All-in-one 2LabsToGo system for analysis of ergot alkaloids in whole rye

Ergot alkaloids, naturally occurring mycotoxins of Claviceps fungi, pose health risks. This necessitates accurate analysis methods to ensure food safety. This study explored the open-source miniaturized all-in-one 2LabsToGo system to analyze ergot alkaloids in whole rye samples. It is suited for sustainable atline analysis as it combines all planar chromatography tasks, allowing low-cost quality control in milling plants. The LOD and LOQ of ergocristine were determined to be 0.4 and 1.2 ng/zone, respectively. Detectability of ergot alkaloids was proven to be below the current maximum limit of 500 µg/kg for rye milling products. The repeatability (%RSD) was 4.1 % and the coefficient of determination of the analytical response (R2) was 0.9918 for ergocristine. The mean recovery rate of ergot alkaloids in spiked whole rye grain was close to 100 %. Results of screening whole rye for ergot alkaloids were successfully verified by comparison with those obtained by conventional status quo HPTLC instrumentation.

Miniaturized open-source 2LabsToGo screening of lactose-free dairy products and saccharide-containing foods

The open-source 2LabsToGo system is the only one in its nature. It combines in one miniaturized instrument all relevant steps normally performed in a chemical and biological laboratory. For the first time, the applicability of the 2LabsToGo system was studied for screening 17 food products. As examples, saccharides were analyzed in eight products of different matrix complexity, and the absence of lactose was studied in nine lactose-free dairy products. Derivatization including homogeneous reagent application and plate heating via the 2LabsToGo system was explored for saccharide detection, and its performance was investigated. The visual detection sensitivity of lactose was comparable to previous studies. The precision of lactose in milk matrix (%RSD 4.6%) as well as the coefficient of determination of the calibration function (0.9995) were highly satisfying. The obtained lactose content of milk (4.5%) was plausible. Screening eight saccharide-containing food samples showed the saccharides in agreement with the expectations for the respective food product. The lactose content of nine different lactose-free dairy products was proven to be below the 0.1% lactose limit value. As proof-of-principle and for verification, these screening results obtained with the miniaturized 2LabsToGo system were reproduced using conventional state-of-the-art instrumentation, which led to the same results. However, instrumental costs were comparably low for the 2LabsToGo system. The application of the new 2LabsToGo system was successfully shown for saccharide screening, which is attractive to the field of quality control or official food control.

2LabsToGo─Recipe for Building Your Own Chromatography Equipment Including Biological Assay and Effect Detection

A complete recipe for building your own chromatography equipment from readily available materials is introduced. It combines sample separation (chemistry laboratory) with biological effect detection (biology laboratory). This hyphenation of two disciplines is necessary for prioritizing important compounds in complex samples. Among the thousands of compounds therein, it is often not clear which compounds are the important ones. On the same separation surface, additional detection of biological effects enables and guides substance prioritization. The newly developed open-source 2LabsToGo system for chemical and biological analysis is completely solvent-resistant and, due to miniaturization, environmentally friendly regarding the consumption of materials. It produces comparable results but is 10 times more compact (26 cm × 31 cm × 34 cm), 10 times lighter (6.8 kg), and 55 times less expensive (€ 1717) than current sophisticated commercial devices. As a proof of concept of the first 2LabsToGo system, the quality of different water samples was analyzed since clean water is becoming increasingly rare. In water, most of the thousands of substance signals or features can neither be identified nor classified toxicologically. However, methods that exploit this hyphenated strategy provide answers to such essential safety issues. Drinking or tap water did not show bioactive or toxic compounds, which was expected, whereas biogas or landfill water samples did. The hyphenated 2LabsToGo strategy is affordable and extremely useful for all laboratories with limited equipment but pressing challenges. It is ready to be used in various analytical tasks and applications.

On-surface autosampling for liquid chromatography-mass spectrometry

An on-surface multi-purpose autosampler was built for liquid chromatography-mass spectrometry (LC-MS) based on the autoTLC-MS interface, taking advantage of open-source hard- and software developments as well as 3D printing. Termed autoTLC-LC-MS system, it is introduced for orthogonal hyphenation of normal phase high-performance thin-layer chromatography with reversed phase high-performance LC (HPLC) and high-resolution MS (HRMS). For verification of its functionality, a multi-class antibiotic mixture was applied as a calibration band pattern on an adsorbent layer and detected by the Bacillus subtilis bioassay. This effect-image was uploaded as a template in the updated TLC-MS_manager software. The clicked-on antibiotic zones were sequentially eluted without intervention from the planar counterpart (without bioassay) via a monolithic HPLC column into the HRMS system. For elution of antibiotics of 7 structural classes at 5 different calibration levels, the new on-surface autosampler achieved intra-day precisions of 2.1-14.1%, while inter-day precisions ranged 2.5-16.1% (all n = 3). The new hyphenation offers potential for planar sample clean-up prior to HPLC, concentration of liquid samples, increase of peak capacity and proof of peak purity or isomers. The integrated autoTLC-LC-MS system enabled high sample throughput, efficiency and reproducibility for the first time through fully automated TLC-LC-MS sequence operation. Its contact-closure signal functionality, versatile 3D printed planar sample holder and open-source software made it readily adjustable for new analytical tasks. Undoubtedly, any planar material can be investigated for leachables, such as textiles, foils, papers and other packagings, as well as planar biological samples for ingredients.

Open-source all-in-one LabToGo Office Chromatography

Print and media technologies were used uncommonly in the field of chromatography and explored in application to create a miniaturized all-in-one LabToGo system. This novel research field termed Office Chromatography (OC) uses additive manufacturing in terms of 3D printing of operational parts as well as open-source hard- and software. The OCLab2 presented here has been considerably extended in its functionalities. For inkjet printing of solutions, a newly designed printhead was manufactured controlled by a self-constructed ink-jet board, allowing to check the nozzles' resistance heating circuit. Plate heating was newly integrated, especially favorable for the demonstrated application of higher volumes of aqueous samples. The UV/Vis/FLD plate images were captured by a Raspberry Pi V2 camera module under illumination by novel light emitting diodes (LEDs) for highly selective RGBW color (Vis), UVC 278-nm (UV) and UVA 366-nm (FLD) detection, installed in a newly created miniature cabinet to protect from extraneous light. The spectral separation of differently colored food dyes was achieved by the fully addressable driver controlled RGBW LEDs. The software was newly written in R to speed-up the processes, supported by the new Raspberry Pi 4B computer with 4 GB RAM. The analysis of Stevia leaves for steviol glycosides yielded results comparable to the status quo. Different water samples were analyzed for bioactive compounds. Thereby, compounds of general cytotoxicity were effect-directed detected by bioluminescent A. fischeri bacteria. It allowed the bioanalytical screening for potential risks in tap water, surface waters, rain water, landfill leachates and biogas slurries.

Determination of mono- and diacylglycerols from E 471 food emulsifiers in aerosol whipping cream by high-performance thin-layer chromatography-fluorescence detection

Mono- and diacylglycerol (MAG and DAG) emulsifiers (E 471) are widely applied to regulate techno-functional properties in different food categories, for example, in dairy products. A method for the determination of MAG and DAG in aerosol whipping cream by high-performance thin-layer chromatography with fluorescence detection (HPTLC-FLD) after derivatization with primuline was developed. For sample preparation, aerosol whipping cream was mixed with ethanol, followed by the addition of water and liquid-liquid extraction with tert-butyl methyl ether. The sample extracts were analyzed by HPTLC-FLD on silica gel LiChrospher plates with n-pentane/n-hexane/diethyl ether (22.5:22.5:55, v/v/v) as mobile phase, when interfering matrix like cholesterol and triacylglycerols were successfully separated from the E 471 food additives. For quantitation, an emulsifier with known composition was used as calibration standard and the fluorescent MAG and DAG were scanned at 366/> 400 nm. Limits of detection and quantitation of 4 and 11 mg/100 g aerosol whipping cream were obtained for both monostearin and 1,2-distearin, respectively, and allowed the reliable quantitation of MAG and DAG from E 471 far below commonly applied emulsifier amounts. Recoveries from model aerosol whipping cream with 400 mg E 471/100 g were determined in a calibration range of 200-600 mg E 471/100 g sample and ranged between 86 and 105% with relative standard deviations below 7%. In aerosol whipping creams from the German market, E 471 amounts ranged between 384 and 610 mg/100 g.

Second-Derivative UV Spectrometric Microdetermination of Dithiocarbamate Residues as Methyl Xanthate

The microdetermination of dithiocarbamate fungicide residues as methyl xanthate using second-derivative UV spectrometry is described. The residue analysis is based on a hot-acid decomposition, scrubbing the evolved CS2 with lead acetate and concentrated H2SO4, and absorbing the CS2 in methanolic KOH. The absorbance of the xanthate system (conventional method) and the height of the negative peak at 302 nm (second-derivative method) are used to quantitate the CS2. The molar absorptivity of the xanthate system within the range of 0.3–2.4 μg CS2/mL where Beer’s law is obeyed, was 1.70 × 104 L mol-1 cm-1. The derivative procedure was more selective and sensitive to CS2 than the classical method. The calibration graph of the derivative procedure was rectilinear from 0.1–1.1 μg/mL of CS2. The coefficient of variation for the determination (n = 10) of a 0.28 (μg/mL standard of CS2 was 2.6%. The detection limit for CS2 was 0.08 μg/mL. The second-derivative procedure was applied to the residue analysis of thiram on tomatoes.

Determination of Dialkyl Phosphates as Breakdown Products of Organophosphorus Insecticides in Fruit Juices by HPTLC with Fluorescence Detection

Dialkyl phosphates (DAP) are common degradation products of organophosphorus pesticides that are used as urinary biomarkers for human exposure. An HPTLC method was developed for the quantitative determination of DAP in fruit juices, i.e., dimethyl phosphate (DMP), dimethyl thiophosphate (DMTP), diethyl phosphate (DEP), and diethyl thiophosphate (DETP). Dibutyl phosphate (DBP) was used as an internal standard. The method was based on precipitation of fruit acids in the presence of barium chloride and acetonitrile and liquidliquid extraction with acetonitrilediethyl ether. Extracted DAP were derivatized with 1-(bromoacetyl)pyrene (BAP), and the BAP derivatives separated on HPTLC amino plates with dichloromethane as the mobile phase. Densitometry was performed by measurement of fluorescence at 366/>400 nm. The limit of quantification (LOQ) values were between 0.8 and 1.4 ng/zone. Fluorescence enhancement was achieved by dipping the plate into a paraffin oil solution, increasing the sensitivity and resulting in an LOQ of 0.50.6 ng/zone. Repeatabilities with relative standard deviations of 3.5 (n = 5, at 1520 ng/zone) and coefficients of correlation of 0.9999 were highly satisfactory for rapid trace analysis of DAP in the fruit juices by HPTLC. The mean recoveries from apple juice spiked at 0.5 mg/L were 74, 83, 70, and 57 for DMP, DEP, DMTP, and DETP, respectively. If an application volume of 5 L of apple juice extract was applied, the LOQ in apple juice was 300 g/L. However, this can be lowered by application of higher volumes (up to 50 L) or a more concentrated derivatization batch.

Nontargeted Multicomponent Analytical Screening of Plastic Food Contact Materials Using Fast Interpretation of Deliverables via Expert Structure-Activity Relationship Software

Plastic packaging materials may release compounds into packed foodstuffs. To identify potential migrants of toxicological concern, resins, and multilayer foils (mainly polyethylene) intended for the production of food contact materials were extracted and analyzed by GC/mass spectrometry. To identify even compounds of low concentrations, AMDIS software was used and data evaluation was safeguarded by the Kovats retention index (RI) system. In this way, 46 compounds were identified as possible migrants. The expert structure-activity relationship software DEREK for Windows was utilized to evaluate all identified substances in terms of carcinogenicity, genotoxicity, thyroid toxicity, and miscellaneous endpoints for humans. Additionally, a literature search for these compounds was performed with Sci-Finder<sup/>, but relevant data were missing for 28 substances. Seven compounds with adverse toxicological effects were identified. In addition, the RIs of 24 commercial additive standards, measured with a GC capillary column of intermediate polarity, are given.

Second-Derivative Spectrometric Determination of Urea in Milk Using the Diacetyl Monoxime Reagent

The application of derivative spectrometry to resolve overlapping spectra and improve the sensitivity and selectivity of the colorimetric determination of urea in milk using diacetyl monoxime is presented. With first-derivative (1D) spectrometry, the max of the colored complex was established to be 525 nm. The absorption band at max 525 nm in normal absorption (0D) spectrometry was resolved into three clearly distinct spectral bands with minima at 497, 530, and 566 nm with second-derivative (2D) spectrometry. With the second-derivative (2D530) technique, the depth of the trough of the strongest signal at 530 nm was used to determine urea in milk samples. Linear calibration curves for urea were obtained over a concentration range of 0.21.4 mg/L, with correlation coefficients greater than 0.999. The LOD and LOQ of the method were 0.01 and 0.03 mg/L, respectively. Recoveries of 99100 of spiked urea in milk with RSD values below 2.0 were obtained. The second-derivative method is simple, affordable, sensitive, and selective for the determination of urea in milk.

Selective Trace Determination of Dithiocarbamate Fungicides in Fruits and Vegetables by Reversed-Phase Ion-Pair Liquid Chromatography with Ultraviolet and Electrochemical Detection

The predominant methods for determination of dithiocarbamate fungicides (DTC) have been based on quantitation of carbon disulfide released by hot acid digestion. Because the subgroups of the DTC family differ in their chemical properties and toxicological behavior, selective determination is required. To meet the demand for a fast, simple, and sensitive procedure, a new reversed-phase ion-pair chromatographic method was developed, consisting of surface extraction followed by direct injection into a liquid chromatographic system equipped with ultraviolet and electrochemical detectors, connected in series. The procedure is applicable to residues of N-methyldithiocarbamates (metam-sodium), N,N-dimethyldithiocarbamates (e.g., ziram and ferbam), ethylenebisdithiocarbamates (e.g., nabam, maneb, zineb, and mancozeb), and propylenebisdithiocarbamates (e.g., propineb) in fruits and vegetables. Limits of quantitation, calculated according to the procedure of the Deutsche Forschungsgemeinschaft, are 9, 12, 8, and 12 μg CS2/L for N-methyl-DTC, N,N-dimethyl-DTC, ethylenebis-DTC, and propylenebis-DTC, respectively, when electrochemical detection is used.

Characterization of E 471 food emulsifiers by high-performance thin-layer chromatography-fluorescence detection

Mono- and diacylglycerol (MAG and DAG) emulsifiers, also known as food additive E 471, are widely used to adjust techno-functional properties in various foods. Besides MAGs and DAGs, E 471 emulsifiers additionally comprise different amounts of triacylglycerols (TAGs) and free fatty acids (FFAs). MAGs, DAGs, TAGs and FFAs are generally determined by high-performance liquid chromatography (HPLC) or gas chromatography (GC) coupled to mass selective detection, analyzing the individual representatives of the lipid classes. In this work we present a rapid and sensitive method for the determination of MAGs, DAGs, TAGs and FFAs in E 471 emulsifiers by high-performance thin-layer chromatography with fluorescence detection (HPTLC-FLD), including a response factor system for quantitation. Samples were simply dissolved and diluted with t-butyl methyl ether before a two-fold development was performed on primuline pre-impregnated LiChrospher silica gel plates with diethyl ether and n-pentane/n-hexane/diethyl ether (52:20:28, v/v/v) as the mobile phases to 18 and 75 mm, respectively. For quantitation, the plate was scanned in the fluorescence mode at UV 366/>400 nm, when the cumulative signal for each lipid class was used. Calibration was done with 1,2-distearin and amounts of lipid classes were calculated with response factors and expressed as monostearin, distearin, tristearin and stearic acid. Limits of detection and quantitation were 1 and 4 ng/zone, respectively, for 1,2-distearin. Thus, the HPTLC-FLD approach represents a simple, rapid and convenient screening alternative to HPLC and GC analysis of the individual compounds. Visual detection additionally enables an easy characterization and the direct comparison of emulsifiers through the lipid class pattern, when utilized as a fingerprint.

Determination of caffeine, theobromine and theophylline in Mate beer and Mate soft drinks by high-performance thin-layer chromatography

Mate beer and Mate soft drinks are beverages produced from the dried leaves of Ilex paraguariensis (Yerba Mate). In Yerba Mate, the xanthine derivatives caffeine, theobromine and theophylline, also known as methylxanthines, are important active components. The presented method for the determination of caffeine, theobromine and theophylline in Mate beer and Mate soft drinks by high-performance thin-layer chromatography with ultraviolet detection (HPTLC-UV) offers a fully automated and sensitive determination of the three methylxanthines. Filtration of the samples was followed by degassing, dilution with acetonitrile in the case of Mate beers for protein precipitation, and centrifugation before the extracts were analyzed by HPTLC-UV on LiChrospher silica gel plates with fluorescence indicator and acetone/toluene/chloroform (4:3:3, v/v/v) as the mobile phase. For quantitation, the absorbance was scanned at 274nm. Limits of detection and quantitation were 1 and 4ng/zone, respectively, for caffeine, theobromine and theophylline. With recoveries close to 100% and low standard deviations reliable results were guaranteed. Experimental Mate beers as well as Mate beers and Mate soft drinks from the market were analyzed for their concentrations of methylxanthines.

Selective two-dimensional effect-directed analysis with thin-layer chromatography

There are thousands of organic trace substances in the environment that are not fully characterized, and evaluation of their relevance to the ecosystem is difficult. Effect-directed analysis (EDA) is a suitable tool to assess the effects of a substance via in-vitro bioassays, which can provide information about the relevance of the substance. High-performance thin-layer chromatography (HPTLC) has been shown to be a good method for fractionation. Environmental samples, however, often have high complexity, which is why the peak capacity of HPTLC is not sufficient. Therefore, this study focused on the development of selective two-dimensional (2D) HPTLC-EDA to increase the peak capacity and facilitate the identification of effective compounds. Thus, only effective zones were selected in the first dimension in terms of heart-cutting and were transferred to the second dimension through elution head-based extraction. Three 2D approaches were developed and validated. The best results in terms of peak capacity and orthogonality were achieved when the retardation factors of the first dimension were used to adjust the mobile phase (MP) for the second dimension. Applying the acetylcholinesterase (AChE) inhibition assay as an example EDA, analysis of spiked surface water by 2D HPTLC-EDA allowed zones with neurotoxic effects to responsible substances to be assigned. The 2D separation reduced the complexity of effective zones and thus facilitated the subsequent identification of effective compounds. Knowledge about a substancés effects enabled assessment of its relevance to the environment.

Logit-log evaluation of planar yeast estrogen screens

Receptor assays like the yeast estrogen screen (YES) performed in microtiter plates normally provide dose-response curves with a sigmoidal shape in semi-log plots. Such sigmoidal plots can be linearized by the logit function resulting in logit-log plots, as mainly known for the evaluation of enzyme-linked immunosorbent assays and radioimmunoassays. Since the planar yeast estrogen screen (pYES) represents the transfer of the receptor assay YES to high-performance thin-layer chromatography (HPTLC), it was assumed to obtain sigmoidal shaped dose-response curves from the measured signals, which subsequently could be used to generate logit-log plots. However, it was observed that typical sigmoidal curves were not obtained, when peak areas were plotted against the applied amount on a logarithmic scale (log amount). Therefore, peak heights were examined in the present study, which revealed proper dose-response curves when plotted against the log amount. The presence of sigmoidal dose-response curves from HPTLC-pYES made it possible to transform the signals into logits and, therefore, to create logit-log plots with linear correlations. The logit-log plots for the estrogen active compounds (EAC) 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) provided a working range up to 500pg/zone. Applying logit-log plots, mean recovery rates for E2 and EE2 from spiked water samples (2-20ng/L) were determined to 90% and 108%, respectively, with ≤24% RSD. Moreover, the linear graphs allowed an easy determination of the half maximal effect dose (ED₅₀) of EAC, since the intersection of the graph with the abscissa represents the ED₅₀. Additionally, with the knowledge of the ED₅₀ values, the estrogenic potential of EAC in terms of estradiol equivalent factors (EEF) could be determined, resulting in 0.64 for EE2.

Planar yeast estrogen screen with resorufin-β-d-galactopyranoside as substrate

For the planar yeast estrogen screen (pYES), 4-methylumbelliferyl-β-d-galactopyranoside was generally employed as substrate, delivering blue fluorescing 4-methylumbelliferone after enzymatic cleavage by the YES reporter β-d-galactosidase as the positive signal for the presence of estrogen active compounds (EAC). As environmental samples like waste water also contain blue fluorescent components, it is difficult to differentiate them from pYES signals. Therefore, resorufin-β-d-galactopyranoside (RGP), providing the orange fluorescing resorufin after enzymatic cleavage, was introduced as pYES substrate to determine EAC. With 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), mean limits of detection and quantitation of 3.5 and 6.5pg/zone, respectively, were determined. Obtained recoveries for both E2 and EE2 from spiked water samples in a concentration range of 2-20ng/L were close to 100%. The application of the RGP-pYES on waste water influent and effluent samples showed the clear detection of EAC without interferences. Estrone (E1), Estriol, E2, and an unknown EAC were found in the influent sample (E2 with a mean of 16.9 ng/L and a precision of 11% RSD; n=4), while another unknown EAC was observed in the effluent sample. In addition, the presence of conjugated EAC in the influent was demonstrated by hydrolysis with β-glucuronidase, when the signals of E1 and the unknown increased by about 25% and 100%, respectively.

High-performance thin-layer chromatography (HPTLC) for the simultaneous quantification of the cyclic lipopeptides Surfactin, Iturin A and Fengycin in culture samples of Bacillus species

A high-performance thin-layer chromatography method has been established for the identification and simultaneous quantification of the cyclic lipopeptides Surfactin, Iturin A and Fengycin in Bacillus culture samples. B. subtilis DSM 10^T, B. amyloliquefaciens DSM 7^T and B. methylotrophicus DSM 23117 were used as model strains. Culture samples indicated that a sample pretreatment is necessary in order to run HPTLC analyses. A threefold extraction of the cell-free broth with the solvent chloroform/methanol (2:1, v/v) gave best results, when all three lipopeptides were included in the analysis. For the mobile phase, a two-step development was considered most suitable. The first development is conducted with chloroform/methanol/water (65:25:4, v/v/v) over a migration distance of 60mm and the second development using butanol/ethanol/0.1% acetic acid (1:4:1, v/v/v) over a migration distance of 60mm, as well. The method was validated according to Validation of Analytical Procedures: Methodology (FDA Guidance) with respect to the parameters linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy and recovery rate. A linear range with R²>0.99 was obtained for all samples from 30ng/zone up to 600ng/zone. The results indicated that quantification of Surfactin has to be performed after the first development (hR_F=44), while Fengycin is quantified after the second development (hR_F=36, hR_F range=20-40). For Iturin A, the results demonstrated that quantification is in favor after the first (hR_F=19) development, but also possible after the second (hR_F=59) development. LOD and LOQ for Surfactin and Iturin A after the first development, and Fengycin after the second development were determined to be 16ng/zone and 47ng/zone, 13ng/zone and 39ng/zone, and 27ng/zone and 82ng/zone, respectively. Results further revealed the highly accurate and precise character of the developed method with a good inter- and intraday reproducibility. For the precision and accuracy, expressed as % recovery and relative standard deviation, respectively, the determined values did not exceed ±15% as specified by the FDA Guidance. The recovery assay conducted for samples obtained from two strains with the solvent chloroform/methanol (2:1, v/v), which was determined to be most suitable if all three lipopeptides are of interest, gave recoveries of 96.5% and 99.6%, 68.6% and 71.6%, and 102.5% and 95.2% for Surfactin, Iturin A and Fengycin, respectively. Overall, a suitable and reliable method for the simultaneous quantification of the lipopeptides Surfactin, Iturin A and Fengycin in biological samples using HPTLC was successfully developed and validated.

How Do Modern Pesticide Treatments Influence the Mobility of Old Incurred DDT Contaminations in Agricultural Soils?

Even more than 50 years after the ban of DDT in Germany, farmers are still affected by its persistence in contaminated soils. Depending on the crop cultivated on such soils, this often leads to low-level residues of DDT and its metabolites DDE and DDD ("DDX"), which are perceived as a risk by the food value chain. Pesticide formulations used in modern agriculture commonly contain high levels of surfactants, but so far no open-field studies have evaluated the effects of these treatments on the mobility of lipophilic contaminants, such as DDX. In this field trial, a 1.03 ha section was cultivated with Cucurbita maxima under realistic conditions to monitor the mobility of DDX in low-level contaminated agricultural soils in dependence of common pesticide applications. A typical organic treatment was compared to a conventional protocol. Soil samples were taken before and after each application. Samples from the organic section featured significantly higher extractable DDX contents in soil and water compared to the conventional section. The results show that modern pesticide treatments can have an unforeseen, yet significant influence on the mobilization and, subsequently, on the plant bioavailability of incurred DDX residues depending on the formulation composition.

Extracellular aromatic biosurfactant produced by Tsukamurella pseudospumae and T. spumae during growth on n-hexadecane

Biosurfactants are surface-active agents produced by microorganisms and show increasing significance in various industrial applications. A great variety of these secondary metabolites are described to occur within actinomycetes, amongst trehalose lipids and oligosaccharide lipids produced by the family Tsukamurellaceae. This study reports on the production of not yet described compounds with surface active behavior by non-pathogenic Tsukamurella pseudospumae and Tsukamurella spumae during growth on hydrophobic carbon sources. Extracts of the purified compounds differ in terms of structure and performance properties to other biosurfactants described within their family. Infrared and nuclear magnetic resonance spectroscopic analysis revealed the presence of aromatic moieties within the surfactant produced, which to date is only known to occur within phenolic glycolipids of some mycobateria.

Reactivity of cosmetic UV filters towards skin proteins: model studies with Boc-lysine, Boc-Gly-Phe-Gly-Lys-OH, BSA and gelatin

OBJECTIVE

Organic UV filters are used as active ingredients in most sunscreens and also in a variety of daily care products. Their good (photo) stability is of special interest to guarantee protective function and to prevent interactions with the human skin. Due to the mostly electrophilic character of the UV filters, reactions with nucleophilic protein moieties like lysine side chains are conceivable. Prior studies showed that the UV filters octocrylene (OCR), butyl methoxydibenzoylmethane (BM-DBM), ethylhexyl salicylate (EHS), ethylhexyl methoxycinnamate (EHMC), benzophenone-3 (BP-3), ethylhexyl triazone (EHT) and dibenzoylmethane (DBM) were able to covalently bind to an HPTLC amino phase and the amino acid models ethanolamine and butylamine after slightly heating and/or radiation.

METHODS

Boc-protected lysine, the tetrapeptide Boc-Gly-Phe-Gly-Lys-OH, bovine serum albumin (BSA) and porcine gelatin were used as more complex models to determine the reactivity of the mentioned UV filters towards skin proteins under thermal or UV irradiation conditions.

RESULTS

After gentle heating at 37°C, benzophenone imines were identified as reaction products of BP-3 and OCR with Boc-lysine and the tetrapeptide, whereas DBM and BM-DBM yielded enamines. For EHMC, a Michael-type reaction occurred, which resulted in addition of Boc-lysine or the tetrapeptide to the conjugated double bond. Ester aminolysis of EHS and EHT mainly afforded the corresponding amides. Reactions of the UV filters with BSA changed the UV spectrum of BSA, generally associated with an increase of the absorption strength in the UVA or UVB range. For all protein models, the UV filters showed an increasing reactivity in the order EHT < EHMC < EHS < BP-3 < OCR < DBM < BM-DBM.

CONCLUSION

Especially the UV absorbers BM-DBM, OCR and BP-3, which are seen as common allergens or photoallergens, showed a high reactivity towards the different skin protein models. As the formation of protein adducts is recognized as important key element in the induction of skin sensitization, the results of this study can contribute to a better understanding of the underlying chemical mechanisms of such reactions.

Rolling--a new application technique for luminescent bacteria on high-performance thin-layer chromatography plates

High-performance thin-layer chromatography (HPTLC) coupled with bioluminescence detection using Vibrio fischeri bacteria can be used for screening for unknown substances. This is accomplished by dipping the HPTLC plate in an aqueous bacteria solution. Especially polar substances, however, can start to dissolve during this process, which leads to blurring and tailing of the zones on the plate. To overcome this disadvantage, we applied the bacteria solution by rolling. This method has been described for chemical derivatizations, but is very rarely used. The rolling device was made of commercially available household articles. Using octhilinone and methylparaben as test compounds, rolling was compared with dipping. Despite of performing the rolling process manually, the results were reproducible. Depending on the substance and its amount on the HPTLC plate, peaks were narrower, up to a factor of 4 higher and with a higher signal-to-noise ratio than after dipping.