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At least 19 recordsLinked to original sources

PubMed1995

Multilayer peroxidase-labeled antibody method: comparison with labeled streptavidin-biotin method, avidin-biotin-peroxidase complex method, and peroxidase-antiperoxidase method.

A new, extremely sensitive, "multilayer peroxidase-labeled antibody method" is introduced. This method utilizes peroxidase-labeled antibodies that immuno-react with their antigen, but also can be an antigen to other peroxidase-labeled antibodies. An example of this method is: use rabbit IgG as the first antibody, peroxidase-labeled goat antirabbit IgG as the second antibody, peroxidase-labeled rabbit antigoat IgG as the third antibody, peroxidase-labeled goat antirabbit IgG as the fourth antibody, and peroxidase-labeled rabbit antigoat IgG as the fifth antibody in succession. We compared the sensitivities of this multilayer peroxidase-labeled antibody method with that of commercially available immuno-peroxidase staining kits, i.e., avidin-biotin-complex method and peroxidase-antiperoxidase method, both by immunostaining and enzyme-linked immunosorbent assay. The generated signal and background in immunostained sections were determined by a computer-assisted image analyzer and by enzyme-linked immunosorbent assay spectrophotometrically. It was found that a maximum signal/background ratio was obtained with those sections reacted with the first four antibodies in succession by the multilayer peroxidase-labeled antibody method, and those reacted with the five antibodies in succession by the multilayer peroxidase-labeled antibody method in the enzyme-linked immunosorbent assay. Thus, the multilayer peroxidase-labeled antibody method is more sensitive than the avidin-biotin-complex method and the peroxidase-antiperoxidase method.

Animals↗

PubMedDate not supplied

Comparison of the compact dry TC method with the standard pour plate method (AOAC official method 966.23) for determining aerobic colony counts in food samples: Performance-tested method.

Compact Dry TC qualifies as a rapid method kit for determining aerobic colony counts in foods. The plates are presterilized and contain culture medium and a cold-soluble gelling agent. The medium is rehydrated by inoculating 1 mL diluted sample into the center of the self-diffusible medium and allowing the solution to diffuse by capillary action. The plates can then be incubated and the colonies counted without any additional steps. The Compact Dry TC method was validated with 5 different raw meats. The performance tests were conducted at 35 degrees and 30 degrees C. In all required performance studies, no apparent differences were observed between the Compact Dry TC method and the Standard Pour Plate method (AOAC Official Method 966.23) for the detection level of aerobic microorganisms. For the accuracy claim (n = 60), a correlation factor of r2(35) = 0.9977 (35 degrees C) and r2(30) = 0.9932 (30 degrees C) could be assigned, as stated in the application for "Performance Tested Method." Quality consistency and storage robustness studies, showed no significant variations in plate count results with different production lots or plates of diverse storage age.

Bacteria, Aerobic↗

PubMed1995

Error analysis of autoradiography method for measurement of cerebral blood flow by 123I-IMP brain SPECT: a comparison study with table look-up method and microsphere model method.

N-isopropyl-p-[123I]iodoamphetamine (IMP) has been commonly used as a cerebral blood flow tracer, but, significant clearance of IMP from the brain to the blood causes underestimation of cerebral blood flow (CBF) as compared with true CBF when the conventional microsphere model method is applied. Previously, we reported an "Autoradiography method" (ARG method) for measuring CBF by using IMP in which this clearance effect was corrected. This method was based on a two-compartment model (influx: K1, efflux: k2, K1/k2 = distribution volume of IMP (Vd)), the K1 (corresponding to CBF) being obtained form the table which showed a correlation between CBF and the brain counts of SPECT scan with a constant Vd value. Arterial input data used were obtained by one point blood sampling 10 min after IMP infusion against the standard input function. In the present study, the ARG method was compared with the table look-up method (TLU method) and the conventional microsphere model method (MS method) for 30 subjects. When the Vd value in the ARG method was assumed to be 50 ml/ml, CBF values obtained by the ARG method were correlated well with those obtained by the TLU method (Y = 1.04X-2.5; X: TLU, Y: ARG r = 0.97) and those obtained by the MS method (Y = 0.82X + 12.1; X: ARG, Y: MS, r = 0.84). But, when the Vd value was assumed to be more or less than 50 ml/ml, ARG method CBF were under- or overestimated compared with the TLU method. This indicated that the ARG method could be a reliable method for CBF measurement if the Vd was determined properly. CBF values obtained by the MS method were actually 13.2% higher than those obtained by the ARG method against previous studies. As reasons for this, errors in the effects of gray-white matter mixture in the ARG method and in estimation of the SPECT brain counts at 8 min in the MS method were considered.

Amphetamines↗

PubMed1995

Accuracy and applicability of measurement of the scoliotic angle at the frontal plane by Cobb's method, by Ferguson's method and by a new method.

A new method for the measurement of scoliotic curves in antero-posterior (AP) radiographs is presented, in which the centre of the surface image of the vertebral bodies of the apical and two end vertebrae of the curvature are defined on the basis of geometric principles. Measurements using the Cobb, the Ferguson, and the new method were performed on ten AP radiographs from each of three groups of young patients with right convex thoracic idiopathic scoliosis with Cobb angles of between 7 and 15 degrees, 16 and 45 degrees and 46 and 80 degrees, respectively. Measurements using the Cobb method yielded significantly higher values than measurements using either the Ferguson method or the new method. In curves with Cobb angles of between 7 and 15 degrees, the values using Ferguson's method were significantly lower than those using the new method; the difference increased significantly in curves with a Cobb angle of 16 degrees or more. The level of significance of the intra- and interobserver differences between the new, the Cobb and the Ferguson methods was significantly higher in curves with a Cobb angle of 16 degrees or more. It is argued that measures of the scoliotic angle obtained by the new method are of greater clinical relevance than those obtained by the two other methods. Unlike the Cobb method, the new method takes into consideration the translation of the apical vertebra in relation to the end vertebrae and not only the tilt of the end vertebrae of the curve. As compared to the Ferguson method, the new method is based on standardised geometric principles, and is not influenced by changes in the shape of the vertebral body. Moreover, the repeatability of the new method is greater than that of both the Cobb method and the Ferguson method. Therefore, it is believed that the new method provides a more accurate measure of the scoliotic curve than do the two other methods, and it is to be preferred over the other two methods in longitudinal evaluation of the development of the curve.

Adolescent↗

PubMed1994

A comparison study of the EF-18 agar/Hydrophobic Grid Membrane Filter (HGMF) method and the enzyme linked antibody (ELA)/HGMF method to the HPB standard method in the isolation of Salmonella.

As part of a comparative and collaborative study of rapid methods for the detection of Salmonella and the standard Health Protection Branch (HPB) method, six Federal and Provincial Laboratories compared the EF-18 agar/Hydrophobic Grid Membrane Filters (HGMF) method to the standard HPB method. Two Federal Laboratories also compared the enzyme linked antibody (ELA)/HGMF method (which is a further development of the EF-18 agar/HGMF method) to the standard method. During this study the false-negative rates ranged from 0% to 15% for the standard HPB method, from 5.88% to 43.5% for the EF-18 agar/HGMF method, and from 0% to 10.5% for the ELA/HGMF method. The EF-18 agar/HGMF method did not compare well with the standard HPB method due to the number of false-negatives. Problems with this method resulted from the inability to isolate colonies of Salmonella on the HGMF due to the small colony size, abnormal colony coloration, and overgrowth by competitors. The ELA/HGMF method, however, was shown to be comparable to the standard HPB method. The main advantages of this method are that the antibody-staining step is independent of colony coloration and carbohydrate utilization on the plating media; the ability to detect some unusual strains of Salmonella irrespective of their atypical reactions on the media; and the ELA staining can indicate the presence of Salmonella even when the HGMF is overgrown by competitors. Also, cultural confirmation can proceed simultaneously yet independently of the ELA staining procedure. The data presented here indicate that this method is worth further study.

Bacteriological Techniques↗

PubMed2002

Recovery of Listeria monocytogenes from vacuum-sealed packages of frankfurters: comparison of the U.S. Department of Agriculture (USDA) food safety and inspection service product composite enrichment method, the USDA Agricultural Research Service (ARS) product composite rinse method, and the USDA-ARS package rinse method.

This study compared three methods for the recovery of Listeria monocytogenes from commercially prepared and vacuum-packaged frankfurters that were inoculated with a five-strain mixture of this pathogen at averages of 22 and 20,133 CFU per package over three trials. The presence and levels of the pathogen were determined by (i) the U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) product composite enrichment method, involving the selective enrichment of a 25-g composite of product and the subsequent plating of this product onto selective agar plates; (ii) the USDA Agricultural Research Service (ARS) product composite rinse method, involving the rinsing of a 25-g composite of product with 0.1% peptone water and the subsequent plating of a portion of the rinse fluid directly onto selective agar plates; and (iii) the USDA-ARS package rinse method, involving the use of 25 ml of 0.1% peptone water to rinse the entire contents of a package and the subsequent plating of a portion of the rinse fluid directly onto selective agar plates. For packages inoculated with 20,133 CFU. L. monocytogenes was recovered at a frequency (percentage of packages positive) of 100% by each of the three methods. The pathogen was recovered at efficiencies (percentages of recovery of L. monocytogenes) of 43 and 94% with the USDA-ARS product rinse method and the USDA-ARS package rinse method, respectively. For packages inoculated with 22 CFU, L. monocytogenes was recovered at frequencies of 17, 10, and 100% by the USDA-FSIS product composite enrichment method, the USDA-ARS product composite rinse method, and the USDA-ARS package rinse method, respectively. The pathogen was recovered at efficiencies of 20 and 95% with the USDA-ARS product composite rinse method and the USDA-ARS package rinse method, respectively. In a related study, the USDA-ARS package rinse method was the only method that detected the pathogen in 60 packages from each of five brands of frankfurters purchased from local grocery stores. These data establish that the USDA-ARS package rinse method is markedly more sensitive, as well as demonstrably more rapid and facile, than either the approved USDA-FSIS product composite enrichment method or the USDA-ARS product composite rinse method in determining the presence or absence of L. monocytogenes and establishing the levels of the pathogen that may be on the surface of ready-to-eat foods such as frankfurters.

Animals↗

PubMedDate not supplied

[Results of two methods for testing bacterial susceptibility to antibiotics: disk method and a new semi-automatic method in liquid medium (ABACR procedure) and comparison with the minimal inhibitory concentration (author's transl)].

A performance analysis was established between three methods for testing of bacterial susceptibility to sixteen antibiotics: agar dilution or minimal inhibitory concentration (MIC) method, agar diffusion or DISK method, and semi-automatic dilution in liquid medium or ABACR method. Precision of the three methods was determined using three reference strains in repetition experiments (9 repetitions for MIC, 60 repetitions for both DISK and ABAC). The results show that MIC method was the most precise, and that the precision of DISK and ABAC methods was not sifnificantly different. Fidelity of both DISK and ABAC methods was compared in taking as reference the MIC of 200 wild strains of Gram-negative bacteria. Omitting the data concerning trimethoprim-sulfamethozoaxol, the results were found concordant between DISK and MIC methods in 68.6 percent of the cases, between ABAC and MIC methods in 73.6 percent, and between ABAC and DISK methods in 68.9 percent. With regard to MIC, ABAC method gave results slightly better than those of DISK method, especially for five antibiotics: gentamicin, minocyclin, doxycylin, chloramphenicol and polymyxin B. So, the ABAC method looks very interesting for a semi-automatic routine method in testing bacterial susceptibility to antibiotics.

Anti-Bacterial Agents↗

PubMed2005

Efficient methods for finding transition states in chemical reactions: comparison of improved dimer method and partitioned rational function optimization method.

A combination of interpolation methods and local saddle-point search algorithms is probably the most efficient way of finding transition states in chemical reactions. Interpolation methods such as the growing-string method and the nudged-elastic band are able to find an approximation to the minimum-energy pathway and thereby provide a good initial guess for a transition state and imaginary mode connecting both reactant and product states. Since interpolation methods employ usually just a small number of configurations and converge slowly close to the minimum-energy pathway, local methods such as partitioned rational function optimization methods using either exact or approximate Hessians or minimum-mode-following methods such as the dimer or the Lanczos method have to be used to converge to the transition state. A modification to the original dimer method proposed by [Henkelman and Jonnson J. Chem. Phys. 111, 7010 (1999)] is presented, reducing the number of gradient calculations per cycle from six to four gradients or three gradients and one energy, and significantly improves the overall performance of the algorithm on quantum-chemical potential-energy surfaces, where forces are subject to numerical noise. A comparison is made between the dimer methods and the well-established partitioned rational function optimization methods for finding transition states after the use of interpolation methods. Results for 24 different small- to medium-sized chemical reactions covering a wide range of structural types demonstrate that the improved dimer method is an efficient alternative saddle-point search algorithm on medium-sized to large systems and is often even able to find transition states when partitioned rational function optimization methods fail to converge.

Journal Article↗

PubMed1993

[Comparative study of two methods of holding premature infants: the kangaroo method versus the traditional method].

This study compared two methods of holding preterm infants: 1) the kangaroo, or skin-to-skin method (K) and 2) the traditional method, or normal handling (T). Skin temperature, heart rate, respiratory rate and oxygen saturation were monitored during both the kangaroo and the traditional handling methods. After testing with the two methods, the mothers indicated their satisfaction and preference. Sixty-one pairs of mothers and babies were tested once with the K method and once with the T method. The first method tested was determined at random: 50% began with K and 50% with T. Skin temperature, heart rate and respiratory rate were similar with both K and T methods. Whereas oxygen saturation was significantly lower (92.8% vs 90.5%, p < 0.0001) under the T method, time of testing was longer (29.5 min vs 25.3 min, p = 0.02) for the K method than for T method. In summary, the findings suggested that mothers preferred the K method because the cold stress factor was avoided, oxygenation was better maintained, and mothers felt closer to their infants.

Adolescent↗

PubMedDate not supplied

Performance of a proposed determinative method for p-TSA in rainbow trout fillet tissue and bridging the proposed method with a method for total chloramine-T residues in rainbow trout fillet tissue.

Chloramine-T is an effective drug for controlling fish mortality caused by bacterial gill disease. As part of the data required for approval of chloramine-T use in aquaculture, depletion of the chloramine-T marker residue (para-toluenesulfonamide; p-TSA) from edible fillet tissue of fish must be characterized. Declaration of p-TSA as the marker residue for chloramine-T in rainbow trout was based on total residue depletion studies using a method that used time consuming and cumbersome techniques. A simple and robust method recently developed is being proposed as a determinative method for p-TSA in fish fillet tissue. The proposed determinative method was evaluated by comparing accuracy and precision data with U.S. Food and Drug Administration criteria and by bridging the method to the former method for chloramine-T residues. The method accuracy and precision fulfilled the criteria for determinative methods; accuracy was 92.6, 93.4, and 94.6% with samples fortified at 0.5X, 1X, and 2X the expected 1000 ng/g tolerance limit for p-TSA, respectively. Method precision with tissue containing incurred p-TSA at a nominal concentration of 1000 ng/g ranged from 0.80 to 8.4%. The proposed determinative method was successfully bridged with the former method. The concentrations of p-TSA developed with the proposed method were not statistically different at p < 0.05 from p-TSA concentrations developed with the former method.

Animals↗

PubMed1998

[Regional cerebral blood flow measurements by a noninvasive microsphere method using 123I-IMP: comparison with the modified fractional uptake method and the continuous arterial blood sampling method].

A noninvasive microsphere method using N-isopropyl-p-[123I]iodoamphetamine (123I-IMP), developed by Yonekura et al., was performed in 10 patients with neurological diseases to quantify regional cerebral blood flow (rCBF). Regional CBF values by this method were compared with rCBF values simultaneously estimated from both the modified fractional uptake (FU) method using cardiac output developed by Miyazaki et al. and the conventional method with continuous arterial blood sampling. In comparison, we designated the factor which converted raw SPECT voxel counts to rCBF values as a CBF factor. A highly significant correlation (r = 0.962, p < 0.001) was obtained in the CBF factors between the present method and the continuous arterial blood sampling method. The CBF factors by the present method were only 2.7% higher on the average than those by the continuous arterial blood sampling method. There were significant correlation (r = 0.811 and r = 0.798, p < 0.001) in the CBF factor between modified FU method (threshold for estimating total brain SPECT counts; 10% and 30% respectively) and the continuous arterial blood sampling method. However, the CBF factors of the modified FU method showed 31.4% and 62.3% higher on the average (threshold; 10% and 30% respectively) than those by the continuous arterial blood sampling method. In conclusion, this newly developed method for rCBF measurements was considered to be useful for routine clinical studies without any blood sampling.

Adult↗

PubMed2002

The Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM): a review of the ICCVAM test method evaluation process and current international collaborations with the European Centre for the Validation of Alternative Methods (ECVAM).

Over the last decade, national authorities in the USA and Europe have launched initiatives to validate new and improved toxicological test methods. In the USA, the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and its supporting National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) were established by the Federal Government to work with test developers and Federal agencies to facilitate the validation, review, and adoption of new scientifically sound test methods, including alternatives that can refine, reduce, and replace animal use. In Europe, the European Centre for the Validation of Alternative Methods (ECVAM) was established to conduct validation studies on alternative test methods. Despite differences in organisational structure and processes, both organisations seek to achieve the adoption and use of alternative test methods. Accordingly, both have adopted similar validation and regulatory acceptance criteria. Collaborations and processes have also evolved to facilitate the international adoption of new test methods recommended by ECVAM and ICCVAM. These collaborations involve the sharing of expertise and data for test-method workshops and independent scientific peer reviews, and the adoption of processes to expedite the consideration of test methods already reviewed by the other organisation. More recently, NICEATM and ECVAM initiated a joint international validation study on in vitro methods for assessing acute systemic toxicity. These collaborations are expected to contribute to accelerated international adoption of harmonised new test methods that will support improved public health and provide for reduced and more-humane use of laboratory animals.

Animal Testing Alternatives↗

PubMed2003

Comparison of methods for determination of glomerular filtration rate: Tc-99m-DTPA renography, predicted creatinine clearance method and plasma sample method.

BACKGROUND: The gamma camera uptake method with Tc-99m-DTPA is simple and less time consuming for the determination of the glomerular filtration rate (GFR). However, its diagnostic accuracy is debated. Gates' method and predicted creatinine clearance method were compared with plasma clearance method with Tc-99m-DTPA for the measurement of GFR. MATERIALS AND METHODS: Tc-99m-DTPA renography was performed on 133 patients (69 males and 64 females; age range being 24 to 84 years) with a wide range of renal function. The GFR was determined simultaneously by 3 methods; (1) gamma camera uptake method (modified Gates, Gates); (2) predicted creatinine clearance method (Cockcroft-Gault, CG); (3) single- or two-plasma clearance method (plasma sample clearance method, PSC). The PSC was chosen as a reference. RESULTS: The regression equation of the Gates and the CG against the PSC was Y = 11.89 + 1.041X (r = 0.790, p < 0.001, RMSE = 23.55 ml/min/1.73 m2) and Y = 8.845 + 0.7899X (r = 0.8270, p < 0.001, RMSE = 16.27 ml/min/1.73 m2), respectively. In comparison with the GFR by PSC, the Gates tended to overestimate the GFR, and contrarily the CG tended to underestimate the GFR. CONCLUSION: The Gates correlates well with the PSC. However, the Gates is even less precise than the CG. The Gates' method in Tc-99m-DTPA renography is not suitable for the estimation of GFR in routine practice.

Adult↗

PubMed2006

Which method should be the reference method to evaluate the severity of rheumatic mitral stenosis? Gorlin's method versus 3D-echo.

INTRODUCTION: Several studies have shown a wide variability among different methods to determine the valve area in patients with rheumatic mitral stenosis. Our aim was to evaluate if 3D-echo planimetry is more accurate than the Gorlin method to measure the valve area. METHODS: Twenty-six patients with mitral stenosis underwent 2D and 3D-echo echocardiographic examinations and catheterization. Valve area was estimated by different methods. A median value of the mitral valve area, obtained from the measurements of three classical non-invasive methods (2D planimetry, pressure half-time and PISA method), was used as the reference method and it was compared with 3D-echo planimetry and Gorlin's method. RESULTS: Our results showed that the accuracy of 3D-echo planimetry is superior to the accuracy of the Gorlin method for the assessment of mitral valve area. CONCLUSIONS: We should keep in mind the fact that 3D-echo planimetry may be a better reference method than the Gorlin method to assess the severity of rheumatic mitral stenosis.

Adult↗

PubMedDate not supplied

Single cuff comparison of two methods for indirect measurement of arterial blood pressure: standard auscultatory method versus automatic oscillometric method.

With the introduction of automatic oscillometric systems for indirect measurement of arterial blood pressure (e.g. DINAMAP), the problem of correspondence between that method and the standard auscultatory method arose. For an exact and valid comparison of two methods, for physiological and methodological reasons, both measurements have to be performed simultaneously and using only one single cuff. Applying a methodological approach fulfilling these preconditions and offering in addition the advantage of a graphic documentation of the individual measurement cycles, we were able to investigate both methods in a sample of 216 comparative experiments. We found a mean difference (auscultatory method minus oscillometric method) between the methods (bias) of -0.82 mm Hg (-0.109 kPa) for systolic pressure, 1.25 mm Hg (0.166 kPa) for diastolic pressure and 1.00 mm Hg (0.133 kPa) for mean pressure. Except for systolic pressure, the differences were statistically significant (paired t-test and analysis of variance). We also obtained a significant negative correlation between the differences and the average of both pressure values (decreasing error with increasing pressure) and a significant negative correlation between differences and heart rate (decreasing differences with increasing heart rate). The conclusions drawn from the comparative study are that, although the oscillometric method exhibited a tendency to higher systolic and lower diastolic measurement values compared to the auscultatory method, both methods are well comparable and the differences are below the level of physiological and clinical significance.

Blood Pressure Determination↗

PubMed2000

Performance evaluation of a method for the determination of bromate in drinking water by ion chromatography (EPA method 317.0) and validation of EPA method 324.0.

The potential carcinogenic nature of bromate has prompted global regulatory agencies, and industrial and academic institutions to publish several methods for the analysis of bromate in both drinking and bottled waters. The United States Environmental Protection Agency (EPA) has reported two methods capable of detecting bromate at or below the promulgated maximum contaminant level of 10.0 microg/l. These methods are EPA Method 300.1 and 317.0. Method 300.1 has been promulgated by EPA for compliance monitoring of bromate under Stage 1 of the Disinfectants/Disinfection By-Products Rule. Due to its sensitivity, selectivity and simplicity, Method 317.0 has been drafted and evaluated for potential use as a future compliance monitoring method. This manuscript describes the performance evaluation work with Method 317.0 and efforts completed at EPA's Technical Support Center that improved the sensitivity of Method 317.0, leading to the development of EPA Method 324.0

Bromates↗

PubMed2002

Analysis methods of polysorbate 20: A new method to assess the stability of polysorbate 20 and established methods that may overlook degraded polysorbate 20.

PURPOSE: Polysorbate 20 is a commonly used excipient in biopharmaceutical formulations, some of which may have an enzymatic activity. The action(s) of polysorbate 20 in biopharmaceutical formulations as a stabilizer require this surfactant to maintain its intact structure. This manuscript evaluates a new analytic method for the analysis of polysorbate 20 degradation in the format of a biopharmaceutical formulation and makes a comparison with several established methods of analysis. METHODS: Polysorbate 20 samples were degraded in a controlled environment utilizing the enzyme pancreatic lipase to generate degradants that included lauric acid and the sorbitan polyoxyethylene side chain. A new method was developed with sufficient sensitivity to analyze the degraded solutions. Lauric acid was derivatized with the fluorescent reagent 9-anthryldiazomethane to form 9-anthrylmethylethyl ester. The derivatized lauric acid was separated by reversed-phase chromatography and detected by fluorescence or UV spectroscopy. Three established methods utilized to measure polysorbate 20 were evaluated for their ability to detect degraded polysorbate 20. These methods were: (1) fluorescence analysis with N-phenyl-1-naphthylamine fluorescent dye; (2) UV spectroscopy with ammonium cobaltothiocyanate colorimetric reagent; and (3) nuclear magnetic resonance (NMR). RESULTS: Polysorbate 20 incubation with lipase resulted in degraded polysorbate 20 as determined by the derivatized lauric acid assay. The UV spectroscopy assay utilizing ammonium cobaltothiocyanate reagent was not able to detect the degradation of polysorbate 20 in the samples. The fluorescence method of analysis detected polysorbate 20 degradation as an approximate 50% decrease in micelles in comparison to standard nondegraded polysorbate 20 solutions. NMR analysis resulted in similar proton peak areas for both degraded and nondegraded polysorbate 20 samples. NMR spectra did contain minor differences between the samples. CONCLUSIONS: It is essential to choose the appropriate method of polysorbate 20 evaluation to assess the content, stability, and compatibility of a formulation. Current established methods to assess polysorbate 20 may overlook and do not necessarily monitor the potential degradation of this surfactant, which results in the formation of lauric acid. Because this type of degradation may occur in a formulation by an enzymatically active biopharmaceutical, a new method of analysis has been established.

Chemistry, Pharmaceutical↗

PubMedDate not supplied

A comparison of methods for determining lead content in drinking water: a portable anodic stripping voltammetry instrument method versus the standard EPA 239.2 method.

Lead levels in drinking water were measured by the standard U.S. Environmental Protection Agency (EPA)-approved atomic absorption spectroscopy-graphite furnace Method 239.2 and compared with determinations made with a newly available portable anodic stripping voltammetry (PASV) instrument. A standard curve was prepared at 2, 5, 10, 15, 20, 25, and 30 microg/L of lead. PASV instrument readings were lower than standard EPA method values, with a mean difference and standard error (SE) of the mean between the two of 1.538+/-0.588 microg/L (n = 7, p = 0.040, significant at the 95% confidence interval [CI]). First-flush drinking water samples collected from 144 water fountains/coolers were preserved with nitric acid. Total lead content was tested twice for 29 EPA method samples and 54 PASV instrument samples to determine the variation within each method; results were not significant at the 95% CI. Total lead content was determined for 144 samples by both methods. PASV instrument readings were lower than standard EPA method values (mean difference and SE of the mean 0.630+/-0.206 microg/L; n = 144, p = 0.0027, significant at the 95% CI). Mean and standard deviation of the 144 samples for the EPA method and the PASV instrument were 6.5+/-11.8 microg/L and 5.9+/-11.6 microg/L, respectively. Means were below the action level for lead of 15 ppb (microg/L), but some values were above the action level (18 [13%] using the EPA method; 20 [14%] using the PASV instrument). Retesting by EPA method showed two false positive PASV values. Results indicate that in some field situations the PASV instrument may prove useful due to its relatively low price, small size, ease of use, and quick readings.

Electrochemistry↗