The present disclosure provides a color chart and a test kit for estimating chemical oxygen demand of water. The color chart includes a blue component, an indigo component, an umber component, and an orange component. The test kit includes an oxidant, a reductant, an indicator, and the color chart. The present disclosure also provides a method for estimating chemical oxygen demand of water. The method includes providing a water sample; adding an oxidant to the water sample; heating the water sample; adding a reductant to the water sample; adding an indicator to the water sample, such that the water sample develops a color; and matching the color of the water sample with the color components of the color chart to estimate the chemical oxygen demand of the water sample.

The present invention is directed to a method for the determination of the hyaluronic acid content of a hydrogel, the method comprising the following steps: a) preparing, as reagent A, a solution of sodium tetraborate in sulfuric acid; b) preparing reagent B by dissolving carbazole in ethanol; c) preparing test solutions by dissolving the hydrogel in an aqueous solution; d) treating the test solution with ultrasounds for a period of time sufficient to obtain a macroscopically homogeneous solution; e) preparing a reference stock solution by dissolving glucuronic acid, or a glucuronic acid-containing substance in an aqueous solution; f) preparing at least 3 reference solutions by dilution of the reference stock solution in aqueous solution, preferably at concentration comprised between 0.0005% w/v and 0.0100% w/v, preferably between 0.0010% w/v and 0.0050% w/v; g) preparing the test tubes by admixing reagent A, reagent B and one of the following: reference solution, test solution, aqueous solution (blank), and optionally solution for interference (crosslinker sample or additive sample); placing each test tube on a water bath for at least 5 min, then cool them to room temperature; h) reading the absorbance at a wavelength comprised between 500 and 580 nm, preferably at about 530 nm, against the blank and optionally the sample for interference.

The present invention is directed to a method for the determination of the hyaluronic acid content of a hydrogel, the method comprising the following steps: a) preparing, as reagent A, a solution of sodium tetraborate in sulfuric acid; b) preparing reagent B by dissolving carbazole in ethanol; c) preparing test solutions by dissolving the hydrogel in an aqueous solution; d) treating the test solution with ultrasounds for a period of time sufficient to obtain a macroscopically homogeneous solution; e) preparing a reference stock solution by dissolving glucuronic acid, or a glucuronic acid-containing substance in an aqueous solution; f) preparing at least 3 reference solutions by dilution of the reference stock solution in aqueous solution, preferably at concentration comprised between 0.0005% w/v and 0.0100% w/v, preferably between 0.0010% w/v and 0.0050% w/v; g) preparing the test tubes by admixing reagent A, reagent B and one of the following: reference solution, test solution, aqueous solution (blank), and optionally solution for interference (crosslinker sample or additive sample); placing each test tube on a water bath for at least 5 min, then cool them to room temperature; h) reading the absorbance at a wavelength comprised between 500 and 580 nm, preferably at about 530 nm, against the blank and optionally the sample for interference.

An embodiment provides a method for measuring nitrate in an aqueous sample, including: introducing an aqueous sample containing an amount of nitrate to a cation exchange resin; flowing the aqueous sample over copper metal; adding a reducing reagent to the aqueous sample; adding a colorimetric indicator to the aqueous sample; and measuring the amount of nitrate in the aqueous sample by measuring a change in intensity of the absorbance. Other aspects are described and claimed.

A method for determining a phosphate concentration in a water sample includes providing the water sample, adding a first acid to the water sample to obtain a second water sample in which a concentration of the first acid is at least 0.5 wt.-%, performing a first photometric measurement of the second water sample, adding a coloring component to the second water sample to obtain a third water sample, performing a second photometric measurement of the third water sample, and calculating the phosphate concentration from a difference between the first photometric measurement and the second photometric measurement.

A method for determining a phosphate concentration in a water sample includes providing the water sample, adding a first acid to the water sample to obtain a second water sample in which a concentration of the first acid is at least 0.5 wt.-%, performing a first photometric measurement of the second water sample, adding a coloring component to the second water sample to obtain a third water sample, performing a second photometric measurement of the third water sample, and calculating the phosphate concentration from a difference between the first photometric measurement and the second photometric measurement.

A visual indicating paste composition is provided which is capable of producing a detectable color change upon contact with an aqueous liquid. The paste composition includes: an indicator dye capable of changing color in the pH range between about 3 and about 11; an inorganic base capable of being converted to a more basic substance upon reaction with water; a liquid carrier (such as a polyalkylene glycol carrier); optionally, a gelling agent such as silica gel; and a proton donating compound such as a carboxylic acid or organosulfonic acid. When applied to a measuring probe, the paste composition is particularly adapted for detecting the water level in the bottom of tanks and delivery systems containing a fuel such as gasoline by producing a clear detectable color change without bleeding or run-off upon contact with an aqueous liquid. The paste composition exhibits long shelf life and improved water tolerance.

Methods and systems for tracking a cassette containing one or more instruments in an instrument reprocessing are provided. A method for tracking an cassette housing one or more instruments in an instrument reprocessing, comprising: sterilizing, at a sterilizer, the cassette; receiving, at a server, a chemical indicator identification encrypted by a private key after the cassette is sterilized; decrypting, at the server, the chemical indicator identification with a corresponding public key; and in response to decryption of the chemical indicator identification, authenticating, at the server, the chemical indicator identification.

A method for detecting labile zinc (Zn.sup.2+) in a biological material is provided herein, the method including: (a) contacting the biological material with a composition including NapBu-BPEA; and (b) imaging the biological material via molecular fluorescence imaging to detect the labile zinc in the biological material. Also provided herein are methods for morphology-correlated detection of labile zinc localization in a subcellular organelle of a living cell and methods for tracking a change in labile zinc localization in a biological material.

A method for the detection of hydrocarbon contamination in a sample is disclosed. The method includes contacting a sample with a molecular probe. The molecular probe has a photoluminescence which is environmentally sensitive. The photoluminescence from the molecular probe is collected. The method includes determining whether the photoluminescence is indicative of a hydrocarbon contaminated sample. A test strip for the detection of hydrocarbon contamination in a sample is also disclosed. The test strip includes a molecular probe embedded in a substrate and/or immobilized to the substrate, the molecular probe having a photoluminescence which is environmentally sensitive to hydrocarbon contaminated sample.