The presented work proposes an approach based on proteomic techniques to identify proteins in egg white. Response surface methodology (RSM) with Box–Behnken design (BBD) was used to optimize the ultrasound-assisted extraction process of proteins from the egg white. The effects of extraction parameters, including trifluoroacetic acid (TFA) concentration, ultrasonic power and ultrasonic time on the extraction process of proteins were evaluated. The optimized extraction parameters were trifluoroacetic acid (TFA) concentration, 0.53% (v/v); ultrasonic power, 50% and ultrasonic time, 40 min. The effects of three factors (trypsin volume, pH of tryptic digestion and incubation time) on the tryptic digestion process of extracted proteins were investigated. The results showed that the optimized tryptic digestion conditions were as follows: volume of 10 μg mL−1 trypsin, 8 μL; pH, 7.0 and incubation time, 16 h. Under the optimized conditions, the peptide mixture was analysed using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The methodology was successfully applied to free-range and barn-raised chicken egg white for protein identification. The results showed that 23 proteins and 29 proteins were identified in free-range chicken and barn-raised chicken egg white, respectively. Among them, the collagen peptides were found in egg white for the first time.

A proteinaceous binding media for the polychrome terracotta army of Emperor Qin Shihuang has been identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Methods for the preparation of the model samples and the elimination of interferences have been evaluated, as well as ageing processes. A method involving the complexation of EDTA in combination with dialysis was used to eliminate any interference in the polychrome layers taken from the historical samples. The model samples were aged by being buried in loess to replicate the ageing process of the historical samples as closely as possible. The optimum conditions for the extraction and subsequent enzymatic hydrolysis of the extracted protein were investigated. Under the optimized conditions, the “peptide mass fingerprints” of the proteinaceous binding media from the historical and model samples were determined by MALDI-TOF-MS. The results revealed that animal glue was used as the binding media for the polychrome layers of Emperor Qin Shihuang’s terracotta army. It also shows that animal glue used as binding media has a long history in China.

The proteinaceous binding media used in Tang Dynasty polychrome pottery was determined using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The optimum conditions for the extraction and subsequent enzymatic hydrolysis of the protein sample were established, and applied to the pretreatment of model and historical samples. Complexation of EDTA in combination with dialysis was determined to be the most effective method for eliminating interferences in polychrome layers taken from historical samples. Model samples were aged by burial in loess so as to more closely replicate the ageing process of the historical samples. Using the aforementioned optimized conditions, the “peptide mass fingerprint” of the binding media of historical and model samples was determined by MALDI-TOF-MS. Comparisons between the “peptide mass fingerprint” obtained for the historical sample and those of the model samples proved that animal glue was used as the binding media for the Tang Dynasty polychrome pottery. It also shows that animal glue used as binding media enjoys a long history in China.

A simple and rapid method for the determination of orthophosphate was developed in this study. The method is based on a reagent-immobilized poly(vinyl alcohol) (PVA) film which is prepared by temporary immobilization of sensitive reagents on the glass slide. The preparation conditions of the film were investigated in detail. Under the optimum conditions, the absorbance is linearly proportional to the concentration of phosphorus from 0.65 to 8.1 μmol L−1 and the limit of detection is 0.5 μmol L−1 of phosphorus. The relative standard deviation is 2.9% (n = 10). The proposed method has been effectively used for the determination of orthophosphate in various water samples.

The analysis of phenylalanine (Phe) in serum is widely performed for the screening of newborn phenylketonuria (PKU). In this work, a novel spectrofluorimetric method for the determination of Phe was developed based on the fluorescence enhancement of Ruhemann's purple, the reaction product between Phe and ninhydrin, upon coordination with Eu3+. A filter paper disc containing immobilized reactants (ninhydrin and Eu3+) was fabricated by sol–gel method. The experimental parameters affecting the determination of Phe, such as the concentrations of immobilized reagents, the pH value, the reaction time and temperature were optimized. Under optimum conditions, the fluorescence intensity of Phe–ninhydrin–Eu3+ system was linearly proportional to the concentration of Phe in the range from 5 × 10−5 to 2 × 10−3 mol L−1, and the limit of detection was found to be 5.2 × 10−6 mol L−1. The relative standard deviation was 2.6% for ten replicate measurements of 1.5 × 10−4 mol L−1 of Phe. The method has merits of sensitivity, simplicity and low cost, and has been applied to the determination of Phe in artificial serum.Graphical abstractHighlights► A simple, low-cost and environmentally friendly determination for phenylalanine is developed. ► Filter paper-based optical sensor is fabricated by immobilizing reactants with sol–gel technology. ► The fluorescence of RP (the reaction product between phenylalanine and ninhydrin) is remarkably enhanced upon binding to Eu3+. ► The method has great potential to be used as an alternative for the diagnosis of newborn phenylketonuria.

A simple and rapid method for the determination of orthophosphate was developed in this study. The method is based on a reagent-immobilized poly(vinyl alcohol) (PVA) film which is prepared by temporary immobilization of sensitive reagents on the glass slide. The preparation conditions of the film were investigated in detail. Under the optimum conditions, the absorbance is linearly proportional to the concentration of phosphorus from 0.65 to 8.1 μmol L−1 and the limit of detection is 0.5 μmol L−1 of phosphorus. The relative standard deviation is 2.9% (n = 10). The proposed method has been effectively used for the determination of orthophosphate in various water samples.