Determination of jasmonic acid in bark extracts from <Emphasis Type="Italic">Hevea brasiliensis</Emphasis> by capillary electrophoresis with laser-induced fluorescence detection

A simple and sensitive method is described for determination of jasmonic acid (JA) in plant tissues. The method is based on derivatization of JA with 5-bromomethylfluorescein (5-BMF) and separation and quantification of the resulting 5-BMF–JA derivative by capillary electrophoresis coupled to laser-induced fluorescence detection (CE–LIF). The derivatization conditions were studied in detail. Our results indicated that 5-BMF-labeled JA could be well separated from other plant hormones present in the sample by use of 20 mmol L^–1 borate buffer (pH 8.5). The response to JA was a linear function of concentration in the range 1 to 100 mol L^–1, with a correlation of 0.9986. Our preliminary work showed that the proposed method had fairly good selectivity and sensitivity. Only small amounts of plant sample are needed to complete the analysis. This described method enables the analysis of JA in crude extracts without extra purification and enrichment procedures.     

Determination of jasmonic acid in <Emphasis Type="Italic">Lemna minor</Emphasis> (L.) by liquid chromatography with fluorescence detection

A new method is described for the determination of endogenous jasmonic acid (JA) in Lemna minor plant extracts using liquid chromatography (LC) with fluorescence detection. Plant tissues were extracted and derivatised using 9-anthryldiazomethane (ADAM reagent) prepared in situ. Accuracy and precision were improved by using the internal standard dihydrojasmonic acid (dh-JA) for the correction of JA losses during sample preparation steps. Liquid chromatography–mass spectrometry (LC/MS) analysis of ADAM derivatives of JA and dh-JA confirmed that a single molecule of JA and dh-JA was coupled with one molecule of reagent. Derivatives of JA and dh-JA were separated with gradient elution on a C₁₈ reversed-phase column using acetonitrile/water as a mobile phase and detected by a fluorescence detector at excitation and emission wavelengths of 254 and 412 nm, respectively. The detection limits of JA and dh-JA were 2.9 ng mL⁻¹ and 3.7 ng mL⁻¹ per 50-μL injection. The method is reproducible and selective and yields single peaks for each compound regardless of isomer. The specificity and accuracy of the proposed LC/FD method was confirmed by liquid chromatography–TurboIon Spray tandem mass spectrometric (LC/MS/MS) analysis of free JA in Lemna minor samples under multiple reaction monitoring conditions.     

Rapid method for determination of protein content in cereals and oilseeds: validation, measurement uncertainty and comparison with the Kjeldahl method

The objective of this research was to test suitability of the Dumas combustion method to completely substitute the Kjeldahl method in routine laboratory determination of crude protein content in cereals and oilseeds. The validation of the method demonstrated that it is able to determine crude protein content in cereals and oilseeds in an efficient and accurate manner, with a detection limit w(N) = 0.006%, quantification limit w(N) = 0.019%, repeatability precision RSD _r = 0.41%, intra-laboratory reproducibility precision RSD _R = 0.74%, trueness, expressed in terms of bias b = 0.43%, and linear response between (2.36–19.2) mg N. Measurement uncertainty, expressed as relative expanded uncertainty (coverage factor k = 2, confidence level 95%), was calculated from validation data (U _rel = 2.24%). In order to examine the relationship between two methods, 15 cereal grain and oilseed samples were analyzed using Dumas and Kjeldahl procedure. The Kjeldahl procedure gave slightly lower w(N) values than the Dumas procedure: w _K(N) = 0.9905 w _D(N) = 0.0376 (R ²  = 0.9996). Relative standard deviations and results of homogeneity test obtained during analysis of complex cereal products (cereal breakfast and muesli bars) show that the Dumas combustion method may be less suitable for analysis of such samples compared to Kjeldahl method.     

A combined method of neutron activation analysis and radiometric measurements for <Superscript>234</Superscript>U and <Superscript>238</Superscript>U determination in soil samples of low uranium concentration

A method that combines the use of non-destructive neutron activation analysis and high-resolution α spectrometry has been developed for determination of the activities of ²³⁴U and ²³⁸U in geological samples of low uranium content. The ²³⁸U content is determined by k₀-based neutron activation analysis, whereas the ²³⁴U/²³⁸U relationship is measured by α spectrometry after isolation and electrodeposition of the uranium extracted from a lixiviation with 6 M HCl. The main advantage of the method is the simplicity of the chemical operations, including the fact that the steps destined to assure similar chemical state for the tracer and the uranium species present in the sample are not necessary. The method was applied to soil samples from sites of the North Peru Coast. Uranium concentration range 3–40 mg/kg and the isotopic composition correspond to natural uranium, with about 10% uncertainty.     

微波消解火焰原子吸收法测定火龙果中铁的不确定度评定

对微波消解火焰原子吸收法测定火龙果中铁含量的不确定度进行评估.建立相应的不确定度数学模型，根据测试过程分析不确定度来源有7个方面，计算各不确定度分量，得到火龙果中铁含量测定结果是X=（1.308±0.281）mg/100 g（k=2）.测量过程不确定度的主要来源是样品溶液测量、样品空白及样品溶液定容等3个方面，其中，标准曲线制作和工作曲线拟合引起的不确定度最大.不确定度评定结果可为水果等营养元素检测方面提供参考，避免或减少一些不必要检测误差，使测试结果更加准确.     

Three‐phase hollow fiber liquid‐phase microextraction combined with HPLC for determination of three trace acidic plant growth regulators in Anoectochilus roxburghii (Wall.) Lindl

The analysis of plant growth regulators presents a challenge due to their trace quantities and complex matrices. A novel, simple, and effective analytical method for the determination of three trace acidic plant growth regulators in Anoectochilus roxburghii (Wall.) Lindl was developed to address this issue. Three‐phase hollow fiber liquid‐phase microextraction combined with high‐performance liquid chromatography was applied for the enrichment, purification, and determination of three acidic plant growth regulators, namely, indole‐3‐acetic‐acid, indole‐3‐butyric‐acid, and (+)‐abscisic acid. The factors affecting extraction performance, including extractant species, pH of donor and acceptor phases, salt addition dosage, extraction time, temperature, and stirring rate, were investigated and optimized. Under optimum conditions, the proposed method provided good linearity (R², 0.9994–0.9999), low limit of detection (0.038–0.12 ng/mL), and acceptable relative recoveries (56.7–117.6%). The enrichment factors were between 153 and 328. The developed method was successfully applied to the enrichment and determination of plant growth regulators in Anoectochilus roxburghii (Wall.) Lindl and exhibited increased purification capacity, higher sensitivity, and decreased organic solvent consumption compared with conventional sample preparation methods. This method may provide a testing platform for the monitoring of plant growth regulator residues, ensuring the safe and effective use of traditional Chinese medicine.     

Magnetic micro‐solid‐phase extraction based on magnetite‐MCM‐41 with gas chromatography–mass spectrometry for the determination of antidepressant drugs in biological fluids

A new facile magnetic micro‐solid‐phase extraction coupled to gas chromatography and mass spectrometry detection was developed for the extraction and determination of selected antidepressant drugs in biological fluids using magnetite‐MCM‐41 as adsorbent. The synthesized sorbent was characterized by several spectroscopic techniques. The maximum extraction efficiency for extraction of 500 μg/L antidepressant drugs from aqueous solution was obtained with 15 mg of magnetite‐MCM‐41 at pH 12. The analyte was desorbed using 100 μL of acetonitrile prior to gas chromatography determination. This method was rapid in which the adsorption procedure was completed in 60 s. Under the optimized conditions using 15 mL of antidepressant drugs sample, the calibration curve showed good linearity in the range of 0.05–500 μg/L (r ² = 0.996–0.999). Good limits of detection (0.008–0.010 μg/L) were obtained for the analytes with good relative standard deviations of <8.0% (n  = 5) for the determination of 0.1, 5.0, and 500.0 μg/L of antidepressant drugs. This method was successfully applied to the determination of amitriptyline and chlorpromazine in plasma and urine samples. The recoveries of spiked plasma and urine samples were in the range of 86.1–115.4%. Results indicate that magnetite micro‐solid‐phase extraction with gas chromatography and mass spectrometry is a convenient, fast, and economical method for the extraction and determination of amitriptyline and chlorpromazine in biological samples.     

High‐throughput determination of fungicides in grapes using thin‐film microextraction coupled with liquid chromatography–tandem mass spectrometry

A high‐throughput and environmentally friendly method based on 96‐well plate thin‐film microextraction was established to determine 14 fungicides in grapes and grape juice using liquid chromatography–tandem mass spectrometry. The thin‐film microextraction optimized method consisted of 60 min of extraction at pH 6.0 with the addition of sodium chloride (2–5%). Acetonitrile/water in the ratio of 8:2 was used for desorption analytes for 60 min. Evaluation of different extractive phases showed that polyacrylonitrile–polystyrene–divinylbenzene was the optimum coating. The linearity of the method was good in the range of 0.01–0.5 μg/mL for 14 fungicides with determination coefficients (R²) from 0.990 to 0.999, which indicated good linearity for both the grape juice and grape matrixes. The limit of detection was in the range of 0.002–0.01 μg/mL. The limit of quantitation was in the range of 0.01 mg/kg according to the minimum fortified level. The average absolute recoveries of the 14 fungicides ranged from 75.0 to 118.3%. The intraday relative standard deviation (n = 4) and interday relative standard deviation (n = 4) were 5.6–13.0% and 1.6–6.4%, respectively. This study showed that this method can be used for analyzing 96 samples in parallel, and the sample preparation time was approximately 2.0 min per sample. In addition, this approach offers a green and low‐cost sample pretreatment technique for future analyses.     

Determination of ultraviolet filter compounds in environmental water samples using membrane‐protected micro‐solid‐phase extraction

A method based on membrane‐protected micro‐solid‐phase extraction coupled with gas chromatography and mass spectrometry was developed for the determination of six ultraviolet filter compounds in various aqueous media. Multiwalled carbon nanotubes as the sorbent were encapsulated in a sealed polypropylene membrane packet and immersed in the sample to extract the analytes, and then dichloromethane was used for desorption purpose. The method was sensitive enough for quantitative analysis of the target analytes, with limits of quantification between 0.01 and 0.06 μg/L, and produced a linear response (R² > 0.991) over the calibration range (0.05–6 μg/L). The obtained reproducibility was practically suitable with relative standard deviation values of less than 14% in pure water (spiked at 0.20/μg L) and less than 15% in real samples. The optimized method was applied for the analysis of real water samples with varying matrix complexity: tap, river, and dam water; geothermal spa; and sewage treatment plant effluent. Various levels and patterns of contamination were observed in the examined samples, while the sample from spa was the most contaminated, regarding the target analytes. Matrix spikes and matrix spike replicates were also analyzed to validate the technique for analysis of real aqueous samples, and satisfactory results were achieved.     

Stability of arsenic peptides in plant extracts: off-line versus on-line parallel elemental and molecular mass spectrometric detection for liquid chromatographic separation

The instability of metal and metalloid complexes during analytical processes has always been an issue of an uncertainty regarding their speciation in plant extracts. Two different speciation protocols were compared regarding the analysis of arsenic phytochelatin (As^IIIPC) complexes in fresh plant material. As the final step for separation/detection both methods used RP-HPLC simultaneously coupled to ICP-MS and ES-MS. However, one method was the often used off-line approach using two-dimensional separation, i.e. a pre-cleaning step using size-exclusion chromatography with subsequent fraction collection and freeze-drying prior to the analysis using RP-HPLC–ICP-MS and/or ES-MS. This approach revealed that less than 2% of the total arsenic was bound to peptides such as phytochelatins in the root extract of an arsenate exposed Thunbergia alata, whereas the direct on-line method showed that 83% of arsenic was bound to peptides, mainly as As^IIIPC₃ and (GS)As^IIIPC₂. Key analytical factors were identified which destabilise the As^IIIPCs. The low pH of the mobile phase (0.1% formic acid) using RP-HPLC–ICP-MS/ES-MS stabilises the arsenic peptide complexes in the plant extract as well as the free peptide concentration, as shown by the kinetic disintegration study of the model compound As^III(GS)₃ at pH 2.2 and 3.8. But only short half-lives of only a few hours were determined for the arsenic glutathione complex. Although As^IIIPC₃ showed a ten times higher half-life (23 h) in a plant extract, the pre-cleaning step with subsequent fractionation in a mobile phase of pH 5.6 contributes to the destabilisation of the arsenic peptides in the off-line method. Furthermore, it was found that during a freeze-drying process more than 90% of an As^IIIPC₃ complex and smaller free peptides such as PC₂ and PC₃ can be lost. Although the two-dimensional off-line method has been used successfully for other metal complexes, it is concluded here that the fractionation and the subsequent freeze-drying were responsible for the loss of arsenic phytochelatin complexes during the analysis. Hence, the on-line HPLC–ICP-MS/ES-MS is the preferred method for such unstable peptide complexes. Since freeze-drying has been found to be undesirable for sample storage other methods for sample handling needed to be investigated. Hence, the storage of the fresh plant at low temperature was tested. We can report for the first time a storage method which successfully conserves the integrity of the labile arsenic phytochelatin complexes: quantitative recovery of As^IIIPC₃ in a formic acid extract of a Thunbergia alata exposed for 24 h to 1 mg As^v L⁻¹ was found when the fresh plant was stored for 21 days at 193 K. Figure On-line HPLC–ICP-MS/ES-MS (bottom) is the preferred method for MS determination of unstable arsenic peptide complexes in plant extracts, since this avoids fractionation and subsequent freeze-drying that are responsible for loss of arsenic phytochelatin complexes in the 2D off-line method (top) Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Gas chromatography-mass spectrometry with solid-phase microextraction method for determination of methyl salicylate and other volatile compounds in leaves of<Emphasis Type="Italic"> Lycopersicon esculentum</Emphasis>

Methyl salicylate (MeSA) in many plants is a important signaling compound, which plays an important role in a pathogen-induced defense response. In this paper, gas chromatography-mass spectrometry (GC-MS) with headspace solid-phase microextraction (HS-SPME) was developed for determination of MeSA and other volatile compounds in leaves of a tomato plant (Lycopersicon esculentum). Tomato leaves were ground under liquid nitrogen and sampled by HS-SPME, with a 100 m polydimethylsiloxane fiber, and finally analyzed by GC-MS. Eighteen compounds in the leaves of tomato plant infested by tobacco mosaic virus (TMV) were separated and identified, among them MeSA, which was quantitatively analyzed by the standard addition method. MeSA concentrations higher than 2.0 g g^–1 fresh weight accumulated in leaves of TMV-infested tomato plant as the defense response to TMV. A similar concentration of MeSA in the leaves of MeSA-treated tomato plant was also found. No MeSA in leaves of control tomato plant was detected. These findings suggest that MeSA might be a signaling compound in the tomato plant response to TMV. The present method for determination of MeSA required only simple sample preparation and no organic solvent, and provided an excellent relative standard deviation of less than 5.0% and a low detection limit of 10 ng g^–1 fresh weight for MeSA. These results show that GC-MS-HS-SPME is a simple, rapid and sensitive method for determination of MeSA and other plant-signaling compounds in plant tissues.     

Cadmium determination in natural waters at the limit imposed by European legislation by isotope dilution and TiO<Subscript>2</Subscript> solid-phase extraction

The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 μg L⁻¹ depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below μg L⁻¹ level in natural water. It is based on solid-phase extraction using TiO₂ nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg⁻¹ (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3–4% k = 2 for a cadmium content of around 100 ng kg⁻¹). We applied the developed method to the groundwater and wastewater samples ERM-CA615 and BCR-713, respectively, and results agreed with certificate values within uncertainty statements.     

Metabolic Fingerprinting of acs7 Mutant and Wild-Type Arabidopsis thaliana Under Salt Stress by Ultra Performance Liquid Chromatography Coupled with Quadrupole/Time of Flight Mass Spectrometry

The metabolic fingerprints of the acs7 mutant and wild-type (WT) of the model plant Arabidopsis thaliana with and without salt stress were compared by ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC-QTOF MS). Separations were performed on C₁₈ column (2.1 mm × 100 mm, 1.7 µm). A linear gradient elution of acetonitrile and 0.1% formic acid solution was used at a flow rate of 0.4 mL/min. Principal components analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were combined for the data treatment. A clear discrimination was obtained by both PCA and PLS-DA. The acs7 salt-treated group was closer to the control group samples than the WT salt-treated group samples. Several potential stress-induced ions were revealed as markers of salt stress. The markers 12-oxophytodienoic acid (OPDA), arabidopside A, sinapoyl malate, linolenic acid, and abscisic acid were identified by the accurate mass (from TOF MS). Linolenic acid and OPDA are the biosynthetic precursors of jasmonic acid (JA) by the octadecanoid pathway. The JA content determination results indicated that salt stress increased the JA levels in the leaves of the WT plant, but there was no significant increase in the JA content of acs7 after salt treatment. These data suggested the responses to salt stress of the acs7 mutant and WT A. thaliana were different in the octadecanoid pathway.     

Polypyrrole‐magnetite dispersive micro‐solid‐phase extraction combined with ultraviolet‐visible spectrophotometry for the determination of rhodamine 6G and crystal violet in textile wastewater

Polypyrrole‐magnetite dispersive micro‐solid‐phase extraction method combined with ultraviolet‐visible spectrophotometry was developed for the determination of selected cationic dyes in textile wastewater. Polypyrrole‐magnetite was used as adsorbent due to its thermal stability, magnetic properties, and ability to adsorb Rhodamine 6G and crystal violet. Dispersive micro‐solid‐phase extraction parameters were optimized, including sample pH, adsorbent amount, extraction time, and desorption solvent. The optimum polypyrrole‐magnetite dispersive micro‐solid phase‐extraction conditions were sample pH 8, 60 mg polypyrrole‐magnetite adsorbent, 5 min of extraction time, and acetonitrile as the desorption solvent. Under the optimized conditions, the polypyrrole‐magnetite dispersive micro‐solid‐phase extraction with ultraviolet‐visible method showed good linearity in the range of 0.05–7 mg/L (R ² > 0.9980). The method also showed a good limit of detection for the dyes (0.05 mg/L) and good analyte recoveries (97.4–111.3%) with relative standard deviations < 10%. The method was successfully applied to the analysis of dyes in textile wastewater samples where the concentration found was 1.03 mg (RSD ±7.9%) and 1.13 mg/L (RSD ± 4.6%) for Rhodamine 6G and crystal violet, respectively. It can be concluded that this method can be adopted for the rapid extraction and determination of dyes at trace concentration levels.     

Magnetic amino‐functionalized hollow silica‐titania microsphere as an efficient sorbent for extraction of pesticides in green and roasted coffee beans

This study describes the synthesis and application of a magnetic amino‐functionalized hollow silica‐titania microsphere as a new sorbent for magnetic dispersive micro‐solid phase extraction of selected pesticides in coffee bean samples. The sorbent was fully characterized by Fourier‐transform infrared spectroscopy, field emission scanning electron microscopy, transition electron microscopy, energy‐dispersive X‐ray spectroscopy, and vibrating sample magnetometry techniques. Significant extraction parameters affecting the proposed method, such as extraction time, sorbent amount, sample solution pH, salt amount, and desorption conditions (desorption solvent and time) were investigated and optimized. All the figures of merits were validated in coffee bean samples under the matrix‐matched calibration method. Linear dynamic ranges were 5–250 µg/kg with the determination coefficients (R²) > 0.9980. The limits of detection for the pesticides of chlorpyrifos, malathion, hexaconazole, and atrazine were 1.42, 1.43, 1.35, and 1.33 µg/kg, respectively. Finally, the method was successfully applied for the determination of the pesticides in green and roasted coffee bean samples, and the obtained recoveries were in the range of 74–113% for spiked samples. The prepared sorbent could be used for the magnetic dispersive micro‐solid phase extraction of pesticides in the plant‐derived food matrix.     

Stacking and determination of phenazine-1-carboxylic acid with low p<Emphasis Type="Italic">K</Emphasis><Subscript>a</Subscript> in soil via moving reaction boundaryformed by alkaline and double acidic buffers in capillary electrophoresis

As shown herein, a normal moving reaction boundary (MRB) formed by an alkaline buffer and a single acidic buffer had poor stacking to the new important plant growth promoter of phenazine-1-carboxylic acid (PCA) in soil due to the leak induced by its low pK _a. To stack the PCA with low pK _a efficiently, a novel stacking system of MRB was developed, which was formed by an alkaline buffer and double acidic buffers (viz., acidic sample and blank buffers). With the novel system, the PCA leaking into the blank buffer from the sample buffer could be well stacked by the prolonged MRB formed between the alkaline buffer and blank buffer. The relevant mechanism of stacking was discussed briefly. The stacking system, coupled with sample pretreatment, could achieve a 214-fold increase of PCA sensitivity under the optimal conditions (15 mM (pH 11.5) Gly-NaOH as the alkaline buffer, 15 mM (pH 3.0) Gly-HCl-acetonitrile (20%, v/v) as the acidic sample buffer, 15 mM (pH 3.0) Gly-HCl as the blank buffer, 3 min 13 mbar injection of double acidic buffers, benzoic acid as the internal standard, 75 μm i.d. × 53 cm (44 cm effective length) capillary, 25 kV and 248 nm). The limit of detection of PCA in soil was decreased to 17 ng/g, the intra-day and inter-day precision values (expressed as relative standard deviations) were 3.17–4.24% and 4.17–4.87%, respectively, and the recoveries of PCA at three concentration levels changed from 52.20% to 102.61%. The developed method could be used for the detection of PCA in soil at trace level.     

Uncertainty in aflatoxin B<Subscript>1</Subscript> analysis using information from proficiency tests

We describe how to calculate uncertainty in the determination of aflatoxin B₁ in nuts and maize using an HPLC method with prederivatisation with trifluoroacetic acid and fluorescence detection. The uncertainty is easily calculated using the information obtained from the participation in several proficiency tests. All the sources of uncertainty are grouped in two terms: (1) matrix variability, intermediate precision and sample heterogeneity, and (2) method concordance. This methodology has the advantage that no extra work needs to be done because all the information to calculate uncertainty comes from proficiency tests. The uncertainty values were calculated using samples whose concentration ranged between 2 and 20 g L^–1. The relative standard uncertainty computed for aflatoxin B₁ was 16.3%.     

Validation of the HS-GC-FID method for the determination of ethanol residue in tablets

This paper describes the validation of a HS-GC-FID method (based on the Pharmacopeia’s method) for the determination of ethanol content in tablets. A general view of the procedure development/optimization process is presented. The main point of this study is the calculation of validation parameters. Selectivity of the method was determined. Linearity (r > 0.997) was observed in the range from 9.0 to 3,040 μg of ethanol per sample (because the mass of the tablets used was around 200 mg, this corresponds to 45–15,200 μg g⁻¹). The method showed good recoveries (average 99.0%), and a relative standard deviation for repeatability and intermediate precision of 4.5% and 5.5% respectively. The limit of detection was calculated to be 3.0 μg of ethanol per sample (15 μg g⁻¹). The uncertainty budget was done according to the "Guide to the Expression of Uncertainty in Measurement" (GUM)[1], and a relative expanded uncertainty was estimated as 4.8%.     

Determination of HEPES in <Superscript>68</Superscript>Ga-labeled peptide solutions

A practical and reliable HPLC method was used for the determination of 2-[4-N-(2-hydroxyethyl)-1-piperazinyl]-N′-ethanesulfonic acid (HEPES) content in the ⁶⁸Ga-labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-Nal3-octreotide (DOTANOC). Linearity of this method was observed in a concentration range of 0.01–10 mg mL⁻¹ and the quantitative limit (signal to noise = 11) was determined as 10 μg mL⁻¹. The HEPES concentration in the final products of ⁶⁸Ga-DOTANOC was typically lower than the detection limit. Pure water and HEPES buffer as reaction medium were investigated using various activities of gallium-68. It was demonstrated that the presence of HEPES buffer consistently furnished very high radiochemical purity of ⁶⁸Ga-DOTANOC, which remained stable for several hours post-labeling. Evidence is provided that in addition to its role as a buffer, HEPES also functions as a radioprotectant agent.     

Determination of N‐nitrosamines in cosmetic products by vortex‐assisted reversed‐phase dispersive liquid–liquid microextraction and liquid chromatography with mass spectrometry

A new analytical method for the simultaneous determination of trace levels of seven prohibited N‐nitrosamines (N‐nitrosodimethylamine, N‐nitrosoethylmethylamine, N‐nitrosopyrrolidine, N‐nitrosodiethylamine, N‐nitrosopiperidine, N‐nitrosomorpholine, and N‐nitrosodiethanolamine) in cosmetic products has been developed. The method is based on vortex‐assisted reversed‐phase dispersive liquid–liquid microextraction, which allows the extraction of highly polar compounds, followed by liquid chromatography with mass spectrometry. The variables involved in the extraction process were studied to obtain the highest enrichment factor. Under the selected conditions, 75 μL of water as extraction solvent was added to 5 mL of n‐hexane sample solution and assisted by vortex mixing during 30 s to form the cloudy solution. The method was successfully validated showing good linearity (0.5–50 ng/mL), enrichment factors up to 65 depending on the target compound, limits of detection values of 1.8–50 ng/g, and good repeatability (RSD < 9.8%). Finally, the proposed method was applied to different cosmetic samples. Quantitative relative recovery values (80–113%) were obtained, thus showing that matrix effects were negligible. The achieved analytical features of the proposed method, besides of its simplicity and affordability, make it useful to perform the quality control of cosmetic products to ensure the safety of consumers.