A rapid method for dry weight determination of proteins on a micro scale with an electrobalance

A method to determine the dry weight (0.25-2 mg) of aqueous protein solutions within 1 h, using an electrobalance, is described. The drying of 50-200 mul solution pipetted onto a glass fiber disc is carried out in vacuo at 70 degrees C until the recorded dry weight becomes constant (within 25-40 min). It has been shown that the dried residue can subsequently be used for other purposes, such as quantitative amino acid analyses. The method is also suitable for the determination of moisture content in lyophilized protein samples.     

Simple method for the routine determination of betaine and N,N-dimethylglycine in blood and urine

A simple and convenient method using commercially available derivatization reagents is described for the measurement of betaine and N,N-dimethylglycine (DMG) in blood and urine. Precolumn derivatization of plasma or urine is performed directly in acetonitrile without extraction with p-bromophenacyl bromide and crown ether as catalyst. The p-bromophenacyl ester derivatives are then separated by high-performance liquid chromatography, using an isocratic system of acetonitrile and water containing choline. Effluent was monitored at 254 nm. The limit of detection was 5 micromol/L for betaine and 2 micromol/L for DMG. Analytical recovery was >97% for both analytes. Total and within-day CVs were 2.0-4.4% and 0.9-2.2% for DMG. For betaine, the total and within-day CVs were 1.3-5.3% and 0.4-3.8%, respectively. The method is precise and cost-effective and has been used successfully to determine the concentrations of DMG and betaine in human plasma and urine.     

Evaluation of a simplified method for site-specific determination of mutans streptococci levels

To determine the oral mutants streptococcal "load" of an individual, saliva samples reflecting the number of colonized tooth surfaces, are often applied. Sometimes a plaque sample from a specific site would be an advantage, for example in connection with local antimicrobial treatments. The aim of the present paper was to evaluate a chairside method for determination of mutans streptococci interproximally. One hundred subjects participated. Four approximal tooth surfaces of each individual were sampled using toothpicks. The toothpicks were then let to contaminate a pad on a specially designed plastic strip and, for comparison, a MSB-agar plate. The strips were incubated in the standard "Strip mutans" broth. The yield of colony forming units on the strip surface corresponded significantly with that on agar plates. Being a simple chair-side method for the evaluation of the site-specific load of mutans streptococci, it is suggested that the method will be used in various investigations to clarify its potential in different clinical situations.     

Simple and fast chromatographic method for the determination of sotalol in human serum

We developed a method for the determination of sotalol in human plasma. After a simple deproteinization of the sample, we submit the supernatant to high-performance liquid chromatography with fluorescence detection. A few minutes are necessary to complete the analysis.     

Gaschromatographic method for routine determination of pregnanediol and pregnanetriol in urine (author's transl)

A rapid, highly sensitive and simple method for the routine measurement of urinary pregnanediol and pregnanetriol involving enzymatic hydrolysis, extraction with toluene and gas liquid chromatography is described.     

Evaluation of a microspectrofluorimetric method or serum vitamin A

A microspectrofluorimetric method for vitamin A was compared with spectrophotometric and trifluoroacetic acid-colorimetric procedures. Values obtained by the fluorimetric method showed a high degree of correlation with those obtained by other standard procedures. However, it was found that the fluorimetric method yielded values which were several-fold higher than those obtained with the spectrophotometric method when sera from pregnant women were tested. The fluorescence from sera of pregnant subjects showed a triphasic decline even when the samples were stored at --20 degrees C.     

Hydroxyproline in serum as a homeostatic index for calcium in cattle

Hydroxyproline, calcium, magnesium, phosphorus, and alkaline phosphatase values were determined in serum over 24 h in Holstein cows. The cows represented two age groups and three percents of diet calcium. Hydroxyproline followed a cyclic pattern dipping at 0800 and 1600 h after milking at 0500 and 1530 h. Phosphorus showed a 24 h rhythm peaking at 1600 h. No other time effects were demonstrated. Hydroxyproline and alkaline phosphatase were both lower in the older cows, indicating a decreased calcium mobilization from bone with age. There was a correlation coefficient of only .20 between serum calcium and hydroxyproline. The calcium concentration in serum was maintained within a narrow range presumably as a result of homeostatic mechanisms involving bone resorption, i.e. the release of calcium and hydroxyproline may indicate the degree of homeostasis required to maintain serum calcium.     

原子吸收光谱法测定锌精矿中镉不确定度评定

对锌精矿化学分析方法——火焰原子吸收光谱法测定镉量时的不确定度进行评定。根据分析过程,对其不确定度来源进行量化表述,评定原子吸收光谱法测定锌精矿中镉的不确定度。评估出的不确定度范围,适用于评价不同实验室人员或不同实验室之间测定结果的质量。     

红外吸收法测定焦炭中硫的不确定度评定

采用红外吸收法测定焦炭中硫,并对一个焦炭中硫的不确定度进行了评定,给出评定结果,求出测定结果的扩展不确定度。     

A modified ultraviolet spectrophotometric method for the determination of theophylline in serum in the presence of barbiturates

Ultraviolet spectrophotometry is the most commonly used technique for the determination of theophylline levels for therapeutic monitoring. Common interferences in most methods are barbiturates and xanthines. A modified method which eliminates interferences from barbiturates and most xanthines is presented. Theophylline is extracted from serum with chloroform/isopropanol at pH 7.4 back extracted into dilute hydrochloric acid and then the solution is made alkaline with sodium hydroxide. Barbiturate interferences are eliminated. Interference from caffeine, uric acid, 7-(2,3-dihydroxypropyl)theophylline, xanthine, and hypoxanthine are not observed. Theobromine, and the metabolite 3-methylxanthine interfere. Interference is not observed from quinidine, diazepam, salicylate, glutethimide, methylprylon, propranolol, methaqualone, dilatin and ethchlorvynol. Sulfanilamide, procainamide and chlordiazepoxide interfere.     

Evaluation of the CLINITEK ATLAS for routine macroscopic urinalysis

OBJECTIVES: To evaluate the performance of a new, benchtop, fully automated urine analyzer the CLINITEK ATLAS and compare it with the URICHEM 1000 CHEMSTRIP UA analyzer. Macroscopic analysis included measurement of 8 urine analyte chemistries and specific gravity by the refractive index method (SgRl). METHODS: The analytical performance studies conducted were calibration stability, precision (within-run and day-to-day), comparison of results of 437 fresh patient urine specimens, analysis of time performance, and problem logging over a 16-day evaluation period. RESULTS: Satisfactory calibration reproducibility, within-run (n = 10), and day-to-day (n = 16) precision was found because results fell within the +/- one color-block by the proposed National Committee for Clinical Laboratory Standards (NCCLS) criteria. Patient results (n = 437) from the 2 analyzers giving the same color-block agreement was found to be for pH, 52%; glucose, 92%; ketones, 86%; protein, 79%; bilirubin, 97%; leukocytes, 72%; blood, 80%; and nitrite, 98%. The concordance defined by the NCCLS criteria as the agreement of results +/- one color-block between the 2 analyzers was found to be for pH, 96%; glucose, 99%; ketones, 100%; protein, 95%; bilirubin, 100%; leukocytes, 97%; and blood 86%. The SgRl determined on ATLAS was correlated with the RD-10 Rapid Density analyzer with the following results: slope = 0.97, intercept = 0.033, r = 0.94, Syx = 0.003, for a range of values from 1.002 to 1.070. CONCLUSION: Our preliminary data indicate that the analytical performance, and automatable features for complete walk-away function of this analyzer can significantly increase the overall testing efficiency in the urinalysis laboratory.     

Evaluation of strategies for molecular fingerprinting for use in the routine work of a Mycobacterium reference unit

We have investigated the role of two rapid PCR-based typing methods, IS6110-based PCR and spacer-oligonucleotide typing, within a national tuberculosis reference service. The validity of clusters with IS6110 restriction fragment length polymorphism fingerprints with less than 6 bands was also investigated in the context of referred isolates.     

Evaluation of a flow cytofluorometric method for rapid determination of amphotericin B susceptibility of yeast isolates

A rapid-flow cytofluorometric susceptibility test for in vitro amphotericin B testing of yeasts was evaluated and compared to the National Committee for Clinical Laboratory Standards (NCCLS) M27-T reference broth macrodilution method. The flow cytofluorometric method is based on the detection of decreased green fluorescence intensity of cells stained with DiOC5(3), a membrane potential-sensitive cationic dye, after drug treatment. Testing was performed on 134 clinical isolates (Candida spp. and Torulopsis glabrata). From the dose-response curve obtained for each isolate, three endpoints were calculated by computer analysis (the concentrations at which the fluorescence intensity was reduced by 50, 80, and 90%, i.e., 50% inhibitory concentration [IC50], IC80, and IC90, respectively). A regression analysis correlating these endpoints with the M27-T MICs showed that the best agreement was obtained with IC80. The flow cytofluorometric method showed good reproducibility with control strains. These initial results suggest that the flow cytofluorometric method is a valid alternative to the NCCLS reference method.     

Isotope dilution-liquid chromatography/electrospray ionization-tandem mass spectrometry for the determination of serum thyroxine as a potential reference method

A new candidate reference method is presented for the determination of thyroxine in serum. The method is based on isotope dilution-liquid chromatography/tandem mass spectrometry using electrospray for ionization. The internal standard used was 13C6-thyroxine, sample pretreatment consisted of protein precipitation and a two-step liquid/liquid extraction procedure, HPLC was performed on a C-18 column with an eluent containing methanol/water/formic acid (60:40:0.1, by volume), and finally thyroxine and its isotopically labeled analogue were measured in the selected reaction monitoring mode for the transitions m/z 777.7--> 731.7 and m/z 783.7--> 737.7, respectively. The detection limit for thyroxine was 6 pg, the within-run coefficient of variation was 1.1%. The samples were measured in six-fold: in duplicate on three independent days. The mean overall coefficient of variation of the method was 1.6%. The new method was evaluated by measuring nine control sera previously determined by an existing ID-GC/MS method. The differences between the results of the two methods ranged from-1.6% to +3.3%, with a mean of +0.2%.     

Evaluation of the efficacy of naltrexone in alcoholism by the determination of serum carbohydrate-deficient transferrin

Naltrexone (NTX) has been shown to be a useful drug for the treatment of alcohol dependence (AD). Carbohydrate-deficient transferrin (CDT) in serum is a new biologic marker of alcohol abuse. To evaluate the efficacy of NTX (50 mg/d) in AD, a group of 20 alcoholics with CDT > 20 U/l was studied using monthly laboratory tests (CDT, ESR, AST, ALT, GGT) and specific psychological testing (CAGE). After the second month statistically significant differences in CDT levels were found. By the end of the study, 13 patients (responders) had normalized their CDT levels. There was no correlation between CDT values and the other laboratory markers. The difference in routine laboratory markers between responders and non responders was not significant. NTX was well tolerated by all the patients and significant alcohol abstinence was achieved. CDT was demonstrated to be a effective marker for the evaluation of alcoholic abstinence during treatment with NTX. Superior results were obtained in comparison with the routine customary markers for AD.     

A micro method for the determination of the configuration of histidine in peptides: evidence for partial racemization during peptide synthesis (author''s transl)

A gas chromatographic method for the determination of small portions of D-histidine together with an excess of L-histidine (or vice versa) is described. Histidine is degraded to aspartic acid by reaction with ozone. The enantiomers are esterified with (+)-3-methyl-2-butanol. After N-trifluoroacetylation the volatile diastereoisomers are separated in glass capillaries coated with a chiral stationary phase and determined quantitatively. For precise evaluations the partial racemization during peptide hydrolysis must be accounted for. The method was applied to some histidine peptides and about 5% racemization was measured.     

Urethrocystometry as a routine method for the objective evaluation of women with urinary incontinence

Over a 2-year period, 401 patients with urinary incontinence were examined at the Women's Clinics in Lund and Malm? and then investigated by urethral pressure profile measurement and simultaneous urethrocystometry. After full investigation the patients could be classified as follows: 214 (53.4%) had genuine stress incontinence, 48 (12.0%) had genuine urge incontinence, 41 (10.2%) had mixed incontinence, 20 (5.0%) had urgency-frequency, 6 (1.5%) had neurogenic incontinence, 9 (2.2%) had incontinence of uncertain aetiology, and 63 (15.7%) of the patients were apparently continent with normal urethral pressure profiles and urethrocystometrograms.