Matrix solid-phase dispersion as a valuable tool for extracting contaminants from foodstuffs

This review updates our knowledge on matrix solid-phase dispersion (MSPD), a sample treatment procedure that is increasingly used for extracting/purifying contaminants from a variety of solid, semi-solid, viscous, and liquid foodstuffs. MSPD is primarily used because of its flexibility, selectivity, and the possibility of performing extraction and cleanup in one step, this resulting in drastically shortening of the analysis time and low consumption of toxic and expensive solvents. Technical developments and parameters influencing the extraction yield and selectivity are examined and discussed. Experimental results for the analysis of pesticides, veterinary drugs, persistent environmental chemicals, naturally occurring toxicants, and surfactants in food are reviewed.     

Matrix solid‐phase dispersion with sand in chromatographic analysis of essential oils in herbs

Introduction – Matrix solid‐phase dispersion (MSPD) is a very simple, cheap and relatively quick sample preparation procedure which involves simultaneous disruption and extraction of various solid and semi‐solid samples due to the direct mechanical blending of the sample with a SPE sorbent, mainly C₁₈. Little is known about MSPD application as a sample preparation method for the analysis of essential oil components in herbs. Objective – To evaluate if C₁₈ sorbent, commonly used in MSPD process, can be substituted with sand in the procedure of essential oil analysis. Methodology – Essential oil extracts were obtained from mint, sage, chamomile, marjoram, savory and oregano using MSPD with C₁₈ sorbent or sand, pressurised liquid extraction and steam distillation. Their qualitative and quantitative compositions ware established by GC‐MS and GC‐FID. Results – The results prove that C₁₈ sorbent can be substituted with sand in the procedure of essential oil analysis in herbs. The recoveries of essential oil components estimated using MSPD/sand are almost equal to those using pressurised liquid extraction. Conclusion – The results presented in the paper reveal that MSPD with sand is suitable for the isolation of essential oil components from herbs. Its extraction efficiency is equivalent to pressurised liquid extraction, recognised as one of the most efficient extraction methods. The cost of MSPD procedure for essential oil analysis can be significantly diminished by substituting C₁₈ with sand. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of matrix solid-phase dispersion methodology to the extraction of endogenous peptides from porcine hypothalamus samples for MS and LC-MS analysis

In this study, we investigated a novel application of matrix solid-phase dispersion (MSPD) methodology for the extraction of endogenous peptides from porcine hypothalamus tissue samples. Several experimental factors of the MSPD procedure were examined. Finally, silica-based octadecyl was chosen as dispersing material and blended with 0.25 g porcine hypothalamus at a ratio of 5, and 10 mL of 60% acetonitrile with 0.2% formic acid in water was chosen as the extraction and elution solvent. This MSPD extraction method was compared to the classic acid extraction method. More peaks were observed in the MSPD extracts (74±5) by MALDI-TOF MS than in acid extracts (34±5). Moreover, 14 potential endogenous peptides were identified in the MSPD extracts after nanoLC-MS/MS analysis, while only 2 endogenous peptides in the acid extracts. These results indicated that MSPD could be employed as a simple and efficient method for the extraction of endogenous peptides from tissues.     

Matrix solid phase dispersion (MSPD)

A review of the many uses of matrix solid phase dispersion (MSPD) in the extraction and analysis of a variety of compounds from a range of samples is provided. Matrix solid phase dispersion (MSPD) has found particular application as a somewhat generic analytical process for the preparation, extraction and fractionation of solid, semi-solid and/or highly viscous biological samples. Its simplicity and flexibility contribute to it being chosen over more classical methods for these purposes. MSPD is based on several simple principles of chemistry and physics, involving forces applied to the sample by mechanical blending to produce complete sample disruption and the interactions of the sample matrix with a solid support bonded-phase (SPE) or the surface chemistry of other solid support materials. These principles are discussed as are the factors to be considered in conducting a MSPD extraction.     

Matrix solid phase dispersion (MSPD)

A review of the many uses of matrix solid phase dispersion (MSPD) in the extraction and analysis of a variety of compounds from a range of samples is provided. Matrix solid phase dispersion (MSPD) has found particular application as a somewhat generic analytical process for the preparation, extraction and fractionation of solid, semi-solid and/or highly viscous biological samples. Its simplicity and flexibility contribute to it being chosen over more classical methods for these purposes. MSPD is based on several simple principles of chemistry and physics, involving forces applied to the sample by mechanical blending to produce complete sample disruption and the interactions of the sample matrix with a solid support bonded-phase (SPE) or the surface chemistry of other solid support materials. These principles are discussed as are the factors to be considered in conducting a MSPD extraction.     

Current trends in solid-phase-based extraction techniques for the determination of pesticides in food and environment

Solid-phase extraction (SPE) procedures for pesticide residues in food and environment are reviewed and discussed. The use of these procedures, which include several approaches such as: matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE), represents an opportunity to reduce analysis time, solvent consumption, and overall cost. SPE techniques differ from solvent extraction depending on the interactions between a sorbent and the pesticide. This interaction may be specific for a particular pesticide, as in the interaction with an immunosorbent, or non-specific, as in the way a number of different pesticides are adsorbed on apolar or polar materials. A variety of applications were classified according to the method applied: conventional SPE, SPME, hollow-fiber micro-extraction (HFME), MSPD and SBSE. Emphasis is placed on the multiresidue analysis of liquid and solid samples.     

Current trends in solid-phase-based extraction techniques for the determination of pesticides in food and environment

Solid-phase extraction (SPE) procedures for pesticide residues in food and environment are reviewed and discussed. The use of these procedures, which include several approaches such as: matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE), represents an opportunity to reduce analysis time, solvent consumption, and overall cost. SPE techniques differ from solvent extraction depending on the interactions between a sorbent and the pesticide. This interaction may be specific for a particular pesticide, as in the interaction with an immunosorbent, or non-specific, as in the way a number of different pesticides are adsorbed on apolar or polar materials. A variety of applications were classified according to the method applied: conventional SPE, SPME, hollow-fiber micro-extraction (HFME), MSPD and SBSE. Emphasis is placed on the multiresidue analysis of liquid and solid samples.     

Sea sand disruption method (SSDM) as a valuable tool for isolating essential oil components from conifers

Essential oils are one of nature's most precious gifts with surprisingly potent and outstanding properties. Coniferous oils, for instance, are nowadays being used extensively to treat or prevent many types of infections, modify immune responses, soothe inflammations, stabilize moods, and to help ease all forms of non-acute pain. Given the broad spectrum of usage of coniferous essential oils, a fast, safe, simple, and efficient sample-preparation method is needed in the estimation procedure of essential oil components in fresh plant material. Generally, the time- and energy-consuming steam distillation (SD) is applied for this purpose. This paper will compare SD, pressurized liquid extraction (PLE), matrix solid-phase dispersion (MSPD), and the sea sand disruption method (SSDM) as isolation techniques to obtain aroma components from Scots pine (Pinus sylvestris), spruce (Picea abies), and Douglas fir (Pseudotsuga menziesii). According to the obtained data, SSDM is the most efficient sample preparation method in determining the essential oil composition of conifers. Moreover, SSDM requires small organic solvent amounts and a short extraction time, which makes it an advantageous alternative procedure for the routine analysis of coniferous oils. The superiority of SSDM over MSPD efficiency is ascertained, as there are no chemical interactions between the plant cell components and the sand. This fact confirms the reliability and efficacy of SSDM for the analysis of volatile oil components.     

Matrix solid-phase dispersion extraction coupled with HPLC-diode array detection method for the analysis of sesquiterpene lactones in root of Saussurea lappa C.B.Clarke

We developed a reliable and effective method to determine costunolide and dehydrocostuslactone in the root of Saussurea lappa C. B.Clarke using matrix solid-phase dispersion (MSPD) extraction, HPLC separation and diode array detection (DAD). Several extraction parameters for the MSPD were optimized. Florisil was chosen as dispersing adsorbent with methanol as elution solvent. The ratio of Florisil to sample was selected to be 4:1 and no additional clean-up steps were needed. Linearities (r>0.9995) were determined to be in the range of 22.5-360.0 μg/mL for costunolide and 25.0-400.0 μg/mL for dehydrocostuslactone. Intra- and inter-day precisions were also determined with a relative standard deviation (RSD) less than 3.2%. The limits of detection were found to be 0.122 μg/mL for costunolide and 0.135 μg/mL for dehydrocostuslactone. The recoveries were in the range of 92.5-99.8% with relative standard deviations ranged from 1.2% to 3.5%. The proposed MSPD method required shorter time and lower solvent volume than maceration-ultrasonic and Soxhlet extraction methods.     

Lysis and fractionation of Mycobacterium paratuberculosis and Escherichia coli by matrix solid-phase dispersion.

A novel method for the lysis and subsequent fractionation of bacterial constituents from Mycobacterium paratuberculosis strain 19698 (M. paratuberculosis) and Escherichia coli strain DH5 alpha utilizing the technique of matrix solid-phase dispersion (MSPD) is described. Bacteria were blended with octadecylsilyl (C18) derivatized silica to obtain cellular lysis. The blended material was used to prepare a column which was sequentially eluted with solvents of increasing polarity. Fractionation of cellular components was confirmed by analysis of the solvent extracts. The possible applicability of the MSPD technique as a general method for the lysis and fractionation of bacterial components is proposed.     

Optimization of a matrix solid-phase dispersion method for the determination analysis of carbendazim residue in plant material

The objective of this paper was to prove that matrix solid-phase dispersion (MSPD) coupled with high performance liquid chromatography (HPLC) and column switching could be used for the determination and quantification of carbendazim residue in plant samples. By comparing results obtained after optimization of the extraction conditions on an acidic silica gel column, it was determined that sorption and retention of carbendazim were achieved via specific interactions. The method of standard additions was used for quantitative analysis. Its performance was evaluated and validated: the detection limit (UV-Vis detection at lambda=279 nm) was 0.02 microg/g, the relative standard deviations (R.S.D.) were between 2.7 and 4.1% and the recoveries were ranging from 84.3 to 90.7% at the 0.04, 0.08 and 0.1 microg/g fortification levels. The method was successfully tested on cereal samples, and the results obtained with the present off-line MSPD-HPLC procedure were found to compare well with those obtained with procedure involving LLE.     

Reconsideration of sample pH adjustment in bioanalytical liquid-liquid extraction of ionisable compounds

Liquid-liquid extraction (LLE) is widely used as a simple and robust sample preparation technique in bioanalytical sample preparation. When extracting ionisable compounds, most bioanalysts adjust the pH of the sample to achieve fully unionized compounds. Usually, a generally accepted rule is applied to adjust the pH of the aqueous phase, known as the pKa+/-2 rule, depending on the acid/base characteristics of the analyte. By taking a closer look at the general equations that describe the extraction behaviour of ionisable compounds, we extended this pH adjustment rule by taking the distribution ratio and the volume of both liquid phases into account. By choosing an extraction pH based on this extended rule, the selectivity of the extraction can be influenced without loss of recovery. As a measure of this selectivity, two equations were proposed to indicate the ability of the extraction system to discriminate between two compounds. Also, milder extraction pH can be used for pH labile analytes. To use this new rule quantitatively, a new calculation method for the determination of the distribution ratio was derived. These calculations were based on normalized recoveries making this method less susceptible to errors in absolute recovery determination. The proposed equations were supported by demonstrating that careful pH adjustment can lead to higher selectivity. The main conclusion was that a closer look at the extraction pH in bioanalytical methods extends the possibilities of obtaining a higher selectivity or the possibilities of extracting pH labile analytes at milder pH conditions without loss of recovery.     

Validation of qualitative chromatographic methods: strategy in antidoping control laboratories

An experimental approach for the validation of chromatographic qualitative methods and its application in an antidoping control laboratory is described. The proposed strategy for validation of qualitative methods consists of the verification of selectivity/specificity, limit of detection (LOD), extraction recovery and repeatability (intra-assay precision). A one-day assay protocol, based on the analysis of five blank samples obtained from different sources and four replicates of control samples at two different concentrations of the analytes, has been defined to evaluate the validation parameters. The following evaluation criteria have been applied: absence of interfering substances at the retention time of the analytes in the blank samples to check the selectivity/specificity of the method, the LOD recommended by international sports authorities has to be attained, and for repeatability, the relative standard deviation should be <25% for the low concentration control sample and <15% for the high concentration control sample. Qualitative screening procedures are able to detect a great number of analytes so that extraction and analysis conditions are always a compromise for the different analytes. For this reason, no minimum acceptance criteria have been defined for data of extraction recoveries. The proposed protocol has been used for the validation of the screening and confirmation qualitative methods included in the scope of the accreditation of an antidoping control laboratory according to ISO quality standards.     

Determination of the major constituents in fruit of Arctium lappa L. by matrix solid-phase dispersion extraction coupled with HPLC separation and fluorescence detection

The arctiin and arctigenin in the fruit of Arctium lappa L. were extracted by matrix solid-phase dispersion (MSPD) and determined by high-performance liquid chromatography (HPLC) with fluorescence detection. The experimental conditions for the MSPD were optimized. Silica gel was selected as dispersion adsorbent and methanol as elution solvent. The calibration curve showed good relationship (r > 0.9998) in the concentration range of 0.010–5.0 μg mL⁻¹ for arctiin and 0.025–7.5 μg mL⁻¹ for arctigenin. The recoveries were between 74.4% and 100%. The proposed method consumed less sample, time and solvent compared with conventional methods, including ultrasonic and Soxhlet extraction.     

High total cholesterol and triglycerides levels increase arginases metabolism,impairing nitric oxide signaling and worsening fetoplacental endothelial dysfunction in gestational diabetes mellitus pregnancies

Maternal physiological dyslipidemia (MPD) supports fetal development in human pregnancy. However, some women develop maternal supraphysiological dyslipidemia (MSPD: increased total cholesterol (TC) and triglycerides (TG) levels). MSPH is present in normal and also in gestational diabetes mellitus (GDM) pregnancies. MSPD and GDM associate with fetoplacental endothelial dysfunction, producing alterations in nitric oxide (NO)-L-arginine/arginase metabolism. Nevertheless, the effect of MSPD on GDM, and how this synergy alters fetoplacental endothelial function is unknown. Therefore, the aim of this study was to evaluate in human umbilical vein endothelial cells, the effects of MSPD in GDM and how these pathologies together affect the fetoplacental endothelial function. 123 women at term of pregnancy were classified as MPD (n = 40), MSPD (n = 35), GDM with normal lipids (GDM-MPD, n = 23) and with increased lipids (GDM-MSPD, n = 25). TC ≥291 mg/dL and TG ≥275 mg/dL were considered as MSPD. Endothelial NO synthase (eNOS), human cationic amino acid transporter 1 (hCat1), and arginase II protein abundance and activity, were assayed in umbilical vein endothelial cells. In MSPD and GDM-MSPD, TC and TG increased respect to MPD and GDM-MPD. eNOS activity was reduced in MSPD and GDM-MSPD, but increased in GDM-MPD compared with MPD. However, decreased tetrahydrobiopterin levels were observed in all groups compared with MPD. Increased hCat1 protein and L-arginine transport were observed in both GDM groups compared with MPD. However, the transport was higher in GDM-MSPD compared to GDM-MPD. Higher Arginase II protein and activity were observed in GDM-MSPD compared with MPD. Thus, MSPD in GDM pregnancies alters fetal endothelial function associated with NO metabolism.     

Molecularly imprinted polymer cartridges coupled on-line with high performance liquid chromatography for simple and rapid analysis of dextromethorphan in human plasma samples

In this paper, a novel method is described for automated determination of dextromethorphan in biological fluids using molecularly imprinted solid-phase extraction (MISPE) as a sample clean-up technique combined with high performance liquid chromatography (HPLC). The water-compatible molecularly imprinted polymers (MIPs) were prepared using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linker, chloroform as porogen and dextromethorphan as template molecule. These imprinted polymers were used as solid-phase extraction sorbent for the extraction of dextromethorphan from human plasma samples. Various parameters affecting the extraction efficiency of the MIP cartridges were evaluated. The high selectivity of the sorbent coupled to the high performance liquid chromatographic system permitted a simple and rapid analysis of this drug in plasma samples with limits of detection (LOD) and quantification (LOQ) of 0.12 ng/mL and 0.35 ng/mL, respectively. The MIP selectivity was evaluated by analyzing of the dextromethorphan in presence of several substances with similar molecular structures and properties. Results from the HPLC analyses showed that the recoveries of dextromethorphan using MIP cartridges from human plasma samples in the range of 1-50 ng/mL were higher than 87%.     

A rapid method for the extraction and determination of vitamin E metabolites in human urine

A method for the direct extraction and routine analysis of the vitamin E metabolites gamma- and alpha-carboxyethyl hydroxychroman (gamma- and alpha-CEHC) from human urine has been developed. A relatively small sample volume (5 ml) can be used and, after enzymatic hydrolysis of the conjugated forms and acidification, the metabolites are extracted with diethyl ether. Recovery of alpha- and gamma-CEHC was compared to that of trolox, used as an internal standard, added to 24-h urine collections from vitamin E-unsupplemented volunteers. Various solvent conditions were initially tested; acidification and ether extraction gave the highest recovery. It was found that after addition and extraction from urine, trolox, alpha- and gamma-CEHC are recovered to a similar extent, hence trolox is viable as an internal standard. The samples were analyzed by both GC and HPLC with electrochemical detection (ECD). HPLC-ECD was found to give higher selectivity and higher sensitivity compared to GC or HPLC with UV detection at 290 nm. The HPLC-ECD detection limit was 10 fmol, linearity (r(2) > 0.98) was achieved in the range of 40 to 200 fmol, which was found to be optimal for 24-h urines from unsupplemented subjects. Inter-sample variability was typically 2-5%. This greater sensitivity and selectivity means that vitamin E metabolites can be analyzed even in unsupplemented subjects. It is also possible to measure unconjugated forms of the metabolites. Typically these were found to represent approximately 10% of the total alpha- and gamma-CEHC. This method can be used routinely for the determination of vitamin E metabolites in urine. The new extraction and detection methods described are relatively quick, less laborious, and more cost-effective than previously available methods.     

Analysis of alkylphenol and bisphenol A in eggs and milk by matrix solid phase dispersion extraction and liquid chromatography with tandem mass spectrometry

A method based on matrix solid phase dispersion (MSPD) using C18 as dispersant, and a subsequent cleanup step with amino-propyl solid phase extraction cartridges and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been developed for the simultaneous determination of nonylphenol (NP), octylphenol (OP) and bisphenol A (BPA) in eggs and milk. Recovery studies were performed at different fortification levels. Average recoveries by MSPD varied from 79% of BPA to 98% of NP and relative standard deviations were equal or lower than 15% for egg samples. The average recoveries in milk ranged from 86 to 84% for BPA, 90 to 99% for NP and 82 to 103% for OP and relative standard deviations were equal to or lower than 8%. The limits of detection (LODs) in eggs were 0.10, 0.10 and 0.25 microg/kg for BPA, NP and OP, respectively and LODs for milk were 0.10, 0.05 and 0.10 microg/kg for BPA, NP and OP, respectively. Investigation of the levels in commercial samples indicated that NP was ubiquitous in milk and eggs at levels ranging from 4.24 to 17.60 microg/kg, and the milk samples were more heavily contaminated by NP than were the egg samples.     

Butanol recovery from fermentations by liquid-liquid extraction and membrane solvent extraction

Extraction can successfully be used for in-situ alcohol recovery in butanol fermentations to increase the substrate conversion. An advantage of extraction over other recovery methods may be the high capacity of the solvent and the high selectivity of the alcohol/water separation. Extraction, however, is a comprehensive operation, and the design of an extraction apparatus can be complex. The aim of this study is to assess the practical applicability of liquid-liquid extraction and membrane solvent extraction in butanol fermentations. In this view various aspects of extraction processes were investigated.Thirty-six chemicals were tested for the distribution coefficient for butanol, the selectivity of alcohol/water separation and the toxicity towards Clostridia. Convenient extractants were found in the group of esters with high molar mass.Liquid-liquid extraction was carried out in a stirred fermenter and a spray column. The formation of emulsions and the fouling of the solvent in a fermentation broth causes problems with the operation of this type of equipment. With membrane solvent extraction, in which the solvent is separated from the broth by a membrane, a dispersion-free extraction is possible, leading to an easy operation of the equipment. In this case the mass transfer in the membrane becomes important.With membrane solvent extraction the development of a process is emphasized in which the extraction characteristics of the solvent are combined with the property of silicone rubber membranes to separate butanol from water. In the case of apolar solvents with a high molar mass, the characteristics of the membrane process are determined completely by the solvent. In the case of polar solvents (e.g. ethylene glycol), the permselectivity of the membrane can profitably be used. This concept leads to a novel type of extraction process in which alcohol is extracted with a water-soluble solvent via a hydrophobic semipermeable membrane. This extraction process has been investigated for the recovery of butanol and ethanol from water. A major drawback in all processes with membrane solvent extraction was the permeation of part of the solvent to the aqueous phase.The extraction processes were coupled to batch, fed batch and continuous butanol fermentations to affirm the applicability of the recovery techniques in the actual process. In the batch and fed batch fermentations a three-fold increase in the substrate consumption could be achieved, in the continuous fermentation about 30% increase.     

Use of supercritical fluid extraction in the analysis of pesticides in soil

The applicability of supercritical fluid extraction (SFE) in pesticide residue analysis in soil was investigated by analysing real soil samples from field experiments. Additionally, radiotracer batch experiments were performed to study the release of non-extractable residues. High repeatability, accuracy and high selectivity were the most important advantages of SFE in residue analysis. Extracts with low amounts of coextractants from the soil matrix were achieved, allowing extracts to be pooled and concentrated without further clean up steps. Thus, the limited volume of extraction thimbles of the SFE apparatus used could be compensated and insufficiently high limits of determination could be improved. Although the application of methanol-modified supercritical CO(2) was a time-saving extraction procedure which reduced solvent usage and solvent waste, SFE efficiency proved only competitive to conventional slurry and Soxhlet extraction. No exhaustive release of non-extractable residues was achieved in radiotracer batch experiments.