Matrix Interference Effects Research Articles

Solid Phase Extraction Method for the Determination of Ni(ll), Cu(ll) and Zn(ll) by Flame Atomic Absorption Spectrometry Using Schiff Base in Various Water Samples

A novel column solid phase extraction procedure was developed for the determination of Ni(II), Cu(II) and Zn(II) in water samples using newly synthesized reagent 1-(2-hydroxy-5- methoxybenzalidene)thiosemicarbazide for preconcentration and separation prior to FAAS using octylpolyethylene glycolphenyether (Triton x-100). The sorbed elements were subsequently eluted with 10 mL of 1 M HNO3 and the acid elutes were analysed by FAAS. Various parameters such as pH, amount of adsorbent, eluent type and volume, flow-rate of the sample solution, volume of the sample solution and matrix interference effect on the retention of the metal ions have been studied. The optimum pH for the sorption of above mentioned metal ions was about 7.0±0.5. The loading capacity of adsorbent for Ni(II), Cu(II) and Zn(II) were found to 28, 26 and 20 µg mL -1 respectively. The limit of detections were found to be 3.6, 3.2 and 3.6 µg mL -1 for Ni(II), Cu(II) and Zn(II) respectively by applying a preconcentration factor 83. Recoveries under optimum conditions were found to be 97.6 to 104% at the 98% confident level. The proposed enrichment method was applied successfully for the determination of metal ions in various water samples. The results were obtained are good agreement with reported method.

A novel method for determining vitamin B1 in a wide variety of foodstuffs with or without polyphenols

Certain foodstuffs exhibit matrix interference effects on the vitamin B1 analysis prescribed in the official methods of the European Union, AOAC International, and Japan. In this study, we demonstrated that one of the problematic polyphenols in green tea or cocoa was tannin. For these matrices, thiamine was found to interact with tannin in the extraction step and was thus removed by filtration as a residue. To resolve the matrix interference, we proposed lowering the pH of the extraction solution by adding hydrochloric acid after the enzyme reaction. High precision (2–3% RSDr) and good recovery (98.3–103%) were obtained with reference materials using the proposed method. We also confirmed the equivalence of the obtained data from the proposed method and the Japanese official method for nutritional labeling. From these results, the method was found to be effective for vitamin B1 analysis regardless of the presence of interference matrices.

Effect of evaporation and matrix interferences on the association of simulated ignitable liquid residues to the corresponding liquid standard

Identification of an ignitable liquid in fire debris evidence can be complicated due to evaporation of the liquid, matrix interferences, and thermal degradation of both the liquid and the matrix. In this research, liquids extracted from simulated fire debris were compared to the original liquid using multivariate statistical procedures. Neat and evaporated gasoline and kerosene standards were spiked onto nylon carpet, which was subsequently burned. The ignitable liquid residues were extracted using a passive headspace procedure and analyzed by gas chromatography–mass spectrometry. Pearson product moment correlation coefficients, hierarchical cluster analysis, and principal components analysis were used to compare the liquids extracted from the carpet to the corresponding neat liquid. For each procedure, association of the extracts according to liquid type was possible, albeit not necessarily to the specific evaporation level. Of the three procedures investigated, principal components analysis offered the most promise since contributions from matrix interferences were essentially eliminated.

A new pretreatment and improved method for determination of selected estrogens in high matrix solid sewage samples by liquid chromatography mass spectrometry

This article describes a pretreatment procedure for samples that possess high matrix interferences to better analyze four estrogens including estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinyl estradiol (EE2) and xenoestrogens bisphenol A (BPA) in solid samples, including the activated sludge and sediment samples investigated here. During the pretreatment procedure, the target compounds were extracted from the samples using accelerated solvent extraction (ASE), and the extracted samples were then purified using four steps for clean-up: liquid–liquid extraction (LLE), Florisil clean-up, aqueous alkali extraction (AAE) and hydrophilic–lipophilic balance (HLB) enrichment. The absolute recoveries of the activated sludge and sediment were 88–97% and 75–100%, respectively, and the limits of detection were both below 0.1ngg−1. After the activated sludge and sediment samples were purified using the four clean-up steps, their matrix interference effects decreased to 0.5–32% and −3.2–0.8%, respectively, and their absorbance values were also clearly reduced. However, the activated sludge and sediment samples that were extracted by ASE but were not purified through the above-mentioned four steps resulted in matrix interference effects on the four estrogens and BPA that reached 81–233% and 47–95%, respectively, in which E3 and BPA were completely suppressed in the activated sludge samples.

Development of a Screening Method for the Determination of PCBs in Water Using QuEChERS Extraction and Gas Chromatography-Triple Quadrupole Mass Spectrometry

A new method has been developed and validated for the simultaneous analysis of 11 polychlorinated biphenyls (PCBs), in water samples at trace levels by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Water samples were extracted by the QuEChERS (Quick Easy Cheap Effective Rugged and Safe) method. The QqQ analyzer acquired data in multiple reactions monitoring (MRM), permitting both quantification and confirmation in a single injection with a running time reduced up to 11.0 min. The effect of matrix interferences in extracts on analyte quantification and the identification of PCBs in water samples was deeply studied. The results showed that PCBs were prone to strong matrix interactions in water samples, and the quantification and identification of PCBs were highly affected by a matrix enhancement effect. To evaluate the performance of the method, validation experiments were carried out on water samples at three spiking levels (1.6, 8.0, 40.0 µg L(-1)). Recovery was in the range of 95 - 109% at 1.6 µg L(-1), 90 - 95% at 8.0 µg L(-1) and 97 - 102% at 40.0 µg L(-1), respectively. Precision values expressed as relative standard deviation (RSD) were lower than 15%. Linearity in the range of 0.5 - 50.0 µg L(-1) provided determination coefficients (R(2)) higher than 0.999 for all compounds. The limits of detection (LODs) for PCBs were ≤0.1 µg L(-1) and the limits of quantification (LOQs) ranged from 0.04 to 0.3 µg L(-1). The applicability of the proposed method to detect and quantify PCBs has been demonstrated in analyse of 15 real samples.

Overcoming the effects of matrix interference in the measurement of urine protein analytes.

Using multiplex bead assays to measure urine proteins has a great potential for biomarker discovery, but substances in urine (the matrix) can interfere with assay measurements. By comparing the recovery of urine spiked with known quantities of several common analytes, this study demonstrated that the urine matrix variably interfered with the accurate measurement of low abundance proteins. Dilution of the urine permitted a more accurate measure of these proteins, equivalent to the standard dilution technique when the diluted analytes were above the limits of detection of the assay. Therefore, dilution can be used as an effective technique for over-coming urine matrix effects in urine immunoassays. These results may be applicable to other biological fluids in which matrix components interfere with assay performance.

Sample Dilution in Omentin Measurement

In the studies, specific enzyme linked immunoassay (ELISA) method is generally used to determinate the plasma omentin level (1,2). There may be matrix effect interferences the omentin measurement. According to international union of pure and applied chemistry, matrix effect is the combined effect of all components of the sample other than the analyte on the measurement of the quantity. In standard laboratory procedures to determinate the plasma omentin by ELISA method, various proportions of dilution should be applied to the samples to reduce matrix interference effect. If the dilution operation is performed for any reason, the measured value must be multiplied by the dilution factor in good laboratory practice. The dilution factor will be 5, if 5fold dilution is applied to samples to reduce the matrix effect. If the sought parameter is measured 23 ng/mL in diluted sample, this value is multiplied by a dilution factor and 115 ng/mL should be reported which is the real value. In one of ours study, we used the BioVendor (BioVendorLaboratomi Medicina, Brno, Czech Republic) Human Omentin-1 ELISA reagent. In standard laboratory procedure, 40-fold dilution had been applied to the samples. In this case, the results had to be multiplied by 40. In this study, the average omentin values of the patients and control group were found 606.6±313.0 ng/mL and 357.5±147.4 ng/mL respectively (3). Although study of the Omentin-1 reference range not enough, manufacturer of the reagent we used in ours study has reported the omentin-1 level approximately 480±21 ng/mL in precision analysis. It has seen that the dilution factor was taking into account in some other similar studies, when the omentin levels were analyzed (4, 5).

An analytical method for the simultaneous trace determination of acidic pharmaceuticals and phenolic endocrine disrupting chemicals in wastewater and sewage sludge by gas chromatography-mass spectrometry

This article presents an analytical method based on solid-phase extraction (SPE) and gas chromatography coupled with mass spectrometry for the simultaneous determination of the most frequently used acidic pharmaceutical residues, ibuprofen, diclofenac, naproxen and ketoprofen (KFN), and phenolic endocrine disruptors, bisphenol (BPA), triclosan (TCS), nonylphenol, nonylphenol monoethoxylate and nonylphenol diethoxylate, in wastewater and sewage sludge samples. In the first phase of the study, each compound has been characterized individually and afterwards in mixture as a trimethylsilyl derivative in order to identify the characteristic ions (m/z ratio) constituting the mass spectrum and to choose the ions for quantification and confirmation. Subsequently, derivatization was evaluated by testing different variables such as the volume of the derivatization solvent bis(trimethylsilyl)trifluoroacetamide and the effect of each catalyst, pyridine and 1% trimethyl chlorosilane, in the derivatized solution. For the analysis of wastewater samples, two commercial SPE cartridges, C18 and Oasis HLB, were compared for their extraction efficiency of the target compounds. The key parameter of extraction procedure included the effect of pH (2.5, 5.3 and 7) of the loading solution. For solid samples, parameters such as the extracted biomass, the volume of the extraction organic solvent and the effect of matrix interferences in chromatographic analysis were evaluated. By using C18 cartridges as purification procedure and ultrasound sonication, satisfactory mean relative recoveries with BPA-d16 and meclofenamic acid as surrogates were obtained ranging from 91% to 117% for wastewater and 84% to 107% for sewage sludge samples. Nine-point calibration of the standard mixture was performed by linear regression analysis with a correlation coefficient >0.99 for all the tested compounds. Limits of detection for the developed methods were established between 0.3 (KFN) and 14.8 (BPA) ng L(-1), and 15.0 (TCS) and 32.9 (BPA) ng g(-1) for wastewater and sewage sludge, respectively. Application to real samples of the wastewater treatment plant in Athens, the capital of Greece, demonstrated the presence of all tested compounds in most of the samples.

Fast and sensitive determination of aluminium with RP-HPLC using an ultra-short monolithic column

A fast and sensitive reversed-phase high-performance liquid-chromatographic method for determination of aluminium in aqueous samples has been developed. The fluorescent aluminium-lumogallion complex (λex 505 nm, λem 574 nm), was formed with a pre-column reagent and then separated on a Chromolith® RP-18e Guard column using a two-tiered, stepped gradient program, with matrix elimination (5/95 (v/v) methanol/water), followed by elution (90/10 (v/v) methanol/water). This method achieved a run time of 2.5 min without compromising sensitivity (limit of detection = 5.6 × 10−10 M, limit of quantification = 7.2 × 10−7 M), precision (3.5% at 3.71 × 10−6 M) or accuracy (recovery = 97.5% ± 3.2%, n = 5, P = 0.95). This represents an improvement in run time by >50% compared to the fastest previously published method [Lee et al., Clin. Chem., 1996, 42, 1405–1411]. This method uses MES buffer (2-(N-morpholino)ethanesulfonic acid), which compared to other buffers is more easily purified, does not complex with aluminium, and can be used in lower concentrations. This method was applied to analysis of: deionised water for column comparison; seawater for matrix interference effects; and tea-infusion for calibration and recovery studies.

Preconcentration and Determination of Trace Amount of Nickel in Water and Biological Samples by Dispersive Liquid‐Liquid Microextraction

AbstractA new, simple and highly sensitive dispersive liquid‐liquid microextraction method using a ionic liquid, i.e., 1‐Butyl‐3‐methylimidazolium hexafluorophosphate ([C4MIM][PF6]) for nickel determination at trace levels in real samples was developed. Nickel was chelated with diethyl dithiocarbamat reagent and extracted into an ionic liquid. Ni was back‐extracted from the IL phase with 200 μL of 0.5 mol L−1 nitric acid and determined by electrothermal atomic absorption spectrometry (ETAAS). Various parameters such as pH, amount of ionic liquid, eluent type and volume, chelating agent concentration, volume of the sample solution and matrix interference effect on the recovery of the metal ions have been studied. Under the optimum conditions, the enrichment factor 100 was obtained from only 20 mL of sample. The calibration graph was linear in the rage of 20‐700 ng L−1 of nickel with detection limit of 5 ng L−1. The relative standard deviation (R.S.D.s) for eight replicate measurements of 20 ng L−1 of nickel was 5.6%. Validation of the methodology was performed by standard addition method and analysis of certified reference material. The method was successfully applied to the determination of Ni+2 in serum and tap water samples.

Bacillus sp. immobilized on Amberlite XAD-4 resin as a biosorbent for solid phase extraction of thorium prior to UV-vis spectrometry determination

A method has been developed for the preconcentration of Th prior to its determination by UV-vis spectrophotometry after complexation with Arsenazo III. A column was packed with Amberlite XAD-4 resin containing immobilized Bacillus sp. as a solid phase extractant. Parameters such as pH of the solution and sample, the concentration of Th, the volume and type of eluent, flow rate and effect of matrix interference were studied. The optimum pH for the sorption of Th is 5.0, and quantitative eluation occurs with 1 mol L-1 HCl. The tolerance limits of some electrolytes were also studied. The loading capacity was determined to be 17.2 mg g−1. The method was applied to the determination of Th in real ore sample and validated by analyzing a certified reference samples (NCS DC-73350; poplar leaves).

Preconcentration of cadmium and nickel using the bioadsorbent Geobacillus thermoleovorans subsp. stromboliensis immobilized on Amberlite XAD-4

Cadmium and nickel ions have been preconcentrated on Geobacillus thermoleovorans subsp. stromboliensis, immobilized on Amberlite XAD-4, and were determined by flame atomic absorption spectrometry (FAAS). Parameters such as pH, amount of adsorbent, eluent type and volume, flow rate of solution and the matrix interference effect on retention have been studied, and extraction conditions were optimized. Elution of Cd(II) and Ni(II) from minicolumns was carried out with 1.0 M hydrochloric acid or nitric acid with recoveries from 97 to 100%. The sorption capacity is 0.0373 and 0.0557 mmol g−1 for Cd(II) and Ni(II), respectively. The detection limits were 0.24 μg L−1 for cadmium and 0.3 μg L−1 for nickel. The relative standard deviations of the procedure were below 10%. The procedure was validated by analyzing certified reference materials and applied to the determination of Cd(II) and Ni(II) in natural water and food samples.

Speciation analysis of As, Sb and Se in leachates of cementitious construction materials using selective solid phase extraction and ICP-MS

A solid phase extraction (SPE) method has been developed for the separation of As(III), Sb(III) and Se(IV) from As(V), Sb(V) and Se(VI) in leachates of cementitious construction materials. The leachates were treated with ammonium pyrrolidine dithiocarbamate (APDC) and the APDC complexes of As(III), Sb(III) and Se(IV) were retained on a non-polar (C-18) sorbent, whereas As(V), Sb(V) and Se(VI) passed through. The SPE method was optimized in a multivariate approach: the effect of sample pH, APDC concentration, mixing time and sample percolation rate on the extraction of the analyte species was studied, and the optimum conditions of the significant parameters, i.e. sample pH and APDC concentration, were identified and experimentally verified. The two oxidation states of the elements can be separated using the SPE method from solutions of pH 3–8 (As), pH 4–10 (Sb) and pH 3–9 (Se) treated with 0.08% (w/v) APDC. The effect of matrix interferences was studied and the use of benzene sulfonate to remove interfering matrix metal ions by ion-pair SPE was demonstrated. The limit of detection of As(V), Sb(V) and Se(VI) by ICP-MS was 0.09, 0.14 and 0.37 µg L−1, respectively. A condition was established for the preconcentration of As(III), Sb(III) and Se(IV) by elution with 3.0 M HNO3 in a back-flushing mode. With a preconcentration factor of 50, concentrations of As(III), Sb(III) and Se(IV) down to 1–6 ng L−1 could be detected using the SPE method in combination with ICP-MS. The SPE method was validated using spike recovery tests, and was used to determine the oxidation states of the target elements in leachates of a concrete material. As(V), Sb(V) and Se(VI) were found to be the major species in most of the leachates.

Sulfadiazine determination in pharmaceuticals by electrochemical reduction on a glassy carbon electrode

Sulfadiazine was quantified in two samples of pharmaceutical preparations by square-wave voltammetry. The analytical signal response was obtained by electrochemical reduction instead of oxidation of the sulfa drug at a glassy carbon electrode. The determination was carried out in 0.04 mol L-1 Britton-Robinson pH 6.8 buffer solution. Sulfadiazine reduction was observed at -1.49 V vs. Ag/AgCl in one well-resolved irreversible peak. The analytical curve was obtained in the concentration range of 62.7 to 340 µmol L-1 (r = 0.9986) with a detection limit of 10.9 µmol L-1. For one sample analyzed, recovery values were in the range of 94.9 to 101.1%, while for the other sample they were within 96.0 to 104.6%, indicating no matrix interference effects on the analytical results for both sulfadiazine samples. The accuracy of the electroanalytical method was compared to the standard amperometric titration method.

Electroanalytical determination of estriol hormone using a boron-doped diamond electrode

A boron-doped diamond (BDD) electrode was used for the electroanalytical determination of estriol hormone in a pharmaceutical product and a urine sample taken during pregnancy by square-wave voltammetry. The optimized experimental conditions were: (1) a supporting electrolyte solution of NaOH at a pH of 12.0, and (2) a frequency of 20 Hz, a pulse height of 30 mV and a scan increment of 2 mV (for the square-wave parameters). The analytical curve was linear in the concentration range of 2.0 x 10(-7) to 2.0 x 10(-5) mol L(-1) (r=0.9994), with a detection limit of 1.7 x 10(-7) mol L(-1) and quantification limit of 8.5 x 10(-7) mol L(-1). Recoveries of estriol were in the range of 98.6-101.0%, for the pharmaceutical sample, and 100.2-103.4% for the urine sample, indicating no significant matrix interference effects on the analytical results. The accuracy of the electroanalytical methodology proposed was compared to that of the radioimmunoassay method. The values for the relative error between the proposed and standard methods were -7.29% for the determination of estriol in the commercial product and -4.98% in a urine sample taken during pregnancy. The results obtained suggest a reliable and interesting alternative method for electroanalytical determination of estriol in pharmaceutical products and urine samples taken during pregnancy using a boron-doped diamond electrode.

Reducing glycerophosphocholine lipid matrix interference effects in biological fluid assays by using high‐turbulence liquid chromatography

Matrix interferences can severely affect quantitative assays of biological samples when electrospray ionization (ESI) is employed with liquid chromatography/tandem mass spectrometry (LC/MS/MS). A major source of matrix interferences for plasma sample analyses is the presence of glycerophosphocholine (GPCho) lipids. The efficiency of online high-turbulence liquid chromatography (HTLC) extraction for eliminating these lipids is evaluated and the interfering effects of endogenous lipids on human plasma assays are measured for pharmaceutical compounds having a wide variety of chemical properties. It is found that GPCho lipids, represented by 16:0, 18:1 and 18:0 LPC (lysophosphatidylcholine) and 16:0-18:2 PC, cause variations for hydrophobic compound analyses even when optimal online HTLC extraction conditions are employed. The efficiency for lipid removal depends on the organic content of the transfer solvent, but turbulent flow loading has no significant effect.

Electroanalytical determination of sulfadiazine and sulfamethoxazole in pharmaceuticals using a boron-doped diamond electrode

Abstract Two sulfonamides, namely sulfadiazine and sulfamethoxazole, were independently quantified in pharmaceutical products by square-wave voltammetry (SWV) using a boron-doped diamond (BDD) electrode. The electroanalytical determination of sulfadiazine was carried out in ethanol + 0.5 mol L −1 H 2 SO 4 50/50 (v/v) and of sulfamethoxazole in ethanol + pH 6.0 phosphate buffer 50/50 (v/v) solutions. Both analytes showed one well-resolved irreversible oxidation peak at around +1.1 V, which served as the analytical response. Calibration curves were obtained in the concentration ranges of 8.01 × 10 −6 to 1.19 × 10 −4 mol L −1 ( r = 0.9995) for sulfadiazine and 6.10 × 10 −6 to 6.01 × 10 −5 mol L −1 ( r = 0.9995) for sulfamethoxazole, with respective detection limits of 2.19 × 10 −6 and 1.15 × 10 −6 mol L −1 . For both sulfonamides, recovery values were in the range of 95–104% for all samples, indicating no matrix interference effects on the analytical results. The accuracy of the electroanalytical methodology reported herein was compared to the standard HPLC method, and the values for the relative error between the proposed and standard methods were −4.31% for sulfadiazine and −0.79% for sulfamethoxazole. The data suggest a potential and interesting alternative method for the electroanalytical determination of sulfa drugs in pharmaceuticals and other products.

Investigation of folic acid stability in fortified instant Asian noodles by use of capillary electrophoresis

A simple, rapid procedure, using capillary zone electrophoresis (CZE), that can efficiently measure added folic acid in fortified instant fried noodles has been developed and validated. Optimum separation of folic acid was obtained on a 72 cm × 75 μm capillary using 8 mM phosphate-12 mM borate run buffer with 5% MeOH at pH 9.5, temperature of 30 °C and voltage of 28 kV. The extracts were introduced into the capillary via electrokinetic injection and the folic acid monitored at 214 nm. For quantification purposes, nicotinic acid was added as internal standard to all samples. Under these conditions the analysis required approximately 12 min. Good results were obtained for different analytical parameters including linearity, accuracy and precision. The limit of detection was calculated to be 5.3 mg/L. Prior to CZE determination, noodle samples were homogenized in the buffer solution for 1 h followed by treatment with α-amylase solution for 1 h at 65 °C or protease solution for 4 h at 37 °C. The enzyme solution was added at a concentration of 25 mg/L and then adjusted to pH 7.0. Using standard addition to eliminate the effect of sample matrix interference, results showed that a higher and more efficient recovery of added folic acid could be obtained when using α-amylase. During the four main stages of instant fried noodle manufacturing (dough crumbs, cut sheets, steaming and frying) folic acid was found to be stable with recoveries of 96–103%.

Pulsed flow modulation comprehensive two-dimensional gas chromatography

Pulsed flow modulation (PFM) is based on higher flow rate time compression of the first GC column effluent, which prior to the injection into the second column is stored for a few seconds in a standard fused silica wide bore transfer line. We constructed the PFM device with two standard 1/16 in. brass compression fittings with the insertion of the two columns inside the wide bore 0.53 mm i.d. fused silica storage transfer line for the elimination of dead volumes. This simple arrangement provides a combination of flexibility in the length of the sample storage transfer line hence comprehensive two-dimensional gas chromatography (GC × GC) cycle time, inert sample path and full elimination of cooling gas consumption. A record short second column injection time of 20 ms is demonstrated. Practical injection times are the sample collection time (such as 4 s) divided by the second to first column flow rate ratio (such as 20/0.7), which is typically around 150 ms. Due to the low cost of the device it can also be considered for use with non comprehensive time segmented GC × GC to remove a few accidental coelutions. PFM-GC × GC excels with high second column capacity due to the use of 0.32 mm i.d. columns with high flow rates as the second dimension GC × GC column. As a result, PFM-GC × GC can have up to two orders of magnitude higher second column sample capacity and linear dynamic range for improved reduction of adverse matrix interference effects due to column overloading.

The use of Bacillus subtilis immobilized on Amberlite XAD-4 as a new biosorbent in trace metal determination

The present work proposes the use of Bacillus subtilis immobilized on Amberlite XAD-4 as new biosorbent in trace metal determination. The procedure is based on the biosorption of Cu and Cd ions on a column of Amberlite XAD-4 resin loaded with dried, dead bacterial components prior to their determination by flame AAS. Various parameters such as pH, amount of adsorbent, eluent type and volume, flow rate of solution and matrix interference effect on the retention of the metal ions have been studied. The optimum pH values of quantitative sorption for Cu and Cd were found to be 7.0 and 7.5, respectively. These metal ions can be desorbed with 1 M HCl (recovery, 96–100%). The sorption capacity of the resin was 0.0297 and 0.035 mmol g −1 for Cu 2+ and Cd 2+, respectively. The tolerance limit of some electrolytes were also studied. This procedure was applied to Cu 2+ and Cd 2+ determination in aqueous solutions, including river and well water systems. In order to evaluate the accuracy of the proposed procedure, the certified reference materials, NRCC-SLRS-4 Riverine water and LGC7162 Strawberry leaves were analyzed.