Easy Sample Pretreatment Research Articles

Magnetic ionic liquid-based liquid-liquid microextraction followed by ultra-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry for simultaneous determination of neurotransmitters in human cerebrospinal fluid and plasma

A green, efficient and easy sample pretreatment method of magnetic ionic liquid-based liquid-liquid microextraction (MIL-based LLME) combined with a sensitive, rapid and precise analytical method of ultra-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UPLC-QqQ/MS2) was developed to simultaneously - determining of neurotransmitters (NTs) in biosamples. Two magnetic ionic liquids (MILs), [P6,6,6,14]3[GdCl6] and [P6,6,6,14]2[CoCl4] tested, and the latter was selected as the extraction solvent due to its advantages of visual recognition, paramagnetic behavior and higher extraction efficiency. Facile magnetic separation of MIL containing analytes from matrix was realized by applying external magnetic field without rather than centrifugation. Experimental parameters that would influence the extraction efficiency, including type and amount of MIL, extraction time, speed of the vortex process, salt concentration, and environmental pH, were optimized obtained. The proposed method was successfully applied to the simultaneous extraction and determination of 20 NTs in human cerebrospinal fluid and plasma samples. Excellent analytical performance indicates the broad potential of this method for clinical diagnosis and therapy of neurological diseases.

Determination of the Synthetic Antioxidants Butylated Hydroxyanisole (BHA) and Butylated Hydroxytoluene (BHT) by Matrix Acidity-Induced Switchable Hydrophilicity Solvent-Based Homogeneous Liquid-Liquid Microextraction (MAI-SHS-HLLME) and High-Performance Liquid Chromatography with Ultraviolet Detection (HPLC-UV)

A rapid and easy sample pretreatment procedure, matrix acidity-induced switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction, has been developed for the isolation of the synthetic antioxidants butylated hydroxyanisole and butylated hydroxytoluene from vinegar samples. Di-(2-ethylhexyl)phosphoric acid (DEHPA) was selected as the extraction solvent and its hydrophilic form was obtained in alkaline solution followed by the addition of vinegar, which acted as both the sample and the inductor of the switching reaction leading to the formation of DEHPA microdroplets. There was no need to centrifuge at this step, since the DEHPA phase containing the analytes was collected from the resulting mixture through magnetic retrieval due to its high affinity for Fe3O4 nanoparticles. After being magnetically separated, the desorbed analytes were analyzed by high performance liquid chromatography with ultraviolet detection (HPLC-UV). Under the optimized conditions, the limits of detection for the analytes were between 3.2 and 5.5 µg L−1 and the linear dynamic range was from 10 to 500 μg L−1. Good precision was obtained with relative standard deviations less than 7.8%. Recovery assays for spiked apple, grape, and white vinegar provided recoveries from 86 to 105%.

The search for a microbiological inhibition method for the rapid, broad-spectrum and high-throughput screening of six kinds of antibiotic residues in swine urine

In this study, a microbiological inhibition method for rapidly screening antibiotics in swine urine was established with an easy sample pre-treatment. The microbiological system consisted of an agar medium mixed with nutrients, sensitizers, a test bacterium (Geobacillus stearothermophilus ATCC12980) and pH indicator (bromocresol purple). It was observed that the detection limits of the test kit for twenty-eight common antimicrobial residues in urine, including β-lactams, aminoglycosides, tetracyclines, sulfonamides, macrolides, and lincosamides, were less than or equal to the maximum residue limits of the kidney, as determined by the EU and China. Moreover, the false negative rate and the false positive rate, along with other performance indexes such as interassay coefficients of variation and shelf life of the kit, all met the standard requirements of the ISO13969:2003 guidelines. Additionally, our results were consistent with those using the gold-standard physical chemistry method, which suggest the proposed method is suitable for screening antibiotic residues.

SU8/glass microchip capillary electrophoresis integrated with Pt electrodes for separation and simultaneous detection of phenylephrine and acetaminophen.

Introduction: A new microfluidic-based method with electrochemical detection was developed for the simultaneous quantification of acetaminophen (AP) and phenylephrine (PHE) pharmaceuticals in the human blood and pharmaceuticals (e.g. tablet and drop). Methods: The separation was achieved on a SU8/glass microchip with a 100 µm Pt working electrode that was positioned out of the channel and 2-(N-morpholino) ethanesulfonic acid was used as a running buffer (pH 7, 10 mM). Home designed modulated high voltage power supply and dual time switcher was used for controlling the injection and separation of the analytes in the unpinched injection mode. Results: The injection was carried out using +750 V for 7 seconds, and the separation and detection voltages were set at +1000 V and +0.9 V, respectively. Critical parameters such as detection potential, buffer concentration, injection, and separation voltage were studied in terms of their effects on the resolution, peak height, and migration times. For each analyte, the correlation coefficients were over 0.99 (n = 6). The developed microchip was able to detect AP and phenylephrine simultaneously with the limit of detection of 7.9 and 5.2 (µg/mL) respectively for PHE and AP and excellent linear range of 10-200 (µg/mL). The recovery of the drugs ranged from 96% to 103%, while the repeatability of the method through inter- and intra-day was lower than 7%. Conclusion: The developed method offers several advantages, including easy sample pretreatment process, simplicity, very fast analysis compared to other typical chromatographic methods. Thus, the proposed microfluidic-based method is proposed to be used as a time- and cost-effective monitoring method for the analysis of AP and PHE.

A microbiological inhibition method for the rapid, broad-spectrum, and high-throughput screening of 34 antibiotic residues in milk

In this study, we developed a microbiological inhibition method for the rapid screening of antibiotics in milk with Geobacillus stearothermophilus ATCC12980 as an indicator bacterium and an easy sample pretreatment. We observed that the limits of detection of the kit for 34 common antibiotic residues in milk, including β-lactams (13), aminoglycosides (6), tetracyclines (4), sulfonamides (6), macrolides (4), lincosamides (1), were lower than or close to the maximum residue limits formulated by the European Union and China. Moreover, the false-positive rate was 1% and the false-negative rates were less than 5%. The ruggedness of the method (the reproducibility of detection capability of different batches of medium) met requirements at determined levels and residual limits. The shelf life of the kit was more than 6 mo at 4°C. Additionally, we observed good correlations between the kit results and ultra-high-performance liquid chromatography-tandem mass spectrometry results for incurred milk (samples taken from animals treated with antibiotics according to the pre-slaughter medication data), which indicated that the kit was reliable for screening antibiotics in incurred samples. In conclusion, the kit has a broad application potential with high sensitivity, specificity, and reproducibility, stability, and reliability, combined with simple operation, low cost, and high-throughput capacity.

A novel sensitive and selective electrochemical sensor based on integration of molecularly imprinted with hollow silver nanospheres for determination of carbamazepine

An electrochemical sensor based on hollow silver nanospheres (hAgNS) and molecularly imprinted polymer (MIP) was developed for drug analysis by using carbamazepine (CBZ) as a model analyte. hAgNS, serving as a support material for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP film warrants improved selectivity for CBZ. Quantification based on the “MIP/gate effect” was performed by employing Fe(CN)63−/4− as the probe to indicate the current intensity. The sensor materials were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, a linear relationship of the electrical signal versus the concentration of CBZ was obtained in the range from 8.0 × 10−11 to 6.0 × 10−8 M with a detection limit of 3.2 × 10−11 M (S/N = 3). Moreover, the prepared sensor exhibited specific detection of CBZ over its structural analogues and interferents, and the established electrochemical method was validated using the standard method-high performance liquid chromatography (HPLC). Eventually, rapid and accurate determination of CBZ in rat serum and cell samples was carried out after easy sample pretreatment.

Determination of photoinitiator 4-methylbenzophenone in milk by cloud point extraction

An efficient and easy sample pretreatment methodology was proposed for the detection of photoinitiator 4-methylbenzophenone from milk before high-performance liquid chromatography. Appropriate conditions for demulsification were studied. The parameters affecting cloud point extraction, such as concentration of Tween-20, electrolyte salt, equilibration temperature, and time, have been investigated. When the spiked level was 200-1000 μg/kg, the average addition standard recovery was 99.14-105.98% with the optimum cloud point extraction conditions (concentration of Tween-20, 138 g/L; mass of anhydrous sodium sulfate, 0.75 g; equilibration temperature, 65°C; equilibration time, 30 min). To decrease the detection limits, further work about the organic solvent, shaking time, and ultrasonic parameters was carried. When the spiked level was 10-100 μg/kg, the average addition standard recovery was 70.40-106.91% with the optimum cloud point extraction and enrichment conditions (optimum cloud point extraction conditions; volume of cyclohexane, 30 mL; shaking time, 20 min; time of ultrasonic, 20 min; temperature of ultrasonic bath, 45°C).

Application of bilinear least squares/residual bilinearization in bulk liquid membrane system for simultaneous multicomponent quantification of two synthetic dyes

For the first time, this research reports a new application of bulk liquid membrane (BLM) with second-order calibration based on the bilinear least squares/residual bilinearization (BLLS/RBL) algorithm, as a novel method for simultaneous removal and quantification of allura red (AR) and sunset yellow (SY) as model compounds in soft drinks and food samples. Due to severe spectral overlapping between the AR and SY and strong colinearities present in the data set, common second-order multivariate calibration methods, such as parallel factor analysis (PARAFAC) and multivariate curve resolution-alternating least-squares (MCR-ALS), could not be successfully applied to the presently studied samples. At first, the basic experimental parameters affecting the transport of the target dyes were investigated and optimized. Then under the optimum conditions, we have explored an alternative use of BLLS/RBL methodology, which can work adequately with strongly overlapping spectra and colinearities problems. Satisfactory results were obtained for analysis of target analytes. The proposed method was validated by comparison with a reference method based on high-performance liquid chromatography-ultra violet detection (HPLC-UV) and no significant differences were found between the reference values and the ones obtained with the proposed method. Such a chemometrics-based protocol may be a very promising tool for more analytical applications in real samples monitoring, due to its advantages of easy sample pretreatment, accuracy, sufficient spectral resolution and concentration prediction even in the presence of unknown interferences.

Arrays of ZnO nanorods decorated with Au nanoparticles as surface-enhanced Raman scattering substrates for rapid detection of trace melamine

In this paper, as a new, highly sensitive and uniform hybrid surface-enhanced Raman scattering (SERS) substrate, arrays of ZnO nanorods (ZnO-NRs) decorated with Au nanoparticles (Au-NPs) have been prepared. This hybrid substrate manifests high SERS sensitivity to melamine and a detection limit as low as 1.0×10−10M (1.26µgL−1). A maximum enhancement factor of 1.0×109 can be obtained with the ZnO NF–Au (sample 2) film. Au-NPs gaps in the array can create lots of SERS “hot spots” that mainly contribute to the high SERS sensitivity. Moreover, the supporting chemical enhancement effect of ZnO-NRs and the better enrichment effect ascribed to the large surface area of the substrate also help to achieve a lower detection limit. The promising advantages of easy sample pretreatment, short detection time and low cost makes the arrays of ZnO-NRs decorated with Au-NPs substrate a potential detection tool in the field of food safety.

Silver deposited polystyrene (PS) microspheres for surface-enhanced Raman spectroscopic-encoding and rapid label-free detection of melamine in milk powder

Silver nanoparticles coated amino modified polystyrene microspheres (PS-NH2/Ag NPs) with extremely high surface enhanced Raman scattering (SERS) activity and uniform surface morphology were created by precise controlling of deposition time. Nanojets that were formed underneath the individual microspheres could be used for nondestructive analysis of species adsorbed on the smooth gold or glass surface. A 10 fold enhancement of SERS was observed between PS-NH2/Ag NPs and gold surface compared to glass surface due to more effective coupling of surface plasmonic resonance. These microsphere SERS substrates could detect 2-Mercaptopyridine down to 10−9M. Four different thiol compounds have been successfully utilized as tags to prepare SERS encoded PS-NH2/Ag NPs microspheres. Furthermore, the potential application of these SERS substrate for rapid detection of melamine in milk powder was explored. A linear relationship was observed between SERS intensity and logarithm of melamine concentrations with the limit of detection (LOD) of 1.9×10−8mol/L. The promising advantages of easy sample pretreatment, low protein background interference, short detection time and low cost makes the PS-NH2/Ag NPs substrate a potential detection tool in the field of food safety.

Simultaneous determination of pre-emergence herbicides in environmental samples using HPLC-DAD combined with second-order calibration based on self-weighted alternating trilinear decomposition algorithm

This work presents a novel strategy for simultaneous and rapid quantitative analysis of three pre-emergence herbicides in environmental samples using HPLC-DAD combined with second-order calibration based on the self-weighted alternating trilinear decomposition (SWATLD) algorithm. The sample preparation procedure was simplified only by using water as solvent and methanol as extractant and data were measured in less than 4.2 min by applying an isocratic mode. Although the elution and spectral profiles of the analytes, prometryne (PRO), napropamide (NAP) and alachlor (ALA), are heavily overlapped with each other and with matrix constitutes, the method not only extracts the profiles of the analytes, but also simultaneously determines the concentrations of them in actual complex systems, i.e., river sediment and wastewater samples. In the analysis of river sediment and wastewater samples, the obtained average recoveries were 99 ± 6% and 98 ± 5% for PRO, 108 ± 6% and 100 ± 4% for NAP and 98 ± 5% and 97 ± 4% for ALA, respectively. Furthermore, the accuracy and precision of the proposed method was also evaluated through elliptical joint confidence region tests as well as figures of merit. Such a chemometrics-based protocol may be a very promising tool for more analytical applications in environment monitoring, due to its advantages of easy sample pretreatment, green, sufficient spectral resolution and concentration prediction even in the presence of unknown interferences.

Simultaneous determination of 6-methylcoumarin and 7-methoxycoumarin in cosmetics using three-dimensional excitation–emission matrix fluorescence coupled with second-order calibration methods

This paper reports a simple, rapid, and effective method for quantitative analysis of 6-methylcoumarin (6-MC) and 7-methoxycoumarin (7-MOC) in cosmetics using excitation–emission matrix (EEM) fluorescence coupled with second-order calibration. After simple pretreatments, the adopted calibration algorithms exploiting the second-order advantage, i.e., parallel factor analysis (PARAFAC) and self-weighted alternating tri-linear decomposition (SWATLD), could allow the individual concentrations of the analytes of interest to be predicted even in the presence of uncalibrated interferences. In the analysis of facial spray, with the external calibration method, the average recoveries attained from PARAFAC and SWATLD with the factor number of 3 ( N = 3) were 101.4 ± 5.5 and 97.5 ± 4.1% for 6-MC, and 103.3 ± 1.7 and 101.7 ± 1.8% for 7-MOC, respectively. Moreover, in the analysis of oil control nourishing toner, the standard addition method (SAM) was suggested to overcome the partial fluorescence quenching of 6-MC induced by the analyte–background interaction, which also yielded satisfactory prediction results. In addition, the accuracy of the two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM), including sensitivity (SEN), selectivity (SEL) and limit of detection (LOD). It was found that both algorithms could give accurate results, only the performance of SWATLD was slightly better than that of PARAFAC in the cases suffering from matrix effects. The method proposed lights a new avenue to determine quantitatively 6-MC and 7-MOC in cosmetics, and may hold great potential to be extended as a promising alternative for more practical applications in cosmetic quality control, due to its advantages of easy sample pretreatment, non-toxic and non-destructive analysis, and accurate spectral resolution and concentration prediction.

High Resolution Inductively Coupled Plasma Mass Spectrometry Allows Rapid Assessment of Iron Absorption in Infants and Children

Stable isotope absorption studies of iron have been limited by the high cost and limited availability of isotope ratio analysis using thermal ionization MS (TIMS). The development of high-resolution double focusing inductively coupled plasma MS (ICP-MS) may permit more cost-efficient sample analysis due to its high throughput, lower cost, easy sample pretreatment, and greater availability. Our objective was to develop an ICP-MS methodology for the measurement of iron isotope ratios using very small blood volumes. We developed a technique using multiple iron-nickel mixing standard solutions to adjust for nickel interference calibration. RBC samples from human subjects previously given 58Fe and 57Fe were analyzed for iron isotope ratios and compared with our current methodology (TIMS). Reproducibility of iron isotope ratios provided external relative SD < 0.5 and 0.7% (1 SD) for 57Fe/54Fe and 58Fe/54Fe, respectively. Iron isotope ratios from ICP-MS analysis did not differ from those from TIMS based on statistical analyses, nor did the calculated iron absorption values. The mean and SD of iron absorption did not differ when measured by TIMS or ICP-MS. A 2-microL RBC sample was sufficient for ICP-MS iron isotope ratio analysis with an internal relative SD < 0.5% and analytical time < 5 min. This technique may assist groups in increasing their use of stable isotope methods to assess iron absorption in infants and children.

Determination of hydroquinone in cosmetic emulsion using microdialysis sampling coupled with high-performance liquid chromatography

A method based on microdialysis sampling combined with high-performance liquid chromatography (HPLC) has been developed for the determination of hydroquinone in cosmetic emulsion. In microdialysis sampling, using deionized water as perfusate, a probe length of 10 mm and dialysis flow-rate of 5 μl min −1 were found to be the optimum conditions for the analysis. The accuracy (% bias) for intra-day ( n = 3) and inter-day ( n = 12, four consecutive days) ranged from −9.5 to 13.0% with a precision less than 7.55% relative standard deviation (R.S.D.). Recovery obtained between 89 and 112% by adding hydroquinone standards into medicated cosmetics and the coefficients of variance between 0.5 and 3.3%. The linearity of calibration curve is in the range of 2 μM–2 mM with an R 2 value for the linear regression of 0.9981. The detection limit is 0.2 μM derived from the three times of signal-to-noise ratio. This method has been applied to determine the hydroquinone content in medicated and non-medicated cosmetics. The contents of hydroquinone in the medicated cosmetics are 5.36% (0.12% R.S.D., n = 3) and 3.85% (0.26% R.S.D., n = 3), respectively; in contrast to the percentages given by the manufacturer are 5 and 4%, the accuracy (% bias) are 7.20 and 3.75%, respectively. No hydroquinone was detected in non-medicated cosmetics. The proposed method has the advantages of easy sample pretreatment, rapid isolation and lower organic solvent consumption than in other methods for the determination of hydroquinone in cosmetics.

Quantitative measurement of ketone bodies in urine using reflectometry

Recently, automated urine test strip readers became available that can report quantitative data. We explored the possibility of measuring all ketone bodies (acetone, acetoacetate, 3-hydroxybutyrate) in urine with these test strips. Monitoring urinary ketone concentrations could offer the advantages of measuring higher values (due to the low renal thresholds) and being less sensitive to fluctuations. We evaluated URISYS 2400 (Roche) quantitative reflectance data for the ketone reflectance field and compared it with biochemical data from urine samples. Using an easy sample pre-treatment with 3-hydroxybutyrate dehydrogenase, we were able to assay 3-hydroxybutyrate as well, which normally does not react on urine test strips. Within- and between-run reproducibility of the reflectance signal for high- and low-concentration urine pools was 11.0-3.6% and 11.0-5.8% for aceto-acetate, 8.2-9.2% and 10.4-16.1% for acetone, and 5.1-3.0% and 5.6-3.5% for 3-hydroxybutyrate, respectively. The lower limit of detection for acetoacetate was 0.13 mmol/L (CV=3.6%). Fair agreement was obtained between test strip data for ketones andcolorimetrically determined acetoacetate values (r=0.90). In urine test strip analysis, quantitative ketone reflectance data allow a simple and fast analysis, offering affordable screening for the detection of ketone body production in diabetes, especially in emergency settings.

Determination of trace elements in wines and classification according to their provenance.

Provenance and authenticity of wines can be recognized on the basis of typical mineral and trace element patterns by means of chemometric methods. Therefore analytical methods were developed for the determination of As, Be, Co, Cs, Ga, Li, Nb, Ni, Rb, Te, Ti, W, Y, and Zr as well as Mo, Cd, Sb, Tl, U, and the rare earth elements in wines by inductively coupled plasma mass spectrometry (ICP-MS). For low risk of contamination or loss of analyte as well as depletion of sample amount and an easy sample pretreatment, direct measurement of diluted wines was studied. The accuracy of the analytical results was proven by recovery experiments by method comparison with standard addition methods and measurement of digested wines. In addition to applying statistical methods for characterizing the precision of the methods, the uncertainty of the measurements was estimated. Results for the elements mentioned above and additional 16 elements (Al, B, Ba, Ca, Cr, Cu, Fe, Mn, Mg, P, Pb, Si, Sn, Sr, V, and Zn) were evaluated by data analytical methods. Due to a specific choice of the analytes for multivariate statistical investigation a prediction rate by cross validation of 88.6% could be achieved.

Determination of polyamines in serum by high-performance capillary zone electrophoresis with indirect ultraviolet detection

A method for determining polyamines in serum by capillary zone electrophoresis (CZE) with indirect ultraviolet detection was established. The concentrations of polyamines in the sera of six healthy adults were determined and the results were in accordance with those obtained previously by high-performance liquid chromatography (HPLC). However, the CZE method is superior to HPLC in that it has high sensitivity, small sample consumption and easy sample pretreatment.

Ion exchange and purification of carbohydrates on a Nafion® membrane as a new sample pretreatment for matrix‐assisted laser desorption/ionization mass spectrometry

AbstractA Nafion membrane was tested as a new tool for a fast and easy sample pretreatment for matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) measurements. This membrane material was used for ion exchange and carbohydrate purification with minimal quantities of sample solution. An ion exchange method for carbohydrates was developed and demonstrated on a Dextran sample. The cations of the original sample were replaced within minutes by potassium or cesium ions. Another feature of this membrane was the fact that proteins and peptides adsorb on the acid surface. This behavior was investigated as a purification step for carbohydrates with high peptide and protein impurity concentrations. It was found that oligosaccharide libraries from rat‐ and mouse IgG mass spectra can be obtained clearly in the presence of high peptide impurities.