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The objective of this work is to provide a critical review of the use of ionic liquids in the microextraction of pesticide residues in fruits and vegetables. It includes an assessment of the advantages and limitations of current applications of ionic liquids in microextraction techniques. The review also aims to illustrate the impact of ionic liquids on the development of novel sorbent materials for analytical applications. The unique physicochemical properties of ionic liquids make them ideal sorbents in separation techniques. Their number of applications in analytical separation has increased considerably over the past 5 years. Therefore, this review focuses on the synthesis, purification, functionalization, and application of ionic liquids for pesticide residue analysis in fruits and vegetables with different sample preparation procedures, covering articles published in the literature since their first application in 2009.

Multivariate response surface methodology optimization using Placket–Burman and Box–Behnken designs were respectively used for the screening and optimization of significant factors for liqu...

Pesticides play vital roles in agricultural practices, but the nature and mishandling of the chemicals have led to their accumulation in moist soil, vegetables and fruits. Thus, development of efficient methods for pesticides determination is one of the most important ways to address such challenges. Multivariate response surface methodology optimisation using Placket–Burman and Box–Behnken designs were respectively used for screening and optimisation of significant factors of quick, easy, cheap, effective, rugged and safe (QuEChERS) with dispersive solid-phase extraction (SPE). Consequently, the optimised QuEChERS-dSPE technique coupled with modified ionic liquid-based (IL-based) dispersive liquid–liquid microextraction was used for sample preparation before LC–MS/MS. The developed method was validated (SANTE 11831-2017) for multi-pesticide residues determination in samples of bananas, cabbages, tomatoes, oranges and onions. The precision results were satisfactory in terms of relative standard deviation (≤ 20%) as recommended. The results of accuracy for relative recoveries (82–137%) were satisfactory because 92.5% of results were within the recommended range (70–120%). The matrix effects in all the samples were very weak (less effective) (≤ − 80%). The linearity of the evaluated results was 5–400 µg kg−1 and regression coefficients (R2) were > 0.99. The resulting limits of detection and quantitation were 0.02–0.32 and 0.07–1.06 µg kg−1, respectively, and therefore satisfactory. Certifiably, the estimated measurement uncertainties range (1–16%) was acceptable (≤ 50%). Thus, the developed method could be reliable and suitable for routine determination of multiple pesticide residues in various vegetable and fruit samples.

There have been growing interests in the rise of public GAP standards in Southeast Asia that have been implemented by the governments in the region. This paper investigates the local implementation of Malaysian public GAP standard called MyGAP by examining its effectiveness in raising the awareness and improving the land use practices of participant small-scale farmers toward better food safety and quality assurance. For this objective, 19 MyGAP certified and 57 uncertified durian farms in the state of Pahang, Malaysia were surveyed. The research found that while certified farm managers showed much better understanding of the basic intent of the policy than uncertified farms, their interests in and assessment of the merits from the scheme concentrate in economic realms rather than related to the original policy goal of food safety and quality assurance. As regards land use practices, certified farms showed much better performance than uncertified farms in record keeping and pesticide management. A set of circumstantial evidence seems to suggest, however, that certified farms' better pesticide management is more likely due to the certification screening of already-well-performing farmers than due to improved practices ex post facto. The observed significant discrepancy in the recent MyGAP adoption rates between durian in Pahang State and crop nationwide makes it difficult for us to determine the degree to which MyGAP's existing level of stringency in compliance led to such pre-screening determinism.

Hollow fiber liquid-phase microextraction (HF-LPME) techniques coupled to chromatographic systems have been widely used for extraction and determination of diverse compounds. HF-LPME was able to provide better results in precision, accuracy, selectivity and enrichment factor, in addition to reduction of matrix effect and carry over. It is applicable within a wide pH range and compatible with most analytical instruments which enable the utilization of HF-LPME in a wide variety of applications. This review focused on the modified HF-LPME techniques, efficiency, comparison to other LPME methods and applications.

Food quality and food safety are major challenges affecting agricultural and industrial aspects of production. Many contaminants from different sources contaminate foods and drinks, leading to disastrous health problems like gene mutations and cancer. Previously, many different methods have been used for the analysis of these contaminants. Liquid–liquid extraction (LLE) has been the most well-known conventional technique used, but its limitations are its tediousness, time required, and the use of large quantities of toxic organic solvents. These limitations have led to the search for other, efficient techniques that are more environmentally friendly. Hence, this review highlights recent advances in liquid-phase (single-drop, hollow fiber, and dispersive liquid–liquid) microextraction procedures for food and drink analyses. Such modifications can be justified for solving limitations associated with the traditional LLE method. The objective of this review is to serve as a reference platform for providing effective management tools for solving problems of pollution, clean-up, and control of food quality and safety globally.

This review presents the application of carbon nanotubes as sorbent materials in the analysis of pesticide residues in fruits and vegetables. The advantages, limitations, and challenges of carbon nanotubes, with respect to their use in analytical chemistry, are presented. The efficiency of their application as extraction sorbent materials (in terms of LOD, LOQ, linearity, relative recovery, and RSD) in SPE, solid-phase microextraction, multi-plug filtration clean-up, matrix solid-phase dispersion, and the quick, easy, cheap, effective, rugged and safe method is reported. The synthesis, functionalization, purification, and characterization methods of carbon nanotubes are also discussed.

Mycotoxins are common food contaminants which cause poisoning and severe health risks to humans and animals. The present study applied chemometric approach in liquid chromatography-tandem mass spectrometry (LC-MS/MS) optimization for simultaneous determination of mycotoxins, i.e., aflatoxins B1, B2, G1, and G2, and ochratoxin A. The validated quick, easy, cheap, effective, rugged, and safe (QuEChERS)-LC-MS/MS method was used to study the occurrence of mycotoxins in 120 food matrices. The recovery ranges from 81.94% to 101.67% with relative standard deviation (RSD) lesser than 11%. Through the developed method, aflatoxins were detected in raisin, pistachio, peanut, wheat flour, spice, and chili samples with concentration ranges from 0.45 to 16.93 &micro, g/kg. Trace concentration of ochratoxin A was found in wheat flour and peanut samples which ranged from 1.2 to 3.53 &micro, g/kg. Some of the tested food samples contained mycotoxins of above the European legal maximum limit.

Background: Methamphetamine (MA) and phentermine (PTM) are critical isomeric compounds that often coexist in biological specimen in toxicology cases which have similar nominal mass. The dependency of high-resolution mass spectrometer and special chiral stationary phase column for separation of isomeric compound impedes screening throughput especially in meeting high sampling demand. Aim: In the absence of such equipment for identification, we introduce the flow injection analysis (FIA)-MRM 3 technique and demonstrated its capabilities for quick identification of both isomeric compounds without liquid chromatography (LC) separation through the addition of selectivity criteria in the MRM 3 mode. Method: 20 to 100 ng/mL of MA and PTM, respectively, in whole blood sample (WBS) and dried blood stain (DBS) were used to develop the method for the identification and relative quantification. Twenty whole blood samples which were reported positive of the drugs were randomly selected and were individually stained onto the Flinders Technology Associates (FTA) card for DBS study. Results: The peaks from the two isomeric compounds were successfully discerned for all the tested specimens using the FIA-MRM 3 spectrometry technique. The limit of detection (LOD) and limit of quantification (LOQ) for MA and PTM were comparable to normal liquid chromatography-tandem mass spectrometry runs at 2.23 and 2.07 ng/mL, respectively, for WBS ( n = 30). For DBS, the LOD and LOQ were 3.40 and 2.86 ng/mL, respectively. The accuracy and inter-day precision for DBS and WBS were in the range of 99.97–111.19% and 7.17–9.55%, respectively. Conclusion: These results demonstrated that the technique is highly adoptable in the screening of isomeric compounds of similar masses in a simple and rapid analysis.

A modified hollow-fiber-supported dispersive liquid-liquid microextraction (HF-DLLME) method was developed for the determination of aflatoxins and ochratoxin A in food samples. The various parameters affecting the efficiency of extraction, such as pH, salt addition, extraction time, stirring rate, desorption time, type and volume of extractant and disperser solvents were carefully studied and optimized using two step strategies. The linearity of the evaluated results was 0.1 to 30 μg L−1 for aflatoxins and 0.1 to 20 μg L−1 for ochratoxin A, with regression coefficients (R2) exceeding 0.9990. The precision was satisfactory with relative standard deviation values less than 11%. The method accuracy was within the recommended range from 70% to 120% and analyte accuracy between 83% and 101%. The limits of detection and quantification were in the range from 0.04 to 0.06 μg L−1 and 0.08 to 0.13 μg L−1, respectively, for multi-aflatoxins, and 0.02 to 0.04 µg L−1 and 0.08 to 0.10 µg L−1, respectively, for ochratoxin A. The developed method was successfully applied for the determination of mycotoxins in food samples.

A novel mass spectrometry detection technique based on a multi-period and multi- experiment (MRM-EPI-MRM3) with library matching in a single run for fast and rapid screening and identification of amphetamine type stimulants (ATS) related drugs in whole blood, urine and dried blood stain was developed and validated. The ATS-related drugs analyzed in this study include ephedrine, pseudoephedrine, amphetamine, methamphetamine, MDMA (3,4-Methylenedioxymethamphetamine), MDA (3,4-Methylenedioxyamphetamine), MDEA (3,4-Methylenedioxy-N-ethylamphetamine) and phentermine. The relative standard deviation for inter and intraday was less than 15% while recoveries ranged from 80% to 120% for all three matrices, i.e., whole blood, urine and dried blood stain. All compounds gave library matching percentage of more than 85% based on the purity. This method was proven to be simple and robust, and provide high confident results complemented with library matching confirmation.

Sample preparation has been identified as the most important step in analytical chemistry and has been tagged as the bottleneck of analytical methodology. The current trend is aimed at developing cost-effective, miniaturized, simplified, and environmentally friendly sample preparation techniques. The fundamentals and applications of multivariate statistical techniques for the optimization of microextraction sample preparation and chromatographic analysis of pesticide residues are described in this review. The use of Placket-Burman, Doehlert matrix, and Box-Behnken designs are discussed. As observed in this review, a number of analytical chemists have combined chemometrics and microextraction techniques, which has helped to streamline sample preparation and improve sample throughput.

Solid-phase microextraction (SPME) is a solvent-less sample preparation method which combines sample preparation, isolation, concentration and enrichment into one step. In this study, multivariate strategy was used to determine the significance of the factors affecting the solid phase microextraction of pesticide residues (fenobucarb, diazinon, chlorothalonil and chlorpyrifos) using a randomised factorial design. The interactions and effects of temperature, time and salt addition on the efficiency of the extraction of the pesticide residues were evaluated using 2(3) factorial designs. The analytes were extracted with 100 μm PDMS fibres according to the factorial design matrix and desorbed into a gas chromatography-mass spectrometry detector. The developed method was applied for the analysis of apple samples and the limits of detection were between 0.01 and 0.2 μg kg(-)(1), which were lower than the MRLs for apples. The relative standard deviations (RSD) were between 0.1% and 13.37% with average recovery of 80-105%. The linearity ranges from 0.5-50 μg kg(-)(1) with correlation coefficient greater than 0.99.

A method for the analysis of aflatoxins in food samples was developed. The preliminary work focused on optimizing sample pretreatment conditions such as the extraction solvent; the type and amount of drying agents; the extraction time; and the solvent-sample ratio. A 60:40 methanol/acetonitrile (%, v/v) extraction mixture provided recoveries in the range of 71.8–107.7% at spike levels of 1.5–50.0 µg/kg with relative standard deviations (RSDs) lower than 15%. The separation of the four aflatoxin compounds with high selectivity and sensitivity, and within reasonable retention times, was performed by a C18 250 mm × 4.6 mm × 5 µm column (Nucleodur 250-5) at 45°C. The developed QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure, high performance liquid chromatography (HPLC) method was then compared with the fluorometric determination method. It was found that the fluorometric determination method had a poor precision and positive bias as compared to QuEChERS-HPLC method. A total of 669 domest...

This paper describes the steps involved in harmonizing a statistical method for the classification of illicit heroin using manufacturing impurity data. Sixteen linked samples were prepared from each of the five unrelated heroin seizures. Five links, totaling 80 samples were subjected to two sample weight approaches for liquid–liquid extraction. A wide range of intra-batch variations were observed in the dataset and this was probably due to the poor extraction efficiency and weight differences. Notwithstanding this, this paper aims to find the best clustering technique (pretreatment and clustering tool) that is able to minimize the intra-batch variation without undermining the inter-batch variation for sample classification. Three pretreatment methods were first evaluated by principle component analysis (PCA) and normalization coupled with standardization was found to be able to show promising results. Subsequently, hierarchical cluster analysis (HCA) was chosen to evaluate the pretreated data as this tech...

A rapid, reliable and confirmatory method has been developed to determine the levels of aflatoxins B1, B2, G1, and G2 in barley, wheat, soybean, corn, peanut and peanut butter. The method is based on a single extraction step followed by liquid chromatography coupled with electrospray ionization quadrupole time of flight mass spectrometry (LC-ESI-QTOF-MS/MS). The extraction, dilution, chromatographic and MS conditions were optimized in order to increase the sample throughput and sensitivity. The quantification of the analytes was measured by performing low-energy collision induced tandem mass spectrometry (CID-MS/MS) using the product ion scan mode. The calibration curves were linear over the range from 0.195 to 50.000 μg/kg for aflatoxin B1, G1 and from 0.029 to 15.000 μg/kg for aflatoxin B2, G2. The correlation coefficients (r2) were higher than 0.998. The overall recoveries for aflatoxins were in the range of 57.1–108.7% at spike levels of 0.6–15.0 μg/kg with relative standard deviations lower than 16%. The limit of quantification (LOQ) for aflatoxins is less than 0.8 μg/kg.

Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tert-butylhydroquinone (TBHQ) are synthetic antioxidants used in the food industry. Herein, we describe the development of a novel graphite nanocomposite-based electrochemical sensor for the multiplex detection and measurement of BHA, BHT, and TBHQ levels in complex food samples using a linear sweep voltammetry technique. Moreover, our newly established analytical method exhibited good sensitivity, limit of detection, limit of quantitation, and selectivity. The accuracy and reliability of analytical results were challenged by method validation and comparison with the results of the liquid chromatography method, where a linear correlation of more than 0.99 was achieved. The addition of sodium dodecyl sulfate as supporting additive further enhanced the LSV response (anodic peak current, Ipa) of BHA and BHT by 2- and 20-times, respectively.

Fruits and vegetables constitute a major type of food consumed daily apart from whole grains. Unfortunately, the residual deposits of pesticides in these products are becoming a major health concern for human consumption. Consequently, the outcome of the long-term accumulation of pesticide residues has posed many health issues to both humans and animals in the environment. However, the residues have previously been determined using conventionally known techniques, which include liquid-liquid extraction, solid-phase extraction (SPE) and the recently used liquid-phase microextraction techniques. Despite the positive technological effects of these methods, their limitations include; time-consuming, operational difficulty, use of toxic organic solvents, low selective property and expensive extraction setups, with shorter lifespan of instrumental performances. Thus, the potential and maximum use of these methods for pesticides residue determination has resulted in the urgent need for better techniques that will overcome the highlighted drawbacks. Alternatively, attention has been drawn recently towards the use of quick, easy, cheap, effective, rugged and safe technique (QuEChERS) coupled with dispersive solid-phase extraction (dSPE) to overcome the setback challenges experienced by the previous technologies. Conclusively, the reviewed QuEChERS-dSPE techniques and the recent cleanup modifications justifiably prove to be reliable for routine determination and monitoring the concentration levels of pesticide residues using advanced instruments such as high-performance liquid chromatography, liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry.

The sample preparation step has been identified as the bottleneck of analytical methodology in chemical analysis. Therefore, there is need for the development of cost-effective, easy to operate, and environmentally friendly miniaturized sample preparation technique. The microextraction techniques combine extraction, isolation, concentration, and introduction of analytes into analytical instrument, to a single and uninterrupted step, and improve sample throughput. The use of liquid-phase microextraction techniques for the analysis of pesticide residues in fruits and vegetables are discussed with the focus on the methodologies employed by different researchers and their analytical performances. Analytes are extracted using water-immiscible solvents and are desorbed into gas chromatography, liquid chromatography, or capillary electrophoresis for identification and quantitation.

The high number of illicit heroin cases in Malaysia has led to the local forensic laboratory profiling of the physical and chemical characteristics of 311 street samples submitted as heroin cases in 2010. Visual examination and physical characteristics of the heroin substance and plastic packages are described. The preferred ranges of the weight of substances per package and the dimensions of the plastic package/receptacle are defined. Analysis of eight major components (three adulterants and five opium alkaloids) is also detailed. It was found that most samples contained less than 10% heroin base and more than 80% caffeine. Physical and chemical data together provide a quick overview of the samples seized within the country. Principal component analysis of the five major opium alkaloids present in the seized samples suggested that there were at least two sources responsible for the samples analyzed.

Statistical validation is crucial for the clustering of unknown samples. This study aims to demonstrate how statistical techniques can be optimized using simulated heroin samples containing a range of analyte concentrations that are similar to those of the case samples. Eight simulated heroin distribution links consisting of 64 postcut samples were prepared by mixing one of two mixtures of paracetamol-caffeine-dextromethorphan at different proportions with eight precut samples. Analyte contents and compositional variation of the prepared samples were investigated. A number of data pretreatments were evaluated by associating the postcut samples with the corresponding precut samples using principal component analysis and discriminant analysis. Subsequently, combinations of seven linkage methods and five distance measures were explored using hierarchical cluster analysis. In this study, Ward-Manhattan showed better distinctions between unrelated links and was able to cluster all related samples in very close distance under the known links on a dendogram. A similar discriminative outcome was also achieved by 90 unknown case samples when clustered via Ward-Manhattan. Language: en

This paper seeks to evaluate whether the chemical profiling data obtained with a constant weight approach can be used in the classification of highly cut heroin samples. A constant weight of a seized substance instead of the conventional weight equivalent to 15 mg heroin base was used to profile the manufacturing impurities. The study attempts to optimize four clustering tools using 12 impurity peaks extracted from the heroin samples (

As far as illicit drugs are concerned, drug profiling utilizing various analytical methods to trace the origin, manufacturing process and distribution chain is a key element in forensic intelligence. Setting aside the practical use of drug profiles, forensic laboratory findings with close reference to that of illicit heroin could also provide metaphyiscal insights about the nature of such intelligence work. The metaphysical nature, if appreciated, provides grounds for further scientific hypotheses that can be validated by logic and observation. Thus, both forensic science and metaphysics adopt an important role in forensic drug intelligence. Hence, it is worth examining the underlying metaphysical nature that governs the intelligence work through forensic science in the effort to counteract drug trafficking. Metaphysical explanations relating to the scientific evidence of drug profiling are integrated in this review, which focuses on the basic notion, law of identity, causality, necessity and holarchy, al...

This paper reviews the application of various modes of solid-phase microextraction (SPME) for the analysis of pesticide residues in fruits and vegetables. SPME is a simple extraction technique that eliminates the use of solvent, and it is applied for the analysis of both volatile and nonvolatile pesticides. SPME has been successfully coupled to both GC and LC. The coupling with GC has been straightforward and requires little modification of existing equipment, but interfacing with LC has proved challenging. The external standard calibration technique is widely used for quantification, while standard addition and internal or surrogate standards are mainly used to account for matrix effects. All parameters that affect the extraction of pesticide residues from fruits and vegetables, and therefore need to be optimized, are also reviewed. Details of the characteristics of analytical procedures and new trends in fiber production using sol-gel technology and molecularly imprinted polymers are discussed.

A new method based on Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) technique followed by liquid chromatography coupled with electrospray ionization quadrupole time of flight mass spectrometry (LC-ESI-QTOF-MS/MS) was developed for the determination of eight(8) type-A and type-B trichothecenes in cereal samples. The quantification of the analytes was measured by performing low-energy collision induced tandem mass spectrometry (CID-MS/MS) using the multiple reaction monitoring (MRM) mode. This method excludes the use of dispersive solid-phase extraction (dSPE) extraction cleanup step to reduce time and cost of analysis. Type-A trichothecenes were ionized in the positive ion mode and type-B trichothecenes in the negative ion mode. The recoveries of fortified cereal samples ranged from 61.9% to 110.9%, and the relative standard deviations (RSDs) were lower than the acceptable 12% in all the cases. The detection limits (S/N = 3) of type-A and type-B trichothecenes were 6.1–8.3 and 12.5–18.7 µg/kg,...

This study aims to utilize the manufacturing impurities found in illicit heroin to predict whether the samples had originated from a common production batch. From highly cut heroin samples, twelve frequently extractable neutral/acidic impurities were selected for investigation. A gas chromatographic method was optimized using three locally seized samples containing the target impurities and a control sample consisting of n-alkanes. The method optimization procedures are reported in detail. The capability of the optimized method was further assessed using five simulated links prepared from unrelated heroin seizures. With the aid of principal component analysis (PCA), it was found that the statistical data pretreatment (normalization followed by standardization, N + S) showed promising results for sample classification using profiles obtained with the optimized method. Similarly, 252 street doses of highly cut samples were analyzed and the profiles were statistically decomposed by PCA after the N + S pretre...

The analysis of the trace elements present in the street doses of heroin has currently been undertaken with a dual aim: to estimate the elemental compositions and to cluster the case samples. Inductively coupled plasma-mass spectrometry was optimized to quantify 18 trace elements simultaneously. The method presented high repeatability and reproducibility for the target elements. The linear concentration ranges achieved linearity with r2 > 0.9975. The limits of detection (LOD) were sufficiently low for almost all the elements except for Ca (LOD = 100 ppb). The limit of quantification (LOQ) for each element was also found acceptable. All target elements show mean recoveries between 92%–108%. Other major findings of this study including intra-sample (RSD

Food samples are usually analyzed with a preliminary step of sample preparation, because pesticide residues are present in low concentrations and embedded in complex matrixes. Solid phase microextraction (SPME) is a solvent-free extraction technique that is fast, relatively inexpensive, easily automated, and versatile with high sample throughput. Analyte extraction, pre-concentration, and introduction into the analytical instrument are achieved in a single uninterrupted process. SPME uses fibers coated with a polymeric stationary phase that can be either a solid, liquid, or a combination of both. The fiber coating extracts the target analytes from a complex food matrix by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred into the analytical instrument for desorption and analysis of the target analytes. The use of sol-gel technology in the production SPME coated fiber has helped to increase the range of pesticide residues that can be e...

A new method for the determination and analysis of aflatoxins in noodles, based on the use of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure, enhanced with a high performance liquid chromatography–coupled to a fluorescence detector (HPLC–FLD) has been developed. The method excludes the use of dispersive solid-phase extraction (dSPE) extraction cleanup step to reduce time and cost of analysis. Separation of the four(4) aflatoxins with higher selectivity and sensitivity, and within reasonable limits of retention time, was performed by using an isocratic mobile phase of water/methanol/acetonitrile (65/25/10) at a column temperature of 30 °C. Optimization of sample preparation and analytical conditions gave recoveries in the range of 75%–107% at spike levels of 5.0–20.0 μg/kg, and relative standard deviations (RSDs) lower than 13% in all the cases. The repeatability and reproducibility results were in range of 2.0–12.3% and 3.4–16.5% respectively. Additionally, the limits of detection (LOD) (0.01–1.00 μg/kg) and the limits of quantification (LOQ) (0.05–1.80 μg/kg) of these aflatoxins are well within the legal limits set by the European Union (EU).

Plastic packaging is one of the most commonly used methods among illicit heroin packers. Distribution starting from the manufacturer to the end users may involve replacement of larger plastic bags with smaller packets as the mass of heroin is divided into smaller portions for street sales. Conventionally, polymeric compositions of these materials are often used qualitatively to distinguish between the types of plastic packets the drug dis- tributors tend to use. In addition, spectral differences when statistically manipulated can also help further differentiate the plastic packets of a parti- cular type. In this study, the IR technique has identified five polymeric types at the macro level from 311 heroin cases involving the use of plastic packages. The most frequently encountered Type 1-Polypropylene-based plastic packets were further distinguished at the micro level by principal component analysis after IR data pretreatment. Possible forensic interpreta- tions about the packers involved in heroin cases were also outlined based on the findings obtained at the two levels. Using IR technique alone is the preliminary step in forensic profiling. Further analysis of other aspects asso- ciated with these packages is required for more precise intelligence work.

Background:Methamphetamine (MA) and phentermine (PTM) are critical isomeric compounds that often coexist in biological specimen in toxicology cases which have similar nominal mass. The dependency o...

Headspace solid-phase microextraction (HS-SPME) was evaluated for the determination of pesticide residues in fruits and vegetables by gas chromatography with an electron capture detector (GC-ECD). The fibre used was coated with polydimethylsiloxane (100 μm thickness) and the analytical conditions employed have been developed and optimised in a previous work [Chai, M. K., Tan, G. H., & Asha, L. (2008). Optimisation of headspace solid-phase microextraction for the determination of pesticide residues in vegetables and fruits. Analytical Sciences, 24 (2), 273–276]. The results show that the HS-SPME procedure gave a better linear range, accuracy, precision, detection and quantification limits and is adequate for analysing pesticide residues in fruits and vegetables. The average recoveries obtained for each pesticide ranged between 71% and 98% at three fortification levels with the relative standard deviation of less than 5%. Repeatability (0.3–3.7%) and intermediate precision (0.8–2.5%) were shown to be satisfactory. The limits of detection (0.01–1 μg L −1 ) and the limits of quantification (0.05–5 μg L −1 ) of these pesticides were much lower than the maximum residue levels (MRL), allowed for fruits and vegetables in Malaysia.

Four tetracyclic oxindole alkaloids, 7(R)- and 7(S)-geissoschizol oxindole (1 and 2), 7(R),16(R)- and 7(S),16(R)-19(E)-isositsirikine oxindole (3 and 4), in addition to a taberpsychine derivative, N(4)-demethyltaberpsychine (5), were isolated from the Malayan Tabernaemontana corymbosa and the structures were established using NMR and MS analysis.

Two new indole alkaloids, 12-methoxykopsine (6) and danuphylline B (7), were obtained from the leaf extract of the Malayan Kopsia species, K. arborea, and their structures established by spectroscopic analysis. An electrochemically-mediated partial synthesis of the ring-opened alkaloid, danuphylline B from the hexacyclic alkaloid, methyl N(1)-de(methoxycarbonyl)chanofruticosinate was carried out.

A headspace solid-phase microextraction method has been developed for the determination of 8 pesticides in vegetables and fruits by using gas chromatography with an electron capture detector. Two types of fibers (polyacrylate, 85 microm and polydimethylsiloxane, 100 microm) have been assayed and compared. The main factors: extraction and desorption parameters, ionic strength, and the effects of dilution and organic solvents, were studied and optimized. The optimized procedures resulted in more than 80% recovery for all the investigated vegetable and fruit samples with RSD values below 10%.

The reaction of [CpMo(CO)3]2 (1) with a molar equivalent of Bz2S3 at 60 °C for 3.5 h has led to the isolation of [CpMo(CO)2(SBz)]2 (2), [CpMo(CO)(SBz)]2S (3) and [CpMo(SBz)S]2 (4) in 16.9%, 3.1% and 61.1% yields, respectively, as main products. Thermolytic studies showed that 2 underwent stepwise decarbonylation to give 3 and 4. All the three products of 2, 3 and 4 were thiolato-bridged dimolybdenum complexes with bond orders of zero, one and two for 2, 3 and 4, respectively. In addition, both 3 and 4 have one and two S atoms bridged in a μ–η2-mode, respectively. The structures of 2 and 3 have been reported previously. The totally decarbonylated 4 was isolated as polymorphs, 4a and 4b, which have been characterized by elemental, spectral analyses and structurally determined.

Graphite material is abundantly available from recyclable sources. It possesses a good electrical conductance property, which makes it an attractive material as a working electrode. However, due to a high activation overpotential it has limited applications as compared to other solid metal electrodes. In this present work, we obtained a graphite rod from a used battery, and carried out electrochemical improvements by electro-deposition with gold nanoparticles (AuNPs). The heterogeneous electron transfer rate and electron transfer resistance of the fabricated electrode were improved. The electrode overpotential has shown improvement by 50 mV, and the effective surface area has increased by 2 fold. To determine the practicability of the AuNPs/graphite electrode, we used the electrode in the analysis of myricetin. A square-wave voltammetry was used in the analysis, and the detection response increased by 2.5 fold, which suggested an improvement in the electrode sensitivity.

The reaction of [CpCr(CO)3]2 (Cp = η5-C5H5) (1) with an equivalent of Bz2S3 at ambient temperature gave [CpCr(CO)2]2S (3) [L.Y. Goh, T.W. Hambley, G.B. Robertson, Organometallics 6 (1987) 1051], novel complexes of [CpCr(CO)2(SBz)]2 (4) and together with [CpCr(SBz)]2S (5) as main products. Thermolytic studies showed that 4 underwent complete decarbonylation to give [CpCr(SBz)]2S (5). Final thermal decomposition of 3 and 5 eventually yielded Cp4Cr4S4 (6) (Goh et al., 1987) after prolonged reaction at 100 °C. However, the reaction of [CpCr(CO)2]2 (Cr Cr) (2) with Bz2S3 was much slower at ambient temperature which required 72 h to complete eventually yielding 3 and 5. All the products have been characterized by elemental and spectral analyses. 4 has been structurally determined.

The various microextraction techniques have been developed in order to reduce sample preparation time, improve sensitivity and selectivity as well as to corroborate the recent advances in the development of highly sensitive and efficient analytical instrumentation. The current trend is aimed at the simplification and miniaturization of extraction steps, which has led to the combination of multi-step extraction and analytical analysis into single uninterrupted step. The method development involves the screening and subsequent optimization of both gas chromatography-mass spectrometry (GC-MS) and solid phase microextraction (SPME) parameters using multivariate experimental design, which has been shown to be efficient and effective with little experimental runs. The use of microextraction has been very effective in the analysis of contaminants in food, water and the environments to ensure they are safe and does not pose any health risk to human.

The need to analyze multi pesticide residues continues to be imperative and applying a suitable experimental design remains the core to achieving a comprehensive chemical analysis. The pretreatment of a sample has been found to be the most important rate-determining step as it affects the instrumental process and data analysis. The use of the SPME technique coupled with GC-MS to determine multi-residue pesticides is found to be applicable in environmental, pharmaceutical, food, clinical, forensic samples in three modes (DI-SPME, HS-SPME and MD-SPME). This has gained much recognition due to its advantage over the classical or previous sample pretreatment methods such as SPE, LLE, LDME, HFME and DLME. Before applying SPME coupled to a GC-MS detector, several conditions need to be met in order to accomplish enhanced extraction rate, efficiency and sensitivity of experimental procedures. The large numbers of data sets obtained with the advent of various instrumental techniques can be analyzed speedily by applying chemometric methods to screen the various parameters affecting the calibration methods by statistical application so as to achieve the best optimization of the experiment. This review aims at looking at the different chemometric methods for multivariate parameter optimization in experimental design for the analysis of pesticide residues in water.

A combination of alumina column chromatography and GC procedures was developed for the determination of synthetic hydrocarbon-based thermal heating fluid (trademarked as Therminol 55™) in vegetable oils. In each run, 3 g of sample solution was loaded onto the alumina (50 g) column and was eluted with 200 mL hexane. The eluate was then concentrated to 1 mL with the aid of a nitrogen stream prior to GC analysis. The GC chromatogram of the thermal heating fluid was characterized by the presence of a bell-shaped hump that could not be resolved into individual peaks. The lowest detection limit based on various spiked palm olein samples was 20 μg/g. The CV obtained were 6.5–8.9% for the intra-day study and 8.1–9.7% for the inter-day study. Overall recoveries of these samples ranged from 68.0 to 85.7% and the method was found to be good enough for quality control purposes.

Solid-phase microextraction (SPME) is a solventless sample preparation method that combines sample preparation, isolation, concentration, and enrichment into one step. A simple and effective method coupling headspace-SPME to GC/MS was developed for the analysis of chlorpyrifos, fenitrothion, endosulfan I, and endosulfan II pesticide residues in cocoa powder. In this study, multivariate strategy was used to determine the significance of the factors affecting the SPME of the pesticides using a Plackett-Burman design, and the significant factors were optimized using central composite design. The analytes were extracted with 100 μm polydimethylsiloxane fibers according to the factorial design matrix and desorbed into a GC/MS instrument. The developed method was applied for the analysis of a cocoa powder sample, and it exhibited good figures of merit for the analytical methodology. Using the optimized conditions, the linearity ranged from 2.5 to 500 μg/kg (R2 > 0.99) using an internal standard calibration method, and the average recoveries were between 75 and 95%, with RSD values between 3.8 and 9.7%.

A simple and reliable high-performance liquid chromatography method for the analysis of diesel oil in contaminated edible oils is described. Analysis performed using a diol column with a mobile phase of heptane and isopropanol (94∶6, vol/vol). Although baseline separation between diesel and other background fluorescent components was not achieved, quantitation was still possible using baseline integration. The method is linear over the range of 5–1000 μg/g with a correlation coefficient (r2) of 0.9984. Average recoveries from spiked edible oils were 94.4–101.3%, with a limit of quantitation (LOQ) of 5 μg/g for sunflower oil, palm olein, and groundnut oil. Corn oil has a higher content of ester components, thus, LOQ was slightly worse (40 μg/g). The applicability of the method was confirmed by gas chromatography-mass spectroscopic detection to show the presence of diesel hydrocarbons in the suspected contaminated crude palm oil. This procedure provides a simple and sensitive method for determining diesel oil concentration in contaminated edible oils without prior sample cleanup or extraction.

Anodic oxidation of kopsamine on platinum in acetonitrile results in cyanation or cyanomethylation, following ring closure, while oxidation on vitreous carbon in methanol yields a dimerization product with a C2 element of symmetry. This behaviour is reproduced in the aromatic congeners of kopsamine, kopsiflorine and 11-methoxykopsilongine. Oxidation of kopsingine on platinum in CH2Cl2–MeCN leads to a stable conjugated iminium salt which can be trapped by alcohol or water nucleophiles to give kopsidines A, B, and C. Kopsidines A and B can also be obtained directly from electrooxidation in methanol or ethanol. Oxidation of dihydrokopsingine in acetonitrile gives the 17-to-5 and 17-to-3 oxo-bridged compounds directly, while oxidation in methanol yields an additional product which is a caged kopsinitarine derivative. Oxidation of an aspidofractinine derivative without unsaturation in the piperidine ring and with a C(17)-αOH function gives a C2 symmetric dimerization product as well as a caged kopsinitarine-type product. Possible pathways leading to the various products are presented.