RU2463600C1 - Method of detecting novocaine and lidocaine in urine - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves successive freezing at temperature 0-4°C for one hour, filtering through glass fibre and centrifuging at 3000 g for 15 minutes of a urine sample obtained from a patient, diluting with water in volume ratio 1:25, measuring, in the obtained urine test solution, potential relative a comparison electrode and determining concentration of novocaine and lidocaine using a calibrated curve.

EFFECT: faster and simpler method, high reliability and safety of analysis.

1 ex, 3 dwg

Description

The invention relates to the field of analytical chemistry and clinical diagnostics. It can be used to determine local anesthetics (novocaine and lidocaine) in the urine of patients when prescribing these drugs.

A known method for the quantitative determination of narcotic and medicinal substances in urine extracts (Dikunets M.A., Apolonova S.A., Rodchenkov G.M. // ZhAH. 2009. V.64, No. 8. P.854-864; RF patent No. 2384846, G01N 33/493, 2010; application of the Russian Federation No. 2008122386, G01N 3/50, 2009). The method includes extraction of narcotic and medicinal substances from physiological fluid, evaporation of the organic extract in a stream of nitrogen, dissolution of the dry residue in methanol and analysis of the resulting solution by high performance liquid chromatography in combination with mass spectrometry (HPLC-MS). The disadvantages of this method are the use of toxic organic solvents; duration and complexity of the analysis; expensive instrument base.

The invention is intended for direct quantitative in situ determination of novocaine and lidocaine in urine.

The technical result is a reduction in analysis time; simplicity of analysis; analysis automation; the possibility of in situ analysis; exception from the analysis of toxic reagents.

The technical result is achieved by the fact that the method for determining novocaine and lidocaine in the urine includes sequential freezing at a temperature of 0 ÷ -4 ° C for an hour, filtering through fiberglass and centrifuging at 3000 g for 15 minutes a urine sample obtained from a patient, diluting the obtained supernatant water in a volume ratio of 1:25, measurement using a sensor in the resulting test solution of urine potential relative to the reference electrode and determination of the concentration of novocaine and lidocaine from the calibration graph in the urine.

The figure 1 presents a block diagram of a method for determining novocaine and lidocaine in urine; figure 2 - the actual and certain values of the concentrations of novocaine (NovHCl) in the urine; figure 3 - metrological characteristics of the method for determining NovHCl in urine.

The method can be implemented using the following installation.

The design of the installation includes a biomedical refrigerator with a temperature of + 5 ... -5 ° C, a filter column filled with fiberglass, a centrifuge with an acceleration of 2000-4000 g, an electrochemical cell consisting of a PD sensor 1, a silver chloride comparison electrode 2, mounted in a tripod 3 containers with a test solution 4, a high-resistance electronic voltmeter 5, a control unit 6, and the PD sensor 1 and electrode 2 are immersed in a container 4 into which the test solution is poured, and through a voltmeter 5 are connected to the control unit 6. Design PD sensor 1 includes two plastic cases 7 and 8, in one of which a reference electrode 9 is installed, in the other there is a perfluorinated sulfocationite polymer (PSP) tube, or membrane, or rod 10 in potassium form so that one end is placed in case 7, and another protrudes beyond housing 8. Housing 7 is filled with 1M KC1 solution (RF patent No. 2376591). The control unit 6 includes a personal computer with software for automatically calculating the concentration of novocaine and lidocaine in urine according to the calibration schedule.

The method is implemented as follows. The urine sample is subsequently frozen for 1 hour at a temperature of 0 ÷ -4 ° С (for crystallization and precipitation of an excess of inorganic salts: chlorides and sulfates of potassium, sodium, ammonium), filtered through fiberglass, centrifuged for 15 minutes at 3000 g (to reduce the concentration of organic metabolites (proteins, sugars, "ketone bodies")). The resulting supernatant is diluted in a volumetric flask with water in a volume ratio of 1:25. An aliquot of 5 ml of the obtained urine test solution is placed in the container 4. The PD sensor 1 and the silver chloride reference electrode 2 are lowered into the container with the urine test solution 4 and the EMF of the electrochemical circuit is determined using a high-resistance voltmeter 5. EMF values are recorded after 2-5 minutes. A voltmeter 5 is connected to a control unit 6, which includes a personal computer with software, for automatically calculating the concentration of novocaine and lidocaine in urine according to the calibration graph of the EMF versus the concentration of novocaine and lidocaine in urine. The calculated concentration value is displayed on a computer screen.

EXAMPLE

Urine samples (10 ml) obtained from patients taking Novocain preparations were subsequently subjected to freezing for 1 hour at a temperature of 0 ÷ -4 ° C, filtering through fiberglass, centrifuging for 15 minutes at 3000 g. The resulting supernatant was diluted in a volumetric flask with water in a volume ratio of 1:25. An aliquot of 5 ml of the obtained urine test solution was placed in a container 4. The PD sensor 1 and a silver chloride comparison electrode 2 were lowered into a container with a urine test solution 4 and the EMF of the electrochemical circuit was determined using a high-resistance voltmeter 5. EMF values were recorded after 2-5 minutes. A voltmeter 5 was connected to a control unit 6, which included a personal computer with software, for automatically calculating the concentration of novocaine in the urine according to the calibration graph of the EMF versus the concentration of novocaine and lidocaine in the urine (the calibration dependence is linear in the concentration range of novocaine 5 · 10 ^-5 -7 , 3 · 10 ^-2 M with an approximation accuracy of 0.98 and allows you to record a change in the concentration of novocaine hydrochloride by 3 · 10 ^-5 M with a change in the response of the PD sensor by 10 mV). The calculated concentration value was displayed on a computer screen.

The detection limit of NovHCl in urine using this method was 5 · 10 ^-5 M. Verification of the correct determination of NovHCl in urine was carried out by the "entered-found" method. The relative error in the determination of NovHCl in urine did not exceed 7% (figure 2). The main metrological characteristics of the method for determining NovHCl in urine are presented in the table in figure 3.

Claims (1)

A method for the quantitative determination of novocaine and lidocaine in urine, including sequential freezing at a temperature of 0 ÷ -4 ° C for an hour, filtering through fiberglass and centrifuging at 3000 g for 15 min a urine sample obtained from a patient, diluting the obtained supernatant with water in a volume ratio 1:25, measurement of the potential in the resulting urine test solution relative to the reference electrode and determination of the concentration of novocaine and lidocaine using a calibration graph.

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