Anal Chem Insights [JOURNAL]
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109 papers
Conductimetric biosensor for the detection of uric Acid by immobilization uricase on nata de coco membrane-pt electrode.
Mulyasuryani A, Srihardiastutie A
Anal Chem Insights · 2011 · PMID 21792276 · Full text
A conductimetric enzyme biosensor for uric acid detection has been developed. The uricase, as enzyme, is isolated from Candida utilis and immobilized on a nata de coco membrane-Pt electrode. The biosensor demonstrates a...
A conductimetric enzyme biosensor for uric acid detection has been developed. The uricase, as enzyme, is isolated from Candida utilis and immobilized on a nata de coco membrane-Pt electrode. The biosensor demonstrates a linear response to urate over the concentration range 1-6 ppm and has good selectivity properties. The response is affected by the membrane thickness and pH change in the range 7.5-9.5. The response time is three minutes in aqueous solutions and in human serum samples. Application of the biosensor to the determination of uric acid in human serum gave results that compared favourably with those obtained by medical laboratory. The operational stability of the biosensor was not less than three days and the relative error is smaller than 10%.
New spectrophotometric method for determining nitrogen dioxide in air using 2,2-azino-bis(3-ethyl benzothiazoline)-6-sulfonic acid-diammonium salt and passive sampling.
Salem AA, Soliman AA, El-Haty IA
Anal Chem Insights · 2011 · PMID 21760708 · Full text
A new simple and highly sensitive spectrophotometric method for determining nitrogen dioxide in air was developed. The method is based on converting atmospheric nitrogen dioxide to nitrite ions within the IVL passive sam...
A new simple and highly sensitive spectrophotometric method for determining nitrogen dioxide in air was developed. The method is based on converting atmospheric nitrogen dioxide to nitrite ions within the IVL passive samplers used for samples collection. Acidifying nitrite ions with concentrated HCl produced the peroxynitrous acid oxidizing agent which was measured using 2, 2-azino-bis(3-ethyl benzothiazoline)-6-sulfonic acid-diammonium salt (ABTS) as reducing coloring agent. A parallel series of collected samples were measured for its nitrite content using a validated ion chromatographic method.The results obtained using both methods were compared in terms of their sensitivity and accuracy. Developed spectrophotometric method was shown to be one order of magnitude higher in sensitivity compared to the ion chromatographic method. Quantitation limits of 0.05 ppm and 0.55 μg/m(3) were obtained for nitrite ion and nitrogen dioxid, respectively. Standard deviations in the ranges of 0.05-0.59 and 0.63-7.92 with averages of 0.27 and 3.11 were obtained for determining nitrite and nitrogen dioxide, respectively.Student-t test revealed t-values less than 6.93 and 4.40 for nitrite ions and nitrogen dioxide, respectively. These values indicated insignificant difference between the averages of the newly developed method and the values obtained by ion chromatography at 95% confidence level.Compared to continuous monitoring techniques, the newly developed method has shown simple, accurate, sensitive, inexpensive and reliable for long term monitoring of nitrogen dioxide in ambient air.
The effect of varying short-chain alkyl substitution on the molar absorptivity and quantum yield of cyanine dyes.
Chapman G, Henary M, Patonay G
Anal Chem Insights · 2011 · PMID 21760707 · Full text
The effect of varying short-chain alkyl substitution of the indole nitrogens on the spectroscopic properties of cyanine dyes was examined. Molar absorptivities and fluorescence quantum yields were determined for a set of...
The effect of varying short-chain alkyl substitution of the indole nitrogens on the spectroscopic properties of cyanine dyes was examined. Molar absorptivities and fluorescence quantum yields were determined for a set of pentamethine dyes and a set of heptamethine dyes for which the substitution of the indole nitrogen was varied. For both sets of dyes, increasing alkyl chain length resulted in no significant change in quantum yield or molar absorptivity. These results may be useful in designing new cyanine dyes for analytical applications and predicting their spectroscopic properties.
Low level determinations of methyl methanesulfonate and ethyl methanesulfonate impurities in emtricitabine active pharmaceutical ingredient by LC/MS/MS using electrospray ionization.
Kakadiya PR, Chandrashekhar TG, Ganguly S … +2 more , Singh DK, Singh V
Anal Chem Insights · 2011 · PMID 21760706 · Full text
Alkyl methanesulfonates have been highlighted as potential genotoxic impurities (PGIs). A sensitive LC/MS/MS method was developed and validated for the determination of Alkyl methanesulfonate impurities in Emtricitabine...
Alkyl methanesulfonates have been highlighted as potential genotoxic impurities (PGIs). A sensitive LC/MS/MS method was developed and validated for the determination of Alkyl methanesulfonate impurities in Emtricitabine API (active pharmaceutical ingredient). LC/MS/MS method on Zorbax SB C(18) column (150 × 4.6 mm i.d.), 3.5 μm, with electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode was used. The proposed method was specific, linear, accurate, rugged and precise. The calibration curves showed good linearity over the concentration range of 0.0025 μg/ml to 0.3 μg/ml the correlation coefficient was >0.999 in each case. Method had very low limit of detection (LOD) and limit of quantification (LOQ) as 0.3 μg/g and 0.4 μg/g respectively for both the analytes. Accuracy was observed within 80%-120% for both the analytes. This method can be further extended a good quality control tool for low level quantitation of Alkyl methanesulfonate impurities in other API.
A validated reverse phase HPLC method for the determination of disodium EDTA in meropenem drug substance with UV-detection using precolumn derivatization technique.
Narola B, Singh AS, Mitra M … +2 more , Santhakumar PR, Chandrashekhar TG
Anal Chem Insights · 2011 · PMID 21760705 · Full text
This paper deals with development and validation of a high performance liquid chromatographic method for the quantitative determination of disodium EDTA (Ethylenediaminetetraacetic acid) in Meropenem active pharmaceutica...
This paper deals with development and validation of a high performance liquid chromatographic method for the quantitative determination of disodium EDTA (Ethylenediaminetetraacetic acid) in Meropenem active pharmaceutical ingredient (API). EDTA was derivatized with Ferric chloride solution by heating at 70 °C in water bath for about 20 minutes and the chromatographic separation achieved by injecting 100 μL of the derivatized mixture into a Waters HPLC system with photodiode array detector using a Phenomenex Luna C18(2) column (250 × 4.6 mm), 5 μ. The mobile phase consisting of 5% methanol and 95% of 0.7 g/L solution of Tetra butyl ammonium bromide and 4.6 g/L solution of sodium acetate trihydrate in water (pH adjusted to 4.0 with the help of acetic acid glacial) and a flow rate of 1 milliliter/minute. EDTA eluted at approximately 6 minutes. The method was suitably validated with respect to specificity, linearity of response, precision, accuracy, ruggedness, stability in analytical solution, limit of quantitation and detection and robustness for its intended use.
Determination of Trace Amounts of Lead Using the Flotation-spectrophotometric method.
Shiri S, Delpisheh A, Haeri A … +3 more , Poornajaf A, Golzadeh B, Shiri S
Anal Chem Insights · 2011 · PMID 30543271 · Full text
The present study describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of extremely low concentrations of lead. It is based on flotation of a complex of Pb...
The present study describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of extremely low concentrations of lead. It is based on flotation of a complex of Pb ions and Alizarin yellow between aqueous and -hexane interface at pH = 6. The proposed procedure is also applied for determination of lead in both tap water and prepared sea water samples. Beer's Law was obeyed over the concentration range of 3.86 × 10 To 8.20 × 10 molL (8-170 ngmL) with an apparent molar absorptivity of 1.33 × 10 molL cm for a 100 mL aliquot of the water sample. The detection limit (n = 10) was 8.7 × 10 molL (1.0 ngmL) and the Relative standard deviation (R.S.D), (n = 10) for 7.2 × 10 molL (150 ngmL) of Pb (II) was 4.36%. A notable advantage of the method is that the determination of Pb (II) is free from the interference of almost all cations and ions found in the environment and waste water samples. The determination of Pb (II) in tap and synthetic seawater samples was also carried out by the present method. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples.
Floatation-spectrophotometric Determination of Thorium, Using Complex Formation with Eriochrome Cyanine R.
Shiri S, Delpisheh A, Haeri A … +3 more , Poornajaf A, Khezeli T, Badkiu N
Anal Chem Insights · 2011 Jan · PMID 21340019 · Full text
A novel and sensitive floatation-spectrophotometric method is presented for determination of trace amounts of thorium in water samples. The method is based on the ion-associated formation between thorium, Eriochrome cyan...
A novel and sensitive floatation-spectrophotometric method is presented for determination of trace amounts of thorium in water samples. The method is based on the ion-associated formation between thorium, Eriochrome cyanine R and Brij-35 at pH = 4 media. The complex was floated in the interface of the aqueous phase and n-hexane by vigorous shaking. After removing the aqueous phase the floated particles were dissolved in methanol and the absorbance was measured at 607 nm. The influence of different important parameters such as Eriochrome cyanine R and surfactants concentration, pH, volume of n-hexane, standing time and interfering ions were evaluated. Under optimized conditions the calibration graph was linear in the range of 6-230 ng mL(-1) of thorium with a correlation coefficient of 0.9985. The limit of detections (LOD), based on signal to noise ratio (S/N) of 3 was 1.7 ng mL(-1). The relative standard deviations for determination of 150 and 30 ng ml(-1) of thorium were 3.26 and 4.41%, respectively (n = 10). The method showed a good linearity, recoveries, as well as some advantages such as sensitivity, simplicity, affordability and a high feasibility. The method was successfully applied to determine thorium in different water and urine samples.
Determination of Trace Amounts of Lead Using the Flotation-spectrophotometric method.
Shiri S, Delpisheh A, Haeri A … +3 more , Poornajaf A, Golzadeh B, Shiri S
Anal Chem Insights · 2010 Dec · PMID 21234287 · Full text
The present study describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of extremely low concentrations of lead. It is based on flotation of a complex of Pb(...
The present study describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of extremely low concentrations of lead. It is based on flotation of a complex of Pb(2+) ions and Alizarin yellow between aqueous and n-hexane interface at pH = 6. The proposed procedure is also applied for determination of lead in both tap water and prepared sea water samples. Beer's Law was obeyed over the concentration range of 3.86 × 10(-8) To 8.20 × 10(-7) molL(-1) (8-170 ngmL(-1)) with an apparent molar absorptivity of 1.33 × 10(6) molL(-1) cm(-1) for a 100 mL aliquot of the water sample. The detection limit (n = 10) was 8.7 × 10(-9) molL(-1) (1.0 ngmL(-1)) and the Relative standard deviation (R.S.D), (n = 10) for 7.2 × 10(-7) molL(-1) (150 ngmL(-1)) of Pb (II) was 4.36%. A notable advantage of the method is that the determination of Pb (II) is free from the interference of almost all cations and ions found in the environment and waste water samples. The determination of Pb (II) in tap and synthetic seawater samples was also carried out by the present method. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples.
A Validated Stability-indicating Reverse Phase HPLC Assay Method for the Determination of Memantine Hydrochloride Drug Substance with UV-Detection Using Precolumn Derivatization Technique.
Narola B, Singh AS, Santhakumar PR … +1 more , Chandrashekhar TG
Anal Chem Insights · 2010 Jul · PMID 20703320 · Full text
This present paper deals with the development and validation of a stability indicating high performance liquid chromatographic method for the quantitative determination of Memantine hydrochloride. Memantine hydrochloride...
This present paper deals with the development and validation of a stability indicating high performance liquid chromatographic method for the quantitative determination of Memantine hydrochloride. Memantine hydrochloride was derivatized with 0.015 M 9-fluorenylmethyl chloroformate (FMOC) and 0.5 M borate buffer solution by keeping it at room temperature for about 20 minutes and the chromatographic separation achieved by injecting 10 muL of the derivatized mixture into a Waters HPLC system with photodiode array detector using a kromasil C18 column (150 x 4.6 mm), 5 mu. The mobile phase consisting of 80% acetonitrile and 20% phosphate buffer solution and a flow rate of 2 milliliter/minute. The Memantine was eluted at approximately 7.5 minutes. The volume of FMOC used in derivatization, concentration of FMOC and derivatization time was optimized and used. Forced degradation studies were performed on bulk sample of Memantine hydrochloride using acid (5.0 Normal (N) hydrochloric acid), base (1.0 N sodium hydroxide), oxidation (30% hydrogen peroxide), thermal (105 degrees C), photolytic and humidity conditions. The developed LC method was validated with respect to specificity, precision (% RSD about 0.70%), linearity (linearity of range about 70-130 mug/mL), ruggedness (Overall % RSD about 0.35%), stability in analytical solution (Cumulative % RSD about 0.11% after 1450 min.) and robustness.
Cell-free expression of protein kinase a for rapid activity assays.
Leippe DM, Zhao KQ, Hsiao K … +1 more , Slater MR
Anal Chem Insights · 2010 May · PMID 20520741 · Full text
Functional protein analysis often calls for lengthy, laborious in vivo protein expression and purification, and can be complicated by the lack of stability of the purified protein. In this study, we demonstrate the feasi...
Functional protein analysis often calls for lengthy, laborious in vivo protein expression and purification, and can be complicated by the lack of stability of the purified protein. In this study, we demonstrate the feasibility of a simplified procedure for functional protein analysis on magnetic particles using cell-free protein synthesis of the catalytic subunit of human cAMP-dependent protein kinase as a HaloTag((R)) fusion protein. The cell-free protein synthesis systems provide quick access to the protein of interest, while the HaloTag technology provides efficient, covalent protein immobilization of the fusion protein, eliminating the need for further protein purification and minimizing storage-related stability issues. The immobilized cPKA fusion protein is assayed directly on magnetic beads and can be used in inhibitor analyses. The combination of rapid protein synthesis and capture technologies can greatly facilitate the process of protein expression and activity screening, and therefore, can become a valuable tool for functional proteomics studies.
A modified method for determination of lumefantrine in human plasma by HPLC-UV and combination of protein precipitation and solid-phase extraction: application to a pharmacokinetic study.
Huang L, Lizak PS, Jayewardene AL … +3 more , Marzan F, Lee MN, Aweeka FT
Anal Chem Insights · 2010 Mar · PMID 20448843 · Full text
An HPLC-UV method was developed and validated for the determination of lumefantrine in human plasma. Lumefantrine and its internal standard halofantrine were extracted from plasma samples using protein precipitation with...
An HPLC-UV method was developed and validated for the determination of lumefantrine in human plasma. Lumefantrine and its internal standard halofantrine were extracted from plasma samples using protein precipitation with acetonitrile (0.2% perchloric acid) followed by solid-phase extraction with Hypersep C(8) cartridges. Chromatographic separation was performed on a Zorbax SB-CN HPLC column (3.0 x 150 mm, 3.5 microm) with water/methanol (0.1% TFA) as the mobile phases in a gradient elution mode. Detection was performed using UV/vis detector at lambda = 335 nm. The method showed to be linear over a range of 50-10,000 ng/mL with acceptable intra- and inter-day precision and accuracy. The mean recoveries were 88.2% for lumefatrine and 84.5% for the I.S. The internal standard halofantrine is readily available from commercial sources. This method was successfully applied to a pharmacokinetic interaction study between a first-line antimalarial combination (artemether-lumefantrine) and antiretroviral therapy.
Liquid chromatography with post-column reagent addition of ammonia in methanol coupled to negative ion electrospray ionization tandem mass spectrometry for determination of phenoxyacid herbicides and their degradation products in surface water.
Raina R, Etter ML
Anal Chem Insights · 2010 Feb · PMID 20212919 · Full text
A new liquid chromatography (LC)-negative ion electrospray ionization (ESI(-))-tandem mass spectrometry (MS/MS) method with post-column addition of ammonia in methanol has been developed for the analysis of acid herbicid...
A new liquid chromatography (LC)-negative ion electrospray ionization (ESI(-))-tandem mass spectrometry (MS/MS) method with post-column addition of ammonia in methanol has been developed for the analysis of acid herbicides: 2,4-dichlorophenoxy acetic acid, 4-chloro-o-tolyloxyacetic acid, 2-(2-methyl-4-chlorophenoxy)butyric acid, mecoprop, dichlorprop, 4-(2,4-dichlorophenoxy) butyric acid, 2,4,5-trichlorophenoxy propionic acid, dicamba and bromoxynil, along with their degradation products: 4-chloro-2-methylphenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol and 3,5-dibromo-4-hydroxybenzoic acid. The samples were extracted from the surface water matrix using solid-phase extraction (SPE) with a polymeric sorbent and analyzed with LC ESI(-) with selected reaction monitoring (SRM) using a three-point confirmation approach. Chromatography was performed on a Zorbax Eclipse XDB-C18 (50 x 4.6 mm i.d., 1.8 mum) with a gradient elution using water-methanol with 2 mM ammonium acetate mobile phase at a flow rate of 0.15 mL/min. Ammonia in methanol (0.8 M) was added post-column at a flow rate of 0.05 mL/min to enhance ionization of the degradation products in the MS source. One SRM transition was used for quantitative analysis while the second SRM along with the ratio of SRM1/SRM2 within the relative standard deviation determined by standards for each individual pesticide and retention time match were used for confirmation. The standard deviation of ratio of SRM1/SRM2 obtained from standards run on the day of analysis for different phenoxyacid herbicides ranged from 3.9 to 18.5%. Limits of detection (LOD) were between 1 and 15 ng L(-1) and method detection limits (MDL) with strict criteria requiring <25% deviation of peak area from best-fit line for both SRM1 and SRM2 ranged from 5 to 10 ng L(-1) for acid ingredients (except dicamba at 30 ng L(-1)) and from 2 to 30 ng L(-1) for degradation products. The SPE-LC-ESI(-) MS/MS method permitted low nanogram-per-liter determination of pesticides and degradation products for surface water samples.
Using a Matlab implemented algorithm for UV-vis spectral resolution for pKa determination and multicomponent analysis.
Gonen Y, Rytwo G
Anal Chem Insights · 2009 Dec · PMID 20072668 · Full text
A Matlab implemented computer code for spectral resolution is presented. The code enables the user to resolve the UV-visible absorption spectrum of a mixture of up to 3 previously known components, to the individual comp...
A Matlab implemented computer code for spectral resolution is presented. The code enables the user to resolve the UV-visible absorption spectrum of a mixture of up to 3 previously known components, to the individual components, thus, evaluating their quantities. The resolving procedure is based on searching the combination of the components which yields the spectrum which is the most similar (minimal RMSE) to the measured spectrum of the mixture. Examples of using the software for pK(a) value estimation and multicomponent analysis are presented and other implementations are suggested.
Micelle enhanced fluorimetric and thin layer chromatography densitometric methods for the determination of (+/-) citalopram and its S-enantiomer escitalopram.
Taha EA, Salama NN, Wang S
Anal Chem Insights · 2009 Apr · PMID 19652757 · Full text
Two sensitive and validated methods were developed for determination of a racemic mixture citalopram and its enantiomer S-(+) escitalopram. The first method was based on direct measurement of the intrinsic fluorescence o...
Two sensitive and validated methods were developed for determination of a racemic mixture citalopram and its enantiomer S-(+) escitalopram. The first method was based on direct measurement of the intrinsic fluorescence of escitalopram using sodium dodecyl sulfate as micelle enhancer. This was further applied to determine escitalopram in spiked human plasma, as well as in the presence of common and co-administrated drugs. The second method was TLC densitometric based on various chiral selectors was investigated. The optimum TLC conditions were found to be sensitive and selective for identification and quantitative determination of enantiomeric purity of escitalopram in drug substance and drug products. The method can be useful to investigate adulteration of pure isomer with the cheap racemic form.
Uncertainty analysis of drug concentration in pharmaceutical mixtures.
Savva M
Anal Chem Insights · 2008 Jun · PMID 19690634
Using a Taylor expansion to first order, a novel method was developed to calculate the uncertainty of drug concentration in pharmaceutical dosage forms. The method allows, in principle, calculation of the maximum potenti...
Using a Taylor expansion to first order, a novel method was developed to calculate the uncertainty of drug concentration in pharmaceutical dosage forms. The method allows, in principle, calculation of the maximum potential error in drug concentration in a mixture composed of an infinite number of ingredients that are measured on multiple balances of variable sensitivity requirements.
Quantitative mass spectrometric analysis of ropivacaine and bupivacaine in authentic, pharmaceutical and spiked human plasma without chromatographic separation.
Salama NN, Wang S
Anal Chem Insights · 2008 May · PMID 19652756 · Full text
The present study employs time of flight mass and bupivacaine in authentic, pharmaceutical and spiked human plasma as well as in the presence of their impurities 2,6-dimethylaniline and alkaline degradation product. The...
The present study employs time of flight mass and bupivacaine in authentic, pharmaceutical and spiked human plasma as well as in the presence of their impurities 2,6-dimethylaniline and alkaline degradation product. The method is based on time of flight electron spray ionization mass spectrometry technique without preliminary chromatographic separation and makes use of bupivacaine as internal standard for ropivacaine, which is used as internal standard for bupivacaine. A linear relationship between drug concentrations and the peak intensity ratio of ions of the analyzed substances is established. The method is linear from 23.8 to 2380.0 ng mL(-1) for both drugs. The correlation coefficient was >or=0.996 in authentic and spiked human plasma. The average percentage recoveries in the ranges of 95.39%-102.75% was obtained. The method is accurate (% RE < 5%) and reproducible with intra- and inter-assay precision (RSD% < 8.0%). The quantification limit is 23.8 ng mL(-1) for both drugs. The method is not only highly sensitive and selective, but also simple and effective for determination or identification of both drugs in authentic and biological fluids. The method can be applied in purity testing, quality control and stability monitoring for the studied drugs.
New spectrofluorimetric method with enhanced sensitivity for determination of paroxetine in dosage forms and plasma.
Darwish IA, Amer SM, Abdine HH … +1 more , Al-Rayes LI
Anal Chem Insights · 2008 Nov · PMID 19609398 · Full text
New simple spectrofluorimetric method with enhanced sensitivity has been developed and validated for the determination of the antidepressant paroxetine (PXT) in its dosage forms and plasma. The method was based on nucleo...
New simple spectrofluorimetric method with enhanced sensitivity has been developed and validated for the determination of the antidepressant paroxetine (PXT) in its dosage forms and plasma. The method was based on nucleophilic substitution reaction of PXT with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole in an alkaline medium (pH 8) to form a highly fluorescent derivative that was measured at 545 nm after excitation at 490 nm. The factors affecting the reaction was carefully studied and optimized. The kinetics of the reaction was investigated, and the reaction mechanism was presented. Under the optimized conditions, linear relationship with good correlation coefficient (0.9993) was found between the fluorescence intensity and PXT concentration in the range of 80-800 ng ml(-1). The limits of detection and quantitation for the method were 25 and 77 ng ml(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 3%. The proposed method was successfully applied to the determination of PXT in its pharmaceutical tablets with good accuracy; the recovery values were 100.2 +/- 1.61%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to the previously reported spectrofluorimetric method for determination of PXT in terms of its higher sensitivity and wider linear range. The high sensitivity of the method allowed its successful application to the analysis of PXT in spiked human plasma. The proposed method is practical and valuable for its routine application in quality control and clinical laboratories for analysis of PXT.
Use of Fourier Transform Infrared (FTIR) spectroscopy to study cadmium-induced changes in Padina tetrastromatica (Hauck).
D'Souza L, Devi P, Shridhar DM … +1 more , Naik CG
Anal Chem Insights · 2008 Oct · PMID 19609397
The aim of this study is to adopt the approach of metabolic fingerprinting through the use of Fourier Transform Infrared (FTIR) technique to understand changes in the chemical structure in Padina tetrastromatica (Hauck)....
The aim of this study is to adopt the approach of metabolic fingerprinting through the use of Fourier Transform Infrared (FTIR) technique to understand changes in the chemical structure in Padina tetrastromatica (Hauck). The marine brown alga under study was grown in two different environmental conditions; in natural seawater (P. tetrastromatica (c)) and in seawater suplemented with 50 ppm of cadmium (P. tetrastromatica (t)) for a three-week period in the laboratory. The second derivative, IR specrum in the mid-infrared region (4000-400 cm(-1)) was used for discriminating and identifying various functional groups present in P. tetrastromatica (c). On exposure to Cd, P. tetrastromatica (t) accumulated 412 ppm of Cd and showed perturbation in the band structure in the mid-IR absorption region. Variation in spectral features of the IR bands of P. tetrastromatica (untreated and treated) suggests that cadmium ions bind to hydroxyl, amino, carbonyl and phosphoryl functionalities. This was attributable to the presence of the following specific bands. A band at 3666 cm(-1) in untreated P. tetrastromatica (c) while a band at 3560 cm(-1) in Cd-treated P. tetrastromatica (t) due to non bonded and bonded O-H respectively. Similarly, non bonded N-H for P. tetrastromatica (c) showed two bands at 3500 cm(-1) and 3450 cm(-1) due to the N-H stretching vibrations and a band at 1577 cm(-1) due to N-H bending vibrations, while an intense band at 3350 cm(-1) due to bonded N-H stretching vibrations and at 1571 cm(-1) due to bending vibrations was observed for Cd-treated P. tetrastromatica (t). Involvement of ester carbonyl group is characterized by the presence of a band at 1764 cm(-1) in untreated P. tetrastromatica (c) while the Cd-treated P. tetrastromatica (t) showed the band at 1760 cm(-1). The intensity of the band at 1710 cm(-1) in the control samples decreased drastically after cadmium treatment indicating carbonyl of COOH to be involved in metal chelation. A band at 1224 cm(-1) for untreated P. tetrastromatica (c) and at 1220 cm(-1) for Cd-treated P. tetrastromatica (t) is indicative of the involvement of phosphoryl group in metal binding. Several other such changes were also evident and discussed in this paper. Based on our observation, FTIR technique proves to be an efficient tool for detecting structural changes and probable binding sites induced by the presence of a metal pollutant, cadmium, in the marine environment.
Palm-based standard reference materials for iodine value and slip melting point.
Tarmizi AH, Lin SW, Kuntom A
Anal Chem Insights · 2008 Sep · PMID 19609396 · Full text
This work described study protocols on the production of Palm-Based Standard Reference Materials for iodine value and slip melting point. Thirty-three laboratories collaborated in the inter-laboratory proficiency tests f...
This work described study protocols on the production of Palm-Based Standard Reference Materials for iodine value and slip melting point. Thirty-three laboratories collaborated in the inter-laboratory proficiency tests for characterization of iodine value, while thirty-two laboratories for characterization of slip melting point. The iodine value and slip melting point of palm oil, palm olein and palm stearin were determined in accordance to MPOB Test Methods p3.2:2004 and p4.2:2004, respectively. The consensus values and their uncertainties were based on the acceptability of statistical agreement of results obtained from collaborating laboratories. The consensus values and uncertainties for iodine values were 52.63 +/- 0.14 Wijs in palm oil, 56.77 +/- 0.12 Wijs in palm olein and 33.76 +/- 0.18 Wijs in palm stearin. For the slip melting points, the consensus values and uncertainties were 35.6 +/- 0.3 degrees C in palm oil, 22.7 +/- 0.4 degrees C in palm olein and 53.4 +/- 0.2 degrees C in palm stearin. Repeatability and reproducibility relative standard deviations were found to be good and acceptable, with values much lower than that of 10%. Stability of Palm-Based Standard Reference Materials remained stable at temperatures of -20 degrees C, 0 degrees C, 6 degrees C and 24 degrees C upon storage for one year.
Comparison of gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry with electron ionization and negative-ion chemical ionization for analyses of pesticides at trace levels in atmospheric samples.
Raina R, Hall P
Anal Chem Insights · 2008 Sep · PMID 19609395 · Full text
A comparison of detection limits of gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) with gas chromatography-tandem mass spectrometry (GC-MS/MS) in selected reaction monitoring (SRM) mode wit...
A comparison of detection limits of gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) with gas chromatography-tandem mass spectrometry (GC-MS/MS) in selected reaction monitoring (SRM) mode with both electron ionization (EI) and negative-ion chemical ionization (NCI) are presented for over 50 pesticides ranging from organochlorines (OCs), organophosphorus pesticides (OPs) and pre-emergent herbicides used in the Canadian prairies (triallate, trifluralin, ethalfluralin). The developed GC-EI/SIM, GC-NCI/SIM, and GC-NCI/SRM are suitable for the determination of pesticides in air sample extracts at concentrations <100 pg microL(-1) (<100 pg m(-3) in air). No one method could be used to analyze the range of pre-emergent herbicides, OPs, and OCs investigated. In general GC-NCI/SIM provided the lowest method detection limits (MDLs commonly 2.5-10 pg microL(-1)) along with best confirmation (<25% RSD of ion ratio), while GC-NCI/SRM is recommended for use where added selectivity or confirmation is required (such as parathion-ethyl, tokuthion, carbofenothion). GC-EI/SRM at concentration <100 pg microL(-1) was not suitable for most pesticides. GC-EI/SIM was more prone to interference issues than NCI methods, but gave good sensitivity (MDLs 1-10 pg microL(-1)) for pesticides with poor NCI response (OPs: sulfotep, phorate, aspon, ethion, and OCs: alachlor, aldrin, perthane, and DDE, DDD, DDT).
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