Influence Of Sample Matrix Research Articles

Novel approach for infrared spectroscopic quantitation of azithromycin in commercial tablets employing paracetamol as matrix modifier

The ATR-FTIR quantitation of azithromycin in three products of commercial tablets was carried out on product specific quantitative regression models using powdered paracetamol as matrix modifier to overcome the variation of spectral response and influence of sample matrix. For each product, a PLS quantitative regression model was established using training infrared spectra obtained from reference mixtures (reference powders with known mass content (%, w/w) of azithromycin mixed homogenously with paracetamol to have mass percentage of azithromycin over total mass of azithromycin and paracetamol (PA) from 30% to 70%). The spectral data were collected in wavenumber range depending on commercial product within the wavenumber zone from 1300 cm−1 to 1750 cm−1 to build quantitative regression models. To quantify azithromycin in any commercial batch of the same product, the homogenized sample powder was mixed with paracetamol to have mixtures with PA value about 50% to record infrared spectrum. The actual amount of azithromycin would then be calculated from spectral response of unknown sample and the pre-established quantitative regression model. Each quantitative regression model was validated according to the current requirements of ICH guideline Q2R1 and those of AOAC International in term of specificity, accuracy, precision, long-term robustness and reliability. The validation results proved that the quantitative regression models were accurate, precise, reliable and robust, able to provide quantitative results of azithromycin in tablets equivalent to those provided by official HPLC method of USP44.

Influence of Sample Matrix on Determination of Histamine in Fish by Surface Enhanced Raman Spectroscopy Coupled with Chemometric Modelling

Histamine fish poisoning is a foodborne illness caused by the consumption of fish products with high histamine content. Although intoxication mechanisms and control strategies are well known, it remains by far the most common cause of seafood-related health problems. Since conventional methods for histamine testing are difficult to implement in high-throughput quality control laboratories, simple and rapid methods for histamine testing are needed to ensure the safety of seafood products in global trade. In this work, the previously developed SERS method for the determination of histamine was tested to determine the influence of matrix effect on the performance of the method and to investigate the ability of different chemometric tools to overcome matrix effect issues. Experiments were performed on bluefin tuna (Thunnus thynnus) and bonito (Sarda sarda) samples exposed to varying levels of microbial activity. Spectral analysis confirmed the significant effect of sample matrix, related to different fish species, as well as the extent of microbial activity on the predictive ability of PLSR models with R2 of best model ranging from 0.722–0.945. Models obtained by ANN processing of factors derived by PCA from the raw spectra of the samples showed excellent prediction of histamine, regardless of fish species and extent of microbial activity (R2 of validation > 0.99).

Identification of N-methylaniline based on azo coupling reaction by combining TLC with SERRS

The objective of this study was to establish a novel method for the determination of N-methylaniline (NMA) based on azo coupling reaction in infant pacifiers prepared with food contact silicone materials by combining thin layer chromatography (TLC) with surface-enhanced resonance Raman scattering (SERRS). TLC was used to separate the azo reaction products to confirm the component spot of azo compound, then the spot of azo compound mixed with silver sol on the TLC plate was qualitatively detected by SERRS. The limit of detection (LOD) of the method is as low as 0.50 ppm for NMA. The influence of sample matrix about the TLC-SERRS detection of NMA was investigated by experiment of simulated positive sample, and the NMA in infant pacifiers exposed to silica gel products was detected. The method of TLC-SERRS for the determination of NMA in infant pacifiers prepared with food contact silicone materials was established, and the real samples were detected. Compared with the methods ever reported, the method has the advantages of high sensitivity, specificity and low cost. It provides a new reference method for establishing a safety system for food contact silicone materials.

The influence of sample matrix on the accuracy of nitrite N and O isotope ratio analyses with the azide method.

The isotope ratios of nitrogen (15 N/14 N) and oxygen (18 O/16 O) in nitrite (NO2 - ) can be measured by conversion of the nitrite into nitrous oxide (N2 O) with azide, followed by mass spectrometric analysis of N2 O by gas chromatography isotope ratio mass spectrometry (GC/IRMS). While applying this method to brackish samples, we noticed that the N and O isotope ratio measurements of NO2 - are highly sensitive to sample salinity and to the pH at which samples are preserved. We investigated the influence of sample salinity and sample preservation pH on the N and O isotope ratios of the N2 O produced from the reaction of NO2 - with azide. The N2 O isotope ratios were measured by GC/IRMS. Under the experimental reaction conditions, the conversion of NO2 - into N2 O was less complete in lower salinity solutions, resulting in respective N and O isotopic offsets of +2.5‰ and -14.0‰ compared with seawater solutions. Differences in salinity were also associated with differences in the fraction of O atoms exchanged between NO2 - and water during the reaction. Similarly, aqueous NO2 - samples preserved at elevated pH values resulted in the incomplete conversion of NO2 - into N2 O by azide, and consequent pH-dependent isotopic offsets, as well as differences in the fraction of O atoms exchanged with water. The addition of sodium chloride to the reaction matrix of samples and standards largely mitigated salinity-dependent isotopic offsets in the N2 O product, and nearly homogenized the fraction of O atom exchange among samples of different salinity. A test of the hypobromite-azide method to measure N isotope ratios of ammonium by conversion into NO2 - then N2 O revealed no influence of sample salinity on the N isotope ratios of the N2 O product. We outline recommendations to mitigate potential matrix effects among samples and standards, to improve the accuracy of N and O isotope ratios in NO2 - measured with the azide method.

L-lysine determination in animal feed using microbiological microtiter plate assay

Chromatographic methods are most commonly used for the analysis of amino acids; however, there is growing need for faster, simpler and more price-effective assays. In this paper, the applicability of a rapid microbiological assay for quantification of the total content of L-lysine in feed samples was evaluated. The assay relies on the dependency of bacterial growth of Pediococcus acidilactici on the presence of L-lysine. Microbiological microtiter plate assay method for the quantitative determination of total (added and natural) L-lysine in feed samples has been verified, and parameters such as accuracy, precision, limit of detection, and limit of determination were evaluated. Results of total L-lysine determination in different feed samples have been compared with results of validated HPLC method. The microbiological microtiter plate assay method can be employed as a qualitative and quantification method for total L-lysine determination with detection and determination limit of 0.040 % and 0.085 %, respectively. However, further research on the influence of sample matrix on the determination of low lysine levels is required.

Influence of sample matrix on the bioavailability of arsenic, cadmium and lead during co-contaminant exposure

In this study, the influence of sample matrix on the relative bioavailability of arsenic (As), cadmium (Cd) and lead (Pb) was assessed following exposure of C57BL/6 mice to spiked aged (12years) soils. AIN93G mouse chow was amended with individual and tertiary As, Cd and Pb soil combinations which were administered to mice over a 9day exposure period. Contaminant relative bioavailability was calculated by comparing As urinary excretion and Cd-kidney/Pb-liver accumulation to corresponding values for compounds used to derive the respective toxicity reference value. Strong linear dose-responses were observed for mice exposed to AIN93G mouse chow augmented with individually spiked soil with As, Cd and Pb. When mice were exposed to co-contaminants, As relative bioavailability (RBA) decreased similar to results from previous co-contaminant salt experiments presumably due to the influence of Cd on phosphate transport proteins, which are utilized for As absorption. However, a decrease in Cd-kidney and Pb-liver accumulation was also observed following co-co-exposure. It was postulated that this resulted from interactions with other (essential) metals (e.g. iron, aluminium, manganese, magnesium) within the soil matrix and their influence on absorption via divalent metal transporters.

Influence of sample matrix on the alkaline extraction of Cr(VI) in soils and industrial materials

An accurate and efficient determination of the highly toxic Cr(VI) in solid materials is important to determine the total Cr(VI) inventory of contaminated sites and the Cr(VI) release potential from such sites into the environment. Most commonly, total Cr(VI) is extracted from solid materials following a hot alkaline extraction procedure (US EPA method 3060A) where a complete release of water-extractable and sparingly soluble Cr(VI) phase is achieved. This work presents an evaluation of matrix effects that may occur during the hot alkaline extraction and in the determination of the total Cr(VI) inventory of variably composed contaminated soils and industrial materials (cement, fly ash) and is compared to water-extractable Cr(VI) results. Method validation including multiple extractions and matrix spiking along with chemical and mineralogical characterization showed satisfying results for total Cr(VI) contents for most of the tested materials. However, unreliable results were obtained by applying method 3060A to anoxic soils due to the degradation of organic material and/or reactions with Fe2+-bearing mineral phases. In addition, in certain samples discrepant spike recoveries have to be also attributed to sample heterogeneity. Separation of possible extracted Cr(III) by applying cation-exchange cartridges prior to solution analysis further shows that under the hot alkaline extraction conditions only Cr(VI) is present in solution in measurable amounts, whereas Cr(III) gets precipitated as amorphous Cr(OH)3(am). It is concluded that prior to routine application of method 3060A to a new material type, spiking tests are recommended for the identification of matrix effects. In addition, the mass of extracted solid material should to be well adjusted to the heterogeneity of the Cr(VI) distribution in the material in question.

Sweeping of hydrophobic amines under inhomogeneous electric field and low surfactant concentration in micellar electrokinetic chromatography.

The influence of sample matrix on sample sweeping in MEKC was examined in the presented manuscript. Significant focusing effect was observed for relatively hydrophobic cationic compounds (emetine, strychnine and quinine) using high ionic strength sample matrix (900 mM H3 PO4 /720 mM Tris) which conductivity was about ninefold higher than utilized BGE. Moreover, the results were obtained using BGE composed of comparatively low surfactant concentration (10 mM SDS) and 40 mM H3 PO4 /32 mM Tris buffer solution. About 200 to 300-fold preconcentration of analytes was reached with the presented method. Basing on experimental results and computer simulation using Simul5 software, hypothetical mechanism of observed phenomenon was proposed.

Determination of doxorubicin in plasma by using CE coupled with in‐column tapered optic‐fiber light‐emitting diode induced fluorescence detection

This paper proposes a novel strategy to enhance detection of doxorubicin in human plasma, using homemade CE combined with normal stacking mode (NSM). The detection system of CE named as in-column tapered optic-fiber light-emitting diode induced fluorescence detection system is economic and more sensitive that has been demonstrated in our previous work. The influence of sample matrix, BGE, applied voltage, and injection time on the efficiency of NSM were systematically investigated. The clean extracts were subjected to CE separation with optimal experimental conditions: Ethanol-water (1:1, v/v) was used as sample matrix, pH 4.12 15 mM sodium phosphate buffer solution containing 70% v/v ACN, applied voltage 23 kV and 45 s hydrodynamic injection at a height of 20 cm. The detection system displayed linear dynamic range from 6.4 to 1.13 × 10(3) ng/mL with a correlation coefficient of 0.9990 and LOD 2.2 ng/mL for doxorubicin (DOX). The proposed CE method has been successfully applied to determine DOX in human plasma which the recoveries of standard DOX added to human plasma were found to been the range of 93.8-104.6%. The results obtained demonstrate that our detection system combined with NSM is a good idea to enhance sensitivity in CE for routine determination of DOX in some biological specimens.

Evaluation of an isotope dilution liquid chromatography tandem mass spectrometry method for pharmaceuticals in fish

An isotope dilution liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was successfully developed and applied for analysis of 15 pharmaceuticals and 2 pharmaceutically active metabolites in fish tissues. This method relied on electrospray ionization (ESI), for which the influence of sample matrix on analyte ionization efficiencies remains a persistent challenge to environmental analysis. Statistically derived method detection limits (MDLs) for most analytes ranged from 1 to 10ng/g, independent of sample matrix, and were as low as 0.04ng/g for the most sensitive compounds in fillet tissue. MDLs for fish fillets were determined for both 10μL and 100μL injection volumes; however, results showed that detection limits did not scale linearly with injection volume. Direct comparison of spike recoveries from fish liver demonstrated that isotope dilution was superior to matrix-matched calibration in compensating for matrix interference. Spike recoveries for the isotope dilution approach generally ranged from 91 to 112%, independent of tissue (i.e., fillet or liver). The developed method was applied to examine target analytes in brown trout (Salmo trutta), collected upstream and downstream from a municipal effluent discharge to East Canyon Creek, Park City, UT, USA. Though no pharmaceuticals were detected in fish samples from the upstream location, 3 and 10 compounds (out of 17 target analytes) were detected in fish fillet and liver samples, respectively, from the downstream sampling site. Pharmaceuticals in fish fillets were observed at concentrations ranging from 0.14 to 12ng/g, while levels were markedly higher in liver tissues (range: 0.27–600ng/g).

세라믹, 금속 및 플라스틱 소재의 니켈 함유량 분석에 관한 연구

ICP-AES와 AAS를 이용하여 세라믹, 금속 및 플라스틱 소재에 함유된 니켈을 정량하기 위한 조건을 연구하였다. 니켈 정량을 위해 산분해하여 조제된 시험 용액을 직접 ICP-AES 또는 AAS로 분석할 때 철이나 크로뮴 등의 원소가 방해하므로, 니켈을 dimethylglyoxime으로 착화시키고 <TEX>$CHCl_3$</TEX>로 추출하여 방해원소로부터 분리한 후 <TEX>$CHCl_3$</TEX>을 제거하고 염산으로 용해하여 측정하였다. 니켈에 대한 측정 회수율이 우수하였고, 방해를 일으키는 매질원소를 효율적으로 제거할 수 있어 본 방법은 인증표준물질(BAM-376 및 PACS-2)에 대한 용매추출시험에서 matrix의 영향을 받지 않고 니겔을 정량할 수 있었다. Quantitative analytical condition for nickel in ceramic, metal and plastic materials using complexation and solvent extraction followed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectrophotometry (AAS) was studied. Ceramic, metal and plastic samples were dissolved by acid digestion. Nickel was determined by ICP-AES and AAS after extraction of Ni <TEX>$(DMG)_2$</TEX> in <TEX>$CHCl_3$</TEX>. Recovery efficiency of nickel was satisfactory, and most of matrix elements causing interference could be effectively eliminated by the separation. Nickel in the certified reference materials (BAM-376 and PACS-2) were quantitatively determined without influence of sample matrix.

구리를 함유한 탄소소재의 납 및 카드뮴 분석에 관한 연구

Quantitative analytical condition for lead and cadmium in copper contained carbon materials using solvent extraction followed by inductively coupled plasma-atomic emission spectrometry was studied. Copper contained carbon samples were dissolved by nitric acid-perchloric acid digestion. Lead and cadmium were determined after separation with KCN masked copper by an dithizone-chloroform solvent extraction. Recovery efficiency of analyte elements was satisfactory, and most of matrix elements causing interference could be effectively eliminated by the separation. Lead and cadmium were quantitatively determined without influence of sample matrix, by applying it procedure to artifact sample.

&lt;b&gt;Determination of trace amounts of zinc by flame atomic absorption spectrometry after separation and preconcentration onto modified natural analcime zeolite loaded 2,3,5,6-tetra(2-pyridyl)pyrazine&lt;/b&gt;

Zinc ions were separated by solid phase extraction onto modified natural analcime zeolite loaded with 2,3,5,6-tetra(2-pyridyl)pyrazine (TPPZ). Extraction efficiency and the influence of sample matrix, flow rate, pH, and type and minimum amount of stripping eluent were investigated. Solutions of zinc ions were passed through a glass column packed with 1.0 g of the sorbent at pH range of 3.8-4.4. The adsorbed zinc ions were eluted with 5.0 mL of 2.0 M HNO3 at a flow rate of 1.0 mL min-1. The calibration curve using the preconcentration system was linear from 0.05 to 2.0 µg mL-1 in final solution with a correlation coefficient of 0.9991. The relative standard deviation (RSD) for eight replicate determinations at 0.5 µg mL -1 zinc was ± 0.92%. Detection limit was 2.9 ng mL-1 in final solution and preconcentration factor was 170. The proposed method was successfully applied to the determination of zinc in various standard and water samples.KEY WORDS: Zinc determination, Solid-phase extraction, Analcime zeolite, Preconcentration, 2,3,5,6-Tetra(2-pyridyl)pyrazine Bull. Chem. Soc. Ethiop. 2010, 24(1), 127-132.

Determination of Ultratrace Amounts of Ce3 in the Presence of Sm3, La3, Dy3, and Yb3 in Water and Soils by Inductively Coupled Plasma-Optical Emission Spectroscopy After Preconcentration with Thio-Functionalized MCM-41 at Controlled pH

A method is presented for the selective preconcentration and determination of ultratrace amounts of Ce3+ ions by inductively coupled plasma-optical emission spectroscopy in the presence of Sm3+, La3+, Dy3+, Yb3+, and common interfering ions. In this method, thio-functionalized MCM-41 is used in the preconcentration step. Extraction efficiency and the influence of sample matrix, pH of sample solution, type and minimum amount of tripping acid, and flow rates were investigated. The preconcentration is pH-dependent, and the best results were obtained in the pH range of 8.5-10.3. The maximum capacity of 2 mg absorbent was found to be 170 +/- 4 microg. The detection limit of the measurements after the preconcentration step was found to be 114 ng Ce3+/L.

Influence of sample matrix and storage on BNP measurement on the Bayer Advia Centaur

The assessment and management of congestive heart failure relies increasingly on the measurement of B-type natriuretic peptide (BNP). However, the effective contribution of this biochemical test in the clinical decision making is influenced by reliability of the measure, which also depends on several preanalytical issues. Since there is controversy on the influence of the matrix and the storage conditions on BNP measurement, we compared results of BNP in serum, K2 ethylene diamine tetra-acetic acid (EDTA) plasma and lithium heparin plasma fresh samples and in matching samples stored at -20 and -80 degrees C for 1 week. BNP measured on the Bayer Advia Centaur was systematically underestimated in heparin plasma (-47%) and serum (-62%) when compared to K2 EDTA plasma. According to the established 100 ng/L cutoff value, 25% and 37% of the fresh samples collected in heparin plasma or serum were misclassified from the reference K2 EDTA fresh specimen, respectively. When compared to the fresh specimens, the mean and interindividual bias observed for samples stored at either -20 degrees C or -80 degrees C was, overall, modest for K2 EDTA plasma (-2%) and heparin plasma (+6% and -4%, respectively), though it appeared clinically meaningful in serum (+47% and +28%, respectively). Although we can not rule out that other BNP assays using different antibodies may be not affected from degradation during storage to the same extent, results of our investigation demonstrate that K2 EDTA plasma is the most suitable specimens for BNP testing on fresh and frozen samples stored at either -20 degrees C or -80 degrees C for up to 1 week.

Application of ion-exchange cartridge clean-up in food analysis: VI. Determination of six penicillins in bovine tissues by liquid chromatography–electrospray ionization tandem mass spectrometry

A multiresidue analytical method was developed for the quantification of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine tissues using liquid chromatography– electrospray ionization tandem mass spectrometry (LC–ESI MS/MS) with a multiple reaction monitoring technique. Using the deuterated PCG and NFPC as internal standard was effective for improvement of repeatability and accuracy. We chose [M − H-141] − as a monitor ion of MRM analysis and [M − H] − as a precursor ion for each penicillin. Combination of an ion-exchange cartridge clean-up and ion-pair LC enable us to determine the residual penicillins using the standard curves made from standard solutions without the influence of sample matrix on the MS. The average recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from bovine liver, kidney and muscle at the same concentrations as the tolerance levels of PCG (50 μg/kg) ranged from 77 to 101% with the coefficients of variation ranging from 0.7 to 4.2% ( n=5). The limits of quantification for the six penicillins were 2–10 μg/kg in bovine muscle, liver and kidney (S/N ratio >10).

Ultra-trace monitoring of copper in environmental and biological samples by inductively coupled plasma atomic emission spectrometry after separation and preconcentration by using octadecyl silica membrane disks modified by a new schiff's base

Ultra-trace amounts of Cu(II) were separated and preconcentrated by solid phase extraction on octadecyl-bonded silica membrane disks modified with a new Schiff,s base (Bis- (2-Hydroxyacetophenone) -2,2-dimethyl-1,3-propanediimine) (SBTD) followed by elution and inductively coupled plasma atomic emission spectrometric detection. The method was applied as a separation and detection method for copper(II) in environmental and biological samples. Extraction efficiency and the influence of sample matrix, flow rate, pH, and type and minimum amount of stripping acid were investigated. The concentration factor and detection limit of the proposed method are 500 and 12.5 pg mL-1, respectively.

Ultratrace determination of lead, cadmium and copper in environmental and biological samples by atomic absorption spectrometry after their separation and preconcentration using octadecyl silica membrane disks modified with a new n–s schiff base

Pb(II), Cd(II) and Cu(II) ions were separated and preconcentrated by solid-phase extraction on octadecyl-bonded silica membrane disks modified with a new S–N-containing Schiff base (bis-2-thiophenal propandiamine) (BTPD) followed by elution and atomic absorption spectrometric detection. The method was applied as a separation and detection method for lead(II), cadmium(II) and copper(II) in environmental and biological samples. Extraction efficiency and the influence of sample matrix, flow rate, pH, and type and minimum amount of stripping acid were investigated. The maximum capacity of the membrane disks modified by 4 mg of BTPD was found to be 668 ± 10, 480 ± 8 and 454 ± 7 µg of lead, cadmium and copper, respectively. The limit of detection of the proposed method is 0.25, 0.01 and 0.02 ng/mL for lead, cadmium and copper, respectively.

Determination of nelfinavir free drug concentrations in plasma by equilibrium dialysis and liquid chromatography/tandem mass spectrometry: important factors for method optimization

A method was developed and validated for measuring the free fraction of nelfinavir in plasma employing equilibrium dialysis for the separation of free (unbound) drug and liquid chromatography/tandem mass spectrometry for quantitation. Nelfinavir, widely used to treat HIV infection, is a highly bound HIV protease inhibitor with the fraction bound in plasma being greater than 98%. Thus variations in the free fraction may be clinically important when interpreting total drug concentrations. Optimization of the method was carried out considering the influence of sample matrix and physicochemical and absorptive properties of nelfinavir. Nelfinavir free fraction averaged 0.41±0.094, 0.43±0.087 and 0.41±0.063% at nelfinavir plasma concentrations of 1000, 2000 and 3000 ng/ml, respectively. Free nelfinavir concentrations were underestimated with this assay by ∼25% because of unavoidable losses to adsorption. However, the adsorptive loss was reproducible and consistent across the concentration range of the assay. Within-day and between-day precisions ranged from 6.0 to 9.4% and 15.2 to 27.3%, respectively. The lower limit of quantitation of the unbound concentration of nelfinavir was 1.0 ng/ml, permitting analysis of samples with total concentrations of nelfinavir in plasma that are ≥400 ng/ml. This developed method proves reproducible and sensitive and its application to patient plasma samples is also reported.

SEPARATION AND PRE-CONCENTRATION OF TRACE AMOUNTS OF CERIUM(III) ON OCTADECYL SILICA MEMBRANE DISCS MODIFIED WITH 1,3,5-TRITHIACYCLOHEXANE AND ITS SPECTROPHOTOMETRIC DETERMINATION BY ARSENAZO(III)

A simple and reliable method for rapid and selective separation and determination of trace amounts of Ce3+ ions from aqueous samples using octadecyl-bonded silica membrane discs modified with 1,3,5-trithiacyclohexane (TTCH) and spectrophotometry with arsenazo(III) is presented. Extraction efficiency and the influence of sample matrix, pH of sample solution, type and minimum amount of stripping acid, and flow-rates were investigated. The maximal capacity of the membrane discs modified with 15 mg of TTCH was found to be 547 μg of cerium. The limit of detection of the proposed method is 2 ng/mL. The effects of various cationic interferences on the percent recovery of cerium in binary mixtures were studied. The method was applied to the recovery of Ce3+ ions from synthetic samples.