The compound-independent calibration of polybrominated diphenyl ethers isomers using gas chromatography-inductively coupled plasma mass spectrometry
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A simple, rapid and sensitive method for the determination of atorvastatin calcium in pharmaceutical preparations using two modified carbon paste electrodes was developed. One electrode (sensor A) is based on ion-pair of atorvastatin with 5,6-diaminouracil hydrochloride (ATS-DAUH) and the other (sensor B) is based on atorvastatin with picric acid (ATS-PC). Among three different solvent mediators tested, dioctylphthalate (DOPH) exhibited a proper behavior including Nernstian slopes of the calibration curve at 58.76 ± 0.8 and 57.48±1 mV per decade for sensors A and B. The response times were 10 and 12 s, detection limits 1.3 × 10−6 and 2.2 × 10−6 M; the concentration range 2.5 × 10−6-7.9 × 10−2 M and 3.0 × 10−6 to 7.9 × 10−2 M respectively. The present electrodes show good discrimination of atorvastatin calcium from several inorganic, organic ions, sugars and some common excipients. The sensors were applied for the determination of atorvastatin calcium in pharmaceutical preparations using standard addition and the calibration curve methods. The results obtained were satisfactory with excellent percentage recovery comparable and sometimes better than those obtained by other routine methods for the assay. The proposed potentiometric methods offer the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.
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Identification and quantification of human fingernail calcium is demonstrated by laser-induced breakdown spectroscopy (LIBS) using the modified external standardization. Since cow’s horn and hoof have structures very similar to the fingernail, either of them is individually selected as the matrix of standard samples. In total, 12 standard samples for each matrix are prepared using CaCO3 as the standard substance. In order to achieve accurate calibration curves associated with the method of modified external standard, foremost, the calcium concentration of each of matrices (horn and hoof) is determined by the method of standard additions. The results indicate that there exist 4887 µg/g (ppm) and 4156 µg/g (ppm) of calcium in the pure horn and hoof matrices, respectively. Then, the external calibration curves related to the two matrices are plotted using the information of standard samples. Finally, by the use of signals obtained from LIBS experiment for three different fingernails and inserting their amounts into the calibration curves, the calcium concentration of the fingernails under test is measured to be 10,814 µg/g (ppm), 13,106 µg/g (ppm) and 14,974 µg/g (ppm). The difference of the calcium concentrations between three specimens, as will be discussed, may be due to different physical conditions of people who have donated their fingernails.
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A new analytical procedure for the direct determination of metal impurities in aluminium oxide by ultrasonic slurry sampling–electrothermal vaporization–inductively coupled plasma mass spectrometry (ETV–ICP-MS) is reported. The elements studied include Cr, Cu, Ga, Fe, Mg, Mn, Na, V and Zn. Two samples of fine alumina powder (including the certified reference material NIST SRM 699) were used in this study without any additional pre-treatment. Analytical results of the external calibration using aqueous standards, the external calibration using matched matrix standards and the standard additions method are presented and compared. The most appropriate (average accuracy of 97±5.5% for sample NIST SRM 699) was the standard additions procedure of calibration. An acceptable agreement was found between the results of the slurry sampling procedure and the certified or reference values, and the repeatability of measurements was always better than 13.6%. Some other analytical figures-of-merit,e.g., limits of detection, are also presented. The absolute limits of detection (for the analysis of 15 µl samples) ranged from 0.8 to 8.3 pg. The speed and multi-element analytical potential of this technique seem to be very advantageous.
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The quantitation of target analytes in complex matrices such as biological samples requires special calibration approaches to compensate for additional capacity or activity in the matrix samples. A conventional calibration curve, obtained with standard solutions, is one of the most important calibration procedures for quantitation of target analytes in such matrices. However, these technique require a great number of reagents and material, and consume a considerable amount of time throughout the analysis. In this work, a new calibration procedure to analyze urine samples is proposed for the first time in chromatography procedures. The proposed calibration, called the addition calibration technique, was used for the determination of acetaminophen and hydrochlorothiazide in urine samples. The results obtained for the proposed calibration mode were compared to those obtained using standard addition and standard calibration techniques. The proposed addition calibration was validated by statistical studies between results obtained by the addition technique and conventional techniques, using the ANOVA test and linear regression. The results demonstrated good agreement among them. The performance of the analytical method was evaluated. Relative standard deviation, limit of detection, and limit of quantification are respectively 0.5–0.6%, 0.169–0.75 µg/mL, and 0.565–2.5 µg/mL. Linear range falls within the range of 0.3 to 63.8 µg/mL for both compounds. Accuracy ranged between 94% and 101%.
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OBJECTIVE To establish a rapid and accurate method for instantaneous analysis of Pb,Cd,As in blood by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). METHODS The assay method was established according to comparative study of standard curve method and standard addition curve method (a method derived and developed from standard addition method). RESULTS Both methods showed good correlative coefficients of calibration curve,limits of detection and reproducibilities for all test elements. Standard curve method,indicated unsatisfactory spiked recovery between 92.00% and 135.0%,as well as unacceptable determined values of reference materials (GBW09139e and GBW09140e). Standard addition curve method indicated satisfactory spiked recovery range from 93.33% to 102.0% and coincident contents of reference materials. CONCLUSION Standard addition curve method,bearing better spiked recovery and precise than those of standard curve method,was a rapid and accurate method for simultaneous determination of harmful elements in blood by ICP-MS.
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The standard solutions prepared by different methods to establish the amount of external standard calibration curve recovery compared to the preparation of acetone solvent matrix calibration curve standard solution of chlorpyrifos recovery is 92%to 99%.relative standard deviation(RSD)≤4.18%,chlorpyrifos in the 0.035～1.4 mg/L in the range a good linear relationship between the instrument detection limit of this method is 0.02 mg/L,the detection limit is 0.008 mg/kg.On the same sample by double flame photometric detector(FPD)detection, DB-1701+DG than the DB-1 column matrix effects a small column.Standard solution prepared by the solvent matrix to establish the amount of external standard calibration curve to eliminate matrix effects.
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In this study, a simple, fast and eco-friendly ultrasound-assisted-cloud point extraction method for extraction and pre-concentration of zinc, nickel and cobalt from vegetables and foods prior to their determination by flame atomic absorption spectrometry (FAAS) was proposed. Ultrasound energy was used to shorten extraction time and reduce steps needed or to improve selectivity. The method is based on complex formation of metal ions with carmine in presence of cationic surfactant at pH 5.0, and then extraction of their hydrophobic complexes into the micellar phase of Igepal CO-630 as extractant. After optimisation, calibration curves for Zn, Co and Ni were linear in the range of 2–120, 2–220 and 2–180 μg kg−1, respectively. Limits of detection, which is described as ratio of 3×standard deviation of 12 replicate measurements of blank analysis to slope of calibration curves, were 0.5, 0.6 and 0.6 μg kg−1 for Zn, Ni and Co, respectively. Relative standard deviations (RSDs%, n: 5) for 25 μg kg−1 of each analyte were less than 3.1%. The recovery rate was higher than 94% with a lower RSD than 3.1% for five replicate measurements of 25 μg kg−1 of each analyte. The accuracy was verified using two different standard reference materials (SRM 1570a-Trace elements in spinach leaves and SRM 1548a-Typical diet), and the results were in good agreement with the certified values. The method was applied to the determinations of Zn, Ni and Co in vegetables and foods by FAAS.
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