LEAD – A PREANALYTICAL/ANALYTICAL VARIABLE IN CLINICAL CHEMISTRY

Lead is one of the most studied clinically important metals due its high toxicity and a high number of workers exposed to it. The interest toward Pb is elevated by the fact that children are especially susceptible to lead poisoning. Research regarding lead poisoning requires a complex, multi-disciplinary (clinical medical and clinical chemical) approach. Monitoring human exposure to lead (intake, i.e. poisoning) may be achieved by quantification of Pb in tissues and body fluids. For that reason, a number of accurate and reliable analytical methods for the determination of Pb (analytical/preanalytical variable) were developed. An objective of this review paper is to provide key information necessary for proper interpretation of results of lead related clinical/laboratory tests. OLOVO - PREANALITIČKA/ANALITIČKA VARIJABLA U KLINIČKOJ HEMIJI Olovo spada u red najizučavanijih klinički relevantnih metala zbog svoje toksičnosti i broja radnika izloženih ovom metalu. Povećano interesovanje prema ovom metalu je posledica i toga što su deca naročito podložna trovanju njime. Ispitivanja koja se tiču trovanja olovom zahtevaju kompleksan, multidisciplinaran (kliničko-medicinski i kliničko-hemijski) pristup. Monitoring izlaganja olovu (unos, odnosno trovanje) se može ostvariti kvantifikacijom Pb u tkivima i telesnim tečnostima. Iz tog razloga je razvijen veliki broj preciznih i pouzdanih metoda za njegovo određivanje (analitička/preanalitička varijabla). Cilj ovog preglednog članka je da sumira ključne informacije neophodne za valjanu interpretaciju rezultata kliničkih/laboratorijskih testova vezanih za olovo

KINETIČKO-SPEKTROFOTOMETRIJSKI PRISTUP HIDROLITIČKOJ DEGRADACIJI AMPICILINA PRIMENJEN ZA ODREĐIVANJE HISTIDINA

The objective of this research was to develop a kinetic-spectrophotometric method for the determination of microquantities of L-histidine in pure form and dietary supplements. The method was based on the kinetics of ampicillin degradation by Ni(II) ion as a catalyst in the presence of L-histidine in a strongly alkaline medium. The rate of this reaction was monitored spectrophotometrically by measuring the increase in absorbance at 265 nm as a function of time. The same approach was used for the investigation of the reaction rate in the absence of histidine. A differential variant of the tangent method was used to process the kinetic data. Beer’s law was obeyed in the interval of histidine concentration from 1.24 µg/ml to 11.63 µg/mlwith the relative standard deviation ranging from 8.1% to 0.7%. The detection limit of 0.46 µg/ml was estimated based on the 3S0 criterion. The interference effects of some metal ions, anions, and other molecules on the reaction rate were studied to assess method selectivity. Herein described method was applied for the quantification of histidine in dietary supplements. The point hypothesis test confirmed that there was no significant difference between the proposed and the reference method.Cilj ovog istraživanja je bio razvoj kinetičko-spektrofotometrijske metode za određivanje mikrokoličina L-histidina u čistom obliku i dijetetskim suplementima. Metoda je zasnovana na reakciji degradacije ampicilina koja je katalizovana Ni(II) jonom u prisustvu L-histidina u jako baznoj sredini. Brzina reakcije praćena je spektrofotometrijski merenjem povećanja apsorbance na 265 nm sa vremenom. Isti pristup je korišćen za praćenje brzine reakcije u odsustvu histidina. Diferencijalna varijanta tangensne metode je upotrebljena za obradu kinetičkih podataka. Metoda je zadovoljavala Beer-ov zakon u intervalu koncentracija od 1,24 µg/ml do 11,63 µg/ml sa relativnom standardnom devijacijom od 8,1% do 0,7%. Detekcioni limit od 0,46 µgcm-3 je procenjen korišćenjem 3S0 kriterijuma. Selektivnost metode je ispitana na osnovu uticaja pojedinih metalnih jona, anjona i organskih molekula na brzinu reakcije. Opisana metoda je primenjena za kvantitativno određivanje histidina u dijetetskim suplementima. Primenom t-testa potvrđeno je da nema značajne razlike između rezultata predložene i referentne metode

Development of a kinetic spectrophotometric method for insecticide diflubenzuron determination in water and baby food samples

A kinetic spectrophotometric method for determining residues of insecticide diflubenzuron 1(4-chlorphenyl)-3-(2,6-diflubenzoyl)urea (DFB) has been developed and validated. Kinetic method was based on the inhibitory effect of DFB on the oxidation reaction of sulfanilic acid (SA) by hydrogen peroxide in the presence of Co2+ ions in a phosphate buffer, which was monitored at 370 nm. DFB can be measured in the concentration interval 0.102 – 3.40 μg mL-1 and 3.40 – 23.80 μg mL-1. The detection and quantification limits of the method were calculated according to the 3σ criteria and found to be 0.077 μg mL-1 and 0.254 μg Ml-1, respectively. The relative standard deviations for five replicate determinations of 0.102, 1.70 and 3.40 μg mL-1 DFB were 2.08, 1.22 and 1.21 %, respectively, for the first concentration interval, and the recovery percentage values were from 94.12 to 97.35 %. HPLC method was used as a parallel method to verify results of the kinetic method. The kinetic method was successfully applied to determine diflubenzuron concentrations in spiked water and baby food samples after solid phase extraction of the samples. The F and t values at 95% confidence level are lower than the theoretical ones, confirming agreement of the developed and the HPLC method. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172061