BACKGROUND Hyperoxaluria is a major risk factor for kidney stone formation. Although urinary oxalate measurement is part of all basic stone risk assessment, there is no standardized method for this measurement. METHODS Urine samples from 24-h urine collection covering a broad range of oxalate concentrations were aliquoted and sent, in duplicates, to six blinded international laboratories for ...

This study describes optimization of headspace solid phase microextraction followed by gas chromatography equipped with a flame ionization detector for toluene at trace level in spiked urine. The parameters affecting the extraction and gas chromatographic determination of analytes were studied: extraction time and temperature; desorption time and temperature; addition of NaCl; and pH, volume an...

A sensitive and easy analytical method for catecholamine metabolites including 4-hydroxy-3-methoxyphenylglycol sulfate (HMPG sulfate), vanillylmandelic acid (VMA) and homovanillic acid (HVA) determination was developed based on liquid chromatography-tandem mass spectrometry in a negative multiple reaction monitoring mode. The analytes were rapidly separated on a reversed-phase Waters Xbridge C1...

Differential pulse cathodic adsorptive stripping voltammetric method was developed for the determination of prednisolone based on electrochemical reduction of the drug at a hanging mercury drop electrode (HMDE) in 0.04 M Britton-Robinson buffer pH 3.5. The peak current varied linearly over the concentration range 7.21-144.2 ng/ml prednisolone with limit of detection and limit of quantification ...

A simple and rapid method was developed using cyclic, differential pulse and square wave voltammetric techniques for the determination of trace-level chalcone at a glassy carbon electrode. Chalcone could produce two anodic peaks at about 0.514 V and 1.478 V and a cathodic peak at about −0.689 V. The differential pulse voltammerty presents a good linear response as compared to square wave voltam...

Laser-induced graphene from paper (paper-LIG) was applied in non-enzymatic electrochemical sensing of uric acid (UA) human urine. Paper-LIG formed by CO2 laser modification into a 3D arrangement. Kinetic analysis paper-LIG electrodes returned effective heterogeneous electron transfer standard rate constants 1.4 × 10−3 cm s−1 and 7.8 10−4 for [Ru(NH3)6]2+/3+ [Fe(CN)6]4−/3− redox probes, respecti...

A comprehensive validity assessment study was performed on eight commercial urine assays for detection of cocaine use. Sensitivity, specificity, and accuracy of each assay were evaluated by analyzing, in random order and under blind conditions, specimens spiked with known drug concentrations and clinical specimens obtained from human subjects after intravenous cocaine use. Commercial assay resu...

An intercomparison exercise was conducted for the quantification of arsenic species in spiked human urine. The primary objective of the exercise was to determine the variance among laboratories in the analysis of arsenic species such as inorganic As (As+3 and As+5), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Laboratories that participated had previous experience with arsenic ...

Monoand di-protic alkyl and aryl phosphates, phosphonates, and thio analogues were determined in spiked samples of bacterial growth medium and human urine using a new procedure wlth a detection llmit of less than 2 pmol each. The acids were fully protonated by passing the aqueous samples through BioRad AG 50W-X8 (H') resin and dried thoroughly before refluxing with 3-benzyl-1-p-tolyltriazene in...

The potential for antibiotic residues in calves from consuming milk containing penicillin G or amoxicillin was investigated. Six calves were fed milk replacer, 6% body weight twice daily, containing 0.293, 2.92, or 5.85 microg of penicillin/ml (ppm) G or 0.25, 1.0, or 2.0 microg of amoxicillin/ml for three consecutive feedings. Urine and blood samples were collected after each feeding. Serum an...