Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water

A rapid, sensitive, and selective detection method of nitrite in foods and water was established by surface-enhanced Raman spectroscopy (SERS) based on the diazo reaction of nitrite with p-nitroaniline and 1-naphthylamine in acidic solution. The azo dye (4-(4-nitrophenyldiazenyl)naphthalene-1-aminium, NNA), which was derived from the diazo reaction, was determined by SERS using citrate-coated silver nanoparticles (AgNPs) as SERS substrates. The concentrations of nitrite in samples were finally calculated from the intensities of SERS signals generated by NNA in the testing solutions. By using the present method combined with a portable miniature Raman spectrometer, on-site determination of nitrite could be performed easily and efficiently. The effects of several experimental parameters on the intensity of SERS signals, such as the volume of AgNP solution and the mixing time of AgNPs and NNA, were investigated. The linear range of the method was 0.1–10.0 mg L^?1. The limits of detection (LODs) were 0.01, 0.03, and 0.05 mg L^?1 at 720, 1,459, and 1,609 cm^?1, respectively. The method was applied to the determination of nitrite in real food and water samples, with recoveries in the range of 86.9–103.4 % and relative standard deviations (RSDs) less than 9.64 %.     

SERS Detection of Insecticide Amitraz Residue in Milk Based on Au@Ag Core-Shell Nanoparticles

A simple, rapid, and environmentally friendly surface-enhanced Raman scattering (SERS) method was developed for the determination of trace amitraz in milk with the use of silver-coated gold nanoparticles (Au@Ag NPs) as enhancing reagent. The normal Raman and SERS spectra of amitraz were analyzed, and the peaks were assigned by density functional theory. The morphology of Au@Ag NPs was characterized and confirmed by transmission electron microscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The SERS effects of Au@Ag NPs were investigated, including the types of solvents for dissolving amitraz, the volume ratio of the Au@Ag NPs and amitraz, and the concentration of aggregating agent (NaCl) for aggregate Au@Ag NPs. Results show that ethanol exerts the least interference on the SERS spectrum of amitraz and is more environmentally sound than methanol. The strongest SERS signal appeared when the volume ratio of Au@Ag NPs and amitraz was 2:1. Moreover, the strongest SERS signals appeared when the concentration of NaCl was 0.025 mol L^?1 because of appropriate aggregation. Under the optimum conditions, the concentration of amitraz presents a good linear relationship with Raman intensity (723 cm^?1) with a linear range of 9.77 × 10^?4~2.93 × 10^?2 g L^?1. The detected recoveries of amitraz in milk were between 81.7 and 100.5% with a relative standard deviation (RSD) of 2.61~5.51%.     

Detection and differentiation of Salmonella serotypes using surface enhanced Raman scattering (SERS) technique

This research was conducted to prove that developed silver biopolymer nanoparticle substrate for surface enhanced Raman scattering (SERS) technique could detect and differentiate three different serotypes of Salmonella. Nanoparticle was prepared by adding 100 mg of silver nitrate to a 2 % polyvinyl alcohol solution, then adding 1 % trisodium citrate to reduce silver nitrate and produce silver encapsulated biopolymer nanoparticles. Then, nanoparticle was deposited on a stainless steel plate and used as SERS substrate. Fresh cultures of Salmonella typhimurium, Salmonella enteritidis and Salmonella infantis were washed and suspended in 10 mL of sterile deionized water. Approximately 5 μl of the bacterial suspensions were placed on the substrate individually and exposed to 785 nm laser excitation. SERS spectral data were recorded between 400 and 1,800 cm^?1. SERS signals were collected from 15 different spots on the substrate for each sample. PCA model was developed to classify Salmonella serotypes. PC1 identified 92 % of the variation between the Salmonella serotypes, and PC2 identified 6 % and in total 98 % between the serotypes. Soft independent modeling of class analogies of validation set gave an average correct classification of 92 %. Comparison of the SERS spectra of Salmonella serotypes indicated that both isolates have similar cell walls and cell membrane structures which were identified by spectral regions between 520 and 1,050 cm^?1. However, major differences were detected in cellular genetic material and proteins between 1,200 and 1,700 cm^?1. SERS with silver biopolymer nanoparticle substrate could be a promising tool in pathogen detection and it would potentially be used to classify them.     

Ultrasensitive Detection of Enrofloxacin in Chicken Muscles by Surface-Enhanced Raman Spectroscopy Using Amino-Modified Glycidyl Methacrylate-Ethylene Dimethacrylate (GMA-EDMA) Powdered Porous Material

Illegally use of enrofloxacin in chicken has raised serious concerns due to its negative effects on public health. In this study, surface-enhanced Raman spectroscopy (SERS) using amino-modified glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) powdered porous material was developed and validated to detect enrofloxacin in chicken muscles. By this method, enrofloxacin in chicken muscles was successfully detected at a concentration of 0.01 mg kg^?1, which was lower than the legal maximum residue limit. And the unique “fingerprint-like” spectral patterns of enrofloxacin obtained from SERS spectra could be used for identification and characterization. Compared with high-performance liquid chromatography, the assay of six samples with SERS was rapid in less than 40 min, and the detection was highly sensitive. The results demonstrate that SERS using GMA-EDMA powdered porous material can be potentially employed as a screening tool for rapid detection of residual drugs in a large amount of food samples.     

Determination of 6-Benzylaminopurine and Hg<Superscript>2+</Superscript> in Bean Sprouts and Drinking Mineral Water by Surface-Enhanced Raman Spectroscopy

A novel method for the determination of 6-benzyladenine (6-BA) in bean sprouts and Hg²⁺ in drinking mineral water by surface-enhanced Raman spectroscopy (SERS) was described. 6-BA exhibits obvious SERS signal by using the substrate of silver nanoparticles (AgNPs), and the presence of Hg²⁺ could cause the decrease of SERS signal of 6-BA. The effects of type of aggregation agent, type and level of pH buffer solution, amount of AgNPs, mixing time, concentration of 6-BA, and reaction time on the SERS signals were investigated. Under the optimized experimental conditions, good linear responses were obtained for 6-BA and Hg²⁺ in the concentration ranges of 10–200 μg L^?1 and 5–200 μg L^?1, respectively. By the present method, the limits of detection (LODs) for the determination of 6-BA and Hg²⁺ are 3.3 and 0.20 μg L^?1, and the recoveries of 6-BA and Hg²⁺ in spiked samples are 85.5–113.0 % and 98.2–111.5 %, respectively.     

Multi-residual Pesticide Monitoring in Commercial Chinese Herbal Medicines by Gas Chromatography–Triple Quadrupole Tandem Mass Spectrometry

To investigate multi-residual pesticide monitoring data in commercial Chinese herbal medicines on major markets, an easy, rapid, and selective gas chromatography with mass spectrometry (GC/MS/MS) method was established for simultaneously determining multi-residual pesticides including organochlorine, pyrethroid, carbamate, and organophosphorus pesticides in Chinese herbal medicines. The analytical method was based on an efficient extraction procedure and further cleanup steps by solid-phase extraction columns, yielding recovery rates in the range of 70.0–120.0 % for the majority of pesticides, except for hexachlorobenze, diazinon, β-HCH, δ-HCH, and omethoate, with precision values expressed as relative standard deviation of 0.1–14.7 %. The limits of detection of the established GC/MS/MS method for all investigated pesticides ranged from 0.01 to 3.6 μg kg^?1 and limits of quantification from 0.03 to 11.88 μg kg^?1. With this validated method, multi-residual pesticides of 132 Chinese herbal medicine samples were analyzed. The monitoring results indicated that pesticide residue was found in 74 samples. In total, 51 pesticides were found with detection rate ranging from 0.76 to 18.94 %. An 82.3 % of positive pesticides were found in less than 6 % of samples. Hexachlorobenzene was found in 25 samples, quintozene in 15 samples, and acephate and simazine in 13 samples. Concentrations of pesticide residue from monitoring data obtained ranged from 0.5 to 203.5 μg kg^?1. The simple and rapid method can be used as routine analysis method in multi-residual pesticide monitoring of Chinese herbal medicines.     

Optimization of the QuEChERS Method for Determination of Pesticide Residues in Chicken Liver Samples by Gas Chromatography-Mass Spectrometry

The goal of this research was to evaluate the application of Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method for the determination of organochlorine, organophosphate, and carbamate pesticides in fatty animal matrices such as liver of chicken obtained from National Research Institute of Animal Production in Balice (Poland). Pesticides extraction effectiveness was evaluated at two different spiking levels (0.010 and 0.020 mg kg^?1) and efficiency of the dispersive solid-phase extraction (d-SPE) clean-up step was evaluated by comparison adding different d-SPE sorbent combinations (PSA?+?GCB, PSA?+?C₁₈, PSA?+?SAX, and PSA?+?NH₂). The analysis of pesticide residues was performed by gas chromatography ion trap mass spectrometry (GC/IT-MS). The linear relation was observed from 0 to 400 ng mL^?1 and the determination coefficient R ²?>?0.997 in all instances for all target analytes. Better recoveries were obtained in samples at 0.020 mg kg^?1 spiking level. The recoveries were in the range 70–120 %, with relative standard deviation (RSD) values lower than 15 % at 0.020 mg kg^?1 spiking level for most pesticides. Similar recovery ratios were obtained with the four different combinations of sorbents tested in the clean-up step, with better precision when the (PSA?+?SAX) combination was tested. Limits of detection (LODs) ranged from 0.001 to 0.005 mg kg^?1 and limits of quantification (LOQs) ranged from 0.003 to 0.015 mg kg^?1. The proposed method was successfully applied analyzing pesticide residues in real chicken liver samples; detectable pesticide residues were observed, but in all of the cases, the contamination level was lower than the default maximum residue levels (MRLs) set by European Union (EU), Regulation (EC) N 396/2005.     

Multicommuted Flow Analysis Procedure for Total Polyphenols Determination in Wines Employing Chemiluminescence Detection

A flow procedure based on a multicommuted flow analysis process for the determination of polyphenolic compounds in wine employing chemiluminescence as detection technique is described. The method was based on the reaction of hypochlorite with gallic acid, the remaining hypochlorite reacted with luminol in an alkaline medium generating electromagnetic radiation with maximum emission at 425 nm. The luminescence intensity presented an inverse relationship to the concentration of polyphenol compounds, which was monitored employing a homemade luminometer. The flow system manifold was designed to use solenoid mini-pumps for propelling fluids in order to obtain a setup of downsized dimension. After setting the variables control of the flow system and the concentrations of the reagent, the following features were achieved: a linear response ranging from 10 to 100 mg L^?1 gallic acid (R ²?=?0.997), a relative standard deviation of 3.4 (n?=?11) for a 50 mg L^?1 gallic acid solution, a detection limit of 6.6 mg L^?1, a sampling throughput of 180 determination h^?1, and a waste generation of 1.1 mL per determination.     

Determination of Polyphenol Content by Formation of Unstable Compound Using a Mini-Pump Multicommutation System

This article describes a multicommuted flow procedure for photometric determination of the polyphenol content in wines and teas, exploiting the formation of unstable intermediate products, by the reaction of sodium hypochloride with gallic acid. Because the lifetime of the formed compound is very short, a special flow cell was designed in order to enable mixing of sample and reagent solution within the flow cell, thus allowing signal monitoring, while compound formation proceeded. The flow system manifold comprised three solenoid mini-pumps to propel sample, reagent solution, and carrier fluid. The photometer consisted of a photodiode and a light emitting diode (LED) with maximum emission at 490 nm. Under the selected operational conditions, useful features including a linear response ranging from 62 to 1000 mg L^?1 gallic acid solution (R?=?0.9987), a detection limit of 21 mg L^?1 gallic acid, a sampling rate of 120 determinations per hour, a relative standard deviation of 1.9 % (n?=?20) for a typical solution containing 400 mg L^?1 gallic acid, and a waste generation of 1.0 mL per determination were also achieved. Medium recovery values of 96.2?±?10.4 and 101.9?±?7.3 % for wines and teas, respectively, were achieved.     

Ultrasensitive and Specific Detection of Salbutamol in Swine Feed,Meat, and Urine Samples by a Competitive Immunochromatographic Test Integrated with Surface-Enhanced Raman Scattering

Salbutamol (SAL), a kind of β-agonist which can enhance the lean meat-to-fat ratio, has been inhibited as an additive used in animal feeds for livestock production in many countries due to its harmful effect to the consumers. In this study, an ultrasensitive and specific competitive immunochromatographic test (ICT) integrated with surface-enhanced Raman scattering (SERS) for the detection of SAL was described. The immunoprobe was prepared by immobilizing polyclonal antibody against SAL on the surface of Au@Ag nanoparticles in which the Raman reporter (4-mercaptobenzoic acid, MBA) had been sandwiched. After ICT procedures, the specific SERS signals generated from MBA on the test line of the ICT strip were measured for the quantitative determination of SAL. The assay was completed in 15 min. The IC₅₀ and the limit of detection (LOD) values of the assay for SAL were 0.028 ng mL^?1 and 3.0 pg mL^?1, respectively. There was no cross-reactivity (CR) of the assay with other three β-agonists (clenbuterol, phenylethanolamine A, and ractopamine), showing high specificity of the assay. Spiking experiments indicated that the average recoveries (n?=?3) of SAL from swine feed, meat, and urine samples were in ranges of 98.4–105.2 % with the relative standard deviations (RSDs) of 1.7–7.8 %. The results demonstrated that the proposed ICT was a feasible method for ultrasensitive and specific detection SAL in swine feed, meat and urine samples, and could be extended for the detection of other target analytes.     

Quantification of Catechin and Epicatechin in Foods by Enzymatic-Spectrophotometric Method with Tyrosinase

Catechin and epicatechin are important phenolic compounds found mainly in tea leaves, cocoa beans, and in the peels and seeds of fruits. The reliable detection of these compounds by spectrophotometry is limited by the interference with substances that absorb light at similar wavelengths; thus, an effective alternative is to detect the oxidation products of these compounds at more specific wavelengths. This study aimed to develop an analytical method to quantify total catechin and epicatechin in some food samples (cocoa beans, guarana powder, apples, and tea leaves) by enzymatic oxidation with tyrosinase. The samples were extracted in an ultrasonic bath and the purified extracts were oxidized with tyrosinase solution. The quinones formed in the reaction were detected by spectrophotometry. The method was selective and presented linearity between 1.21 and 7.26 mg g^?1, limit of detection of 0.48 mg g^?1, and limit of quantification of 1.61 mg g^?1. The accuracy of the proposed method was reasonable, with recoveries between 84.3 and 90.7% in the fortified matrices. High precision was observed, with low coefficients of variation for repeatability (3.17 to 3.68%) and intermediate precision (3.27%). In cocoa beans, the total catechin and epicatechin level was 1.65 mg g^?1 (3.58 mg g^?1). The successful application of the method was also demonstrated in guarana powder. Therefore, the method can be applicable for spectrophotometric analysis of catechin and epicatechin in samples containing above 1.61 mg g^?1 of these compounds.     

Quantitative Detection of Isofenphos-Methyl in Corns Using Surface-Enhanced Raman Spectroscopy (SERS) with Chemometric Methods

Residual pesticides in agricultural production are one of the major food safety concerns around the world. In this study, we investigated the amount of isofenphos-methyl in corns by using surface-enhanced Raman spectroscopy (SERS) coupled with chemometric methods. The highest isofenphos-methyl peak at 1043 cm^?1 was used to detect and quantify the amount of isofenphos-methyl spiked in methanol-water (1:1) solvent and corns. The limits of detection (LODs) of isofenphos-methyl in methanol-water solvent and corns were 0.01 μg/mL and 0.01 μg/g, respectively. Quantitative detection of isofenphos-methyl residues (0–5 μg/mL) was conducted using partial least squares (PLS) model. Based upon the results of leave-one-out cross-validation, isofenphos-methyl could be predicted by PLS (the correlation coefficient was 0.9964) with a low root mean square error of calibration (RMSEC=0.146). The developed SERS method provides a much simpler and more sensitive way to monitor isofenphos-methyl for safe production of corns, which can be extended to the other agricultural products.     

Application of surface enhanced Raman spectroscopy for analyses of restricted sulfa drugs

The presence of sulfonamide residues in muscle foods is an important concern for consumers and regulatory agencies since these residues may pose potential health risks and result in an increase of drug-resistant bacteria. Surface enhanced Raman spectroscopy (SERS) was applied to analyze three sulfa drugs including sulfamerazine, sulfamethazine and sulfamethoxazole with concentrations ranging from 10 ng mL^?1 to 5 ??g mL^?1. Partial least squares regression (PLS) and principal component analysis (PCA) were used for the spectral data analyses. The three sulfa drugs could be detected at concentration levels as low as 10 ng mL^?1. For the quantitative analyses, the R ² values of actual sulfa drug concentrations versus their concentrations predicted by the PLS models ranged from 0.8149 to 0.9009. Plotting of principal components based upon PCA showed clear, separated clusters between different sulfonamides. This study indicated potential for detection and determination of trace amounts of prohibited or restricted drugs with SERS technology.     

A new approach to measure melamine, cyanuric acid, and melamine cyanurate using surface enhanced Raman spectroscopy coupled with gold nanosubstrates

Vibrational spectroscopic characteristics of melamine, cyanuric acid, and melamine cyanurate were measured using surface-enhanced Raman spectroscopy (SERS) coupled with gold nanosubstrates. Trace amounts of melamine and its analogues (cyanuric acid and melamine cyanurate) were characterized and quantified quickly and accurately by SERS in combination with partial least squares (PLS) analysis. Based on the relationship between the Raman intensity of the most prominent peak at around 676 cm⁻¹ and log values of melamine concentrations, the limit of detection (LOD) of SERS for melamine was estimated to be 2.6 × 10⁻⁷ mol L⁻¹ (∼33 ppb). An approximately 3 × 10⁴ fold of enhancement factor for SERS signals of melamine on gold nanosubstrates was obtained. This result was based upon the comparison of the peak at around 676 cm⁻¹ in the SERS spectra with that of normal Raman spectra of melamine in aqueous solutions. SERS spectra of cyanuric acid acquired from its solid form differ significantly from this compound in an aqueous solution, indicating a possible keto-enol isomerization reaction of cyanuric acid in water. When equal amounts of melamine and cyanuric acid were added together, spoke-like crystals of melamine cyanurate formed instantly, which could be measured and characterized by SERS. This study demonstrates that SERS could provide a fast and ultra-sensitive tool for detection and characterization of melamine and its derivative compounds in aqueous solutions.     

Simultaneous determination of pyrimethanil,cyprodinil, mepanipyrim and its metabolite in fresh and home-processed fruit and vegetables by a QuEChERS method coupled with UPLC-MS/MS

A QuEChERS procedure for the simultaneous determination of pyrimethanil, cyprodinil, mepanipyrim and its metabolite (M31) in fresh and processed fruit and vegetables was developed using ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). The determination of the four target compounds was achieved in less than 6.0 min using an electrospray ionisation source in positive mode. The limits of detection (LODs) were below 0.4 μg?kg^?1, while the limits of quantification (LOQs) did not exceed 1.5 μg?kg^?1 for all studied matrices. Good linearity of the calibration curves was obtained over the range from 0.002 to 2 mg?kg^?1, with correlation coefficients higher than 0.999. The average recoveries of this method in apple, peach, cabbage and tomato at the five spiked levels (0.002, 0.01, 0.05, 0.20 and 2.0 mg?kg^?1) ranged from 81.5% to 107.3% with relative standard deviations (RSDs) in the range of 1.5–13.9% (n = 5) for all analytes. Residue levels of anilinopyrimidine fungicides in fresh and home-processed apple, peach, cabbage and tomato were also studied. The results indicate that residue levels are significantly reduced following washing, peeling and boiling, and there is no toxic metabolite of mepanipyrim (M31) which is detected during boiling. This study provides a theoretical basis for China to draw up maximum residue limits (MRLs) and protect consumers from the negative health effects of pesticide residues detected in fruit and vegetables.     

A Biomimetic Sensor with Signal Enhancement of Ferriferrous Oxide-Reduced Graphene Oxide Nanocomposites for Ultratrace Levels Quantification of Methamidophos or Omethoate in Vegetables

In this study, we designed and synthesized Fe₃O₄/reduced graphene oxide (Fe₃O₄/rGO) and MIL@MIP, which were characterized using transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared (FT-IR), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). Here, reports a novel biomimetic electrochemical sensor (BECS) sensitized with Fe₃O₄/reduced graphene oxide (Fe₃O₄/rGO) nanocomposite using MIL@MIP film as recognition element for ultrasensitive quantification of methamidophos or omethoate. The BECS offered fast responses for methamidophos and omethoate with wide linear response ranges of 1.0 × 10^?7–1.0 × 10^?12 and 1.0 × 10^?7–1.0 × 10^?13 mol/L, respectively. Under optimized conditions, the limit of detection (LOD; S/N = 3) of the BECS method was 2.67 × 10^?13 mol/L for methamidophos and 2.05 × 10^?14 mol/L for omethoate. The BECS was applied to detection of methamidophos and omethoate in spiked cucumber and kidney bean samples, and good recoveries varied from 88.2 to 96.9 %. This proposed method was adopted for the determination of the methamidophos or omethoate residues in the rape sample, and the results were also verified using the method of gas chromatography.     

Rapid Analysis of Bitertanol in Agro-products Using Molecularly Imprinted Polymers-Surface-Enhanced Raman Spectroscopy

In this work, we first reported molecularly imprinted polymers-surface-enhanced Raman spectroscopy (MIP-SERS) for rapid detection and quantification of bitertanol in cucumber and peaches. In order to remove interference-mitigation effects and avoid template leakage, MIPs were successfully synthesized based on triadimefon molecules as the dummy template, methacrylic acid (MAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a cross-linker, and 2,2-azobis-isobutyronitrile (AIBN) as an initiator. Static adsorption experiments and Scatchard analysis were then conducted and results showed that the synthesized MIPs could rapidly and selectively adsorb and separate bitertanol from cucumber and peaches due to their predetermined recognition sites. The capacity of MIPs for absorbing bitertanol (～ 2.21 mg/g) was approximately 1.5 times that of non-imprinted polymers (NIPs) (～ 1.55 mg/g). Gold nanoparticles (AuNPs) synthesized by sodium citrate reduction method were validated as a suitable SERS colloid for enhancing Raman signals. SERS spectral peaks (760, 985, 1190, and 1279 cm^?1) were used to develop quantitative analysis based on partial least-squares regression (PLSR) for bitertanol in cucumber and peaches. The LODs for this method were 0.041 and 0.029 mg/kg in cucumber and peaches, respectively. The entire analysis process required 15 min or less. More importantly, the MIP-SERS system provided not only a rapid, sensitive, and reliable method for bitertanol detection, but also a routine for overcoming the interference-mitigation effects in the SERS technology.     

Determination of halosulfuron-methyl residues and dissipation in wheat by QuEChERS and LC-MS/MS

A sensitive and rapid analytical method based on QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation and LC-MS/MS detection was developed for the analysis of halosulfuron-methyl residues in wheat. The recoveries of halosulfuron-methyl in both the wheat plant and grain ranged from 87% to 119% and from 75% to 97%, respectively, with relative standard deviations (RSDs) of 3–9%. The limit of quantification (LOQ) was 0.005 mg kg^?1 for wheat plant and 0.001 mg kg^?1 for wheat grain. The half-life of halosulfuron-methyl in the wheat plant was 0.9–9.5 days. The terminal residue levels of halosulfuron-methyl in wheat grain were below 0.01 mg kg^?1 at harvest.     

Multi-Residue Determination of Pesticides in Açai Tropical Fruit (Euterpe oleracea) by Matrix Solid-Phase Dispersion Combined with Liquid Chromatography

An extraction method based on matrix solid phase dispersion was developed to determine bromuconazole, fenbuconazole, parathion-methyl, kresoxim-methyl, and teflubenzuron in açai using liquid chromatography with ultraviolet diode array detector. The best results were obtained using 1.0 g of açai, 3.0 g of neutral alumina as the dispersant sorbent, and cyclohexane/ethyl acetate (1:1, v/v, 20 mL) as an eluting solvent. The method was validated using açai samples fortified with pesticides at three concentration levels (0.25, 0.5, and 1.0 mg kg^?1). Average recoveries (seven replicates) ranged from 66 to 119 %, with relative standard deviations between 1.4 and 20 %. The detection and quantification limits for açai ranged from 0.02 to 0.05 mg kg^?1 and from 0.05 to 0.1 mg kg^?1, respectively.     

Assessment of the dietary intake of propylene glycol in the Korean population

An improved method for the analysis of propylene glycol (PG) in foods using a gas chromatography-flame ionisation detector (GC-FID), with confirmation by GC-MS, was validated by measuring several analytical parameters. The PG concentrations in 1073 products available in Korean markets were determined. PG was detected in 74.1% of the samples, in a concentration range from the limit of detection (n.d., 0.39 μg ml^?1) to 12,819.9 mg kg^?1. The Korea National Health and Nutrition Examination Survey (KNHANES) 2011–2013 reported the mean intake levels of PG from all sources by the general population and consumers were 26.3 mg day^?1 (0.52 mg kg^?1 day^?1) and 34.3 mg day^?1 (0.67 mg kg^?1 day^?1), respectively. The 95th percentile intake levels of the general population and consumers were 123.6 mg day^?1 (2.39 mg kg^?1 day^?1) and 146.3 mg day^?1 (2.86 mg kg^?1 day^?1), respectively. In all groups of the general population, breads were the main contributors to the total PG intake. These reports provide a current perspective on the daily intake of PG in the Korean population.