Study On The Determination Method Of Thiocyanate (SCN~-) In Urine

Cyanides(inorganic cyanide,organic cyanide,CN-)is widely used in chemical synthesis,electroplating,smelting of precious metal extraction,pharmaceutical,printing and other industries and military industries,including inorganic cyanide(cyanide)is highly toxic substances,high concentration of hydrogen cyanide or sodium cyanide can be inhaled,oral 50～100mg caused rapid respiratory arrest,even death;long term exposure to low dose of cyanide,can cause chronic toxicity,inhibit the synthesis of thyroid hormone transporters and uptake of iodin,hinder the utilization of iodine,cause goiter.The limit value of 11 kinds of cyanide has been stipulated in China’s GBZ2.1 "Occupational exposure limits for hazardous agents in the workplace".Cyanide can invade the body through the respiratory tract,gastrointestinal tract and skin,inorganic cyanide reaction with sulfur in thiocyanate generated enzyme,and then transformed into cyano low toxic thiocyanate radicals,then the formation of thiocyanate can be excreted in urine.Under the action of cytochrome P450 of the liver Organic cyanide can metabolism to epoxy compound or cyanide cyanohydrin,generates hydrocyanic acid,hydrocyanic acid cause subacute poisoning symptoms,at last part of the organic cyanide thiocyanate generated under the action of the enzyme to generate thiocyanate in urine excreted.Previous studies have confirmed that thiocyanate in urine is a metabolic biomarker for cyanide exposure.However,the occupational exposure limit of cyanide has not been formulated at home and abroad.Currently,the standard method for detecting SCN-in urine is "WS/T 39-1996 method for the determination of thiocyanate in urine by pyridine-thiobarbituric acid spectrophotometry".The method is characterized by poor properties and low sensitivity.In order to establish a standard method for the determination of thiocyanate in urine,the chromatographic method for the determination of thiocyanate in urine was studied.The studied and optimized through the column of ion chromatography,the eluent concentration and flow rate of mobile phase conditions and parameters,the sample dilution ratio,centrifugal effect,solid phase extraction column selection were compared to determine the sample pretreatment method;the experiment were stability of urine samples under different preservation conditions;Study on the method of linear range,detection limit,quantitative lower limit,accuracy and precision,interference performance and other indexes are studied;determination of the urine samples which is contact with acetonitrile factory.Urine sample pretreatment method:1.Take lOmL urine sample and add 15 mL centrifuge tube.The urine sample was centrifuged at 4000 r/min and 10 min.2.accurately take the upper layer urine sample 1.0mL in 10 mL volumetric flask,then use deionized water to volume to 10 mL,and shake with vortex oscillator 1 min mixing.At the C18 solid phase extraction column have been activation,3mL diluted urine samples through the activated C18 column,the sample will throught C18 solid phase extraction column by gravity;repeated 2 times,discarding the first filtrate,take the filtrate for second times,two times at intervals of not more than 5min.Filter the filtrate with 0.22 μmneedle nylon filter membrane and test it in the sample bottle.Ion chromatography determination conditions:column:IonPac AS 16(250 mmx4 mm)and IonPae AG 16 protection column;gradient elution mode:0～15min KOH eluent concentration is35mmoL/L 15.1～18.0min;KOH eluent concentration is 70mmoL/L;18.1～23.Omin,KOH of eluent concentration is 35mmoL/L;eluent flow rate:1 mL/min;inhibition of current 179 mA;sampling quantity:25 μL.Sample stability test showed that thiocyanate samples could be stored for 5 days at room temperature and 7 days at 4℃,could be stored for 14 days at-20 ℃;Method of Performance index:this method uses standard curve external standard method for quantitative detection.The content of thiocyanate is linear in the range of 0.1μ.g/mLto 25.0μg/mL,and the correlation coefficient is r=0.9999.The minimum detection limit was 0.1 1μg/mL,and the quantitative lower limit was 0.35μg/mL.The recovery rate of normal urine was 95.1%to 99.9%,and the accuracy was 0.54%～2.05%,and the precision between batches was 2.06%～5.09%.The possible anions in urine,such as Cl-,F-,NO3-,SO42-,Br-,I-,CH3OO-,CO32-,CN-and so on,do not interfere with the determination of analytes.Methods:the urine samples of 8 workers in the acetonitrile workshop of a chemical plant were detected.The concentration of thiocyanate in urine was between 0.11～7.30μg/mL,and with an average concentration of 3.35μg/mL.This study used C18 solid-phase extraction column purify the sample,this will reduce the use of organic solvents,the detection limit is 0.11μg/mL,it is better then the national standardmethod The technical indicator of method compliance with rule of GBZ/T 210.5-2008."Guide for establishing occupation health standards-Part 5:Determination methods of chemicals in biological materials”.Field application shows that this method is suitable for determination of thiocyanate in urine of occupationally exposed workers.