Handheld device with a disposable element for chemical analysis of multiple analytes

A method for measuring analyte concentration of a chemical or a biological substance, said method comprising the steps of:

• a. providing a reagent film with at least one internal reference standard;
• b. immobilizing a layer of said film onto a test element, thereby providing a film coated test element;
• c. emitting light energy onto a coated test element, wherein said light energy undergoes internal reflection and multiangle scattering inside said test element, said light energy being effective to stimulate a dual reference light response from said coated test element;
• d. exposing said coated test element to a sample substance for a specified time period, then removing said exposed test element from said substance, thereby providing a sample test element;
• e. emitting light energy onto said sample test element, said light energy being effective to stimulate a dual sample light response from said sample test element;
• f. collecting and processing said reference and sample light response data to calculate a light absorption response;
• g. utilizing said light absorption response to detect and quantify analyte concentration in said substance;
• and
• h. generating a signal indicative of said analyte concentration based on said detection and quantification.