Rexcell Tissue & Airlaid AB is a producer of paper products such as coloured tissue, where it is important to manufacture a product that does not release any colour during usage. To prevent colour bleeding, a fixative is added during the paper dyeing process. However, excessive fixative can cause issues to the papermaking process due to its charge. Currently, charge measurements on the water flow are used to detect fixative overdose, but a more precise method is desired. This study explores using FTIR spectroscopy and existing charge measurements (PCD and Z-potential) to analyse process water for different dye types (Red, Black, Green). The ATR-FTIR technique shows that fixative is detectable only at higher concentrations than present in the water. By reducing the process water to measurable fixative levels, concentration determination is possible using IR peaks associated with the amine bond. Comparing concentration values with charge values, a good agreement is observed for two dye types, but the green whitewater shows discrepancies. This could be due to the charged dye molecules influencing the fixative spectrum, affecting concentration determination. The study suggests using an ATR crystal allowing multiple reflections to enhance the fixative signal for accurate concentration measurement. Further investigation is needed to understand the impact of coloured molecules on fixative properties and the FTIR spectrum. In summary, it is feasible to determine fixative concentration in whitewater using FTIR-ATR, but refining the methodology is essential for reliable results

Inom klinisk patologi bedöms vävnadsprover under mikroskop, med syftet att fastställa diagnos. Utgångsmaterial är antingen ett helt organ eller en liten bit från det sjukligt förändrade organet. I det senare fallet kallas preparatet för biopsi och dessa tas med hjälp av biopsiverktyg och oftast under ultraljudledning. Njurbiopsier kan tas vid misstänkt transplantatavstötning, av medicinska skäl, vid inflammatoriska tillstånd (nefriter) samt nefrotiska tillstånd. En del av biopsimaterialet fixeras i 4 % formaldehyd för ljusmikroskopisk (LM) bedömning, medan resten transporteras i transportlösningar som Michels- eller Zeus lösning. Det materialet fryses ned direkt för kryostatsnittning, dessa transportlösningar syftar till att bevara vävnaden färsk för immunofluorescens (IF) analys. Problem kan uppstå när materialet som bedöms med LM inte innehåller ett acceptabelt antal glomeruli, där minst 12- 15 stycken krävs för att biopsin skall vara representativ. Om det är alltför få till antalet brukar man tina och formaldehydfixera IF materialet. Morfologin blir oftast dålig och inte lämplig för bedömning. Den enda som man kan göra är att ombiopsera patienten. Detta är kostsamt, obekvämt för patienten och inte helt riskfritt. Syftet med den här studien var att undersöka ifall man kan ersätta transportlösningarna med ett fixativ som skulle medföra bättre morfologi i de fall som IF materialet måste tinas upp och användas för LM, men samtidigt erbjuda samma kvalitet på IF-signalen. Tre fixeringsmedel jämfördes med rutinmetodens 4 % formaldehyd; dels kommersiellt tillgängliga som Histochoice och HOPE (Hepes-Glutamic acid buffer mediated Organic solvent Protection Effect) och ett fixativ som är baserat på zinkjoner. Resultatet visade att när det gäller LM-undersökning på paraffininbäddat material så gav HOPE och Histochoice acceptabel morfologi av glomeruli. Vid upptinande av materialet följt av formaldehyd/paraffin, sågs fortsatt god kvalitet i den glomerulära morfologin, medan den tubulära morfologin var klart undermålig. Zn-fixering ledde till bubblor i cytoplasman vilket inte är acceptabel morfologi. I IF-analys gav alla fixativ negativ signal utom Zn-fixering, vilken gav en positiv signal. Det innebär att ingen säker diagnos kan ställas vid användning av de undersökta fixeringsmedlen som kan ersätta transportlösningar eller rutinlaboratoriet formaldehyd. Zn-fixativ såg lovande ut om det bortses från bubblorna, men detta behöver undersökas ytterligare i framtida studier / lt is important for clinical pathology to assess tissue samples (preparations) under the microscope to make a diagnosis. Starting materials is either a whole organ, or a small piece of the diseased body. The material can also be in the form of so-called biopsies, which are taken by biopsytools and ultrasound. Kidney biopsy may be taken for suspected transplant rejection, medical reasons and at nephritic (inflammation), and nephrotic states. Half of the material from kidney biopsies are transported in transport solutions of the type Michel / Zeus that serves the purpose of preserving the tissue fresh for immunofluorescence (IF) analysis. The other half is fixed in 4% formaldehyde for light microscope (LM) assessment, a procedure that precludes IF staining due to destruction of the antigenicity of the tissues. Problems might occur when the material is assessed by LM and do not contain an acceptable number of glomeruli, at least 12-15 are regarded as acceptable for diagnosis. If these are fewer in numbers, the material previously used for IF may be thawed and formaldehyde fixed. The morphology is however often adversely affected by this procedure, rendering the tissue unsuitable for morphological assessment. Therefore the only remaining option is to re-biopsy patients. This is costly, inconvenient for the parients, and not completely safe. This study was performed in order to explore if transport solutions can be replaced by a fixative that would result in a better morphology after thawing of the tissues, but with retained IF -quality. Three fixing agents were compared with routine method 4% formaldehyde; the commercially available Histochoice and HOPE fixatives (Hepes-Glutamic acid buffer mediated Organic solvent Protection Effect) and a fixative that was based on zinc ions. The results showed that in terms of LM, the fixatives HOPE and Histochoice gave acceptable morphology of the glomeruli, while the tubules were poor. It also showed that there were a lot of bubbles in the cytoplasm at the Zn-fixing. As for IF-analysis, all were negative except Zn that gave a positive signal. This means that no secure diagnosis can replace the routine transport formaldehyde. Zn fixative looked promising, except the bubbles, but needs to be further investigated in future studies.