP-3 were detected at concentrations of 4.40–27.39 and < 0.020–0.560 ng/g w.w., respectively, indicating their widespread presence. Overall, our proposed method successfully detected UVACs in marine invertebrates, raising concerns regarding their potential environmental and health effects.

Emerging mycotoxin occurrence in chicken feed and eggs from Algeria.

Poultry farming has developed into one of Algeria's most productive industrial farming because of the growing demand for sources of protein among Algerian society. Laying hen feed consists mainly of cereals, which can be contaminated with molds and subsequently with their secondary metabolites known as mycotoxins. These later can pose a serious danger to the production and quality of eggs in the commercial layer industry. This work focuses on the detection of emerging mycotoxins, mainly enniatins (ENNs) and beauvericin (BEA), in poultry feed and eggs from different locations in Algeria. Two different QuEChERS-based extractions were established to extract ENNs and BEA from chicken feed and eggs. The determination of mycotoxin occurrence was achieved by a UHPLC-MS/MS method using 0.1% (v/v) formic acid in water and MeOH as mobile phase, an ESI interface operating in positive mode, and a triple quadrupole mass spectrometer operating in MRM for the detection. Matrix-matched calibration curves were carried out for both matrices, obtaining good linearity (R2 > 0.99). The method performance was assessed in terms of extraction recovery (from 87 to 107%), matrix effect (from - 47 to - 86%), precision (RSD < 15%), and limits of quantitation (≤ 1.1µg/kg for feed and ≤ 0.8µg/kg for eggs). The analysis of 10 chicken feed samples and 35 egg samples composed of a 10-egg pool each showed that ENN B1 was the most common mycotoxin (i.e., found in 9 feed samples) with contamination levels ranging from 3.6 to 41.5µg/kg, while BEA was detected only in one feed sample (12µg/kg). However, eggs were not found to be contaminated with any mycotoxin at the detection limit levels. Our findings indicate that the searched mycotoxins are present in traces in feed and absent in eggs. This can be explained by the application of a mycotoxin binder. However, this does not put a stop on the conduction of additional research and ultimately setting regulations to prevent the occurrence of emerging mycotoxins.

Validation of a modified QuEChERS method for the quantification of residues of currently used pesticides in Cuban agricultural soils, using gas chromatography tandem mass spectrometry

We present an analytical method to detect and quantify residues of currently used pesticides (CUPs), which include 31 active ingredients (ai) and seven transformation products (TPs) in tropical and agricultural soils of Cuba. Ten isotopically labeled analogous compounds served as internal standards (IL-IS). The novelty of this research is the inclusion of different tropical soils type scarcely studied for CUPs and TPs, based on the QuEChERS (quick, easy, cheap, effective, rugged and safe) method, followed by chromatography tandem mass spectrometry. All figures of merit proved to be satisfactory according to SANTE guidelines 2020 and 2021. Matrix effects (ME) calculated by the external standard method were significant (|ME| > 20% for almost all compounds; grand mean ± standard deviation (STD) 104 ± 108%) in all soils. The internal standard method compensated ME to non-significant levels (8 ± 50%), even for analytes with a non-structure identical IL-IS (STD, 13 ± 57%). Repeatability (relative standard deviation, RSDr) and reproducibility (RSDR) for skeletic regosol (SR) were 7.5 ± 2.8% and 11.7 ± 4.7%, respectively. Absolute (quantified for 11 analytes with structure identical IL-IS) and relative recovery from SR was 92 ± 13% (mean ± STD) and 90 ± 12%, respectively. Limits of quantification for SR ranged from 0.1 to 10 ng/g, except metalaxyl and oxyfluorfen (25 ng/g each). Linearity of matrix-matched (MM) calibration curves (5 to 100 ng/g) had an R2 of ≥ 0.99 for all soils and almost all analytes. The method was successfully applied to 30 real soil samples.

Procjena utjecaja matriksa na kvantifikaciju lipofilnih toksina u plodovima mora

Phycotoxin accumulation in seafood can cause human intoxication and significant economic losses in seafood-producing areas. To protect consumer safety, maximum permitted levels in bivalve molluscs have been set, with appropriate analytical methods for their determination and quantification. The reference method for lipophilic phycotoxins, commonly referred to as lipophilic toxins, is liquid chromatography tandem mass spectrometry (LCMS/MS method), where coeluting components from the matrix can affect the efficiency of ionisation, resulting in erroneous quantification. In this study, the matrix effect was evaluated using the slope ratio analysis method, which involves comparing the slopes of the calibration curves in the matrix with those in pure solvent. The extent of the matrix effect was investigated in mussels, oysters, queen scallops and ascidians. The study covered all phycotoxins under Regulation EU 853/2004 for which certified standards are commercially available, including unregulated pectenotoxin 2. The results indicated that all lipophilic toxins were susceptible to this effect when LC-MS/MS was used for their determination. Significant ion suppression was evident for most analytes in all matrices, except for okadaic acid and dinophysistoxin 2 in bivalves, where significant ion enhancement was demonstrated, and dinophysistoxin 1 in oyster and scallop extract where no significant effect on ionisation was observed. Further analysis revealed no significant differences between the slope of mussel matrix-matched calibration and that of other bivalve matrices. Given this minor difference, the mussel matrix-matched calibration curve could be applied to minimise the matrix effect and to quantify phycotoxins in bivalve matrices analysed here, with the exception of the okadaic acid group in ascidians, which requires matrix-matched calibration prepared with the blank extract of these mentioned species. Given the risks phycotoxins pose to human health, ongoing analytical method development is necessary in this field to properly control food safety and ensure consumer health.

Assessment of pheniramine in alternative biological matrices by liquid chromatography tandem mass spectrometry.

Pheniramine is an over-the-counter antihistamine drug. Its accessibility and low cost made it more popular among drug abusers in Pakistan. In this study, pheniramine was quantified in both conventional and alternative specimens of twenty chronic drug abusers, aged 16-50years, who were positive for pheniramine in comprehensive toxicological screening for drugs by gas chromatography with mass spectral detection in positive electron impact mode. Pheniramine was extracted from biological specimens using solid phase extraction and liquid chromatography tandem mass spectrometry was employed for quantification. Chromatographic separation was carried out on a Poroshell120EC-18 (2.1mm × 50mm × 2.7µm) column using water-acetonitrile in formic acid (0.1%) mobile phase in gradient elution mode with 500μL/min flow rate. Positive electrospray ionization mode and multi-reaction monitoring with ion transitionsm/z241.3 → 195.8 and 167.1 for pheniramine andm/zm/z247.6 → 173.1 for pheniramine-d6 were employed. The quantification method showed good linear ranges of 2-1000ng/mL in blood, urine, and oral fluid; 2-1000ng/mg in hair and 5-1000ng/mg in nail with ≥ 0.985% coefficient of linearity. The retention time of pheniramine was 3.0 ± 0.1min. The detection and lower quantification limits were 1ng/mL and 2ng/mL for blood, urine, oral fluid and hair whereas 2.5ng/mg and 5ng/mg for nail, respectively. Mean extraction recovery and ionization suppression ranged 86.3-95.1% and -4.6 to -14.4% in the studied matrices. Intra-day and inter-day precision were 4.1-9.3% and 2.8-11.2%, respectively. Pheniramine levels in specimens of drug abusers were 23-480ng/mL in blood, 72-735ng/mL in urine, 25-379ng/mL in oral fluid, 10-170ng/mg in hair and 8-86ng/mg in nail specimens. Alternative specimens are of utmost significance in clinical and medico-legal cases. In this study, authors compared matrix-matched calibration curves to blood calibration curve and obtained results within ± 10%; thereby justifying the use of blood calibration curve for urine, oral fluid, hair, and nail specimens.

Development and validation of a targeted mass spectrometry method for the quantification of milk protein allergens in multiple complex food matrices using matrix-independent calibration

Quantitative detection of food allergens is crucial in assessing the risk of allergic responses in susceptible individuals and ensuring regulatory compliance. Targeted mass spectrometry methods provide an opportunity to analyze allergens from complex, processed food matrices. However, probable interferences of diverse food matrices mandates preparation of matrix-matched calibration curves, challenging adaptation of methods into multiple matrices. In this study, we have developed a novel matrix-independent calibration strategy employing exogenous carrier proteins as background and demonstrated its adaptability in quantification of milk from multiple food matrices at concentrations relevant for risk assessment applications. Peptides representing casein or whey fractions of milk were detectable from concentrations as low as 1 ppm nonfat dry milk (NFDM) in baked cookie matrix at 46–99% accuracy, 0.5 ppm total milk protein (TMP) in pasteurized beverages at 94–138% accuracy, and 1 ppm casein in chocolate at 35–51% accuracy. Quantitative estimations of milk from matrix-independent calibration curves in the background of egg white powder as exogenous carrier were comparable to those from a matrix-matched calibration curve, and the quantitative precision was within 30% CV across the inter-day replicates. The sensitivity, accuracy, and precision of this matrix-independent approach ensure robustness of the method for high throughput food allergen analysis as required in routine testing labs.

Determination of erythromycin, clarithromycin and N-desmethyl-erythromycin A residues in pork, beef and lamb based on a simple and fast extraction procedure followed by ultrahigh-performance liquid chromatography with triple quadrupole/linear ion trap mass spectrometry

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was developed for the simultaneous determination of erythromycin (ERY), clarithromycin (CLA) and N-desmethyl-erythromycin A (N-D-ERY) in pork, beef and lamb via ultrahigh-performance liquid chromatography with triple quadrupole/linear ion trap mass spectrometry (UHPLC-QTRAP-MS/MS). The sample preprocessing and detection conditions were optimized, and the obtained parameters of all target compounds met the EU and FDA requirements. In the sample preprocessing procedure, acetonitrile-water (80:20, v/v) was used as an extractant, and a Cleanert MAS-Q cartridge was utilized and achieved good extraction recovery. The matrix-matched calibration curves showed good linearities, with determination coefficients of 0.9983–0.9999. The recoveries ranged from 88.96% to 101.76% with relative standard deviations (RSDs) ≤5.95%, and the intraday and interday RSDs ranged from 2.64% to 6.65% and 3.08–6.38%, respectively. The limits of detection and quantification for the pork, beef and lamb samples were 0.4 μg/kg and 2.0 μg/kg, respectively. The detection limits and detection capabilities were in the range of 2.15–215.16 μg/kg and 2.26–230.32 μg/kg, respectively. This method was successfully applied to the analysis of the pork, beef and lamb samples, demonstrating its applicability and suitability for the routine analysis of ERY, CLA and N-D-ERY residues in meat samples.

Simultaneous determination of five carbapenems, highly polar antibiotics, in milk by LC-MS/MS

The simultaneous determination of five carbapenems (biapenem, doripenem, ertapenem, imipenem, and meropenem) in raw and pasteurised bovine milk samples using LC-MS/MS was achieved and validated. Chromatographic separation was conducted on an InertSustain® AQ-C18 column using 0.1% formic acid in water and acetonitrile as the mobile phase. Target compounds were extracted using acetonitrile/water (20:80, v/v). After the removal of lipids with acetonitrile-saturated hexane, the dissolved protein was denatured with acetic acid. A portion of the supernatant was passed through an Oasis® PRiME HLB cartridge to remove the matrix. This novel method was validated in accordance with the Japanese validation guidelines and exhibited good trueness, ranging from 86.3% to 96.2%, using matrix-matched calibration curves. The relative standard deviation of repeatability ranged from 1.0% to 6.3%, and that of within-laboratory reproducibility ranged from 1.6% to 7.1%. The limit of quantification was 1.0 µg kg−1 for all analytes. None of the 60 milk samples commercially available in Tokyo contained any analytes. This novel method exhibited high-quality performance and can easily be implemented for the routine monitoring of carbapenems, which are highly polar antibiotics in milk.

Development and validation of a non-invasive method for quantifying amino acids in human saliva.

As an analytical matrix, saliva has superior characteristics than blood and urine. Saliva collection is, first and foremost, non-invasive, making it convenient, painless, and secure for more susceptible people. Second, it does not need professional training for medical personnel, resulting in cost-effectiveness and suitability for extensive collection in support of research. In this study, we developed a method and used it to quantify 13 salivary-free amino acid (SFAA) profiles to support the early clinical diagnosis of diseases using LC-MS/MS. Using an Intrada Amino Acid column (100 × 3 mm, 3 μm), chromatographic separation was accomplished with a binary gradient elution, and an electrospray ionisation source running in the positive ionisation mode was chosen for data collection using the multiple reaction monitoring (MRM) modes. Amino acids were extracted from saliva using acetonitrile. In the MRM mode, LODs and LOQs for ten amino acids were in the range of 0.06-2.50 μM and 0.19-7.58 μM, respectively, and those values were in the range of 1.00-3.00 μM and 3.00-8.50 μM, respectively, for three amino acids. Matrix-matched six-point calibration curves showed a linear correlation coefficient (r 2) of ≥0.998. Recovery experiments validated the method by spiking the control sample at three different concentration levels (5, 50 and 100 μM), and the accuracy level was 85-110%. Except for Thr and Ser, intra- (n = 3) and inter-day (n = 3) precision fell between 0.02 and 7.28. Salivary amino acids can serve as possible biomarkers for various malignancies, with fluctuations in body fluids being crucial for cancer diagnosis; therefore, examining amino acid patterns in saliva can assist in early cancer detection. LC-MS offers improved selectivity and sensitivity for non-derivatised amino acid analysis, surpassing conventional methods and offering proactive quality assurance, making it suitable for complicated sample matrices. These discoveries could be significant in investigating new pathways and cancer treatments and looking for possible AA biomarkers for other malignancies and diseases.

Evaluating the Presence and Depletion of Residual Ivermectin in Milk Following Subcutaneous Injections on Lactating Cows

Dairy farming industry in Kenya has experienced significant growth due to the rising consumption of milk and dairy products. Consequently, to improve output,veterinary drugs were administered prophylactically and/or therapeutically to dairy cattle. Commonly used drugs included beta-agonists, anthelmintics, antibiotics, and steroid hormones. Parasitic diseases more so tick infestations hindered production. Chemical methods were primarily used in tick management however, the technique proved expensive and developed resistance. Conversely, ivermectin effectively controlled ecto- and endoparasites in livestock, hence gaining popularity in tick management. Nonetheless, its residues accumulated in animal tissues, rendering it unacceptable on animals that produced milk for human use. Apparently, farmers in tick-infested areas in Nyandarua County, Kenya used ivermectin, but there lacked adequate evidence to show that it occurred in milk. Thus, this study examined the performance of Liquid Chromatography tandem mass spectrometry (LC-MS-MS) in order to analyse the presence and depletion pattern of ivermectin residues after it excreted in cow milk following subcutaneous treatment of dairy cows. Between day 0.5 and day 57 following treatment, 24 milk samples were purposefully collected and stored at -20°C.. The samples were prepared using QuEChERS, a solid-phase extraction technique.Further, positive Electrospray ionization (+ESI) LC-MSMS qualitative analysis identified a precursor ion with the mass number of m/z 897.5 and corresponding product ions—m/z 897.5 &gt; 329, m/z 897.5 &gt; 240, and m/z 897.5 &gt; 183—within a retention time of 8.782-8.858 (mean = 8.362±0.002) minutes. The solvent and matrixmatched calibration curves displayed satisfactory linearity with r=0.998 and 0.993 as their respective correlation coefficients. Additionally, the limit of detection was 2.5 ng/ml and limit of quantification reached 10 ng/ml. The analyte recovery ranged from 74.977% to 101.435%, within satisfactory limits. Hence, ivermectin residues were quantified in milk samples from the 0.5th to 17th day. The highest concentration (60.90±0.98 ng/ml) was observed on 2nd day. No traces of the residue were detected beyond day 18 and as a result, the study recommends a withdrawal period of 18days after subcutaneous ivermectin treatment. It is therefore important to perform further research on other dairy and animal products that people consume.

Determination of 45 Pesticides in Avocado Varieties by the QuEChERS Method and Gas Chromatography-Tandem Mass Spectrometry.

Gas chromatography (GC) tandem mass spectrometry (MS/MS) stands as a preeminent analytical instrument extensively employed for the surveillance of pesticide residues in food. Nevertheless, these methods are vulnerable to matrix effects (MEs), which can potentially affect accurate quantification depending on the specific combination of analyte and matrix. Among the various strategies to mitigate MEs, matrix-matched calibration represents the prevailing approach in pesticide residue applications due to its cost-effectiveness and straightforward implementation. In this study, a total of 45 representative pesticides were analyzed in three different varieties of avocado (i.e., Criollo, Hass, and Lorena) using the Quick-Easy-Cheap-Effective-Rugged-Safe (QuEChERS) method with ammonium formate and GC-MS/MS. For this purpose, 5 g of the avocado sample was extracted with 10 mL of acetonitrile, and then 2.5 g of ammonium formate was added to induce phase separation. Subsequently, the supernatant underwent a cleanup process via dispersive solid-phase extraction employing 150 mg of anhydrous MgSO4, 50 mg of primary-secondary amine, 50 mg of octadecylsilane, 10 mg of graphitized carbon black, and 60 mg of a zirconium oxide-based sorbent (Z-Sep+). The GC-MS/MS analysis was successfully performed in less than 25 min. Rigorous validation experiments were carried out to assess the performance of the method. The examination of a matrix-matched calibration curve for each variety of avocado revealed that the ME remained relatively consistent and less than 20% (considered as a soft ME) for most pesticide/variety combinations. Furthermore, the method´s limits of quantification were lower than 5 µg/kg for all three varieties. Finally, the recovery values for most pesticides fell within the acceptable range of 70-120%, with relative standard deviation values below 20%.

Simultaneous Screening and Quantification of 479 Pesticides in Green Tea by LC-QTOF-MS.

A high-throughput screening and quantification method for 479 pesticides in green tea was established based on solid-phase extraction combined with liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Pesticides were extracted from samples using an optimized SPE (TPT cartridges) procedure. LC-QTOF-MS in All Ions MS/MS scan mode acquired full MS data for quantification and product ion spectra for identification. LC-QTOF-MS quantification was achieved using matrix-matched standard calibration curves to achieve the optimal method accuracy. The method performance characteristics included the linearity, overall recovery, precision, and measurement uncertainty being evaluated. The validation results exhibited a good sensitivity with the LOQs of 5-55 µg/kg, which was satisfactory for their MRLs in China or the EU. The recoveries of more than 92.7% of the 479 pesticides in green tea were 70-120% at the three spiked levels with a precision of ≤20%. Finally, this method was employed to analyze 479 pesticides in 95 tea samples from markets in China. The test results of the tea samples showed that tolfenpyrad, buprofezin, and pyridaben were found with lower concentrations. The method has effectively improved the determination efficiency of pesticide residue screening by high-resolution mass spectrometry in green tea.

Detection and Quantification of Acrylamide in Second Trimester Amniotic Fluid Using a Novel LC-MS/MS Technique to Determine Whether High Acrylamide Content during Pregnancy Is Associated with Fetal Growth.

Acrylamide, an organic compound, is, chemically speaking, a vinyl-substituted primary amide. It is produced industrially, principally as a precursor to polyacrylamides, for use in such products as plastics and cosmetics. This same compound, however, forms naturally in certain foods, both home-cooked and packaged, especially when prepared at high temperatures. We developed and validated a novel reliable technique for the determination of acrylamide in amniotic fluid. Multiple reaction monitoring (MRM) is a targeted mass spectrometry (MS) technique which enables the detection and quantification of particular molecules in a complex mixture. Thanks to its throughput, selectivity, and sensitivity, MRM-MS has been identified as offering an alternative to antibody-based studies for the purpose of biomarker verification. Our aim was to investigate the presence of acrylamide in amniotic fluid and, via the MRM-MS technique, to determine whether there is any correlation between maternal exposure to acrylamide, through a woman's diet, and fetal growth. Our amniotic fluid bank included 40 samples from various fetal growth rates, as objectively denoted by the neonatal weight centile at delivery, while our analytical detection method was based on liquid chromatography-tandem mass spectrometry (LC-MS/MS). Acrylamide was determined with reversed phase chromatography and monitoring of two multiple reaction monitoring (MRM) transitions. Quantification was performed using the matrix-matched calibration curve. Acrylamide was detected at concentrations between 7.1 and 1468 ng/mL in six out of the total of 40 amniotic fluid samples that were used. Our method limit of detection and quantification was 1.4 ng/mL and 4.6 ng/mL, respectively. The repeatability of our method ranged between 11 and 14%, expressed as relative standard deviation levels between 5 and 100 ng/mL. Detection of acrylamide in early second trimester amniotic fluid, for the first time in the literature to our knowledge, raises concerns about fetal health, given that published data on animal studies have attributed a number of birth defects to acrylamide. Our novel LC-MS/MS method for the determination of acrylamide in amniotic fluid proved to be effective and its performance in practice was very accurate, simple, and fast. Validation of the method revealed that the use of a matrix-matched curve is necessary for the quantification.

Development and validation of an LC–MS/MS method for determination of tetrodotoxin and its analogues in various pufferfish tissues and its application in Korean pufferfish

A robust method was developed and validated for analyzing tetrodotoxin and its analogues (TTXs) in high- and low-fat tissues of pufferfish using LC–MS/MS. The tissue distribution of TTXs in four Takifugu pufferfish species and their phenotypic variants was determined using the validated method. A significant matrix effect was shown, and the matrix-matched TTX calibration curves (r2 > 0.999) were used for the analysis of TTX. The method detection limit for TTX ranged from 0.006 to 0.009 μg/g. Recoveries from TTX-fortified tissue samples (0.1–2.0 µg/g) were in the range of 96.1–107.3 % with RSDs less than 7.8 %. TTX levels in the pufferfish tissues reached a maximum of 1.32 × 104 µg/g. The developed method was used for the relative quantification of TTX analogues. The major TTX analogues were deoxyTTXs (i.e., trideoxy-, dideoxy-, and deoxyTTX). The ovary and liver of pufferfish showed higher concentrations of TTXs compared to other tissues. The developed method was successfully validated and applied to Korean pufferfish samples.

An integrated calibration strategy for the development and validation of an LC-MS/MS method for accurate quantification of egg allergens (Gal d 1–6) in foods

Accurate determination of egg allergens in food is vital for allergen management and labeling. However, quantifying egg allergens with mass spectrometry poses challenges and lacks validation methods. Here, we developed and validated an LC-MS/MS method for quantifying egg allergens (Gal d 1–6) in foods. Sample extraction, enzymatic digestion, purification, proteins/peptides selection, and calibration curves were optimized. VMVLC[+57]NR (Gal d 1) and GTDVQAWIR (Gal d 5) exhibited outstanding sensitivity and stability, serving as quantitation markers for egg white and yolk. Using a matrix-matched calibration curve with allergen ingredients as calibrants and labeled peptides as standards, we achieved highly accurate quantitation. Validation involved spiking egg protein into egg-free foods, showing excellent sensitivity (LOQ: 1–5 mg/kg), accuracy (62.4 %–88.5 %), and reproducibility (intra-/inter-day precision: 3.5 %–14.2 %/8.2 %–14.6 %). Additionally, we successfully applied this method to commercial food analysis. These findings demonstrate optimal allergen selection, peptides, and calibration strategy are crucial parameters for food allergen quantification via MS-based methods.

Determination of Tilmicosin in Bovine, Swine, Chicken, and Turkey Tissues by Liquid Chromatography With Tandem Mass Spectrometry, Single-Laboratory Validation.

An LC-MS/MS method was developed for determination and confirmation of tilmicosin in bovine, swine, chicken, and turkey tissues (liver, kidney, muscle, and skin/fat) and bovine milk. The method was subjected to single-laboratory validation to establish method performance parameters. Animal tissues and bovine milk were fortified at four concentrations ranging from 0.5 times the lowest maximum residue limit (MRL) or tolerance to 2 times the highest MRL or tolerance considering the Codex and EU MRLs and the US tolerances in the various tissues and milk studied. Incurred tissues were analyzed to verify the precision of the method. The data demonstrated linearity of matrix-matched calibration curves using a weighted (1/×) regression. Recoveries varied from 83.3 to 107.1%. Repeatability precision (RSDr) ranged from 0.465 to 13.4% and intermediate precision (RSDi) ranged from 2.24 to 14.7% in fortified tissue. Repeatability of the method was verified in incurred tissues, ranging from 3.41 to 16.0%. The limits of detection and quantitation of the method are presented and vary by matrix. One confirmatory transition ion was examined across all matrixes and met US and EU criteria for mass spectrometry confirmation. The method was shown to be robust when small changes in method parameters were made, and stability of the analyte in fortified tissues, extracts, standard solutions, and matrix-matched standards was estimated. The data satisfy the requirements of the AOAC Stakeholder Panel for Veterinary Drug Residue Methods for single-laboratory validation studies and the U.S. Food and Drug Administration Center for Veterinary Medicine Guidance for Industry #208 (VICH GL49). The LC-MS/MS method was demonstrated to be suitable for determination and confirmation of tilmicosin residues in bovine, swine, chicken, and turkey tissues and bovine milk based on Codex and EU MRLs and US tolerances.

Deep eutectic solvent-based dispersive liquid–liquid microextraction for determination of organochlorine pesticides in water and apple juice samples

In this work, we developed a deep eutectic solvent-based dispersive liquid–liquid microextraction (DES-based DLLME) method for the extraction and preconcentration of organochlorine pesticides (OCPs) from water and apple juice samples. Different DESs were synthesized by mixing menthol with carboxylic acids such as acetic, formic, and lactic acids. Among them, DES synthesized by mixing menthol with formic acid at a molar ratio of 1:1 showed the highest extraction efficiency for the target OCPs compared to other DESs. Various parameters affecting the method's extraction efficiency, including volume of DES, ionic strength, and centrifugation rate and time, were optimized. Under optimum conditions, matrix-matched calibration curves were separately constructed using water and apple juice samples. The obtained calibration curves have exhibited wide linearity ranges for both matrices. The limits of detections (LODs) and quantifications (LOQs) of the method ranged from 0.01 to 0.04, and 0.10–0.14 ng mL−1 for water and 0.05–0.09 and 0.22–0.41 ng mL−1 for apple juice samples, respectively. Similarly, the trueness of the method studied by spiking the samples at three concentration levels showed recovery values ranging from 80.1 to 112.5 % for both water and apple juice matrices. The findings demonstrated that the proposed DES-based DLLME method is rapid, simple, and environmentally benign. Thus, it could be used as an alternative method for determining OCPs in water, apple juice, and other related matrices.

Determination of glyphosate and aminomethylphosphonic acid residues in Finnish soils by ultra‐high performance liquid chromatography–tandem mass spectrometry

Glyphosate [N-(phosphonomethyl) glycine] (GLY) adsorbs strongly in Finnish soils. A new method for GLY and its main degradation product, aminomethylphosphonic acid (AMPA) residues in clay soils (Protovertic Luvisol) was developed and validated. A new method was necessary because the previous one required laborious cleaning pre-treatments, and its recovery was quite poor (<40%–70%). In the new method, the earlier method's extraction solvent, 0.1 M potassium hydroxide (KOH), was replaced by more effective 0.6 M KOH. The old post-column high-performance liquid chromatography and fluorescence (HPLC-FLD) method was replaced by the ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) method. Compounds were identified as their fluorenyl methyl chloroformate (FMOC) derivatives by a multiple reaction monitoring (MRM) technique and quantified by an internal standard method utilising multipoint matrix-matched calibration. Glufosinate-ammonium (GLUF) was used to monitor the effectiveness of extraction with good recovery (80–119%). All calibration curves were found to be linear (R2 ≥ 0.98) in the studied calibration range (0.01–3.31 mg kg−1 in fresh soil). The repeatability and reproducibility were 25% and 28% for GLY, and 20% and 24% for AMPA in real research soil samples. The method was effective throughout the calibration range in all the studied Finnish agricultural soils.•An improved method was created to analyse glyphosate (GLY) and AMPA in Finnish clay soil.•The challenge caused by strong GLY adsorption on soil was solved by using multipoint matrix-matched calibration curve samples which were prepared identically with the research samples.•The method performed well in all tested clay, loam and sandy loam soils.

Simultaneous Determination of 54 Pesticides in Proso Millet Using QuEChERS with Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

To assess the potential risks posed to the environment and human health, analyzing pesticide residues in proso millet is important. This paper aimed to develop a modified QuEChERS method with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of 54 pesticide residues in proso millet. Parameters including the mobile phase of the instrument, the acidity of the extraction solvent, and the type of absorbents were optimized to provide satisfactory performance. The method was validated concerning linearity, limit of quantification (LOQ), matrix effect, accuracy, and precision. In detail, the linearity of the matrix-matched calibration curve was acceptable with correlation coefficients (R2) higher than 0.99. The mean recovery was in the range of 86% to 114% with relative standard deviations (RSDs) ≤ 20% (n = 5). The LOQ was determined to be 0.25-10 μg/kg. The developed method was feasible for the determination of multiple pesticide residues in proso millet.

Determination of 80 pesticide residues in milk using NH_2-MWNTs by liquid chromatography-time of flight mass spectrometry

A method for the determination of 80 pesticide residues in milk by liquid chromatography-time-of-flight mass spectrometry(LC-QTof-MS) was developed. The target compounds in milk were extracted with acetonitrile-methanol(9∶1, V/V) containing 1% acetic acid, and purified by aminated multi-walled carbon nanotubes(NH_2-MWNTs). The chromatographic column was Waters Acquity UPLC BEH C_(18 )(100 mm×2.1 mm, 1.7 μm). The 80 pesticides were detected by liquid chromatography-time-of-flight mass spectrometry and quantified using an external standard method by matrix matched calibration curve. The purification method showed a good linearity(r~2≥ 0.99) over the concentration range from 5 to 100 μg/L for the 80 pesticides in this study. The limits of detection(LODs) and quantification(LOQs) of the 80 pesticides in milk ranged from 0.01 to 0.50 μg/L and 0.03 to 1.50 μg/L, respectively. The mean recoveries of the three spiked levels ranged from 71.5% to 116.9% with the relative standard deviation ranging from 1.2% to 18.1%, indicating that the accuracy and precision of the method were good. Among the milk samples, no residues of the 80 pesticides in this study were found after screening. The method has good linearity, good sensitivity, accuracy and precision and is suitable for the simultaneous and rapid determination of 80 pesticide residues in milk.