Identification of flavonoids in Hakmeitau beans (Vigna sinensis) by high-performance liquid chromatography-electrospray mass spectrometry (LC-ESI/MS)

Liquid chromatography coupled with electrospray mass spectrometry (LC-ESI/MS) with positive and negative ion detection was used for the identification of flavonoids in Hakmeitau beans, a black seed cultivar of cowpea (Vigna sinensis). Gradient elution with water and acetonitrile, both containing 2% formic acid, was employed in chromatographic separation. The peaks were identified by comparison of the retention times and the UV-vis spectroscopic and mass spectrometric data with authentic standards and/or literature data. The identified flavonoids included six anthocyanins (cyanidin 3-O-galactoside, cyanidin 3-O-glucoside, delphinidin 3-O-glucoside, malvidin 3-O-glucoside, peonidin 3-O-glucoside, and petunidin 3-O-glucoside) and four flavonol/flavonol glycosides (kaempferol 3-O-glucoside, quercetin, quercetin 3-O-glucoside, and quercetin 3-O-6' '-acetylglucoside). The tentatively identified flavonoids included two anthocyanins (malvidin 3-O-acetylglucoside and peonidin 3-O-malonylglucoside) and three flavonol glycosides (myricetin-3-O-glucoside, quercetin 7-O-glucoside, and quercetin-3-O-diglucoside). These flavonoids are present in seed coats, and the contents of anthocyanins and flavonol glycosides were 20.7 and 2.0 mg/g, respectively.     

Determination of trinexapac in wheat by liquid chromatography-electrospray ionization tandem mass spectrometry

A quantitative and confirmatory method for the analysis of trinexapac (free acid metabolite of trinexapac-ethyl) in wheat is described. Residues were extracted from wheat with acetonitrile in aqueous phosphate buffer (pH 7) overnight. The extract was directly injected into the HPLC system. Chromatographic separation was achieved on an octadecylsilica column, and detection was performed by negative ion electrospray ionization tandem mass spectrometry. The precursor ion of trinexapac [M - H](-) at m/z 223 was subjected to collisional fragmentation with argon to yield two intense diagnostic product ions at m/z 135 and 179, respectively. Accuracy and specificity for routine analysis of trinexapac were demonstrated. The validated concentration range was 10-200 microg/kg based on a 0.10 g/mL wheat sample extract. Recoveries were within the range of 71-94%, with associated relative standard deviations better than 10%. The limit of detection for trinexapac in wheat was estimated at 5 microg/kg. The method has been applied to a survey of 100 samples of wheat. In 46% of the samples analyzed, a quantifiable amount of trinexapac was detected, ranging from 10 to 110 microg/kg. It has been demonstrated that analyses of trinexapac accurately reflect the total amount of residues of the plant growth regulator, trinexapac-ethyl, in the wheat samples following field application. No residues of the parent compound, trinexapac-ethyl, in wheat were detected.     

Identification of the epsilon-(gamma-glutamyl)lysine cross-linking sites in alpha-lactalbumin polymerized by mammalian and microbial transglutaminases

To investigate the site specificity of two transglutaminases (TGases), that is, the enzymes from guinea pig liver (GTGase) and Streptoverticillium (MTGase), the acyl acceptor and donor sites in alpha-lactalbumin were determined. Alpha-lactalbumin was cross-linked in the presence of dithiothreitol by GTGase and MTGase for 15 and 30 min, respectively. Cross-linked alpha-lactalbumins by GTGase and MTGase were digested with lysylendopeptidase followed by the separation of the resulting peptides using reverse-phase HPLC. By the sequence analysis of the peptide fragments containing two N termini, which indicates the presence of cross-linked peptide, the lysine residues targeted by TGases were identified as follows: for GTGase, Lys16, Lys93, and Lys122; for MTGase, Lys5. These peptide fragments were further digested by V8 protease. Separation and sequence analyses of the resultant peptides were performed to identify glutamine residue involved in cross-linking. It was found that Gln54 was cross-linked to lysine residues by GTGase and MTGase in common. It is suggested that the difference in the numbers of lysine residues targeted by GTGase and MTGase may be responsible for the difference in the polymerization process of alpha-lactalbumin between GTGase- and MTGase-catalyzed systems.     

Profiling and quantification of isoflavonoids in kudzu dietary supplements by high-performance liquid chromatography and electrospray ionization tandem mass spectrometry

The kudzu vine (Pueraria sp.) is a rich source of isoflavones. Dietary supplements based on kudzu have become commercially available. In the present study, liquid chromatography coupled with negative and positive electrospray ionization tandem mass spectrometry (MS/MS) and diode array detection (DAD) has been used for the detection and characterization of isoflavonoids in kudzu dietary supplements (KDS). The MS/MS spectrum of the protonated ion of puerarin showed characteristic product ions of the C-glycoside unit itself, whereas daidzin generated an abundant Y(0)(+) aglycon ion in its product ion spectrum. A base peak due to the loss of 120 Da [M + H - 120](+) is the diagnostic ion for C-glycosides. Neutral loss scans allowed for the detection of other C- and O-glycosides in the methanolic extract of KDS, and their structures have been proposed. The concentration of isoflavonoids in the methanolic extract of commercially available KDS was quantified by using DAD-HPLC. Puerarin, rather than daidzin, was the most abundant component (8.44-30.60 mg/capsule) in commercially available KDS.     

Identification of flavonol and xanthone glycosides from mango (Mangifera indica L. Cv. "Tommy Atkins") peels by high-performance liquid chromatography-electrospray ionization mass spectrometry

Flavonol O- and xanthone C-glycosides were extracted from mango (Mangifera indica L. cv. "Tommy Atkins") peels and characterized by high-performance liquid chromatography-electrospray ionization mass spectrometry. Among the fourteen compounds analyzed, seven quercetin O-glycosides, one kaempferol O-glycoside, and four xanthone C-glycosides were found. On the basis of their fragmentation pattern, the latter were identified as mangiferin and isomangiferin and their respective galloyl derivatives. A flavonol hexoside with m/z 477 was tentatively identified as a rhamnetin glycoside, which to the best of our knowledge, has not yet been reported in mango peels. The results obtained in the present study confirm that peels originating from mango fruit processing are a promising source of phenolic compounds that might be recovered and used as natural antioxidants or functional food ingredients.     

Identification and quantification of betalains from the fruits of 10 mexican prickly pear cultivars by high-performance liquid chromatography and electrospray ionization mass spectrometry

Qualitative and quantitative analyses of betalain pigments in 10 cultivars/lines of prickly pear (Opuntia spp.) fruit grown in Mexico were conducted with reverse phase high-performance liquid chromatography-diode array detection (HPLC-DAD) coupled with electrospray mass spectrometry (ESI-MS). Betacyanins and betaxanthins were identified by comparison with the UV/vis and mass spectrometric characteristics as well as the retention times of semisynthesized reference betaxanthins. Data revealed that the ratio and concentration of betalain pigments are responsible for the color in the different cultivars, showing the highest betalains content in the fruit of purple colored Camuesa (O. robusta Wendl.) (8.1 mg/g dry fruit), which is comparable to that found in red beet Beta vulgaris L. ssp. Var. Pablo) (8.6 mg/g dry tissue). Yellow betalains were absent in Reyna (O. alba-carpa) prickly pear cultivar. A total of 24 known/unknown betalains were present in the prickly pear fruit samples studied, including 18 betaxanthins and 6 betacyanins. Our results indicate that prickly pear cultivars can be considered as a potential source of yellow and red natural colorants.     

Identification of betalains from yellow beet (Beta vulgaris L.) and cactus pear [Opuntia ficus-indica (L.) Mill.] by high-performance liquid chromatography-electrospray ionization mass spectrometry

Betaxanthins, the yellow-orange water-soluble pigments from yellow beet (Beta vulgaris ssp. vulgaris cv. Bejo Zaden) and cactus pear (Opuntia ficus-indica cv. Gialla) have been investigated using an HPLC system compatible with mass spectrometry. Five novel betaxanthins were found and characterized as the immonium adducts of betalamic acid with serine, gamma-aminobutyric acid, valine, isoleucine, and phenylalanine. To enable concentration of betalain samples, desalting was performed by solid-phase extraction. With this technique, betacyanins could be separated from the betaxanthins using the pH-dependent retention characteristics of red and yellow betalains. The betaxanthin fraction was taken for the preparation of betalamic acid as a precursor for semisynthetic standards. The HPLC method was applied to yellow beet and cactus pear, revealing a more complex betalain profile than described earlier, thus proving its suitability for screening of betaxanthin-containing plants as potential sources for natural food colors.     

Determination of saponins in aerial parts of barrel medic (Medicago truncatula) by liquid chromatography-electrospray ionization/mass spectrometry

Triterpene saponins from aerial parts of Medicago truncatula cv. Jemalong A-17, M. truncatula Gaertn.var. longispina Urb., and M. truncatula Gaertn. var. truncatula were profiled and quantified using reverse-phase liquid chromatography with on-line photodiode array detection and electrospray ionization mass spectrometry (LC-PDA/ESI/MS/MS). The determination was based on standard curves obtained for the 18 available saponin standards, previously isolated from Jemalong A-17. Aerial parts of all three subspecies contained 17 saponins previously identified and also a substantial amount of astragaloside VIII (3-GlcA-Xyl-Rha soyasapogenol B), not previously reported in M. truncatula. The compositions of saponin mixtures were very similar in the three subspecies with three dominant groups, recognized as zanhic acid, medicagenic acid, and soyasapogenol glycosides. Relative proportions of these three groups were also similar in the three subspecies: var. longispina had 49.5, 48.1, and 2.4%; var. truncatula, 41.5, 53.4, and 5.1%; and Jemalong A-17, 42.1, 56.6, and 1.3% of zanhic acid, medicagenic acid, and soyasapogenol glycosides, respectively. Jemalong A-17 had 30% lower total content of saponins as compared to M. truncatula var. longispina and M. truncatula var. truncatula; in relation to the dry matter, var. longispina contained 0.22%, var. truncatula, 0.22%, and Jemalong A-17, 0.15% dry matter of saponins. If one takes into consideration that this determination was performed on spring-collected samples, it can be concluded that the concentration of saponins in M. truncatula is similar to the concentration in alfalfa (Medicago sativa); the proportions of the three groups of saponins in these species are slightly different from those found in alfalfa, having a higher content of zanhic acid glycosides.     

Determination of furaltadone and nifursol residues in poultry eggs by liquid chromatography-electrospray ionization tandem mass spectrometry

The use of nitrofurans as veterinary drugs has been banned from intensive animal production in the European Union (EU) since 1993. The objective of the present study was to evaluate the accumulation and depletion of furaltadone and nifursol and their side-chain metabolites 5-methylmorpholino-3-amino-2-oxazolidinone (AMOZ) and 3,5-dinitrosalicylic acid hydrazide (DNSAH) in eggs after administration of therapeutic and subtherapeutic doses of the drugs to laying hens during three consecutive weeks. LC-MS/MS, with positive and negative electrospray ionization methods, was used for the determination of parent compounds and metabolites in yolk and egg white and was validated according to criteria established by Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) of the analytical methodology for metabolites were 0.1 and 0.5 μg/kg for AMOZ and 0.3 and 0.9 μg/kg for DNSAH, respectively. For the parent compounds, CCα and CCβ were 0.9 and 2.0 μg/kg for furaltadone and 1.3 and 3.1 μg/kg for nifursol, respectively. The data obtained show that the parent compounds are much less persistent than their side-chain metabolites in either yolk or egg white. Between the studied metabolites, AMOZ is the most persistent and could be detected in either yolk or egg white three weeks following withdrawal from treatment.     

Determination of 12 type A and B trichothecenes in cereals by liquid chromatography-electrospray ionization tandem mass spectrometry

A new sensitive method for the simultaneous determination of 12 trichothecenes (deoxynivalenol, nivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, fusarenon X, T-2 toxin, HT-2 toxin, neosolaniol, monoacetoxyscirpenol, diacetoxyscirpenol, T-2 triol, and T-2 tetraol) by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) is presented. The development of the method and investigations on the matrix influence on the MS signal are described in particular. The matrix effect was thereby minimized by using an internal standard, a special mobile phase, and specific fragmentation parameters. The sample was extracted with acetonitrile/water (84:16, v/v), and the extract was cleaned up with a MycoSep 227 column. Quantification was based on the internal standard de-epoxy-deoxynivalenol. Calibration curves were linear between 16 and 1600 ng/g, and the limits of detection ranged from 0.18 to 5.0 ng/g. The developed method was applied for the determination of trichothecenes in 120 naturally contaminated wheat and oat samples.     

Analysis of fumonisin B(1) in Fusarium proliferatum-infected asparagus spears and garlic bulbs from Germany by liquid chromatography-electrospray ionization mass spectrometry

Fusarium proliferatum is one of a group of fungal species that produce fumonisins and is considered to be a pathogen of many economically important plants. The occurrence of fumonisin B(1) (FB(1)) in F. proliferatum-infected asparagus spears from Germany was investigated using a liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method with isotopically labeled fumonisin FB(1)-d(6) as internal standard. FB(1) was detected in 9 of the 10 samples in amounts ranging from 36.4 to 4513.7 ng/g (based on dry weight). Furthermore, the capability of producing FB(1) by the fungus in garlic bulbs was investigated. Therefore, garlic was cultured in F. proliferatum-contaminated soil, and the bulbs were screened for infection with F. proliferatum and for the occurrence of fumonisins by LC-MS. F. proliferatum was detectable in the garlic tissue, and all samples contained FB(1) (26.0-94.6 ng/g). This is the first report of the natural occurrence of FB(1) in German asparagus spears, and these findings suggest a potential for natural contamination of garlic bulbs with fumonisins.     

Development of a new high-performance liquid chromatography-electrospray ionization time-of-flight mass spectrometry method for the determination of low molecular mass organic acids in plant tissue extracts

A liquid chromatography-electrospray ionization time-of-flight mass spectrometry method has been developed for the direct and simultaneous determination of 10 low molecular mass organic acids in different plant tissue extracts. The method does not include a derivatization step. Quantification was accomplished using (13)C-labeled malic and succinic acids as internal standards. Good limits of detection (0.05-1.27 pmol) were obtained for malic, 2-oxoglutaric, succinic, quinic, shikimic, cis-aconitic, and citric acids, whereas for oxalic, ascorbic, and fumaric acids limits of detection were 255, 25, and 11 pmol, respectively. Repeatability values for the retention time and peak area were <5%, with the exception of ascorbic acid. Analyte recovery was between 92% and 110% in most cases, with the exception of oxalic (39-108%), 2-oxoglutaric (44-69%), and ascorbic (22-86%) acids, which may require specific extraction procedures and use of the corresponding (13)C-labeled organic acid as internal standards to improve accuracy. The method was applied to three types of plant materials: sugar beet leaf extracts, tomato xylem sap, and commercial orange juice.     

Identification of olive (Olea europaea) pulp proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nano-liquid chromatography tandem mass spectrometry

Proteins in the pulp of olive ( Olea europaea ) constitute a minor fraction. They have been sparsely studied despite their suggested role in oil stability and olive allergenicity. The analysis of a pulp protein extract by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a major band at 24 kDa that was subjected to tryptic in-gel digestion. Peptide extracts were analyzed by MALDI-TOF MS and nanoLC-MS/MS. The use of different search engines enabled the assignment of a number of fragmentation spectra to peptide sequences, identifying a major band as a thaumatin-like protein and other low-abundant proteins such a drought-induced protein SDi-6-like, an acyl carrier protein, Cu/Zn and Mn superoxide dismutases, a small heat shock protein, and an ATP-dependent protease subunit. Many of the produced spectra did not give good matches in the database searches, due to the scarce presence of O. europaea entries in protein databases. Nevertheless, a huge number of spectra corresponded to peptides, which showed a high degree of homology with others from sequenced organisms. These results proved that database searching with MS/MS spectra constitutes a promising approach for the characterization of olive pulp proteins.     

Determination of five macrolide antibiotic residues in raw milk using liquid chromatography-electrospray ionization tandem mass spectrometry

A confirmatory method using liquid chromatography-electrospray ionization tandem mass spectrometry for determination of five macrolide antibiotics including spiramycin, tilmicosin, oleandomycin, erythromycin, and tylosin in raw milk is presented. Macrolides were extracted from raw milk by acetonitrile, and sample extracts were further cleaned up using solid-phase extraction cartridges. Data acquisition was achieved using multiple reaction monitoring, that is, two transitions, to provide a high degree of sensitivity and specificity. Matrix-matched standard calibration curves with the use of roxithromycin as an internal standard were utilized to achieve the best accuracy of the method. Both a conventional validation procedure and a designed experiment were applied to study the accuracy and precision of the method. The measurement uncertainty arising from accuracy and precision was estimated. The method accuracy, expressed as a percentage of overall recovery, was approximately 100%, and its intermediate precision was <10%. LC-ESI/MS/MS method detection limits (S/N > or = 3:1) of five macrolides were <0.3 microg/kg.     

Identification of betalains from petioles of differently colored Swiss chard (Beta vulgaris L. ssp. cicla [L.] Alef. Cv. Bright Lights) by high-performance liquid chromatography-electrospray ionization mass spectrometry

The betalain pattern of differently colored Swiss chard (Beta vulgaris L. ssp. cicla [L.] Alef. cv. Bright Lights) was investigated for the first time. Nineteen betaxanthins and nine betacyanins were identified by RP-HPLC and positive ion electrospray mass spectrometry, co-injection experiments with semisynthetic reference compounds, and standards derived from authentic plant material, respectively. Histamine-betaxanthin and alanine-betaxanthin were found to be novel betaxanthins, which to the best of our knowledge have not been reported as natural compounds until now. Furthermore, tyramine-betaxanthin (miraxanthin III) and 3-methoxytyramine-betaxanthin, which to date were known only from families other than the Chenopodiaceae, were detected for the first time in colored Swiss chard. The betacyanin pattern of purple petioles was composed of betanin, isobetanin, betanidin, and isobetanidin. Although phyllocactin was present in only trace amounts, further acylated structures such as betanidin-monoferuloyl-5-O-beta-diglucoside and lampranthin II, accompanied by their corresponding C(15)-epimers, were identified. In addition, quantification of betalains and CIE LCh degrees measurements were performed with the colored extracts to correlate the visual appearance with the respective pigment patterns. Besides the novel phytochemical findings, the present study is useful for the evaluation of betalainic Swiss chard as a potential coloring foodstuff.     

Identification of procyanidins in cocoa (Theobroma cacao) and chocolate using high-performance liquid chromatography/mass spectrometry

Monomeric and oligomeric procyanidins present in cocoa and chocolate were separated and identified using a modified normal-phase high-performance liquid chromatography (HPLC) method coupled with on-line mass spectrometry (MS) analysis using an atmospheric pressure ionization electrospray chamber. The chromatographic separation was achieved using a silica stationary phase in combination with a gradient ascending in polarity. This qualitative report confirms the presence of a complex series of procyanidins in raw cocoa and certain chocolates using HPLC/MS techniques. Although both cocoa and chocolate contained monomeric and oligomeric procyanidin units 2-10, only use of negative mode provided MS data for the higher oligomers (i.e., >pentamer). Application of this method for qualitative analysis of proanthocyanidins in other food products and confirmation of this method as a reliable quantitative tool for determining levels of procyanidins in cocoa, chocolate, and other food products are currently being investigated.     

Identification and characterization of anthocyanins by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry in common foods in the United States: vegetables, nuts, and grains

Anthocyanins in common foods in the United States, other than fruits and berries, were identified and characterized by high-performance liquid chromatography (HPLC)-electrospray ionization-tandem mass spectrometry coupled with diode array detection. Of all of the 40+ vegetables, nuts, and grains screened, seven vegetables, one nut, and one grain were found to contain anthocyanins; the number of anthocyanins detected varied from two in pistachio nuts to 34 in red radishes. The individual anthocyanins were identified by comparing their mass spectrometric data and retention times with those of standards, published data, and reference food samples. In all of the samples analyzed, except for sorghum, only six common anthocyanidins (delphinidin, cyanidin, pelargonidin, petunidin, peonidin, and malvidin) were found as their glycosides. Anthocyanins in certain vegetables such as red cabbage and red radish were highly conjugated with sugars and acylated groups, and thus, their structures were very complicated. Eight different either aliphatic or aromatic acylated groups (acetoyl, coumaroyl, malonoyl, p-hydroxybenzoyl, feruoyl, caffeoyl, sinapoyl, and oxaloyl) were identified in the anthocyanins. In addition to glucose, six other sugar moieties (galactose, xylose, rhamnose, rutinose, sambubiose, and laminaribiose) were observed. Three varieties of sorghum were found to contain 3-deoxyanthocyanidins and their derivatives as major anthocyanins. A number of new anthocyanins were identified in the foods studied. This paper presents complete HPLC profiles and MS spectrometric data, obtained under the same experimental conditions, for common vegetables, pistachio nuts, and sorghum that contain anthocyanins.     

Pharmacokinetic study of nobiletin and tangeretin in rat serum by high-performance liquid chromatography-electrospray ionization-mass spectrometry

Nobiletin (NOB) and tangeretin (TAN), two of the main polymethoxylated flavones (PMFs) in citrus, influence a number of key biological pathways in mammalian cells. Although the impacts of NOB and TAN on glucose homeostasis and cholesterol regulation have been investigated in human clinical trials, much information is still lacking about the metabolism and oral bioavailability of these compounds in animals. In this study, NOB and TAN were administered to rats by gavage and intraperitoneal (ip) injection, and the blood serum concentrations of these compounds and their main metabolites were monitored by high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS). In addition to the administered compounds, two metabolites of TAN and eight metabolites of NOB were detected and measured over 24 h. With identical oral doses, nearly 10-fold higher absorption of NOB occurred compared to TAN. For both compounds, maximum levels of glucuronidated metabolites occurred in the blood serum at later time points (～5-8 h) compared to the earlier T(max) values for NOB and TAN. In most cases the glucuronides occurred at substantially higher concentrations than the aglycone metabolites. Low levels of NOB and TAN and their metabolites were detectable in rat blood serum even at 24 h after treatment.     

Determination of oleandrin in tissues and biological fluids by liquid chromatography-electrospray tandem mass spectrometry

A rapid LC-MS/MS method, using a triple-quadrupole/linear ion trap mass spectrometer, was developed for the quantitative determination of oleandrin in serum, urine, and tissue samples. Oleandrin, the major cardiac glycoside of oleander (Nerium oleander L.), was extracted from serum and urine samples with methylene chloride and from tissues with acetonitrile. The tissue extracts were cleaned up using Florisil solid-phase extraction columns. Six replicate fortifications of serum and urine at 0.001 microg/g (1 ppb) oleandrin gave average recoveries of 97% with 5% CV (relative standard deviation) and 107% with 7% CV, respectively. Six replicate fortifications of liver at 0.005 microg/g (5 ppb) oleandrin gave average recoveries of 98% with 6% CV. This is the first report of a positive mass spectrometric identification and quantitation of oleandrin in tissue samples from oleander intoxication cases. The sensitivity and specificity of the LC-MS/MS analysis enables it to be the method of choice for toxicological investigations of oleander poisoning.     

Determination of low levels of perchlorate in lettuce and spinach using ion chromatography-electrospray ionization mass spectrometry (IC-ESI-MS)

A sample preparation method was developed to quantify environmentally relevant (low micrograms per liter) concentrations of perchlorate (ClO4(-)) in leafy vegetables using IC-ESI-MS. Lettuce and spinach were macerated, centrifuged, and filtered, and the aqueous extracts were rendered water-clear using a one-step solid-phase extraction method. Total time for extraction and sample preparation was 6 h. Ion suppression was demonstrated and was likely due to unknown organics still present in the extract solution after cleanup. However, this interference was readily eliminated using a Cl(18)O4(-) internal standard at 1 microg/L in all standards and samples. Hydroponically grown perchlorate-free butterhead lettuce was spiked to either 10.3 or 37.7 microg/kg of fresh weight (FW), and recoveries were between 91 and 98% and between 93 and 101%, respectively. Five types of lettuce and spinach from a local grocery store were then analyzed; they contained from 0.6 to 6.4 microg/kg of FW. Spike recoveries using the store-bought samples ranged from 89 to 100%. The method detection limit for perchlorate in plant extracts is 40 ng/L, and the corresponding minimum reporting limit is 200 ng/L or 0.8 microg/kg of FW.