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Analytical chem final paper

front 1 abstract	back 1 paper test card engineered to perform an iodometric titration iodometric titration- type of redox rxn with iodine where appearance of iodine indicates end point card requires storage + mixing on demand of diff incompatible reagents titration activated when applied solution to card (dried reagents reconstituted + combined through surface-tension-enabled mixing (STEM) iodine atoms quantified from iodate in aq solns (0.8-15 ppm) useful to quantify iodine in salts (example) accuracy = 1.4 ppm precision = 0.9 ppm detect B-lactam antibiotics when using iodometric back titration meets ASSURED criteria - to use in low resource settings where lab based analytical procedures are not very available
front 2 intro	back 2 paper analytical devices (PADs) - good tools to solve chem problems in low resource settings enable chem to be performed in locations that lack reliable access to lab reagents, glassware, instrumentation, etc. they also store reagents + separate fluids /things + can act as timers can be used to create/perform complex analytical tasks (like PH titrations) used for quantification encournters for many technical challenges to overcome in order to have reliable measurements reagents stored on paper substrate must be compatible + stable for long time interest - to use paper test cards (the PADs) to address analytical need of salt producers in the developing world. salt for consumption is usually fortified w/ potassium iodate (from 15-50 ppm iodine) many of the salt producers do not have access to a titration lab to perform the iodometric titration used to assay the iodate -> the test card is designed to carry out the entire analytical task used salt w/ iodate in it as a model system to establish the analytical metrics of the redox titration analysis w/ iodometric titration -> xs iodide react w/ iodate in presence of acid = form triiodide then triiodide titrated w/ thiosulfate using starch solution (THE INDICATOR) the endpoint is reached when the color turns clear show versatility of this titration device by also quantifying beta-lactam antibiotics via iodometric back titration
front 3 results + discussion	back 3 REAGENT STORAGE AND SURFACE TENSION ENABLED MIXING (STEM) reagents for the iodometric titration of iodate cannot be stored together on paper substrate at acidic pH, iodide oxidized by air and the starch indicator is degraded by both acid and iodine (this happens both in solution AND in DRIED reagents on paper) - conclusion: strict isolation of stored reagents is necessary wax patterning - via rapid printing methods (whiteside) = make isolated zones on paper to separate the reagents + recombine during titration loading zones made where the reagents are put and dried for storage after test soln added to rxn area -> card shaken wax barriers + solution meniscus confined the sample and reagents this entire process = surface tension enabled mixing (STEM) part per million on paper regular iodometric titration - aloquots thiosulfate titrated onto sample until eq. point but on paper test card: zones in each rxn are loaded w/ diff amounts of sodium thiosulfate along w/ excess potassium iodide, tosic acid, and starch indicator in central indicator area iodine also stabilized more for storage as a Cd(II) salt aliquots applied to each rxn area to activate the titration paper test card not like traditional titration(which usually perform best w sharp end point indicator) - instead, each rxn area gives no color unless amount of iodate in soln overwhelms the amount of thiosulfate on rxn area = papercard combines features of limit tests and colorimetric quant. assay negative control - contains only acid + starch (should have no response when test soln applied iodine is detected with starch indicator the limit test detects iodide in concentrations greater than 20 ppm (diff squares detect diff limits of iodide) square 12 - positive control w/ potassium iodate, potassium iodide, tosic acid, starch to produce blue response no matter what test soln is applied CALIBRATION OF DEVICE quantification by color measurement is challenging if variations captured in the sun, shade, or various lightings -> so images captured in a light box color measured by computer image analysis SD of blank samples, LOD determined to be 0.8 ppm and lower LOQ was estimated to be 2.4 ppm INTERNAL VALIDATION experts analyzed solns blindly, and read w accuracy of 0.5 ppm and precision of 0.5 ppm range 0-75 ppm 2 newly trained users analyzed same 110 images, achieved accuracy of 1.4 ppm + avg precision of 0.9 ppm computerized image analysis -> intensities of colors measured + conc measured with calibration curves 4 of the salt pads gave discrepant results + could not be quantified avg accuracy for image analysis by computer = 0.9 ppm main source of inaccuracy is systematic underestimation of the iodine concentration at high iodine concentrations camera software - source of error avg precision for range 0-15 ppm was 0.9 ppm avg precision for 0-7 ppm was 0.3 ppm = these measurements show that computer image analysis is more accurate and precise than visual estimates of concentrations by newly trained users but also that expert readers can surpass the accuracy and precision of the computer image analysis program visual interpretation: advantages - increases usability in low resource settings = capture data w/ cell phone = interpret electronically = preserve it empower monitoring agencies to track quality of salt in diff geographical areas over time disadvantages - human error in reading / recording results
front 4 cont.	back 4 robustness tested to see how storage + diff water sources affected response 8 ppm I standard using tap water w/ high mineral content hard water standards had 8% error lake water standards had 17% error

front 5 cont	back 5 utility of test card for other analyses: iodometric back-titration of amoxicillin iodometric titration saw procedure for quantification of beta-lactam antibiotics (ensure quality of pharmaceutical product) studied if paper test card analysis could be useful for quality testing in low resource settings where analytical chem labs are rare tested amoxicillin conc. 0-0.9 mg/ml test card response showed good differentiation shows that cards could be used to detect antibiotics that contain 83% labeled API
front 6 cont.	back 6 suitability for use in low-resource settings ASSURED (affordable, sensitive, specific, user friendly, rapid, robust) criteria to assess devices meant for use in low resource settings considered in design reasons how/why: complete process = 0.09$ + $.5 labor + could be decreased paper test card performs iodine analysis w/ accuracy + precision that rivals other technology used in salt fortification plants in the developing world + can perform iodometric back titration w/ to detect substandard antibiotics sufficient accuracy takes 5 mins test cards can withstand a lot of conditions test cards can be analyzed using computer image processing of mobile phone photographs -> mobile phone network for data collection + archiving
front 7 experimental section	back 7 materials 2% starch indicator p-toluenesulfonic acid potassium iodide cadmium chloride sodium nitrite anhydrous sodium thiosulfate secondary standard of potassium iodate NaCl amoxicillin iodine soln etc. fabrication of saltPAD Running + analyzing test cards create test soln, dilute 3.25 g salt into 15 g water (1:5) dilution 125 microL soln per rxn zone on the test cards + shake SaltPAD calibration curves iodate standards from 0-15 ppm I in 3.7 M NaCl created by dilution from stock potassium iodate soln standards pipetted on saltPADs and blue color PAD respondse measured w/ imageJ internal lab validation 3.7 M NaCl brine spiked with 11 levels of iodate + coded samples analyzed bind by 2 operators - each apply test samples stability testing - accelerated aging of test cards stimulated by storing at 40 deg celcius back titration to quantify amoxicillin amoxicillin conc. from 0-1.0 mg/mL to 2.0 mL of each soln, 1.0 M NaOH with 2.0 mL HCl add 10 ml of 0.0050 M triiodide pipetted into soln diluted soln 2:25 w/ water new calibration curve for iodine response created bc of matrix change from salt soln to water soln
front 8 conclusions	back 8 paper card that stoers multiple reagents + recombines them thru surface tension enabled mixing paper analytical device performs accurate + precise measurments of iodate in iodized salts cards can be used for other assays of redox active analytes when did for beta-lactam - gave good differentiation among amoxicilllin

front 9 Advantages to using PADs / the paper test card engineered in the experiment	back 9 enable chemistry to be performed in locations that lack reliable access to lab reagents, glassware, and instrumentation they are also cheap to use/produce and can be done in about 5 minutes. (time/money) can perform complex analytical tasks (like titrations)
front 10 what is the issue / topic being addressed in the paper?	back 10 using the paper test cards to address an analytical need of salt producers in the developing world salt for consumption is usually fortified w/ potassium iodate (from 15-50 ppm iodine) many of the salt producers do not have access to a titration lab to perform the iodometric titration used to assay the iodate -> the test card is designed to carry out the entire analytical task
front 11 CONCLUSION: TOPICS THAT COULD DEFINITELY BE ASKED BASED ON THE PAPER	back 11 titrations ppm precision, accuracy dilution question back titration w/ iodine external standard slope and sensitivity LOD LOQ/LLOQ SD (std deviation) grubbs test
front 12 what is the indicator used	back 12 then triiodide titrated w/ thiosulfate using starch solution (THE INDICATOR) in analysis: excess iodide react w/ iodate in presence of acid = form triiodide triiodide titrated w/ thiosulfate using starch soln as an indicator if triiodide exceed reducting capacity of thiosulfate, then the indicator is BLUE if its smaller than the capacity, then indicator is UNCOLORED

front 13 what is the negative control	back 13 negative control - contains only acid + starch (should have no response when test soln applied
front 14 what is the positive control	back 14 square 12 - positive control w/ potassium iodate, potassium iodide, tosic acid, starch to produce blue response no matter what test soln is applied
front 15 why is quantification by color challenging? what can be done to overcome this challenge?	back 15 quantification by color measurement is challenging if variations captured in the sun, shade, or various lightings -> so images captured in a light box
front 16 question abt SD, LOQ, LOD	back 16 SD of blank samples, LOD determined to be 0.8 ppm and lower LOQ was estimated to be 2.4 ppm

front 17 advantages and disadvantages to visual interpretation	back 17 = makes it accesible visual interpretation: advantages - increases usability in low resource settings = capture data w/ cell phone = interpret electronically = preserve it empower monitoring agencies to track quality of salt in diff geographical areas over time disadvantages - human error in reading / recording results
front 18 diff matrixes used?	back 18 using diff water sources to test robustness of PAD
front 19 what was back titrated in the paper? What was the purpose?	back 19 iodate fortified salt w/ iodate in model system to carry out the analytical task of measuring iodine in salt redox titration excess iodide + iodate + acid = triiodide then titratef w/ thiosulfate using starch indicator if triiodate exceeds reducing capacity of thiosulfate, = indicator is blue (is clear before this) if smaller than amount of thiosulfate = indicator basically, I3 (triiodate) excess reacts with starch = BLUE COMPLEX amoxicillin saw procedure for quantification of beta-lactam antibiotics (ensure quality of pharmaceutical product) studied if paper test card analysis could be useful for quality testing in low resource settings where analytical chem labs are rare
front 20 results of back titration of amoxicillin	back 20 test card response showed good differentiation shows that cards could be used to detect antibiotics that contain 83% labeled API

front 21 analyte?	back 21 IODATE (IO3-)
front 22 matrix?	back 22 aqueous
front 23 is the method developed in the study quantitative or qualitative?	back 23 BOTH: QUANTITATIVE AND QUALITATIVE Qual - Color change Quant - Intensity of color using computer software
front 24 challenge of using PADs	back 24 reagents stored in paper substrate must be compatible + stable for long periods of time

front 25 what real world topic is the method developed aimed to address? / motivation for the method creation? / what they wanted to improve on?	back 25 to address analytical needs for salt producers salt usually fortified with potassium iodate many salt producers do not have access to a titration lab to assay the iodate this test card (PAD) is designed to carry out the entire analytical process
front 26 how does the indicator in the assay work?	back 26 IT IS A STARCH fortified salt w/ iodate in model system to carry out the analytical task of measuring iodine in salt redox titration excess iodide + iodate + acid = triiodide then titratef w/ thiosulfate using starch indicator if triiodate exceeds reducing capacity of thiosulfate, = indicator is blue if smaller than amount of thiosulfate = indicator basically, I3 (triiodate) excess reacts with starch = BLUE COMPLEX
front 27 what is the endpoint in the back titration and difference of PAD vs glassware titration	back 27 endpoint is when all S2O3 have reacted Pad: endpoint = BLUE before eq. point (not all S2O3 reacted) = uncolored glassware titration: endpoint = clear
front 28 can the assay be used for various other redox-active analytes?	back 28 YES the device is VERSATILE ex: quantified beta-lactam antibiotics via iodometric back titration

front 29 beta-lactam back titration	back 29 antibiotics quantified degraded in base -> redox active thiol -> acidified + known amount excess triiodide added to oxidize thiol unreacted triiodide is back titrated w/ thiosulfate
front 30 what is the STEM method used?	back 30 surface tension enabled mixing (STEM) the samples and reagents are confined to the reaction area by the solution meniscus and the wide wax barriers they are mixed by gently shaking liquid applied to rxn area - forms dome confined by the solution meniscus. Reagents stored in the 5 loading zones dissolve + mix
front 31 how is titration done on the test cards?	back 31 zones and each reaction area are loaded with different amounts of sodium thiosulfate, excess potassium iodide, tosic acid, and starch indicator can load up to 5 reagents on the card
front 32 where are the positive and negative controls?	back 32 they are designated reaction areas there are different reaction areas that act as positive or negative control

front 33 what is different about the card's end point vs a traditional titration?	back 33 traditional: has sharp end points card: no color unless the amount of iodate in solution overwhelms the amount of thiosulfate -> then iodate content in the reaction area cause inc color production from the indicator until the response is saturated
front 34 limit test	back 34 test to make sure iodine content is below allowed value for edible salt limit amount in salt for consumption is 15-30 ppm ish square 11 labeled ">30" on the test card changes color = sample is over iodized = more iodate than allowed
front 35 what is measured on the test card?	back 35 ppm I (iodine atoms/L solution) see how it is the analyte? ultimately measures 2 things colorimetric quantificatino assay (the titration) limit tests (determine if too much iodine for consumption)
front 36 diff parts of the card	back 36 negative control only acid/starch no response limit test for iodide quantify iodate in range of 0-4 ppm quantify iodate in range of 0-4 ppm quantify iodate in range of 0-4 ppm quantify in range of 3-7 ppm quantify in range of 3-7 ppm quantify in range of 3-7 ppm 7-11 ppm 11-15 ppm limit test for iodate in conc. greater than 30 ppm I positive control

front 37 why was a lightbox used	back 37 bc quantification by color measurement is challenging if there are variations of images captured in the sun, shade, etc light box has consistent illumination
front 38 blue color measured by what?	back 38 computer image analysis
front 39 what did the results of computer image analysis of the blue color on the test cards show?	back 39 sigmoidal increase in color with increasing iodate concentration
front 40 how many measurements were taken?	back 40 triplicate measurements taken to contribute to precision

front 41 more sensitive = bigger slope	back 41 no data
front 42 systematic error	back 42 camera software - adjusts exposure/coloration of image = lowers apparent iodine concentration manual exposure could avoid this issue systematic underestimation of iodine concentration at high iodine concentrations - main source of inaccuracy
front 43 computer reading of cards advantages/disadvantages	back 43 visual analysis inc usability in low resource settings using phone camera allows easy data collection + have in centralized network = more accessible con visual analysis introduce human error in read/record results
front 44 how do different water sources and storage affect response? tap w/ high mineral water 8% error lake water 17% error	back 44 no data

front 45 current methods for measurement of iodine in salt as well as their pros/cons (why theyre good but also why they are not ideal for the conditions being addressed (address an analytical need of salt producers in the developing world, no access to a titration lab to perform the iodometric titrations)	back 45 glassware titration good precision/accuracy if done in lab + professionally in field conditions in dev world settings -> accuracy/precision are compromised by impure reagents lack of calibration/service for analytical balances overconcentrated titrant rapid test kits (RTKs) inexpensive but external validation study by WHO showed that tests are not reliable spectroscopic test kits good metrics but limited quantification range but require purchase of specialized reader + kits of the chemicals used saltPAD not most accuracy (middle), and least precise of the options, BUT is cheapest (for sure) and technical expertise needed is low sacrifices accuracy and precision for the sake of low cost and expertise needed, making it a good choice for settings with low ability to obtain and run the other methods discussed
front 46 why is back titration of amoxicillin done?	back 46 Wanted to address whether the paper test card developed could be useful in quality testing in low resource areas (useful for testing besides the iodate assay it was developed for) to ensure antibiotic quality places of low resources have substandard antibiotics + need to be checked for quality
front 47 ppm solution and salt and must convert to iodate	back 47 ppm I = mg iodine atoms / L solution Must convert to iodate first Mg iodine mg/kg salt Salt water soln – mg/L
front 48 How do LOD and LOQ used compare to the ones we used in class?	back 48 LOD = 0.8 ppm I, defined by 3SD/m LLOQ = what we call the limit of quantification they call it lower limit of quantification defined same as us, as 10SD/m 2.4 ppm I

front 49 eq 1 is about what?	back 49 precision calculated btw the 2 interpreters (x1 and x2)
front 50 eq2 is about what?	back 50 calc accuracy (real vs measured)
front 51 what is robustness and how did it play into the study?	back 51 if something is robust it means that external stimuli will not easily affect it. that is why the experimenters put the PAD in extreme conditions and show that it still works. I think this is also important in low resource settings as the storing conditions for the PADs might not be optimal. aging in convection oven lake wager vs hard water
front 52 why are they trying to find the analyte? (iodate)	back 52 bc they add it to fortify salts, and want to measure it in salts

front 53 why is the assay being made?	back 53 because they wanted to establish an assay that can be used in low resource areas, that can be done without chemistry equipment, electricity, etc. Iodate and beta-lactam are model systems, and they are trying to detect tests that can test various analytes in low resource areas
front 54 PAD	back 54 paper analytic device device developed
front 55 ASSURED	back 55 ASSURED (affordable, sensitive, specific, user friendly, rapid and robust, equipment free, deliverable to the end user) criteria to assess devices meant for use in low resource settings considered in design reasons how/why: complete process = 0.09$ + $.5 labor + could be decreased paper test card performs iodine analysis w/ accuracy + precision that rivals other technology used in salt fortification plants in the developing world + can perform iodometric back titration w/ to detect substandard antibiotics sufficient accuracy takes 5 mins test cards can withstand a lot of conditions test cards can be analyzed using computer image processing of mobile phone photographs -> mobile phone network for data collection + archiving
front 56 why iodate?	back 56 dont give good reason, just chose as model system to detect an analyte did same w/ beta lactam just trying to create a test for low resource areas

front 57 how the assay works	back 57 separate into quadrants so reagents dont react - separate sample in the middle
front 58 reaction steps	back 58 1. cs iodide (I-), dont know how much iodate (IO3-) so flood so it runs out = I3- excess I- in soln 2. titrate I3- with S2o3- 3. starch added
front 59 their spiking vs ours	back 59 their spiking is ??? ours is adding a known concentration of the analyte (spike), to an unknown concentration analyte in a sample, and determining the original unknown from the response (signal, intensity, etc)
front 60 the titrant is	back 60 I3- (triiodide)

front 61

pH meter

back 61

as ionic strength increases, the H+ is inhibited from reaching the pH meter and pH reads higher than it really is