Quantitative Determination of Chromium by a Diphenylcarbazide Method

铬被广泛应用于其他金属，如钢铁、铬合金和耐火材料产品，它也被用于电镀、鞣制和颜料工业。虽然铬化合物非常有用，但铬离子对人体有害。因此，使用铬的制造商需要仔细处理和快速定量测定，以确保用户和产品的安全。其中最广泛使用的定量方法是使用紫外-可见分光光度计的Diphenylcarbazide Method。Application NoteUV-0004 Quantitative Determination of Chromiumby Diphenylcarbazide Method2/4Application Note Quantitative Determination of Chromium by Diphenylcarbazide Method In t ro d uc t ion Chrom i um is widely used with other metals such as iron and steel， chromium alloy， and refractory products， it is also used in the plating， tanning， and pigment i ndustries. While ch r omium compounds are very useful， chromium ions are h armful to the h uman body.Therefore， manufacturers us i ng chromium r equi r e carefu l hand li ng and r apid q u antitat i ve determina t ion for user and product safety. The most widely used q u anti t at i ve method i s the diphenycarbazide absorption method u sing a UV-Visible spectrophotometer. This application note examines the detection and quantitat i on limits of chrom i um using a JASCO V-630 spectrophotometer. Calibrat i on curves were created using a chromogen i c kit from a commercial r eagent manufacturer f or simple quantitati v e determinat i ons. V-630 UV-Visible Spectro p hotometer Keyword s V-630， U V -V i si bl e /NIR， M a t e ri a l s， Quan ti tation Exper i men t al T o prepare t he stock standard solution，K，Cr ，O， was d ri ed a t 150℃ f or one h our t h en placed in a desiccator. 8.79 mg of the K，Cr ，O， was dissolved i n 100 mL water and 80.4 mL of this solu t ion was dilu t ed to 100 mL in a 100 mL f lask， produc i ng a 25 mg/L chrom iu m sta n dard stock solution. T h is was furt h er dil u ted to c r eat e another standard stock solut i on of 0.25mg/L. These two stock solutions were used to prepare Cr (VI) standards for the calibration curves with the following concentrations： 1.5， 1.0，0.5， 0.25，0.125，0.060，0.040，0.020，0.010， 0.0075，0.0050， 0.0025， 0.0010， and 0.0000 mg/L. T h e chromogenic r e ac ti on of t h e ch r omat e solut i ons was allowed to e qui l ibrate at room temperatu r e (21℃). One package of the reagent u sed for Cr (Vl) water analysis wa s added to t he cal ib ration curve solut i ons i mmediate l y after openi n g since the reagent i s h ygroscopic and deteriorates with ti me. The bottle of the analysis solution was agitated by hand for approximately 60 seconds until completely d i ssolved . I ncomplete m i xing does n ot provide a proper ch r omogenic reaction a n d will h ave an effect o n the absorbance values obta i ned for the reagent r eaction. Granular reage n t will remain eve n if the reagent dissolves perfectly i n the solution . The remainder prec i pitates at the bottom of cell a n d does not have an influ e nce on the absorption measure m ents. 25 mL of a 0.5 mg/L Cr (V I ) solu ti o n was p re p a r ed to evaluate t he ti me r equired for proper reac t ion of the c h romogenic reagent using t h e ti me course absorption measurement da t a f rom t h e chromogenic r eaction (Figure 1). The ch r omoge n ic reagent was added to the solution r i ght afte r ope n ing， mixed for one minute， and the reaction t i me at t h e absorpt i on maximum of 540 nm was measured . Here， 90 seconds was assumed as the ti me delay after addition of the r eagent unt i l sta r ting the absorption measurement. The c h romogenic reactio n was completed approximately 150 seconds after sta r ting the time based measurement (4 m i n u t es afte r addition of the r eagen t ). Further， the reagent color became stable 210seco n ds a f ter star tin g the measurement (5 min u tes af t er addit i on of th e reagent). Figure 1. Ti m e cou r s e m e asu r em e nt o f t h e chromogeni c react i o n a t 540 nm (lef t) a n d co l o r c h ang e of t he reactio n befo r e an d a ft er t he add it ion of t he r eag en t (r i ght ). R esul t s Figure 2 illustrates the change in the absorption maximum upon the addit i on of the reagen t to the chromium standa r d solutions. JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A Figure 2. Ab so r p t i on sp e c t ra o f v a r yi n g Cr (V I ) standa r d so lu t i o n s. Fluctuation in the spectral baseline wa s observed for t h e Cr (Vl) sol u tion conce n t r ations betwee n 0.01 mg/L and 0.001mg/L. Thus， the calibrat i on curves we r e created based on t h e peak heigh t at 542 nm u sing peak b aseline points at 402 and 635 n m. The ca l culated peak heigh t va lu es are shown in Table 1. The quantitation limit of the calibra t ion curve created with the complete calibration set was 0.09 mg/L. Fu r thermore， when the cal i brat i o n cu r ve was created using only the data from the sol u tions i n t he range between 0.01 mg/L and 0.001 mg/L， a quantitation l i mit of 0.0025 mg/L was obta i ned with t h e t r uncated data set (F i gure 3). Figure 3. C al i b r a tion cu r ves f or st a nd ar d concen t r a t i o n s (lef t) a n d t h e s hor tene d c on c e ntra tion ra n g e (right). JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A UASGO Table 1. Ch r omiu m stan d a rd con cen tr a tions a n d ca l c ula te d absor p tion s. Concentration (mg/mL) Absorbance Concentration (mg/mL) Absorbance 0 -0.00019 0.02 0.013 0.001 0.00036 0.04 0.02695 0.00125 0.00068 0.06 0.03932 0.0025 0.00134 0.125 0.0827 0.005 0.00302 0.25 0.17008 0.0075 0.00459 0.5 0.33018 0.01 0.00603 1 0.64278 一一 一一 1.5 0.94904 Conclu s ion This applic a tion n otes demonstrates the excellent sensitivity of the JASCO V-630 by quantifying ch r omium concentrat i ons between 0.09 mg/L to 1.5 mg/L， as well as between 0.01 mg/L and 0.001 mg/L. 28600 Mary's Cour t ， E a s to n ， M D 21601US A