A comparative study of the different analytical methods for analysis of S-allyl cysteine in black garlic by HPLC

A sensitive and reproducible analytical method to measure S-allyl cysteine (SAC) in black garlic was developed using the HPLC-FLD (fluorescence detection) with prior derivatization with AccQ-Fluor Reagent. The results were then compared with those from obtained using the HPLD-UVD (ultraviolet detection) that has been conventionally used for measuring SAC in raw garlic. The SAC content in raw garlic measured by the HPLC-FLD and the HPLD-UVD were 21.52 and 22.73 μg/g, respectively. And these results were satisfactory with %CV (coefficient of variation) less than 2%. However, the application of the HPLC-UVD for the determination of SAC in black garlic was limited due to the high %CV that arose from the unstable baseline. However, the HPLC-FLD could be applied to the measurement of SAC in black garlic with satisfactory %CV. The HPLC-FLD method was validated by determining the linearity, limit of detection, limit of quantification, accuracy and precision. This method showed excellent linearity with a coefficient of determination (R²) greater than 0.998. The limits of detection (LOD) and the limit of quantification (LOQ) were 6.28 and 19.02 μg/mL, respectively. The accuracy ranged from 98.51 to 102.08%, and the precision of the method was found to be less than 2%.     

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.     

The determination of vitamin D3 in bovine milk by liquid chromatography mass spectrometry

A renewed international interest in vitamin D status has revealed significant deficiencies in several populations, including Australia. Vitamin D exists in two forms, cholcalciferol (D₃) and ergocalciferol (D₂). The main source of vitamin D₃ is from exposure of 7-dehydrocholesterol present in the skin to UV irradiation. However, there is an absolute requirement for vitamin D through proper dietary intake if humans live in the absence of sunlight or exclusively indoors. Bovine milk is considered to be a good dietary source of vitamin D₃, even though the levels are quite low. This paper describes robust methods using liquid chromatography–linear ion trap mass spectrometry (LC–MSⁿ) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) to measure the levels of vitamin D₃ in fresh bovine milk (0.05 μg/100 ml), commercial (natural and fortified) milk samples (0.01–2 μg/100 ml) and a dairy based infant formula (8 μg/100 g), without the need for extensive clean-up procedures. The limits of quantification (LOQ) are 0.01 μg/100 ml and 0.02 μg/100 ml for LC–MSⁿ and LC–MS/MS, respectively. Recoveries of vitamin D₃ added to the samples prior to saponification were satisfactory (range 60–90%). 25-Hydroxyvitamin D₃ was not present in any of the samples analysed (LOQ = 0.01 μg/100 ml, recovery range 30–40%).     

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.     

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.     

Quantification of (+)-catechin and (−)-epicatechin in coconut water by LC–MS

An analytical technique has been developed to detect trace amounts of both (+)-catechin and (−)-epicatechin in the coconut water extract. Both (+)-catechin and (−)-epicatechin in the coconut water were found for the first time by the solid-phase extraction, and they were further analysed using liquid chromatography (LC)–ion trap mass spectrometry (MS) equipped with positive atmospheric pressure chemical ionisation interface on multiple reaction monitoring mode. The limit of detection and quantification for (+)-catechin were 7.8 and 15.6 μg/ml, respectively, while those for (−)-epicatechin were 3.9 and 7.8 μg/ml, respectively. The average concentration of (+)-catechin and (−)-epicatechin in the coconut water was 0.344 and 0.242 μg/ml, respectively. The LC–MS/MS analysis accelerated the quantitative analysis of (+)-catechin and (−)-epicatechin in the coconut water extract with high accuracy, precision and recovery. Results obtained in this study will serve as quality control and useful reference for drug development.     

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.     

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%.     

Phenolic profile,antioxidants, and sensory acceptance of bioactive-enhanced peanuts using ultrasound and UV

Phenolic antioxidant compounds, including resveratrol, are associated with reduced risk of cancer and cardiovascular disease, and delayed ageing. This study aims to quantify synergistic enhancement of phenolics and antioxidants in peanuts by combinations of ultrasound (US)–UV treatments, compared to either US or UV, and determine optimum parameters for combined US–UV process. LC–MS confirmed the bioactive phenolics: trans-resveratrol, trans-piceid, and p-coumaric-, caffeic-, and ferulic-acids, which achieved maximum increases, with combined US–UV, compared to US or UV; as did total phenolics (TP), TEAC, and ORAC. Optimum parameters for a combined US–UV process will provide up to 4.8 μg/g trans-resveratrol, 170 μg/g p-coumaric acid, and 150 μM TE/g ORAC or >100% that found in red wines; 1.0 μg/g trans-piceid, 2.6 μg/g ferulic acid, 1.48 mg GAE/g TP, and consumer acceptance ?5. Optimum combined US–UV resulted in 1.3× or 2.3× the trans-resveratrol concentrations in US or UV, respectively, suggesting synergistic effect of UV and US in enhancing resveratrol in peanuts.     

LC–MS/MS analysis of phenols for classification of red wine according to geographic origin,grape variety and vintage

A rapid LC–MS/MS method for quantification of phenols and polyphenols in authentic wine samples with unrivalled sensitivity was developed. Excellent limits of detection in the low μg L⁻¹ range were achieved. Reversed phase HPLC employing sub-2 μm particles as stationary phase allowed high-throughput analysis with analysis times of 10 min for 11 compounds. The phenolic pattern was assessed in 97 authentic wine samples (stored under identical conditions without further treatment or modification) comprising eleven geographical Austrian regions, six grape varieties and five vintages. Canonical discriminant analysis was applied to the data set showing the suitability of the (poly)phenolic spectrum for classification of the wine samples. The method allowed a geographic discrimination of several grape varieties and a grape variety based discrimination of four regions. As a novel finding excellent (poly)phenol-based differentiation of the five investigated vintages (2003–2007) was achieved.     

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.     

Sterigmatocystin presence in typical Latvian grains

Ninety five samples of different Latvian grains (wheat, buckwheat, barley, oats and rye) from the year 2006 and 120 samples from the year 2007 were analyzed for Aspergillus ssp. mycotoxin–sterigmatocystin (STC) content. 13.7% of the analyzed 2006 year samples were positive for STC with the concentration levels ranging from <0.7 to 83 μg/kg and 35% of the analyzed 2007 year samples were positive for STC with the concentration levels ranging from <1 to 47 μg/kg. A previously developed sensitive LC – Electrospray Positive Ionization – MS/MS method was applied for the analysis of STC in grains. Method includes sample extraction with acetonitrile/water solution, solid phase extraction (SPE) on Strata X SPE column, separation on reversed phase C₁₈ column and STC detection by LC–MS/MS.     

Exploration of Vanilla pompona from the Peruvian Amazon as a potential source of vanilla essence: Quantification of phenolics by HPLC-DAD

This study provides the first chemical investigation of wild-harvested fruits of Vanilla pompona ssp. grandiflora (Lindl.) Soto-Arenas developed in their natural habitat in the Peruvian Amazon. Flowers were hand-pollinated and the resulting fruits were analysed at different developmental stages using an HPLC-DAD method validated for the quantification of glucovanillin and seven other compounds. The method showed satisfactory linearity (r² > 0.9969), precision (coefficient of variation <2%), recoveries (70–100%), limit of detection (0.008–0.212 μg/ml), and limit of quantification (0.027–0.707 μg/ml). The evaluation of crude and enzyme-hydrolyzed Soxhlet-extracted samples confirmed the leading role of glucosides in fruit development. LC–ESI-MS studies corroborated the identities of four glucosides and seven aglycones, among them vanillin (5.7/100 g), 4-hydroxybenzyl alcohol (3.6/100 g), and anisyl alcohol (7.1/100 g) were found in high concentrations. The attractive flavor/aroma profile exhibited by wild V. pompona fruits supports studies focused on the development of this species as a specialty crop.     

Determination of <Emphasis Type="Italic">Bacillus cereus</Emphasis> Emetic Toxin in Food Products by Means of LC–MS²

Cereulide is the heat-stable toxin produced by certain strains of Bacillus cereus. It is the main virulence factor of emetic B. cereus strains, which causes the emetic food poisoning syndrome, including rare fatal cases of food intoxications. Due to presumably low intoxication doses, a sensitive, specific, and robust technique is needed for its detection. In 2002, a LC–MS method was developed which allowed absolute quantification of cereulide using valinomycin as standard. This study describes the validation, according to the Commission Decision 2002/657/EC, of the LC–MS2 method, a tandem mass spectrometry technique, which guarantees lower detection limit and higher specificity. The LC–MS2 method, calibrated with valinomycin, was validated in rice and tested on various matrices (i.e., red beans, spices, and chili con carne) containing cereulide. The process combines a simple extraction step from the food matrix followed by LC–MS2 analysis and detection by ion trap mass spectrometer. The detection limit for cereulide in rice was 0.5 ng eq/g, which is 20 to 2,500 times lower than currently understood intoxicative doses between 10 and 1.280 ng/g previously reported for cereulide. The validated method was specific, sensitive, repeatable, and reproducible with recoveries ranging from 77% to 101%.     

Liquid chromatography–electrospray ionization–tandem mass spectrometry method for determination of twenty multi-class pesticide residues in cashew

This paper describes an analytical methodology employing the extraction QuEChERS (Quick, Easy, Cheap, Effective, Robust and Safe) method and liquid chromatography coupled to mass spectrometry using electrospray ionization source (LC–ESI–MS/MS). The methodology was validated for the determination of twenty multiclass pesticides in cashew. It was evaluated for selectivity, linearity, limits of detection (LOD) and quantification (LOQ), matrix effect, as well as the precision and accuracy in terms of percentage of recovery. Analyses were performed by selected reaction monitoring (SRM) using two transitions (precursor ion → ion product). All pesticides studied showed good linearity with correlation coefficient greater than 0.99. LODs and LOQs ranged from 0.10 to 0.25 ng g⁻¹ and 0.30 to 0.75 ng g⁻¹, respectively. Due to the complexity of the sample, study the effect matrix was performed. Cashew apples samples spiked (5, 50 and 100 ng g⁻¹) showed recovery results ranging from 66 to 119 g/100 g, and RSD ≤ 12%, which is in accordance with standard recommended by Brazilian rules (ABNT NBR 14029/2005), except simazine. The validated method was applied to commercial samples obtained in Fortaleza-CE, Brazil, but no contamination of pesticides residues was observed.     

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.     

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.     

LC–MS/MS coupled with QSAR modeling in characterising of angiotensin I-converting enzyme inhibitory peptides from soybean proteins

The importance of soy products in reducing the risk of cardiovascular disease is well documented. Our previous computation study has indicated the presence of several potent ACE inhibitory peptides within soybean proteins which needs to be identified. The aim of the study was to identify ACE inhibitory peptides from soy proteins using LC–MS/MS coupled with quantitative structure–activity relationship (QSAR) model. Soybean protein hydrolysate digested by thermolysin showed an IC₅₀ value of 53.6 μg/mL, decreased slightly to 51.8 μg/mL after adding pepsin, and increased to 115.6 μg/mL after adding trypsin. A total of 34 peptides were characterised from LC–MS/MS. Five novel tripeptides, IVF, LLF, LNF, LSW and LEF, with predicted IC₅₀ values lower than 10 μM were synthesized and validated. The results showed that soybean is an excellent source of ACE inhibitory peptides.     

LC/ESI–MS/MS method for the identification and quantification of spinosad residues in olive oils

This paper reports the use of liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) method for the identification and quantification of residues of the natural insect control agent Spinosad in olive oils. The method determines the active ingredients Spinosyns A and D and two minor metabolites Spinosyns B and K without laborious sample treatment. All four analytes are determined simultaneously in a single injection using positive electrospray ionisation LC–MS with multiple reaction monitoring (MRM). For the quantitative analysis of samples an external calibration curve was built. The calibration curves for each analyte were linear in the concentration range 20–500 ng/mL with a correlation coefficient ranging between 0.995 and 0.999. Results from spike and recovery experiments at levels of 100 and 200 ng/mL gave mean recoveries ranging from 87–116% with satisfactory precision (relative standard deviation (RSD) from 1–8%). The excellent selectivity and sensitivity allows quantification and identification of low levels of Spinosad in olive oils (limits of quantification (LOQs) 0.004–0.073).     

Determination of tetracyclines in pig and other meat samples using liquid chromatography coupled with diode array and tandem mass spectrometric detectors

Two high performance liquid chromatographic methods (HPLC–DAD and LC–MS/MS) were developed to analyze tetracycline (TC) residues in pig meat (pork) samples. The method involved a sample preparation using a solid–liquid extraction (SLE) by McIlvaine buffer, followed by a solid-phase extraction (SPE) clean-up using Strata-XL cartridges. The developed sample clean-up resulted in a selective chromatogram in the HPLC–DAD separation and a reduced matrix effect (ME) in LC–MS/MS analysis. Moreover, HPLC columns packed with core–shell particles were tested for separation, which further enhanced the sensitivity and the selectivity of determinations. The validation of the methods for pig samples was carried out according to European Union 2002/657/EC decision. In addition, validation was also performed for bovine, chicken, and turkey meat samples using HPLC–DAD method. The performance characteristics of determinations were evaluated with both spiked and incurred samples, and were systematically compared. LC–MS/MS technique was found to be more accurate for spiked samples; however, HPLC–DAD method resulted in more reliable concentrations for incurred samples.