Evaluating the blank contamination and recovery of sample pretreatment procedures for analyzing organophosphorus flame retardants in waters

Organophosphate esters（OPEs）, used as flame retardants and plasticizers, are widely present in environmental waters. Development of accurate determination methods for trace OPEs in water is urgent for understanding the fate and risk of this class of emerging pollutants. However, the wide use of OPEs in experimental materials results in blank interference, which influences the accuracy of analytical results. In the present work, blank contamination and recovery of pretreatment procedures for analysis of OPEs in water samples were systematically examined for the first time. Blank contaminations were observed in filtration membranes, glass bottles, solid phase extraction cartridges, and nitrogen blowing instruments. These contaminations could be as high as 6.4–64 ng/L per treatment. Different kinds of membranes were compared in terms of contamination levels left after common glassware cleaning, and a special wash procedure was proposed to eliminate the contamination from membranes. Meanwhile, adsorption of highly hydrophobic OPEs on the inside wall of glass bottles was found to be 42.4%–86.1%, which was the primary cause of low recoveries and was significantly reduced by an additional washing step with acetonitrile. This work is expected to provide guidelines for the establishment of analysis methods for OPEs in aqueous samples.

On-site rapid detection of multiple pesticide residues in tea leaves by lateral flow immunoassay

The application of pesticides (mostly insecticides and fungicides) during the tea-planting process will undoubtedly increase the dietary risk associated with drinking tea. Thus, it is necessary to ascertain whether pesticide residues in tea products exceed the maximum residue limits. However, the complex matrices present in tea samples comprise a major challenge in the analytical detection of pesticide residues. In this study, nine types of lateral flow immunochromatographic strips (LFICSs) were developed to detect the pesticides of interest (fenpropathrin, chlorpyrifos, imidacloprid, thiamethoxam, acetamiprid, carbendazim, chlorothalonil, pyraclostrobin, and iprodione). To reduce the interference of tea substrates on the assay sensitivity, the pretreatment conditions for tea samples, including the extraction solvent, extraction time, and purification agent, were optimized for the simultaneous detection of these pesticides. The entire testing procedure (including pretreatment and detection) could be completed within 30 min. The detected results of authentic tea samples were confirmed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), which suggest that the LFICS coupled with sample rapid pretreatment can be used for on-site rapid screening of the target pesticide in tea products prior to their market release.

Development of an accurate lateral flow immunoassay for PEDV detection in swine fecal samples with a filter pad design

Porcine epidemic diarrhea virus(PEDV),as the main causative pathogen of viral diarrhea in pigs,has been reported to result in high morbidity and mortality in neonatal piglets and cause significant economic losses to the swine industry.Rapid diagnosis methods are essential for preventing outbreaks and transmission of this disease.In this study,a paper-based lateral flow immunoassay for the rapid diagnosis of PEDV in swine fecal samples was developed using stable color-rich latex beads as the label.Under optimal conditions,the newly developed latex bead-based lateral flow immunoassay(LBs-LFIA)attained a limit of detection(LOD)as low as 10^(3.60) TCID_(50)/mL and no cross-reactivity with other related swine viruses.To solve swine feces impurity interference,by adding a filtration unit design of LFIA without an additional pretreatment procedure,the LBs-LFIA gave good agreement(92.59%)with RT-PCR results in the analysis of clinical swine fecal samples{n=108),which was more accurate than previously reported colloidal gold LFIA(74.07%)and fluorescent LFIA(86.67%).Moreover,LBs-LFIA showed sufficient accuracy(coefficient of variance[CV]<15%)and stable(room temperature storage life>56 days)performance for PEDV detection,which is promising for on-site analysis and user-driven testing in pig production system.

Determination of haloacetic acids in hospital effuent after chlorination by ion chromatography

The ion chromatography combined solid phase extraction （SPE） method was developed for the analysis of low concentration haloacetic acids （HAAs）, a class of disinfection by-products formed from chlorination of hospital wastewater. The monitored HAAs included monochloroacetic acid, monobromoacetic acid, dichloroacetic acid, dibromoacetic acid and trichloroacetic acid. The method employed a sodium hydroxide eluent at a flow rate of 0.8 ml/min, electrolytically generated gradients, and suppressed conductivity detection. To analyze the HAAs in real hospital wastewater samples, C18 pretreatment cartridge was utilized to reduce samples＇ turbidity. Preconcentration with SPE and matrix elimination with treatment cartridges were investigated and found to be able to obtain acceptable detection limits. Linearity, repeatability and detection limits of the above method were evaluated. The detection limits of monobromoacetic acid and dibromoacetic acid were 2.61 μg/L and 1.30 μg/L, respectively, and the other three acids are ranging from 0.48 to 0.82μg/L under 25-fold preconcentration. When the above optimization procedure was applied to three hospital wastewater samples with different treatment processes in Tianjin, it was found that the dichloroacetic acid was the major compound, and the growth ratios of the HAAs after disinfection by sodium hypochlorite were 91.28%, 63.61% and 79.50%, respectively.

New techniques of on-line biological sample processing and their application in the field of biopharmaceutical analysis

Biological sample pretreatment is an important step in biological sample analysis. Due to the diversity of biological matrices, the analysis of target substances in these samples presents significant challenges to sample processing. To meet these emerging demands on biopharmaceutical analysis, this paper summarizes several new techniques of on-line biological sample processing: solid phase extraction, solid phase micro-extraction, column switching, limited intake filler, molecularly imprinted solid phase extraction, tubular column, and micro-dialysis. We describe new developments, principles, and characteristics of these techniques, and the application of liquid chromatography mass spectrometry (LC MS) in biopharmaceutical analysis with these new techniques in on-line biological sample processing. (C) 2016 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND

Quantitative extraction of chromium Ⅵ and Ⅲ from tanned leather: a comparative study of pretreatment methods

In this study,seven pretreatment methods for chromium speciation in tanned leather were evaluated:acidic miner‑alization,ethylenediaminetetraacetic acid(EDTA)extraction,diethylenetriaminepentaacetic acid(DTPA)extraction,alkaline extraction(NH 4 OH),ammonium nitrate extraction(NH 4 NO 3),water extraction,and phosphate buffer extrac‑tion.Acidic mineralization permitted the decomposition of the organic matter and ensured the complete digestion of leathers,giving access to the total content of chromium in each sample using inductively coupled plasma‑atomic emission spectrometry(ICP‑AES).From all the extractant media tested,EDTA proved to be the most efficient,allowing the extraction of Cr(VI)and Cr(III)as a Cr(III)‑EDTA complex,quantitatively.Method validation is presented for EDTA extraction and direct mineralization.For the EDTA extraction,method detection limit(MDL)and method quantifica‑tion limit(MQL)for total Cr in leather were 3.4 ppb and 11.2 ppb(µg of total Cr per L of extraction solution),respec‑tively.Due to the lack of leather certified reference materials(CRMs)for Cr(VI),accuracy was evaluated by spiking leather samples with a Cr(VI)solution.The spike recovery of EDTA microwave assisted extraction ranged from 91.0 to 108.6%.Interday precision was also evaluated and all variation coefficients were below 5%,for both mineralization and EDTA extraction.This article provides an efficient procedure to extract quantitatively chromium from leather,while maintaining the speciation,which can be further followed by ion chromatography‑inductively coupled plasma‑mass spectrometry(IC‑ICP‑MS).

The application of immunoassay in bioanalysis

Immunoassay technology is an analytical method with high sensitivity and specificity; it provides a technique to assay materials which cannot be measured by other methods, or are difficult to detect. It plays a very important role in biological sample pre-treatment, therapeutic drug monitoring and drug determination, and is one of the important means for in vivo drug analyses. This paper reviews immunoassays commonly used in bioanalysis, including immunoextraction and immunodepletion for pretreatment of biological samples, conventional immunoassay methods and new immunoassay technologies for determination of target drugs.

Simultaneous determination of free methamphetamine,pethidine,ketamine and tramadol in urine by dispersive liquid–liquid microextraction combined with GC–MS

A simple and rapid dispersive liquid–liquid microextraction(DLLME)technique coupled with gas chromatography–ion trap mass spectrometry(GC–MS)was developed for the extraction and analysis of methamphetamine(MA),pethidine(PD),ketamine(KT)and tramadol(TD)from human urine.In this study,different parameters affecting the extraction process such as the type and volume of extraction solvent,type and volume of disperser solvent,extraction time and pH value and salt effect were studied and optimized.Under optimized conditions,the enrichment factor ranged from 185 to 226 and the average recovery ranged from 80.45%to 95.55%.The linear range was 10.0–1000.0 mg/L,the limit of detection and quantitation were in the range 0.43–1.96 mg/L and 1.44–6.53 mg/L,respectively.The relative standard deviations were in the range 1.98%–3.90%(n=7).The obtained results show that DLLME combined with GC–MS is a fast and simple method for the determination of MA,PD,KT and TD in human urine.

An Improved Method of Laser Particle Size Analysis and Its Applications in Identification of Lacustrine Tempestite and Beach Bar：An Example from the Dongying Depression

Grain size analysis is a common method in the study of sedimentology. For the consolidated sedimentary rocks, the traditional methods are rock slice observation and image analysis. In recent years, laser particle size analyzer is used widely in particle size analysis of sedimentary rock. Unlike the pretreatment of loose samples, the rock samples must be crushed, added acid to wipe out cement, and washed. However, in the step of washing, most of the fines component（less than 63 μm） in the suspended state should be inevitably lost. It will significantly affect the accuracy of particle size analysis, especially for siltstone. This paper presents a siltstone sample pretreatment method which core step is washing acid by centrifuge. Compared with traditional decantation method, the results show that the median particle size reduced 33.2 μm on average. Compared with the precipitation method which is commonly used for handling loose samples, the change of solid-liquid separation time is from 12 h to 10 min, while the average reduction of median particle size is about 15 μm. The grain size value corresponded to the cumulative volume of 10%/90% reduced 2.5 μm/20.3 μm on average. The percentage of the clay component less than 2 μm increased 2.88% on average. The fine particle（2–4 μm） and silt component（4–63 μm） increased 1.71% and 5.56% on average. Based on this method, two kinds of similar lacustrine siltstone were analyzed. They are tempestite and beach bar which are difficult to identify in the Lijin sub-depression, Dongying depression, Shengli oilfield, China. The final grain-size probability plot of tempestite is the type of “one saltation component and three suspension components”. The content of suspension components can reach to 80%–90%. The beach bar is the type of “one saltation component and two suspension components”. The content of suspension components can reach to 40%–45%. They both have the characteristics of high slope which means well sorting. But they can be distinguished based on the suspension sedimentary characteristics which were preserved by maximum degree in this kind of sample pretreatment method.

Facile preparation of nano-g-C_(3)N_(4)/UiO-66-NH_(2) composite as sorbent for high-efficient extraction and preconcentration of food colorants prior to HPLC analysis

In this work,the nano-g-C_(3)N_(4)/Ui O-66-NH_(2)composite was prepared by one-step solvothermal method.The as-prepared composite was characterized by scanning electron microscopy,Brunner-Emmet-Teller measurement,energy dispersive spectrometer,X-ray diffraction,and Fourier transform infrared spectroscopy.By using nano-g-C_(3)N_(4)/Ui O-66-NH_(2)composite as sorbent,a dispersive solid-phase extraction coupled with high-performance liquid chromatography was developed to sensitive analysis of food colorants including tartrazine,amaranth,carmine,sunset yellow,allura red and bright blue.The experiment parameters including the amount of sorbent,adsorption time,the p H of adsorption solution,desorption time,desorption solvent,the p H of desorption solution as well as the proportion between desorption solvent and buffer solvent were investigated.Under the optimized conditions,the limits of detection(S/N=3) and limits of quantitation (S/N=10) were determined in the ranges of 0.08-0.8 and 0.2-2.0 ng/m L,respectively.With the developed sample pretreatment method,carmine and brilliant blue were determined from blueberry juice by HPLC-DAD.The contents were calculated as 1.53μg/m L and0.17μg/mL,respectively.

Recent developments in the detection of melamine

In recent years,there were two reported outbreaks of food borne illness associated with melamine.The presence of melamine and its related compounds in milk,feed,and other foods has resulted in the need for reliable methods for the detection and accurate quantification of this class of contaminants.The sample pretreatment for melamine in a complex matrix usually involves a liquid extraction by a polar solvent,followed by a further clean-up with solid phase extraction.Analyses of melamine and related compounds are commonly carried out by liquid or gas chromatographic methods conjugated with mass spectrometry.Other innovative screening methods,which use antibodies,molecularly imprinted polymers,capillary electrophoresis,and gold nanoparticles,are also used to develop assays and biosensors to melamine.However,many of these methods have been hindered by matrix effects,the solubility of melamine-cyanuric acid complex,and background contamination.This article reviews recent developments for detecting melamine and discusses future directions.