Quantitative analysis of acrylamide in tea by liquid chromatography coupled with electrospray ionization tandem mass spectrometry

An effective sample preparation procedure was optimized and a liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the quantitative analysis of acrylamide in tea. [¹³C₃]-acrylamide was used as internal standard. Acrylamide was extracted at 25 °C for 20 min by 10 ml water followed by 10 ml acetonitrile, and then 4 g of magnesium sulfate and 0.5 g of sodium chloride were added to the above mixture under stirring thoroughly. In order to increase the response of acrylamide, 9 ml acetonitrile layer was taken and concentrated to 0.5 ml. Solid-phase extraction with an Oasis MCX cartridge was carried out for clean-up. The limit of detection (LOD) and limit of quantification (LOQ) were 1 and 5 ng/ml, respectively. The recovery efficiency of the extraction procedure ranged between 74% and 79%. The levels of acrylamide in 30 tea samples were less than 100 ng/g. Black, oolong, white and yellow tea samples had quite low acrylamide contents (<20 ng/g). Higher acrylamide levels occurred in baked, roasted, and one sun-dried green tea samples (46–94 ng/g).     

The influence of latitude on the concentration of vitamin D3 and 25-hydroxy-vitamin D3 in Australian red meat

There is little information on the vitamin D content of Australian red meat or on the possible influence of latitude on this content. To determine the content of vitamin D₃ and 25-hydroxy-vitamin D₃ (25OHD₃), lamb and beef were analysed from 34° S with LC–IT-MS. To investigate the possible influence of latitude on vitamin D in meat, the lean meat and fat from five cuts of beef were analysed from 17° S and 41° S. Lamb contained 0.10 μg vitamin D₃/100 g and 0.20 μg 25OHD₃/100 g lean meat, while beef contained 0.12 μg vitamin D₃ and 0.27 μg 25OHD₃/100 g (lean meat). Latitude had no effect on the vitamin D₃ (P = 0.21) or 25OHD₃ (P = 0.29) content of lean beef, but fat from cattle in the 17° S latitude group contained significantly higher (P < 0.01) concentrations of vitamin D₃ than fat from the 41° S group of cattle.     

Aflatoxins contamination in spices and processed spice products commercialized in Korea

A survey for total aflatoxins (aflatoxins B₁, B₂, G₁, and G₂) was conducted on 88 spices and processed spice products commercialized in Korea. The presence of aflatoxins was determined by high-performance liquid chromatography (HPLC) with fluorescence detector using immunoaffinity column clean-up. Total aflatoxins (AFs) are detected in 12 samples (13.6% of incidence) including seven red pepper powder, two red pepper pastes (Kochujang), two curry and one ginger product. The contamination levels are 0.08–4.45 μg/kg as aflatoxin B₁ and 0.08–4.66 μg/kg as AFs. The liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis on contaminated samples was conducted for the confirmation of detected aflatoxins. The 12 samples which showed aflatoxins by HPLC/FLD were confirmed as aflatoxins by LC–MS/MS.     

Arsenic speciation in white wine by LC–ICP–MS

This study deals with As speciation in white wine. Arsenic species were selectively determined by liquid chromatography–inductively coupled plasma–mass spectrometry (LC–ICP–MS). Separation of As species was performed using an anion exchange column with ammonium phosphate solution (pH 6.00) as mobile phase. Samples of 14 white wine produced in South America were analysed. They were 10-fold diluted in the mobile phase prior to analysis by LC–ICP–MS. Accuracy was evaluated by recovery tests, whereas As species recovery ranged from 95% to 106%. Additionally, the sum of arsenic species concentration found by LC–ICP–MS was in agreement with the total arsenic concentration determined by ICP–MS after sample digestion. Arsenic species detected were arsenite [As(III)], arsenate [As(V)] and dimethylarsinic acid (DMA). As(III) and As(V) were detected in all analysed wine samples and DMA was detected only in wines produced in Argentina. Results for As determination in samples were from 2.9 to 10.3, 8.6 to 17.8, and <0.45 to 1.07 μg L⁻¹ for As(III), As(V) and DMA, respectively.     

Determination of Gibberellin A3 residue in fruit samples by liquid chromatography–tandem mass spectrometry

A fast, simple, low cost, and high throughput method has been developed for the determination of Gibberellin A3 residue in fruit samples (apple, orange, peach, pear and grape). Analysis is performed by LC–MS/MS operated in the multiple reaction monitoring (MRM) mode, acquiring two specific precursor-product ion transitions per target compound. The method has been validated showing good linearity and selectivity. Limits of quantification (LOQs) were 10 μg kg⁻¹ for apple, orange, peach, pear and grape samples. The average recoveries, measured at three concentration levels (10, 20 and 200 μg kg⁻¹) were in the range 77.8–96.2% for the compound tested with relative standard deviations below 13.7%. The proposed method is rapid, simple and could be utilised for the routine analysis of Gibberellin A3 in fruit samples.     

Microwave-assisted extraction and determination of cyanuric acid residue in infant formula samples by liquid chromatography–tandem mass spectrometry

In the present work, microwave-assisted extraction method in combining with liquid chromatography–tandem mass spectrometry (LC–MS/MS) was proposed for the determination of cyanuric acid (CYA) in infant formula samples. The separation was performed on a MERCK ZIC HILIC column (150 × 2.1 mm i.d., 5 μm) with gradient elution of 20 mM ammonium acetate solution – acetonitrile. The method could respond linearly with cyanuric acid at concentrations from 1.0 to 50 ng mL⁻¹ with a quantification limit of 0.25 mg kg⁻¹. The intra- and inter-day precision was less than 4% and the recovery of the assay was in the range of 86.7–93.1%. In the analysis of practical spiked infant formula samples, the new method yielded satisfactory results. Due to its simplicity and accuracy the straightforward method is particularly suitable for routine cyanuric acid detection.     

Interference-free determination of acrylamide in potato and cereal-based foods by a laboratory validated liquid chromatography–mass spectrometry method

A simple and rapid method was developed and validated for the determination of acrylamide in potato and cereal-based foods by using a single quadrupole liquid chromatography–mass spectrometry (LC–MS) interfaced with positive atmospheric pressure chemical ionization (APCI+). Acrylamide was simply extracted with 0.01 mM acetic acid in a vortex mixer prior to LC–MS analysis. The applicability of validated method was shown for a wide range of processed foods including chips, fries, crisps, breads, biscuits and cookies. The mean recovery was found to be 99.7 with a repeatability of 1.8% in the range 100–1000 ng/g. During LC–MS analyses, the major interfering co-extractive was identified as valine which yields characteristic [M + H]⁺ and compound specific product ions having m/z of 118 and 72, respectively. Valine increased the baseline signal preventing accurate and precise quantitation, and resulted in poorer sensitivity in selected ion monitoring mode. The adverse effect of valine could be limited by instrumentally adjusted delay time or by solid-phase extraction with strong cation-exchanger sorbent.     

Identification of irradiated meats by determining o- and m-tyrosine as markers

To identify the irradiated meats, various parameters that affect extraction efficiency of tyrosine positional isomers were evaluated. The optimum procedure employed simple extraction by 0.1% formic acid and protein precipitation by acetone. Baseline separation for the extract was carried out on LC–fluorescence detection (FLD) and LC–tandem mass spectrometry (MS/MS). The LC–FLD and LC–MS/MS method had LOD of 1.7–2.1 and 0.3–0.5 ng/mL, respectively, and showed excellent linear correlation over three orders of magnitude, obtained ideal recoveries (78.68–88.90%) and RSD (≤ 8%). The methods were successfully applied in multiple samples. For o- and m-tyrosine, the order of descending trend was: chicken > beef > hairtail > pork and chicken > hairtail > beef > pork, respectively. The radiation dose could be quantitatively evaluated by the nonlinear correlation (y = A₀x² + A₁x + A₂) with coefficients of determination r² > 0.998 in individual meat samples.     

Simultaneous determination of bisphenol A,octylphenol, and nonylphenol by pressurised liquid extraction and liquid chromatography–tandem mass spectrometry in powdered milk and infant formulas

A new analytical method, using pressurised liquid extraction (PLE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS), was developed for the simultaneous determination of bisphenol A (BPA), octylphenol (OP) and nonylphenol (NP) in powdered infant formulas (IF) and powdered skimmed milk (PM). The analytes were extracted by PLE, using this optimised conditions: ethyl acetate as solvent, 70 °C of temperature, reversed-phase silica C₁₈ as dispersing agent and three cycles of extraction. The extracts were then injected in LC–MS/MS using a Gemini C₁₈ column and a mixture of 5% water and 95% methanol/acetonitrile, both with 0.1% ammonia, as a mobile phase. Recoveries at different fortification levels (0.5 and 0.05 mg kg⁻¹), were between 89% and 92% for BPA, 84 and 98% for OP, and 93% and 101% for NP. The method was applied to the analysis of samples of PM and IF, bought in Italian and Spanish markets. In positive samples, phenols concentration ranged from 0.07 to 1.29 mg kg⁻¹ for BPA, from 0.028 to 1.55 mg kg⁻¹ for OP and from 0.026 to 1.47 mg kg⁻¹ for NP.     

Determination of ionophores in raw bovine milk using LC–MS/MS: Application to residue surveillance

Residues of four ionophores (lasalocid, monensin, narasin, and salinomycin) in raw milk samples were extracted with acetonitrile and subsequently determined using liquid chromatography–tandem mass spectrometry. Ionophores could be determined down to 0.1 ng g⁻¹ level, without additional cleanup or concentration of the resulting extract. The analysis of a series of raw milk samples fortified at analyte concentrations ranging from 1 to 20 ng g⁻¹ yielded average accuracies ranging from 60.7% to 118.3% with percent relative standard deviations below 13%. During six months of a surveillance program, 1072 raw milk samples were collected from the transport chain of dairy producers in Alberta and analysed. Monensin was detected in 736 of 1072 samples tested at concentrations ranging from 0.10 to 0.53 ng g⁻¹ which is well below the current Canadian maximum residue limit of 10 ng g⁻¹.     

Liquid chromatography–tandem mass spectrometry for the determination of chrysoidine in yellow-fin tuna

A high performance liquid chromatography (HPLC) coupled to electrospray ionisation tandem mass spectrometry (MS/MS) method was described for the residue detection of chrysoidine in yellow-fin tuna in the present study. Samples were cleaned up with solid phase extraction (SPE) cartridge, and then injected into HPLC for separation. Multiple-reaction monitoring (MRM) was applied for quantitative determination. Results showed that the low limit of detection (LOD) of the method was 1.25 × 10⁻¹² g, and the low limit of quantification (LOQ) was 0.42 μg/L. The standard calibration curve was y = 2333.9x −845 (r² > 0.99) with the linear range of 0.63–100 μg/L. The average recoveries of chrysoidine ranged from 86.0% to 108.0% when the spiked concentration was from 0.5 μg/kg to 20 μg/kg. And the developed method also showed the good test precisions (RSD%: 4.38–14.27%).     

Naturally-occurring folates in foods: Method development and analysis using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

An accurate method for detecting and quantifying both synthetic (folic acid) and naturally-occurring folates in foods is described. A system capable of analysing the five most commonly occurring folates (pteroylglutamic acid, 5-methyltetrahydrofolate, tetrahydrofolate, 10-formylfolate and 5-formyltetrahydrofolate) in 20 min using liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. Quantification of folates was performed using ¹³C labelled internal standards. This paper outlines the development of a comparatively fast LC–MS/MS method, method validation using commercially available folate standards and establishment of the method’s suitability for quantification using selected reaction monitoring (SRM) mass spectrometry. The application of the system was verified by analysing several certified reference materials and comparing results with certified values as determined by microbiological assay. LC–MS/MS promises to be an ideal tool for the quantitative analysis of folates in food.     

Determination of aflatoxin levels in nuts and their products consumed in South Korea

A total of 85 nuts and their products marketed in South Korea were assessed for aflatoxins using a monitoring scheme consisting of enzyme-linked immunosorbent assay (ELISA) for rapid screening, high performance liquid chromatography (HPLC) for quantification and LC–mass spectrometry (MS) for confirmation. Thirty-one out of 85 samples gave ELISA readings above 0.06 and were screened as possible positive samples. Aflatoxin contents of possible positive samples were determined using HPLC with a detection limit of 0.08–1.25 μg/kg and a quantification limit of 0.15–2.50 μg/kg. Nine samples including 1 raw peanut, 4 roasted peanuts, 2 peanut butters, 1 pistachio and 1 seasoned assorted nut were contaminated with aflatoxins (10.6% of incidence), ranging in various levels up to 28.2 μg/kg. LC–MS analysis on contaminated samples revealed that peaks eluting at 4.4, 5.2, 9.1 and 11.9 min were confirmed as aflatoxin G₁, aflatoxin B₁, aflatoxin G₂ and aflatoxin B₂, respectively.     

Dissipation kinetics of forchlorfenuron, 6-benzyl aminopurine,gibberellic acid and ethephon residues in table grapes (Vitis vinifera)

The residue dynamics of plant growth regulators (PGR) forchlorfenuron (CPPU), 6-benzylaminopurine (6-BA), gibberellic acid (GA₃) and ethephon in grape are presented, corresponding to their field applications at recommended and double doses. Random samples were collected from each treated and control plot at regular time intervals. The optimised sample preparation technique involves extraction of 10 g homogenised sample with 20 ml methanol (+1% formic acid) and measurement by LC–MS/MS multiple reaction monitoring, offering limit of quantification ?0.0025 μg/g for all except ethephon with LOQ of 0.005 μg/g. The recoveries at LOQ and above were 84.8–109.5%. Residue dissipation of all the PGRs followed non-linear two-compartment first + first-order kinetics. CPPU, 6-BA and ethephon residues dissipated with preharvest intervals (PHIs) of 33.5, 12 and 32 days at recommended dose with no PHI applicable for GA₃. The PHIs successfully minimised residue problems as observed from survey results of traceable field samples.     

Rapid quantitation of curcumin in turmeric via NMR and LC–tandem mass spectrometry

A rapid, sensitive and accurate ¹H NMR method has been developed for the quantitation of curcumin isolated from Curcuma longa rhizome (turmeric) extract, the results of which were compared with a validated LC–MS/MS method. The relative standard deviations of the methods were found to be 2.49% and 3.48% for the ¹H NMR and LC–MS/MS methods, respectively. The correlation coefficients were 0.998 for ¹H NMR and 0.995 for LC–MS/MS assay in the calibration range. The recoveries at 5 mg mL⁻¹ and 50 μg mL⁻¹ concentrations averaged to 99–101% for both techniques, respectively. The uncertainty of the measurement of curcumin via ¹H NMR spectroscopy was determined to be 5.80% while in LC–ESI-MS/MS method was 7.38%.     

Identification and quantitative determination of glucosinolates in seeds and edible parts of Korean Chinese cabbage

Glucosinolates (GSLs) have attracted major interest due to the chemopreventive properties of some of their transformation products. GSLs in the seeds and edible parts of Korean Chinese cabbage (Brassicacampestris L. ssp. pekinensis) were identified and quantified by LC–ESI–MS and LC–UV. As a result, nine GSLs were identified: progoitrin, glucoraphanin, glucoalyssin, gluconapin, 4-hydroxy-3-indolylmethyl, glucobrassicanapin, glucoerucin, glucobrassicin, and 4-methoxyglucobrassicin. The total GSL levels were 268–198 and 23.0–15.8 μmol/g dry weight (DW) for seeds and edible parts, respectively. Gluconapin (197 μmol/g DW) was the highest individual GSL in seeds, whereas 4-methoxyglucobrassicin (6.08–4.94 μmol/g DW) and glucobrassicanapin (8.18–3.09 μmol/g DW) were found in the edible parts. In addition, LC–MS profiles of the nine GSLs identified from Korean Chinese cabbage were subjected to principal components analysis (PCA) to evaluate differences among samples. The metabolome among the four cultivar seed or edible parts was clearly separated by PCA.     

Development and validation of a new LC–MS/MS method for the simultaneous determination of six major ergot alkaloids and their corresponding epimers. Application to some food and feed commodities

A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of six major ergot alkaloids, ergometrine, ergosine, ergotamine, ergocornine, ergokryptine and ergocristine, as well as their corresponding epimers in food and feed samples. The method involves extraction under alkaline conditions and subsequent clean-up by applying a simple and rapid liquid–liquid partitioning procedure prior to LC–MS/MS analysis. Evaluation of the method revealed good linearity, accuracy and precision. The limits of quantification varied from 0.1 to 1 μg/kg depending on the analyte and matrix. The average extraction and clean-up recoveries in different matrices were between 45 (only for ergometrine in biscuit) and 90%. The uncertainty associated with the analytical method was not higher than 51% and 30%, at concentration levels of 2.5 and 150 μg/kg respectively. Analyte epimerization proved to be minimal during the analytical procedure. The method has been successfully applied to the determination of ergot alkaloids in some Belgian food and feed commodities. Ergot alkaloids were found in 104 out of 122 samples investigated. Ergosine was the most frequently occurring alkaloid, while the highest levels were observed for ergotamine, ergocristine or ergosine, depending on the product type. The total alkaloid content in positive samples varied from 1 to 1145 μg/kg.     

Quantifying fenobucarb residue levels in beef muscles using liquid chromatography–tandem mass spectrometry and QuEChERS sample preparation

This paper describes a comparison of the properties of the three versions of the QuEChERS method (quick, easy, cheap, effective, rugged and safe) – the original (unbuffered), acetate-buffered, and citrate-buffered methods – for the determination of fenobucarb residues in beef muscles via liquid chromatography–electrospray ionisation tandem mass spectrometry (LC–ESI⁺-MS/MS). The recovery results were good for all the versions; however, the acetate-buffered version gave higher and more consistent recoveries for fenobucarb than the other versions. Performance characteristics, such as linearity, accuracy, and precision were determined. Matrix-matched standard calibration was used for quantification, obtaining recoveries in the range of 83.7–93.4% with relative standard deviations of <5%, at two spiking levels: 10 and 40 μg/kg. The limits of detection (LOD) and quantification (LOQ) were estimated to be 1.5 and 5 μg/kg, respectively. Finally, the method was applied to the analysis of 15 market samples, and no residues were found over the limit of quantification. The method developed was found able to determine the analyte with satisfactory intensity and accuracy.     

Pressurised liquid extraction combining LC–DAD–ESI/MS analysis as an alternative method to extract three major flavones in Citrus reticulata ‘Chachi’ (Guangchenpi)

Pressurised liquid extraction (PLE) of three major flavones (hesperidin, nobiletin, and tangeretin) from the peels of Citrus reticulata ‘Chachi’ (Guangchenpi) was investigated. These flavones were quantified and analysed by liquid chromatography–diode array detector–electrospray ionisation mass spectrometry (LC–DAD–ESI/MS). The PLE procedure was optimised, validated and compared with other conventional extraction techniques. PLE gained the best result due to the highest extraction efficiency within the shortest extraction time. The optimal conditions of PLE were employing 70% methanol as extraction solvent at a temperature of 160 °C and extraction pressure of 1500 psi, using one extraction cycle with a static extraction time of 20 min. MS coupling with an ESI interface in the positive ion mode was used as the detection technique. This is the first report on combining PLE with LC–DAD–ESI/MS for the extraction and quantification of flavones in Citrus reticulata ‘Chachi’.     

Folate composition of 10 types of mushrooms determined by liquid chromatography–mass spectrometry

White button, crimini, shiitake, maitake, enoki, oyster, chanterelle, morel, portabella, and uv-treated portabella mushrooms were sampled from U.S. retail outlets and major producers. Folate [5-methyltetrahydrofolate (5-CH₃-H₄folate), 10-formyl folate (10-HCO-folate), 5-formyltetrahydrofolate (5-HCO-H₄folate)] was analysed using a validated LC–MS method in four composites of each product, including an in-house mushroom control composite and a reference material (BCR 485 Lyophilised Mixed Vegetables). Chanterelle and morel had the lowest total folate (2–6 μg/100 g), oyster had the highest (mean, 44.2 μg/100 g); other types contained 12.4 μg/100 g (shiitake) to 29.8 μg/100 g (vitamin D-enhanced portabella). Enoki and oyster had almost exclusively 5-CH₃-H₄folate. Morel and chanterelle contained predominately formyl folates. Other species had similar amounts of 5-CH₃-H₄folate and formyl folates. Enoki, oyster, and shiitake, unlike all others, had low to non-detectable 10-HCO-folate (<1 μg/100 g). These precise data on the composition of folate vitamers in different types of mushrooms will facilitate assessment of the dietary contribution of naturally occurring folate.