Disposable biosensor test for organophosphate and carbamate insecticides in milk

A highly sensitive and rapid biosensor test based on disposable screen-printed thick-film electrodes was developed, which is suitable for monitoring organophosphate and carbamate residues in foods of animal origin with increased fat contents such as milk. The wild-type enzyme was combined with three engineered variants of Nippostrongylus brasiliensis acetylcholinesterase (NbAChE), to obtain enhanced sensitivity. The sample pretreatment could be reduced to a minimum. There was no extraction or fat removal necessary. With the biosensor test paraoxon concentrations down to 1 microg/L could be detected in milk. The detection limit for carbaryl was 20 microg/L. Recovery rates for paraoxon and carbaryl in milk samples lay between 89 and 107%. Ten milk samples from local markets were tested both with the biosensor test and with standard chromatographic multiresidue methods. Two milk samples caused AChE inhibition rates of >50%. Accordingly, 4 microg/L tebufenpyrad, 4 microg/L tetraconazole, and 2 microg/L bifenthrin were detected in one of these milk samples. The other milk sample contained 2 microg/L tebufenpyrad.     

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.     

Determination of selenium in human milk by hydride cold-trapping atomic absorption spectrometry and calculation of daily selenium intake.

A technique of hydride cold-trapping atomic absorption spectrometry following microwave digestion was developed and optimized for the determination of selenium in human milk. The method was validated by the analysis of two standard reference materials (CRM milk powder). The detection limit was 0.5 ng mL(-)(1). The method was then used to analyze 78 milk samples from 38 Austrian mothers throughout their first 10 months of lactation. The mean concentration of selenium in the mother's milk decreased with the days postpartum from 23.9 +/- 12.0 microg L(-)(1) in colostrum to a plateau of 11.4 +/- 3.0 microg L(-)(1) in mature milk. On the basis of the milk selenium concentrations, the selenium intakes of the fully breast-fed infants and the lactating mothers were calculated. The selenium intake of the infants during their first 3 months of life was >8.2 microg day(-)(1). The selenium intake of the lactating mothers was 48 microg day(-)(1). Compared to the recommended dietary allowance, the fully breast-fed infants received sufficient selenium but the lactating mothers obtained less than the recommended.     

Simultaneous differential pulse polarographic determination of cadmium, lead, and copper in milk and dairy products

The contents of potentially toxic elements lead and cadmium and the essential element copper in various milk and dairy products consumed in Turkey were determined by differential pulse polarography (DPP), primarily to assess whether the intakes comply with recommended desired concentrations for essential and permissible levels for toxic elements. A simple and rapid DPP method has been developed for the simultaneous determination of cadmium, lead, and copper in samples. Using the differential pulse mode, half-wave peak potentials as E(1/2) were -0.58, -0.40, and -0.07 V for cadmium (Cd), lead (Pb), and copper (Cu), respectively. Marketed formulations of dairy products have been analyzed by calibration and standard addition methods. Recovery experiments were found to be quantitative. The linear domain ranges were 0.00-674.28 microg/L for Cd (R2 = 0.9999), 0.19-2.94 mg/L (p < 0.01) for Pb (R2 = 0.9997), and 0.41-133.46 microg/L for Cu (p < 0.01) (R2 = 0.9999). The studies have shown that the method is a rapid, reproducible, and accurate determination of these elements in milk and dairy products and can be used in the analysis of marketed formulations in the milk and dairy industry.     

Development of an enzyme-linked immunosorbent assay for the detection of dicamba

A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) in water. The CI-ELISA has a detection limit of 2.3 microg L(-1) and a linear working range of 10--10000 microg L(-1) with an IC(50) value of 195 microg L(-1). The dicamba polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with a dicamba metabolite, 5-hydroxydicamba, and structurally related chlorobenzoic acids. The assay was used to estimate quantitatively dicamba concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, a C(18) (reversed phase) column concentration step was devised prior to analysis, and the detection limits were increased by at least by 10-fold. After the sample preconcentration, the detection limit, IC(50), and linear working range were 0.23, 19.5, and 5-200 microg L(-1), respectively. The CI-ELISA estimations in water correlated well with those from gas chromatography-mass spectrometry (GC-MS) analysis (r(2) = 0.9991). This assay contributes to reducing laboratory costs associated with the conventional GC-MS residue analysis techniques for the quantitation of dicamba in water.     

Development of a microtiter plate ELISA and a dipstick ELISA for the determination of the organophosphorus insecticide fenthion

In previous studies, polyclonal antibodies against the organophosphorus insecticide fenthion were obtained and an indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed for this pesticide. In this study, using these antibodies and an enzyme tracer, direct competitive ELISAs for fenthion in microtiter plate and dipstick formats were developed. The microtiter plate ELISA showed an IC(50) value of 1.2 microg/L with a detection limit of 0.1 microg/L. The antibodies showed negligible cross-reactivity with other organophosphorus pesticides. The use of the dipstick format using Immunodyne as a support membrane allowed the quick visual detection of fenthion in concentrations >10 microg/L. The IC(50) value of the dipstick format using reflectance detection was 15 microg/L with a detection limit of 0.5 microg/L. The recoveries of fenthion from spiked vegetable samples using the two formats without any prior enrichment or cleanup steps were 87-116%.     

Large volume cold on-column injection for gas chromatography-negative chemical ionization-mass spectrometry analysis of selected pesticides in air samples

A new gas chromatographic method is described for the analysis of fungicides captan, captafol, and folpet from organic extracts of air samples using large volume injection (LVI) via a cold on-column (COC) inlet coupled with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). Although standard split/splitless injection due to high injection port temperatures (>225 degrees C) have been shown to degrade these thermally labile fungicides, COC injection minimizes degradation. Insecticides such as chlorpyrifos and diazinon were also examined to show added selectivity. By using a solvent vapor exit with the COC inlet, injection volumes of 10-100 microL can be made to lower detection levels. GC-NCI-MS was compared to GC-electron impact ionization-mass spectrometry for each pesticide using LVI-COC injections and was found to be 2-80 times more sensitive, depending on the pesticide. Method detection limit (MDL) values with 100 microL injections were 2.5 microg L-1 for captan, folpet, and diazinon, 5.0 microg L-1 captafol, and 1.0 microg L-1 for chlorpyrifos, with the normal working range examined for sample analysis from MDL to 100 microg L-1. Detection of all pesticides except captafol, used only in the United States but not Canada, was demonstrated from air samples taken from Abbotsford, British Columbia, Canada.     

ELISA for sulfonamides and its application for screening in water contamination

Two enzyme-linked immunosorbent assays (ELISAs) were tested for their suitability for detecting sulfonamides in wastewater from various stages in wastewater treatment plants (WWTPs), the river into which the wastewater is discharged, and two swine-rearing facilities. The sulfamethoxazole ELISA cross-reacts with several compounds, achieving detection limits of <0.04 microg/L for sulfamethoxazole (SMX), sulfamethoxypyridine, sulfachloropyridine, and sulfamethoxine, whereas the sulfamethazine (SMZ) ELISA is more compound specific, with a detection limit of <0.03 microg/L. Samples from various stages of wastewater purifications gave 0.6-3.1 microg/L by SMX-ELISA, whereas river samples were approximately 10-fold lower, ranging from below detection to 0.09 microg/L. Swine wastewater samples analyzed by the SMX-ELISA were either at or near detectable limits from one facility, whereas the other facility had concentrations of approximately 0.5 microg/L, although LC-MS/MS did not confirm the presence of SMX. Sulfamethazine ELISA detected no SMZ in either WWTP or river samples. In contrast, wastewater samples from swine facilities analyzed by SMZ-ELISA were found to contain approximately 30 microg/L [piglet (50-100 lb) wastewater] and approximately 7 microg/L (market-weight hog wastewater). Sulfamethazine ELISA analyses of wastewater from another swine facility found concentrations to be near or below detection limits. A solid phase extraction method was used to isolate and concentrate sulfonamides from water samples prior to LC-MS/MS multiresidue confirmatory analysis. The recoveries at 1 microg/L fortification ranged from 42 +/- 4% for SMZ to 88 +/- 4% for SMX ( n = 6). The ELISA results in the WWTPs were confirmed by LC-MS/MS, as sulfonamide multiresidue confirmatory analysis identified SMX, sulfapyridine, and sulfasalazine to be present in the wastewater. Sulfamethazine presence at one swine-rearing facility was also confirmed by LC-MS/MS, demonstrating the usefulness of the ELISA technique as a rapid and high-throughput screening method.     

Extending the working range of immunoanalysis by exploitation of two monoclonal antibodies

A newly established rat monoclonal antibody (mAb) for isoproturon, namely, IOC 10G7, is described. This mAb shows a standard curve for isoproturon in phosphate-buffered saline with a test midpoint of 5.5 +/- 1.8 microg/L (n = 15). In combination with the formerly developed mAb IOC 7E1, IOC 10G7 can be exploited to extend the working range for the analysis of isoproturon. Both antibodies were formatted into a competitive enzyme-linked immunosorbent assay (ELISA), using the same enzyme-tracer. MAb IOC 7E1 and mAb IOC 10G7 have different affinities for the target compound, but the signal-response curves of the single antibodies overlap. Cross-reactivity (CR) patterns of both antibodies are comparable, showing the highest CR for the metabolite 1-(4-isopropylphenyl)-3-methylurea (IOC 10G7, 9%; IOC 7E1, 19%). The system described here includes the combined, but individual, usage of both assays on one microtiter plate, as well as the strategy for mixing the two antibodies for the utilization in one assay. When standards are performed in Milli-Q water, the working range for isoproturon with the individual ELISAs using mAb IOC 7E1 is from 0.01 to 1 microg/L (test midpoint = 0.11 +/- 0.03 microg/L; n = 17) and with IOC 10G7, it is 1-100 microg/L (test midpoint = 10.3 +/- 1.6 microg/L; n = 32). The working range with mixed antibodies is usually on the order of 0.03-30 microg/L (test midpoint = 0.5 +/- 0.2 microg/L; n = 17). These strategies (mAbs individually and mixed) cover a range of 4 and 3 orders of magnitude, respectively. As a demonstration, water samples of different origins and an extract of mixed sediment were analyzed. The advantages of these strategies are discussed.     

Rapid determination of fumonisin B1 in food samples by enzyme-linked immunosorbent assay and colloidal gold immunoassay

A rapid enzyme-linked immunosorbent assay (ELISA) test (microwell plate) and a membrane-based colloidal gold immunoassay in flow-through and lateral-flow formats for the rapid detection of fumonisin B1 (FB1) were developed. The rapid microwell assay can be completed within 20 min with the detection limit of 0.5 +/- 0.2 microg/L. Membrane-based colloidal gold immunoassays had a visual detection limit of 1.0 microg/L for FB1 with the detection time of <10 min. Matrix interference was eliminated by 15-fold dilutions of methanol extracts with buffer. These immunoassays can be used as quantitative or qualitative tools for the rapid detection of FB1 residues in 10-20 min on-site.     

Identification and quantification of astaxanthin esters in shrimp (Pandalus borealis) and in a microalga (Haematococcus pluvialis) by liquid chromatography-mass spectrometry using negative ion atmospheric pressure chemical ionization

Negative ion liquid chromatography-atmospheric pressure chemical ionization mass spectrometry [negative ion LC-(APCI)MS] was used for the identification of astaxanthin esters in extracts of commercial shrimp (Pandalus borealis) and dried microalga (Haematococcus pluvialis) samples. A cleanup step using a normal phase solid phase extraction (SPE) cartridge was applied prior to analysis. Recovery experiments with astaxanthin oleate as model compound proved the applicability of this step (98.5 +/- 7.6%; n = 4). The assignment of astaxanthin esters in negative ion LC-(APCI)MS was based on the detection of the molecular ion (M*-) and the formation of characteristic fragment ions, resulting from the loss of one or two fatty acids. Quantification of individual astaxanthin esters was performed using an astaxanthin calibration curve, which was found to be linear over the required range (1-51 micromol/L; r2 = 0.9996). Detection limits, based on the intensity of M*-, a signal-to-noise ratio of 3:1, and an injection volume of 20 microL, were estimated to be 0.05 microg/mL (free astaxanthin), 0.28 microg/mL (astaxanthin-C16:0), and 0.78 microg/mL (astaxanthin-C16:0/C16:0), respectively. This LC-(APCI)MS method allows for the first time the characterization of native astaxanthin esters in P. borealis and H. pluvialis without using time-consuming isolation steps with subsequent gas chromatographic analyses of fatty acid methyl esters. The results suggest that the pattern of astaxanthin-bound polyunsaturated fatty acids of P. borealis does not reflect the respective fatty acid pattern found in triacylglycerides. Application of the presented LC-(APCI)MS technique in common astaxanthin ester analysis will forestall erroneous xanthophyll ester assignment in natural sources.     

Migration of nonylphenol from plastic containers to water and a milk surrogate

Nonylphenol (NP) is used as an antioxidant and plasticizer in some plastic products. After the discovery of its endocrine-disrupting potential, concern over human exposure to this chemical has increased. Recently, a group in Germany estimated the average daily intake of NP from food (7.5 microg/day), excluding water. In the present study, NP, octylphenol (OP), and their respective ethoxylates (1-5) were measured in spring water bottled in three different types of plastic (HDPE, PET, and PVC). NP was present in water from HDPE and PVC containers, at 180 and 300 ng/L respectively, which represent 4.8% and 8% of the value calculated by the German group assuming a consumption of 2 L of water per day. OP was found in water from HDPE extracts in lower amounts, 12 ng/L, and neither the NP- nor the OP-ethoxylates were detected in any of the samples. Attempts to measure these compounds in tap water were unsuccessful, probably because reaction with residual chlorine results in the formation of chlorinated byproducts. Migration of NP from HDPE containers to a milk surrogate was also evaluated; results indicate that the amounts of NP leaching into milk might be similar to those in bottled water.     

Development of time-resolved chemiluminescence for the determination of antu in river water, wheat, barley, and oat grain samples

A novel chemiluminescence method for the determination of antu has been developed based on the reaction between potassium permanganate in acid medium with this rat-poison in the presence of formaldehyde as an emission enhancer. The main feature of the system used is that the recording of the whole chemiluminescence intensity-vs-time profiles can be obtained, using the stopped-flow technique in a continuous-flow system. This enables the use of three quantitative parameters adjustable via software settings, one of them a typically kinetic parameter, such as rate of the light-decay reaction, and the others conventional parameters, such as maximum emission intensity and total emission area, which are proportional to the analyte concentration. The optimum chemical conditions for the chemiluminescence emission were investigated. The effect of common emission enhancers, such as formic acid, formaldehyde, glutaraldehyde, acetaldehyde, quinine, fluorescein, rhodamine B, and rhodamine 6G, was studied. The parameters selected were sulfuric acid 4.0 mol L(-)(1), permanganate 0.1 mmol L(-)(1), and formaldehyde 1.0 mol L(-)(1). The calibration graphs obtained with each one of the measurement parameters were linear for the concentration range from 0.05 to 3.00 microg mL(-)(1). The detection limits ranged from 0.005 to 0.010 microg mL(-)(1), and RSD values (n = 10) of 0.99-1.79% at a 0.30 microg mL(-)(1) concentration level and 1.71-2.22% at a 1.0 microg mL(-)(1) concentration level were obtained. The present chemiluminescence procedures were applied to the determination of antu in different kinds of samples, such as river water, wheat, barley, and oat grain samples. Recovery values not significantly different from the spiked amount were found for these determinations.     

Determination of 49 organophosphorus pesticide residues and their metabolites in fish, egg, and milk by dual gas chromatography-dual pulse flame photometric detection with gel permeation chromatography cleanup

A new method for the quantitative determination of 49 kinds of organophosphorus pesticide residues and their metabolites in fish, egg, and milk by dual gas chromatography-dual pulse flame photometric detection was developed. Homogenized samples were extracted with acetone and methylene chloride (1 + 1, v/v), and then the extracts were cleaned up by gel permeation chromatography (GPC). The response of each organophosphorus pesticide showed a good linearity with its concentration; the linearity correlation was not less than 0.99. The detection limits (S/N = 3) of pesticides were in the range of 0.001-0.025 mg kg?1. The recovery experiments were performed by blank sample spiked at low, medium, and high fortification levels. The recoveries for fish, egg, and milk were 50.9-142.2, 53.3-137.2, and 50.3-139.4% with relative standard deviations (RSD, n = 6) of 2.3-24.9, 4.3-26.7, and 2.8-32.2%, respectively. The method was applied to detect organophosphorus pesticides in samples collected from the market, and satisfactory results were obtained. This quantitative method was highly sensitive and exact and could be applied to the accurate determination of organophosphorus contaminants in fish, egg, and milk.     

Simultaneous determination of ethidimuron, methabenzthiazuron, and their two major degradation products in soil

An analytical method has been developed for the quantification of two herbicides (ethidimuron and methabenzthiazuron) and their two main soil derivatives. This method involves fluidized-bed extraction (FBE) prior to cleanup and analysis by reverse-phase liquid chromatography with UV detection at 282 nm. FBE conditions were established to provide efficient extraction without degradation of the four analytes. (14)C-labeled compounds were used for the optimization of extraction and purification steps and for the determination of related efficiencies. Extraction was optimal using a fexIKA extractor operating at 110 degrees C for three cycles (total time = 95 min) with 75 g of soil and 150 mL of a 60:40 v/v acetone/water mixture. Extracts were further purified on a 500 mg silica SPE cartridge. Separation was performed on a C18 Purosphere column (250 mm x 4 mm i.d.), at 0.8 mL min(-1) and 30 degrees C with an elution gradient made up of phosphoric acid aqueous solution (pH 2.2) and acetonitrile. Calibration curves were found to be linear in the 0.5-50 mg L(-1) concentration range. Besides freshly spiked soil samples, method validation included the analysis of samples with aged residues. Recovery values, determined from spiked samples, were close to 100%. Limits of detection ranged between 2 and 3 microg kg(-1) of dry soil and limits of quantification between 8 and 10 microg kg(-1) of dry soil. An attempt to improve these performances by using fluorescence detection following postcolumn derivatization by orthophthalaldehyde-mercaptoethanol reagent was unsuccessful.     

Rapid high pressure liquid chromatographic determination of aflatoxin M1 in milk and nonfat dry milk

A modification of the current revised AOAC method, 26.A10-26.A15, is described for the rapid analysis of aflatoxin M1 in milk and nonfat dry milk. The method incorporates chloroform extraction and eliminates the need for column chromatography by using liquid-liquid partition for sample extract cleanup. Quantitation is carried out by using fluorescence detection combined with high pressure liquid chromatography (HPLC) of aflatoxin M1 which has been converted to aflatoxin M2a with trifluoroacetic acid. The method has a detection limit of 0.014 micrograms/L (2 X signal/noise) for whole milk. For 6 samples of naturally contaminated nonfat dry and freeze-dried milk, the modified method gave an average result of 0.698 micrograms/L; the AOAC method gave an average result of 0.386 micrograms/L.     

Rapid and sensitive determination of sulfonamide residues in milk and chicken muscle by microfluidic chip electrophoresis

A new, rapid, and sensitive method was proposed for the determination of sulfonamide residues in milk and chicken muscle samples by microchip electrophoresis with laser-induced fluorescence detection. Separation of fluorescamine-labeled sulfonamides was accomplished by using a buffer containing 5 mmol/L boric acid and 1% (w/v) polyvinyl alcohol (PVA). The pH, amount of PVA, and concentration of boric acid in the running buffer were found to have great influence on the separation. By optimizing these conditions, the separation of four sulfonamides, sulfamethazine, sulfamethoxazole, sulfaquinoxaline, and sulfanilamide, was achieved within 1 min with limits of detection (S/N = 3) of 0.2-2.3 μg/L, which are well below the maximum residue limit. The proposed method also exhibited very good repeatability; the relative standard deviations for both within-day and between-day measurements were ≤3.0%. With a simplified sample pretreatment protocol, fast determination of sulfonamides in real samples was successfully performed with standard addition recoveries of 93.3-100.8 and 82.9-92.3%, respectively.     

Liquid chromatography-electrospray ionization-mass spectrometry method in multiple reaction monitoring mode to determine 17alpha-ethynylestradiol residues in cattle hair without previous digestion

A liquid chromatography-mass spectrometric (LC-MS/MS) method has been developed for determination of ethynylestradiol residues in cattle hair. Hair samples were pulverized with a cryogenic mill followed by a simple extraction with acetonitrile. A dansyl derivatization procedure to improve ethynylestradiol detection was used before the LC-MS/MS analysis in multiple reaction monitoring (MRM) mode using alpha-estradiol as an internal standard. The method was validated following the latest EU guidelines using blank hair samples spiked at 2 ng g(-1). The detection capability (CCbeta) was less than 2 ng g(-1), and the decision limit (CCalpha) was 1 ng g(-1). Incurred samples obtained 56 days after cow treatment with ethynylestradiol were analyzed, and the presence of ethynylestradiol in the hair was confirmed in all cases.     

Determination of postharvest fungicides in fruit juices by solid-phase extraction followed by liquid chromatography electrospray time-of-flight mass spectrometry

A multiresidue method using liquid chromatography-time-of-flight mass spectrometry (LC-TOFMS) has been developed for the quantitative analysis of five widely used postharvest fungicides (carbendazim, thiabendazole, imazalil, prochloraz, and iprodione) and two of their transformation products (imazalil and prochloraz metabolites) in fruit juices. LC-TOFMS in positive electrospray ionization mode was used to quantify and confirm trace levels of these fungicides in fruit juices. The proposed method consists of a sample treatment step based on solid-phase extraction using hydrophilic-lipophilic-balanced polymer-based reverse-phase SPE cartridges (Oasis HLB) and methanol as an eluting solvent. Fruit-juice extracts spiked at different fortification levels (10 and 20 microg L(-1)) yielded average recoveries in the range of 71-109% with RSD (%) below 15%. Subsequent identification, confirmation, and quantitation were carried out by LC-TOFMS analysis. The confirmation of the target species was based on accurate mass measurements of protonated molecules ([M+H]+) and fragment ions, obtaining routine accuracy errors lower than 2 ppm in most cases. The obtained limits of detection (LODs) of the proposed method were in the range of 0.08-0.45 microg L(-1). Finally, the proposed method was successfully applied to the analysis of 23 fruit juice samples collected from different European countries and the United States, showing the potential applicability of the method in routine analysis. Over 50% of the samples tested contained pesticide residues, but relatively low concentration levels were found.     

Reaction of tryptophan with carbohydrates: identification and quantitative determination of novel beta-carboline alkaloids in food

The formation of various carbohydrate-derived beta-carbolines was observed when model reactions of tryptophan with glucose were studied by means of HPLC with diode array detection, as well as by means of HPLC-MS. Isolation of these compounds and subsequent characterization by tandem mass spectrometry and NMR spectroscopy led to the identification of diastereomeric 1-(1,3,4,5-tetrahydroxypent-1-yl)-9H-pyrido[3,4-b]indoles (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-9H-pyrido[3,4-b]indoles (2a/b), and E/Z isomers of 1-(1,5-dihydroxypent-3-en-1-yl)-9H-pyrido[3,4-b]indole (3a/b). HPLC-MS was used to prove the presence of these novel beta-carboline alkaloids in various food samples. In addition, quantitative determination of beta-carbolines 1a, 1b, and 2a/b in numerous products was achieved by means of HPLC with fluorometric detection. Concentrations ranged from 12 to 1922 microg/L for 1a and 1b and from 3 to 644 microg/L for 2a/b. The highest concentrations of all carbohydrate-derived beta-carbolines under study were found in ketchup, soy sauce, and fish sauce.